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Wall Teichoic Acid Deficiency in Staphylococcus aureus Confers Selective Resistance to Mammalian Group IIA Phospholipase A₂ and Human β-Defensin 3

Inflammation Program,¹ Departments of Microbiology,² Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa,³ Veterans' Administration Medical Center, Iowa City, Iowa 52242,⁴ Channing Laboratory, Brigham and Women's Hospital, and Harvard Medical School, Boston, Massachusetts 02134,⁵ Cellular and Molecular Microbiology, Department of Medical Microbiology and Hygiene, University Hospitals Tübingen, 72076 Tübingen, Germany⁶

Received 20 December 2007/ Returned for modification 30 January 2008/ Accepted 2 March 2008

Wall teichoic acids (WTAs) and membrane lipoteichoic acids (LTAs) are the major polyanionic polymers in the envelope of Staphylococcus aureus. WTAs in S. aureus play an important role in bacteriophage attachment and bacterial adherence to certain host cells, suggesting that WTAs are exposed on the cell surface and could also provide necessary binding sites for cationic antimicrobial peptides and proteins (CAMPs). Highly cationic mammalian group IIA phospholipase A₂ (gIIA PLA₂) kills S. aureus at nanomolar concentrations by an action(s) that depends on initial electrostatic interactions, cell wall penetration, membrane phospholipid (PL) degradation, and activation of autolysins. A tagO mutant of S. aureus that lacks WTA is up to 100-fold more resistant to PL degradation and killing by gIIA PLA₂ and CAMP human β-defensin 3 (HBD-3) but has the sensitivity of the wild type (wt) to other CAMPs, such as Magainin II amide, hNP1-3, LL-37, and lactoferrin. In contrast, there is little or no difference in either gIIA PLA₂ activity toward cell wall-depleted protoplasts of the wt and tagO strains of S. aureus or in binding of gIIA PLA₂ to wt and tagO strains. Scanning and transmission electron microscopy reveal increased surface protrusions in the S. aureus tagO mutant that might account for reduced activity of bound gIIA PLA₂ and HBD-3 toward the tagO mutant. In summary, the absence of WTA in S. aureus causes a selective increase in bacterial resistance to gIIA PLA₂ and HBD-3, the former apparently by reducing access and/or activity of bound antibacterial enzyme to the bacterial membrane.

Published ahead of print on 17 March 2008.

Editor: J. B. Bliska