Patients with HIV who get vaccinated with a disabled version of the virus can, in many cases, fight the real one to a draw. A new study shows that injecting heat-inactivated HIV can awaken immune protection in some patients, limiting their need for drugs for weeks or months. While the effects appear temporary, the approach might eventually lead to a way to control HIV over the long-term.
The immune system is understaffed in the fight against HIV, largely because the virus targets the very immune T cells that coordinate defence against the virus. Efforts to alert these and other immune forces to the presence of HIV in already infected patients through vaccination have produced mixed results.
The new study, published January 2 in Science Translational Medicine, reports on an approach that can lower virus levels substantially. Using blood samples from 36 patients, researchers extracted each person’s HIV and a sampling of immune system cells called dendritic cells. For 22 randomly selected patients, the scientists blasted the HIV with heat to inactivate it. The patients then received as a vaccine their own dendritic cells and inactivated HIV. Over 12 weeks, virus levels plummeted by at least 90 percent in 12 of the 22 volunteers.
The result suggests that dendritic cells toting the inactivated HIV can direct an immune onslaught toward the live virus circulating in patients, says study co-author Felipe Garcia, an infectious disease physician at the University of Barcelona. Other patients in the study who received their own unchanged HIV and dendritic cells as a control group showed little benefit.
In most of the treated patients, the newfound immunity to HIV faded over time and virus levels rose. After 48 weeks, only three who got the therapeutic vaccine still maintained the 90 percent drop in virus levels.
All the patients had been taking standard antiretroviral therapy beforehand. Previous attempts at using a vaccine to gin up an immune response in patients who hadn’t been taking the standard medications failed. “It is likely that the person’s immune system is already damaged, and so they cannot mount a sufficiently efficient functional antiviral response” to a vaccine, says Anders Fomsgaard, a physician at Statens Serum Institute in Copenhagen. “It may be more optimal to vaccinate during antiretroviral therapy.”
Formsgaard says the reduction in virus levels seen in the new study is promising. His team is trying to identify viral particles that elicit the best response when confronted by immune forces.
Even if a therapeutic vaccine falls short of eradicating HIV from the body completely, it would still be beneficial if it proves to be long-lasting, Garcia says. Knocking the virus down to extremely low levels would mean many patients wouldn’t need drugs, wouldn’t show disease symptoms and wouldn’t be likely to transmit HIV to others. There is an example of such people already – “elite controllers,” the less than 1 percent of people who remain infected with HIV for years but whose immune systems suppress the virus.