Innate Immune Sensing of Rift Valley Fever Virus

描述（由申请人提供）：该试点项目将定义宿主对a类生物防御病原体裂谷热病毒（RVFV）反应的先天免疫途径，通过使用已建立的人源转化细胞系和来自特定基因敲除小鼠的小鼠细胞，在体外阐述裂谷热病毒早期细胞反应的分子成分。在非洲和阿拉伯半岛的半干旱地区，野生动物和家畜之间每8年发生一次裂谷热病毒的自然流行。这些暴发与受感染牲畜的高死亡率有关，并且通常与裂谷热病毒相关的人类疾病同时流行有关。在这种情况下，通过昆虫叮咬或气溶胶吸入向人类传播，这在接触感染裂谷热病毒的动物的体液时发生。根据最近在肯尼亚开展的工作，我们已经确定，在流行期间和流行间期，裂谷热病毒向人类传播的程度比以前怀疑的要大得多，在受威胁的人类社区中，裂谷热病毒感染的终生风险高达25%。对裂谷热病毒的先天免疫尚未得到广泛的描述。在裂谷热病毒感染的动物模型中，已确定早期I型干扰素（IFN）反应具有很强的保护作用。此外，在人感染中，干扰素反应的延迟发作与裂谷热病毒引起的更严重的临床疾病有关。toll样受体（TLRs）是一类膜结合的种系编码模式识别受体（PRRs），能够检测病毒颗粒或病毒复制产物，并刺激早期IFN反应。另一类细胞质分子最近被认为与病毒诱导的IFN基因调控有关。视黄酸诱导基因i （RIG-I）和黑色素瘤分化相关基因5 (Mda-5)/Helicard)，两种DExD/H盒RNA解旋酶含有蛋白相互作用caspase募集和激活结构域（CARD）并识别特定的病毒产物。我们建议确定参与裂谷热病毒先天反应的关键PRRs和信号通路。我们假设RVFV与TLRs和/或RIG-I和Mda-5的相互作用对于诱导I型ifn作为人类感染过程中发生的早期保护性和/或疾病介导免疫反应的一部分至关重要。具体来说，我们的目标是：1)确定TLRs或RNA解旋酶各自共同接头信号在RVFV复制和先天免疫激活中的相对作用；2)确定参与RVFV诱导的I型IFN和炎症细胞因子反应的特定TLRs和/或解旋酶。拟议研究的新结果将用于支持发展一个更大的、以人口为基础的项目，该项目将提交给NIAID以获得校外资金。我们提出了高度相关的研究来确定先天免疫受体和参与早期宿主防御裂谷热病毒的途径。裂谷热病毒（裂谷热病毒）是布尼亚病毒科的一种白蛉病毒，根据其在蓄意释放的情况下预计对北美公共卫生和农业造成的严重影响，被指定为a类生物防御病原体。在非洲和阿拉伯半岛的半干旱地区，野生动物和家畜之间每8年发生一次裂谷热病毒的自然流行。这些暴发与受感染牲畜的高死亡率有关，并且通常与裂谷热病毒相关的人类疾病同时流行有关。根据最近在肯尼亚开展的工作，我们已经确定，在流行期间和流行间期，裂谷热病毒向人类传播的程度比以前怀疑的要大得多，在受威胁的人类社区中，裂谷热病毒感染的终生风险高达25%。

DESCRIPTION (provided by applicant): This pilot project will define the innate immune pathways critical for host response to a Category A biodefense pathogen, Rift Valley Fever Virus (RVFV), by elaborating molecular components of early cellular responses to RVFV in vitro, using established human-derived transformed cell lines and murine cells from specific gene knockout mice. In semi-arid regions of Africa and the Arabian Peninsula, natural epizootics of RVFV occur every ~8 years among wildlife and domestic animals. These outbreaks are associated with high mortality among affected livestock, and are usually associated with simultaneous epidemics of RVFV-associated human disease. In such settings, transmission to humans occurs either by insect bite or aerosol inhalation, which occurs during exposure to body fluids of RVFV-infected animals. Based on recent work in Kenya, we have determined that the extent of RVFV transmission to humans is much greater than previously suspected, both during epidemics and inter-epidemic periods, with up to 25% lifetime risk of RVFV infection in threatened human communities. Innate immunity to RVFV has not been extensively characterized. In animal models of RVFV infection, a strong protective role has been identified for early type I interferon (IFN) responses. In addition, in human infection, a delayed onset of IFN response is associated with the more severe forms of RVFV-induced clinical disease. Toll-like receptors (TLRs) constitute a class of membrane bound, germ-line encoded pattern-recognition receptors (PRRs) capable of detecting viral particles or products of viral replication, and stimulating early IFN responses. Another class of cytoplasmic molecules has recently been implicated in virus-induced IFN gene regulation. Retinoic acid-inducible gene-I (RIG-I) and melanoma differentiation-associated gene 5 (Mda-5)/Helicard), two DExD/H box RNA helicases contain protein interaction caspase recruitment and activation domains (CARD) and recognize specific viral products. We propose to identify critical PRRs and signaling pathways involved in the innate response to Rift Valley Fever virus. We hypothesize that interactions of RVFV with TLRs and/or RIG-I and Mda-5 are critical for the induction of type I IFNs as part of the early protective and/or disease-mediating immune responses that occur during the course of human infection. Specifically our aims are to 1) to define the relative role TLRs or RNA helicase respective common adaptor signaling in RVFV replication and innate immune activation, 2) to define specific TLRs and/or helicases involved in RVFV induced type I IFN and inflammatory cytokine responses. Novel results from the proposed studies will be used to support development of a larger, population-based project to be submitted to NIAID for extramural funding. PUBLIC HEALTH RELEVANCE We proposed highly relevant studies to define the innate immune receptors and pathways involved in early host defense against Rift Valley fever Virus. Rift Valley Fever virus (RVFV), a Phlebovirus in the Bunyaviridae family, is designated a Category A biodefense pathogen based upon its projected severe impact on public health and agriculture in North America in the event of a deliberate release. In semi-arid regions of Africa and the Arabian Peninsula, natural epizootics of RVFV occur every ~8 years among wildlife and domestic animals. These outbreaks are associated with high mortality among affected livestock, and are usually associated with simultaneous epidemics of RVFV-associated human disease. Based on recent work in Kenya, we have determined that the extent of RVFV transmission to humans is much greater than previously suspected, both during epidemics and inter-epidemic periods, with up to 25% lifetime risk of RVFV infection in threatened human communities.