A handful of people with HIV have been cured after receiving HIV-resistant stem cells – but a man who received non-resistant stem cells is also now HIV-free
An HIV-infected human cell STEVE GSCHMEISSNER/SCIENCE PHOTO LIBRARY
A man has become the seventh person to be left HIV-free after receiving a stem cell transplant to treat blood cancer. Significantly, he is also the second of the seven who received stem cells that were not actually resistant to the virus, strengthening the case that HIV-resistant cells may not be necessary for an HIV cure.
“Seeing that a cure is possible without this resistance gives us more options for curing HIV,” says Christian Gaebler at the Free University of Berlin.
Five people have previously become free of HIV after receiving stem cells from donors who carried a mutation in both copies of a gene encoding a protein called CCR5, which HIV uses to infect immune cells. This led scientists to conclude that having two copies of the mutation, which completely removes CCR5 from immune cells, was crucial for curing HIV. “The belief was that using these HIV-resistant stem cells was essential,” says Gaebler.
Advertisement
But last year a sixth person – known as the “Geneva patient” – was declared free of the virus for more than two years after receiving stem cells without the CCR5 mutation, suggesting CCR5 isn’t the whole story – although many scientists think the roughly two-year virus-free period isn’t quite long enough to show they were actually cured, says Gaebler.
The latest case strengthens the idea that the Geneva patient has been cured. It involves a man who, in October 2015, received stem cells to treat leukaemia, a type of blood cancer where immune cells grow uncontrollably. The man, who was aged 51 at the time, had HIV. During his treatment, he was given chemotherapy to destroy the vast majority of his immune cells, making room for the donor stem cells to produce a healthy immune system.
Free newsletter Sign up to Health Check Expert insight and news on scientific developments in health, nutrition and fitness, every Saturday. Sign up to newsletter
Ideally, the man would have received HIV-resistant stem cells, but these weren’t available, so doctors used cells that carried one typical and one mutated copy of the CCR5 gene. At the time, the man was taking a standard HIV therapy called antiretroviral therapy (ART), a combination of drugs that suppress the virus to undetectable levels, meaning it can’t be passed on to other people – and reducing the risk that the donor cells would be infected.
... continue reading