Pandemic Potential of H5N1 Influenza Viruses

描述（由申请人提供）：本研究的长期目标是了解可能导致在人类之间有效传播的高致病性H5N1流感病毒出现的分子机制。最近，已多次记录到这些病毒从禽类直接传播到人类。目前，市面上还没有针对这一亚型的疫苗，最近的研究结果表明，H5N1病毒正变得越来越善于感染人类。拟议的研究建立在研究者对现有H5N1病毒的获取和高效的反向遗传系统的可用性的基础上，该系统允许随意修改流感病毒基因组。目标1旨在确定H5N1禽流感病毒在人类中适应所需的分子特征。人类和禽流感病毒分离物的综合序列分析揭示了禽流感病毒适应人类的候选氨基酸。这些氨基酸对病毒复制能力的重要性将在哺乳动物物种中通过使用反向遗传产生的突变病毒进行测试。目的2调查H5N1病毒和目前在哺乳动物物种（包括小鼠、雪貂和非人灵长类动物）中流行的人类毒株之间重组的毒力和传播力。预计这些研究将为评估这种基因重组的大流行潜力提供必要的信息。目的3评估流感PB2蛋白627位氨基酸对哺乳动物物种适应和传播的作用。有证据表明，位于该位置的赖氨酸可能通过在上呼吸道获得生长优势，从而促进病毒在人类之间的有效传播，从而促进哺乳动物的致病性。目的4确定最近分离的对奥司他韦（流感病毒神经氨酸酶的有效抑制剂）具有耐药性的H5N1病毒的致病潜力。目的5阐明鸭获得高毒力H5N1病毒的分子机制。虽然禽流感病毒通常在鸭中保持无症状，但一些H5N1病毒在2002年获得了杀死鸭的能力。非致病性和致病性鸭病毒分离株之间的重组有望对流感发病的分子机制产生新的见解。总的来说，这些研究将使人们能够更好地防范未来在人类中暴发的高致病性禽流感病毒。

DESCRIPTION (provided by applicant): The long-term goal of this research is to understand the molecular mechanisms that could lead to the emergence of highly pathogenic H5N1 influenza viruses that are efficiently transmitted among humans. Recently, direct avian-to-human transmission of these viruses has been documented multiple times. Currently, no vaccine to this subtype is commercially available and recent findings suggest that H5N1 viruses are becoming more adept at infecting people. The proposed research builds on the investigator's access to current H5N1 viruses and the availability of a highly efficient reverse genetics system that allows the influenza virus genome to be modified at will. Aim 1 seeks to identify the molecular features required for adaptation of avian H5N1 viruses in humans. Comprehensive sequence analyses of human and avian virus isolates revealed candidate amino acids for the adaptation of avian viruses to humans. The importance of these amino acids to the replicative ability of viruses will be tested in mammalian species by using mutant viruses generated with reverse genetics. Aim 2 investigates the virulence and transmissibility of reassortants between H5N1 viruses and currently circulating human strains in mammalian species including mice, ferrets, and nonhuman primates. These studies are expected to provide information essential for assessing the pandemic potential of such reassortants. Aim 3 assesses the role of the amino acid at position 627 of the influenza PB2 protein for adaptation to and spread among mammalian species. Evidence suggests that Lys at this position may promote pathogenicity in mammals, possibly by conferring a growth advantage in the upper respiratory tract, hence facilitating efficient virus spread among humans. Aim 4 determines the pathogenic potential of a recently isolated H5N1 virus resistant to oseltamivir, an effective inhibitor of influenza virus neuraminidase. Aim 5 elucidates the molecular mechanisms for the acquisition of high virulence of H5N1 viruses in ducks. While avian influenza viruses are usually maintained asymptomatically in ducks, some H5N1 viruses acquired the ability to kill ducks in 2002. Reassortants between nonpathogenic and pathogenic duck virus isolates are expected to yield new insights into the molecular mechanisms of influenza pathogenesis. Collectively, these studies will enable better preparedness for future outbreaks of highly pathogenic avian influenza viruses in humans.