text: Vaccines http://www.mdpi.com/journal/vaccines Latest open access articles published in Vaccines at http://www.mdpi.com/journal/vaccines http://www.mdpi.com/2076-393X/3/4/829 Respiratory syncytial virus (RSV) is the single most important cause of serious lower respiratory tract infections in young children; however no effective treatment or vaccine is currently available. Previous studies have shown that therapeutic treatment with a monoclonal antibody (clone 131-2G) specific to the RSV G glycoprotein CX3C motif, mediates virus clearance and decreases leukocyte trafficking to the lungs of RSV-infected mice. In this study, we show that vaccination with layer-by-layer nanoparticles (LbL-NP) carrying the G protein CX3C motif induces blocking antibodies that prevent the interaction of the RSV G protein with the fractalkine receptor (CX3CR1) and protect mice against RSV replication and disease pathogenesis. Peptides with mutations in the CX3C motif induced antibodies with diminished capacity to block G protein-CX3CR1 binding. Passive transfer of these anti-G protein antibodies to mice infected with RSV improved virus clearance and decreased immune cell trafficking to the lungs. These data suggest that vaccination with LbL-NP loaded with the CX3C motif of the RSV G protein can prevent manifestations of RSV disease by preventing the interaction between the G protein and CX3CR1 and recruitment of immune cells to the airways. Vaccines 2015-10-12 3 4 Article 10.3390/vaccines3040829 829 849 2076-393X 2015-10-12 doi: 10.3390/vaccines3040829 Patricia Jorquera Katie Oakley Thomas Powell Naveen Palath James Boyd Ralph Tripp http://www.mdpi.com/2076-393X/3/4/814 Nanoparticles have demonstrated unique advantages in enhancing immunotherapy potency and have drawn increasing interest in developing safe and effective vaccine formulations. Recent technological advancement has led to the discovery and development of cell membrane-coated nanoparticles, which combine the rich functionalities of cellular membranes and the engineering flexibility of synthetic nanomaterials. This new class of biomimetic nanoparticles has inspired novel vaccine design strategies with strong potential for modulating antibacterial immunity. This article will review recent progress on using cell membrane-coated nanoparticles for antibacterial vaccination. Specifically, two major development strategies will be discussed, namely (i) vaccination against virulence factors through bacterial toxin sequestration; and (ii) vaccination against pathogens through mimicking bacterial antigen presentation. Vaccines 2015-10-06 3 4 Review 10.3390/vaccines3040814 814 828 2076-393X 2015-10-06 doi: 10.3390/vaccines3040814 Pavimol Angsantikul Soracha Thamphiwatana Weiwei Gao Liangfang Zhang http://www.mdpi.com/2076-393X/3/4/803 In the development of subunit vaccines with purified or recombinant antigens for cancer and infectious diseases, the design of improved and safe adjuvants able to efficiently target the antigen presenting cells, such as dendritic cells, represents a crucial challenge. Nanoparticle-based antigen delivery systems have been identified as an innovative strategy to improve the efficacy of subunit vaccines. Among them, self-assembled micellar nanoparticles from amphiphilic (macro)molecules have recently emerged as promising candidates. In this short review, we report on the recent research findings highlighting the versatility and potential of such systems in vaccine delivery. Vaccines 2015-09-25 3 4 Review 10.3390/vaccines3040803 803 813 2076-393X 2015-09-25 doi: 10.3390/vaccines3040803 Thomas Trimaille Bernard Verrier http://www.mdpi.com/2076-393X/3/3/771 Transcription is a dynamic process influenced by the cellular environment: healthy, transformed, and otherwise. Genome-wide mRNA expression profiles reflect the collective impact of pathways modulating cell function under different conditions. In this review we focus on the transcriptional pathways that control tumor infiltrating CD8+ T cell (TIL) function. Simultaneous restraint of overlapping inhibitory pathways may confer TIL resistance to multiple mechanisms of suppression traditionally referred to as exhaustion, tolerance, or anergy. Although decades of work have laid a solid foundation of altered transcriptional networks underlying various subsets of hypofunctional or "dysfunctional" CD8+ T cells, an understanding of the relevance in TIL has just begun. With recent technological advances, it is now feasible to further elucidate and utilize these pathways in immunotherapy platforms that seek to increase TIL function. Vaccines 2015-09-17 3 3 Review 10.3390/vaccines3030771 771 802 2076-393X 2015-09-17 doi: 10.3390/vaccines3030771 Katherine Waugh Sonia Leach Jill Slansky http://www.mdpi.com/2076-393X/3/3/751 Evolution of Bordetella pertussis is driven by natural and vaccine pressures. Isolates circulating in regions with high vaccination coverage present multiple allelic and antigenic variations as compared to isolates collected before introduction of vaccination. Furthermore, during the last epidemics reported in regions using pertussis acellular vaccines, isolates deficient for vaccine antigens, such as pertactin (PRN), were reported to reach high proportions of circulating isolates. More sporadic filamentous hemagglutinin (FHA) or pertussis toxin (PT) deficient isolates were also collected. The whole genome of some recent French isolates, deficient or non-deficient in vaccine antigens, were analyzed. Transcription profiles of the expression of the main virulence factors were also compared. The invasive phenotype in an in vitro human tracheal epithelial (HTE) cell model of infection was evaluated. Our genomic analysis focused on SNPs related to virulence genes known to be more likely to present allelic polymorphism. Transcriptomic data indicated that isolates circulating since the introduction of pertussis vaccines present lower transcription levels of the main virulence genes than the isolates of the pre-vaccine era. Furthermore, isolates not producing FHA present significantly higher expression levels of the entire set of genes tested. Finally, we observed that recent isolates are more invasive in HTE cells when compared to the reference strain, but no multiplication occurs within cells. Vaccines 2015-09-14 3 3 Article 10.3390/vaccines3030751 751 770 2076-393X 2015-09-14 doi: 10.3390/vaccines3030751 Valérie Bouchez Nicolas Hegerle Francesco Strati Elisabeth Njamkepo Nicole Guiso http://www.mdpi.com/2076-393X/3/3/730 The safety and precision of peptide antigens has prompted the search for adjuvants capable of increasing the immune response against these intrinsically poorly immunogenic antigens. The integration of both immunostimulants and peptide antigens within nanometric delivery systems for their co-delivery to immune cells is a promising vaccination strategy. With this in mind, the potential synergistic effect of the immunostimulant poly (I:C) (pIC) and a T-Helper peptide (PADRE), integrated into a chitosan (CS) based nanostructure, was explored. The value of this nanostructured combination of materials was assessed for a peptide antigen (1338aa) derived from the HPV-16 L2 protein. These nanoparticles, produced by ionic gelation technique, exhibited a nanometric size (<300 nm), a high positive surface charge (>40 mV) and high pIC association efficiency (>96%). They also showed capacity for the association of both the 1338aa and PADRE peptides. The influence of the presence of pIC and PADRE in the nanocomposition, as well as that of the peptide presentation form (encapsulated versus surface adsorbed) on the antibody induction was evaluated in a preliminary in vivo study. The data obtained highlights the possibility to engineer nanoparticles through the rational combination of a number of adjuvant molecules together with the antigen. Vaccines 2015-09-11 3 3 Article 10.3390/vaccines3030730 730 750 2076-393X 2015-09-11 doi: 10.3390/vaccines3030730 Jorge Correia-Pinto Noemi Csaba John Schiller Maria Alonso http://www.mdpi.com/2076-393X/3/3/703 Indoleamine 2, 3-dioxygenase (IDO) is the first and rate limiting catabolic enzyme in the degradation pathway of the essential amino acid tryptophan. By cleaving the aromatic indole ring of tryptophan, IDO initiates the production of a variety of tryptophan degradation products called "kynurenines" that are known to exert important immuno-regulatory functions. Because tryptophan must be supplied in the diet, regulation of tryptophan catabolism may exert profound effects by activating or inhibiting metabolism and immune responses. Important for survival, the regulation of IDO biosynthesis and its activity in cells of the immune system can critically alter their responses to immunological insults, such as infection, autoimmunity and cancer. In this review, we assess how IDO-mediated catabolism of tryptophan can modulate the immune system to arrest inflammation, suppress immunity to cancer and inhibit allergy, autoimmunity and the rejection of transplanted tissues. Finally, we examine how vaccines may enhance immune suppression of autoimmunity through the upregulation of IDO biosynthesis in human dendritic cells. Vaccines 2015-09-10 3 3 Review 10.3390/vaccines3030703 703 729 2076-393X 2015-09-10 doi: 10.3390/vaccines3030703 Jacques Mbongue Dequina Nicholas Timothy Torrez Nan-Sun Kim Anthony Firek William Langridge http://www.mdpi.com/2076-393X/3/3/686 Microorganisms like the halophilic archaeon Halobacterium sp. NRC-1 produce gas-filled buoyant organelles, which are easily purified as protein nanoparticles (called gas vesicles or GVNPs). GVNPs are non-toxic, exceptionally stable, bioengineerable, and self-adjuvanting. A large gene cluster encoding more than a dozen proteins has been implicated in their biogenesis. One protein, GvpC, found on the exterior surface of the nanoparticles, can accommodate insertions near the C-terminal region and results in GVNPs displaying the inserted sequences on the surface of the nanoparticles. Here, we review the current state of knowledge on GVNP structure and biogenesis as well as available studies on immunogenicity of pathogenic viral, bacterial, and eukaryotic proteins and peptides displayed on the nanoparticles. Recent improvements in genetic tools for bioengineering of GVNPs are discussed, along with future opportunities and challenges for development of vaccines and other applications. Vaccines 2015-09-07 3 3 Review 10.3390/vaccines3030686 686 702 2076-393X 2015-09-07 doi: 10.3390/vaccines3030686 Shiladitya DasSarma Priya DasSarma http://www.mdpi.com/2076-393X/3/3/662 Recent studies have demonstrated great therapeutic potential of educating and unleashing our own immune system for cancer treatment. However, there are still major challenges in cancer immunotherapy, including poor immunogenicity of cancer vaccines, off-target side effects of immunotherapeutics, as well as suboptimal outcomes of adoptive T cell transfer-based therapies. Nanomaterials with defined physico-biochemical properties are versatile drug delivery platforms that may address these key technical challenges facing cancer vaccines and immunotherapy. Nanoparticle systems have been shown to improve targeted delivery of tumor antigens and therapeutics against immune checkpoint molecules, amplify immune activation via the use of new stimuli-responsive or immunostimulatory materials, and augment the efficacy of adoptive cell therapies. Here, we review the current state-of-the-art in nanoparticle-based strategies designed to potentiate cancer immunotherapies, including cancer vaccines with subunit antigens (e.g., oncoproteins, mutated neo-antigens, DNA and mRNA antigens) and whole-cell tumor antigens, dendritic cell-based vaccines, artificial antigen-presenting cells, and immunotherapeutics based on immunogenic cell death, immune checkpoint blockade, and adoptive T-cell therapy. Vaccines 2015-08-27 3 3 Review 10.3390/vaccines3030662 662 685 2076-393X 2015-08-27 doi: 10.3390/vaccines3030662 Yuchen Fan James Moon http://www.mdpi.com/2076-393X/3/3/638 Despite the discovery of many potential antigens for subunit vaccines, universal protection is often lacking due to the limitations of conventional delivery methods. Subunit vaccines primarily induce antibody-mediated humoral responses, whereas potent antigen-specific cellular responses are required for prevention against some pathogenic infections. Nanoparticles have been utilised in nanomedicine and are promising candidates for vaccine or drug delivery. Nanoparticle vehicles have been demonstrated to be efficiently taken up by dendritic cells and induce humoral and cellular responses. This review provides an overview of nanoparticle vaccine development; in particular, the preparation of nanoparticles using a templating technique is highlighted, which would alleviate some of the disadvantages of existing nanoparticles. We will also explore the cellular fate of nanoparticle vaccines. Nanoparticle-based antigen delivery systems have the potential to develop new generation vaccines against currently unpreventable infectious diseases. Vaccines 2015-08-10 3 3 Article 10.3390/vaccines3030638 638 661 2076-393X 2015-08-10 doi: 10.3390/vaccines3030638 Aya Taki Peter Smooker http://www.mdpi.com/2076-393X/3/3/620 Vaccines are considered one of the greatest medical achievements in the battle against infectious diseases. However, the intractability of various diseases such as hepatitis C, HIV/AIDS, malaria, tuberculosis, and cancer poses persistent hurdles given that traditional vaccine-development methods have proven to be ineffective; as such, these challenges have driven the emergence of novel vaccine design approaches. In this regard, much effort has been put into the development of new safe adjuvants and vaccine platforms. Of particular interest, the utilization of plant virus-like nanoparticles and recombinant plant viruses has gained increasing significance as an effective tool in the development of novel vaccines against infectious diseases and cancer. The present review summarizes recent advances in the use of plant viruses as nanoparticle-based vaccines and adjuvants and their mechanism of action. Harnessing plant-virus immunogenic properties will enable the design of novel, safe, and efficacious prophylactic and therapeutic vaccines against disease. Vaccines 2015-08-05 3 3 Review 10.3390/vaccines3030620 620 637 2076-393X 2015-08-05 doi: 10.3390/vaccines3030620 Marie-Ève Lebel Karine Chartrand Denis Leclerc Alain Lamarre http://www.mdpi.com/2076-393X/3/3/597 The significant contribution of host immunity in early tumorigenesis has been recently recognized as a result of our better understanding of the molecular pathways regulating tumor cell biology and tumor-lymphocyte interactions. Emerging evidence suggests that disseminated dormant tumor cells derived from primary tumors before or after immune surveillance, are responsible for subsequent metastases. Recent trends from the field of onco-immunology suggest that efficiently stimulating endogenous anticancer immunity is a prerequisite for the successful outcome of conventional cancer therapies. Harnessing the immune system to achieve clinical efficacy is realistic in the context of conventional therapies resulting in immunogenic cell death and/or immunostimulatory side effects. Targeted therapies designed to target oncogenic pathways in tumor cells can also positively regulate the endogenous immune response and tumor microenvironment. Identification of T cell inhibitory signals has prompted the development of immune checkpoint inhibitors, which specifically hinder immune effector inhibition, reinvigorating and potentially expanding the preexisting anticancer immune response. This anticancer immunity can be amplified in the setting of immunotherapies, mostly in the form of vaccines, which boost naturally occurring T cell clones specifically recognizing tumor antigens. Thus, a promising anticancer therapy will aim to activate patients' naturally occurring anticancer immunity either to eliminate residual tumor cells or to prolong dormancy in disseminated tumor cells. Such an endogenous anticancer immunity plays a significant role for controlling the balance between dormant tumor cells and tumor escape, and restraining metastases. In this review, we mean to suggest that anticancer therapies aiming to stimulate the endogenous antitumor responses provide the concept of the therapeutic management of cancer. Vaccines 2015-07-30 3 3 Review 10.3390/vaccines3030597 597 619 2076-393X 2015-07-30 doi: 10.3390/vaccines3030597 Constantin Baxevanis Sonia Perez http://www.mdpi.com/2076-393X/3/3/579 Cholera toxin subunit B (CTB) is the nontoxic portion of cholera toxin. Its affinity to the