DISTINCT PROFILES OF IMMUNOGLOBULIN G-BINDING-PROTEIN EXPRESSION BY INVASIVE SEROTYPE M1 ISOLATES OF STREPTOCOCCUS-PYOGENES

Analysis of immunoglobulin G (IgG)-binding-protein expression by invas ive group A streptococcal isolates of the M1 serotype collected as par t of a Centers for Disease Control and Prevention surveillance study r evealed two distinct phenotypes, One group of type M1 isolates express ed a surface protein reactive with ail four human IgG subclasses (type IIo), while a second group expressed a surface protein demonstrating significant reactivity only with human IgG3 (type IIb). The functional forms of IgG-binding protein were antigenically related, and both wer e recognized by a rabbit polyclonal antiserum to serotype M1 but not b y normal rabbit serum. While the quantities of antigenic M1 protein pr esent in the extracts of representative isolates displaying each pheno type differed, the functional differences were found to be qualitative and not solely quantitative. The IgG-binding properties of these anti genically related MI proteins could be readily distinguished from thos e of another IgG-binding protein, protein H. Type M1 isolates of the I Ib phenotype differed from those of the Do phenotype by secreting larg er amounts of a casein-hydrolyzing protease into culture supernatants.