Evaluation of the micro enzyme-linked immunosorbent assay (ELISA) for antibodies in American visceral leishmaniasis: antigen selection for detection of infection-specific responses.

This study was designed to evaluate the ELISA for diagnosis of American visceral leishmaniasis (AVL) using antigen prepared from different Leishmania isolates and from a strain of Trypanosoma cruzi. Two Leishmania donovani chagasi isolates from Bahia and Maranhão (both states of northern Brazil), one L. donovani from Sudan, one L. mexicana amazonensis isolate, and one T. cruzi isolate were used. A total of 375 sera were tested, including 119 from AVL patients, 96 from nonleishmaniasis hospitalized patients, 20 from healthy persons, 30 from patients with mucocutaneous leishmaniasis, 28 from patients with Chagas' disease, 20 from patients with tuberculosis, 21 from leprosy patients, 27 from schistosomiasis patients and 14 from patients with systemic mycoses. The antigens prepared from L. d. chagasi (Bahia) and L. m. amazonensis showed the highest sensitivity (98% and 99%, respectively) for detecting antibodies in sera from AVL patients. However, the specificity of L. d. chagasi (Bahia) antigen was better than that of L. m. amazonensis (96% vs. 86%). Comparison among the three L. donovani isolates demonstrated that the antigen prepared with the isolate from the same area where the sera originated yielded higher mean absorbance than the others. By using spectrophotometric absorbance values it was possible to use a single dilution of serum (between 1/100-1/400) since a clear separation was seen between AVL patients and controls. No patients with the other diseases who were tested gave positive results. We suggest that ELISA can be a very convenient, sensitive, and specific test for diagnosis of AVL when soluble antigen, preferably from an isolate from the test area, is used.