monosialotetrahexosylganglioside (GM1) that is broadly distributed in a variety of cell types including epithelial cells of the gut and antigen presenting cells, macrophages, dendritic cells, and B cells, allows its optimal access to the immune system. CTB can easily be expressed on its own in a variety of organisms, and several approaches can be used to couple it to antigens, either by genetic fusion or by chemical manipulation, leading to strongly enhanced immune responses to the antigens. In autoimmune diseases, CTB has the capacity to evoke regulatory responses and to thereby dampen autoimmune responses, in several but not all animal models. It remains to be seen whether the latter approach translates to success in the clinic, however, the versatility of CTB to manipulate immune responses in either direction makes this protein a promising adjuvant for vaccine development. Vaccines 2015-07-24 3 3 Review 10.3390/vaccines3030579 579 596 2076-393X 2015-07-24 doi: 10.3390/vaccines3030579 Thomas Stratmann http://www.mdpi.com/2076-393X/3/3/556 Understanding the heterogeneity of groups along the vaccine hesitancy continuum presents an opportunity to tailor and increase the impact of public engagement efforts with these groups. Audience segmentation can support these goals, as demonstrated here in the context of the 2009 H1N1 vaccine. In March 2010, we surveyed 1569 respondents, drawn from a nationally representative sample of American adults, with oversampling of racial/ethnic minorities and persons living below the United States Federal Poverty Level. Guided by the Structural Influence Model, we assessed knowledge, attitudes, and behaviors related to H1N1; communication outcomes; and social determinants. Among those who did not receive the vaccine (n = 1166), cluster analysis identified three vaccine-hesitant subgroups. Disengaged Skeptics (67%) were furthest from vaccine acceptance, with low levels of concern and engagement. The Informed Unconvinced (19%) were sophisticated consumers of media and health information who may not have been reached with information to motivate vaccination. The Open to Persuasion cluster (14%) had the highest levels of concern and motivation and may have required engagement about vaccination broadly. There were significant sociodemographic differences between groups. This analysis highlights the potential to use segmentation techniques to identify subgroups on the vaccine hesitancy continuum and tailor public engagement efforts accordingly. Vaccines 2015-07-15 3 3 Article 10.3390/vaccines3030556 556 578 2076-393X 2015-07-15 doi: 10.3390/vaccines3030556 Shoba Ramanadhan Ezequiel Galarce Ziming Xuan Jaclyn Alexander-Molloy Kasisomayajula Viswanath http://www.mdpi.com/2076-393X/3/3/544 Therapeutic cancer vaccines do not hold promise yet as an effective anti-cancer treatment. Lack of efficacy or poor clinical outcomes are due to several antigenic and immunological aspects that need to be addressed in order to reverse such trends and significantly improve cancer vaccines' efficacy. The newly developed high throughput technologies and computational tools are instrumental to this aim allowing the identification of more specific antigens and the comprehensive analysis of the innate and adaptive immunities. Here, we review the potentiality of systems biology in providing novel insights in the mechanisms of the action of vaccines to improve their design and effectiveness. Vaccines 2015-07-14 3 3 Review 10.3390/vaccines3030544 544 555 2076-393X 2015-07-14 doi: 10.3390/vaccines3030544 Luisa Circelli Annacarmen Petrizzo Maria Tagliamonte Maria Tornesello Franco Buonaguro Luigi Buonaguro http://www.mdpi.com/2076-393X/3/3/519 Despite the promise of targeted therapies, there remains an urgent need for effective treatment for esophageal cancer (EC) and triple-negative breast cancer (TNBC). Current FDA-approved drugs have significant problems of toxicity, safety, selectivity, efficacy and development of resistance. In this manuscript, we demonstrate that rationally designed peptide vaccines/mimics are a viable therapeutic strategy for blocking aberrant molecular signaling pathways with high affinity, specificity, potency and safety. Specifically, we postulate that novel combination treatments targeting members of the EGFR family and IGF-1R will yield significant anti-tumor effects in in vitro models of EC and TNBC possibly overcoming mechanisms of resistance. We show that the combination of HER-1 and HER-2 or HER-1 and IGF-1R peptide mimics/vaccine antibodies exhibited enhanced antitumor properties with significant inhibition of tumorigenesis in OE19 EC and MDA-MB-231 TNBC cell lines. Our work elucidates the mechanisms of HER-1/IGF-1R and HER-1/HER-2 signaling in these cancer cell lines, and the promising results support the rationale for dual targeting with HER-1 and HER-2 or IGF-1R as an improved treatment regimen for advanced therapy tailored to difference types of cancer. Vaccines 2015-07-06 3 3 Article 10.3390/vaccines3030519 519 543 2076-393X 2015-07-06 doi: 10.3390/vaccines3030519 Jay Overholser Kristen Ambegaokar Siobhan Eze Eduardo Sanabria-Figueroa Rita Nahta Tanios Bekaii-Saab Pravin Kaumaya http://www.mdpi.com/2076-393X/3/3/503 Vaccines against dengue virus (DV) are commercially nonexistent. A subunit vaccination strategy may be of value, especially if a safe viral vector acts as biologically active adjuvant. In this paper, we focus on an immunoglobulin-like, independently folded domain III (DIII) from DV 2 envelope protein (E), which contains epitopes that elicits highly specific neutralizing antibodies. We modified the hepatitis B small surface antigen (HBsAg, S) in order to display DV 2 DIII on a virus-like particle (VLP), thus generating the hybrid antigen DIII-S. Two varieties of measles virus (MV) vectors were developed to express DIII-S. The first expresses the hybrid antigen from an additional transcription unit (ATU) and the second additionally expresses HBsAg from a separate ATU. We found that this second MV vectoring the hybrid VLPs displaying DIII-S on an unmodified HBsAg scaffold were immunogenic in MV-susceptible mice (HuCD46Ge-IFNarko), eliciting robust neutralizing responses (averages) against MV (1:1280 NT90), hepatitis B virus (787 mIU/mL), and DV2 (1:160 NT50) in all of the tested animals. Conversely, the MV vector expressing only DIII-S induced immunity against MV alone. In summary, DV2 neutralizing responses can be generated by displaying E DIII on a scaffold of HBsAg-based VLPs, vectored by MV. Vaccines 2015-07-03 3 3 Article 10.3390/vaccines3030503 503 518 2076-393X 2015-07-03 doi: 10.3390/vaccines3030503 Indira Harahap-Carrillo Ivonne Ceballos-Olvera Jorge Valle http://www.mdpi.com/2076-393X/3/3/490 Nowadays, immunotherapy represents one promising approach for cancer treatment. Recently, spectacular results of cancer immunotherapy clinical trials have confirmed the crucial role of immune system in cancer regression. Therapeutic cancer vaccine represents one widely used immunotherapy strategy to stimulate tumor specific T cell responses but clinical impact remains disappointing in targeting CD8 T cells. Although CD8 T cells have been initially considered to be the main protagonists, it is now clear that CD4 T cells also play a critical role in antitumor response. In this article, we discuss the role of tumor antigen-specific CD4 T cell responses and how we can target these cells to improve cancer vaccines. Vaccines 2015-06-30 3 3 Review 10.3390/vaccines3030490 490 502 2076-393X 2015-06-30 doi: 10.3390/vaccines3030490 Jeanne Galaine Christophe Borg Yann Godet Olivier Adotévi http://www.mdpi.com/2076-393X/3/2/467 Years of unsuccessful attempts at fighting established tumors with vaccines have taught us all that they are only able to truly impact patient survival when used in a preventive setting, as would normally be the case for traditional vaccines against infectious diseases. While true primary cancer prevention is still but a long-term goal, secondary and tertiary prevention are already in the clinic and providing encouraging results. A combination of immunopreventive cancer strategies and recently approved checkpoint inhibitors is a further promise of forthcoming successful cancer disease control, but prevention will require a considerable reduction of currently reported toxicities. These considerations summed with the increased understanding of tumor antigens allow space for an optimistic view of the future. Vaccines 2015-06-17 3 2 Review 10.3390/vaccines3020467 467 489 2076-393X 2015-06-17 doi: 10.3390/vaccines3020467 Pier-Luigi Lollini Federica Cavallo Patrizia Nanni Elena Quaglino http://www.mdpi.com/2076-393X/3/2/448 The barriers presented by immune suppression in the ovarian tumor microenvironment present one of the biggest challenges to development of successful tumor vaccine strategies for prevention of disease recurrence and progression following primary surgery and chemotherapy. New insights gained over the last decade have revealed multiple mechanisms of immune regulation, with ovarian tumor-associated macrophages/DC likely to fulfill a central role in creating a highly immunosuppressive milieu that supports disease progression and blocks anti-tumor immunity. This review provides an appraisal of some of the key signaling pathways that may contribute to immune suppression in ovarian cancer, with a particular focus on the potential involvement of the c-KIT/PI3K/AKT, wnt/β-catenin, IL-6/STAT3 and AhR signaling pathways in regulation of indoleamine 2,3-dioxygenase expression in tumor-associated macrophages. Knowledge of intercellular and intracellular circuits that shape immune suppression may afford insights for development of adjuvant treatments that alleviate immunosuppression in the tumor microenvironment and enhance the clinical efficacy of ovarian tumor vaccines. Vaccines 2015-05-29 3 2 Review 10.3390/vaccines3020448 448 466 2076-393X 2015-05-29 doi: 10.3390/vaccines3020448 Martin Cannon Debopam Ghosh Swetha Gujja http://www.mdpi.com/2076-393X/3/2/429 Vaccination has proven to be an invaluable means of preventing infectious diseases by reducing both incidence of disease and mortality. However, vaccines have not been effectively developed for many diseases including HIV-1, hepatitis C virus (HCV), tuberculosis and malaria, among others. The emergence of new technologies with a growing understanding of host-pathogen interactions and immunity may lead to efficacious vaccines against pathogens, previously thought impossible. Vaccines 2015-05-26 3 2 Review 10.3390/vaccines3020429 429 447 2076-393X 2015-05-26 doi: 10.3390/vaccines3020429 Rebecca Loomis Philip Johnson http://www.mdpi.com/2076-393X/3/2/420 Antibodies to immune checkpoints have entered the clinical arena and have been shown to provide a clinical benefit for metastatic melanoma and, possibly, for other tumors as well. In this review paper we summarize this therapeutic activity and underline the functional mechanisms that may be involved. Among them, we discuss the so far neglected role of tumor-associated antigens (TAAs) deriving from tumor somatic mutations and summarize the results of recent trials showing the immunogenic strength of such TAAs which can be specifically targeted by T cells activated by immune checkpoint antibodies. Finally we discuss new immunotherapy approaches that involve the combination of self/shared- or neo-TAAs-based vaccines and immune checkpoint blockade antibodies, to increase the clinical response of metastatic melanoma patients. Vaccines 2015-05-21 3 2 Review 10.3390/vaccines3020420 420 428 2076-393X 2015-05-21 doi: 10.3390/vaccines3020420 Giorgio Parmiani Cristina Maccalli Michele Maio http://www.mdpi.com/2076-393X/3/2/408 Developing countries disproportionately suffer from the burden of cervical cancer yet lack the resources to establish systematic screening programs that have resulted in significant reductions in morbidity and mortality in developed countries. Human Papillomavirus (HPV) vaccination provides an opportunity for primary prevention of cervical cancer in low-resource settings through vaccine provision by Gavi The Vaccine Alliance. In addition to the traditional national introduction, countries can apply for a demonstration program to help them make informed decisions for subsequent national introduction. This article summarizes information from approved Gavi HPV demonstration program proposals and preliminary implementation findings. After two rounds of applications, 23 countries have been approved targeting approximately 400,000 girls for vaccination. All countries are proposing primarily school-based strategies with mixed strategies to locate and vaccinate girls not enrolled in school. Experiences to date include: Reaching marginalized girls has been challenging; Strong coordination with the education sector is key and overall acceptance has been high. Initial coverage reports are encouraging but will have to be confirmed in population based coverage surveys that will take place later this year. Experiences from these countries are consistent with existing literature describing other HPV vaccine pilots in low-income settings. Vaccines 2015-05-20 3 2 Review 10.3390/vaccines3020408 408 419 2076-393X 2015-05-20 doi: 10.3390/vaccines3020408 Celina Hanson Linda Eckert Paul Bloem Tania Cernuschi http://www.mdpi.com/2076-393X/3/2/390 Adjuvants improve host responsiveness to co-delivered vaccines through a variety of mechanisms. Agents that trigger cells expressing Toll-like receptors (TLR) activate an innate immune response that enhances the induction of vaccine-specific immunity. When administered in combination with vaccines designed to prevent or slow tumor growth, TLR agonists have significantly improved the generation of cytotoxic T lymphocytes. Unfortunately, vaccines containing TLR agonists have rarely been able to eliminate large established tumors when administered systemically. To improve efficacy, attention has focused on delivering TLR agonists intra-tumorally with the intent of altering the tumor microenvironment. Agonists targeting TLRs 7/8 or 9 can reduce the frequency of Tregs while causing immunosuppressive MDSC in the tumor bed to differentiate into tumoricidal macrophages thereby enhancing tumor elimination. This work reviews pre-clinical and clinical studies concerning the utility of TLR 7/8/9 agonists as adjuvants for tumor vaccines. Vaccines 2015-05-08 3 2 Review 10.3390/vaccines3020390 390 407 2076-393X 2015-05-08 doi: 10.3390/vaccines3020390 Hidekazu Shirota Debra Tross Dennis Klinman http://www.mdpi.com/2076-393X/3/2/373 Influenza is a major respiratory pathogen causing annual outbreaks and occasional pandemics. Influenza vaccination is the major method of prophylaxis. Currently annual influenza vaccination is recommended for groups at high risk of complications from influenza infection such as pregnant women, young children, people with underlying disease and the elderly, along with occupational groups such a healthcare workers and farm workers. There are two main types of vaccines available: the parenteral inactivated influenza vaccine and the intranasal live attenuated influenza vaccine. The inactivated vaccines are licensed from 6 months of age and have been used for more than 50 years with a good safety profile. Inactivated vaccines are standardized according to the presence of the viral major surface glycoprotein hemagglutinin and protection is mediated by the induction of vaccine strain specific antibody responses. In contrast, the live attenuated vaccines are licensed in Europe for children from 2–17 years of age and provide a multifaceted immune response with local and systemic antibody and T cell responses but with no clear correlate of protection. Here we discuss the immunological immune responses elicited by the two vaccines and discuss future work to better define correlates of protection. Vaccines 2015-04-24 3 2 Review 10.3390/vaccines3020373 373 389 2076-393X 2015-04-24 doi: 10.3390/vaccines3020373 Saranya Sridhar Karl Brokstad Rebecca Cox http://www.mdpi.com/2076-393X/3/2/344 With its vast amount of uncharacterized and characterized T cell epitopes available for activating CD4+ T helper and CD8+ cytotoxic lymphocytes simultaneously, whole tumor antigen represents an attractive alternative source of antigens as compared to tumor-derived peptides and full-length recombinant tumor proteins for dendritic cell (DC)-based immunotherapy. Unlike defined tumor-derived peptides and proteins, whole tumor lysate therapy is applicable to all patients regardless of their HLA type. DCs are essentially the master regulators of immune response, and are the most potent antigen-presenting cell population for priming and activating naïve T cells to target