Sero-diagnostic potential of Plasmodium falciparum recombinant merozoite surface protein (MSP)-3 expressed in silkworm.

Plasmodium falciparum is a blood protozoan parasite, transmitted by Anopheles mosquitoes vectors, that can cause morbidity and even leads to mortality in tropical countries. Strategies are directed to combat malaria including development of diagnostic tools, serological markers and vaccinations. A target under intensive studies is Merozoite Surface Protein (MSP)-3. The aim of this study is to express and purify recombinant MSP3 of P. falciparum (rPfMSP3) using silkworm expression system as a host for its large-scale production and to investigate its potential effectiveness for sero-diagnosis. The rPfMSP3 formed oligomers in a blue-native PAGE and its N-glycosylation was confirmed by periodic acid-Schiff staining and PNGase F treatment. The amyloid-like morphology of the rPfMSP3 oligomers was observed. Enzyme-linked immunosorbent assay showed that 60-70% of human samples from subjects living in malaria endemic areas in Indonesia detected the rPfMSP3. Western blot results showed that the rPfMSP3 was recognized by a malaria infected human serum but not by an uninfected human serum. The rPfMSP3 was successfully expressed in silkworm as a soluble protein and has the potential to be used in serological measurement for detecting PfMSP3-specific antibodies in sera from individuals living in endemic areas.