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Secretory IgA, salivary peroxidase, and catalase-mediated microbicidal activity during hydrogen peroxide catabolism

Y Uehara1, K Agematsu, K Kikuchi

  • 1Department of General Medicine, Kochi Medical School, Kohasu Oko-cho Nankoku, Japan. ue3527@jeans.ocn.ne.jp

The Journal of Infectious Diseases
|June 3, 2006
PubMed

Insights

Secretory IgA (SIgA) enhances the killing of MRSA by oral bacteria. SIgA converts hydrogen peroxide into ozone, a potent antimicrobial agent, significantly boosting bacterial defenses in the mouth.

Area of Science:

  • Oral microbiology
  • Immunology
  • Antimicrobial mechanisms

Background:

  • Viridans streptococci produce hydrogen peroxide (H2O2) to kill methicillin-resistant Staphylococcus aureus (MRSA).
  • High bacterial counts (hundreds of viridans streptococci) are typically needed to eliminate MRSA.
  • The oral cavity harbors complex interactions between bacteria, host immunity, and antimicrobial molecules.

Purpose of the Study:

  • To investigate the potency of effector molecules generated from H2O2 catabolism in the oral cavity.
  • To elucidate the role of secretory IgA (SIgA) and salivary components in enhancing antimicrobial activity against MRSA and Candida albicans.
  • To understand the mechanisms by which oral bacteria and host factors cooperate to maintain oral homeostasis.

Main Methods:

  • Formation of coaggregates between Streptococcus sanguinis (viridans streptococci), MRSA, and salivary components including SIgA.
  • Analysis of reactive oxygen species (ROS) production, specifically singlet molecular oxygen (1O2), within these coaggregates.
  • Assessment of the bactericidal and fungicidal activity of generated molecules, including ozone, against MRSA and Candida albicans.

Main Results:

  • SIgA and an unidentified salivary factor facilitated coaggregation of Streptococcus sanguinis and MRSA.
  • Within coaggregates, H2O2 was converted to singlet molecular oxygen (1O2) by salivary peroxidase and MRSA catalase.
  • SIgA transformed 1O2 into ozone, resulting in potent bactericidal activity, reducing the required Streptococcus sanguinis count to kill MRSA (<10 cfu).
  • SIgA, Aspergillus niger catalase, and H2O2 in saliva effectively killed Candida albicans, a fungus resistant to H2O2.

Conclusions:

  • SIgA plays a crucial role in potentiating the antimicrobial activity of oral bacteria against pathogens like MRSA and Candida albicans.
  • The conversion of H2O2 to ozone via SIgA represents a novel host defense mechanism in the oral cavity.
  • SIgA, in conjunction with indigenous bacteria and innate immunity, forms a significant system for maintaining oral homeostasis.

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