Two HIV-infected men are showing no traces of HIV in their blood after going through stem cell transplants similar to the one "Berlin Patient" Timothy Brown received, according to a study presented at the XIX International AIDS Conference.
The study results, discussed by Daniel Kuritzkes, M.D., from Brigham and Women's Hospital in Boston, showed a promising method of targeting the latent or hidden HIV reservoir.
Both patients underwent allogeneic (or foreign) stem cell transplantation for the treatment of lymphoma after being on antiretroviral therapy (ART) for about four years. The first patient was born with HIV and started ART three to four years before the transplant, while the second acquired HIV through sex in the mid '80s and started ART in 2003 before receiving a transplant in 2007.
Prior to the transplants, both men had undetectable viral loads, but still had HIV in hidden CD4 reservoirs. In contrast to Brown, they received a milder form of chemotherapy just before their transplants and were able to stay on HIV treatment throughout the transplant process.
While Brown's donor cells lacked the key CCR5 receptor, which HIV uses to attach to CD4 cells, the two men received donor cells that did have the CCR5 receptor and were fully susceptible to HIV. However, because they were able to remain on ART during the transplant period, the donor cells were not infected with HIV.
"We believe that continual administration of effective ART protected the donor cells from becoming HIV infected as those donor cells eliminated and replaced the patients' own immune cells, effectively clearing the virus from the patients' blood lymphocytes," Kuritzkes said.
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.
"The importance of our findings is that we have evidence now that we can protect uninfected cells from becoming infected when they're transplanted into an HIV-infected patient, a form of PrEP at the cellular level, if you will," Kuritzkes added.
The researchers plan on assessing the full extent of HIV reservoir reduction by looking for HIV in various body tissues and analyzing the effects of treatment interruption.