Staphylococcus aureus ATP Synthase Promotes Biofilm Persistence by Influencing Innate Immunity

Abstract

Staphylococcus aureus is a major cause of prosthetic joint infection (PJI), which is characterized by biofilm formation. S. aureus biofilm skews the host immune response toward an anti-inflammatory profile by the increased recruitment of myeloid-derived suppressor cells (MDSCs) that attenuate macrophage proinflammatory activity, leading to chronic infection. A screen of the Nebraska Transposon Mutant Library identified several hits in the ATP synthase operon that elicited a heightened inflammatory response in macrophages and MDSCs, including atpA, which encodes the alpha subunit of ATP synthase. An atpA transposon mutant (ΔatpA) had altered growth kinetics under both planktonic and biofilm conditions, along with a diffuse biofilm architecture that was permissive for leukocyte infiltration, as observed by confocal laser scanning microscopy. Coculture of MDSCs and macrophages with ΔatpA biofilm elicited significant increases in the proinflammatory cytokines interleukin 12p70 (IL-12p70), tumor necrosis factor alpha (TNF-α), and IL-6. This was attributed to increased leukocyte survival resulting from less toxin and protease production by ΔatpA biofilm as determined by liquid chromatography with tandem mass spectrometry (LC-MS/MS). The enhanced inflammatory response elicited by ΔatpA biofilm was cell lysis-dependent since it was negated by polyanethole sodium sulfanate treatment or deletion of the major autolysin, Atl. In a mouse model of PJI, ΔatpA-infected mice had decreased MDSCs concomitant with increased monocyte/macrophage infiltrates and proinflammatory cytokine production, which resulted in biofilm clearance. These studies identify S. aureus ATP synthase as an important factor in influencing the immune response during biofilm-associated infection and bacterial persistence. IMPORTANCE Medical device-associated biofilm infections are a therapeutic challenge based on their antibiotic tolerance and ability to evade immune-mediated clearance. The virulence determinants responsible for bacterial biofilm to induce a maladaptive immune response remain largely unknown. This study identified a critical role for S. aureus ATP synthase in influencing the host immune response to biofilm infection. An S. aureus ATP synthase alpha subunit mutant (ΔatpA) elicited heightened proinflammatory cytokine production by leukocytes in vitro and in vivo, which coincided with improved biofilm clearance in a mouse model of prosthetic joint infection. The ability of S. aureus ΔatpA to augment host proinflammatory responses was cell lysis-dependent, as inhibition of bacterial lysis by polyanethole sodium sulfanate or a ΔatpAΔatl biofilm did not elicit heightened cytokine production. These studies reveal a critical role for AtpA in shaping the host immune response to S. aureus biofilm.

Staphylococcus aureus Protection-Related Type 3 Cell-Mediated Immune Response Elicited by Recombinant Proteins and GM-CSF DNA Vaccine

“…In this latter study, we searched the antibodies produced by dairy cows which were exposed to S. aureus but remained healthy, hypothesizing that the antibodies repertoire directed against these specific S. aureus proteins contributed to mastitis resistance. The first S. aureus protein, the so-called SAS protein, plays a pivotal role in dictating biofilm growth and structure [ 33 ], enhances tolerance of S. aureus towards some host antimicrobial peptides of the innate immunity [ 34 ], inhibits pro-inflammatory cytokine production by monocyte-derived macrophages and myeloid-derived suppressor cells, and renders S. aureus more resistant to the bactericidal activity of monocyte-derived macrophages [ 33 ]. The second S. aureus SDD protein is critical for bacteria survival and proliferation.…”

Understanding the Role of the Antioxidant Drug Erdosteine and Its Active Metabolite on Staphylococcus aureus Methicillin Resistant Biofilm Formation

“…The most upregulated protein was the ATP synthase gamma chain (AtpG). AtpG belongs to the ATP synthase operon, the genes of which encode the subunits of the ATP synthase catalytic core, the central metabolic protein driven by the proton motive force generated by the respiratory chain [ 42 ]. With regard to S. aureus , a recent study identified that AtpG was needed for virulence in a mouse model of skin and soft tissue infection.…”

<em>Staphylococcus aureus</em> Protection-Related Type 3 Cell-Mediated Immune Response Elicited by Recombinant Proteins and GM-CSF DNA Vaccine

“…In this latter study, we searched the antibodies produced by dairy cows exposed to S. aureus but remained healthy, hypothesizing that the antibodies repertoire directed against these specific S. aureus proteins contributed to mastitis resistance. The first S. aureus protein, socalled SAS protein, plays a pivotal role in dictating biofilm growth and structure [33], enhances tolerance of S. aureus towards some host antimicrobial peptides of the innate immunity [34], inhibits pro-inflammatory cytokines production by monocyte-derived macrophages and myeloid-derived suppressor cells and renders S. aureus more resistant to the bactericidal activity of monocyte-derived macrophages [33]. The second S. aureus SDD protein is critical for bacteria survival and proliferation.…”