ANALYSIS OF IMMUNOGLOBULIN G-BINDING-PROTEIN EXPRESSION BY INVASIVE ISOLATES OF STREPTOCOCCUS-PYOGENES

Invasive group A streptococcal isolates collected as part of a Centers for Disease Control and Prevention surveillance study were analyzed f or expression of immunoglobulin G (IgG)-binding proteins. Two IgG-bind ing phenotypes of group A isolates of the M1 serotype were identified The first group expressed a surface protein that bound all four human IgG subclasses (type IIo) and was recognized by rabbit anti-serotype M 1-specific antiserum but not by normal rabbit serum. The second group expressed an IgG-binding protein that was also recognized by the anti- serotype M1 antiserum but demonstrated significant nonimmune reactivit y only with human IgG3 (type IIb). Analysis of extracts of the isolate s for reactivity with human IgA, fibrinogen, and albumin was also perf ormed The importance of the binding of human plasma Proteins to pathog enic group A streptococci remains to he established.