Basis of HIV resistance suggests new vaccine strategy.

Reports that a study of the immune responses in sex workers in Nairobi, Kenya, revealed that women who remain seronegative for HIV for several years mounted cytotoxic T lymphocyte responses to a different set of epitopes than those who were HIV positive. Trial of a vaccine that includes the seronegative-specific isotopes; Difficulty of developing a vaccine in Africa, because of genetic variability of the virus and the host population; Outlook for another vaccine that is being tested.