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Graduate Defense: Danielle Scarbrough

October 23 @ 10:30 am - 11:30 am MDT

Thesis Information

Title: Identification and Characterization of Candidate Staphylococcus Aureus Antigens for Inclusion in a Multivalent Bovine Mastitis Vaccine

Program: Master of Science in Biomolecular Sciences

Advisor: Dr. Juliette Tinker, Biological Sciences

Committee Members: Dr. Ken Cornell, Chemistry and Biochemistry and Dr. Brad Morrison, Biological Sciences

Abstract

Bovine mastitis, inflammation typically caused by bacterial infection, is the most prevalent disease affecting the global dairy industry. Staphylococcus aureus remains one of the most important pathogens implicated in the disease and can persist within herds at subclinical levels. A preventative S. aureus bovine mastitis vaccine would substantially lessen costs associated with treatment and restore revenue lost due to decreased milk production. One such experimental vaccine is the IsdA-CTA2/B + ClfA-CTA2/B vaccine, containing S. aureus antigens IsdA and ClfA chimeras, each fused to the nontoxic A2/B subunits of the cholera toxin which serves as an adjuvant. Previous clinical studies have indicated protective, but not fully preventative, effects following vaccination in cows. Additional antigens are required to increase vaccine efficacy. To identify priority candidate vaccine antigens, a combined proteomics and transcriptomics approach was implemented. S. aureus was cultured in traditional LB broth and, to replicate biological conditions in the bovine udder, skim milk. S. aureus extracts were subsequently analyzed by mass spectrometry and Next Generation RNA sequencing to measure unique surface proteins and upregulated genes in skim milk culture conditions. Selected candidates were further prioritized by subcellular localization to the cell periphery and by adhesin probability. Top candidate vaccine antigens identified include: fibrinogen-binding protein (Fib), bifunctional autolysin (Atl), thermonuclease (Nuc), autolysin/adhesin (Aaa), secretory antigen SsaA-like protein, and zinc ABC transporter substrate-binding protein.