tumors. Because of these unique properties, numerous DC-based immunotherapies have been initiated in the clinics. In this review, we describe the different types of whole tumor antigens that we could use to pulse DCs ex vivo and in vivo. We also discuss the different routes of delivering whole tumor antigens to DCs in vivo and activating them with toll-like receptor agonists. Vaccines 2015-04-23 3 2 Review 10.3390/vaccines3020344 344 372 2076-393X 2015-04-23 doi: 10.3390/vaccines3020344 Cheryl Chiang George Coukos Lana Kandalaft http://www.mdpi.com/2076-393X/3/2/320 The concept of stimulating the body's immune response is the basis underlying vaccination. Vaccines act by initiating the innate immune response and activating antigen presenting cells (APCs), thereby inducing a protective adaptive immune response to a pathogen antigen. Adjuvants are substances added to vaccines to enhance the immunogenicity of highly purified antigens that have insufficient immunostimulatory capabilities, and have been used in human vaccines for more than 90 years. While early adjuvants (aluminum, oil-in-water emulsions) were used empirically, rapidly increasing knowledge on how the immune system interacts with pathogens means that there is increased understanding of the role of adjuvants and how the formulation of modern vaccines can be better tailored towards the desired clinical benefit. Continuing safety evaluation of licensed vaccines containing adjuvants/adjuvant systems suggests that their individual benefit-risk profile remains favorable. Adjuvants contribute to the initiation of the innate immune response induced by antigens; exemplified by inflammatory responses at the injection site, with mostly localized and short-lived effects. Activated effectors (such as APCs) then move to draining lymph nodes where they direct the type, magnitude and quality of the adaptive immune response. Thus, the right match of antigens and adjuvants can potentiate downstream adaptive immune responses, enabling the development of new efficacious vaccines. Many infectious diseases of worldwide significance are not currently preventable by vaccination. Adjuvants are the most advanced new technology in the search for new vaccines against challenging pathogens and for vulnerable populations that respond poorly to traditional vaccines. Vaccines 2015-04-16 3 2 Review 10.3390/vaccines3020320 320 343 2076-393X 2015-04-16 doi: 10.3390/vaccines3020320 Alberta Pasquale Scott Preiss Fernanda Silva Nathalie Garçon http://www.mdpi.com/2076-393X/3/2/293 Influenza A virus is a respiratory pathogen which causes both seasonal epidemics and occasional pandemics; infection continues to be a significant cause of mortality worldwide. Current influenza vaccines principally stimulate humoral immune responses that are largely directed towards the variant surface antigens of influenza. Vaccination can result in an effective, albeit strain-specific antibody response and there is a need for vaccines that can provide superior, long-lasting immunity to influenza. Vaccination approaches targeting conserved viral antigens have the potential to provide broadly cross-reactive, heterosubtypic immunity to diverse influenza viruses. However, the field lacks consensus on the correlates of protection for cellular immunity in reducing severe influenza infection, transmission or disease outcome. Furthermore, unlike serological methods such as the standardized haemagglutination inhibition assay, there remains a large degree of variation in both the types of assays and method of reporting cellular outputs. T-cell directed immunity has long been known to play a role in ameliorating the severity and/or duration of influenza infection, but the precise phenotype, magnitude and longevity of the requisite protective response is unclear. In order to progress the development of universal influenza vaccines, it is critical to standardize assays across sites to facilitate direct comparisons between clinical trials. Vaccines 2015-04-14 3 2 Review 10.3390/vaccines3020293 293 319 2076-393X 2015-04-14 doi: 10.3390/vaccines3020293 Lynda Coughlan Teresa Lambe http://www.mdpi.com/2076-393X/3/2/263 Obtaining approval for a multinational vaccine trial from an ethics committee and the national competent authority of different Member States of the European Union (EU) is challenging under clinical trial Directive 2001/20/EC because of the differences in the implementation of the directive in national laws of Member States. In this review the national differences in requirements for ethical and competent authority approval are illustrated. The national ethical and competent authority review procedures in Finland, Hungary, The Netherlands, Norway and Slovenia are described under the EU trial directive after discussing the provisions of the trial directive related to both review procedures. The review illustrates the differences between the countries in the documents that have to be submitted for the review procedures, the submission procedures and the language requirements of the documents, the organization of the ethics committees and the role of the competent authority in the approval procedure. Vaccines 2015-04-14 3 2 Review 10.3390/vaccines3020263 263 292 2076-393X 2015-04-14 doi: 10.3390/vaccines3020263 Eva van Doorn Eelko Hak Bob Wilffert http://www.mdpi.com/2076-393X/3/2/239 Influenza viruses have a huge impact on public health. Current influenza vaccines need to be updated annually and protect poorly against antigenic drift variants or novel emerging subtypes. Vaccination against influenza can be improved in two important ways, either by inducing more broadly protective immune responses or by decreasing the time of vaccine production, which is relevant especially during a pandemic outbreak. In this review, we outline the current efforts to develop so-called "universal influenza vaccines", describing antigens that may induce broadly protective immunity and novel vaccine production platforms that facilitate timely availability of vaccines. Vaccines 2015-03-26 3 2 Review 10.3390/vaccines3020239 239 262 2076-393X 2015-03-26 doi: 10.3390/vaccines3020239 Lidewij Wiersma Guus Rimmelzwaan Rory de Vries http://www.mdpi.com/2076-393X/3/2/221 The skin is an attractive organ for immunization because of the presence of antigen-presenting cells. Intradermal delivery via tattooing has demonstrated superior vaccine immunogenicity of DNA vaccines in comparison to conventional delivery methods. In this study, we explored the efficacy of tattoo injection of a tumor vaccine based on recombinant Semliki Forest virus replicon particles (rSFV) targeting human papillomavirus (HPV). Tattoo injection of rSFV particles resulted in antigen expression in both the skin and draining lymph nodes. In comparison with intramuscular injection, the overall antigen expression determined at the site of administration and draining lymph nodes was 10-fold lower upon tattoo injection. Delivery of SFV particles encoding the E6 and E7 antigens of human papillomavirus type 16 (SFVeE6,7) via tattooing resulted in HPV-specific cytotoxic T cells and in vivo therapeutic antitumor response. Strikingly, despite the observed lower overall transgene expression, SFVeE6,7 delivered via tattoo injection resulted in higher or equal levels of immune responses as compared to intramuscular injection. The intrinsic immunogenic potential of tattooing provides a benefit for immunotherapy based on an alphavirus. Vaccines 2015-03-24 3 2 Article 10.3390/vaccines3020221 221 238 2076-393X 2015-03-24 doi: 10.3390/vaccines3020221 Stephanie van de Wall Mateusz Walczak Nienke van Rooij Baukje-Nynke Hoogeboom Tjarko Meijerhof Hans Nijman Toos Daemen http://www.mdpi.com/2076-393X/3/2/203 Tumor vaccine design requires prediction and validation of immunogenic MHC class I epitopes expressed by target cells as well as MHC class II epitopes expressed by antigen-presenting cells essential for the induction of optimal immune responses. Epitope prediction methods are based on different algorithms and are instrumental for a first screening of possible epitopes. However, their results do not reflect a one-to-one correlation with experimental data. We combined several in silico prediction methods to unravel the most promising C57BL/6 mouse-restricted Hepatitis C virus (HCV) MHC class I epitopes and validated these epitopes in vitro and in vivo. Cytotoxic T lymphocyte (CTL) epitopes within the HCV non-structural proteins were identified, and proteasomal cleavage sites and helper T cell (Th) epitopes at close proximity to these CTL epitopes were analyzed using multiple prediction algorithms. This combined in silico analysis enhances the precision of identification of functional HCV-specific CTL epitopes. This approach will be applicable to the design of human vaccines not only for HCV, but also for other antigens in which T-cell responses play a crucial role. Vaccines 2015-03-24 3 2 Article 10.3390/vaccines3020203 203 220 2076-393X 2015-03-24 doi: 10.3390/vaccines3020203 Peng Ip Hans Nijman Toos Daemen http://www.mdpi.com/2076-393X/3/1/186 Gene-based vaccines as typified by plasmid DNA vaccines and recombinant viral-vectored vaccines are expected as promising solutions against infectious diseases for which no effective prophylactic vaccines exist such as HIV, dengue virus, Ebola virus and malaria, and for which more improved vaccines are needed such as tuberculosis and influenza virus. Although many preclinical and clinical trials have been conducted to date, no DNA vaccines or recombinant viral-vectored vaccines expressing heterologous antigens for human use have yet been licensed in the U.S., Europe or Japan. In this research, we describe the current regulatory context for gene-based prophylactic vaccines against infectious disease in the U.S., Europe, and Japan. We identify the important considerations, in particular, on the preclinical assessments that would allow these vaccines to proceed to clinical trials, and the differences on the regulatory pathway for the marketing authorization in each region. Vaccines 2015-03-18 3 1 Article 10.3390/vaccines3010186 186 202 2076-393X 2015-03-18 doi: 10.3390/vaccines3010186 Yoshikazu Nakayama Atsushi Aruga http://www.mdpi.com/2076-393X/3/1/172 In the last 20 years, novel non-seasonal influenza viruses have emerged, most of which have originated from birds. Despite their apparent inability to cause pandemics, with the exception of H1N1 swine influenza virus, these viruses still constitute a constant threat to public health. While general concern has decreased after the peak of the H5N1 virus, in recent years several novel reassorted influenza viruses (e.g., H7N9, H9N2, H10N8) have jumped the host-species barrier and are under surveillance by the scientific community and public health systems. It is still unclear whether these viruses can actually cause pandemics or just isolated episodes. The purpose of this review is to provide an overview of old and novel potential pandemic strains of recent decades. Vaccines 2015-03-18 3 1 Review 10.3390/vaccines3010172 172 185 2076-393X 2015-03-18 doi: 10.3390/vaccines3010172 Claudia Trombetta Simona Piccirella Daniele Perini Otfried Kistner Emanuele Montomoli http://www.mdpi.com/2076-393X/3/1/148 The existence of pathogens that escape recognition by specific vaccines, the need to improve existing vaccines and the increased availability of therapeutic (non-infectious disease) vaccines necessitate the rational development of novel vaccine concepts based on the induction of protective cell-mediated immune responses. For naive T-cell activation, several signals resulting from innate and adaptive interactions need to be integrated, and adjuvants may interfere with some or all of these signals. Adjuvants, for example, are used to promote the immunogenicity of antigens in vaccines, by inducing a pro-inflammatory environment that enables the recruitment and promotion of the infiltration of phagocytic cells, particularly antigen-presenting cells (APC), to the injection site. Adjuvants can enhance antigen presentation, induce cytokine expression, activate APC and modulate more downstream adaptive immune reactions (vaccine delivery systems, facilitating immune Signal 1). In addition, adjuvants can act as immunopotentiators (facilitating Signals 2 and 3) exhibiting immune stimulatory effects during antigen presentation by inducing the expression of co-stimulatory molecules on APC. Together, these signals determine the strength of activation of specific T-cells, thereby also influencing the quality of the downstream T helper cytokine profiles and the differentiation of antigen-specific T helper populations (Signal 3). New adjuvants should also target specific (innate) immune cells in order to facilitate proper activation of downstream adaptive immune responses and homing (Signal 4). It is desirable that these adjuvants should be able to exert such responses in the context of mucosal administered vaccines. This review focuses on the understanding of the potential working mechanisms of the most well-known classes of adjuvants to be used effectively in vaccines. Vaccines 2015-03-05 3 1 Review 10.3390/vaccines3010148 148 171 2076-393X 2015-03-05 doi: 10.3390/vaccines3010148 Huub Savelkoul Valerie Ferro Marius Strioga Virgil Schijns http://www.mdpi.com/2076-393X/3/1/137 Immunization of health care workers (HCWs) against influenza has been associated with improvements in patient safety. The aim of this study is to assess the beliefs, attitudes, and knowledge of HCWs and health profession students regarding influenza. An anonymous questionnaire was distributed to HCWs in three local Florentine healthcare units, at Careggi University Teaching Hospital, and to students in health profession degree programs. A total of 2576 questionnaires were fully completed. A total of 12.3% of subjects responded that they were "always vaccinated" in all three of the seasonal vaccination campaigns studied (2007–2008 to 2009–2010), 13.1% had been vaccinated once or twice, and 74.6% had not received vaccinations. Although the enrolled subjects tended to respond that they were "never vaccinated," they considered influenza to be a serious illness and believed that the influenza vaccine is effective. The subjects who refused vaccination more frequently believed that the vaccine could cause influenza and that it could have serious side effects. More than 60% of the "always vaccinated" group completely agreed that HCWs should be vaccinated. Self-protection and protecting family members or other people close to the respondent from being infected and representing potential sources of influenza infection can be considered motivating factors for vaccination. The results highlight the importance of improving vaccination rates among all HCWs through multi-component interventions. Knowledge of influenza should be reinforced. Vaccines 2015-02-26 3 1 Article 10.3390/vaccines3010137 137 147 2076-393X 2015-02-26 doi: 10.3390/vaccines3010137 Guglielmo Bonaccorsi Francesca Santomauro Barbara Porchia Giuditta Niccolai Elettra Pellegrino Paolo Bonanni Chiara Lorini http://www.mdpi.com/2076-393X/3/1/105 The successful isolation of a human influenza virus in 1933 was soon followed by the first attempts to develop an influenza vaccine. Nowadays, vaccination is still the most effective method to prevent human influenza disease. However, licensed influenza vaccines offer protection against antigenically matching viruses, and the composition of these vaccines needs to be updated nearly every year. Vaccines that target conserved epitopes of influenza viruses would in principle not require such updating and would probably have a considerable positive impact on global human health in case of a pandemic outbreak. The extracellular domain of Matrix 2 (M2e) protein is an evolutionarily conserved region in influenza A viruses and a promising epitope for designing a universal influenza vaccine. Here we review the seminal and recent studies that focused on M2e as a vaccine antigen. We address the mechanism of action and the clinical development of M2e-vaccines. Finally, we try to foresee how M2e-based vaccines could be implemented clinically in the future. Vaccines 2015-02-13 3 1 Review 10.3390/vaccines3010105 105 136 2076-393X 2015-02-13 doi: 10.3390/vaccines3010105 Lei Deng Ki Cho Walter Fiers Xavier Saelens http://www.mdpi.com/2076-393X/3/1/90 The potency of vaccines must be determined to ensure that the appropriate dose is given. The manufacture and assessment of influenza vaccines are complicated by the continuously changing nature of the pathogen, which makes efficacy estimates difficult but also confounds attempts to produce a well-validated, consistent potency assay. Single radial diffusion has