JJo, a recombinant dimer of conformationally restricted peptide elicits protective response against Group A Streptococcus (GAS) isolates from a GAS-endemic region

Abstract

A peptide (J14) containing conformationally restricted epitopes from the M protein of Group A Streptococcus (GAS) is capable of eliciting protective immune response against GAS infection. However, the protective response may be lost possibly due to its weak secondary-structure when the antigen is fused with other antigens in a recombinant polyepitope vaccine construct. We previously showed that JJo, a conformationally stabilized derivative of dimeric J14, overcomes this problem. We now show that anti JJo antibodies react with diverse GAS isolates found in the Indian sub-continent and that these antibodies are opsonic for GAS. The GAS strains used in this study were isolated from throat and skin swabs from Mumbai, Chennai and Vellore. Sera from mice immunized with recombinant JJo peptide were tested by ELISA, immunofluorescence, flow-cytometry, indirect bactericidal assay and mouse challenge assays to determine specific immunogenicity, opsonic functions and protection against an Indian isolate. We propose that JJo is a robust antigen suitable for inclusion in recombinant multi-epitope vaccines which are potentially affordable option for the pediatric population of developing countries.