Evaluation of Promastigote and Amastigote Antigens in the Indirect Fluorescent Antibody Test for American Cutaneous Leishmaniasis

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  • Departments of Immunology and Parasitology, Walter Reed Army Institute of Research, Washington, D.C. 20307

Leishmania braziliensis panamensis promastigotes, temperature-induced in vitro-cultivated amastigotes, Vero cell-derived amastigotes, and rodent lesion-derived amastigotes were evaluated as antigens in the indirect immunofluorescent antibody (IFA) test for American cutaneous leishmaniasis. Test sensitivity was determined using sera from 34 U.S. soldiers with leishmaniasis diagnosed by demonstrating parasites in their skin lesions. Sera were collected from 3 to 24 months after exposure to Leishmania. Positive IFA reactions among patient sera were 82% with promastigotes or lesion amastigotes, 79% with in vitro amastigotes, and 76% with Vero cell amastigotes (P = N.S.). Positive titers ranged from 1: 8 to 1:128 using all antigens. Test specificity was determined with 30 sera from healthy individuals. False positive reactions ranged from 0–5% depending on the antigen and all titers were ⩽1:8. Test cross-reactivity was assessed with 47 sera from patients with other diseases. Depending on the antigen, cross-reactions occurred with sera from patients with Chagas' disease, lupus erythematosus, malaria, toxoplasmosis and amebiasis. None of the antigens cross-reacted with sera from patients with viral hepatitis, coccidioidomycosis, syphillis, schistosomiasis, and trichinosis. In replicate experiments, 99–100% of the sera varied no more than ±1 titer dilution. As sensitivity, specificity, cross-reactivity, and reproducibility of the four antigens were statistically similar, promastigotes, which can be easily and economically cultured in large numbers in vitro are recommended for use in the IFA test for American cutaneous leishmaniasis.