been used for decades and provides a relatively simple way to measure the amount of biologically active materials present in the vaccine. It requires reagents, which are updated on a regular, frequently yearly, basis and alternative methods continue to be sought. Vaccines 2015-02-05 3 1 Review 10.3390/vaccines3010090 90 104 2076-393X 2015-02-05 doi: 10.3390/vaccines3010090 Philip Minor http://www.mdpi.com/2076-393X/3/1/74 Epstein-Barr virus (EBV) infects B-, T-, and NK cells and has been associated not only with a wide range of lymphoid malignancies but also with autoimmune diseases such as lupus erythematosus, rheumatoid arthritis and, in particular, multiple sclerosis. Hence, effective immunotherapeutic approaches to eradicate EBV infection might overthrow cancer and autoimmunity incidence. However, currently no effective anti-EBV immunotherapy is available. Here we use the concept that protein immunogenicity is allocated in rare peptide sequences and search the Epstein-Barr nuclear antigen 1 (EBNA1) sequence for peptides unique to the viral protein and absent in the human host. We report on a set of unique EBV EBNA1 peptides that might be used in designing peptide-based therapies able to specifically hitting the virus or neutralizing pathogenic autoantibodies. Vaccines 2015-02-05 3 1 Article 10.3390/vaccines3010074 74 89 2076-393X 2015-02-05 doi: 10.3390/vaccines3010074 Giovanni Capone Candida Fasano Guglielmo Lucchese Michele Calabrò Darja Kanduc http://www.mdpi.com/2076-393X/3/1/22 Influenza A virus in swine (IAV-S) is one of the most important infectious disease agents of swine in North America. In addition to the economic burden of IAV-S to the swine industry, the zoonotic potential of IAV-S sometimes leads to serious public health concerns. Adjuvanted, inactivated vaccines have been licensed in the United States for over 20 years, and there is also widespread usage of autogenous/custom IAV-S vaccines. Vaccination induces neutralizing antibodies and protection against infection with very similar strains. However, IAV-S strains are so diverse and prone to mutation that these vaccines often have disappointing efficacy in the field. This scientific review was developed to help veterinarians and others to identify the best available IAV-S vaccine for a particular infected herd. We describe key principles of IAV-S structure and replication, protective immunity, currently available vaccines, and vaccine technologies that show promise for the future. We discuss strategies to optimize the use of available IAV-S vaccines, based on information gathered from modern diagnostics and surveillance programs. Improvements in IAV-S immunization strategies, in both the short term and long term, will benefit swine health and productivity and potentially reduce risks to public health. Vaccines 2015-01-30 3 1 Review 10.3390/vaccines3010022 22 73 2076-393X 2015-01-30 doi: 10.3390/vaccines3010022 Matthew Sandbulte Anna Spickler Pamela Zaabel James Roth http://www.mdpi.com/2076-393X/3/1/20 The editors of Vaccines would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2014:[...] Vaccines 2015-01-08 3 1 Editorial 10.3390/vaccines3010020 20 21 2076-393X 2015-01-08 doi: 10.3390/vaccines3010020 Vaccines Editorial Office http://www.mdpi.com/2076-393X/3/1/1 China's commitment to implementing established and emerging HIV/AIDS prevention and control strategies has led to substantial gains in terms of access to antiretroviral treatment and prevention services, but the evolving and multifaceted HIV/AIDS epidemic in China highlights the challenges of maintaining that response. This study presents modeling results exploring the potential impact of HIV vaccines in the Chinese context at varying efficacy and coverage rates, while further exploring the potential implications of vaccination programs aimed at reaching populations at highest risk of HIV infection. A preventive HIV vaccine would add a powerful tool to China's response, even if not 100% efficacious or available to the full population. Vaccines 2015-01-05 3 1 Article 10.3390/vaccines3010001 1 19 2076-393X 2015-01-05 doi: 10.3390/vaccines3010001 Thomas Harmon Wei Guo John Stover Zunyou Wu Joan Kaufman Kammerle Schneider Li Liu Liao Feng Bernard Schwartländer http://www.mdpi.com/2076-393X/2/4/841 Standard-of-care cisplatin and radiation therapy (CRT) provides significant tumor control of human papillomavirus (HPV)-mediated head and neck squamous cell carcinomas (HNSCCs); this effectiveness depends on CRT-mediated activation of the patient's own immune system. However, despite good survival, patients suffer significant morbidity necessitating on-going studies to define novel therapies that alleviate this burden. Given the role of the immune system in tumor clearance, immune modulation may further potentiate the CRT-activated response while potentially decreasing morbidity. CD137, an inducible cell surface receptor found on activated T cells, is involved in differentiation and survival signaling in T cells upon binding of its natural partner (CD137L). A number of studies have shown the effectiveness of targeting this immune-stimulatory pathway in regards to tumor clearance. Here, we test its role in HPV+ HNSCC tumor clearance using a previously characterized mouse model. We show that amplification of this stimulatory pathway synergizes with CRT for enhanced tumor clearance. Interestingly, tumor clearance is further potentiated by local tumor cell expression of CD137L. Vaccines 2014-12-10 2 4 Article 10.3390/vaccines2040841 841 853 2076-393X 2014-12-10 doi: 10.3390/vaccines2040841 Christopher Lucido Paola Vermeer Bryant Wieking Daniel Vermeer John Lee http://www.mdpi.com/2076-393X/2/4/832 Vaccines are commonly used as a preventive medicine for infectious diseases worldwide; however, the trial for an amyloid beta vaccine against Alzheimer's disease will open a new concept in vaccination. In case of therapeutic vaccines for cancer, their targets are usually specific antigens in cancer cells, allowing activated cytotoxic T cells (CTLs) to attach and remove the antigen-presenting cancer cells. In our therapeutic vaccines against hypertension, the target is angiotensin II (Ang II) and induced anti-Ang II antibodies could efficiently ameliorate high blood pressure. Similarly, we developed the therapeutic vaccine against DPP4 for diabetes mellitus. However, because Ang II or DPP4 is an endogenous hormone, we must avoid autoimmune disease induced by these vaccines. Therefore, our system was used to design a therapeutic vaccine that elicits anti-Ang II or DPP4 antibodies without CTL activation against Ang II or DPP4. In this review, we will describe our concept of therapeutic vaccines for hypertension and diabetes mellitus. Vaccines 2014-11-26 2 4 Review 10.3390/vaccines2040832 832 840 2076-393X 2014-11-26 doi: 10.3390/vaccines2040832 Hironori Nakagami Hiroshi Koriyama Ryuichi Morishita http://www.mdpi.com/2076-393X/2/4/797 Equine influenza (EI) is a major respiratory disease of horses, which is still causing substantial outbreaks worldwide despite several decades of surveillance and prevention. Alongside quarantine procedures, vaccination is widely used to prevent or limit spread of the disease. The panel of EI vaccines commercially available is probably one of the most varied, including whole inactivated virus vaccines, Immuno-Stimulating Complex adjuvanted vaccines (ISCOM and ISCOM-Matrix), a live attenuated equine influenza virus (EIV) vaccine and a recombinant poxvirus-vectored vaccine. Several other strategies of vaccination are also evaluated. This systematic review reports the advances of EI vaccines during the last few years as well as some of the mechanisms behind the inefficient or sub-optimal response of horses to vaccination. Vaccines 2014-11-14 2 4 Review 10.3390/vaccines2040797 797 831 2076-393X 2014-11-14 doi: 10.3390/vaccines2040797 Romain Paillot http://www.mdpi.com/2076-393X/2/4/785 This special issue is focused on DNA vaccines, marking the two decades since the first demonstration of pre-clinical protection was published in Science (Ulmer et al.; Heterologous protection against influenza by injection of DNA encoding a viral protein. 1993). This introductory article provides an overview of the field and highlights the observations of the articles in this special issue while placing them in the context of other recent publications. Vaccines 2014-10-27 2 4 Editorial 10.3390/vaccines2040785 785 796 2076-393X 2014-10-27 doi: 10.3390/vaccines2040785 Britta Wahren Margaret Liu http://www.mdpi.com/2076-393X/2/4/772 In previous studies, we demonstrated in mice and prairie dogs that simultaneous administration of two recombinant raccoon poxviruses (rRCN) expressing Yersinia pestis antigens (F1 and V307—a truncated version of the V protein) provided superior protection against plague challenge compared to individual single antigen constructs. To reduce costs of vaccine production and facilitate implementation of a sylvatic plague vaccine (SPV) control program for prairie dogs, a dual antigen construct is more desirable. Here we report the construction and characterization of a novel RCN-vectored vaccine that simultaneously expresses both F1 and V307 antigens. This dual antigen vaccine provided similar levels of protection against plague in both mice and prairie dogs as compared to simultaneous administration of the two single antigen constructs and was also shown to protect mice against an F1 negative strain of Y. pestis. The equivalent safety, immunogenicity and efficacy profile of the dual RCN-F1/V307 construct warrants further evaluation in field efficacy studies in sylvatic plague endemic areas. Vaccines 2014-10-27 2 4 Article 10.3390/vaccines2040772 772 784 2076-393X 2014-10-27 doi: 10.3390/vaccines2040772 Tonie Rocke Brock Kingstad-Bakke Willy Berlier Jorge Osorio http://www.mdpi.com/2076-393X/2/4/755 The LC16m8 strain of vaccinia virus, the active ingredient in the Japanese smallpox vaccine, was derived from the Lister/Elstree strain. LC16m8 is replication-competent and has been administered to over 100,000 infants and 3,000 adults with no serious adverse reactions. Despite this outstanding safety profile, the occurrence of spontaneously-generated large plaque-forming virulent LC16m8 revertants following passage in cell culture is a major drawback. We identified the gene responsible for the reversion and deleted the gene (B5R) from LC16m8 to derive LC16m8Δ. LC16m8∆ is non-pathogenic in immunodeficient severe combined immunodeficiency (SCID) mice, genetically-stable and does not reverse to a large-plaque phenotype upon passage in cell culture, even under conditions in which most LC16m8 populations are replaced by revertants. Moreover, LC16m8∆ is >500-fold more effective than the non-replicating vaccinia virus (VV), Modified Vaccinia Ankara (MVA), at inducing murine immune responses against pathogenic VV. LC16m8∆, which expresses the SIV gag gene, also induced anti-Gag CD8+ T-cells more efficiently than MVA and another non-replicating VV, Dairen I minute-pock variants (DIs). Moreover, LC16m8∆ expressing HIV-1 Env in combination with a Sendai virus vector induced the production of anti-Env antibodies and CD8+ T-cells. Thus, the safety and efficacy of LC16m8∆ mean that it represents an outstanding platform for the development of human vaccine vectors. Vaccines 2014-10-17 2 4 Review 10.3390/vaccines2040755 755 771 2076-393X 2014-10-17 doi: 10.3390/vaccines2040755 Minoru Kidokoro Hisatoshi Shida http://www.mdpi.com/2076-393X/2/4/735 Dendritic cells (DC) play essential roles determining efficacy of vaccine delivery with respect to immune defence development and regulation. This renders DCs important targets for vaccine delivery, particularly RNA vaccines. While delivery of interfering RNA oligonucleotides to the appropriate intracellular sites for RNA-interference has proven successful, the methodologies are identical for RNA vaccines, which require delivery to RNA translation sites. Delivery of mRNA has benefitted from application of cationic entities; these offer value following endocytosis of RNA, when cationic or amphipathic properties can promote endocytic vesicle membrane perturbation to facilitate cytosolic translocation. The present review presents how such advances are being applied to the delivery of a new form of RNA vaccine, replicons (RepRNA) carrying inserted foreign genes of interest encoding vaccine antigens. Approaches have been developed for delivery to DCs, leading to the translation of the RepRNA and encoded vaccine antigens both in vitro and in vivo. Potential mechanisms favouring efficient delivery leading to translation are discussed with respect to the DC endocytic machinery, showing the importance of cytosolic translocation from acidifying endocytic structures. The review relates the DC endocytic pathways to immune response induction, and the potential advantages for these self-replicating RNA vaccines in the near future. Vaccines 2014-10-16 2 4 Review 10.3390/vaccines2040735 735 754 2076-393X 2014-10-16 doi: 10.3390/vaccines2040735 Kenneth McCullough Panagiota Milona Lisa Thomann-Harwood Thomas Démoulins Pavlos Englezou Rolf Suter Nicolas Ruggli http://www.mdpi.com/2076-393X/2/4/707 Serological techniques commonly used to quantify influenza-specific antibodies include the Haemagglutination Inhibition (HI), Single Radial Haemolysis (SRH) and Virus Neutralization (VN) assays. HI and SRH are established and reproducible techniques, whereas VN is more demanding. Every new influenza vaccine needs to fulfil the strict criteria issued by the European Medicines Agency (EMA) in order to be licensed. These criteria currently apply exclusively to SRH and HI assays and refer to two different target groups—healthy adults and the elderly, but other vaccine recipient age groups have not been considered (i.e., children). The purpose of this timely review is to highlight the current scenario on correlates of protection concerning influenza vaccines and underline the need to revise the criteria and assays currently in use. In addition to SRH and HI assays, the technical advantages provided by other techniques such as the VN assay, pseudotype-based neutralization assay, neuraminidase and cell-mediated immunity assays need to be considered and regulated via EMA criteria, considering the many significant advantages that they could offer for the development of effective vaccines. Vaccines 2014-10-13 2 4 Review 10.3390/vaccines2040707 707 734 2076-393X 2014-10-13 doi: 10.3390/vaccines2040707 Claudia Trombetta Daniele Perini Stuart Mather Nigel Temperton Emanuele Montomoli http://www.mdpi.com/2076-393X/2/4/686 Gene-based vaccination strategies, specifically viral vectors encoding vaccine immunogens are effective at priming strong immune responses. Mucosal routes offer practical advantages for vaccination by ease of needle-free administration, and immunogen delivery at readily accessible oral/nasal sites to efficiently induce immunity at distant gut and genital tissues. However, since mucosal tissues are inherently tolerant for induction of immune responses, incorporation of adjuvants for optimal mucosal vaccination strategies is important. We report here the effectiveness of alpha-galactosylceramide (α-GalCer), a synthetic glycolipid agonist of natural killer T (NKT) cells, as an adjuvant for enhancing immunogenicity of vaccine antigens delivered using viral vectors by mucosal routes in murine and nonhuman primate models. Significant improvement in adaptive immune responses in systemic and mucosal tissues was observed by including α-GalCer adjuvant for intranasal immunization of mice with vesicular stomatitis virus vector encoding the model antigen ovalbumin and adenoviral vectors expressing HIV env and Gag antigens. Activation of NKT cells in systemic and mucosal tissues along with significant increases in adaptive immune responses were observed in rhesus macaques immunized by intranasal and sublingual routes with protein or adenovirus vectored antigens when combined with α-GalCer adjuvant. These results support the utility of α-GalCer adjuvant for enhancing immunogenicity of mucosal vaccines delivered using viral vectors. Vaccines 2014-10-10 2 4 Article 10.3390/vaccines2040686 686 706 2076-393X 2014-10-10 doi: 10.3390/vaccines2040686 Shailbala Singh Pramod Nehete Guojun Yang Hong He Bharti Nehete Patrick Hanley Michael Barry K. Sastry http://www.mdpi.com/2076-393X/2/3/654 There is currently no vaccine available for human use for any parasitic infections, including the helminth disease, schistosomiasis. Despite many researchers working towards this goal, one of the focuses has been on identifying new antigenic targets. The bar to achieve protective efficacy in humans was set at a consistent