Surface Glycopolymers Are Crucial for In Vitro Anti-Wall Teichoic Acid IgG-Mediated Complement Activation and Opsonophagocytosis of Staphylococcus aureus.

The cell envelopes of many Gram-positive bacteria contain wall teichoic acids (WTA). Staphylococcus aureus WTAs are composed of ribitol phosphate (RboP) or glycerol phosphate (GroP) backbones substituted with D-alanine and N -acetyl-D-glucosamine (GlcNAc) or N -acetyl-D-galactosamine (GalNAc). Two WTA glycosyltransferases, TarM and TarS, are responsible for modifying RboP WTA with α-GlcNAc and β-GlcNAc, respectively. Recently we reported that purified human serum anti-WTA IgG specifically recognizes β-GlcNAc of staphylococcal RboP WTA and then facilitates complement C3 deposition and opsonophagocytosis of S. aureus laboratory strains. This prompted us to examine whether anti-WTA IgG can induce C3 deposition on a diverse set of clinical S. aureus isolates. To this end, we compared anti-WTA IgG-mediated C3 deposition and opsonophagocytosis abilities using 13 different staphylococcal strains. Of note the majority of S. aureus strains tested was recognized by anti-WTA IgG, resulting in C3 deposition and opsonophagocytosis. A minority of strains was not recognized by anti-WTA IgG, which correlated either with extensive capsule production or alteration in the WTA glycosylation pattern. Our results demonstrate that the presence of TarS-mediated β-GlcNAcylated WTA in clinically isolated S. aureus strains is an important factor for induction of anti-WTA IgG-mediated C3 deposition and opsonophagocytosis.