噬菌体裂解酶细胞壁结合域V12CBD竞争结合自溶素的识别底物免疫保护金黄色葡萄球菌感染的分子机制

金黄色葡萄球菌是重要的人类病原菌，以金黄色葡萄球菌自身组分为核心抗原的疫苗均未能通过临床试验。寻找能诱发免疫保护作用的异源抗原可能是发展金黄色葡萄球菌疫苗的新途径。噬菌体裂解酶的细胞壁结合域可通过竞争性结合细菌自溶素的识别底物而成为理想的异源抗原。我们前期研究表明裂解酶细胞壁结合域V12CBD的抗血清可通过与自溶素AtlA-R1R2的交叉反应而特异结合金黄色葡萄球菌，从而提高免疫小鼠的存活率。本项目拟在此基础上，鉴定金黄色葡萄球菌AtlA-R1R2的识别底物，揭示V12CBD与其交叉结合的物质基础；揭示V12CBD抗血清激活补体免疫，促进调理吞噬的分子机制；并建立小鼠模型系统探究V12CBD免疫保护作用的有效性和广谱性。本项目的顺利实施不仅能阐明V12CBD免疫保护金黄色葡萄球菌感染的分子机制，而且可为金黄色葡萄球菌疫苗的研制提供新思路、新途径，具有重要的理论意义和实际意义。

Staphylococcus aureus is an important human pathogen, and all vaccines that contains core antigens from S. aureus have failed in clinical trials. It is assumed a novel way for developing S. aureus vaccines by using heterologous antigen that derives from non-S. aureus species but can elicit effect immune response. In this regard, the cell-wall binding domains of bacteriophage lysins, which can recognize the conserved elements on the cell wall surface of target bacteria and could compete the binding site of autolysin, could serve as an ideal source. Our previous studies showed that the cell-wall binding domain of the PlyV12 lysin, V12CBD, could generate antibodies with high specificity for S. aureus and immunoprotects mice from lethal S. aureus infection after vaccination. In this project, we plan to identify the substrate of the major autolysin of S. aureus, AtlA, and evaluate its cross-reaction with V12CBD; reveal the mechanism underlying the activation of complement system and opsonophagocytosis of anti-V12CBD serum and anti-V12CBD nanobody; and evaluate the immunoprotective efficacy of V12CBD in mouse sepsis, pneumonia, and passive immune models using S. aureus isolates with different SCCmec types. Successful complementation of this project will not only unveil the substrate and the molecular mechanism underlying the vaccination effect of V12CBD, but could also open a novel way for developing S. aureus vaccines.