Third Patient Becomes “HIV Free” After Stem Cell Therapy
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A 53-year-old male patient in Düsseldorf is the third person to achieve long-term human immunodeficiency virus type 1 (HIV-1) remission after receiving a stem cell therapy. The case study is published in Nature.
Long-acting therapies for HIV
The development of antiretroviral therapy (ART) for the treatment of HIV has resulted in the disease evolving from a fatal condition to one that is chronic, but manageable, in many patient cases. The goal of ART is to suppress the viral load such that it is undetectable, meaning the virus cannot be transmitted from one person to another. ART regimens require HIV patients to take a combination of medications daily, and long-acting therapeutic options are sought after.
In Nature, virologist Dr. Björn-Erik Ole Jensen and colleagues at the University Hospital of Düsseldorf report sustained HIV-1 remission in a 53-year-old patient who was diagnosed with acute myeloid leukemia (AML) in January 2008. The patient had been undergoing ART for several years prior to the AML diagnosis, for which he was prescribed allogeneic hematopoietic stem cell transplantation therapy (HSCT).
What is HSCT?
HSCT is a type of cancer immunotherapy that aims to “reset” a patient’s immune system to support their fight against cancer. The patient’s own bone marrow is effectively “wiped out” and replaced by transferring blood stem cells from a donor.
In this instance, the donor stem cells carried a mutation in the gene encoding the HIV-1 receptor CCR5, which prevents expression of the CCR5 cell-surface protein – a protein that is critical for HIV to enter and infect cells.
"During the pandemic, the public learned that viruses use special ‘door handles’ called receptors to get into our cells. Just as SARS-CoV-2 uses the ACE-2 receptor to infect cells of the lungs and other tissues, HIV uses a different receptor called CCR5 to infect cells of the immune system,” explains Dr. Ioannis Jason Limnios from the Clem Jones Centre for Regenerative Medicine at Bond University, who was not involved in the study.
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“What happens if the door handle is missing? For about 30 years, it has been known that some individuals are resistant to HIV infection because they lack CCR5 receptors on their cells; HIV can’t open the door and get inside,” he adds.
Patient achieves long-term HIV remission
The therapy used by Jensen and team – called CCR5Δ32/Δ32 HSCT – has demonstrated success in achieving long-term remission in two previous cases of HIV-1 patients experiencing leukemia: the “London patient” and the “Berlin patient”. In the Nature study, the 53-year-old patient received CR5Δ32/Δ32 HSCT in February 2013, and underwent chemotherapy treatment and infusions of donor lymphocytes. Initially after the stem cell therapy, ART was continued, though HIV-1 was undetectable in the patient’s blood. ART was stopped in November 2018 to explore whether the infection returned, with the patient’s permission. They have remained in remission ever since.
“This study shows that transplanting blood stem cells from an HIV-resistant donor has led to the development of a new, HIV-resistant immune system in an HIV+ patient. By following the patient for a decade after transplantation, researchers have shown that their HIV resistant immune system is stable and working well, and that the patient remains healthy after stopping antiviral therapy for 4-years,” says Limnios.
“This third case of HIV-1 cure after allogeneic CCR5Δ32/Δ32 HSCT provides detailed information on the virological and immunological signature before and after ATI and generates valuable insights that will hopefully guide future cure strategies,” Jensen and colleagues write.
The team’s use of the word “hopeful” is important here; HSCT is a high-risk procedure that is used in some cases of cancer, based on careful consideration from both the clinician and the patient. Rejection of the transplant can have serious adverse side effects. Therefore, it’s unlikely that HSCT could be rolled out for all HIV-1 patients, even those with leukemia.
However, we’re now living in an era where stem cell and gene editing technologies (such as CRISPR-Cas9) are advancing at an unprecedented pace. “Rather than harvesting stem cells from donors with rare and special genetics, they [stem cell therapies] can be created in specialized facilities under highly controlled conditions, and in greater quantities,” says Limnios.
In the Nature paper, Jensen and colleagues suggest that the approach adopted in this study could be expanded by introducing the CCR5Δ32 mutation into stem cell grafts using gene therapy approaches. This, they say, may carry promise for developing an HIV-1 cure outside the treatment of blood cancers.
Reference: Jensen BEO, Knops E, Cords L, et al. In-depth virological and immunological characterization of HIV-1 cure after CCR5Δ32/Δ32 allogeneic hematopoietic stem cell transplantation. Nat Med. 2023. doi:10.1038/s41591-023-02213-x.