2型猪链球菌脑膜炎小鼠模型的构建及其转录组学分析

Establishment and transcriptomic analysis of the mouse model of meningitis caused by Streptococcus suis serotype 2

摘要:

【背景】2型猪链球菌(Streptococcus suis serotype 2, S. suis 2)可感染宿主引起严重的脑膜炎，对养猪业和人类公共卫生安全构成重大威胁。【目的】构建S. suis 2感染小鼠脑膜炎模型，并对其脑组织进行转录组学分析，为揭示S. suis 2感染宿主后引起脑膜炎的分子机制和发现潜在的治疗靶点提供理论依据。【方法】采用S. suis 2感染小鼠，并对其脑组织进行病理组织学分析确认构建脑膜炎小鼠后，对其脑组织进行转录组学分析，对比S. suis 2感染和未感染小鼠的差异表达基因，并对差异表达基因进行基因本体论(gene ontology, GO)功能、京都基因和基因组百科全书(Kyoto encyclopedia of genes and genomes, KEGG)通路富集和韦恩分析。【结果】脑病理组织学分析结果显示，S. suis 2感染的小鼠脑膜中有大量的炎症细胞浸润，并且血管周围出现“袖套”现象，并能从感染小鼠的组织器官中再分离出攻毒的S. suis 2菌株，结果证明构建了S. suis 2感染脑膜炎小鼠模型。转录组学分析结果表明，感染S. suis 2与未感染的小鼠相比，存在397条差异表达基因，其中109个基因表达水平下调，288个基因表达水平上调。GO功能富集分析表明，差异表达基因主要富集于细胞成分功能中的细胞质和细胞质膜，生物过程功能中的信号传导、转录调控、凋亡过程、系统免疫和对细菌的应答，以及分子功能中的蛋白结合。KEGG通路富集分析表明差异表达基因主要富集于多个重要的信号通路，包括细胞因子-细胞因子受体相互作用、免疫应答相关通路、凋亡通路、细胞吞噬和代谢等。韦恩分析显示，脑源神经营养因子(brain derived neurotrophic factor, bdnf)基因交会于脑膜炎关联基因集、耳聋关联基因集和S. suis 2感染差异表达基因集，且表达显著下调；c4b、fas、icam1、cxcl1、csf3、lrg1和nde1基因交会于脑膜炎关联基因集和S. suis 2感染差异表达基因集，且表达均显著上调。【结论】本研究构建了S.suis 2感染的小鼠脑膜炎模型，并对脑组织进行了转录组学分析，揭示了S. suis 2感染后小鼠脑中多个重要的差异表达基因和分子信号通路，并绘制了分子信号通路网络，为S. suis 2感染引起脑膜炎的分子机制研究提供了新的理论依据和潜在的治疗靶点。

关键词:2型猪链球菌;感染;脑膜炎;转录组学;免疫反应

Abstract:

[Background] Streptococcus suis serotype 2 (S. suis 2) causes severe meningitis in the host, posing a major threat to the pig industry and human public health. [Objective] The mouse model of meningitis induced by S. suis 2 infection was established, and its brain tissue was analyzed by transcriptomics to provide a theoretical basis for revealing the molecular mechanism of meningitis caused by S. suis 2 infection in mouse and discovering potential therapeutic targets.[Methods] S. suis 2 was used to infect mouse, and the histopathological changes in the mouse brain tissue were observed to verify the model of meningitis in mouse was successfully established. Furthermore, transcriptomic analysis was performed to identify the differentially expressed genes (DEGs) between the S. suis 2-infected and uninfected mouse. Moreover, gene ontology (GO) functional annotation, Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis, and Venn analysis were performed for the DEGs. [Results] S. suis 2 successfully infected mouse and caused meningitis. The brain of the infected mouse showed infiltration of massive inflammatory cells and perivascular cuffing around the blood vessels. Moreover, the S. suis 2 strain was isolated from the tissues of the modeled mouse. The results proved that the mouse model of meningitis caused by S. suis 2 infection was successfully established. A total of 397 DEGs were identified, including 109 genes with down-regulated expression and 288 genes with up-regulated expression. GO functional annotation showed that the DEGs were mainly enriched in the cytoplasm, plasma membrane, signal transduction, regulation of transcription, apoptotic process, immune system process, response to bacteria, and protein binding. KEGG pathway enrichment analysis indicated that the DEGs were mainly enriched in multiple important signaling pathways regulating host cytokine-cytokine receptor interaction, immune response, apoptosis, phagocytosis, and metabolism. The Venn analysis showed that the brain-derived neurotrophic factor (bdnf) gene converged in meningitis-related genes set, deafness-related genes set, and DEGs set of S. suis 2 infection, with significantly down-regulated expression. The c4b, fas, icam1, cxcl1, csf3, lrg1, and nde1 genes converged in the meningitis-related genes set and the DEGs set of S. suis 2 infection, with significantly up-regulated expression. [Conclusion] A mouse model of meningitis induced by S. suis 2 infection was successfully established. The transcriptomics of the brain tissue of the model mouse revealed several key DEGs and signaling pathways, and the molecular signaling pathway network was built. The findings provide a new theoretical basis for revealing the molecular mechanism of S. suis 2 induced-meningitis and exploring potential therapeutic targets.

Key words:Streptococcus suis serotype 2;infection;meningitis;transcriptomics;immune response