THE LUCKY FEW: WHY SOME WOMEN ARE IMMUNE TO HIV

Why do some women avoid infection with HIV, despite having had years of unprotected sex with infected partners? According to researchers at UMDNJ-New Jersey Medical School (NJMS), it's because they have key immune cell responses that are working to block the virus from multiplying and infecting them.

In the six-year study, researchers followed 18 women who were in long-term relationships with infected male partners. All the women remained healthy except for one, who contracted the virus after nine years of exposure. In 13 of the women, researchers detected the presence of a potentially effective defense, responses of two types of lymphocytes: CD8 "suppressor" cells or CD4 "helper" cells. These cells energize the immune system and act against invading organisms. The behavior of these lymphocytes could be used to test the effectiveness of new vaccines against the disease, says Joan Skurnick, PhD, an associate professor of preventive medicine and community health at NJMS and co-author of the study.

Four other women who remained HIV negative had no unusual immune cell responses, and researchers did not identify why they did not become infected. There could be two possible reasons: one, the women may be genetically primed to react to the virus defensively; and two, their partners may have had strong lymphocyte responses themselves, which might weaken the virus and help block infection.

The study does not conclude that any of the women have lifelong immunity from HIV. "No one should have unprotected sex with an HIV-infected person, and this study does not alter that message. We can't conclude that the women are risk-free," says Skurnick.

Donald Louria, MD, chair emeritus of preventive medicine, Paul Palumbo, MD, professor, department of pediatrics, and Thomas M. Denny, assistant professor, pathology, laboratory medicine and pediatrics, all at NJMS, were co-authors of the study, which was published in the February 15, 2002 issue of the Journal of Infectious Diseases.