Antibodies Could Prevent HIV Transmission

Antibodies that prevent some HIV-positive people from progressing to AIDS could be used to develop microbicides or a vaccine to prevent HIV-negative people from contracting the virus, according to research presented Thursday at the XVII INTERNATIOAL AIDS CONFERENCE in Mexico City, the Washington Post reports.

According to the research, conducted by researchers at theUniversitity of Texas medical school , some long-term survivors of HIV have antibodies against an HIV protein called gp120. The antibodies, called "catalytic antibodies," attack an area on the outer shell of HIV where the virus binds to immune system cells, preventing the virus from entering the cells. According to the researchers, the antibodies are present in people with lupus, and "researchers noticed years ago that HIV infection rarely occurred in them," according to the Post. "One hypothesis is that they mount an immune response that protected them," Stephanie Planque, a student at UTMS who presented the research at the AIDS conference, said. Lupus patients' immune systems malfunction and produce a number of "unusual" antibodies, the Post reports.

HIV-positive people make separate antibodies against gp120, but they usually are not strong enough to stop or slow the progression of the virus, according to the Post. Previous research on a vaccine using the protein did not stop or slow HIV progression.

The researchers, led by Sudhir Paul at UTMS, found that gp120 is part of a 13-unit stretch of proteins located where the virus attaches to immune cells. Gp120 is hidden by the other proteins, making it more difficult for the immune system to make antibodies against it, according to the research.

Planque screened antibodies made by lupus patients to determine if any produced catalytic activity against HIV's 13-unit protein stretch, which includes gp120. She found that antibodies derived from the lupus patients killed five strains of HIV.

According to the researchers, the findings could be used to find a way to prompt the immune system to make its own supply of antibodies against gp120 before being exposed to the virus. However, the "road is long before we reach that point," Planque said. The researchers are currently researching strategies to "presen[t]" the protein stretch to the immune system that stimulates catalytic antibodies more effectively than what happens naturally. If such an approach proves successful, it could produce a useful vaccine, the Post reports.

Although drugs containing antibodies are expensive, a microbicide containing catalytic antibodies might be affordable for people in developing countries because only a small quantity would be needed to prevent HIV transmission during sexual contact, the researchers said. In addition, the protective benefit would only need to last hours, not days or weeks. According to the Post, the "broad effect" of catalytic antibodies is "important" and any microbicide or vaccine developed from the antibodies would need to prevent all HIV strains to be "useful" (Brown, Washington Post, 8/8).