H3N2亚型犬流感病毒基因变异对传播特性的影响及作用机制

H3N2 subtype canine influenza virus (CIV) was prevalent in dogs in China. Due to the close contact between dogs and humans, H3N2 CIV is posing a potential threat to human health once it occurred human-adapted mutation. Acquiring efficient transmissibility among humans is an important requirement for an animal influenza virus becomes pandemic. Guinea pigs is a nice model to be used to study the transmission of influenza virus in humans. Previously, we found that the transmissibility among guinea pigs of recent H3N2 CIVs was increased, and some strains were capable of air droplet transmission. However, the molecular mechanism of the transmissibility of CIV is still unclear. In this project, we plan to systematically compare the transmissibility of H3N2 CIVs in guinea pigs, determine the proteins crucial for transmission by studying the receptor specificity, neuraminidase activity, and polymerase activity. We will elucidate the role of the crucial gene segments and amino acid mutation by reverse genetics, and analyze charges and structure of functional domain induced by the amino acid mutation. The outcome generated form this project will elucidate the molecular basis of the enhanced transmissibility of CIV, and provide valuable information for early warning and control of novel influenza virus.

H3N2亚型犬流感病毒（CIV）在我国犬群中广泛流行，鉴于犬与人的亲密接触性，一旦CIV发生适应人的变异，对公共卫生健康可能造成危害。动物流感病毒获得在人群中有效的传播能力是病毒形成大流行的重要因素。豚鼠是用于研究流感病毒在人群中传播能力的理想模型，申请人前期的研究发现，近年来H3N2 CIV在豚鼠模型中的传播能力提高，甚至部分病毒能够通过气溶胶途径传播。然而，导致CIV传播能力改变的分子基础尚不清楚。本项目拟系统研究不同分离时期H3N2 CIV的传播特性，探究具有不同传播特性的CIV在受体结合特性、神经氨酸酶活性、聚合酶活性等蛋白功能的差异，确定导致病毒传播能力改变的关键病毒蛋白；利用反向遗传技术，揭示决定CIV传播性的关键基因片段及氨基酸位点；利用结构生物信息学技术，解析基因变异所引起的电荷变化和功能域结构的改变。从而阐明CIV传播性增强的分子基础，为新型流感病毒的预警和防控提供依据。

H3N2亚型犬流感病毒（CIV）在我国犬群中广泛流行，鉴于犬与人的亲密接触性，一旦CIV发生适应人的变异，对公共卫生健康可能造成危害。在本项目支持下，课题组系统开展了我国H3N2 CIV的流行病学调查，发现2016年之后分离的CIV各基因组片段形成了一个与韩国，美国流行毒株亲缘关系更近的新进化分支，新进化分支不仅具备了新的抗原性，还获得了与哺乳动物适应性相关的位点，表明新分支毒株对公共卫生安全的潜在威胁潜在威胁性；系统评价了代表性H3N2 CIV在豚鼠中的传播性，结果表明有更多新分支毒株的传播能力增强，且多株病毒具备了气溶胶传播特性；我们进一步深入解析了H3N2犬流感病毒在豚鼠中的传播能力提高的分子机制，发现了HA与PB1的变异在增强H3N2 CIV在豚鼠中的传播能力中起关键作用，并且HA-204位，PB1-154、-205、-216位为关键氨基酸位点；揭示了PA-X截短有利于提高CIV在犬群中的复制能力和传播性；在以上研究的基础上，还开展了疫苗应用研究，筛选出具有广谱中和活性的疫苗候选株，研发出H3N2和H3N8亚型犬流感二价灭活苗。上述研究成果有助于系统认识H3N2 CIV的流行性，及其传播的分子机制，并为其防控提供了技术保障。

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