Secreted antigens of the amastigote and promastigote forms of Leishmania infantum inducing a humoral response in humans and dogs

To study the antigens secreted by promastigote and amastigote forms of leis hmania infantum which are able to induce a humoral response in human patien ts and dogs, we have carried out immunoprecipitation assays with different supernatants of in vitro cultured parasites, metabolically labelled with [S -35]methionine, using serum samples from human patients and dogs, in additi on, some metabolic labelling experiments were performed daily during the in vitro culture parasite's life cycle to follow the time course excretion-se cretion of parasitic antigens. The results demonstrated that the two differ ent hosts developed an antibody response against secreted antigens of both stages of Leishmania infantum. Nevertheless, the humoral response directed against the excreted secreted antigens of the promastigote forms was qualit atively and quantitatively different when we compare the human and the dog immune responses. On the other hand, when the excreted-secreted antigens of the amastigote forms are immunoprecipitated with either human or canine im mune serum, the humoral response is similar. In addition, the time course s tudy showed that excretion-secretion of antigens was qualitatively and quan titatively modulated during the parasitic in vitro life cycle.