SEROLOGIC EVIDENCE FOR A CLASS-I GROUP-A STREPTOCOCCAL INFECTION AMONG RHEUMATIC-FEVER PATIENTS

Group A streptococci (GAS) of serotypes most commonly associated with rheumatic fever (RF) outbreaks differ from many other serotypes by the presence of a unique, surface-exposed epitope on the M protein molecu le, Based on the presence or absence of this epitope, GAS are categori zed as class I or II, respectively, The objective of this study was to determine whether RF patients have an altered immune response to the class I-specific epitope, Immunoreactivity to class I- and class II-sp ecific epitopes was determined for serum IgG derived from persons with a recent history of acute RF, uncomplicated GAS pharyngitis, and no k nown recent GAS infection. The results indicate that only RF patients display elevated levels of serum Ige directed towards the class I-spec ific epitope; they lack immunoreactivity to the class II epitope, The serologic findings strongly suggest that many of the RF patients were recently infected with a class I GAS isolate.