BACKGROUND: The serodiagnosis of visceral leishmaniasis due to Leishmaniadonovani using crude parasite antigen is complicated in many endemic areas by cross-reactions with serumfrom humans infected with other protozoan diseases. The search for pure antigens avoiding such cross-reactionsis in progress. Developing a vaccine against cutaneous leishmaniasis has been much more successful thanagainst visceral leishmaniasis. Immunoprophylactic studies using various combinations of antigens andadjuvants are also in progress, and several strategies are in use, with varying degrees of success. MATERIAL/METHODS:Promastigotes of Leishmania donovani were used. The 78kDa protein was purified by a monoclonal antibodytagged CNBr sepharose CL-4B column. The presence of the protein in both stages of the parasite and inkala-azar patient serum was analyzed by western blotting. ELISA was used for serodiagnosis and isotypeanalysis of antibodies produced in immunized mice. Immunoprophylactic studies were carried out basedon in vitro transformation of amastigotes to promastigotes. RESULTS: The 78 kDa membrane protein, presentin both amastigote and promastigote forms of the parasite, was purified to homogeneity. The protein wasfound to have serodiagnostic potential to detect kala-azar. BALB/c mice immunized with 78kDa proteinrevealed reduction in spleen parasitemia. Isotype profiles of antibodies produced by immunized mice showedincreased production of IgG2a and decreased IgG1 levels. CONCLUSIONS: Our results demonstrated, for thefirst time, the serodiagnostic and immunoprophylactic use of a pure membrane protein isolated from Leishmaniadonovani of Indian origin.

Keywords: Antibodies, Monoclonal, Antibodies, Protozoan, Antigens, Protozoan, Immunoglobulin G, Immunoglobulin Isotypes, Immunoglobulin M, India, Leishmania donovani, Leishmaniasis, Visceral, Membrane Proteins, Molecular Weight, Parasitemia, Protozoan Proteins, Protozoan Vaccines, Vaccination