For the first time, researchers have used a type of gene editing called CRISPR to try to treat a person infected with HIV. They managed to engineer stem cells that are immune to HIV and transplant them into a man living with HIV and leukaemia (a blood cancer). The gene-edited cells survived in the man’s body for more than a year without causing detectable side-effects, but didn’t reduce the amount of HIV in his blood.
The research was inspired by the case of Timothy Ray Brown, the ‘Berlin patient’ who appears to have been cured of HIV after a stem cell transplant from a donor who had a rare genetic mutation. The donor did not have CCR5 receptors (which HIV usually uses to gain entry to a cell) on their immune system cells, making the donor resistant to HIV infection. After the transplant, Brown appears to be resistant to HIV too.
Chinese scientists took stem cells from a normal donor (someone who does not have this genetic mutation) and used gene editing to remove the CCR5 receptors. This was difficult to do and only 18% of the cells were successfully edited.
Their patient was a 27-year-old man who had been diagnosed with HIV and leukaemia and needed a stem cell transplant. After chemotherapy and the transplant, his leukaemia went into remission. The transplant of edited cells does not appear to have done the man any harm, but it has not resulted in a lowering of viral load or a remission of HIV. The man stopped his HIV treatment for a few weeks and his viral load increased rapidly, so he went back onto HIV treatment.
Scientists are excited about this case because the man is doing well more than a year and a half later (there are some concerns about the safety of CRISPR gene editing) and because up to 8% of his stem cells continue to have the CCR5 mutation. This shows that gene-edited cells can persist in the body.
For gene editing to have more impact on HIV, it would need to be possible to engineer a larger number of cells without CCR5 receptors. And for more of them to survive in the body.
But this study provides a proof of concept to inspire researchers working towards an HIV cure.
For more information, read NAM's page 'The search for an HIV cure'.