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Analysis of the neutralizing antibody response following flavivirus infection

黄病毒感染后中和抗体反应的分析

基本信息

批准号：
9354825
负责人：
Theodore Pierson
金额：
$ 5.3万
依托单位：
NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
依托单位国家：
美国
项目类别：
财政年份：
资助国家：
美国
起止时间：
至
项目状态：
未结题

项目摘要

Dengue virus (DENV) is a mosquito-borne member of the Flavivirus genus that has a global impact on public heath due to its widespread distribution and the ability to cause severe disease in humans. Each year, an estimated 390 million individuals are infected by DENV, with clinical manifestations ranging from a self-limiting acute febrile illness (dengue fever) to a potentially fatal syndrome characterized by plasma leakage and shock (dengue hemorrhagic fever; DHF). Four related serotypes of DENV circulate in nature, each capable of causing the full spectrum of DENV-related disease. Prospective clinical studies clearly demonstrate that sequential infection with two DENV serotypes is associated with a more severe disease course. The number of DHF cases reported has increased dramatically during the past twenty years, and now exceeds 250,000 cases annually. Thus, there is an urgent need for the development of a safe and effective vaccine for all four serotypes of DENV. Neutralizing antibodies play an important role in protection against flavivirus infection. Antibodies have been mapped to all three structural domains of the E protein (DI-DIII) that exhibit varying degrees of neutralization potency and confer protection by multiple effector mechanisms. Eliciting neutralizing antibody is a major goal of vaccine development. Complicating these efforts is a requirement for vaccines to simultaneously elicit protection against four different viruses that while antigenically related, share only some of the antibody-binding determinants thought to contribute to virus neutralization. Thus, antibodies raised against one serotype of DENV may react with virions of another serotype, but often with reduced affinity and functional potency. Paradoxically, antibodies may also play a role in enhancing virus infection and exacerbating disease. Antibody-dependent enhancement of infection (ADE) describes a dramatic increase in infection of Fc-receptor-bearing cells in the presence of sub-neutralizing concentrations of antibody or immune sera. The most direct link between ADE and the clinical outcome of DENV infection comes from investigations of the unusually large number of severe DENV cases following primary infection observed in infants during the first year of life. In a broader context, antibodies elicited by primary infection with one serotype of DENV may bind related viruses introduced during secondary infection with reduced avidity, resulting in engagement of the virion with a stoichiometry that does not permit virus neutralization but can support ADE. The development of an immune response that elicits protective levels of neutralizing antibodies against all four serotypes of virus present in the vaccine is a key factor for reducing the risk of ADE. The development of a protective tetravalent response is complicated by the possibility that all four components of a live attenuated tetravalent vaccine may not be equally immunogenic in the vaccinee. Interference and uneven levels of infectivity among DENV strains in this context has been reported. Understanding the immunogenicity of each component of a tetravalent vaccine is an important aspect of vaccine development and identifying appropriate correlates of protection, particularly because it is presently unclear how many serotype-specific responses will be required for protection from all four serotypes of DENV. However, dissecting the specific contribution of each element of a tetravalent vaccine is technically challenging due to the presence of antibodies that bind cross-reactive determinants shared by different components of the vaccine. A detailed map of the functionally important type-specific and group-reactive epitopes on the E protein is not presently available. Improved methodology that distinguishes and quantifies the functional contribution of each component of a tetravalent vaccine would allow for improvements in estimates of vaccine immunogenicity, a more precise correlate of protection, and a powerful investigational tool to study vaccine success and failure.

登革病毒（DENV）是黄病毒属的一种蚊媒成员，由于其广泛分布和在人类中引起严重疾病的能力，对公共卫生具有全球影响。每年，估计有3.9亿人感染DENV，临床表现从自限性急性发热性疾病（登革热）到以血浆渗漏和休克为特征的潜在致命综合征（登革出血热; DHF）。DENV的四种相关血清型在自然界中传播，每种血清型都能够引起DENV相关疾病的全谱。前瞻性临床研究清楚地表明，两种DENV血清型的连续感染与更严重的病程相关。在过去的二十年中，登革出血热病例报告的数量急剧增加，现在每年超过25万例。因此，迫切需要开发针对DENV的所有四种血清型的安全有效的疫苗。中和抗体在抵抗黄病毒感染中起重要作用。抗体已被映射到E蛋白的所有三个结构域（DI-DIII），这些结构域表现出不同程度的中和效力，并通过多种效应器机制提供保护。产生中和抗体是疫苗开发的主要目标。使这些努力复杂化的是要求疫苗同时引起针对四种不同病毒的保护，这四种不同病毒虽然抗原相关，但仅共享被认为有助于病毒中和的一些抗体结合决定簇。因此，针对DENV的一种血清型产生的抗体可以与另一种血清型的病毒体反应，但通常具有降低的亲和力和功能效力。巧合的是，抗体也可能在增强病毒感染和加重疾病中发挥作用。抗体依赖性感染增强（ADE）描述了在亚中和浓度的抗体或免疫血清存在下携带Fc受体的细胞的感染的显著增加。ADE与DENV感染的临床结局之间最直接的联系来自于对出生后第一年内在婴儿中观察到的原发性感染后异常大量的重度DENV病例的研究。在更广泛的背景下，由一种血清型的DENV的初次感染引起的抗体可以结合在二次感染期间引入的相关病毒，其亲和力降低，导致病毒粒子以不允许病毒中和但可以支持ADE的化学计量接合。产生免疫应答，提高疫苗中存在的所有四种血清型病毒的中和抗体的保护水平，是降低ADE风险的关键因素。四价减毒活疫苗的所有四种组分在接种者中的免疫原性可能不相等，这使得四价保护性应答的发展复杂化。在此背景下，已报道了DENV毒株之间的干扰和不均匀的感染性水平。理解四价疫苗的每种组分的免疫原性是疫苗开发和鉴定适当的保护相关性的重要方面，特别是因为目前还不清楚保护所有四种DENV血清型需要多少种DENV特异性应答。然而，由于存在结合疫苗的不同组分所共有的交叉反应性决定簇的抗体，剖析四价疫苗的每个元件的特定贡献在技术上具有挑战性。目前还没有E蛋白上功能重要的类型特异性和组反应性表位的详细图谱。改进的方法，区分和量化四价疫苗的每种组分的功能贡献，将允许改进疫苗免疫原性的估计，更精确的保护相关性，以及研究疫苗成功和失败的强大的研究工具。