Leishmaniasis: Current status of vaccine development

Leishmaniae are obligatory intracellular protozoa in mononuclear phagocytes . They cause a spectrum of diseases, ranging in seventy from spontaneously healing skin lesions to fatal visceral disease. Worldwide, there are 2 mill ion new cases each year and 1/10 of the world's population is at risk of in fection. To date, there are no vaccines against leishmaniasis and control m easures rely on chemotherapy to alleviate disease and on vector control to reduce transmission. However, a major vaccine development program aimed ini tially at cutaneous leishmaniasis is under way. Studies in animal models an d humans are evaluating the potential of genetically modified live attenuat ed vaccines, as well as a variety of recombinant antigens or the DNA encodi ng them. The program also focuses on new adjuvants, including cytokines, an d delivery systems to target the T helper type 1 immune responses required for the elimination of this intracellular organism. The availability, in th e near future, of the DNA sequences of the human and Leishmania genomes wil l extend the vaccine program. New vaccine candidates such as parasite virul ence factors will be identified. Host susceptibility genes will be mapped t o allow the vaccine to be targeted to the population most in need of protec tion.