High immunogenicity of Streptococcus pneumoniae IgA1 protease

Introduction and Objectives: IgA1 protease is one of the virulance factors in Streptococcus pneumoniae and plays an important role in bacterium pathogenesis. In the present study, the immunogenicity of IgA1 protease was evaluate in healthy human sera. Materials and Methods: IgA1 protease truncated gene (705bp) was amplified by PCR and following digestion with restriction enzymes, ligated with pET28a expression vector. Recombinant protein expression was carried out in E. coli BL21 strain and recombinant protein purified by affinity chromatography. Antibody titer against recombinant protease in three groups of age 0-2, 2-40 and over 40 years old healthy individuals was measured with ELISA assay. Results: Recombinant protein was expressed and purified successfully. Antibody titer against IgA1 protease showed a significant correlation (p-value<0.05) between groups under two and over two years at titers of 20, 40, 80 and 160. Conclusion: According to the results, an appropriate antibody titer against recombinant protease was obtained especially in people with over two years old. It concluded that the high levels of antibody against recombinant IgA1 protease may be resulted from permanent stimulation of immune system by IgA1 protease which naturally produce by streptococci in oral cavity.

Keywords:

IgA1 protease , Streptococcus pneumoniae , ELISA assay