[Eukaryotic expression of SjE16, SjPPIase and SjRobl genes from Schistosoma japonicum egg and evaluation of their role in immunodiagnosis].

Objective: To express Schistosoma japonicum egg proteins by eukaryotic system and evaluate their role in schistosomiasis immunodiagnosis.

Methods: S. japonicum egg RNA was extracted and reversed to cDNA. Egg specific or highly expressed genes: SJCHGC01695 (SjE16), SJCHGC00856 (SjlMA8), SJCHGC06249 (SjTOR), SJCHGC06324 (SjP40), SJEFTD02 (SjSLP), SJCHGC06679 (SjPPIase) and SJCHGC06529 (SjRobl), were amplified and sub-cloned to eukaryotic expression vector pPIC9K. Recombinant vectors were transformed to yeast GS115 and the recombinant yeast was induced by methanol. Proteins were purified with Ni-NTA affinity chromatography and analyzed by SDS-PAGE and Western blotting. For the detection of specific antibodies, the wells of microtiter plate were coated with soluble egg antigen (SEA), SjE16, SjPPIase and SjRobl, respectively, or combination of recombinant proteins. The specific antibody reactivity in sera from schistosome-infected mice and patients were examined by ELISA.

Results: The highly expressed genes from S. japonicum eggs were cloned by PCR. The recombinant proteins of SjE16, SjPPIase and SjRobl were expressed and identified by SDS-PAGE and Western blotting. Those recombinant SjE16, SjPPIase and SjRobl were recognized by IgM and IgG in schistosome-infected mouse and patient sera. The sensitivity of the three antigens in detecting IgM and IgG in acute patients were 80%, 60%, 80% and 40%, 80%, 70%, respectively, while that of the combination of SjE16 and SjRobl in detecting IgM was 100%.

Conclusion: The above three S. japonicum egg enriched proteins were expressed using eukaryotic expression system and can be used in acute schistosomiasis diagnosis.