ABSTRACT
Objective To express the novel fibronectin-binding protein Fba of group A streptococcus(GAS)and analyze its immunogenicity,so that to evaluate the immune responses to GAS infection.Methods fba gene was amplified by polymerase chain reaction(PCR)and confirmed by sequencing.Then it was cloned into pGEX4T-2 vector and Fba protein was expressed in E.coli BL21.The protein expression was identified by enzyme-linked immunosorbent assay(ELISA)and Westernblot.The sera from mice infected with GAS and anti-streptolysin-O positive patients were detected using microtiter plates coated with purified Fba protein as antigen.Afterward Balb/C mice were immunized with this purified protein and the sera were collected after the third immunization for the detection of IgG titer.Results It was confirmed by ELISA and Western blot that the recombinant Fba protein had a specific affinity with anti-Fba sera of rabbit.The anti-serum IgG titer of mice imrnunized with Fba protein was up to 1:4800.Conclusions GAS infection or Fba protein immunization are able to induce high serum titer of anti-Fba which could react specifically with the recombinant Fba protein.It indicates that Fba protein has good immunogenicity and antigenicity.So Fba protein could be a GAS candidate vaccine and an important tool to detect anti-GAS titer in GAS infected patients.