Diagnostic and prognostic potential of a competitive enzyme-linked immunosorbent assay for leishmaniasis in India

Leishmania donovani species-specific monoclonal antibody (monoclonal antibo dy D2) was evaluated for its diagnostic and prognostic potential by a compe titive enzyme-linked immunosorbent assay (C-ELISA) in sera from Indian pati ents with visceral leishmaniasis (VL) and seven patients with post-kala-aza r dermal leishmaniasis (PKDL). These results were compared with those obtai ned by microscopy with Giemsa-stained tissue smears and a direct enzyme-lin ked immunosorbent assay (direct ELISA) with crude parasite antigen. Of 121 patients with clinically diagnosed VL examined, 103 (85.1%) were positive a nd 11 (9.1%) were negative by all three methods. An additional 7 (5.8%) who were negative by microscopy were positive by both C-ELISA and direct ELISA , Seven PKDL patients were also examined and were found to be positive by a ll three methods. Analysis of the chemotherapeutic response to sodium antim ony gluconate of these 110 serologically positive VL patients showed that 5 7 (51.8%) were drug responsive and 53 (48.2%) were drug resistant. The C-EL ISA with sera from 20 longitudinally monitored VL patients before and after chemotherapy showed a significant decrease in percent inhibition of monocl onal antibody D2 in drug-responsive patients. However, in drug-unresponsive patients, the percent inhibition of D2 was unchanged or was slightly incre ased, Our results therefore indicate (i) the applicability of L. donovani s pecies-specific monoclonal antibody D2 for sensitive and specific serodiagn osis by C-ELISA, (ii) that the C-ELISA is more sensitive than microscopy, e specially for early diagnosis, (iii) that L, donovani is still the main cau sative agent of VL, irrespective of the chemotherapeutic response, and (iv) that the C-ELISA can be used to evaluate the success of drug treatment.