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Women Who Stayed HIV-Free StudiedTRENTON, N.J. (AP) - For years, more than a dozen women have intrigued AIDS (news - web sites) scientists: They have remained HIV (news - web sites) free despite having frequent, unprotected sex with an infected partner.
Now researchers at the University of Medicine and Dentistry of New Jersey think they can help explain why. The women, they say, have immune systems behaving as they were vaccinated against AIDS.
Their study found that in most of the women, key immune cells worked in various ways to block the HIV virus (news - web sites) from multiplying in their bodies and infecting them, information that could help create an AIDS vaccine. But the researchers and other AIDS experts stress that the conclusions reached in the study shouldn't be interpreted to mean that sex without a condoms is safe for anyone. "If people have unprotected sex with someone who is HIV-positive, they do so at their own peril," warned lead researcher Dr. Donald B. Louria, of the university's Department of Preventive Medicine and Community Health. Louria noted that of the 18 women in the study, one was infected with HIV after nine years of frequent, unprotected sex — despite warnings from health workers against it. Many researchers have been studying the tiny group of people who mysteriously have not become infected with the virus despite long-term, unprotected exposure. Previous studies covered one or two immune factors, with similar results, but this study was the most comprehensive, said Susan Plaeger of the Division of AIDS at the National Institute of Allergy and Infectious Diseases (news - web sites). The 17 uninfected women had unprotected sex with an HIV-positive partner for periods ranging from one year to 11 years dating as far back as the mid-1980s. All but five were persuaded to stop doing so during the study, which included twice-a-year tests of the women's HIV status from 1995 through 2000. Tests on their blood focused on two types of immune cells, CD8 and CD4 cells, which kill invading organisms and rev up the rest of the immune system. HIV normally invades and destroys the CD4 cells, gradually disabling the immune system and leaving the person susceptible to other infections. The CD8 cells and CD4 cells separately were mixed with HIV proteins in laboratory dishes, mimicking how they would interact in a person's body, and researchers watched for reactions. In many samples, the CD4 cells rapidly reproduced, as if stimulating the rest of the immune system, and the CD8 cells or two different substances they produced stopped the HIV virus from reproducing. The team had expected to find one immune response protecting the women from HIV infection, but instead found all four types of resistance spread among 13 of the 17 women. "Thirteen of them had at least one immune-type response that was stronger than what one would expect from an unexposed person," said Joan H. Skurnick, associate professor of preventive medicine and community health at the university's New Jersey Medical School in Newark. One woman had all four responses. The other four women, and the 18th woman who eventually was infected, had none of those defenses. Louria said the researchers also found abnormally high levels of CD8 cells in the women's partners, which appeared to be lowering chances of transmitting the HIV virus. "This essentially backs up a lot of other data that indicates CD8 cells (and CD4 cells) are important as a protective mechanism against HIV," Plaeger said. The study is published in the February issue of the Journal of Infectious Diseases. Dr. Timothy Babinchak, director of clinical research on infectious diseases at Thomas Jefferson University Hospital in Philadelphia, said the findings should encourage further study with more patients. Besides helping in vaccine development, he said the information might help AIDS doctors identify which people infected with the HIV virus are likely to progress to full-blown AIDS most quickly. |
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