SAN DIEGO Scientists have taken a big step toward making an effective HIV vaccine, by discovering how the immune systems of some people better resist infection than others.
The resistance is generated by certain “helper” immune cells that act in tandem with other cells in making especially potent antibodies against HIV, the virus that causes AIDS. Increasing the activity of these helper cells should increase the effectiveness of vaccines.
The findings were published Thursday in the journal Immunology. Led by Shane Crotty of the La Jolla Institute for Allergy & Immunology, researchers found that levels of potent “broadly neutralizing” antibodies in HIV-positive people correlated with high levels of helper cells.
Besides the helper cells found in HIV-positive patients, the study found what appears to be their precursor cells in those uninfected. This means it may be possible to make a preventive vaccine, the study said. If the helper cells are stimulated in the infected, a therapeutic vaccine could help them better resist HIV.
The research represents “a really important advance,” said longtime AIDS researcher Anthony Fauci, director of the National Institute of Allergy & Infectious Diseases.
Most HIV vaccine research focused on the antibody-making cells, Fauci said. Relatively little attention was paid to the role of their helpers, Fauci said.
The antibody-making cells belong to a class called B cells. Their helpers are of a kind called T cells. There are many different subcategories of these cells, and knowing which ones to target is vital, Fauci said.
“We have another target to aim our vaccine against,” Fauci said. “How do you get these cells to really maximally respond?”
During the first years of the AIDS epidemic, the human immune system was believed to be incapable of making effective antibodies to HIV. The discovery of broadly neutralizing antibodies several years ago shattered that belief.
But only about 5 percent of HIV-positive people make these antibodies. And most of the time, these broadly neutralizing antibodies don’t stop the disease from progressing.
So researchers have been collecting and studying these antibodies to find which ones work best. They’re also trying to understand what’s different about the immune systems of those making them, and how to make a vaccine that can give the same power to everyone else.
The study will make it easier to watch how broadly neutralizing antibodies develop, said Rowena Johnston, vice president and director of research at amfAR, The Foundation for AIDS Research.
For the study, Crotty invented a blood test to find the helper cells. That’s less invasive than the existing method of performing a biopsy, Johnston said.
“The fact that they can find these (markers) in the blood will really speed along research and make it more efficient,” Johnston said. “They’ll be able to watch in real time how it is that the body makes these broadly neutralizing antibodies, and observe in real time how these broadly neutralizing antibodies affect the virus.”
Observing that interplay will give clues about which properties should be replicated in a vaccine to give the best control, Johnston said. A vaccine producing broadly neutralizing antibodies might be useful to control HIV in the already infected, Johnston said. It might offer a milder alternative to retroviral drugs.