Protection against streptococcal pharyngeal colonization with a vaccinia: M protein recombinant.

Phagocytosis of group A streptococci requires type-specific antibodies directed against the variable determinants of the bacterial surface M protein molecule. As a step toward developing a broadly protective anti-streptococcal vaccine, a vaccinia virus (VV) recombinant was constructed that expresses the conserved region of the structural gene encoding the M6 molecule (VV:M6'). Mice immunized intranasally with the VV:M6' virus showed markedly reduced pharyngeal colonization by streptococci after intranasal and oral challenge with these bacteria. M protein-specific serum immunoglobulin G was significantly elevated in vaccinated animals and absent in controls. A similar approach may prove useful for the identification of protective determinants present on other bacterial and viral pathogens.