Immunogenicity and protective ability of RpoE against Streptococcus suis serotype 2

Aims RpoE is quite immunogenic and can be used as a candidate vaccine for Streptococcus suis infection via immunoproteomics as reported in our previous studies. In this study, we aimed to verify the immunogenicity of recombinant RpoE and its protective effect against of S. suis. Methods and Results The RpoE protein was successfully expressed in Escherichia coli, and the purified recombinant protein was mixed with ISA206 to prepare an S. suis subunit vaccine. Mice were immunized with the RpoE subunit vaccine and then infected with the virulent S. suis strain ZY05719. Subunit vaccine-immunized mice achieved 50% protection, less pathological damage and less bacterial distribution in each organ compared with the control mice. Furthermore, in vitro culture, showed that mouse antisera significantly (P < 0·001) inhibited the growth of S. suis, and qRT-PCR results showed that RpoE successfully induced the up-regulation of IL-6 and TNF-α cytokines. Conclusions RpoE mice were vaccinated to obtain immune protection, which may be candidates for S. suis subunit vaccine. Significance and Impact of the Study The results of this study will provide new ideas for the development of safe and effective recombinant subunits vaccines for S. suis.