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Protective antigenic determinant of streptococcal M protein shared with sarcolemmal membrane protein of human heart

J B Dale, E H Beachey

    The Journal of Experimental Medicine
    |October 1, 1982
    PubMed

    Insights

    Antibodies against a specific part of type 5 M protein from group A streptococci cross-react with human heart tissue. This finding suggests a potential link between streptococcal infections and heart conditions.

    Area of Science:

    • Immunology
    • Microbiology
    • Cardiology

    Background:

    • Group A streptococci (GAS) are a significant human pathogen.
    • M proteins are key virulence factors of GAS, involved in immune evasion.
    • Previous studies suggest potential autoimmune reactions following streptococcal infections.

    Purpose of the Study:

    • To investigate the cross-reactivity of antibodies against type 5 M protein with human heart tissue.
    • To identify and characterize the specific antigenic determinant responsible for this cross-reactivity.
    • To assess the functional significance of this cross-reactivity in terms of antibody-mediated protection.

    Main Methods:

    • Immunization of rabbits with a peptide fragment of type 5 M protein (pep M5).
    • Immunofluorescence assays to detect antibody cross-reactivity with human heart sarcolemmal membranes.
    • Antibody absorption assays using sarcolemmal membranes and various streptococcal M proteins.
    • Opsonization assays to evaluate the functional activity of antisera against streptococci.
    • Affinity chromatography for purification of cross-reactive antibodies and antigens.

    Main Results:

    • One rabbit produced antibodies that cross-reacted with human heart sarcolemmal membranes.
    • Cross-reactivity was specific and could be absorbed by type 5 and 19 M proteins and heart tissue.
    • Heart-reactive antibodies enhanced the opsonization of both type 5 and type 19 streptococci.
    • The cross-reactive antigen purified from heart tissue was a complex protein with four subunits.

    Conclusions:

    • A specific antigenic determinant on type 5 M protein is responsible for cross-reactivity with human heart tissue.
    • This cross-reactivity is associated with protective immunity against relevant streptococcal serotypes.
    • The findings provide evidence for a potential mechanism linking streptococcal infections to rheumatic heart disease.

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