Immune effect of FbaAmAb2 against the surface protein FbaA of group A Straptococcus / 中华微生物学和免疫学杂志

ABSTRACT

Objective To detect the immune effect of FbaAmAb2 against the surface protein of group A Straptococcus (GAS),and explore the pathogenesis and therapy of GAS infections.Methods By subclonal and bacterial ELISA,the positive hybridoma cells were screened that can produce better titers of FbaAmAb2 against GAS-surface FbaA protein,and were injected into the peritoneal cavities of BALB/c mice to produce ascites.The collected ascites were performed to dilute,as follows,original ascite,12,14,18,and 116 to test tube agglutination.Based on the results,we selected appropriate dilution to passively immunize mice,and then challenged the mice with GAS,evaluating FbaAmAb2 neutralizing ability with GAS in mice by the survival rate of the immunized mice.Whether FbaAmAb2 could inhibit the binding of factor H to GAS was confirmed by the invasive inhibition assay.Results The IgG titer of bacteria solution ELISA is 1160 and the titer of tube agglutination is 1∶8.The protect rates of FbaAmAb2 on preventing mice with GAS infections are as follows66.67％ in original ascite and 12 diluted groups,and 50％ in 14 diluted group.Mice in each experimental group were evoked significantly protective immune responses compared with the PBS control by SPSS analysis.FbaAmAb2 can competitively inhibit factor H binding to the surface proteins FbaA of GAS,which decreased the entry of GAS into the cytoplasm of human epithelial cells through the binding of factor H.Conclusion FbaAmAb2 is promising to be used in emergent prevention or the clinical therapy for GAS infection and it is promising starting points for pharmacologic targeting and further development of new therapeutic agents for GAS.