[Development of an AIDS vaccine: status report]

After over 20 years of research and development (R&D) and more than 85 clinical trials using various candidate vaccines, there has been little progress in research for a vaccine against HIV/AIDS. This disappointing result raises serious doubts as to whether an effective HIV/AIDS vaccine will be available within a reasonable time frame. There are three main obstacles. The first is that the virus promptly enters into the genome of effector memory T-cells that then constitute an infection reservoir from which the virus cannot be dislodged. The second obstacle involves the genetic hyper-variability of the virus that can easily dodge host immune defenses by mutating. The third obstacle is that we are still unable to induce antibodies able to neutralize wild strains of the virus and block infection early. Current vaccines are designed to induce cellular immune responses - mostly of the CD8+ cytotoxic T cell (CTL) type - in the hope of limiting the clinical consequences of infection by reducing the rate of virus multiplication and decreasing virus load in recently infected persons. This strategy has led to development of numerous live attenuated vaccines using a wide variety of viral or bacterial vectors. These vaccines are currently being tested either singly or in various prime-boost combinations using several of these vaccines or DNA vaccines. The efficacy of these vaccination techniques in humans remains to be determined.