Demonstration of protection in mice from a lethal challenge of three M serotypes of Streptococcus pyogenes using an M-negative vaccine.

Mice were vaccinated with a temperature-sensitive, M-negative mutant (JC3) of Streptococcus pyogenes. This vaccine was found to offer protection from a lethal challenge of homologous M-negative and type 28 M-positive strains of S. pyogenes as well as heterologous M3 and M18 strains. Using an immunoblot method, hyperimmune serum from mice vaccinated with JC3 was found to contain moderate to high titres of antibody to all challenge strains. Additionally, this hyperimmune serum was used to probe Western blots of whole-cell proteins extracted from each of the above streptococcal strains. Three proteins were identified (M(r) = 32, 43 and 46 kDa) as immunogenic and conserved among the three serotypes studied.