Engineering, expression, and immuno-characterization of recombinant protein comprising multi-neutralization sites of rabies virus glycoprotein

The rabies virus (RV) glycoprotein (G protein) induces neutralizing antibodies, which are important in protection against rabies. In the present study, three gene fragments that encode polypeptides (corresponding to amino acid residues 19–60, 181–219, and 300–458) comprising the linear neutralization sites of the G protein were spliced together in tandem by PCR-based site-directed mutagenesis and heterologously expressed in Escherichia coli (DE3). The recombinant protein (designated rRVg) was purified under denaturing conditions and solubilized by stepwise dialysis against an alkaline buffer (0.05 M Na2CO3 pH 9.6). Western blot analysis of the antigenicity of rRVg showed that it was recognized by rabies-immune serum. Competitive neutralization assay revealed that rRVg significantly reduced the RV-neutralizing activity of the rabies-immune serum. These results show potential of rRVg as a diagnostic antigen for detecting RV-neutralizing antibodies in immunized hosts.