Until this year, the only person known to have been cured of HIV was an individual, known as the ‘Berlin patient’, who received two allogenic hematopoietic stem cell transplants following total body irradiation, all to treat his acute myeloid leukemia. The cells used in these transplants lacked CCR5 (CCR5 Δ32/Δ32), a crucial HIV entry receptor leading to the cure.
This year, a person with HIV known as the ‘London patient’ went into remission following a single (CCR5Δ32/Δ32) allogeneic stem cell transplant without total body irradiation, indicating not only that the Berlin patient wasn’t a fluke but also that cell-based cure strategies needn’t be so toxic.
In parallel, scientists have been testing CRISPR technology to remove CCR5 from hematopoietic stem cells for transplant into HIV-infected individuals. A patient who was treated 19 months ago for acute lymphoblastic leukemia with these cells is alive, indicating that the approach is safe; however, the levels of CCR5 disruption in their lymphocytes are too low for them to stop antiretroviral drug therapy.