Gene Therapy for HIV Resistance Succeeds in Trials—But Hold the “Cure” Talk
Earlier this week at a scientific conference in Boston, HIV researchers announced a remarkable success in countering the virus’ drain on the immune system. But this early step is far from a cure.
Why it’s exciting:
Carl June and colleagues tested six male patients who already had HIV and were taking a standard antiviral regimen. Like many HIV patients, the drugs helped them, but their counts of immune cells stayed low. June’s team tested a therapy created by Sangamo BioSciences in Richmond, California, that alters a patient’s actual white blood cells to make them more HIV-resistant.
Researchers removed a sample of CD4+ T cells, the type of immune cells affected by HIV, from each man and used Sangamo’s enzyme to disrupt the CCR5 gene, which encodes a protein that HIV uses to enter CD4+ cells. The engineered cells were then infused back into the patients. Immune-cell counts subsequently rose for five of the six patients who received the therapy. “It’s very exciting,” says John Rossi, a molecular biologist at the City of Hope’s Beckman Research Institute in Duarte, California. “If they did this several times in a given patient, you could establish a high percentage of resistant cells.” [Nature]
The idea came from the “Berlin Patient,” who we’ve written about before at 80beats. He became famous after receiving a donation of bone marrow from someone who carried a mutation in CCR5 that made them resistant to HIV.
Typically when a person with HIV stops therapy even undetectable virus quickly rebounds to very high levels, generally within a few weeks. The doctor and patient waited as the months ticked by, and still no virus reappeared. They came to the conclusion that they had proved their hypothesis; the patient had apparently been cured of HIV. [Scientific American]
Why we shouldn’t get too excited just yet:
The success in these few patients has some docs excited that people could really start to think about an immune system recovery like the Berlin Patient’s. But let’s not get carried away just yet:
“If successful, this probably could have wide application, but going from six patients to an entire epidemic is a ways to go,” said Dr. Michael Horberg, director of HIV/AIDS at Kaiser Permanente Health Plan and vice chair of the HIV Medicine Association. “With other successes we’ve already had, that makes it more promising and people are starting to have a greater vision as to what’s possible.” However, as Kolber pointed out, this trial was what’s known as a phase I trial, which means it was primarily looking at safety, not effectiveness, although investigators do often report on initial effectiveness results at this stage. [HealthDay News]
Dr. Jacob Lalezari of Quest Clinical Research of San Francisco, who led the first test of this procedure, agrees. Though the men in this study saw immune system boosts, just 6 percent of their T-cells carried the anti-HIV mutation. And there are strains of virus that use a different point of entry.
He warned that it would be “way overstated” to suggest that the results so far are a possible cure. “It’s an overreach of the data. There are a lot of people out there with hopes and dreams around the C-word,” so caution is needed. [AP]
Image: Wikimedia / HIV Budding