Berlin patient

American Timothy Ray Brown had been living with HIV for 11 years, taking antiretroviral medication to suppress the virus, when he developed leukemia (unrelated to his HIV infection). His doctor in Berlin, where he was living, used a bone marrow donor with a known genetic mutation which gives resistance to HIV infection by blocking attachment of HIV to cells. Despite discontinuing his antiretroviral therapy, levels of HIV in his blood rapidly fell to undetectable levels, his CD4 count increased, and researchers have not detect HIV in his blood or in various biopsies since. It's thought that a combination of chemotherapy destroying his own immune system, a transplant using a naturally resistant donor, and his new immune system attacking the remnants of his old one all helped rid his body of HIV. Brown is the only individual who is considered to have a 'sterilizing cure', meaning he no longer harbours the HIV virus within his body, as opposed to a functional cure when someone still harbours the virus within their bodies but does not need to take antiretroviral treatment. This case has been seen by many as providing key parts of a blueprint from which to work towards a cure.