System and intranasal immunization of group B streptococcal C5a peptide
Objective To study the system of streptococcal C5a peptidase (ScpB) and the specif-ic antibody levels in serum, lung, vagina and recta after subcutaneous and intranasal immunization with dif-ferent doses of C5a peptide. Methods Recombinant protein C5a peptide was expressed in E. coli strain BL21 and purified by affinity chromatography. The expressed product was identified by SDS-PAGE and pep-tide mass fingerprinting (PMF). BALB/c mice were subcutaneously and intranasally injected with different doses of ScpB. Antibody titer was tested by ELISA. Opsonophagocytosis assay was used to test the function of antibody. Results ScpB protein was successfully expressed and purified. The probability based mouse score of ScpB was 175 by PMF analysis. ELISA data showed that both subcutaneous and intranasal immtmi-zation could elicit significantly higher levels of IgG in immunized mice serum than that of control group (P ＜0.01), 30 μg group waa better than 5 μg and 10 μg group. Intranasal immunization could elicit higher lev-els of IgA in lung, vagina and rectum (P ＜0.001) while system immunization could not. Opsenophagocyto-sis tests indicated that anti-serum of ScpB had opsenophagocytic activity than that of control (P ＜ 0. 05).Conclusion The results demonstrated that intranasal immunization with ScpB could induce significantly higher levels of lgG and IgA, and its anti-serum had better opsenic activity. 
 
Key words: 
Group B Streptococcus;  CSa peptidase;  Mucosal immunization;  Subcutaneous immu-nization;  Opsenophagocytosis