New protective antigen of group A streptococci

AUTOR(ES)

Dale, James B.

FONTE

American Society for Clinical Investigation

RESUMO

It is widely believed that the surface M protein of group A streptococci is the predominant surface protein of these organisms containing opsonic epitopes. In the present study, we identified a new surface protein, distinct from M protein, that evokes protective antibodies. A type 18 M-negative mutant was found to be both resistant to phagocytosis in human blood and virulent in mice. The wild-type strain, but not the M-negative mutant, was opsonized by antisera against purified recombinant M18 protein or a synthetic peptide copying the NH2-terminus of M18. However, antisera raised against a crude pepsin extract of the M-negative mutant opsonized both strains, indicating the presence of a protective antigen in addition to type 18 M protein. This antiserum was used to identify and purify a 24-kDa protein fragment (Spa, streptococcal protective antigen) that evoked antibodies that opsonized the M18 parent and the M-negative mutant. The results of passive mouse protection tests confirmed the presence of protective epitopes within Spa. The deduced amino acid sequence of a 636-bp 5′ fragment of the spa18 gene showed no homology with sequences in GenBank. These studies reveal the presence of a new protective antigen of certain strains of group A streptococci that may prove to be an important component of vaccines to prevent streptococcal infections.

Documentos Relacionados

• Molecular Analysis of Group B Protective Surface Protein, a New Cell Surface Protective Antigen of Group B Streptococci
• A monoclonal antibody identifies a protective C-protein alpha-antigen epitope in group B streptococci.
• Conservation of protective and nonprotective epitopes in M proteins of group A streptococci.
• Streptococcal group B type antigen X in group L streptococci.
• Evaluation of a new presumptive medium for group D streptococci.