To evaluate the effectiveness of vaccine protection from infected cells from another individual of the same species, vaccinated rhesus macaques (Macaca mulatta) were challenged with peripheral blood mononuclear cells from another animal diagnosed with acquired immune deficiency syndrome (AIDS). Half of the simian immunodeficiency virus (SIV)-vaccinated animals challenged were protected, whereas unprotected vaccinates progressed as rapidly to AIDS. Protection was unrelated to either total antibody titers to human cells, used in the production of the vaccine, to HLA antibodies or to virus neutralizing activity. However, analysis of the serotype of each animal revealed that all animals protected against cell-associated virus challenge were those which were SIV vaccinated and which shared a particular major histocompatibility complex (MHC) class I allele (Mamu-A26) with the donor of the infected cells. Cytotoxic T lymphocytes (CTL) specific for SIV envelope protein were detected in three of four protected animals vs. one of four unprotected animals, suggesting a possible role of MHC class I-restricted CTL in protection from infected blood cells. These findings have possible implications for the design of vaccines for intracellular pathogens such as human immunodeficiency virus (HIV).

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