AN ENZYME-LINKED-IMMUNOSORBENT-ASSAY USING DETERGENT-SOLUBLE PLASMODIUM-VIVAX ANTIGEN FOR SEROEPIDEMIOLOGICAL SURVEYS

An enzyme-linked immunosorbent assay (ELISA) to detect antibodies to Plasmodium vivax parasites in human sera was developed using P vivax-infected erythrocytes from local malarious patients in southern Mexico. Infected cells were concentrated using a discontinuous Percoll(R) gradient and detergent-soluble antigens obtained using Triton(R) X100. The use of detergent and the addition of protease inhibitors to the antigen preparation ensured high sensitivity and reproducibility of the assay. No cross reactions were observed in sera immune to other protozoan, helmintic and bacterial infections, although some cross reactivity was seen in P. falciparum immune sera. A strong correlation between antibody titre values obtained by the ELISA and those obtained using an IFAT was observed. In a small field trial, carried out in a village where malaria transmission occurs, both ELISA and IFAT produced similar seroepidemiological profiles with regard to frequency of positive antibody titres and their distribution among the different age groups of the population.