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The relationship between opacity factor and M protein in Streptococcus pyogenes

G Hallas, J P Widdowson

    Journal of Medical Microbiology
    |February 1, 1983
    PubMed

    Insights

    Streptococcus pyogenes M protein and opacity factor (OF) were extracted using different methods. Some strains lost M protein and OF activity, suggesting potential plasmid involvement, though plasmids were not detected.

    Area of Science:

    • Microbiology
    • Immunology
    • Molecular Biology

    Background:

    • Streptococcus pyogenes possesses M protein and opacity factor (OF), virulence factors with implications for host immune response.
    • Different extraction methods yield varying amounts of M protein and OF, impacting antigen characterization.
    • The genetic basis and stability of M protein and OF expression in S. pyogenes serotypes are not fully understood.

    Purpose of the Study:

    • To investigate the differential extraction of M protein and OF from Streptococcus pyogenes.
    • To characterize the properties of M protein and OF, including their separation and functional activity.
    • To explore the stability of M protein and OF expression and potential genetic mechanisms, such as plasmid carriage.

    Main Methods:

    • Differential extraction of antigens using Lancefield acid and sodium dodecyl sulphate (SDS) methods.
    • Separation of antigens via Sepharose 4B chromatography.
    • Functional assays including precipitation with anti-M serum and neutralization of opsonic antibodies.
    • Isoelectric focusing for antigen profiling.
    • Serial subculture in Todd-Hewitt broth to assess antigen stability.
    • Agarose-gel electrophoresis to detect plasmid DNA.

    Main Results:

    • SDS extracts yielded high OF titres, while acid extracts yielded more M protein.
    • OF could be separated from M protein, and some OF fractions neutralized opsonic antibodies.
    • Partial similarity was observed in the isoelectric-focusing profiles of M protein and OF.
    • Some OF-positive serotypes (M-types 22, 49) lost both M antigen and OF activity upon subculture.
    • OF-negative serotypes showed variable stability; M-types 5 and 6 were stable, while M-types 12, 55, and 57 lost M antigens.
    • No plasmid DNA was detected in any tested strains via agarose-gel electrophoresis.

    Conclusions:

    • Extraction method significantly influences the yield of M protein and OF from Streptococcus pyogenes.
    • OF possesses functional activity, including the neutralization of opsonic antibodies, independent of M protein precipitation.
    • The loss of M antigen and OF activity in certain serotypes suggests genetic instability, potentially involving plasmid-borne genes, although direct evidence was not found.
    • Further investigation is needed to elucidate the genetic mechanisms underlying the stability and expression of these virulence factors.

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