LIVE ATTENUATED VACCINES
The observation that NEF strains could offer protection against challenge with pathogenic SIV infections in rhesus macaques served as the model for the use of this type of attenuated vaccine. However, this mutant’s drawback is that it produces a lifelong persistent viral infection in the host. The positive side is that although the attenuated vaccine does not prevent infection with a wild-type SIV infection, it does prevent that infection from going on to produce the disease AIDS. Thus, this approach does not appear feasible now. However, what is being explored is the nature of the protective immune response in these monkeys after infection with the attenuated virus.