Streptococcus suis serotype 2 (SS2) is a serious zoonotic pathogen; it can lead to symptoms of streptococcal toxic shock syndrome (STSS) in humans and sepsis in pigs, and poses a great threat to public health. The SS2 MetQ gene deletion strain has attenuated antiphagocytosis, although the mechanism of antiphagocytosis and pathogenesis of MetQ in SS2 has remained unclear. In this study, stable isotope labeling by amino acids in cell culture (SILAC) based liquid chromatography–mass spectrometry (LC–MS) and subsequent bioinformatics analysis was used to determine differentially expressed proteins of RAW264.7 cells infected with △MetQ and ZY05719. Proteomic results were verified by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting for selected proteins. Further research was focused mainly on immune system processes related to downregulated proteins, such as Src and Ccl9, and actin cytoskeleton and endocytosis related upregulated proteins, like Pstpip1 and Ppp1r9b. The proteomic results in this study shed light on the mechanism of antiphagocytosis and innate immunity of macrophages infected with △MetQ and ZY05719, which might provide novel targets to prevent or control the infection of SS2.

猪链球菌血清型2（SS2）是一种严重的人畜共患病原体。它可以导致人链球菌中毒性休克综合症（STSS）症状和猪败血症，对公众健康构成巨大威胁。尽管尚不清楚SS2 MetQ基因缺失菌株的抗吞噬作用机理和MetQ在SS2中的发病机理，但SS2 MetQ基因缺失菌株已经减弱了其抗吞噬作用。在这项研究中，使用基于细胞培养（SILAC）的液相色谱-质谱（LC-MS）中氨基酸的稳定同位素标记以及随后的生物信息学分析来确定感染△ MetQ的RAW264.7细胞的差异表达蛋白。和ZY05719。蛋白质组学结果通过定量实时聚合酶链反应（qRT-PCR）和蛋白质印迹法进行了验证。进一步的研究主要集中在与下调的蛋白（例如Src和Ccl9）以及肌动蛋白细胞骨架和内吞作用相关的上调的蛋白（例如Pstpip1和Ppp1r9b）相关的免疫系统过程。这项蛋白质组学研究结果揭示了被△ MetQ和ZY05719感染的巨噬细胞的抗吞噬作用和先天免疫的机制，这可能为预防或控制SS2的感染提供了新的靶点。