Scientists have found that even small differences in theprotein coats of the AIDS virus can determine if an antibodyprevents infection by the virus, has no effect or evenstimulates it.

The finding has implications for vaccine designers, whoapparently run the risk of perpetuating rather than halting HIVinfection.

Srisakul Kliks, assistant research virologist at the Universityof California, San Francisco, Cancer Research Institute,presented the results at Monday's session of the SeventhInternational Conference on AIDS in Florence, Italy.

In cultures, the UCSF team found that human antibodies aimedat the V3 loop of the HIV protein envelope could neutralize onestrain while spurring growth in another. The three strainstested differed by only one amino acid in the V3 region.

While the team doesn't know if the lab results would hold truein the human body, Kliks said the study underlines theimportance of careful vaccine design to avoid using antibodiesthat could end up helping certain HIV strains proliferate.

"This isn't encouraging," said Dr. Jay Levy, UCSF professor ofmedicine and a researcher at the institute.

Kliks added that other regions of the HIV envelope may alsoplay an important role in viral sensitivity to antibodies.

In another report to the conference, researchers reported thatAZT, the only AIDS drug approved for use in the United States,combined with another anti-viral compound called ddc resultedin improved T cell levels in patients compared to patientsusing only AZT. The combination therapy also sustained anincreased T cell level for more than a year. By comparison, Tcells in the AZT-only patients receded within six months. --Karen Bernstein

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