Expression, purification and polyclonal antibody preparation of the Schistosoma japonicum SjGrpE protein

Abstract

To investigate the biological properties of Schistosoma japonicum SjGrpE protein, and to express and purify the recombinant SjGrpE protein and test its immunogenicity. The amino acid composition, molecular weight, hydrophilicity and hydrophobicity, transmembrane region, signal peptide, localization, phosphorylation site, ubiquitination site, glycosylation site, secondary and tertiary structures and B cell epitopes of the SjGrpE protein were predicted using bioinformatics analyses. The SjGrpE gene was amplified using PCR assay using S. japonicum cDNA as a template, double enzyme-digested and linked to the pET28a vector to yield the recombinant plasmid pET28a-SjGrpE. The recombinant plasmid pET28a-SjGrpE was transformed into Escherichia coli BL21, and then IPTG was employed to induce the expression of the target protein, which was purified by nickel ion affinity chromatography. After mice were immunized with the recombinant SjGrpE protein, mouse sera were collected, and the polyclonal antibody against the SjGrpE protein was characterized. SjGrpE protein, which was identified as a hydrophilic protein, was predicted to have a molecular weight of approximately 24.3 kDa without transmembrane regions or signal peptides, and locate in the mitochondrion. SjGrpE protein contained 18 phosphorylation sites and 2 ubiquitination sites, but had no glycosylation sites. In addition, SjGrpE protein contained 5 B-cell epitopes. The full length of SjGrpE gene was approximately 660 bp. The recombinant pET28a-SjGrpE plasmid was successfully generated, and the recombinant SjGrpE protein was obtained following the affinity chromatography, which stimulated mice to secrete high-titer antibodies. The recombinant SjGrpE protein has been successfully prepared and this recombinant protein has a high immunogenicity, which provides a basis for evaluating its value as a vaccine candidate for S. japonicum infections.