Study on immunological functions of heat shock protein 40 kDa of Schistosoma japonicum

Abstract

To investigate the immunological functions of heat shock protein 40 kDa of Schistosoma japonicum (SjHSP40). The homology of the SjHSP40 protein sequence was analyzed and the B and T cell epitopes of SjHSP40 were predicted using bioinformatics tools. The full-length SjHSP40 gene was amplified using a PCR assay, and cloned into the prokaryotic expression vector pGEX-6P-1, which was transformed into Escherichia coli BL-21. The protein expression was induced with isopropyl β-D-thiogalactoside (IPDG), and then, the recombinant protein was purified with glutathione-sepharose 4B resin to yield the fusion protein GST-SjHSP40, which was checked with SDS-PAGE and Western blotting. Following immunization with GST-SjHSP40, the serum levels of anti-SjHSP40 IgG antibody and IgG1 and IgG2a subtypes were detected in BALB/c mice using ELISA. In addition, the effect of SjHSP40 on CD4+ T-cell subset differentiation was examined using flow cytometry. SjHSP40 contained 7 potential B cell epitopes and multiple T cell epitopes (CTL epitopes and Th epitopes). The prokaryotic expression plasmid pGEX-6p-1-SjSHP40 was successfully constructed, and the fusion protein GST-SjHSP40 was obtained following IPDG induction and protein purification. Significantly higher serum levels of anti-SjHSP40 IgG, IgG1 and IgG2a antibodies were detected in mice immunized with GST-SjHSP40 than in other groups; however, SjHSP40 showed no remarkable effects on CD4+ T-cell subset differentiation. SjHSP40 may induce specific humoral immune responses in mice; however, it does not affect the balance of Th immune responses. It is suggested that SjHSP40 may be a potential vaccine candidate.