Staphylococcus aureus is a major cause of bovine chronic and subclinical mastitis, including abscess formation in the mammary gland. S. aureus hemolysins play a role in bacterial immune evasion and virulence. Our research indicates that 8. aureusvirulence locus, agr, a-, and 5- hemolysins modulate mammary epithelial cells (MAC-T) immune responses during extracellular and intracellular infections. S. aureus intracellular infections suppress MAC-T inflammatory and certain coagulatory gene expression. However, MAC-T thrombomodulin gene expression is induced by intracellular S. aureus after 12h post infection. Supernatants collected from S. aureus intracellularly infected or extracellularly stimulated MAC-T 24h post infection were used to stimulate polymorphonuclear (PMN) leukocytes to quantify gene expression. Interestingly, PMN stimulated with intracellularly infected MAC-T supernatants induced a stronger inflammatory response than extracellularly stimulated MAC-T supernatants. We hypothesized that MAC-T thrombomodulin activity during S. aureus infection induced PMN gene induction. To test this hypothesis, we measured generation of Activated Protein C (APC) on the surface of MAC-T. Post infection, bovine protein C and thrombin were added to MAC-T and incubated for lh. Substrate-2366 and hirudin were added to the MAC-T supernatants. Optical density readings were taken to measure APC concentration in the wells. Our results indicate that S. aureus agr and hemolysins influence thrombomodulin activity on the MAC-T during infection. Future research will focus on the effect of APC on bovine PMN function.
展开▼
