Interactions between the major structural glycoprotein E2 of classical swine fever virus (CSFV) with host proteins have been identified as important factors affecting virus replication and virulence. Previously, using the yeast two-hybrid system, we identified swine host proteins specifically interacting with CSFV E2. In this report, we use a proximity ligation assay to demonstrate that swine host protein CCDC115 interacts with E2 in CSFV-infected swine cells. Using a randomly mutated E2 library in the context of a yeast two-hybrid methodology, specific amino acid mutations in the CSFV E2 protein responsible for disrupting the interaction with CCDC115 were identified. A recombinant CSFV mutant (E2ΔCCDC115v) harboring amino acid changes disrupting the E2 protein interaction with CCDC115 was produced and used as a tool to assess the role of the E2-CCDC115 interaction in viral replication and virulence in swine. CSFV E2ΔCCDC115v showed a slightly decreased ability to replicate in the SK6 swine cell line and a greater replication defect in primary swine macrophage cultures. A decreased E2-CCDC115 interaction detected by PLA is observed in cells infected with E2ΔCCDC115v. Importantly, animals intranasally infected with 105 TCID50 of E2ΔCCDC115v experienced a significantly longer survival period when compared with those infected with the parental Brescia strain. This result would indicate that the ability of CSFV E2 to bind host CCDC115 protein during infection plays an important role in virus replication in swine macrophages and in virus virulence during the infection in domestic swine.

中文翻译：

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病毒复制过程中，包含猪宿主蛋白卷曲螺旋域的115（CCDC115）与经典猪瘟病毒结构糖蛋白E2相互作用。

已确定经典猪瘟病毒（CSFV）的主要结构糖蛋白E2与宿主蛋白之间的相互作用是影响病毒复制和毒力的重要因素。以前，我们使用酵母双杂交系统，鉴定了与CSFV E2特异性相互作用的猪宿主蛋白。在本报告中，我们使用邻近连接测定法来证明猪宿主蛋白CCDC115与CSFV感染的猪细胞中的E2相互作用。在酵母双杂交方法的背景下，使用随机突变的E2文库，鉴定了CSFV E2蛋白中负责破坏与CCDC115相互作用的特定氨基酸突变。产生了具有氨基酸变化从而破坏E2蛋白与CCDC115相互作用的重组CSFV突变体（E2ΔCCDC115v），并将其用作评估E2-CCDC115相互作用在猪病毒复制和毒力中的作用的工具。CSFVE2ΔCCDC115v在SK6猪细胞系中的复制能力略有降低，而在原代猪巨噬细胞培养物中的复制缺陷则更大。在用E2ΔCCDC115v感染的细胞中观察到PLA检测到的E2-CCDC115相互作用降低。重要的是，与感染亲本布雷西亚毒株的动物相比，经鼻内感染105 TCID50的E2ΔCCDC115v的动物经历了明显更长的生存期。