Zhang Hao, Shi Hongyan, Wei Yanwu, Shi Da, Cao Mengxiang, Liu Jianbo, Liu Jianhang, Li Liang, Liu Changming, Feng Li, Huang Liping
Division of Swine Digestive System Infectious Diseases, State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China.
Front Microbiol. 2023 Mar 30;14:1162104. doi: 10.3389/fmicb.2023.1162104. eCollection 2023.
A study in 2006 showed that the clinical course of PEDV disease was markedly aggravated by transplacental infection of PCV2. Therefore, we investigated whether the small intestine supports PCV2 replication and the effect of PCV2 infection on PEDV replication in epithelial cells .
To confirm the intestinal tropism of PCV2, the viral loads in the small-intestinal tissues after PCV2 infection were determined with virus titration, and the viral titers in the infected pig jejunum, ileum, ileocecal valve, and colon were 10, 10, 10, and 10 TCID/g, respectively. We then determined the propagation characteristics of PCV2 in ileal epithelial cells (IPI-FX) and jejunal epithelial cells (IPEC-J2) with an immunoperoxidase monolayer assay, virus titration, and an immunofluorescence assay. Both IPI-FX and IPEC-J2 cells supported the replication of PCV2, with titers of 10 and 10 TCID/ml, respectively. We established an infection model of PCV2 and PEDV in IPI-FX cells and found that PEDV and PCV2 infected the cells individually and together. The effects of PCV2 infection on PEDV replication were determined with reverse transcription-quantitative PCR (qPCR), western blotting, and virus titration. When PCV2 infected IPI-FX cells before PEDV, PCV2 significantly inhibited the replication of PEDV in a dose- and time-dependent manner and that the mRNAs of IFN-β, TNF-α, IL1β, and OASL were downregulated (detected with qPCR). Surprisingly, when IPI-FX cells were co-infected with PCV2 and PEDV, PCV2 promoted the replication of PEDV, the expression of the host IFN-β, TNF-α, IL1β, and OASL mRNAs was upregulated.
These findings demonstrate that the co-infection of IPI-FX cells with PCV2 and PEDV represents an excellent model in which to investigate their combined pathogenic mechanisms.
2006年的一项研究表明，猪圆环病毒2型（PCV2）经胎盘感染会显著加重猪流行性腹泻病毒（PEDV）疾病的临床病程。因此，我们研究了小肠是否支持PCV2复制以及PCV2感染对上皮细胞中PEDV复制的影响。
为证实PCV2的肠道嗜性，通过病毒滴定法测定PCV2感染后小肠组织中的病毒载量，感染猪的空肠、回肠、回盲瓣和结肠中的病毒滴度分别为10、10、10和10 TCID/g。然后，我们用免疫过氧化物酶单层测定法、病毒滴定法和免疫荧光测定法确定PCV2在回肠上皮细胞（IPI-FX）和空肠上皮细胞（IPEC-J2）中的增殖特性。IPI-FX和IPEC-J2细胞均支持PCV2复制，滴度分别为10和10 TCID/ml。我们在IPI-FX细胞中建立了PCV2和PEDV的感染模型，发现PEDV和PCV2可单独或共同感染细胞。用逆转录定量PCR（qPCR）、蛋白质印迹法和病毒滴定法确定PCV2感染对PEDV复制的影响。当PCV2在PEDV之前感染IPI-FX细胞时，PCV2以剂量和时间依赖性方式显著抑制PEDV复制，并且干扰素-β（IFN-β）、肿瘤坏死因子-α（TNF-α）、白细胞介素1β（IL1β）和2'-5'-寡腺苷酸合成酶样蛋白（OASL）的mRNA下调（通过qPCR检测）。令人惊讶的是，当IPI-FX细胞同时感染PCV2和PEDV时，PCV2促进PEDV复制，宿主IFN-β、TNF-α、IL1β和OASL mRNA的表达上调。
这些发现表明，IPI-FX细胞同时感染PCV2和PEDV是研究它们联合致病机制的一个极佳模型。
