Toronto Man’s HIV in Remission After Bone Marrow Transplant for Cancer Treatment

A Toronto man could soon join a small group of individuals worldwide considered to be in remission from HIV following a bone marrow transplant performed to treat cancer, according to health officials and medical researchers involved in his care.

The 62-year-old man, referred to by health officials only as the “Toronto patient,” was diagnosed with acute myelogenous leukemia in 2021 and subsequently underwent a bone marrow transplant at the Princess Margaret Cancer Centre, part of the University Health Network (UHN). The transplant utilized donor stem cells selected for a rare genetic mutation known as CCR5 delta-32, which confers natural resistance to HIV infection.

According to researchers from UHN, Unity Health Toronto, and the University of Toronto, the CCR5 gene produces a protein on the surface of immune cells that HIV uses to enter and infect cells. Individuals with the delta-32 mutation do not produce this receptor, making them resistant to certain strains of HIV. Approximately one percent of people of European descent carry this genetic trait.

Mario Ostrowski, a clinician-scientist at St. Michael’s Hospital (Unity Health Toronto), explained that bone marrow transplants from donors with the delta-32 mutation can provide a potential pathway to curing HIV by replacing the recipient’s immune system with one that HIV cannot infect.

In the case of the Toronto patient, this approach appears to have been successful. Following the transplant, medical teams observed that the man’s HIV became undetectable, and his immune system showed no signs of being affected by the virus.

Sharon Walmsley, director of the HIV clinic at UHN’s Toronto General Hospital, described the development as a significant change for the patient. “This person now has an immune system that cannot be affected by HIV,” she said. “He is quite amazed by all of this… When we told him that we believe him to be cured, he was quite astonished.”

The case was presented publicly on Saturday at the Canadian Association of HIV Research Conference in Winnipeg, where researchers shared updates on the patient’s progress. While the term “cure” is being used cautiously, the sustained absence of detectable HIV following the transplant meets criteria used by researchers to define long-term remission or potential cure in the context of such interventions.

Only a handful of cases globally have demonstrated similar outcomes, most notably the “Berlin patient” and the “London patient,” both of whom underwent bone marrow transplants for cancer treatment and subsequently showed no detectable HIV after stopping antiretroviral therapy. The Toronto case, if confirmed, would represent a third such instance and the first reported in Canada.

Medical experts emphasize that bone marrow transplantation remains a high-risk procedure and is not considered a viable or scalable treatment for HIV due to its intensity, potential complications, and the rarity of suitable donors. However, these rare cases continue to inform scientific understanding of HIV reservoirs and the conditions under which the virus might be eradicated from the body.

Researchers involved in the Toronto patient’s care continue to monitor his health closely, conducting regular tests to confirm the absence of HIV and assess immune function. As of the latest update, no rebound of the virus has been detected, and the patient remains in good health following his cancer treatment.

The findings underscore the importance of continued investment in HIV research and the exploration of innovative, albeit complex, strategies aimed at achieving long-term remission or a functional cure. While not applicable to the broader population, such cases provide critical insights that may guide future therapeutic approaches.