Suppression of the inflammatory immune response prevents the development of chronic biofilm infection due to methicillin-resistant Staphylococcus aureus

Infect Immun. 2011 Dec;79(12):5010-8. doi: 10.1128/IAI.05571-11. Epub 2011 Sep 26.

Abstract

Staphylococcus aureus is a common cause of prosthetic implant infections, which can become chronic due to the ability of S. aureus to grow as a biofilm. Little is known about adaptive immune responses to these infections in vivo. We hypothesized that S. aureus elicits inflammatory Th1/Th17 responses, associated with biofilm formation, instead of protective Th2/Treg responses. We used an adapted mouse model of biofilm-mediated prosthetic implant infection to determine chronic infection rates, Treg cell frequencies, and local cytokine levels in Th1-biased C57BL/6 and Th2-biased BALB/c mice. All C57BL/6 mice developed chronic S. aureus implant infection at all time points tested. However, over 75% of BALB/c mice spontaneously cleared the infection without adjunctive therapy and demonstrated higher levels of Th2 cytokines and anti-inflammatory Treg cells. When chronic infection rates in mice deficient in the Th2 cytokine interleukin-4 (IL-4) via STAT6 mutation in a BALB/c background were assessed, the mice were unable to clear the S. aureus implant infection. Additionally, BALB/c mice depleted of Treg cells via an anti-CD25 monoclonal antibody (MAb) were also unable to clear the infection. In contrast, the C57BL/6 mice that were susceptible to infection were able to eliminate S. aureus biofilm populations on infected intramedullary pins once the Th1 and Th17 responses were diminished by MAb treatment with anti-IL-12 p40. Together, these results indicate that Th2/Treg responses are mechanisms of protection against chronic S. aureus implant infection, as opposed to Th1/Th17 responses, which may play a role in the development of chronic infection.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Antibodies, Monoclonal / therapeutic use
  • Biofilms / growth & development*
  • Chronic Disease
  • Immunity, Innate
  • Inflammation / prevention & control*
  • Interleukin-12 Subunit p40 / immunology
  • Interleukin-6 / immunology
  • Methicillin-Resistant Staphylococcus aureus / physiology*
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Prostheses and Implants / microbiology
  • STAT6 Transcription Factor / genetics
  • STAT6 Transcription Factor / metabolism
  • Staphylococcal Infections / immunology*
  • Staphylococcal Infections / microbiology
  • T-Lymphocytes, Regulatory / immunology
  • Th2 Cells / physiology

Substances

  • Antibodies, Monoclonal
  • Interleukin-12 Subunit p40
  • Interleukin-6
  • STAT6 Transcription Factor
  • Stat6 protein, mouse