Immuno-protective Potency Of Recombinant MRP-FBP Adhesin Fragment From Streptococcus Suis Type 2

Streptococcus suis type 2 (SS2) is an important zoonotic pathogen which causes meningitis, pneumonia, septicemia, and sudden death. Muramidase-released protein (MRP) and fibronectin and fibrinogen-binding protein (FBP) are adhesins of SS2. Based on DNAstar software analysis, one highly antigenic fragment in each gene was selected and amplified by PCR. Then recombinant plasmid pET32a-mrp, pET32a-fbp and pET32a-mrp-fbp were respectively constructed, transmitted into E. coli. BL21(DE3), and induced by IPTG. SDS-PAGE analysis showed the molecular weight of expressed MRP was 47KD, FBP 52KD, and MRP-FBP 80kD. Western blot demonstrated that MRP-FBP can be recognized by serum against SS2 whole cell. Adhesin vaccines were Prepared respectively with MRP, FBP and MRP-FBP as antigen. Balb/c mice were used to determine protective capacity of the three vaccines. Mice were vaccinated twice and then challenged with HA9801, a virulent isolate of SS2. Results showed that, vaccine MRP-FBP protected 80% of mice, MRP 60%, and FBP only 30%. Conclusion: the short fragmented recombinant adhesin MRP-FBP selected in this study is the best candidate antigen up to date for subunit vaccine development against SS2.