<qa>  What is the net effect of the prime-boost vaccination?The study design is a two-arm, open label randomised study. Eligible participants are recruited from two participant cohorts Cohort I - Recently diagnosed or Cohort II - Previously diagnosed with HIV. All participants receive combination ART cART for the duration of the intervention phase of the study Cohort I: 42 weeks, Cohort II: 18 weeks. In patients meeting the criteria for randomisation eligibility assessed at week 22screening, participants will either continue cART or receive an intervention consisting of two anti-HIV vaccines separated by 8 weeks followed by 10 doses of the HDACi, vorinostat, in addition to cART. We hypothesise that the prime-boost vaccination will result in the generation of vaccine induced HIV specific CTLs that will recognise HDACi-activated cells of the HIV reservoir and destroy them. The net effect will be a greater reduction in the HIV reservoir defined as HIV total DNA in CD4 T-cells in the cARTvaccineHDACi compared to the cART alone. Our strategy is entirely different from previous therapeutic vaccination approaches which have been largely unsuccessful. Immunological priming to conserved HIV proteins will drive CD8 T-lymphocyte recognition of latently-infected cells rendered immunogenic by HDACi. We anticipate that the viral antigens expressed by latently-infected cells will be unable to adapt to, or escape from, the immune response as they will be expressed directly from chromosomal DNA, avoiding the steps of the viral life-cycle that facilitate immune-driven adaptation. We have chosen a prime-boost immunisation strategy with recombinant replication-defective chimpanzee adenovirus and modified vaccinia Ankara vectors, bearing conserved HIV antigens; these products have been shown to induce high titres of HIV-specific CD8 T-cells. In addition, these vaccines will drive immune responses against conserved regions of the virus that may be well preserved in individuals with PHI. 