Studies on the Epidemiology of H5N1 Influenza Evolution

描述（由申请人提供）：高致病性H5N1禽流感病毒构成使人衰弱的大流行威胁。虽然预防性疫苗正在开发中，但正在进行的病毒进化以逃避免疫反应仍然存在问题。因此，我的长期目标是了解这种病毒在选择性免疫压力下的抗原进化和分子流行病学，并深入了解潜在大流行毒株的起源和出现。核心假设是，病毒逃逸突变体受到与中和抗体的特定相互作用的限制，这些突变体必须沿着明确的、显性的、可复制的进化路线进化，以逃避免疫压力。这一假设部分基于对最近在人群中暴发的H5N1病毒的流行病学分析的观察结果。血凝素（HA）中一些氨基酸的变化与受体结合有关，在人身上比在禽身上更常见，这表明这些病毒在抗原性上是不同的。这种积极的选择可能是由于特定的免疫压力以及病毒对人类宿主的适应过程。我将使用针对HA的人单克隆抗体来检验这一假设，以确定H5N1病毒在选择性免疫压力下的进化途径。此外，我将把流感感染的具体逃逸途径与临床结果联系起来。特别是，我提出以下具体目标：1)表征一组中和和交叉中和抗h5抗体的表位及其作用机制。2)鉴定由这些抗体诱导的病毒逃逸突变体，并根据序列变异模式描述允许的进化路线，通过该路线病毒可以逃避表位特异性抗体中和。3)确定病毒进化途径是否与病毒体外适应度和致病性以及体内病毒感染的临床结果相关。

DESCRIPTION (provided by applicant): Highly pathogenic avian influenza virus H5N1 poses a debilitating pandemic threat. While prophylactic vaccines are being developed, ongoing viral evolution to evade immune responses remains problematic. Therefore, my long-term goals are to understand the antigenic evolution and molecular epidemiology of this virus in the face of selective immune pressure and to gain insights into the genesis and emergence of potentially pandemic strains. The central hypothesis is that viral escape mutants are constrained by specific interactions with neutralizing antibodies, and these mutants must evolve along defined, dominant, and reproducible evolutionary routes to escape from the immune pressure. The hypothesis is based, in part, on observations from epidemiological analysis of H5N1 virus from recent outbreaks in human populations. Some amino acids changes in hemagglutinin (HA) were involved in receptor binding and more frequently observed in human than in avian isolates, indicating that these viruses were antigenically distinct. This positive selection may be due to specific immune pressures as well as the process of viral adaptation to human hosts. I will test the hypothesis using human mAbs against the HA to define the pathways of H5N1 virus evolution under selective immune pressures. Additionally, I will correlate the specific routes of escape with clinical outcomes of influenza infection. In particular, I propose the following specific aims: 1) To characterize the epitopes of a panel of neutralizing and cross-neutralizing anti-H5 antibodies and their mechanisms of action. 2) To identify viral escape mutants induced by these antibodies and delineate the permitted evolutionary routes, as defined by patterns of sequence variations, by which the virus can escape epitope-specific antibody neutralization. 3) To determine if routes of virus evolution can be correlated with viral fitness and pathogenicity in vitro and clinical outcome of viral infection in vivo. RELEVANCE: Preventing human infections with bird flu has become a major public health priority as the virus continues to cause widespread economic and human losses as it spreads. The scientific contributions of this research will add to our understanding of how the virus survives detection and elimination by the immune system and provide strategic approaches to preventing infection or clinical disease progression.