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Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction
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Capsular antibodies induce type-specific phagocytosis of capsulated Staphylococcus aureus by human polymorphonuclear

W W Karakawa1, A Sutton, R Schneerson

  • 1Pennsylvania State University, University Park 16802.

Infection and Immunity
|May 1, 1988
PubMed

Insights

Staphylococcus aureus types 5 and 8 capsules resist phagocytosis. Antibodies targeting these capsular polysaccharides (CPS) enhance phagocytosis by human immune cells, aiding immunity against S. aureus infections.

Area of Science:

  • Immunology
  • Microbiology
  • Bacterial Pathogenesis

Background:

  • Staphylococcus aureus is a major cause of bloodstream infections.
  • Capsular types 5 and 8 (CPS) are prevalent in invasive S. aureus strains.
  • These capsular polysaccharides are known virulence factors that evade host immune responses.

Purpose of the Study:

  • To investigate the role of Staphylococcus aureus capsular types 5 and 8 in evading phagocytosis.
  • To determine the efficacy of antibodies against capsular polysaccharides in promoting phagocytosis.
  • To elucidate the contribution of specific CPS epitopes, like O-acetylation, to immune evasion.

Main Methods:

  • In vitro phagocytosis assays using human polymorphonuclear leukocytes (PMN).
  • Testing of antisera and monoclonal antibodies against type 5 and 8 capsular polysaccharides (CPS).
  • Evaluation of antibody efficacy against native and modified CPS, including O-acetylated epitopes.

Main Results:

  • Staphylococcus aureus strains with capsular types 5 and 8 demonstrated resistance to phagocytosis by PMN.
  • Type-specific antisera and monoclonal antibodies against CPS 5 and 8 significantly induced phagocytosis.
  • Antibodies targeting the O-acetyl moiety of type 8 CPS were particularly effective in promoting phagocytosis.

Conclusions:

  • Staphylococcus aureus capsular polysaccharides (CPS) mediate resistance to host innate immunity, specifically phagocytosis.
  • Antibody-mediated targeting of CPS, especially specific epitopes like O-acetylation, can overcome immune evasion.
  • These findings support the role of CPS in S. aureus pathogenesis and suggest potential targets for immunotherapies.

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