Molecular mechanisms of immune dysregulation by filoviral interferon

丝状病毒，埃博拉病毒和马尔堡病毒（EBOV和MARV），是引起严重病毒性出血热的新兴负链RNA病毒。这些人畜共患病病原体的毒性和新出现的性质使其成为对人类健康的重大威胁，是生物恐怖主义的潜在因素和NIAID A类优先病原体。目前，没有批准的抗丝状病毒治疗剂可用。丝状病毒出血热的特征是不受控制的全身性病毒复制、过度炎症和凝血、树突状细胞（DC）功能失调和淋巴细胞凋亡。我们先前鉴定和结构表征了丝状病毒干扰素拮抗剂蛋白，包括EBOV和MARV VP 35、EBOV VP 24和MARV VP 40。VP 35抵消干扰素（IFN）-α/β（关键的抗病毒细胞因子）的产生。EBOV VP 24和MARV VP 40阻断IFN-α/β诱导的信号传导。我们假设这些病毒IFN-拮抗剂的功能不仅会抵消IFN-α/β的先天抗病毒作用，而且通过靶向模式识别、干扰素和细胞因子受体下游的信号传导，还能够破坏正常的DC成熟过程并促进失调的DC-T淋巴细胞相互作用。以这种方式，丝状病毒IFN拮抗剂将破坏先天性和适应性抗病毒免疫。基于西奈山伊坎医学院Basler实验室与华盛顿大学Amarasinghe和Gross实验室之间正在进行的合作，我们将描述丝状病毒干扰素拮抗剂免疫破坏的分子机制。利用体外生物化学和结构研究，华盛顿大学的Amarasinghe和Gross实验室将确定丝状病毒干扰素拮抗剂如何与宿主免疫系统信号分子相互作用的结构和生物化学基础，并设计功能丧失突变体。Basler实验室将确定树突状细胞和巨噬细胞中受每种丝状病毒IFN拮抗剂影响的特定信号通路，并使用Amarasinghe和Gross实验室提供的结构和生化数据以及关键信号分子的特异性敲除来确定丝状病毒IFN拮抗剂对巨噬细胞功能和DC细胞成熟的影响。所得数据将产生关于丝状病毒IFN拮抗剂对EBOV和MARV抑制DC功能的贡献（将由项目2测试）、对非人灵长类动物模型中病毒复制的促进和IFN的诱导以及适应性免疫应答的贡献（由项目3解决）的具体假设。

The filoviruses, Ebola and Marburg viruses (EBOV and MARV), are emerging, negative-strand RNA viruses that cause severe viral hemorrhagic fever. The virulence and emerging nature of these zoonotic pathogens makes them a significant threat to human health, potential agents of bioterrorism and NIAID category A priority pathogens. Currently, no approved anti-filovirus therapeutics are available. Filoviral hemorrhagic fever is characterized by uncontrolled, systemic virus replication, excessive inflammation and coagulation, dysregulated dendritic cell (DC) function and lymphocyte apoptosis. We previously identified and structurally characterized filoviral interferon antagonist proteins, including EBOV and MARV VP35, EBOV VP24 and MARV VP40. The VP35s counteract the production of interferon (IFN)-alpha/beta, critical antiviral cytokines. EBOV VP24 and MARV VP40 block the signaling induced by IFN-alpha/beta. We hypothesize that the function of these viral IFN-antagonists will not only counteract the innate antiviral effects of IFN-alpha/beta but, by targeting signaling downstream of pattern recognition, interferon and cytokine receptors, will also be able to disrupt the normal DC maturation process and promote dysregulated DC-T lymphocyte interactions. In this way, the filoviral IFN-antagonists will disrupt both innate and adaptive antiviral immunity. Building on ongoing collaborations between the Basler laboratory at the Icahn School of Medicine at Mt Sinai and the Amarasinghe and Gross laboratories at Washington University, we will characterize the molecular mechanisms of immune disruption by filoviral interferon antagonists. Using in vitro biochemical and structural studies, the Amarasinghe and Gross laboratories at Washington University will define the structural and biochemical basis for how filoviral interferon antagonists interact with host immune system signaling molecules and design loss of function mutants. The Basler laboratory will define the specific signaling pathways affected by each filoviral IFN-antagonist in dendritic cells and macrophages and using the structural and biochemical data provided by Amarasinghe and Gross labs as well as specific knockdown of key signaling molecules will define the impact of filoviral IFN-antagonists on macrophage function and DC cell maturation. The resulting data will generate specific hypotheses regarding the contribution of filoviral IFN-antagonists to EBOV and MARV suppression of DC function (to be tested by Project 2), to promotion of virus replication and induction of IFN and adaptive immune responses in non-human primate models (addressed by Project 3).