Expression, immunolocalization and serodiagnostic value of a myophilin-like protein from Schistosoma japonicum.

The cDNA of a Schistosoma japonicum myophilin-like protein was cloned, sequenced, and expressed in Escherichia coli as a recombined protein (rSj myophilin-like protein), and the protein was purified by affinity chromatography. The deduced amino acid sequences of the Sj myophilin-like protein showed significant homology to myophilin, calponin, Np22 and Mp20. Northern blot and RT-PCR analyzes revealed expression of the Sj myophilin-like protein mRNA in eggs, sporocysts, cercariae, hepatic schistosomula and adult worms. Confocal fluorescence microscopy localized the native protein to the muscle of the adult worm. In schistosome-infected rabbits, the rSj myophilin-like protein antibody level, assessed by ELISA, was elevated after infection but was reduced after praziquantel treatment. In humans, the myophilin-like protein antibody level was evaluated by ELISA in sera from 33 non-infected humans and 61 schistosomiasis patients; the results showed a highly significant difference between the two groups with a sensitivity of 57.4%. Taken together, the myophilin-like protein may prove useful for monitoring the therapeutic effect of praziquantel rather than in serodiagnosis of schistosomiasis.