Role of Endosomal TLRs in Staphylococcus aureus Infection

Identification of the receptors involved in innate immune recognition of Staphylococcus aureus, a major cause of morbidity and mortality in humans, is essential to develop alternative strategies to treat infections caused by anti-biotic-resistant strains. In the current study, we examine the role of endosomal TLRs, which sense the presence of prokaryotic-type nucleic acids, in anti staphylococcal host defenses using infection models involving genetically defective mice. Single deficiencies in TLR7, 9, or 13 resulted in mild or no decrease in host defenses. However, the simultaneous absence of TLR7, 9, and 13 resulted in markedly increased susceptibility to cutaneous and systemic S. aureus infection concomitantly with decreased production of proinflammatory chemokines and cytokines, neutrophil recruitment to infection sites, and reduced production of reactive oxygen species. This phenotype was significantly more severe than that of mice lacking TLR2, which senses the presence of staphylococcal lipoproteins. Notably, the combined absence of TLR7, 9, and 13 resulted in complete abrogation of IL-12 p70 and IFN-beta responses to staphylococcal stimulation in macrophages. Taken together, our data highlight the presence of a highly integrated endosomal detection system, whereby TLR7, 9, and 13 cooperate in sensing the presence of staphylococcal nucleic acids. We demonstrate that the combined absence of these receptors cannot be compensated for by cell surface-associated TLRs, such as TLR2, or cytosolic receptors. These data may be useful to devise strategies aimed at stimulating innate immune receptors to treat S. aureus infections.

Automated summary

Identification of the receptors involved in innate immune recognition of Staphylococcus aureus is essential for developing alternative strategies to treat infections caused by antibiotic-resistant strains. In this study, a highly integrated endosomal detection system involving TLR7, 9, and 13 was found to cooperate in sensing the presence of staphylococcal nucleic acids, with their combined absence leading to increased susceptibility to S. aureus infections and impaired immune responses. These findings suggest potential strategies for stimulating innate immune receptors to combat S. aureus infections.