induction of 40% protection or better by the World Health Organisation (WHO), and although this is a modest goal, it is yet to be reached with the six most promising schistosomiasis vaccine candidates (Sm28GST, IrV5, Sm14, paramyosin, TPI, and Sm23). Adjuvant selection has a large impact on the effectiveness of the vaccine, and the use of adjuvants to aid in the stimulation of the immune system is a critical step and a major variable affecting vaccine development. In addition to a comprehensive understanding of the immune system, level of protection and the desired immune response required, there is also a need for a standardised and effective adjuvant formulation. This review summarises the status of adjuvants that have been or are being employed in schistosomiasis vaccine development focusing on immunisation outcomes at preclinical and clinical stages. Vaccines 2014-09-02 2 3 Review 10.3390/vaccines2030654 654 685 2076-393X 2014-09-02 doi: 10.3390/vaccines2030654 Rachel Stephenson Hong You Donald McManus Istvan Toth http://www.mdpi.com/2076-393X/2/3/642 Plants represent a safe, efficacious and inexpensive production platform by which to provide vaccines and other therapeutic proteins to the world's poor. Plant virus expression vector technology has rapidly become one of the most popular methods to express pharmaceutical proteins in plants. This review discusses several of the state-of-the-art plant expression systems based upon geminiviruses that have been engineered for vaccine production. An overview of the advantages of these small, single-stranded DNA viruses is provided and comparisons are made with other virus expression systems. Advances in the design of several different geminivirus vectors are presented in this review, and examples of vaccines and other biologics generated from each are described. Vaccines 2014-08-05 2 3 Review 10.3390/vaccines2030642 642 653 2076-393X 2014-08-05 doi: 10.3390/vaccines2030642 Kathleen Hefferon http://www.mdpi.com/2076-393X/2/3/624 Viral vectors are promising tools for gene therapy and vaccines. Viral vector-based vaccines can enhance immunogenicity without an adjuvant and induce a robust cytotoxic T lymphocyte (CTL) response to eliminate virus-infected cells. During the last several decades, many types of viruses have been developed as vaccine vectors. Each has unique features and parental virus-related risks. In addition, genetically altered vectors have been developed to improve efficacy and safety, reduce administration dose, and enable large-scale manufacturing. To date, both successful and unsuccessful results have been reported in clinical trials. These trials provide important information on factors such as toxicity, administration dose tolerated, and optimized vaccination strategy. This review highlights major viral vectors that are the best candidates for clinical use. Vaccines 2014-07-29 2 3 Review 10.3390/vaccines2030624 624 641 2076-393X 2014-07-29 doi: 10.3390/vaccines2030624 Takehiro Ura Kenji Okuda Masaru Shimada http://www.mdpi.com/2076-393X/2/3/601 Intracellular neurofibrillary tangles and extracellular senile plaques are potential targets for active and passive immunotherapies. In this study we used the transgenic mouse model P301S for active immunizations with peptide vaccines composed of a double phosphorylated tau neoepitope (pSer202/pThr205, pThr212/pSer214, pThr231/pSer235) and an immunomodulatory T cell epitope from the tetanus toxin or tuberculosis antigen Ag85B. Importantly, the designed vaccine combining Alzheimer's disease (AD) specific B cell epitopes with foreign (bacterial) T cell epitopes induced fast immune responses with high IgG1 titers after prophylactic immunization that subsequently decreased over the observation period. The effectiveness of the immunization was surveyed by evaluating the animal behavior, as well as the pathology in the brain by biochemical and histochemical techniques. Immunized mice clearly lived longer with reduced paralysis than placebo-treated mice. Additionally, they performed significantly better in rotarod and beam walk tests at the age of 20 weeks, indicating that the disease development was slowed down. Forty-eight weeks old vaccinated mice passed the beam walk test significantly better than control animals, which together with the increased survival rates undoubtedly prove the treatment effect. In conclusion, the data provide strong evidence that active immune therapies can reduce toxic effects of deposits formed in AD. Vaccines 2014-07-29 2 3 Article 10.3390/vaccines2030601 601 623 2076-393X 2014-07-29 doi: 10.3390/vaccines2030601 Monique Richter Agneta Mewes Manuela Fritsch Ute Krügel Ralf Hoffmann David Singer http://www.mdpi.com/2076-393X/2/3/581 Viral vectors are promising tools for vaccination strategies and immunotherapies. However, CD8+ T cell responses against pathogen-derived epitopes are usually limited to dominant epitopes and antibody responses to recombinant encoded antigens (Ags) are mostly weak. We have previously demonstrated that the timing of viral Ag expression in infected professional Ag-presenting cells strongly shapes the epitope immunodominance hierarchy. T cells recognizing determinants derived from late viral proteins have a clear disadvantage to proliferate during secondary responses. In this work we evaluate the effect of overexpressing the recombinant Ag using the modified vaccinia virus early/late promoter H5 (mPH5). Although the Ag-expression from the natural promoter 7.5 (P7.5) and the mPH5 seemed similar, detailed analysis showed that mPH5 not only induces higher expression levels than P7.5 during early phase of infection, but also Ag turnover is enhanced. The strong overexpression during the early phase leads to broader CD8 T cell responses, while preserving the priming efficiency of stable Ags. Moreover, the increase in Ag-secretion favors the induction of strong antibody responses. Our findings provide the rationale to develop new strategies for fine-tuning the responses elicited by recombinant modified vaccinia virus Ankara by using selected promoters to improve the performance of this viral vector. Vaccines 2014-07-22 2 3 Article 10.3390/vaccines2030581 581 600 2076-393X 2014-07-22 doi: 10.3390/vaccines2030581 Pablo Becker Miriam Nörder Sebastian Weissmann Ronny Ljapoci Volker Erfle Ingo Drexler Carlos Guzmán http://www.mdpi.com/2076-393X/2/3/563 Therapeutic HIV immunization is intended to induce new HIV-specific cellular immune responses and to reduce viral load, possibly permitting extended periods without antiretroviral drugs. A multigene, multi-subtype A, B, C HIV-DNA vaccine (HIVIS) has been used in clinical trials in both children and adults with the aim of improving and broadening the infected individuals' immune responses. Despite the different country locations, different regimens and the necessary variations in assays performed, this is, to our knowledge, the first attempt to compare children's and adults' responses to a particular HIV vaccine. Ten vertically HIV-infected children aged 4–16 years were immunized during antiretroviral therapy (ART). Another ten children were blindly recruited as controls. Both groups continued their antiretroviral treatment during and after vaccinations. Twelve chronically HIV-infected adults were vaccinated, followed by repeated structured therapy interruptions (STI) of their antiretroviral treatment. The adult group included four controls, receiving placebo vaccinations. The HIV-DNA vaccine was generally well tolerated, and no serious adverse events were registered in any group. In the HIV-infected children, an increased specific immune response to Gag and RT proteins was detected by antigen-specific lymphoproliferation. Moreover, the frequency of HIV-specific CD8+ T-cell lymphocytes releasing perforin was significantly higher in the vaccinees than the controls. In the HIV-infected adults, increased CD8+ T-cell responses to Gag, RT and viral protease peptides were detected. No augmentation of HIV-specific lymphoproliferative responses were detected in adults after vaccination. In conclusion, the HIV-DNA vaccine can elicit new HIV-specific cellular immune responses, particularly to Gag antigens, in both HIV-infected children and adults. Vaccinated children mounted transient new HIV-specific immune responses, including both CD4+ T-cell lymphoproliferation and late CD8+ T-cell responses. In the adult cohort, primarily CD8+ T-cell responses related to MHC class I alleles were noted. However, no clinical benefits with respect to viral load reduction were ascribable to the vaccinations alone. No severe adverse effects related to the vaccine were found in either cohort, and no virological failures or drug resistances were detected. Vaccines 2014-07-17 2 3 Article 10.3390/vaccines2030563 563 580 2076-393X 2014-07-17 doi: 10.3390/vaccines2030563 Paolo Palma Lindvi Gudmundsdotter Andrea Finocchi Lars Eriksson Nadia Mora Veronica Santilli Angela Aquilani Emma Manno Paola Zangari Maria Romiti Carla Montesano Alba Grifoni Andreas Brave Karl Ljungberg Pontus Blomberg Stefania Bernardi Eric Sandström Bo Hejdeman Paolo Rossi Britta Wahren http://www.mdpi.com/2076-393X/2/3/549 Synthetic tumor vaccines have been proven to be promising for cancer immunotherapy. However, the limitation of the specificity and efficiency of the synthetic tumor vaccines need further improvements. To overcome these difficulties, additional tumor-associated targets need to be identified, and optimized structural designs of vaccines need to be elaborated. In this review, we summarized the main strategies pursued in the design of synthetic tumor vaccines, such as multi-component, multivalency, antigen modification and other possible ways to improve the efficiency of synthetic tumor vaccines. Vaccines 2014-07-15 2 3 Review 10.3390/vaccines2030549 549 562 2076-393X 2014-07-15 doi: 10.3390/vaccines2030549 Zhi-Hua Huang Zhan-Yi Sun Yue Gao Pu-Guang Chen Yan-Fang Liu Yong-Xiang Chen Yan-Mei Li http://www.mdpi.com/2076-393X/2/3/537 While T cells recognise the complex of peptide and major histocompatibility complex (MHC) at the cell surface, changes in the dose and/or structure of the peptide component can have profound effects on T cell activation and function. In addition, the repertoire of T cells capable of responding to any given peptide is variable, but broader than a single clone. Consequently, peptide parameters that affect the interaction between T cells and peptide/MHC have been shown to select particular T cell clones for expansion and this impacts on clearance of disease. T cells with high functional avidity are selected on low doses of peptide, while low avidity T cells are favoured in high peptide concentrations. Altering the structure of the peptide ligand can also influence the selection and function of peptide-specific T cell clones. In this review, we will explore the evidence that the choice of peptide dose or the structure of the peptide are critical parameters in an effective vaccine designed to activate T cells. Vaccines 2014-07-02 2 3 Review 10.3390/vaccines2030537 537 548 2076-393X 2014-07-02 doi: 10.3390/vaccines2030537 Graham Leggatt http://www.mdpi.com/2076-393X/2/3/515 Conventional vaccine strategies have been highly efficacious for several decades in reducing mortality and morbidity due to infectious diseases. The bane of conventional vaccines, such as those that include whole organisms or large proteins, appear to be the inclusion of unnecessary antigenic load that, not only contributes little to the protective immune response, but complicates the situation by inducing allergenic and/or reactogenic responses. Peptide vaccines are an attractive alternative strategy that relies on usage of short peptide fragments to engineer the induction of highly targeted immune responses, consequently avoiding allergenic and/or reactogenic sequences. Conversely, peptide vaccines used in isolation are often weakly immunogenic and require particulate carriers for delivery and adjuvanting. In this article, we discuss the specific advantages and considerations in targeted induction of immune responses by peptide vaccines and progresses in the development of such vaccines against various diseases. Additionally, we also discuss the development of particulate carrier strategies and the inherent challenges with regard to safety when combining such technologies with peptide vaccines. Vaccines 2014-07-02 2 3 Review 10.3390/vaccines2030515 515 536 2076-393X 2014-07-02 doi: 10.3390/vaccines2030515 Weidang Li Medha Joshi Smita Singhania Kyle Ramsey Ashlesh Murthy http://www.mdpi.com/2076-393X/2/3/500 The potent adjuvant activity of the novel adjuvant, poly[di(sodiumcarboxylatoethylphenoxy)phosphazene] (PCEP), with various antigens has been reported previously. However, very little is known about its mechanisms of action. We have recently reported that intramuscular injection of PCEP induces NLRP3, an inflammasome receptor gene, and inflammatory cytokines, including IL-1β and IL-18, in mouse muscle tissue. Caspase-1 is required for the processing of pro-forms of IL-1β and IL-18 into mature forms and is a critical constituent of the NLRP3 inflammasome. Hence, in the present study, we investigated the role of caspase-1 in the secretion of IL-1β and IL-18 in PCEP-stimulated splenic dendritic cells (DCs). Caspase inhibitor YVAD-fmk-treated splenic DCs showed significantly reduced IL-1β and IL-18 secretion in response to PCEP stimulation. Further, PCEP had no effect on the expression of MHC class II or co-stimulatory molecules, CD86 and CD40, suggesting that PCEP does not induce DC maturation. However, PCEP directly activated B-cells to induce significant production of IgM. In addition, PCEP+ovalbumin (OVA) immunized mice showed significantly increased production of antigen-specific IFN-γ by CD4+ and CD8+ T-cells. We conclude that PCEP activates innate immunity, leading to increased antigen-specific T-cell responses. Vaccines 2014-06-26 2 3 Article 10.3390/vaccines2030500 500 514 2076-393X 2014-06-26 doi: 10.3390/vaccines2030500 Sunita Awate Nelson Eng Volker Gerdts Lorne Babiuk George Mutwiri http://www.mdpi.com/2076-393X/2/2/463 Novel efficient vaccines are needed to control tuberculosis (TB), a major cause of morbidity and mortality worldwide. Several TB vaccine candidates are currently in clinical and preclinical development. They fall into two categories, the one of candidates designed as a replacement of the Bacille Calmette Guérin (BCG) to be administered to infants and the one of sub-unit vaccines designed as booster vaccines. The latter are designed as vaccines that will be administered to individuals already vaccinated with BCG (or in the future with a BCG replacement vaccine). In this review we provide up to date information on novel tuberculosis (TB) vaccines in development focusing on the risk assessment of candidates composed of genetically modified organisms (GMO) which are currently evaluated in clinical trials. Indeed, these vaccines administered to volunteers raise biosafety concerns with respect to human health and the environment that need to be assessed and managed. Vaccines 2014-06-16 2 2 Review 10.3390/vaccines2020463 463 499 2076-393X 2014-06-16 doi: 10.3390/vaccines2020463 Amaya Leunda Aline Baldo Martine Goossens Kris Huygen Philippe Herman Marta Romano http://www.mdpi.com/2076-393X/2/2/422 High-risk types of human papillomavirus (HPV) cause over 500,000 cervical, anogenital and oropharyngeal cancer cases per year. The transforming potential of HPVs is mediated by viral oncoproteins. These are essential for the induction and maintenance of the malignant phenotype. Thus, HPV-mediated malignancies pose the unique opportunity in cancer vaccination to target immunologically foreign epitopes. Therapeutic HPV vaccination is therefore an ideal scenario for proof-of-concept studies of cancer immunotherapy. This is reflected by the fact that a multitude of approaches has been utilized in therapeutic HPV vaccination design: protein and peptide vaccination, DNA vaccination, nanoparticle- and cell-based vaccines, and live viral and bacterial vectors. This review provides a comprehensive overview of completed and ongoing clinical trials in therapeutic HPV vaccination (summarized in tables), and also highlights selected promising preclinical studies. Special emphasis is given to adjuvant science and the potential impact of novel developments in vaccinology research, such as combination therapies to overcome tumor immune suppression, the use of novel materials and mouse models, as well as systems vaccinology and immunogenetics approaches. Vaccines 2014-06-13 2 2 Review 10.3390/vaccines2020422 422 462 2076-393X 2014-06-13 doi: 10.3390/vaccines2020422 Hadeel Khallouf Agnieszka Grabowska