除了小牛,没有其他牛冠状病毒(BCoV)感染模型,由于其价值高且操作不便,使得BCoV疫苗的疗效评估和致病机理研究不便。本研究旨在建立小鼠BCoV感染模型。用BCoV感染4周龄雄性BALB/c小鼠,筛选最佳感染条件,包括以下感染途径:灌胃,腹腔注射,和尾静脉注射剂量为1×108TCID50、2×108TCID50和4×108TCID50。利用最佳感染条件,BALB/c小鼠感染BCoV,和他们的体重,血常规,炎症因子,尸检,病毒分布,在感染后1、3、5和7天测量病毒载量。结果表明,BCoVHLJ-325株感染BALB/c小鼠的最佳条件是连续口服灌胃3天,剂量为4×108TCID50。感染后第7天,肺部有明显的广泛巩固和结肠壁变薄。在各种器官中观察到明显的炎症,尤其是在结肠和肺泡中,大量炎症细胞浸润的地方.BCoVAg和核酸在内脏器官中均为阳性。结肠和肺中的病毒载量显著高于其他器官(p<0.001)。BCoV感染的小鼠从第5天开始显示出体重下降的趋势,并且在第6天和第7天与对照组相比存在显着差异(p<0.001)。感染后24h,白细胞和淋巴细胞总数开始减少,明显低于对照组(p<0.001),并逐渐恢复到控制水平。细胞因子TNF-α,IL-1β,IL-6呈增加趋势,第5天和第7天显著高于对照组(p<0.001)。这些结果表明BCoVHLJ-325株可以感染BALB/c小鼠并引起炎症反应和组织损伤。在感染后的第七天,用4×108TCID50的剂量和连续的三次灌胃观察到了最显著的效果。这项研究建立,第一次,BCoV感染的BALB/c小鼠模型,为评价BCoV疫苗的免疫效力和研究其致病机制提供了技术手段。
There are no other bovine coronavirus (BCoV) infection models except calves, which makes efficacy evaluation of vaccines and pathogenic mechanism research of BCoV inconvenient owing to their high value and inconvenient operation. This
study aimed to establish a mouse model of BCoV infection. BCoV was used to infect 4-week-old male BALB/c mice and the optimal infection conditions were screened, including the following infection routes: gavage, intraperitoneal injection, and tail vein injection at doses of 1 × 108 TCID50, 2 × 108 TCID50 and 4 × 108 TCID50. Using the optimal infection conditions, BALB/c mice were infected with BCoV, and their body weight, blood routine, inflammatory factors, autopsy, virus distribution, and viral load were measured at 1, 3, 5, and 7 days after infection. The results showed that the optimal conditions for infecting BALB/c mice with BCoV HLJ-325 strain were continuous oral gavage for 3 days with a dose of 4 × 108 TCID50. On the 7th day after infection, there was significant extensive consolidation of the lungs and thinning of the colon wall. Significant inflammation was observed in various organs, especially in the colon and alveoli, where a large number of inflammatory cells infiltrate. Both BCoV Ag and nucleic acid are positive in visceral organs. The viral load in the colon and lungs was significantly higher than that in the other organs (p < 0.001). BCoV-infected mice showed a decreasing trend in body weight starting from day 5, and there was a significant difference compared to the control group on days 6 and 7 (p < 0.001). The total number of white blood cells and lymphocytes began to decrease and was significantly lower than that in the control group 24 h after infection (p < 0.001), and gradually returned to the control level. The cytokine TNF-α, IL-1β, and IL-6 showed an increasing trend, significantly higher than the control group on day 5 and 7 (p < 0.001). These results indicate that the BCoV HLJ-325 strain can infect BALB/c mice and cause inflammatory reactions and tissue lesions. The most significant effect was observed on the seventh day after infection with a dose of 4 × 108 TCID50 and three consecutive gavages. This
study established, for the first time, a BALB/c mouse model of BCoV infection, providing a technical means for evaluating the immune efficacy of BCoV vaccines and studying their pathogenic mechanisms.