Seventh patient ‘cured’ of HIV: why scientists are excited

🌈 Abstract

The article discusses the case of a 60-year-old man in Germany who has become free of HIV after receiving a stem-cell transplant, making him the second person to receive stem cells that are not resistant to the virus. This case challenges the previous belief that targeting the CCR5 receptor is the key to curing HIV, and suggests that there may be other mechanisms involved in HIV eradication through stem-cell transplants.

🙋 Q&A

[01] The Next Berlin Patient

1. What is the key finding about the latest case of an HIV-free patient after a stem-cell transplant?

• The latest case, referred to as the "next Berlin patient", received stem cells from a donor who only had one copy of the mutated CCR5 gene, rather than the special donor stem cells with both copies of the mutated gene that were used in previous cases.
• This suggests that finding a cure for HIV is "not all about CCR5" and that there may be other mechanisms involved in HIV eradication through stem-cell transplants.

2. How does this case broaden the potential donor pool for stem-cell transplants for HIV treatment?

• Roughly 1% of people of European descent carry mutations in both copies of the CCR5 gene, but some 10% have one mutated copy.
• The fact that the "next Berlin patient" received stem cells from a donor with only one mutated copy of the CCR5 gene means the donor pool for stem-cell transplants is expanded.

3. What are some of the proposed mechanisms for why this stem-cell transplant succeeded when others have failed?

• Antiretroviral treatment reducing the amount of virus in the body
• Chemotherapy before the transplant killing many of the host's immune cells where residual HIV lurks
• Transplanted donor cells marking leftover host cells as foreign and destroying them, along with any virus residing in them
• The rapid and complete replacement of the host's bone-marrow stem cells with those of the donor's contributing to swift eradication

4. How could this case impact therapies currently in early-stage clinical trials that use gene editing to target the CCR5 receptor?

• Even if these therapies don't get to every single cell, they could still have an impact, as the fact that both the "next Berlin patient" and their donor had one mutated CCR5 gene copy could create an extra barrier to the virus entering cells.

[02] Previous HIV-Free Cases

1. Who was the first person found to be HIV-free after a bone-marrow transplant, and what was unique about the donor stem cells used in his case?

• The first person found to be HIV-free after a bone-marrow transplant was Timothy Ray Brown, known as the "Berlin patient".
• Brown and a handful of others received special donor stem cells that carried a mutation in the gene encoding the CCR5 receptor, which is used by most HIV virus strains to enter immune cells.

2. How did the outcomes of previous attempts to transplant stem cells from donors with regular CCR5 genes differ from the latest case?

• Previous attempts to transplant stem cells from donors with regular CCR5 genes have seen the virus reappear weeks to months after the people with HIV stopped taking antiretroviral therapy, in all but one person.
• In contrast, the "next Berlin patient" has been free of the virus for almost six years after stopping antiretroviral therapy.

3. What is known about the Geneva patient, who was also reported to be free of HIV after a stem-cell transplant?

• The Geneva patient, presented in 2023, had been without antiretroviral therapy for 18 months and remains free of the virus, about 32 months later.