Angelika Riemer http://www.mdpi.com/2076-393X/2/2/397 The ability to predict the conditions under which antibodies protect against viral infection would transform our approach to vaccine development. A more complete understanding is needed of antibody protection against lentivirus infection, as well as the role of mutation in resistance to an antibody vaccine. Recently, an example of antibody-mediated vaccine protection has been shown via passive transfer of neutralizing antibodies before equine infectious anemia virus (EIAV) infection of horses with severe combined immunodeficiency (SCID). Viral dynamic modeling of antibody protection from EIAV infection in SCID horses may lead to insights into the mechanisms of control of infection by antibody vaccination. In this work, such a model is constructed in conjunction with data from EIAV infection of SCID horses to gain insights into multiple strain competition in the presence of antibody control. Conditions are determined under which wild-type infection is eradicated with the antibody vaccine. In addition, a three-strain competition model is considered in which a second mutant strain may coexist with the first mutant strain. The conditions that permit viral escape by the mutant strains are determined, as are the effects of variation in the model parameters. This work extends the current understanding of competition and antibody control in lentiviral infection, which may provide insights into the development of vaccines that stimulate the immune system to control infection effectively. Vaccines 2014-05-27 2 2 Article 10.3390/vaccines2020397 397 421 2076-393X 2014-05-27 doi: 10.3390/vaccines2020397 Elissa Schwartz Robert Smith? http://www.mdpi.com/2076-393X/2/2/380 Outer membrane proteins, such as glyceraldehyde-3-phosphate dehydrogenase (GAPDH), are considered immunodominant antigens for eliciting protective immunity against Vibrio harveyi, the main etiological agent of vibriosis in fish. Cationic antimicrobial peptides (AMPs), such as pleurocidin (PLE), play important roles in activating and recruiting immune cells, thereby contributing to subsequent innate and adaptive immune responses. In the present study, we aimed to use PLE peptide as a potent adjuvant to improve the immunogenicity of V. harveyi recombinant GAPDH (rGAPDH). In order to prepare a controlled-release vaccine, PLE peptide and rGAPDH protein were simultaneously encapsulated into polymeric microparticles made from the biodegradable poly(lactide-co-glycolide) (PLG) polymer. The resulting PLG-encapsulated PLE plus rGAPDH (PLG-PLE/rGAPDH) microparticles, 3.21–6.27 μm in diameter, showed 72%–83% entrapment efficiency and durably released both PLE and rGAPDH for a long 30-day period. Following peritoneal immunization in grouper (Epinephelus coioides), PLG-PLE/rGAPDH microparticles resulted in significantly higher (p < 0.05, nested design) long-lasting GAPDH-specific immunity (serum titers and lymphocyte proliferation) than PLG-encapsulated rGAPDH (PLG-rGAPDH) microparticles. After an experimental challenge of V. harveyi, PLG-PLE/rGAPDH microparticles conferred a high survival rate (85%), which was significantly higher (p < 0.05, chi-square test) than that induced by PLG-rGAPDH microparticles (67%). In conclusion, PLE peptide exhibits an efficacious adjuvant effect to elicit not only improved immunity, but also enhanced protection against V. harveyi in grouper induced by rGAPDH protein encapsulated in PLG microparticles. Vaccines 2014-05-14 2 2 Article 10.3390/vaccines2020380 380 396 2076-393X 2014-05-14 doi: 10.3390/vaccines2020380 Shu-Chun Chuang Wan-Ling Huang Sau-Wei Kau Yun-Pei Yang Chung-Da Yang http://www.mdpi.com/2076-393X/2/2/354 Inefficient DNA delivery methods and low expression of plasmid DNA have been major obstacles for the use of plasmid DNA as vaccine for HIV/AIDS. This review describes successful efforts to improve DNA vaccine methodology over the past ~30 years. DNA vaccination, either alone or in combination with other methods, has the potential to be a rapid, safe, and effective vaccine platform against AIDS. Recent clinical trials suggest the feasibility of its translation to the clinic. Vaccines 2014-05-14 2 2 Review 10.3390/vaccines2020354 354 379 2076-393X 2014-05-14 doi: 10.3390/vaccines2020354 Barbara Felber Antonio Valentin Margherita Rosati Cristina Bergamaschi George Pavlakis http://www.mdpi.com/2076-393X/2/2/323 Vaccine efficacy is optimized by addition of immune adjuvants. However, although adjuvants have been used for over a century, to date, only few adjuvants are approved for human use, mostly aimed at improving vaccine efficacy and antigen-specific protective antibody production. The mechanism of action of immune adjuvants is diverse, depending on their chemical and molecular nature, ranging from non-specific effects (i.e., antigen depot at the immunization site) to specific activation of immune cells leading to improved host innate and adaptive responses. Although the detailed molecular mechanism of action of many adjuvants is still elusive, the discovery of Toll-like receptors (TLRs) has provided new critical information on immunostimulatory effect of numerous bacterial components that engage TLRs. These ligands have been shown to improve both the quality and the quantity of host adaptive immune responses when used in vaccine formulations targeted to infectious diseases and cancer that require both humoral and cell-mediated immunity. The potential of such TLR adjuvants in improving the design and the outcomes of several vaccines is continuously evolving, as new agonists are discovered and tested in experimental and clinical models of vaccination. In this review, a summary of the recent progress in development of TLR adjuvants is presented. Vaccines 2014-04-25 2 2 Review 10.3390/vaccines2020323 323 353 2076-393X 2014-04-25 doi: 10.3390/vaccines2020323 Deana Toussi Paola Massari http://www.mdpi.com/2076-393X/2/2/297 Adjuvants are crucial components of vaccines. They significantly improve vaccine efficacy by modulating, enhancing, or extending the immune response and at the same time reducing the amount of antigen needed. In contrast to previously licensed adjuvants, current successful adjuvant formulations often consist of several molecules, that when combined, act synergistically by activating a variety of immune mechanisms. These "combination adjuvants" are already registered with several vaccines, both in humans and animals, and novel combination adjuvants are in the pipeline. With improved knowledge of the type of immune responses needed to successfully induce disease protection by vaccination, combination adjuvants are particularly suited to not only enhance, but also direct the immune responses desired to be either Th1-, Th2- or Th17-biased. Indeed, in view of the variety of disease and population targets for vaccine development, a panel of adjuvants will be needed to address different disease targets and populations. Here, we will review well-known and new combination adjuvants already licensed or currently in development—including ISCOMs, liposomes, Adjuvant Systems Montanides, and triple adjuvant combinations—and summarize their performance in preclinical and clinical trials. Several of these combination adjuvants are promising having promoted improved and balanced immune responses. Vaccines 2014-04-14 2 2 Review 10.3390/vaccines2020297 297 322 2076-393X 2014-04-14 doi: 10.3390/vaccines2020297 Benoît Levast Sunita Awate Lorne Babiuk George Mutwiri Volker Gerdts Sylvia van Drunen Littel-van den Hurk http://www.mdpi.com/2076-393X/2/2/252 The mechanism by which vaccine adjuvants enhance immune responses has historically been considered to be the creation of an antigen depot. From here, the antigen is slowly released and provided to immune cells over an extended period of time. This "depot" was formed by associating the antigen with substances able to persist at the injection site, such as aluminum salts or emulsions. The identification of Pathogen-Associated Molecular Patterns (PAMPs) has greatly advanced our understanding of how adjuvants work beyond the simple concept of extended antigen release and has accelerated the development of novel adjuvants. This review focuses on the mode of action of different adjuvant classes in regards to the stimulation of specific immune cell subsets, the biasing of immune responses towards cellular or humoral immune response, the ability to mediate epitope spreading and the induction of persistent immunological memory. A better understanding of how particular adjuvants mediate their biological effects will eventually allow them to be selected for specific vaccines in a targeted and rational manner. Vaccines 2014-04-10 2 2 Review 10.3390/vaccines2020252 252 296 2076-393X 2014-04-10 doi: 10.3390/vaccines2020252 Elke Bergmann-Leitner Wolfgang Leitner http://www.mdpi.com/2076-393X/2/2/228 Most commercial vaccines offered to the aquaculture industry include inactivated antigens (Ag) formulated in oil adjuvants. Safety concerns are related to the use of oil adjuvants in multivalent vaccines for fish, since adverse side effects (e.g., adhesions) can appear. Therefore, there is a request for vaccine formulations for which protection will be maintained or improved, while the risk of side effects is reduced. Here, by using an inactivated salmonid alphavirus (SAV) as the test Ag, the combined use of two Toll-like receptor (TLR) ligand adjuvants, CpG oligonucleotides (ODNs) and poly I:C, as well as a genetic adjuvant consisting of a DNA plasmid vector expressing the viral haemorrhagic septicaemia virus (VHSV) glycoprotein (G) was explored. VHSV-G DNA vaccine was intramuscularly injected in combination with intraperitoneal injection of either SAV Ag alone or combined with the oil adjuvant, Montanide ISA763, or the CpG/polyI:C combo. Adjuvant formulations were evaluated for their ability to boost immune responses and induce protection against SAV in Atlantic salmon, following cohabitation challenge. It was observed that CpG/polyI:C-based formulations generated the highest neutralizing antibody titres (nAbs) before challenge, which endured post challenge. nAb responses for VHSV G-DNA- and oil-adjuvanted formulations were marginal compared to the CpG/poly I:C treatment. Interestingly, heat-inactivated sera showed reduced nAb titres compared to their non-heated counterparts, which suggests a role of complement-mediated neutralization against SAV. Consistently elevated levels of innate antiviral immune genes in the CpG/polyI:C injected groups suggested a role of IFN-mediated responses. Co-delivery of the VHSV-G DNA construct with either CpG/polyI:C or oil-adjuvanted SAV vaccine generated higher CD4 responses in head kidney at 48 h compared to injection of this vector or SAV Ag alone. The results demonstrate that a combination of pattern recognizing receptor (PRR) ligands, such as CpG/polyI:C, increases both adaptive and innate responses and represents a promising adjuvant strategy for enhancing the protection of future viral vaccines. Vaccines 2014-03-25 2 2 Article 10.3390/vaccines2020228 228 251 2076-393X 2014-03-25 doi: 10.3390/vaccines2020228 Hanna Thim Stéphane Villoing Marian McLoughlin Karen Christie Søren Grove Petter Frost Jorunn Jørgensen http://www.mdpi.com/2076-393X/2/2/216 Modulation of the cytokine milieu is one approach for vaccine development. However, therapy with pro-inflammatory cytokines, such as IL-12, is limited in practice due to adverse systemic effects. Spatially-restricted gene expression circumvents this problem by enabling localized amplification. Intracellular co-delivery of gold nanorods (AuNR) and a heat shock protein 70 (HSP70) promoter-driven expression vector enables gene expression in response to near infrared (NIR) light. AuNRs absorb the light, convert it into heat and thereby stimulate photothermal expression of the cytokine. As proof-of-concept, human HeLa and murine B16 cancer cells were transfected with a HSP70-Enhanced Green Fluorescent Protein (EGFP) plasmid and polyethylenimine (PEI)-conjugated AuNRs. Exposure to either 42 °C heat-shock or NIR light induced significant expression of the reporter gene. In vivo NIR driven expression of the reporter gene was confirmed at 6 and 24 h in mice bearing B16 melanoma tumors using in vivo imaging and flow-cytometric analysis. Overall, we demonstrate a novel opportunity for site-directed, heat-inducible expression of a gene based upon the NIR-absorbing properties of AuNRs and a HSP70 promoter-driven expression vector. Vaccines 2014-03-25 2 2 Article 10.3390/vaccines2020216 216 227 2076-393X 2014-03-25 doi: 10.3390/vaccines2020216 Helen Andersson Yoo-Shin Kim Brian O'Neill Zheng-Zheng Shi Rita Serda http://www.mdpi.com/2076-393X/2/2/196 DNA vaccine-induced immunity can be enhanced by the co-delivery of synthetic gene-encoding molecular adjuvants. Many of these adjuvants have included cytokines, chemokines or co-stimulatory molecules that have been demonstrated to enhance vaccine-induced immunity by increasing the magnitude or type of immune responses and/or protective efficacy. In this way, through the use of adjuvants, immune responses can be highly customizable and functionally tailored for optimal efficacy against pathogen specific (i.e., infectious agent) or non-pathogen (i.e., cancer) antigens. In the novel study presented here, we examined the use of cellular transcription factors as molecular adjuvants. Specifically the co-delivery of (a) RelA, a subunit of the NF-κB transcription complex or (b) T-bet, a Th1-specific T box transcription factor, along with a prototypical DNA vaccine expressing HIV-1 proteins was evaluated. As well, all of the vaccines and adjuvants were administered to mice using in vivo electroporation (EP), a technology demonstrated to dramatically increase plasmid DNA transfection and subsequent transgene expression with concomitant enhancement of vaccine induced immune responses. As such, this study demonstrated that co-delivery of either adjuvant resulted in enhanced T and B cell responses, specifically characterized by increased T cell numbers, IFN-γ production, as well as enhanced antibody responses. This study demonstrates the use of cellular transcription factors as adjuvants for enhancing DNA vaccine-induced immunity. Vaccines 2014-03-25 2 2 Article 10.3390/vaccines2020196 196 215 2076-393X 2014-03-25 doi: 10.3390/vaccines2020196 Devon Shedlock Colleen Tingey Lavanya Mahadevan Natalie Hutnick Emma Reuschel Sagar Kudchodkar Seleeke Flingai Jenny Yan Joseph Kim Kenneth Ugen David Weiner Kar Muthumani http://www.mdpi.com/2076-393X/2/1/181 The attenuated live M. bovis Bacille-Calmette-Guérin (BCG) is still the sole vaccine used against tuberculosis, but confers only variable efficacy against adult pulmonary tuberculosis (TB). Though no clear explanation for this limited efficacy has been given, different hypotheses have been advanced, such as the waning of memory T-cell responses, a reduced antigenic repertoire and the inability to induce effective CD8+ T-cell responses, which are known to be essential for latent tuberculosis control. In this study, a new BCG-based vaccination protocol was studied, in which BCG was formulated in combination with a plasmid DNA vaccine. As BCG is routinely administered to neonates, we have evaluated a more realistic approach of a simultaneous intradermal coadministration of BCG with pDNA encoding the prototype antigen, PPE44. Strongly increased T- and B-cell responses were observed with this protocol in C57BL/6 mice when compared to the administration of only BCG or in combination with an empty pDNA vector, as measured by Th1-type spleen cell cytokine secretion, specific IgG antibodies, as well as specific IFN-γ producing/cytolytic-CD8+ T-cells. Moreover, we observed a bystander activation induced by the coding plasmid, resulting in increased immune responses against other non-plasmid encoded, but BCG-expressed, antigens. In all, these results provide a proof of concept for a new TB vaccine, based on a BCG-plasmid DNA combination. Vaccines 2014-03-05 2 1 Article 10.3390/vaccines2010181 181 195 2076-393X 2014-03-05 doi: 10.3390/vaccines2010181 Nicolas Bruffaerts Marta Romano Olivier Denis Fabienne Jurion Kris Huygen http://www.mdpi.com/2076-393X/2/1/179 The editors of Vaccines would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2013. [...] Vaccines 2014-02-28 2 1 Editorial 10.3390/vaccines2010179 179 180 2076-393X 2014-02-28 doi: 10.3390/vaccines2010179 Vaccines Editorial Office http://www.mdpi.com/2076-393X/2/1/160 Since the initial proof-of-concept studies examining the ability of antigen-encoded plasmid DNA to serve as an immunogen, DNA vaccines have evolved as a clinically safe and effective platform for priming