A diagnostic ELISA for visceral leishmaniasis, based on antigen from media conditioned by Leishmania donovani promastigotes.

Leishmania donovani promastigotes were cultured in a protein-free medium for 3-5 days and the spent medium used to prepare antibody-detection ELISA plates. When the plates were used to test 29 Kenyan and 16 Nepalese patients with visceral leishmaniasis (VL; kala-azar), all the sera collected at diagnosis were found to have high levels of parasite-specific IgG. The levels of these antibodies dropped 6-12 months post-initiation of antileishmanial therapy in all but one of the patients. Although the levels in sera from 59% of the treated patients fell to those measured in sera from healthy controls, those in sera from 17% of the patients did not drop below those seen at diagnosis. The antigen used did not cross-react with sera from patients with parasitological diagnosis of malaria, filariasis, African trypanosomiasis or echinococcosis. Antibodies to antigens in the spent medium were detected, by western blot, in all the sera from Nepalese patients with VL. Promastigote-conditioned media could be the source of cheap antigen for the immunodiagnosis of leishmaniasis.