HIV in their blood plasma and purified CD4 T cells using a sensitive culture method

In 2012, Daniel Kuritzkes reported results of two stem cell transplants in patients with HIV. They did not, however, use donors with the Δ32 deletion. One of the men has been followed for two years and the other for three and a half years. While both are still on HIV treatment, neither shows traces of HIV in their blood plasma and purified CD4 T cells using a sensitive culture method (less than 3 copies/ml). They are also showing a significant decline in HIV antibodies, suggesting a lack of HIV replication.[49][verification needed]In 2007, a team of doctors in Berlin, Germany, including Gero Hütter, performed a stem cell transplant for leukemia patient Timothy Ray Brown, who was also HIV-positive. From 60 matching donors, they selected a [CCR5]-Δ32 homozygous individual with two genetic copies of a rare variant of a cell surface receptor. This genetic trait confers resistance to HIV infection by blocking attachment of HIV to the cell. Roughly one in 1000 people of European ancestry have this inherited mutation, but it is rarer in other populations..The transplant was repeated a year later after a relapse. Over three years after the initial transplant and despite discontinuing antiretroviral therapy, researchers cannot detect HIV in the transplant recipient's blood or in various biopsies. Levels of HIV-specific antibodies have also declined, leading to speculation that the patient may have been functionally cured of HIV. However, scientists emphasise that this is an unusual case.[46] Potentially fatal transplant complications (the "Berlin patient" suffered from graft-versus-host disease and leukoencephalopathy) mean that the procedure could not be performed in others with HIV, even if sufficient numbers of suitable donors were found.