HIV-specific cellular and humoral responses in heterologous "prime-boost" vaccination regimens. Direct injection of plasmid DNA into the muscle induces T- and B-cell responses against foreign antigens. However, the insufficient magnitude of this response has led to the development of approaches for enhancing the immunogenicity of DNA vaccines. The last two decades have seen significant progress in the DNA-based vaccine platform with optimized plasmid constructs, improved delivery methods, such as electroporation, the use of molecular adjuvants and novel strategies combining DNA with viral vectors and subunit proteins. These innovations are paving the way for the clinical application of DNA-based HIV vaccines. Here, we review preclinical studies on the DNA-prime/modified vaccinia Ankara (MVA)-boost vaccine modality for HIV. There is a great deal of interest in enhancing the immunogenicity of DNA by engineering DNA vaccines to co-express immune modulatory adjuvants. Some of these adjuvants have demonstrated encouraging results in preclinical and clinical studies, and these data will be examined, as well. Vaccines 2014-02-28 2 1 Review 10.3390/vaccines2010160 160 178 2076-393X 2014-02-28 doi: 10.3390/vaccines2010160 Smita Iyer Rama Amara http://www.mdpi.com/2076-393X/2/1/138 DNA vaccination has been studied in the last 20 years for HIV vaccine research. Significant experience has been accumulated in vector design, antigen optimization, delivery approaches and the use of DNA immunization as part of a prime-boost HIV vaccination strategy. Key historical data and future outlook are presented. With better understanding on the potential of DNA immunization and recent progress in HIV vaccine research, it is anticipated that DNA immunization will play a more significant role in the future of HIV vaccine development. Vaccines 2014-02-25 2 1 Review 10.3390/vaccines2010138 138 159 2076-393X 2014-02-25 doi: 10.3390/vaccines2010138 Yuxin Chen Shixia Wang Shan Lu http://www.mdpi.com/2076-393X/2/1/129 The current study examined and compared the willingness of young Black men who have sex with men (YBMSM) to accept pre-exposure prophylaxis (PrEP), adult male circumcision, and condoms for reducing their risk of HIV acquisition. The majority (67%) reported unprotected receptive anal sex in the last six months. About three-quarters (71%) would accept using PrEP if it was 100% effective. Cost influenced PrEP acceptance with 19% indicating acceptance at $100 per month co-pay. Of those not circumcised, 50% indicated willingness if circumcision was 100% effective. Acceptance of circumcision decreased markedly to 17% with co-pays of $100. About 73% of men were willing to use condoms if they were 100% effective and 50% indicated a willingness at the cost of $10 per month. The findings suggest that condom use promotion strategies should remain at the forefront of public health efforts to control HIV incidence among YBMSM. Vaccines 2014-02-18 2 1 Article 10.3390/vaccines2010129 129 137 2076-393X 2014-02-18 doi: 10.3390/vaccines2010129 Richard Crosby Angelica Geter Ralph DiClemente Laura Salazar http://www.mdpi.com/2076-393X/2/1/112 Seven-valent pneumococcal conjugate vaccine (PCV7) introduction and routine pediatric use has substantially reduced the burden of Streptococcus pneumoniae disease worldwide. However, a significant amount of disease burden, due to serotypes not contained in PCV7, still exists globally. A newly recognized serotype, 6C, was until recently, identified and reported as serotype 6A. This review summarizes the serotype epidemiology of pneumococcal disease pre- and post-introduction of PCV7, available post-marketing surveillance data following the introduction of higher valency pneumococcal vaccines (PCV10, PCV13) and future prospects for the development of new pneumococcal vaccines. Vaccines 2014-02-14 2 1 Review 10.3390/vaccines2010112 112 128 2076-393X 2014-02-14 doi: 10.3390/vaccines2010112 Lucia Lee Xin-Xing Gu Moon Nahm http://www.mdpi.com/2076-393X/2/1/107 In late October 2011, the Monroe County Department of Public Health (MCDPH) was notified of a suspected case of meningitis in a 9-year old girl from Monroe County, NY. Laboratory testing at the New York State Department of Health (NYSDOH) Wadsworth Center confirmed the identification of Haemophilus influenzae serotype e (Hie) isolated from the patient's cerebrospinal fluid (CSF) using real-time polymerase chain reaction (RT-PCR). The universal immunization of infants with conjugate H. influenzae type b (Hib) vaccine has significantly reduced the incidence of invasive Hib disease, including meningitis, one of the most serious complications for infected children. Not surprisingly, as the epidemiology of invasive H. influenzae continues to change, non-Hib serotypes will likely become more common. The findings reported here underscore the importance for clinicians, public health officials, and laboratory staff to consider non-Hib pathogens in pediatric cases of meningitis, especially when initial investigations are inconclusive. Vaccines 2014-02-13 2 1 Case Report 10.3390/vaccines2010107 107 111 2076-393X 2014-02-13 doi: 10.3390/vaccines2010107 Byron Kennedy Anita Weimer Brenden Bedard Jennifer Nayak Drew Sacheli John Ricci Donna Meyer Donna Hubbard http://www.mdpi.com/2076-393X/2/1/89 The advantages of genetic immunization of the new vaccine using plasmid DNAs are multifold. For example, it is easy to generate plasmid DNAs, increase their dose during the manufacturing process, and sterilize them. Furthermore, they can be stored for a long period of time upon stabilization, and their protein encoding sequences can be easily modified by employing various DNA-manipulation techniques. Although DNA vaccinations strongly increase Th1-mediated immune responses in animals, several problems persist. One is about their weak immunogenicity in humans. To overcome this problem, various genetic adjuvants, electroporation, and prime-boost methods have been developed preclinically, which are reviewed here. Vaccines 2014-01-13 2 1 Review 10.3390/vaccines2010089 89 106 2076-393X 2014-01-13 doi: 10.3390/vaccines2010089 Kenji Okuda Yoshiyuki Wada Masaru Shimada http://www.mdpi.com/2076-393X/2/1/49 Streptococcus pneumoniae still causes severe morbidity and mortality worldwide, especially in young children and the elderly. Much effort has been dedicated to developing protein-based universal vaccines to conquer the current shortcomings of capsular vaccines and capsular conjugate vaccines, such as serotype replacement, limited coverage and high costs. A recombinant live vector vaccine delivering protective antigens is a promising way to achieve this goal. In this review, we discuss the researches using live recombinant vaccines, mainly live attenuated Salmonella and lactic acid bacteria, to deliver pneumococcal antigens. We also discuss both the limitations and the future of these vaccines. Vaccines 2014-01-07 2 1 Review 10.3390/vaccines2010049 49 88 2076-393X 2014-01-07 doi: 10.3390/vaccines2010049 Shifeng Wang Roy Curtiss III http://www.mdpi.com/2076-393X/2/1/36 Recent studies indicate that DNA immunization is powerful in eliciting antigen-specific antibody responses in both animal and human studies. However, there is limited information on the mechanism of this effect. In particular, it is not known whether DNA immunization can also enhance the development of antigen-specific B cell development. In this report, a pilot study was conducted using plague LcrV immunogen as a model system to determine whether DNA immunization is able to enhance LcrV-specific B cell development in mice. Plague is an acute and often fatal infectious disease caused by Yersinia pestis (Y. pestis). Humoral immune responses provide critical protective immunity against plague. Previously, we demonstrated that a DNA vaccine expressing LcrV antigen can protect mice from lethal mucosal challenge. In the current study, we further evaluated whether the use of a DNA priming immunization is able to enhance the immunogenicity of a recombinant LcrV protein vaccine, and in particular, the development of LcrV-specific B cells. Our data indicate that DNA immunization was able to elicit high-level LcrV antibody responses when used alone or as part of a prime-boost immunization approach. Most significantly, DNA immunization was also able to increase the levels of LcrV-specific B cell development. The finding that DNA immunization can enhance antigen-specific B cell responses is highly significant and will help guide similar studies in other model antigen systems. Vaccines 2013-12-27 2 1 Article 10.3390/vaccines2010036 36 48 2076-393X 2013-12-27 doi: 10.3390/vaccines2010036 Wei Li Shixia Wang Shan Lu http://www.mdpi.com/2076-393X/2/1/15 Interrogating immune correlates of infection risk for efficacious and non-efficacious HIV-1 vaccine clinical trials have provided hypotheses regarding the mechanisms of induction of protective immunity to HIV-1. To date, there have been six HIV-1 vaccine efficacy trials (VAX003, Vaxgen, Inc., San Francisco, CA, USA), VAX004 (Vaxgen, Inc.), HIV-1 Vaccine Trials Network (HVTN) 502 (Step), HVTN 503 (Phambili), RV144 (sponsored by the U.S. Military HIV Research Program, MHRP) and HVTN 505). Cellular, humoral, host genetic and virus sieve analyses of these human clinical trials each can provide information that may point to potentially protective mechanisms for vaccine-induced immunity. Critical to staying on the path toward development of an efficacious vaccine is utilizing information from previous human and non-human primate studies in concert with new discoveries of basic HIV-1 host-virus interactions. One way that past discoveries from correlate analyses can lead to novel inventions or new pathways toward vaccine efficacy is to examine the intersections where different components of the correlate analyses overlap (e.g., virus sieve analysis combined with humoral correlates) that can point to mechanistic hypotheses. Additionally, differences in durability among vaccine-induced T- and B-cell responses indicate that time post-vaccination is an important variable. Thus, understanding the nature of protective responses, the degree to which such responses have, or have not, as yet, been induced by previous vaccine trials and the design of strategies to induce durable T- and B-cell responses are critical to the development of a protective HIV-1 vaccine. Vaccines 2013-12-27 2 1 Review 10.3390/vaccines2010015 15 35 2076-393X 2013-12-27 doi: 10.3390/vaccines2010015 Georgia Tomaras Barton Haynes http://www.mdpi.com/2076-393X/2/1/1 In this brief review, we discuss immune tolerance as a factor that determines the magnitude and quality of serum antibody responses to HIV-1 infection and vaccination in the context of recent work. We propose that many conserved, neutralizing epitopes of HIV-1 are weakly immunogenic because they mimic host antigens. In consequence, B cells that strongly bind these determinants are removed by the physiological process of immune tolerance. This structural mimicry may represent a significant impediment to designing protective HIV-1 vaccines, but we note that several vaccine strategies may be able to mitigate this evolutionary adaptation of HIV and other microbial pathogens. Vaccines 2013-12-19 2 1 Review 10.3390/vaccines2010001 1 14 2076-393X 2013-12-19 doi: 10.3390/vaccines2010001 Garnett Kelsoe Laurent Verkoczy Barton Haynes http://www.mdpi.com/2076-393X/1/4/527 The success of cellular immunotherapies against cancer requires the generation of activated CD4+ and CD8+ T-cells. The type of T-cell response generated (e.g., Th1 or Th2) will determine the efficacy of the therapy, and it is generally assumed that a type-1 response is needed for optimal cancer treatment. IL-17 producing T-cells (Th17/Tc17) play an important role in autoimmune diseases, but their function in cancer is more controversial. While some studies have shown a pro-cancerous role for IL-17, other studies have shown an anti-tumor function. The induction of polarized T-cell responses can be regulated by dendritic cells (DCs). DCs are key regulators of the immune system with the ability to affect both innate and adaptive immune responses. These properties have led many researchers to study the use of ex vivo manipulated DCs for the treatment of various diseases, such as cancer and autoimmune diseases. While Th1/Tc1 cells are traditionally used for their potent anti-tumor responses, mounting evidence suggests Th17/Tc17 cells should be utilized by themselves or for the induction of optimal Th1 responses. It is therefore important to understand the factors involved in the induction of both type-1 and type-17 T-cell responses by DCs. Vaccines 2013-11-21 1 4 Review 10.3390/vaccines1040527 527 549 2076-393X 2013-11-21 doi: 10.3390/vaccines1040527 Julia Terhune Erik Berk Brian Czerniecki http://www.mdpi.com/2076-393X/1/4/513 When HIV was discovered and established as the cause of AIDS in 1983–1984, many people believed that a vaccine would be rapidly developed. However, 30 years have passed and we are still struggling to develop an elusive vaccine. In trying to achieve that goal, different scientific paradigms have been explored. Although major progress has been made in understanding the scientific basis for HIV vaccine development, efficacy trials have been critical in moving the field forward. Major lessons learned are: the development of an HIV vaccine is an extremely difficult challenge; the temptation of just following the fashion should be avoided; clinical trials are critical, especially large-scale efficacy trials; HIV vaccine research will require long-term commitment; and sustainable collaborations are needed to accelerate the development of an HIV vaccine. Concrete actions must be implemented with the sense of urgency imposed by the severity of the AIDS epidemic. Vaccines 2013-10-30 1 4 Article 10.3390/vaccines1040513 513 526 2076-393X 2013-10-30 doi: 10.3390/vaccines1040513 José Esparza http://www.mdpi.com/2076-393X/1/4/497 The HIV-1 envelope glycoprotein spike is the target of neutralizing antibody attack, and hence represents the only relevant viral antigen for antibody-based vaccine design. Various approaches have been attempted to recapitulate Env in membrane-anchored and soluble forms, and these will be discussed here in the context of recent successes and challenges still to be overcome. Vaccines 2013-10-28 1 4 Review 10.3390/vaccines1040497 497 512 2076-393X 2013-10-28 doi: 10.3390/vaccines1040497 Quentin Sattentau http://www.mdpi.com/2076-393X/1/4/481 Increasing numbers of HIV-infected individuals have access to potent antiretroviral drugs that control viral replication and decrease the risk of transmission. However, there is no cure for HIV and new strategies have to be developed to reach an eradication of the virus or a natural control of viral replication in the absence of drugs (functional cure). Therapeutic vaccines against HIV have been evaluated in many trials over the last 20 years and important knowledge has been gained from these trials. However, the major obstacle to HIV eradication is the persistence of latent proviral reservoirs. Different molecules are currently tested in ART-treated subjects to reactivate these latent reservoirs. Such anti-latency agents should be combined with a vaccination regimen in order to control or eradicate reactivated latently-infected cells. New in vitro assays should also be developed to assess the success of tested therapeutic vaccines by measuring the immune-mediated killing of replication-competent HIV reservoir cells. This review provides an overview of the current strategies to combine HIV vaccines with anti-latency agents that could act as adjuvant on the vaccine-induced immune response as well as new tools to assess the efficacy of these approaches. Vaccines 2013-10-28 1 4 Review 10.3390/vaccines1040481 481 496 2076-393X 2013-10-28 doi: 10.3390/vaccines1040481 Alessandra Noto Lydie Trautmann http://www.mdpi.com/2076-393X/1/4/463 In veterinary medicine, there have been different experiences with the plasmid DNA vaccination. In this area and with the hypothesis to demonstrate the effectiveness of different plasmids encoding porcine respiratory and reproductive syndrome (PRRS), five DNA vaccines against PRRS were evaluated for their innocuity and efficacy in pigs. Eighteen animals were divided into five groups which were injected with five (A, B, C, D, E) different DNA vaccines. Albeit, none of the proposed vaccines were able to protect the animals against PRRS virus. Only vaccines A and B were able to reduce the clinical signs of the infection. ELISA IgM were detected 30 days after the first vaccination in the pigs injected by Vaccine A or B. ELISA IgG were detected 90 days