Cloning, Expression, and Immunogenicity Analysis of the CpsE Protein from Group B Streptococcus Isolated from Tilapia (Oreochromis Niloticus)

Abstract

Group B Streptococcus (GBS) is a\rmajor cause of serious bacterial infection in numerous animal species. The\rproduction of capsular polysaccharide(CPs) is vital to GBS to evade host\rimmunity. One of the genes that required for production of CPs, cpsE, has been\rdetermined to be well conserved in capsule gene cluster (cps).This study cloned\rthe cpsE gene from Tilapia of GBS clinical isolate (serotype Ia) and expressed\rthis gene with aid of pET-32a(+) in Escherichia coli BL21(DE3) competent cells\rto obtain high levels of the recombinant protein for further study about CpsE\rin fish and examination of its immunogenicity. The optimization of induction\rconditions (IPTG concentration, temperature and time) in E.coli was accomplished\rand let us to perform the recombinant protein induction at 37℃ for 3h,with 0.2mM IPTG in Luria Bertani (LB) medium.\rAt the optimal conditions, recombinant protein was expressed in an insoluble\rform (inclusion bodies) and accounted for approximately 23% of the total\rprotein. Purification by affinity chromatography yielded about 480mg fusion\rprotein per liter culture.