SummaryStaphylococcus aureus is a major cause of skin and soft tissue infections and aggravator of the inflammatory skin disease atopic dermatitis (AD). Langerhans cells (LCs) initiate a Th17 response upon exposure to S. aureus, which contributes to host defense but also to AD pathogenesis. However, the molecular mechanisms underlying the unique pro-inflammatory capacities of S. aureus remain unclear. We demonstrate that human LCs directly interact with S. aureus through the pattern-recognition receptor langerin (CD207), which specifically recognizes the conserved β-N-acetylglucosamine (GlcNAc) modifications of wall teichoic acid (WTA) that are not expressed by other staphylococcal species. The WTA glycoprofile strongly influences the production of Th1-and Th17-polarizing cytokines by LCs. Specifically, β-GlcNAc activates LCs, whereas co-decoration of WTA with α-GlcNAc through the enzyme TarM, uniformly present in the AD-associated CC1 lineage, attenuates LC immune activation. Our findings provide important mechanistic insights into the role of S. aureus in inflammatory skin disease.
Staphylococcus aureus is the leading cause of skin and soft tissue infections. It remains incompletely understood how skin-resident immune cells respond to S. aureus invasion and contribute to an effective immune response. Langerhans cells (LCs), the only professional antigen-presenting cell type in the epidermis, sense S. aureus through their pattern-recognition receptor langerin, triggering a pro-inflammatory response. Langerin specifically recognizes the β-1,4-linked N-acetylglucosamine (β-GlcNAc) modification, which requires the glycosyltransferase TarS, on the cell wall glycopolymer Wall Teichoic Acid (WTA). Recently, an alternative WTA glycosyltransferase, TarP, was identified in methicillin-resistant S. aureus strains belonging to clonal complexes (CC) 5 and CC398. TarP also modifies WTA with β-GlcNAc but at the C-3 position of the WTA ribitol phosphate (RboP) subunit. Here, we aimed to unravel the impact of β-GlcNAc linkage position for langerin binding and LC activation. In addition, we performed structure-binding studies using a small panel of unique chemically-synthesized WTA molecules to assess langerin-WTA binding requirements. Using FITC-labeled recombinant human langerin and genetically-modified S. aureus strains, we observed that langerin similarly recognized bacteria that produce either TarS- or TarP-modified WTA. Furthermore, using chemically-synthesized WTA, representative of the different S. aureus WTA glycosylation patterns, established that β-GlcNAc is sufficient to confer langerin binding. Functionally, tarP-expressing S. aureus induce increased cytokine production and maturation of in vitro-generated LCs compared to tarS-expressing S. aureus. Overall, our data suggest that LCs are able to sense all β-GlcNAc-WTA producing S. aureus strains, likely performing an important role as first responders upon S. aureus skin invasion.
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