Innate Immune Sensing of Rift Valley Fever Virus

描述(申请人提供)：这项试点项目将确定对宿主对A类生物防御病原体裂谷热病毒(RVFV)的反应至关重要的先天免疫途径，方法是利用已建立的人源转化细胞系和特定基因敲除小鼠的小鼠细胞，在体外阐述RVFV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隔8年就会发生一次RVFV的自然流行性流行。这些暴发与受影响牲畜的高死亡率有关，通常与与RVFV相关的人类疾病的同时流行有关。在这种情况下，通过昆虫叮咬或吸入气雾剂向人类传播，这发生在接触受RVFV感染的动物的体液时。根据最近在肯尼亚所做的工作，我们已经确定，无论是在流行期间还是在流行间歇期，RVFV向人类传播的程度都比之前怀疑的要大得多，在受威胁的人类社区中，RVFV终身感染的风险高达25%。对RVFV的先天免疫还没有广泛的特征。在RVFV感染的动物模型中，已发现对I型干扰素(干扰素)早期反应具有很强的保护作用。此外，在人类感染中，干扰素反应的延迟与RVFV引起的更严重的临床疾病有关。Toll样受体(Toll-like Receptor，TLRs)是一类膜结合、胚系编码的模式识别受体，能够检测病毒颗粒或病毒复制产物，刺激早期的干扰素应答。另一类细胞质分子最近被认为与病毒诱导的干扰素基因调控有关。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)，两个DExD/H box RNA解旋酶含有蛋白相互作用的半胱氨酸酶招募和激活结构域(CARD)，识别特定的病毒产物。我们建议确定与裂谷热病毒的先天反应有关的关键PRR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/或疾病介导性免疫反应的一部分至关重要。具体地说，我们的目标是1)确定TLRs或RNA解旋酶在RVFV复制和天然免疫激活中各自共同的适配器信号中的相对作用；2)确定RVFV诱导的I型干扰素和炎性细胞因子反应中涉及的特定TLRs和/或解旋酶。拟议研究的新结果将用于支持一个更大的、以人口为基础的项目的发展，该项目将提交给NIAID以获得外部资金。公共卫生相关性我们提出了高度相关的研究，以确定参与早期宿主防御裂谷热病毒的先天免疫受体和途径。裂谷热病毒(RVFV)是布尼亚病毒科的一种白喉病毒，被指定为A类生物防御病原体，因为如果故意释放，它将对北美的公共卫生和农业造成严重影响。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隔8年就会发生一次RVFV的自然流行性流行。这些暴发与受影响牲畜的高死亡率有关，通常与与RVFV相关的人类疾病的同时流行有关。根据最近在肯尼亚所做的工作，我们已经确定，无论是在流行期间还是在流行间歇期，RVFV向人类传播的程度都比之前怀疑的要大得多，在受威胁的人类社区中，RVFV终身感染的风险高达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.