The Relationship between M-antigen and Opacity Factor in Group A Streptococci

Abstract

S U M M A R YM-protein and the opacity factor (OF) were both extracted by Lancefield's method from certain types of group A streptococci. The two proteins could not be separated by fractional precipitation with ammonium sulphate, column chromatography or polyacrylamide gel electrophoresis. The OF appeared to be closely associated with the high molecular weight fraction of the M-antigen, and there is some evidence that the two may form part of the same molecule.M-protein and the OF were sought in various other extracts and preparations of M-positive and M-negative variants of serotypes which gave a positive serum opacity reaction (SOR). In all preparations from M-positive variants, the two proteins were always present. In M-negative variants, the OF present in the wall-membrane fraction could be extracted only by ' phage-associated ' lysin. All other extracts from M-negative variants were SOR-negative and M-negative. In the SOR-positive extract obtained by phage lysin treatment of M-negative variants, no M-antigen could be detected by precipitin tests, though the extracts contained a protein of similar electrophoretic mobility to the precipitin-positive protein in the extracts of the M-positive variants of the same serotype.

Purification of the Extracellular Opacity Factor of a Strain of Group A Streptococcus M Type 2

“…While this property suggests that the type-specific antiserum contains antibodies specific for the OF in highly purified extracellular preparations, the lack of reactivity of the same antiserum with these preparations by the various sensitive immunological procedures makes it difficult to interpret. An analogous observation was made by Widdowson et al (1971). They reported the preparation of antisera that neutralized the SOR activity of the immunizing strain but had little or no M precipitin activity.…”

“…Carboxymethylcellulose chromatography at an acid pH had been used for the partial purification of M type antigens 1 and 12 (Fox & Wittner, 1965;Strauss, Metha & Lange, 1974) and the M and OF antigens in Lancefield extracts of M types 2 and 49 streptococci (Widdowson et al, 1971). In our experiments, however, the ammonium sulphate-purified SOR-active test samples partially precipitated when dialysed against phosphate buffers at the slightly acidic pH of 5.5.…”

“…In contrast, Top & Wannamaker (1968b) showed a consistent association between several M serotypes and the exhibition of the SOR. More recent studies by Widdowson et al (1971) have indicated that cell-bound OF is closely related to the M antigens of SOR+ strains. They were unable to separate the two entities in cellular extracts from two SOR+ strains by biochemical procedures and suggested that the OF and M antigens may form a part of the same protein molecules.…”

Antibody to streptococcal opacity factor in human sera

“…A tube of horse serum without antiserum and another of horse serum without OF were always included as controls and the opacity was estimated visually or after dilution with an equal volume of saline. The A475 was read spectrophotometrically (Widdowson et al 1971).…”

“…The antigenic specificity of OF runs parallel with that of the M-antigen (Widdowson, Maxted & Grant, 1970), so that inhibition is observed only when OF is mixed with antisera against a member of the same M-type. The OF is closely associated with the M-antigen in the bacterial cell and the two may form part of the same complex protein (Widdowson, Maxted, Grant & Pinney, 1971).…”