Sign of HIV Immunity Reported; Protective Responses Suspected in Two Studies

Some people may be producing immune responses that protect them from HIV infection, according to two reports presented Monday at the 14th International AIDS Conference. The reports require confirmation, but at first glance were signs that it is possible to build immunity against the virus -- long a goal of vaccine research.

Dr. Anthony Kebba of the Uganda Virus Research Institute in Entebbe described the case of eight couples he has studied. All involved husbands infected for many years with HIV and wives who have never contracted the virus. The men had what are considered active infections, with a viral load high enough to pose considerable risk of infection to the wives. Kebba's team examined samples of tissue taken from the wives' vaginas after three days of sexual abstinence. In five of the women, vaginal tissue samples were found to contain antibodies. In test tubes, those antibodies attacked HIV. "Our results confirm that heterosexual exposure to the virus does not always lead to infection," Kebba said.

A Pasteur Institute team led by Dr. X. Truong in Ho Chi Minh City found similar results in long-term Vietnamese intravenous drug abusers. She analyzed blood samples from 45 IV drug users who had been injecting narcotics for more than ten years, but who had never become infected with HIV, even though they had contracted other infections: 82 percent had hepatitis B; 100 percent had hepatitis C; and 80 percent had the rare HTLV cancer virus.

When Truong compared their immune systems with those of 50 healthy individuals who did not inject drugs, she found that even when she drowned the cells of the drug users with HIV, they did not become infected. She found that the drug users were making large numbers of immune system cells called CD8 suppressor cells, which aggressively destroyed any cell infected by HIV. One researcher pleased with the results -- and their implication for vaccine development -- was Dr. Jay Levy of the University of California-San Francisco. The findings confirm his long-held position that CD8 cells secrete potent chemicals that control or destroy HIV.

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