Application of signaling protein 14-3-3 and 26 kDa glutathione-S-transferase to serological diagnosis of Schistosomiasis japonica

Schistosomiasis japonica is currently one of the most serious parasitic diseases and over 670 000 people are infected in China by the end of 2006. In order to establish an effective diagnostic method, the gene coding for Sj14-3-3 and Sj26 kDa GST were cloned and expressed separately in Escherichia coli as fusion protein with His-tag. The rSj14-3-3 and 26 kDa rSjGST were combinedly used as antigens for enzyme-linked immunosorbent assays (ELISA) to diagnose acute and chronic S. japonica. Our results showed that the sensitivity in diagnoses of both acute and chronic schistosomiasis was 94.4% (67/71) and 80.7% (96/119), respectively. The specificity was 94.7% applying 132 sera from people living in S. japonicum-free areas. The data also showed that the recombinant proteins cross-react with Clonorchis sinensis and hookworms at a rate of 11.8% and 5.3% respectively. Parallel tests were conducted among ELISA, indirect hemagglutination assay (IHA) and circular ovum precipitin test (COPT) to determine anti-S. japonicum antibodies in sera of patients with schistosomiasis, healthy control, and those infected with other parasites and the results showed no significant difference in sensitivity for acute schistosomiasis between ELISA and IHA assays (χ2 = 1.33, P > 0.05), but significant between ELISA and COPT assays (χ2 = 6.72, P < 0.01). Our results also revealed significant difference in positive rate between ELISA and IHA (χ2 = 24.74, P < 0.005), as well as between ELISA and COPT (χ2 = 58.14, P < 0.005). These results suggest that the rSj14-3-3 and r26 kDa SjGST would be effective diagnostic antigens for detection of antibodies to S. japonicum in human. Due to the easy production, high sensitivity and specificity, the recombinant proteins tested in this study can be considered as candidate reagent for immunological diagnosis of human schistosomiasis.