Serological detection of Plasmodium vivax malaria using recombinant proteins corresponding to the 19-kDa C-terminal region of the merozoite surface protein-1

Abstract Background Serological tests to detect antibodies specific to Plasmodium vivax could be a valuable tool for epidemiological studies, for screening blood donors in areas where the malaria is not endemic and for diagnosis of infected individuals. Because P. vivax cannot be easily obtained in vitro, ELISA assays using total or semi-purified antigens are rarely used. Based on this limitation, we tested whether recombinant proteins representing the 19 kDa C-terminal region of the merozoite surface protein-1 of P. vivax (MSP119) could be useful for serological detection of malaria infection. Methods Three purified recombinant proteins produced in Escherichia coli (GST-MSP119, His6-MSP119 and His6-MSP119-PADRE) and one in Pichia pastoris (yMSP119-PADRE) were compared for their ability to bind to IgG antibodies of individuals with patent P. vivax infection. The method was tested with 200 serum samples collected from individuals living in the north of Brazil in areas endemic for malaria, 53 serum samples from individuals exposed to Plasmodium falciparum infection and 177 serum samples from individuals never exposed to malaria. Results Overall, the sensitivity of the ELISA assessed with sera from naturally infected individuals was 95%. The proportion of serum samples that reacted with recombinant proteins GST-MSP119, His6-MSP119, His6-MSP119-PADRE and yMSP119-PADRE was 90%, 93.5%, 93.5% and 93.5%, respectively. The specificity values of the ELISA determined with sera from healthy individuals and from individuals with other infectious diseases were 98.3% (GST-MSP119), 97.7% (His6-MSP119 and His6-MSP119-PADRE) or 100% (yMSP119-PADRE). Conclusions Our study demonstrated that for the Brazilian population, an ELISA using a recombinant protein of the MSP119 can be used as the basis for the development of a valuable serological assay for the detection of P. vivax malaria.

This work was supported by a grant from the Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP). MHCR, MMR and ISS are supported by fellowships from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). Also, the Ethics Committee of the University of São Paulo approved it. The authors would like to thank Dr. Marcelo U. Ferreira and Dr. Silvia di Santi for kindly providing the sera from individuals from West Africa, Dr. MUF for providing recombinant protein MSP2 of P. falciparum, and Drs. Michel Rabinovitch and MUF for critical reading of the manuscript.

This work was supported by a grant from the Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP). MHCR, MMR and ISS are supported by fellowships from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). Also, the Ethics Committee of the University of São Paulo approved it. The authors would like to thank Dr. Marcelo U. Ferreira and Dr. Silvia di Santi for kindly providing the sera from individuals from West Africa, Dr. MUF for providing recombinant protein MSP-2 of P. falciparum, and Drs. Michel Rabinovitch and MUF for critical reading of the manuscript.