金黄色葡萄球菌（S. aureus）是目前影响我国奶牛乳房炎的重要致病菌。噬菌体作为一种新型的抗耐药致病菌的潜在抗菌剂正受到广泛关注。前期研究发现噬菌体vB_SauM_JS25能显著抑制胞内S. aureus定殖，且能通过Toll样受体2（TLR2）途径下调S. aureus诱导的IL-6等细胞因子的表达。本研究拟采用牛乳腺上皮细胞系 MAC-T，以TLR2配体LTA代替细菌感染，通过对IL-6等细胞因子及TLR2信号通路中MAPK和NF-κB相关磷酸化蛋白的表达定量检测，明确噬菌体调节S. aureus诱导的先天性免疫信号通路。在此基础上，利用生物信息学分析含Ig样结构域的噬菌体蛋白，通过体内外实验测定其对TLR2信号通路中MAPK和NF-κB及其对S. aureus定殖的影响，进一步探索噬菌体调控S. aureus诱导TLR2信号通路的功能蛋白，丰富噬菌体抗感染机制理论基础。

Staphylococcus aureus (S. aureus) is recognized as one of the most major pathogens causing bovine mastitis. Bacteriophage is a new potential antimicrobial that deal with resistant pathogen. The previous study found that phage vB_SauM_JS25 could significantly inhibit intracellular S. aureus colonization, and can reduced S. aureus-induced the expression of TNF-α, IL-1β, and IL-6 mediated by Toll-like receptor 2 (TLR2) pathway. In this study, bovine mammary epithelial cells (MAC-T) will be stimulated with TLR2 ligand-LTA instead of bacterial infection, and then infected with phage, quantitative analysis will be utilized to detect the expression of several cytokines, the level of proteins in MAPK (p38, JNK and ERK1/2) and NF-κB (p65, IκBα) pathway, which helps to understand the phage regulates innate immune signaling pathways induced by S. aureus. The Ig-like domain in phage genome will be analyzed by PSI-BLAST, then the phage capsid proteins containing Ig-like domain will be expressed by eukaryotic expression system. After transfected with recombinant plasmid, we will measure the levels and phosphorylation of MAPK and NF-κB and its impact on the colonization of S. aureus, that could clarify which protein of phage regulates S. aureus induced innate immune. Furtherly we will verify the function of screened phage proteins in the mouse mammary. These results will indicate the molecular mechanism of phage regulates TLR2 signal transduction pathways induced by S. aureus, enrich antibacterial mechanism of the phage and provide new ideas for the prevention of bovine mastitis.