The Production of Opacity in Serum by Group A Streptococci and Its Relationship with the Presence of M Antigen

Widdowson, Jean P.; Maxted, W. R.; Grant, Doris L.

doi:10.1099/00221287-61-3-343

Cited by 77 publications

(81 citation statements)

References 12 publications

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“…The OF is protein in nature (Hill & Wannamaker, 1968) and its serological specificity corresponds to the M-type from which it was derived, in that it is inhibited by antisera prepared against members of the same M-type but not by antisera for heterologous M-types (Widdowson et al 1970). The correlation with T-antigen pattern…”

Section: Introductionmentioning

confidence: 99%

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

Widdowson

Maxted

Grant

et al. 1971

Journal of General Microbiology

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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.

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Section: Introductionmentioning

confidence: 99%

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

Widdowson

Maxted

Grant

et al. 1971

Journal of General Microbiology

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“…OF is antigenically variant, and type-specific antiserum against OF will neutralize the opacity reaction (52). The antigenic variability of OF parallels that of M protein (56). For example, a strain with a type 49 M protein will always express a type 49 OF.…”

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confidence: 99%

Identification of a divergent M protein gene and an M protein-related gene family in Streptococcus pyogenes serotype 49

1989

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The antigenically variant M protein of Streptococcus pyogenes enhances virulence by promoting resistance to phagocytosis. The serum opacity factor (OF), produced by a subset of M serotypes, is also antigenically variant, and its antigenic variability exactly parallels that of M protein. OF-positive and OF-negative streptococci are also phenotypically distinguishable by a number of other criteria. In order to study the differences between OF-positive and OF-negative streptococci, we cloned and sequenced the type 49 M protein gene (emm49), the first to be cloned from an OF-positive strain. This gene showed evolutionary divergence from the OF-negative M protein genes studied previously. Furthermore, emm49 was part of a gene family, in contrast to the single-copy nature of previously characterized M protein genes.The M protein, a major virulence factor of Streptococcus pyogenes (group A streptococci), enhances the pathogenicity of the organism by blocking phagocytosis in the nonimmunized host (26,27). Antibodies to M protein develop in infected individuals and confer immunity (34). Streptococcal M protein, however, is antigenically variant, and opsonic antibodies to M protein are largely type specific. Thus, with 70 or more M protein serotypes (35), group A streptococci can successfully avoid immune surveillance.Molecular biological techniques have increased our knowledge of the structure of M protein and its antigenic variability. Five M protein genes have been cloned, and all have been at least partially sequenced (16,24,40,42,46). The M proteins encoded by these sequenced genes have a common framework which includes a conserved signal peptide, a hypervariable amino terminus, and a highly conserved C-terminus. Each gene also appears to contain some internal sequence repetitions, although the extent and degree of similarity of these repeats vary among the genes. Furthermore, regions preceding and following these M protein genes are conserved (16,42). This suggests that the genes are situated in a common expression site on the streptococcal chromosome.Our understanding of how the M protein hypervariable regions evolved is still incomplete. Duplication and deletion of intragenic repeats present in the variable regions of M molecules is a possible mechanism for the introduction of variant amino acids into the M protein sequences (25). Recent evidence shows that intragenic recombination can indeed introduce variant opsonic determinants into the repetitive regions of the M6 protein (28). Not all of the opsonic antigenic determinants of M proteins, however, are located in the repetitive regions of the molecules (25, 32). Thus, additional mechanisms must be involved in the generation of M protein antigenic diversity.A model explaining the generation of M protein antigenic diversity must account for the fact that other streptococcal proteins exhibit antigenic diversity in a nonrandom manner relative to the M type. Among these are the T antigen, a * Corresponding author. (18) and by genetic means (8). Clearly, the processe...

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“…As previously suggested by Widdowson et al (1970), this may be attributed to the partial denaturation of the OF as a result of the harsh conditions of the Lancefield extraction procedure.…”

Section: M a R T I N E Z A N D Othersmentioning

confidence: 62%

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

Martinez¹,

Rippe

Fuller

et al. 1978

Journal of General Microbiology

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The extracellular Opacity Factor elaborated by a strain of group A streptococcus M type 2 was purified by ammonium sulphate precipitation, DEAE-cellulose and hydroxylapatite column chromatography and Sephadex G-200 gel filtration. Gel filtration experiments indicated that the Opacity Factor is constituted of high molecular weight proteins or protein aggregates which appear to dissociate into subunits of 66 000 minimum molecular weight as determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The purified preparations had no group A carbohydrate or T protein antigens. Passive haemagglutination and indirect immunofluorescence tests indicated that Opacity Factor is distinct from the M type 2 protein antigen.

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The Production of Opacity in Serum by Group A Streptococci and Its Relationship with the Presence of M Antigen

Cited by 77 publications

References 12 publications

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

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

Identification of a divergent M protein gene and an M protein-related gene family in Streptococcus pyogenes serotype 49

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

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