Mechanisms of broadly neutralizing humoral immunity against influenza viruses

描述（由申请人提供）：人用疫苗通常是通过反复试验产生的，对它们提供的保护性免疫所涉及的分子机制知之甚少。这种疫苗开发系统对随时间推移几乎不表现出变异性的病原体非常有效;然而，很明显，需要更复杂的方法来开发针对经历连续结构变化的病原体（如流感病毒）的广泛保护性疫苗。目前的流感病毒疫苗通过引发抗体来提供保护，该抗体通过结合病毒的高度可变区域来阻断病毒进入。为了使基于抗体的疗法和疫苗能够有效对抗广泛的结构多样化的流感病毒，显然必须通过阻断病毒复制的替代途径来获得保护。我们小组的成员和其他人对病毒血凝素（HA）保守茎域的广泛中和单克隆抗体的鉴定是一个突破性的进展，因为这些抗体中的许多能够阻断病毒和内体膜的融合，但结合对结构变化具有相对抗性的表位。我们小组成员的第二个关键发现是低浓度抗茎抗体介导的保护作用依赖于Fc-Fc受体（FcR）相互作用;因此，抗体同种型决定了低浓度抗茎抗体的保护活性。目前的提议是对可用于提供针对流感病毒的广泛保护的分子机制进行多中心研究。 我们的项目包括：1）精确定位介导病毒中和的病毒HA和神经氨酸酶糖蛋白上的表位，并剖析它们实现中和的机制。2)使用嵌合流感病毒蛋白的免疫研究，旨在鉴定能够介导广谱体液免疫的结构元件。3)描述Fc-FcR相互作用在病毒中和中的作用。4)在人类受试者中研究如何在疫苗接种期间引发具有有利Fc结构域的抗体。5)人类B细胞对流感抗原特异性的自然进化研究。6)鉴定引起广谱抗流感体液免疫的流感抗原暴露的特定序列。总的来说，我们的目的是更好地了解针对流感病毒表面蛋白的广泛保护性体液免疫应答的机制，从而为推进新一代广泛保护性流感病毒疫苗和基于抗体的治疗方法创造蓝图。

DESCRIPTION (provided by applicant): Human vaccines have most often been generated by trial and error with little understanding of molecular mechanisms involved in the protective immunity that they provide. This system of vaccine development has been remarkably effective against pathogens that exhibit little variability over time; however, it has become evident that a much more sophisticated approach is required to develop broadly protective vaccines against pathogens that undergo continuous structural change, such as influenza viruses. Current influenza virus vaccines confer protection by eliciting antibodies that block viral entry by bindin regions of the virus that are highly mutable. In order for antibody-based therapies and vaccines to be effective against a breadth of structurally diverse influenza viruses, protection will clearl have to be gained through alternate routes of blocking viral replication. The identification of broadly neutralizing monoclonal antibodies against the conserved stalk domain of the viral hemagglutinin (HA), by members of our group and by others, was a groundbreaking advance, as many of these antibodies are able to block fusion of viral and endosomal membranes, yet bind epitopes that are relatively resistant to structural change. A second critical finding by members of our group was that protection mediated by anti-stalk antibodies at low concentrations is dependent on Fc-Fc Receptor (FcR) interactions; therefore, antibody isotype determines protective activity of anti-stalk antibodies at lower concentrations. The current proposal is for a multi-center investigation into molecular mechanisms that can be harnessed to provide broad-based protection against influenza viruses. Our projects include: 1) Precise mapping of epitopes on the viral HA and neuraminidase glycoproteins that mediate virus neutralization, and dissection of mechanisms by which they achieve neutralization. 2) Immunization studies using chimeric influenza virus proteins designed to identify structural elements able to mediate broad-spectrum humoral immunity. 3) Delineation of the roles of Fc-FcR interactions in viral neutralization. 4) Investigation in human subjects into how to elicit antibodies with favorable Fc domains during vaccination. 5) Studies on the natural evolution of human B cell specificities against influenza antigens. 6) Identification of specific sequences of influenza antigen exposures that elicit broad-spectrum, anti-influenza humoral immunity. Overall, our intention is to better understand the mechanisms of broadly protective humoral immune responses against the influenza virus surface proteins and thereby create a blueprint for advancing a new generation of broadly protective influenza virus vaccines and antibody-based therapeutics.