Viral-bacterial co-infections of the differentiated airway epithelium by pathogens associated with the bovine respiratory disease complex

呼吸道混合感染在现代集约化农畜生产系统中发挥着重要作用。控制混合感染是一项具有挑战性的任务，因为与单一感染相比，发病机制要复杂得多。虽然多年来人们已经知道这一点，但对联合感染中病原体和宿主之间相互作用的分子机制知之甚少。在动物感染中研究这一点是非常困难的，因此，重要的是开发合适的体外模型，尽可能接近体内的情况。在拟议的项目中，我们将分析牛呼吸道重要病原体对呼吸道上皮细胞的混合感染。所分析的病原体包括两种病毒和三种细菌，它们都被认为与牛呼吸道疾病复合体有关：牛呼吸道合胞病毒(BRSV)、牛副流感病毒3(BPIV3)、多杀性巴氏杆菌、溶血性曼氏杆菌和牛支原体。这个项目是基于我们分析了分化的呼吸道上皮细胞的病毒单一感染的初步工作。使用两种分化的呼吸道上皮细胞培养系统，精密切片肺切片和气液界面培养，我们发现BPIV3感染呼吸道细胞是非常有效的，并且对上皮细胞有不利的影响。相比之下，呼吸道上皮细胞被证明在很大程度上对BRSV感染具有抵抗力。拟议项目的目的是首先分析已经在牛分枝杆菌病例中开始的细菌单一感染。这之后是对联合感染的调查。将讨论以下问题：(I)BPIV3感染的有害影响是否有利于三种细菌中的一种随后感染？(2)细菌感染是否使呼吸道细胞易受BRSV感染？预期的结果将增加我们对猪链球菌如何在牛肺中相互作用以诱发牛呼吸道疾病复合体特有症状的理解。

Co-infections in the respiratory tract play an important role in modern intensive production systems of agricultural animals. Control of co-infections is a challenging task, since pathogenesis is much more complex as compared to mono-infections. Though this has been known for many years, little is known about the molecular mechanisms of interactions between pathogens and the host in co-Infections. It is very difficult to study this in animal infections and, therefore, it is important to develop suitable in vitro models which mimic the in vivo situation as closely as possible. In the proposed project, we will analyze the co-infection of airway epithelial cells by important pathogens of the bovine respiratory tract. The pathogens analyzed comprise two viruses and three bacteria that are all considered to be involved the bovine respiratory disease complex: bovine respiratory synzytial virus (BRSV), bovine parainfluenzavirus 3 (BPIV3), Pasteruella multocida, Mannheimia haemolytica und Mycoplasma bovis. This project is based on preliminary work in which we analyzed the viral mono-infection of differentiated airway epithelial cells. Using two cultural systems for differentiated respiratory epithelial cells, precision-cut lung slices and air-liquid-interface cultures, we found that infection of airway cells by BPIV3 is very efficient and has a detrimental effect on the epithelium. By contrast, cells of the respiratory epithelium turned out to be largely resistant against an infection by BRSV. Aim of the proposed project is first to analyze the bacterial mono-infection which has already been started in the case of M. bovis. This is followed by an inverstigation of the co-infection. The following will be addressed: (i) Does the detrimental effect of the BPIV3 infection favor a subsequent infection by one of the three bacterial agents? (ii) Does the bacterial infection render the airway cells susceptible for a subsequent infection by BRSV? The expected results will increase our understanding how S. suis how important respiratory pathogens interact in the bovine lung to induce the symptoms characteristic for the bovine respiratory disease complex.