Immunosuppresion by Measles & Canine Distemper Viruses

描述（由申请人提供）：麻疹是一种发现病毒诱导免疫抑制现象的疾病：1908年，von Pirquet观察到结核杆菌素皮肤试验反应在急性麻疹过程中短暂下降。麻疹（MV）、犬瘟热（CDV）和牛瘟等麻疹病毒具有免疫抑制作用。这种现象背后的机制是复杂的，但病毒受体的相互作用可能起着核心作用：野生型MV、CDV和牛瘟病毒株优先使用免疫细胞特异性蛋白SLAM（分别为人、犬或牛）作为受体。此外，MV疫苗株Edmonston也通过普遍存在的补体激活调节剂CD46优先进入细胞，CD46相互作用改变了对MV的免疫反应。此外，由MV非结构蛋白V和C引发的进入后宿主控制逃避机制干扰STAT蛋白磷酸化和干扰素激活。我们将验证两个假设：第一，slam依赖性进入对麻疹病毒的免疫抑制至关重要。第二，V和C蛋白有利于病毒在免疫细胞和全身的传播。将使用两种动物模型：用于麻疹的猕猴和用于犬瘟热的雪貂。我们已经生产了选择性受体盲重组mv和cdv。我们正在构建野生型衍生的mv和cdv，其中V或C或这两种蛋白的表达被沉默或增强。猕猴或雪貂将被鼻内感染，并将确定在PBMC、淋巴和非淋巴器官中支持MV和CDV传播的细胞类型。毒力和免疫抑制将根据分级参数进行表征，包括疾病体征、白细胞数量、病毒血症强度和持续时间、体外淋巴细胞增殖水平、中和抗体升数和细胞因子谱。我们预测在受体识别缺陷病毒感染或进入后水平后这些参数的差异变化。结果将在这些预测结果的背景下进行解释。在疾病晚期复制的病毒中，将根据功能测定、测序和传染性cdna的反向转移来寻找恢复毒力的候选突变。这些实验将确定在两个生物学相关的动物系统中，通过特定受体进入细胞和进入后逃避宿主控制机制对麻疹病毒诱导的免疫抑制的相对重要性。

DESCRIPTION (provided by applicant): Measles is the disease with which the phenomenon of virus-induced immunosuppression was discovered: in 1908 von Pirquet observed that the tuberculin skin test response was transiently depressed during the course of acute measles. Morbilliviruses including measles (MV), canine distemper (CDV) and rinderpest are immunosuppressive. The mechanisms underlying this phenomenon are complex, but viral receptor interactions may play a central role: wild-type MV, CDV and rinderpest virus strains preferentially use the immune cell-specific protein SLAM (human, canine or bovine, respectively) as a receptor. In addition, the MV vaccine strain Edmonston enters cells preferentially also through the ubiquitous regulator of complement activation, CD46, and CD46 interactions modify the immune response to MV. Moreover, post-entry host control evasion mechanisms elicited by the MV non-structural proteins V and C interfere with STAT protein phosphorylation and interferon activation. We will test two hypotheses: first, that SLAM-dependant entry is of central importance for immunosuppression by morbilliviruses. Second, that the V and C proteins favor virus dissemination in immune cells and systemically. Two animal models will be used: macaques for measles and ferrets for canine distemper. We have produced selectively receptor-blind recombinant MVs and CDVs. We are constructing wild type-derived MVs and CDVs in which the expression of V or C, or of both proteins, is silenced or enhanced. Macaques or ferrets will be infected intranasally and the cell types supporting MV and CDV dissemination in PBMC, and in lymphatic and non-lymphatic organs, will be identified. Virulence and immunosuppression will be characterized based on graded parameters including disease signs, leukocyte number, strength and duration of viremia, in vitro lymphocyte proliferation levels, neutralizing antibody liters, and cytokine profile. We predict differential changes in these parameters following infections with viruses defective at the receptor recognition or post-entry level. Results will be interpreted in the context of these predicted outcomes. Candidate mutations for reversion to virulence will be sought in viruses replicating at late disease stages based on functional assays, sequencing, and back-transfer in infectious cDNAs. These experiments will define the relative importance of cell entry through specific receptors and of post-entry host control evasion mechanisms for morbillivirus-induced immunosuppression in two biologically relevant animal systems.