Preclinical evaluation of a vaccine based on conserved region of M protein that prevents group A streptococcal infection.

ABSTRACT

BACKGROUND & OBJECTIVES: Infection with group A Streptococcus (GAS) may result in a number of human diseases ranging from the relatively benign pharyngitis to the potentially life-threatening invasive diseases and post-infectious sequelae. We have previously defined a minimal B-cell epitope from the conserved region of the M-protein. Here we report on the immunogenicity, opsonic potential of the resulting sera and the level of protection induced by this peptide in comparison to a pepsin extract of the M protein. METHODS: Inbred mice were immunized with peptides derived from the M protein. Sera were collected from the immunized mice and its opsonic potential determined for M1 and M6 GAS strains. Mice were then intranasally challenged with a virulent M1 GAS strain to determine the protective efficacy of the peptides. RESULTS: The peptides induced significant antibody responses when delivered subcutaneously and immunized mice demonstrated significantly enhanced survival compared to control groups following challenge. INTERPRETATION & CONCLUSION: The data obtained in the present study indicated that the chimeric peptide J8 from the conserved region of the M protein could form the basis for an anti-streptococcal vaccine in future.