Efficacy of the merozoite surface protein 1 of Plasmodium vivax as an antigen for ELISA to diagnose malaria.

Malaria is still a major health problem in Thailand and its incidence is currently rising in Korea. To identify a useful antigen for the diagnosis of malaria patients, a cDNA expression library from malaria parasites was constructed and screened out immunologically. One clone was selected in view of its predominant reactivity with the patient sera. The recombinant malaria parasite antigen (Pv30) with 27 kDa as a C-terminal His-tag fusion protein that was produced in Escherichia coli was identified through immunoblot analysis. The deduced amino acid sequence had the sequence homology with the merozoite surface protein 1 (MSP1) genes of Plasmodium falciparum and P. yoelii, each by 41% and 42%, respectively. Measurement of serum IgG and IgM antibody to Pv30 by enzyme-linked immunosorbent assay (ELISA) was evaluated as a serodiagnostic test for malaria patients in Thailand (endemic area) and Korea (recently reemerging area). The sensitivity of P. vivax, P. falciparum, and P. malariae was 96.3% (26 /27), 90.6% (29/32), and 100% (6/6), respectively, and the specificity was 63.5% (40/63) in Thailand samples. The sensitivity of P. vivax was 98.8% (88/89), and the specificity was 96.6% (86/89) in Korean samples. Pv30 appears to be a good and reliable recombinant antigen for serodiagonosis of malaria in a nonendemic area.