German Man Maintains HIV Remission After Stem Cell Treatment

A man from Germany has been in remission from HIV for an impressive six years following a stem cell transplant aimed at treating his aggressive leukemia. This patient, referred to as Berlin 2 (B2), is now among the few known cases of long-term HIV remission.

B2 received a transplant of donor stem cells that contained only one copy of a mutation believed to confer resistance to HIV. This is in contrast to other patients who received stem cells containing two copies of this mutation. While the single-copy cells were expected to offer only temporary resistance, they have sparked curiosity about how the HIV virus was effectively cleared from B2’s system.

Immunologist Christian Gaebler, who led research published in a recent paper, suggests that this case might open up new avenues for understanding potential HIV cures.

HIV is notoriously difficult to treat, primarily because it attacks the body’s immune cells, diminishing the immune response and leaving individuals susceptible to additional infections. The virus is adept at changing rapidly and can develop resistance to medications if not treated consistently. It employs a receptor known as CCR5 to infiltrate host cells, where it can integrate its DNA into the genome and remain dormant within certain immune cells for extended periods. This creates reservoirs that are challenging to target with standard antiretroviral therapies.

In successful stem cell transplant cases, aggressive chemotherapy is first administered to eliminate a large portion of the immune cells, including those harboring the virus. After that, a transplant of stem cells helps rebuild the immune system, ideally enabling it to identify and target any remaining viral reservoirs.

Out of the seven identified cases of long-term remission, five involved donors with two copies of the CCR5 Δ32 mutation, which essentially blocks HIV from entering the cells. Interestingly, B2 already had one copy of the mutation inherited from a parent but still contracted HIV in 2009. After receiving a matching stem cell donor with one copy of the mutation and undergoing treatment, he stopped taking his antiretroviral medication in 2018 and has maintained an undetectable level of the virus since then.

This particular instance indicates that having two copies of the mutation may not be essential for achieving long-lasting HIV remission following a stem cell transplant. In fact, there’s another patient—also in remission—whose donor lacked the CCR5 Δ32 mutation. However, some other patients who had standard donors experienced a resurgence of the virus, suggesting that further research is necessary.

While the CCR5 Δ32-based stem cell treatment offers hope, it’s not likely to become a standard option for HIV patients due to the potential for severe side effects and complications arising from intensive chemotherapy and transplant procedures. Interestingly, B2’s case might steer future research toward less invasive methods that could mimic the beneficial aspects of the transplant process—like reducing viral reservoirs and potentially utilizing pharmaceutical or gene editing techniques instead.

The researchers emphasize the importance of targeting and possibly eliminating these viral reservoirs as vital in any long-term strategy aimed at curing HIV. Their findings appear in the journal Nature.