The Enzyme-Linked Immunosorbent Assay (Elisa) for Malaria

I. The Use of In Vitro-Cultured Plasmodium falciparum as Antigen

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  • Bureau of Tropical Diseases, Center for Disease Control, Public Health Service, U.S. Department of Health, Education, and Welfare, Atlanta, Georgia 30333

Using the Panama II strain of Plasmodium falciparum obtained from continuous in vitro culture as antigen, the micro enzyme-linked immunosorbent assay (ELISA) was used to test serum samples from 50 persons from the southeastern United States and serum specimens collected weekly from four non-immune and nine semi-immune patients infected with P. falciparum. None of the 50 sera from the United States had ELISA antibody titers ⩾1:80. The nine semi-immune patients had rapid ELISA antibody responses (titers ⩾ 1:2560) following patent parasitemia. ELISA titers remained elevated despite disappearance of patent parasitemia, and declined gradually following curative antimalarial therapy. The ELISA responses observed in the four non-immune patients were more variable, though positive titers appeared rapidlly with patent parasitemia. Maximum titers were lower than those observed in semi-immune patients. These results demonstrate that P. falciparum obtained from continuous in vitro culture is an excellent antigen for the micro-ELISA test for malaria. However, further assessments of the ELISA are needed to identify the conditions associated with positive responses.