Host chemokines bind to Staphylococcus aureus and stimulate protein A release

Area of Science:

• Microbiology
• Immunology
• Pathogen-host interactions

Background:

• Host-derived signals rarely benefit bacterial pathogens during infection.
• Understanding bacterial virulence factor regulation is crucial for developing effective treatments.

Purpose of the Study:

• To investigate if host immunoregulatory chemokines influence the release of virulence factors from community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA).
• To elucidate the mechanism and implications of chemokine-induced virulence factor release in CA-MRSA infections.

Main Methods:

• Screening of 42 host immunoregulatory chemokines for their ability to induce Staphylococcus protein A (SPA) release from CA-MRSA.
• Detailed mechanistic studies on chemokine CXCL9-induced SPA release, including investigation of bacterial density, post-translational modification, and chemokine binding.
• Analysis of clinical samples from patients and a mouse model to detect extracellular SPA and relevant chemokines in infected tissues.

Main Results:

• 31 out of 42 tested chemokines induced SPA release from CA-MRSA.
• CXCL9 induced SPA release via a post-translational mechanism inversely proportional to bacterial density.
• CXCL9 and CXCL10 specifically bound to CA-MRSA cell membranes and cell walls, respectively.
• Extracellular SPA and SPA-releasing chemokines were detected in human clinical samples and a mouse model of CA-MRSA skin abscess.

Conclusions:

• Host immunoregulatory chemokines can induce virulence factor release in CA-MRSA, representing a novel immune evasion strategy.
• The binding of chemokines to CA-MRSA suggests a potential scavenging function contributing to immune evasion.
• This interaction highlights a unique mechanism where pathogens exploit host defense molecules to enhance their survival and virulence.