Impact of BHV-1 tegument proteins on the innate response to infection and virion morphogenesis.

牛疱疹病毒-1 （BoHV-1）对生长、牛奶生产和国际牲畜贸易产生严重影响，因此对世界范围内的养牛业造成重大经济损失。在北美，BoHV-1是牛呼吸道疾病的一部分，每年使养牛业损失10亿美元。此外，BoHV-1是水牛中出现的一种新病毒。疱疹病毒由四个同心的区室组成：核蛋白核、衣壳、被皮和包膜。被膜蛋白首先与细胞内环境相互作用，并在后期形成新的病毒粒子的被膜。一些疱疹病毒被膜蛋白具有重要的功能，例如调控转录和病毒形态发生。BoHV-1被膜形成的机制、部位及其蛋白组分的功能在很大程度上是未知的。***本项目的总体目标是对BoHV-1的被膜蛋白进行功能表征。短期目标是表征被膜蛋白VP8在宿主对BoHV-1感染的反应、病毒组装和适应性中的作用。感染BoHV-1的牛细胞或小牛导致强烈的内在宿主反应。这表明病毒需要在感染早期抵消这种反应。VP8是最丰富的病毒蛋白，在感染后2小时的组织培养中检测到，是牛感染所必需的。我们假设并且已经有证据表明VP8在克服宿主早期内在防御中起重要作用。我们将进一步阐明导致这种现象的VP8的机制和关键结构域。其次，由于VP8缺失突变病毒的病毒粒子形态和组成发生了改变，我们假设VP8在病毒形态发生中发挥了作用。为了研究这一点，我们将确定BoHV-1被皮形成和组装所需的vp8蛋白相互作用网络。长期目标是表征其他BoHV-1被膜蛋白。为了获得这些研究的基础，我们将定义BoHV-1病毒粒子在不同成熟阶段的组成。这将导致鉴定其他潜在重要的被膜蛋白，在BoHV-1发病机制和形态发生的背景下进一步研究。***该项目的研究结果预计将对基于特定毒力因子的缺失或修饰的BoHV-1减毒疫苗的合理设计产生重大影响。此外，可以开发靶向被膜蛋白并中断感染或病毒组装起始的治疗方法。随着牛作为新疫苗或疗法体内试验的天然宿主的可用性，这将加速许可，这项工作将很快使加拿大和全世界的畜牧业受益。*** *** **

Bovine herpesvirus-1 (BoHV-1) has a severe impact on growth, milk production, and international livestock trade, thus being responsible for major economic damage to the cattle industry worldwide. In North America BoHV-1 is part of the bovine respiratory disease complex, which costs the cattle industry >1 billion dollars each year. In addition, BoHV-1 is an emerging virus in buffalo. Herpesviruses are composed of four concentric compartments, the nucleoprotein core, capsid, tegument and envelope. Tegument proteins are the first to interact with the intracellular environment and at a later stage associate to create the tegument of new virions. Some herpesvirus tegument proteins have important functions, for instance in regulation of transcription and in virus morphogenesis. The mechanism and site of BoHV-1 tegument formation, and the functions of its protein components are largely unknown.***The overall goal of this program is to perform a functional characterization of the tegument proteins of BoHV-1. The short-term objective is to characterize the role of tegument protein VP8 in the host response to BoHV-1 infection, virus assembly and fitness. Infection of bovine cells or calves with BoHV-1 leads to a strong intrinsic host response. This suggests that the virus needs to counteract this response early during infection. VP8 is the most abundant viral protein, is detected in tissue culture at 2 h post-infection before de novo synthesis and is essential for infection of cattle. We hypothesize and already have evidence that VP8 plays an important role in overcoming early intrinsic defences of the host. We will further elucidate the mechanism and the critical domains of VP8 that are responsible for this phenomenon. Secondly, as the virion morphology and composition is altered in a VP8 deletion mutant virus, we hypothesize VP8 to play a role in virus morphogenesis. To investigate this, we will identify the VP8-protein interaction networks required for tegument formation and assembly of BoHV-1. The long-term objective is to characterize additional BoHV-1 tegument proteins. To obtain a basis for these studies, we will define the composition of BoHV-1 virions at different stages of maturation. This will lead to the identification of additional potentially important tegument proteins, to be further studied in context of BoHV-1 pathogenesis and morphogenesis.***The results of this program are expected to have a significant impact on the rational design of attenuated BoHV-1 vaccines based on deletion or modification of specific virulence factors. Furthermore, therapeutics that target tegument proteins and interrupt initiation of infection or virus assembly may be developed. With the availability of cattle as the natural host for in vivo testing of new vaccines or therapeutics, which will expedite licensing, this work will quickly be of benefit to the livestock industry in Canada and worldwide. *** *** **