In spite of extensive prevention programs, the HIV epidemics is still spreading worldwide, in particularly in developing countries where clade C viruses predominate. WHO estimates that there are 16,000 new cases of HIV infection daily and that 100 M individuals will be infected by the end of the next decade. In spite of its spectacular results in seropositive patients, high-activity antiretroviral therapy (HAART) cannot eradicate the virus and is faced with side-effects, problems of compliance and the emergence of drug-resistant viruses. Furthermore, its prohibitive cost severely limits its use in developing countries. Therefore, the development of a preventive vaccine remains the best strategy to control the HIV-1 epidemics and a public health priority. However, the development of such a vaccine remains a formidable challenge to both the industry and the scientific community (Burton DR, More JP. Why do we not have an HIV vaccine and how can we make one? Nat Med 1998;4:495-8). (C) 1999 Elsevier Science Ltd. All rights reserved.