Immune recognition and function of Bovine Viral Diarrhea Virus envelope proteins

牛病毒性腹泻病毒(BVDV)在加拿大牛群中高度流行。BVDV的这种传播继续给奶牛群和肉牛群造成重大经济损失。在受感染的怀孕奶牛中，胎儿在怀孕的前三个月通过胎盘感染病毒。这头小牛将成为持续性感染(PI)，不会对该病毒产生免疫反应。由此产生的牛犊在出生时对BVDV免疫耐受，并将在其一生中排出大量BVDV。这些PI动物被认为是新的BVDV感染和持续病毒传播的主要来源。为了更好地了解这些病毒是如何进化并在宿主体内持续存在的，研究病毒的自然抗原变异性是必不可少的。随着时间的推移，病毒表现出的这些抗原性变化是由宿主和病原体相互作用的方式决定的。我们已经使用这些PI来研究病毒在宿主间和宿主内的变异性，这将被用来建立可以推断BVDV进化的进化模型。BVDV的高突变率对宿主免疫反应和旨在开发疫苗以防止感染这些病原体的研究人员都构成了挑战。 该程序的这一部分专门旨在阐明BVDV的两种最具抗原性的包膜蛋白的性质。在这项研究中，我们将探索两种不同的方法来量化抗原-抗体相互作用。将检查一系列不同的单抗和多克隆抗体以及几种自然产生的BVDV变种(目标I)。我们将更好地了解抗体与特定抗原结合的决定因素，我们可以比较不同菌株的抗原性。为了更准确地识别BVDV包膜蛋白中被免疫系统识别的部分，我们将使用两种不同但互补的策略(目标II)绘制参与免疫识别的氨基酸图谱。这将为我们提供免疫系统识别并可能在未来经历进化变化的部分的概述。本提案的最后一个组成部分(目标III)将研究这些包膜糖蛋白的糖结构(N-糖基化)。这些糖在病毒生命周期中具有非常重要的作用，并可以影响宿主的免疫系统识别病毒的方式。N-糖基化在免疫逃逸中发挥重要作用。通过对这些糖结构施加特定的选择性压力，我们迫使病毒适应。这将揭示病毒修改糖蛋白这些关键成分的选择。目前的研究有望为BVDV与其牛宿主的相互作用提供新的见解，并将产生关于病毒变异性和进化的新信息。所有这些信息将导致一种新的方法来推断病毒的进化和我们如何构建BVDV疫苗。

Bovine Viral Diarrhea Virus (BVDV) is highly prevalent among cattle herds in Canada. This circulation of BVDV continues to cause significant economic losses in both dairy and beef herds. In infected pregnant cows, the fetus contracts the virus transplacentally during the first trimester of gestation. This calf will become persistently infected (PI), and will not mount an immune response against this virus. The resulting calf is BVDV immunotolerant at birth and will shed large quantities of BVDV throughout its life. These PI animals are considered the main source of new BVDV infections and continued virus circulation. To better understand how these viruses evolve and persist in their host it is essential to study the virus natural antigenic variability. These antigenic changes exhibited by the virus over time are determined by the way hosts and pathogens interact. We have used these PIs to study virus inter- and intra-host variability which will be used to establish evolutionary models that can infer BVDV evolution. The high mutation rate of BVDV is posing challenges for both the host immune response and the researcher that aims to develop vaccines to prevent infections with these pathogens. This component of the program specifically aims to elucidate the properties of the two most antigenic envelope proteins of BVDV. In this study we will explore two different ways to quantify the antigen-antibody interaction. A series of different monoclonal and polyclonal antibodies and several naturally occurring BVDV variants will be examined (Objective I). We will better understand the determinants of antibody binding to a specific antigen and we can compare the antigenicity of the various strains. To more precisely identify the parts of the BVDV envelope proteins that are recognized by the immune system, we will map the amino-acids that are involved in immune recognition using two different, but complementary strategies (Objective II). This will provide us with an overview of the parts that are recognized by the immune system and are likely to undergo evolutionary change in the future. The last component of this proposal (Objective III) will study the sugar-structures (N-glycosylation) of these envelope glycoproteins. These sugars have very important roles in the virus lifecycle and can influence the way the immune system of the host will recognize the virus. N-glycosylation can play a significant role in immune-escape. By posing specific selective pressures on these sugar structures we force the virus to adapt. This will reveal the options for the virus to modify these crucial components of the glycoprotein. The current studies are expected to provide novel insights in the way BVDV interacts with its bovine host and will generate new information on virus variability and evolution. All this information will lead to a new way to infer virus evolution and how we construct BVDV vaccines.