How did the 'Berlin patient' rid himself of HIV?

This case is one of the most studied cases in the HIV epidemic history. The case is about a man Timothy Ray Brown who is the only person to have been cured of HIV. He lived with the virus for 11 years before he eventually developed leukemia. Brown had been on chemotherapy for quite some time but it ultimately proved ineffective. So the next step was to have a bone marrow transplant, which is a common treatment for this type of cancer. This is when he stopped taking his antiretroviral drugs, which usually results in levels of HIV to skyrocket afterwards. But in Brown's case, he was left with little to no trace of any viral genetic material in his body. Doctors attribute this strange success to 3 possibilities. Before he had the bone marrow transplant, the doctors destroyed his immune system with chemotherapy. Secondly, when Brown got the bone marrow transplant, the donor had an extremely rare genetic mutation in which the key receptor on the white blood cell that the virus targets was not there, which prevented the virus from establishing the infection. Lastly, the new immune system attacked the remnants of his old one that held the infected cells. Scientists are trying to replicate this bizarre procedure with monkeys who have leukemia but have not had major success. After the chemo radiation to wipe out the immune system and the bone marrow transplant, the HIV infected cells make a complete resurgence. I think this is a very fascinating case, because it is thought that HIV is incurable. Hopefully one day scientists will find the genetic mutation that caused this rare mutation and can pin point it to exactly where it is on the genome so that we can one day replicate the results, and be able to cure the cancer for many people to come. I think its interesting that not all genetic mutations are necessarily bad, in this case it cured someone from an extreme illness.

http://www.sciencemag.org/news/2014/09/how-did-berlin-patient-rid-himself-hiv