Timothy Ray Brown, also known as the “Berlin patient,” is the only human believed to have been cured of HIV, following a bone marrow transplant from a donor immune to the virus. Now, researchers of a new study published in PLOS Pathogens have tested the potential mechanisms underlying this cure in monkeys.

Share on Pinterest Researchers found that although radiation exposure prior to stem cell transplantation reduced the viral reservoir in monkeys infected with a chimeric simian/human immunodeficiency virus, it failed to cure them.

In 1995, Brown was diagnosed with HIV (human immunodeficiency virus). After undergoing antiretroviral therapy (ART) for the infection for more than 10 years, he was also diagnosed with acute myeloid leukemia.

Brown was treated with radiation and chemotherapy, before receiving a bone marrow transplant from a donor who possessed a mutation that wipes out the function of CCR5 – a gene that allows HIV to enter human cells.

Last year, a study confirmed that Brown had been functionally cured of HIV. He had no detectable HIV replication in his blood and had gone without ART for 5 years.

According to the researchers, led by Guido Silvestri of Emory University in Atlanta, GA, there are many possible mechanisms that could have contributed to Brown’s cure. They note that the CCR5 mutation in donor cells may have protected the patient against HIV infection, or the donor cells may have deemed the host cells as invaders and attacked them – a “graft versus host” response – eliminating any cells infected with HIV that survived radiation.

Furthermore, the removal of blood and immune cells after radiation exposure could have destroyed all or the majority of infected cells that had previously avoided the clutches of ART. For the first time, Silvestri and colleagues tested this strategy in monkeys.