Identification and characterization of a novel antigenic protein of Streptococcus suis type 2

An immunogenic protein, named HM3, of Streptococcus suis type 2 HA9801 was identified by using immunoproteomic assay. Some characters of this protein were analyzed by several online bioinformatical tools, including BLAST, SinglP, HMMTOP and PSORTb. The most homologous sequence of HM3 was extracellular solute-binding protein (gi/69246104) of Enterococcus faecium. The predictions results showed that HM3 contained Signal peptide and one transmembrane region, and Non-Cytoplasmic Localization were also predicted. Partial gene of this protein were amplified from the genome of HA9801 by PCR and inserted into expression plasmid pET-32a (+) after double digested by BamH I and Sal I, then transformed into BL21 (DE3) where they were induced to express by IPTG. After induced, there was specific proteins band of approximately 45kDa on the SDS-PAGE gel. Western-blotting showed that recombinant protein could react with immune serum of HA9801 of SPF (Specefic pathogen Free) mini-swine. This protein could be taken as vaccine candidate of SS2.