A second patient with HIV has been cured with a stem cell transplant at Charité – Berlin University Medicine. In 2008, the “Berlin Patient” became the first person in the world to be cured of HIV, by such a transplant. In both cases the patients were being treated for blood cancers using stem cell transplants and the researchers specially selected the donors. HIV is typically incurable. After transplant, the current patient has had no detectable virus for more than five years even though he is not taking antiviral medications.
The first Berlin patient received stem cells from a donor who was homozygous for CCR5, which can protect against HIV infection, but is very rare. This second patient’s donor was heterozygous for CCR5. Why this patient was cured while the virus has resumed replicating in comparable cases is still unclear. The researchers are considering multiple potential factors.
This new case will be presented at the International AIDS Conference in Munich on July 24.
A team from Charité demonstrated that stem cell transplants work against HIV as well as cancer back in 2008, when they applied it to the person who came to be known as the “Berlin Patient.” Since then, four more people worldwide have been treated in this way and are now viewed as having been cured of HIV.
Stem cell transplantation is only used in patients who have HIV and develop certain forms of leukemia or lymphoma that do not respond to radiation or chemotherapy. In such a transplant, stem cells from a healthy person are transferred to the patient to basically replace their immune system. Engineered correctly, these cells can fight the cancer and HIV.
In order to multiply, HIV requires the CCR5 receptor to enter immune cells. Only about one percent of the European population has a CCR5 receptor with what is known as the delta 32 mutation. It prevents the virus from entering, making people with this mutation naturally immune to HIV. If it is possible to find a stem cell donor whose tissue is a match for the recipient and that person carries this immunity-causing mutation, then stem cell transplantation can cure not only the patient’s cancer, but also HIV.
The second patient, now 60, tested positive for HIV in 2009 and was then diagnosed with AML in 2015. A team from the department of hematology, oncology and cancer immunology at Charité took him on as a leukemia patient. The patient’s risk profile meant that it was necessary for him to undergo both chemotherapy and additional stem cell transplantation.
“We couldn’t find a matching stem cell donor who was immune to HIV, but we did manage to find one whose cells have two versions of the CCR5 receptor: the normal one, and then an extra, mutated one,” explains Olaf Penack, MD, PhD, a senior physician at the department treating the patient. “This occurs when a person inherits the delta 32 mutation from only one parent. However, having both versions of the receptor does not confer immunity to HIV.”
Even though the donor was not herself immune, it became apparent that the stem cell transplantation had been successful in curing HIV after the patient discontinued the recommended antiviral treatment on his own in 2018.
