The non-classical major-histocompatibility-complex II protein SLA-DM is crucial for African swine fever virus replication

African swine fever virus (ASFV) is a lethal animal pathogen which enters its host cells through endocytosis. So far, host factors specifically required for ASFV replication have been barely identified. In this study a genome-wide CRISPR/Cas9 knockout screen in porcine cells indicated that the genes RFXANK, RFXAP, SLA-DMA, SLA-DMB, and CIITA are important for productive ASFV infection. The proteins encoded by these genes belong to the major-histocompatibility-complex II (MHC II), or swine-leucocyte-antigen-complex II (SLA II). RFXAP and CIITA are MHC II-specific transcription factors, whereas SLA-DMA/B are subunits of the non-classical MHC II molecule SLA-DM. Targeted knockout of either of these genes led to severe replication defects of different ASFV isolates, reflected by substantially reduced plating efficiency, cell-to-cell spread, and progeny virus titers. For the characterization of the knockouts on a proteome level the protein contents of the knockout cell lines were analyzed by mass spectrometry.

非洲猪瘟病毒（African swine fever virus, ASFV）是一种致命的动物病原体，可通过胞吞作用侵入宿主细胞。迄今为止，针对非洲猪瘟病毒复制所特异性必需的宿主因子仍鲜有被探明。本研究通过在猪源细胞中开展全基因组CRISPR/Cas9基因敲除筛选实验，发现RFXANK、RFXAP、SLA-DMA、SLA-DMB及CIITA基因对于非洲猪瘟病毒的有效感染至关重要。上述基因编码的蛋白均属于主要组织相容性复合体II（major-histocompatibility-complex II, MHC II），即猪白细胞抗原II（swine-leucocyte-antigen-complex II, SLA II）家族成员。其中RFXAP与CIITA为MHC II特异性转录因子，而SLA-DMA/B则是非经典MHC II分子SLA-DM的亚基。靶向敲除上述任一基因均会导致不同非洲猪瘟病毒分离株出现严重的复制缺陷，具体表现为集落形成效率大幅降低、细胞间传播能力受损以及子代病毒滴度显著下降。为在蛋白质组层面表征上述基因敲除细胞系，研究人员通过质谱技术对敲除细胞系的蛋白含量进行了分析检测。