Ellen Phiddian
Another patient is free from HIV, after a stem cell transplant used to treat leukemia also suppressed the virus.
The patient, a 53-year-old male, was previously HIV-positive but has had undetectable levels of the virus in his blood for nine years. He stopped using anti-retroviral treatments four years ago, and the HIV hasn’t resurfaced.
The treatment used – hematopoietic stem cell transplantation, or HSCT – has been successful at suppressing HIV in two other people, referred to as the ‘London patient’ and the ‘Berlin patient’.
This patient, also called the ‘Düsseldorf patient’, was first tentatively announced as “cured” of HIV in 2019, shortly after stopping anti-retroviral treatments.
With four years’ more data, the international team of researchers has now confidently described his long-term remission in a Nature Medicine paper with the headline: “In-depth virological and immunological characterization of HIV-1 cure after CCR5Δ32/Δ32 allogeneic hematopoietic stem cell transplantation”.
Like the Berlin and London patients, the Düsseldorf patient had HIV-1: the most common type of HIV, accounting for more than 90% of infections. He was diagnosed with acute myeloid leukemia in January 2011, and received a stem cell and immune cell transplant from a donor in February 2013, alongside chemotherapy.
Crucially, the stem cells from this donor had a specific property: they’re called CR5Δ32/Δ32 hematopoietic stem cells, and they’re HIV-resistant.
Dr Ioannis Jason Limnios, from Bond University’s Clem Jones Centre for Regenerative Medicine, who was not involved in the research, says it’s “exciting progress in the fight against AIDS”.
“During the pandemic, the public learned that viruses use special ‘door handles’ called receptors to get into our cells. Just as COVID-19 uses the ACE-2 receptor to infect cells of the lungs and other tissues, HIV uses a receptor called CCR5 to infect cells of the immune system,” explains Limnios.
“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.
“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-positive 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 four years.”
The patient gave informed consent for ceasing anti-retroviral therapy in 2018. After this, the researchers still couldn’t see HIV in his blood cells, or any indicators from his immune system that the virus was provoking a reaction there.
There were, however, a few trace amounts of HIV in the patient’s tissue samples. When the researchers tested these tiny amounts of HIV in mice, they couldn’t get the virus to spread.
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While this is promising, Limnios says that “it’s not yet clear if type of therapy is a life-long ‘cure,’ and the risk of passing on HIV, whilst extremely low, will never be zero using this therapy alone”.
The researchers also point out that, for the moment, HSCT is a high-risk procedure, and only an option for some people with both HIV-1 and life-threatening blood cancers.
Limnios adds that innovations in gene editing, like CRISPR, means we no longer need rely on rare, HIV-resistant stem cell donors to treat these patients.
A couple of other people who had HIV have gone into remission after receiving other clinical treatments, like immune therapies.