Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QP, UK.
Department of Virology, Faculty of Medicine, Imperial College London, St. Mary's Campus, London W2 1PG, UK.
J Gen Virol. 2013 Jul;94(Pt 7):1647-1657. doi: 10.1099/vir.0.052670-0. Epub 2013 Apr 11.
Vaccinia virus (VACV) encodes many proteins that antagonize the innate immune system including a family of intracellular proteins with a B-cell lymphoma (Bcl)-2-like structure. One of these Bcl-2 proteins called K7 binds Toll-like receptor-adaptor proteins and the DEAD-box RNA helicase DDX3 and thereby inhibits the activation of NF-κB and interferon regulatory factor 3. However, the contribution of K7 to virus virulence is not known. Here a VACV lacking the K7R gene (vΔK7) was constructed and compared with control viruses that included a plaque purified wt (vK7), a revertant with the K7R gene reinserted (vK7-rev) and a frame-shifted virus in which the translational initiation codon was mutated to prevent K7 protein expression (vK7-fs). Data presented show that loss of K7 does not affect virus replication in cell culture or in vivo; however, viruses lacking the K7 protein were less virulent than controls in murine intradermal (i.d.) and intranasal (i.n.) infection models and there was an altered acute immune response to infection. In the i.d. model, vΔK7 induced smaller lesions than controls, and after i.n. infection vΔK7 induced a reduced weight loss and signs of illness, and more rapid clearance of virus from infected tissue. Concomitantly, the intrapulmonary innate immune response to infection with vΔK7 showed increased infiltration of NK cells and CD8⁺ T-cells, enhanced MHC class II expression by macrophages, and enhanced cytolysis of target cells by NK cells and VACV-specific CD8⁺ T-cells. Thus protein K7 is a virulence factor that affects the acute immune response to infection.
牛痘病毒（VACV）编码许多拮抗先天免疫系统的蛋白，包括具有 B 细胞淋巴瘤（Bcl）-2 样结构的细胞内蛋白家族。这些 Bcl-2 蛋白之一称为 K7，它与 Toll 样受体衔接蛋白和 DEAD 盒 RNA 解旋酶 DDX3 结合，从而抑制 NF-κB 和干扰素调节因子 3 的激活。然而，K7 对病毒毒力的贡献尚不清楚。在此，构建了一种缺乏 K7R 基因的 VACV（vΔK7），并与包括经蚀斑纯化的野生型（vK7）、重新插入 K7R 基因的回复突变体（vK7-rev）和翻译起始密码子突变以防止 K7 蛋白表达的框移病毒（vK7-fs）在内的对照病毒进行了比较。结果表明，缺失 K7 并不影响病毒在细胞培养或体内的复制；然而，缺乏 K7 蛋白的病毒在小鼠皮内（i.d.）和鼻内（i.n.）感染模型中的毒力低于对照病毒，并且感染后的急性免疫反应发生改变。在 i.d.模型中，vΔK7 引起的病变小于对照病毒，而在 i.n.感染后，vΔK7 引起的体重减轻和疾病迹象减少，以及从感染组织中更快地清除病毒。同时，感染 vΔK7 后肺部的先天免疫反应显示 NK 细胞和 CD8⁺ T 细胞的浸润增加，巨噬细胞的 MHC Ⅱ类表达增强，以及 NK 细胞和 VACV 特异性 CD8⁺ T 细胞对靶细胞的细胞溶解增强。因此，蛋白 K7 是一种影响感染后急性免疫反应的毒力因子。
