ABSTRACT

Bovine viral diarrhea virus (BVDV) is affecting cattle populations all over the world causing acute disease, immunosuppressive effects, respiratory diseases, gastrointestinal, and reproductive failure in cattle. The virus is taken up via the oronasal route and infection of epithelial and immune cells contributes to the dissemination of the virus throughout the body. However, it is not known how the virus gets across the barrier of epithelial cells encountered in the airways. Here, we analyzed the infection of polarized primary bovine airway epithelial cells (BAEC). Infection of BAEC by a non-cytopathogenic BVDV was possible via both the apical and the basolateral plasma membrane, but the infection was most efficient when the virus was applied to the basolateral plasma membrane. Irrespective of the site of infection, BVDV was efficiently released to the apical site, while only minor amounts of virus were detected in the basal medium. This indicates that the respiratory epithelium can release large amounts of BVDV to the environment and susceptible animals via respiratory fluids and aerosols, but BVDV cannot cross the airway epithelial cells to infect subepithelial cells and establish systemic infection. Further experiments showed that the receptor, bovine CD46, for BVDV is expressed predominantly on the apical membrane domain of the polarized epithelial cells. In a CD46 blocking experiment, the addition of an antibody directed against CD46 almost completely inhibited apical infection, whereas basolateral infection was not affected. While CD46 serves as a receptor for apical infection of BAEC by BVDV, the receptor for basolateral infection remains to be elucidated.

摘要

牛病毒性腹泻病毒 (BVDV) 正在影响世界各地的牛群，导致牛的急性疾病、免疫抑制作用、呼吸系统疾病、胃肠道和生殖功能衰竭。病毒通过口鼻途径吸收，上皮细胞和免疫细胞的感染有助于病毒在全身传播。然而，尚不清楚病毒如何穿过气道中遇到的上皮细胞屏障。在这里，我们分析了极化原代牛气道上皮细胞 (BAEC) 的感染。非致细胞性 BVDV 感染 BAEC 可能通过顶端和基底外侧质膜，但当病毒应用于基底外侧质膜时，感染最有效。无论感染部位如何，BVDV 被有效地释放到顶端部位，而在基础培养基中仅检测到少量病毒。这说明呼吸道上皮细胞可以通过呼吸道液和气溶胶向环境和易感动物释放大量BVDV，但BVDV不能穿过气道上皮细胞感染上皮下细胞并建立全身感染。进一步的实验表明，BVDV 的受体牛 CD46 主要在极化上皮细胞的顶端膜结构域上表达。在 CD46 阻断实验中，添加针对 CD46 的抗体几乎完全抑制了顶端感染，而基底外侧感染不受影响。CD46 作为 BVDV 感染 BAEC 的受体，