A vaccine pairing a genetically altered, harmless canarypox virus and a genetically engineered piece of the HIV protein coat induces immune system activity against laboratory strains of HIV better than either vaccine alone, according to a School of Public Health researcher.

"The results of tests on 131 people at low risk for HIV infection convinced us we should continue testing two-vaccine combinations," says Mary Lou Clements-Mann, professor of international health and lead author of a report on the multicenter trial published in the May 1998 issue of The Journal of Infectious Diseases. The study was supported by the National Institutes of Health.

The researchers are now conducting further trials in which canarypox vaccines with genes for HIV envelope protein--a piece of the outside covering of the virus--and other HIV gene products are given together or in sequence. These vaccines also are being tested in volunteers at high risk for HIV infection due to unsafe sex or other behaviors, according to Clements-Mann.

The combination vaccines stimulated anti-HIV immune system activity in volunteers better than either vaccine alone, sparking production of both anti-HIV antibodies and CD8+ cytotoxic T lymphocytes, white blood cells that destroy cells infected with the HIV virus, says Clements-Mann.

The multicenter team tested the two-vaccine combination-- called ALVAC-gp160/rpg120--because previous research suggested that a successful AIDS vaccine might need to induce both antibodies and CD8+ CTLs to eliminate HIV from the body. Past vaccines made with altered live vaccinia viruses expressing HIV proteins could potentially spread from person to person and possibly harm persons with AIDS, according to Clements-Mann. But the genetically engineered canarypox viruses do not multiply in humans, she says. "Therefore, we believe these vaccines will be safe and not be transmissible to people vaccine volunteers are in contact with."