Identifying mucin O-glycans in the regulation of Staphylococcus aureus pathogenesis

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PROJECT SUMMARY/ABSTRACT The goal of this project is to leverage mucin O-glycans as potent natural compounds that suppress biofilm formation, aggregation, and other important virulence genes and pathways in the opportunistic pathogen Staphylococcus aureus (S. aureus). S. aureus causes numerous debilitating infections and is successful at persisting as robust biofilms. Biofilms are difficult to eradicate because they are able to evade host immunity, are tolerant to antimicrobials, and increase antibiotic-resistance emergence. Therapeutic strategies to suppress and prevent the S. aureus biofilm formation are urgently needed. Mucus functions as a key defense mechanism on epithelial linings of numerous organ systems and it can suppress numerous important virulence responses of S. aureus via the glycans displayed on mucin polymers. Therefore, mucus has strong potential for the development of new approaches to combat this problematic pathogen. Mucin polypeptide backbones are grafted with several hundred unique glycan structures. Their exceptional potential for virulence-attenuation of mucin- associated glycans has been recognized for some time, but because their individual bioactivities have been intractable to analysis, their potential has barely been tapped. We will close this gap by harnessing our collective expertise in microbiology, mucin biology, glycan chemistry, and in vivo infection models to identify single and small groups of mucin glycans that inhibit S. aureus biofilm formation and aggregation. Our pilot data strongly support the premise and feasibility of this study: mucin glycans suppress virulence genes involved with S. aureus biofilm formation, clumping/aggregation, and toxin-mediated lysis of human neutrophils, all of which are important in infection. These findings support a central role for mucin glycans in host protection and provide the impetus to identify glycan structures responsible for the anti-virulence effects. Our goal is to provide much- needed virulence-attenuating molecules to manage this problematic pathogen, drawn from the rich and untapped natural library of biological glycans underlying host defense. We will combine functional glycan analysis, microbiology, and in vivo infection studies to identify regulatory mucin O-glycans that impede S. aureus virulence. In Aim 1, we will harvest bioactive glycans from mucins to generate annotated libraries for functional analysis and identify those O-glycans that attenuate S. aureus biofilm formation and aggregation. In Aim 2, we will investigate the anti-virulence effects of mucin O-glycans in well-established human neutrophil- and in vivo infection models. This project is significant because it will empower us to elucidate and harness the myriad biological functions of glycans and mucins on S. aureus and its host. This proposal also sets a firm experimental groundwork that could lead to pivotal changes in the prevention and treatment of S. aureus infection. Moreover, many well-known antibiotics contain glycans as part of their core structure. Therefore, successful identification and in vivo validation of O-glycans that attenuate S. aureus virulence has the potential to create exciting new glycan-based or -mimetic therapeutics that enhance, or even replace, the use of antibiotics.