title: New protective antigen of group A streptococci.
abstract: 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.
authors.affiliation: Veterans Affairs Medical Center, Memphis, Tennessee 38104, USA. james.dale@med.va.gov
authors.forename: J B
authors.initials: JB
authors.lastname: Dale
authors.forename: E Y
authors.initials: EY
authors.lastname: Chiang
authors.forename: S
authors.initials: S
authors.lastname: Liu
authors.forename: H S
authors.initials: HS
authors.lastname: Courtney
authors.forename: D L
authors.initials: DL
authors.lastname: Hasty
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis / Q000276:immunology / Q000302:isolation & purification; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D001428:Bacterial Vaccines; D001483:Base Sequence; D003001:Cloning, Molecular; D003429:Cross Reactions; D004269:DNA, Bacterial; D007106:Immune Sera; D051379:Mice; D008969:Molecular Sequence Data; D013297:Streptococcus pyogenes / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001428:Bacterial Vaccines; D004269:DNA, Bacterial; D007106:Immune Sera; C119204:streptococcal protective antigen