AIDS vaccines: concepts and first trials

Two categories of obstacles impede the development of an AIDS vaccine. Virological obstacles are due to lentiviruses, to which HIV and SIV belong, having developed strategies to escape the immune responses of infected hosts and establish persistent infection. These strategies are based on two mechanisms: latency corresponding to restriction of viral gene expression that renders the virus antigenically invisible, and variability, the consequences of which are antigenic shift and permanent adaptation to selective pressures. Immunological obstacles are linked to a central unanswered question: is the global effect of the immune response against HIV beneficial or deleterious to the host and, if beneficial, is it able to resist the virally induced immunosuppression? These obstacles are difficult to overcome theoretically and empirical trials are necessary; live attenuated or recombinant vaccines, inactivated vaccines, subunit vaccines, anti-idiotypes, and synthetic and chimeric vaccines are currently being tested in animals or in humans. At present, promising results have been obtained with inactivated virus vaccines with the use of macaque monkeys infected by SIV as a model.