Development of a vaccine for the prevention of AIDS, a critical appraisal.

The pathogenesis and clinical expression of HIV-1 infection in humans is considered in terms of classical pathogenetic studies of viral infections for which successful vaccines have been produced. The unique features of HIV pathogenesis are defined, and gaps in knowledge identified as a framework for considering designs for immune intervention. Envelope-derived candidate vaccines have been used in immunization and challenge experiments in SIV/macaque or HIV/chimpanzee models, presented either as vaccinia recombinant vectors or as subunits, singly or in sequence. These studies have been paralleled by clinical trials for safety and immunogenicity in seronegative individuals. Data generated will permit comparison of immune responses to specific antigens and delivery systems in animal models and in humans. In limited studies conducted under optimized conditions, non-human primates have been protected against virus challenge when immunized with some candidate vaccines or following passive transfer of high-titred antibody. Consideration of current information suggests that in order to prevent HIV infection it may be necessary to devise new strategies capable of inducing and maintaining high threshold titres of biologically relevant antibody as well as persistence of active cytotoxic T cells recognizing multiple epitopes.