Gene Therapy for Controlling HIV Shows Early Promise
Small study hints treatment could someday help patients fight AIDS virus without drugs
No one knows whether the technology used in this study will eventually offer a functional cure. But Levine said there were "hints" that, with further refinement, it could.
One month after the T-cell infusion, half of the study patients stopped their regular HIV drug regimen for up to 12 weeks. Initially, the patients' "viral load" increased, but for the four who were able to stay off their medication for the full 12 weeks, the viral load declined toward the end.
There were also signs that some of the modified T-cells were resistant to HIV: When patients stopped their medications, the infused T-cells did decline in number -- but not to the extent that their unmodified T-cells did.
HIV researchers have been studying the CCR5 protein for years. It's long been known, Levine said, that the protein allows HIV to gain entry into cells. And people who have a particular mutation in both copies of their CCR5 gene (inherited from both parents) are protected from HIV infection.
CCR5 research has gained momentum in the past several years -- particularly after the famous case of the "Berlin patient," who is considered the first person to be cured of HIV.
That patient, whose real name is Timothy Ray Brown, was HIV-positive back in 2007, when he underwent a bone marrow transplant to treat leukemia. His bone marrow donor carried two copies of the CCR5 mutation, and the transplant not only cured his cancer, but also knocked his HIV levels below the threshold of detection. He has been off of HIV drugs since 2008.
For the current study, Levine and his colleagues tried to mimic that CCR5 mutation using what's called a zinc-finger nuclease -- which is basically an artificial enzyme that can snip DNA at a specific site.
That effectively knocked out the CCR5 gene in 11 percent to 28 percent of patients' T-cells before they were re-infused.
Levine said one of the more immediate goals now is to make the process more efficient. Right now, the technology knocks out both copies of CCR5 in some cells, but only one copy in others.