Earliest Communication Between S. uberis and the Host

S. uberis, a member of the pyogenic cluster of Streptococcus, is commonly isolated as a cause of intramammary infection and mastitis in dairy cattle, worldwide. Bovine mastitis is a common reason for the administration of therapeutic antibiotics within dairy prodution1,2. Mastitis reduces milk yields by 600-1200kg per affected animal per year3; creating inefficiencies resulting in the need for greater number of animals. Ruminants are a common source of greenhouse gases and inefficiency due to mastitis in the UK alone can be considered contribute an additional 1 million tonnes CO2e/year. Infections leading to this disease therefore pose an environmental, AMR, and economic challenge to the dairy industry. Invading pathogens are typically detected by the host via pattern recognition receptors (PRRs). Pathogen-associated molecular patterns (PAMPs) such as LPS or dsRNA, originating from the pathogen, are recognised by PRRs. This initiates a signalling cascade guiding the formation of the inflammasome and generation of inactive "pro" forms of pro-inflammatory cytokines such as pro-IL-1beta and pro-IL-18 - thereby "priming" the inflammasome. Secondary activating signals such as extracellular ATP, particulate crystals4, or the M protein of S. pyogenes5 then cause caspase-mediated cleavage and maturation of pro-inflammatory cytokines and chemokines. Neutrophils are commonly recruited to sites of inflammation by the chemoattractive chemokine, CXCL86. Pro-inflammatory cytokines can also cause maturation of further inflammasomes in nearby cells, amplifying the local inflammatory response. We have recently elucidated the mechanism describing how S. uberis initiates the inflammasome reaction in mammary macrophage and paradoxically this appears to promote bacterial colonisation and disease pathology. This project would further this area of investigation by: (i) determining the bacterial components involved in immune priming and inflammasome triggering and (ii) determining the output from the bovine macrophage that communicates with other local leukocytes and or mammary epithelial tissue References 1. Su, S. et al. UK Veterinary Antibiotic Resistance and Sales Surveillance UK-VARSS 2014. (2014). 2. Veterinary Medicines Directorate, A. and P. H. A. UK Veterinary Antibiotic Resistance and Sales Surveillance UK-VARSS 2018. www.gov.uk/government/collections/veterinary-antimicrobial-resistance-and-sales-surveillance. (2019). 3. Wilson, D. J. et al. Effect of Clinical Mastitis on the Lactation Curve: A Mixed Model Estimation Using Daily Milk Weights. J. Dairy Sci. 87, 2073-2084 (2004). 4. Bauernfeind, F. G. et al. Cutting Edge: NF-kB Activating Pattern Recognition and Cytokine Receptors License NLRP3 Inflammasome Activation by Regulating NLRP3 Expression. J. Immunol. 183, 787-791 (2009). 5. Valderrama, J. A. et al. Group A streptococcal M protein activates the NLRP3 inflammasome. Nat. Microbiol. 2, 1425-1434 (2017). 6. de Oliveira, S. et al. Cxcl8 (IL-8) Mediates Neutrophil Recruitment and Behavior in the Zebrafish Inflammatory Response. J. Immunol. 190, 4349-4359 (2013).