Impact of Glycan Linkage to Wall Teichoic Acid on Langerin Recognition and Langerhans Cell Activation.

is the leading cause of skin and soft tissue infections. It remains incompletely understood how skin-resident immune cells respond to invading and contribute to an effective immune response. Langerhans cells (LCs), the only professional antigen-presenting cell type in the epidermis, sense through their pattern-recognition receptor langerin, triggering a proinflammatory response. Langerin recognizes the β-1,4-linked -acetylglucosamine (β1,4-GlcNAc) but not α-1,4-linked GlcNAc (α1,4-GlcNAc) modifications, which are added by dedicated glycosyltransferases TarS and TarM, respectively, on the cell wall glycopolymer wall teichoic acid (WTA). Recently, an alternative WTA glycosyltransferase, TarP, was identified, which also modifies WTA with β-GlcNAc but at the C-3 position (β1,3-GlcNAc) 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. Using genetically modified strains, we observed that langerin similarly recognized bacteria that produce either TarS- or TarP-modified WTA, yet -expressing induced increased cytokine production and maturation of -generated LCs compared to -expressing . Chemically synthesized WTA molecules, representative of the different WTA glycosylation patterns, were used to identify langerin-WTA binding requirements. We established that β-GlcNAc is sufficient to confer langerin binding, thereby presenting synthetic WTA molecules as a novel glycobiology tool for structure-binding studies and for elucidating molecular pathogenesis. Overall, our data suggest that LCs are able to sense all β-GlcNAc-WTA producing strains, likely performing an important role as first responders upon skin invasion.