after the first vaccination in the pigs injected by Vaccine B or C. Neutralizing antibody were detected Post Challenge Days 61 (PCD) in all groups. In the pigs inoculated with Vaccine C, IFN-g were detected 90 days after first vaccination, and after challenge exposure they increased. In the other groups, the IFN-g were detected after challenge infection. Pigs injected with each of the vaccines A, B, C, D and E showed a significantly higher level of CD4−CD8+ lymphocytes (p < 0.001) after infection in comparison with their controls. Vaccines 2013-10-18 1 4 Article 10.3390/vaccines1040463 463 480 2076-393X 2013-10-18 doi: 10.3390/vaccines1040463 Stefano Petrini Giorgio Ramadori Riccardo Villa Paolo Borghetti Elena de Angelis Anna Cantoni Attilio Corradi Augusto Amici Maura Ferrari http://www.mdpi.com/2076-393X/1/4/444 We are witnessing a new era of immune-mediated cancer therapies and vaccine development. As the field of cancer vaccines advances into clinical trials, overcoming low immunogenicity is a limiting step in achieving full success of this therapeutic approach. Recent discoveries in the many biological roles of chemokines in tumor immunology allow their exploitation in enhancing recruitment of antigen presenting cells (APCs) and effector cells to appropriate anatomical sites. This knowledge, combined with advances in gene therapy and virology, allows researchers to employ chemokines as potential vaccine adjuvants. This review will focus on recent murine and human studies that use chemokines as therapeutic anti-cancer vaccine adjuvants. Vaccines 2013-10-16 1 4 Review 10.3390/vaccines1040444 444 462 2076-393X 2013-10-16 doi: 10.3390/vaccines1040444 Iuliana Bobanga Agne Petrosiute Alex Huang http://www.mdpi.com/2076-393X/1/4/415 Eliciting effective immune responses using non-living/replicating DNA vaccines is a significant challenge. We have previously shown that ballistic dermal plasmid DNA-encoded flagellin (FliC) promotes humoral as well as cellular immunity to co-delivered antigens. Here, we observe that a plasmid encoding secreted FliC (pFliC(-gly)) produces flagellin capable of activating two innate immune receptors known to detect flagellin; Toll-like Receptor 5 (TLR5) and Nod-like Receptor family CARD domain-containing protein 4 (NRLC4). To test the ability of pFliC(-gly) to act as an adjuvant we immunized mice with plasmid encoding secreted FliC (pFliC(-gly)) and plasmid encoding a model antigen (ovalbumin) by three different immunization routes representative of dermal, systemic, and mucosal tissues. By all three routes we observed increases in antigen-specific antibodies in serum as well as MHC Class I-dependent cellular immune responses when pFliC(-gly) adjuvant was added. Additionally, we were able to induce mucosal antibody responses and Class II-dependent cellular immune responses after mucosal vaccination with pFliC(-gly). Humoral immune responses elicited by heterologus prime-boost immunization with a plasmid encoding HIV-1 from gp160 followed by protein boosting could be enhanced by use of pFliC(-gly). We also observed enhancement of cross-clade reactive IgA as well as a broadening of B cell epitope reactivity. These observations indicate that plasmid-encoded secreted flagellin can activate multiple innate immune responses and function as an adjuvant to non-living/replicating DNA immunizations. Moreover, the capacity to elicit mucosal immune responses, in addition to dermal and systemic properties, demonstrates the potential of flagellin to be used with vaccines designed to be delivered by various routes. Vaccines 2013-09-25 1 4 Article 10.3390/vaccines1040415 415 443 2076-393X 2013-09-25 doi: 10.3390/vaccines1040415 Sanna Nyström Andreas Bråve Tina Falkeborn Claudia Devito Björn Rissiek Daniel Johansson Ulf Schröder Satoshi Uematsu Shizuo Akira Jorma Hinkula Steven Applequist http://www.mdpi.com/2076-393X/1/4/398 2013 marks a milestone year for plasmid DNA vaccine development as a first-in-class cytomegalovirus (CMV) DNA vaccine enters pivotal phase 3 testing. This vaccine consists of two plasmids expressing CMV antigens glycoprotein B (gB) and phosphoprotein 65 (pp65) formulated with a CRL1005 poloxamer and benzalkonium chloride (BAK) delivery system designed to enhance plasmid expression. The vaccine's planned initial indication under investigation is for prevention of CMV reactivation in CMV-seropositive (CMV+) recipients of an allogeneic hematopoietic stem cell transplant (HCT). A randomized, double-blind placebo-controlled phase 2 proof-of-concept study provided initial evidence of the safety of this product in CMV+ HCT recipients who underwent immune ablation conditioning regimens. This study revealed a significant reduction in viral load endpoints and increased frequencies of pp65-specific interferon-γ-producing T cells in vaccine recipients compared to placebo recipients. The results of this endpoint-defining trial provided the basis for defining the primary and secondary endpoints of a global phase 3 trial in HCT recipients. A case study is presented here describing the development history of this vaccine from product concept to initiation of the phase 3 trial. Vaccines 2013-09-25 1 4 Case Report 10.3390/vaccines1040398 398 414 2076-393X 2013-09-25 doi: 10.3390/vaccines1040398 Larry Smith Mary Wloch Jennifer Chaplin Michele Gerber Alain Rolland http://www.mdpi.com/2076-393X/1/3/384 The skin is an attractive tissue for vaccination in a clinical setting due to the accessibility of the target, the ease of monitoring and most importantly the immune competent nature of the dermal tissue. While skin electroporation offers an exciting and novel future methodology for the delivery of DNA vaccines in the clinic, little is known about the actual mechanism of the approach and the elucidation of the resulting immune responses. To further understand the mechanism of this platform, the expression kinetics and localization of a reporter plasmid delivered via a surface dermal electroporation (SEP) device as well as the effect that this treatment would have on the resident immune cells in that tissue was investigated. Initially a time course (day 0 to day 21) of enhanced gene delivery with electroporation (EP) was performed to observe the localization of green fluorescent protein (GFP) expression and the kinetics of its appearance as well as clearance. Using gross imaging, GFP expression was not detected on the surface of the skin until 8 h post treatment. However, histological analysis by fluorescent microscopy revealed GFP positive cells as early as 1 h after plasmid delivery and electroporation. Peak GFP expression was observed at 24 h and the expression was maintained in skin for up to seven days. Using an antibody specific for a keratinocyte cell surface marker, reporter gene positive keratinocytes in the epidermis were identified. H&E staining of treated skin sections demonstrated an influx of monocytes and granulocytes at the EP site starting at 4 h and persisting up to day 14 post treatment. Immunological staining revealed a significant migration of lymphocytic cells to the EP site, congregating around cells expressing the delivered antigen. In conclusion, this study provides insights into the expression kinetics following EP enhanced DNA delivery targeting the dermal space. These findings may have implications in the future to design efficient DNA vaccination strategies for the clinic. Vaccines 2013-08-28 1 3 Article 10.3390/vaccines1030384 384 397 2076-393X 2013-08-28 doi: 10.3390/vaccines1030384 Janess Mendoza Dinah Amante Gleb Kichaev Christine Knott William Kiosses Trevor Smith Niranjan Sardesai Kate Broderick http://www.mdpi.com/2076-393X/1/3/367 Nucleic acid-based vaccines such as viral vectors, plasmid DNA (pDNA), and mRNA are being developed as a means to address limitations of both live-attenuated and subunit vaccines. DNA vaccines have been shown to be potent in a wide variety of animal species and several products are now licensed for commercial veterinary but not human use. Electroporation delivery technologies have been shown to improve the generation of T and B cell responses from synthetic DNA vaccines in many animal species and now in humans. However, parallel RNA approaches have lagged due to potential issues of potency and production. Many of the obstacles to mRNA vaccine development have recently been addressed, resulting in a revival in the use of non-amplifying and self-amplifying mRNA for vaccine and gene therapy applications. In this paper, we explore the utility of EP for the in vivo delivery of large, self-amplifying mRNA, as measured by reporter gene expression and immunogenicity of genes encoding HIV envelope protein. These studies demonstrated that EP delivery of self-amplifying mRNA elicited strong and broad immune responses in mice, which were comparable to those induced by EP delivery of pDNA. Vaccines 2013-08-22 1 3 Article 10.3390/vaccines1030367 367 383 2076-393X 2013-08-22 doi: 10.3390/vaccines1030367 Yen Cu Kate Broderick Kaustuv Banerjee Julie Hickman Gillis Otten Susan Barnett Gleb Kichaev Niranjan Sardesai Jeffrey Ulmer Andrew Geall http://www.mdpi.com/2076-393X/1/3/348 Recent advances in HIV vaccine development along with a better understanding of the immune correlates of risk have emerged from the RV144 efficacy trial conducted in Thailand. Epidemiological data suggest that CRF01_AE is still predominant in South-East Asia and is spreading in China with a growing number of circulating recombinant forms due to increasing human contact, particularly in large urban centers, tourist locations and in sites of common infrastructure. A vaccine countering CRF01_AE is a priority for the region. An Asia HIV vaccine against expanding B/E or BCE recombinant forms should be actively pursued. A major challenge that remains is the conduct of efficacy trials in heterosexual populations in this region. Men who have sex with men represent the main target population for future efficacy trials in Asia. Coupling HIV vaccines with other prevention modalities in efficacy trials might also be envisaged. These new avenues will only be made possible through the conduct of large-scale efficacy trials, interdisciplinary teams, international collaborations, and strong political and community commitments. Vaccines 2013-08-14 1 3 Article 10.3390/vaccines1030348 348 366 2076-393X 2013-08-14 doi: 10.3390/vaccines1030348 Punnee Pitisuttithum Supachai Rerks-Ngarm Robert O'Connell Jerome Kim Jean-Louis Excler http://www.mdpi.com/2076-393X/1/3/343 This Vaccines issue on "Confidence in Vaccines" provides sound evidence through multiple perspectives of life-saving impacts when vaccination programs are effectively implemented in a population. Yet there remain challenges to achieving this impact, including scientific, medical, manufacturing, policy-related and logistical issues. Additionally, socio-cultural, religious and political agendas can come into play, taking public health hostage and sometimes allowing the circulation of myths regarding vaccination. All of these challenges play a role in public confidence in vaccines and vaccination. What we trust, we embrace. What we do not trust, we do not embrace. Vaccines 2013-08-12 1 3 Opinion 10.3390/vaccines1030343 343 347 2076-393X 2013-08-12 doi: 10.3390/vaccines1030343 Norman Begg http://www.mdpi.com/2076-393X/1/3/328 The development of vaccines to treat and prevent human immunodeficiency virus (HIV) infection has been hampered by an incomplete understanding of "protective" immune responses against HIV. Natural control of HIV-1 infection is associated with T-cell responses against HIV-1 Gag proteins, particularly CD8+ T-cell responses restricted by "protective" HLA-B alleles, but other immune responses also contribute to immune control. These immune responses appear to include IgG antibodies to HIV-1 Gag proteins, interferon-a-dependant natural killer (NK) cell responses and plasmacytoid dendritic cell (pDC) responses. Here, it is proposed that isotype diversification of IgG antibodies against HIV-1 Gag proteins, to include IgG2, as well as IgG3 and IgG1 antibodies, will broaden the function of the antibody response and facilitate accessory cell responses against HIV-1 by NK cells and pDCs. We suggest that this should be investigated as a vaccination strategy for HIV-1 infection. Vaccines 2013-08-09 1 3 Review 10.3390/vaccines1030328 328 342 2076-393X 2013-08-09 doi: 10.3390/vaccines1030328 Martyn French Laila Abudulai Sonia Fernandez http://www.mdpi.com/2076-393X/1/3/305 HIV-1 DNA vaccines have many advantageous features. Evaluation of HIV-1 vaccine candidates often starts in small animal models before macaque and human trials. Here, we selected and optimized DNA vaccine candidates through systematic testing in rabbits for the induction of broadly neutralizing antibodies (bNAb). We compared three different animal models: guinea pigs, rabbits and cynomolgus macaques. Envelope genes from the prototype isolate HIV-1 Bx08 and two elite neutralizers were included. Codon-optimized genes, encoded secreted gp140 or membrane bound gp150, were modified for expression of stabilized soluble trimer gene products, and delivered individually or mixed. Specific IgG after repeated i.d. inoculations with electroporation confirmed in vivo expression and immunogenicity. Evaluations of rabbits and guinea pigs displayed similar results. The superior DNA construct in rabbits was a trivalent mix of non-modified codon-optimized gp140 envelope genes. Despite NAb responses with some potency and breadth in guinea pigs and rabbits, the DNA vaccinated macaques displayed less bNAb activity. It was concluded that a trivalent mix of non-modified gp140 genes from rationally selected clinical isolates was, in this study, the best option to induce high and broad NAb in the rabbit model, but this optimization does not directly translate into similar responses in cynomolgus macaques. Vaccines 2013-07-19 1 3 Article 10.3390/vaccines1030305 305 327 2076-393X 2013-07-19 doi: 10.3390/vaccines1030305 Marie Borggren Lasse Vinner Betina Andresen Berit Grevstad Johanna Repits Mark Melchers Tara Elvang Rogier Sanders Frédéric Martinon Nathalie Dereuddre-Bosquet Emma Bowles Guillaume Stewart-Jones Priscilla Biswas Gabriella Scarlatti Marianne Jansson Leo Heyndrickx Roger Grand Anders Fomsgaard http://www.mdpi.com/2076-393X/1/3/293 There is increasingly broad global recognition of the need to better understand determinants of vaccine acceptance. Fifteen social science, communication, health, and medical professionals (the "Motors of Trust in Vaccination" (MOTIV) think tank) explored factors relating to vaccination decision-making as a step to building a multidisciplinary research agenda. One hundred and forty seven factors impacting decisions made by consumers, professionals, and policy makers on vaccine acceptance, delay, or refusal were identified and grouped into three major categories: cognition and decision-making; groups and social norms; and communication and engagement. These factors should help frame a multidisciplinary research agenda to build an evidence base on the determinants of vaccine acceptance to inform the development of interventions and vaccination policies. Vaccines 2013-07-18 1 3 Communication 10.3390/vaccines1030293 293 304 2076-393X 2013-07-18 doi: 10.3390/vaccines1030293 Heidi Larson Julie Leask Sian Aggett Nick Sevdalis Angus Thomson http://www.mdpi.com/2076-393X/1/3/278 DNA vaccines can induce both humoral and cellular immune responses. Although some DNA vaccines are already licensed for infectious diseases in animals, they are not licensed for human use because the risk and benefit of DNA vaccines is still controversial. Indeed, in humans, the immunogenicity of DNA vaccines is lower than that of other traditional vaccines. To develop the use of DNA vaccines in the clinic, various approaches are in progress to enhance or improve the immunogenicity of DNA vaccines. Recent studies have shown that immunogenicity of DNA vaccines are regulated by innate immune responses via plasmid DNA recognition through the STING-TBK1 signaling cascade. Similarly, molecules that act as dsDNA sensors that activate innate immune responses through STING-TBK1 have been identified and used as genetic adjuvants to enhance DNA vaccine immunogenicity in mouse models. However, the mechanisms that induce innate immune responses by DNA vaccines are still unclear. In this review, we will discuss innate immune signaling upon DNA vaccination and genetic adjuvants of innate immune signaling molecules. Vaccines 2013-07-18 1 3 Review 10.3390/vaccines1030278 278 292 2076-393X 2013-07-18 doi: 10.3390/vaccines1030278 Kouji Kobiyama Nao Jounai Taiki Aoshi Miyuki Tozuka Fumihiko Takeshita Cevayir Coban Ken Ishii