The 'Berlin patient' is an HIV-positive man who developed acute myeloid leukaemia, received successful treatment and subsequently experienced a relapse in 2007 that required a transplant of stem cells. 
 
 Doctors chose stem cells from an individual who had an unusual genetic profile: a mutation inherited from both parents that resulted in CD4 cells that lacked the CCR5 receptor. This mutation, called CCR5 delta 32 homozygosity, is present in less than 1% of Caucasians in northern and western Europe, and is associated with a reduced risk of becoming infected with HIV. 
 
 This is because all new infecting viruses need to use the CCR5 receptor on CD4 cells when infecting an immune system cell of the CD4 type. 
 
 Later in the course of HIV infection another type of virus emerges that can use the CXCR4 receptor instead. 
 
 Before the stem cell transplant the patient received chemotherapy treatment that destroyed most immune cells and total body irradiation, and also received immunosuppressive drugs to prevent rejection of the stem cells. 
 
 Antiretroviral therapy was halted on the day of the transplant, and the patient had to receive a second stem cell transplant 13 days after the first one, due to a further relapse of leukaemia. 
 
 The patient continued to receive immunosuppressive treatment to prevent rejection for 38 months, and at 5, 24 and 29 months post-transplant colon biopsies were taken to investigate possible graft-versus-host disease in the intestine. At each investigation additional samples were taken to check for signs of HIV infection in the abundant immune cells of the gut wall. 
 
 During the 38 month follow-up period the donor CD4 cells repopulated the mucosal immune system of the gut, to such an extent that the frequency of CD4 cells was almost twice as high as in HIV-negative healthy controls, and this phenomenon was also seen in a control group of ten HIV-negative individuals who received stem cell transfers. 
 
 The repopulation of CD4 cells was accompanied by the complete disappearance of host CD4 cells, and after two years the patient had the CD4 count of a healthy adult of the same age. 
 
 One of the challenges for any approach to curing HIV infection is long-lived immune system cells, which need to be cleared before a patient can be cured. In the case of the Berlin patient CCR5-bearing macrophages could not be detected after 38 months, suggesting that chemotherapy had destroyed these longer-lived cells, and that they had also been replaced by donor cells. 
 
 The German researchers and San Francisco-based immunologist Professor Jay Levy believe that the findings point to the importance of suppressing the production of CCR5-bearing cells, either through transplants or gene therapy. 
 
 The patient did not resume antiretroviral therapy after the transplant. 
 
 Nevertheless HIV remained undetectable by both viral load testing (RNA) and tests for viral DNA within cells, and HIV antibody levels declined to the point that the patient has no antibody reactivity to HIV core antibodies, and only very low levels of antibodies to the HIV envelope proteins. 
 
 Seventeen months after the transplant the patient developed a neurological condition, which required a brain biopsy and lumbar puncture to sample the cerebrospinal fluid for diagnostic purposes. HIV was also undetectable in the brain and the CSF. 
 
 An additional indication that HIV is not present lies in the fact that the patient’s CD4 cells are vulnerable to infection with virus that targets the CXCR4 receptor. If any virus with this preference was still present, the researchers argue, it would be able to swiftly infect the large population of memory CD4 cells that has emerged. ||||| On the heels of World AIDS Day comes a stunning medical breakthrough: Doctors believe an HIV-positive man who underwent a stem cell transplant has been cured as a result of the procedure. 
 
 Timothy Ray Brown, also known as the "Berlin Patient," received the transplant in 2007 as part of a lengthy treatment course for leukemia. His doctors recently published a report in the journal Blood affirming that the results of extensive testing "strongly suggest that cure of HIV infection has been achieved." 
 
 Brown's case paves a path for constructing a permanent cure for HIV through genetically-engineered stem cells. 
 
 Last week, Time named another AIDS-related discovery to its list of the Top 10 Medical Breakthroughs of 2010. Recent studies show that healthy individuals who take antiretrovirals, medicine commonly prescribed for treating HIV, can reduce their risk of contracting the disease by up to 73 percent. 
 
 While these developments by no means prove a cure for the virus has been found, they can certainly provide hope for the more than 33 million people living with HIV worldwide. Alongside such findings, global efforts to combat the epidemic have accelerated as of late, with new initiatives emerging in the Philippines and South Africa this week.
– In another potentially big break in the treatment of AIDS, scientists believe that an HIV-positive man has been cured by a stem cell transplant, the Huffington Post reports. Timothy Ray Brown, often referred to as the "Berlin Patient," underwent both stem-cell therapy alongside conventional chemotherapy for leukemia—not his HIV infection. But three years later, researchers say that test results "strongly suggest that cure of HIV infection has been achieved." The stem cell donor just happened to have a natural resistance to HIV infection, explains AIDSmap.com. "If a cure has been achieved in this patient, it points the way towards attempts to develop a cure for HIV infection through genetically engineered stem cells," writes Keith Alcorn.