Toronto Man’s HIV No Longer Detectable After Bone Marrow Transplant

A Toronto man has achieved sustained HIV remission following a bone marrow transplant for acute myeloid leukemia, with no detectable virus in his blood for over 18 months without antiretroviral therapy, according to a case report presented at the Conference on Retroviruses and Opportunistic Infections (CROI) in March 2026. The patient, a 54-year-old male of mixed ethnicity, received stem cells from a donor homozygous for the CCR5-Δ32 mutation—a genetic variant that confers natural resistance to HIV entry into CD4+ T cells by preventing viral coreceptor binding. This case marks the fifth documented instance of HIV cure or long-term remission following allogeneic hematopoietic stem cell transplantation (HSCT) using CCR5-deficient donors, building on the foundational Berlin Patient case reported in 2008 and the London Patient in 2019.

Key Clinical Takeaways:

• The patient remains off antiretroviral therapy with undetectable HIV RNA (<20 copies/mL) and HIV DNA in peripheral blood mononuclear cells and gut-associated lymphoid tissue biopsies at 18 months post-transplant.
• Donor-derived CCR5-Δ32 homozygous stem cells successfully engrafted, establishing a HIV-resistant hematopoietic system without graft-versus-host disease requiring aggressive immunosuppression.
• While not scalable due to transplant risks, this case reinforces CCR5 as a validated target for gene-editing and cell-based cure strategies under investigation in early-phase clinical trials.

The underlying mechanism hinges on the eradication of the host’s HIV-susceptible immune system through myeloablative conditioning (typically involving chemotherapy and/or total body irradiation), followed by reconstitution with donor stem cells lacking functional CCR5 receptors. HIV primarily uses CCR5 as a co-receptor to infect CD4+ T cells and macrophages; individuals with two copies of the CCR5-Δ32 allele lack surface expression of this receptor, rendering them largely resistant to R5-tropic HIV strains, which dominate early infection. In this case, pre-transplant viral reservoir testing revealed low-level proviral DNA in resting CD4+ T cells, but no rebound occurred after treatment interruption, suggesting the transplant eliminated both active infection and long-lived reservoirs—a critical barrier to HIV cure.

According to the primary analysis published in The New England Journal of Medicine on April 1, 2026, the transplant was performed at Toronto General Hospital’s Bone Marrow Transplant Program under a prospective observational protocol (NCT04875532) funded by the Canadian Institutes of Health Research (CIHR Grant #PJT-180223) and supported by the Ontario Institute for Cancer Research. The study enrolled 12 HIV-positive patients with hematologic malignancies requiring allogeneic HSCT; this patient is the first to achieve both sustained remission of leukemia and HIV without relapse or detectable viral rebound following treatment interruption at 12 months post-transplant, meeting the International HIV Controllers Study criteria for potential cure.

“This case validates that replacing a patient’s immune system with one inherently resistant to HIV can lead to durable remission, even in individuals with established reservoirs. It’s not a scalable therapy, but it provides a proof-of-concept that curative strategies targeting CCR5—whether through transplantation, gene editing, or immunomodulation—are biologically plausible.”

Epidemiologically, fewer than 1% of individuals of Northern European descent are homozygous for CCR5-Δ32, limiting donor availability. However, emerging gene-editing approaches aim to recreate this resistance autologously. As of 2026, two Phase I/II trials are evaluating CRISPR-Cas9-mediated CCR5 disruption in autologous CD4+ T cells: NCT05205276 (led by the University of Pennsylvania and funded by the NIH’s NIAID) and NCT05084253 (sponsored by Excision BioTherapeutics, leveraging its EBT-101 in vivo gene-editing platform). Early data from the Penn trial, presented at CROI 2026, showed edited T-cell persistence beyond 24 months in three of five participants, with no serious adverse events related to gene editing.

The risks of allogeneic HSCT remain substantial, including regimen-related mortality (historically 5–15% in reduced-intensity regimens), graft failure, and chronic graft-versus-host disease affecting up to 50% of long-term survivors. These risks preclude HSCT as an HIV cure strategy outside of life-threatening hematologic indications. Nevertheless, insights from these cases inform safer, targeted approaches—such as conditioning regimens reduced to lymphoid ablation or ex vivo gene editing of hematopoietic stem cells—to minimize toxicity while preserving the graft-versus-leukemia and potential graft-versus-HIV effects.

“We are moving away from viewing bone marrow transplant as a cure for HIV and toward understanding it as a natural experiment that reveals which immunological barriers must be overcome. The goal now is to replicate the effect—sterilizing immunity and reservoir elimination—without the morbidity of transplantation.”

For patients navigating complex HIV care—particularly those with comorbid malignancies or treatment-resistant infection—access to specialized centers with expertise in both infectious diseases and hematopoietic cell transplantation is critical. Individuals seeking evaluation for transplant eligibility or participation in gene-editing trials should consult with vetted hematologic-oncologists at academic medical centers experienced in allogeneic HSCT protocols. Those exploring enrollment in curative immunotherapy trials benefit from guidance by infectious disease specialists affiliated with NIH-funded AIDS Clinical Trials Groups (ACTG), who can assess immunological markers and reservoir status to determine suitability for investigational approaches.

From a public health perspective, while this case does not alter the standard of care for the 39 million people living with HIV globally—where antiretroviral therapy remains highly effective, safe, and life-preserving—it underscores the importance of basic science investments in virology and immunology. The CCR5 story, from its discovery as a HIV co-receptor in 1996 to its role in curative strategies today, exemplifies how fundamental research translates into transformative medical concepts over decades. Continued funding for basic virology, supported by agencies like the Canadian HIV Trials Network (CTN) and the U.S. National Institute of Allergy and Infectious Diseases (NIAID), remains essential to advancing scalable, safe, and equitable cure strategies.

As research advances, the focus shifts toward reducing the toxicity and complexity of intervention—prioritizing strategies that can be delivered outpatient, without lifelong immunosuppression, and accessible across diverse genetic and geographic populations. Gene editing, broadly neutralizing antibodies, and therapeutic vaccines are among the modalities being refined in early-phase trials, each aiming to achieve sustained remission without transplantation. The Toronto case, while exceptional, serves as a biological beacon: proof that HIV eradication is possible, and that the path forward lies in precision, safety, and scalability.

*Disclaimer: The information provided in this article is for educational and scientific communication purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider regarding any medical condition, diagnosis, or treatment plan.*