Ability of CMV Vaccines to Induce Antibodies that Block Endocytic Entry

描述（由申请人提供）：人类巨细胞病毒（CMV）是美国出生缺陷的主要传染性原因。每年在怀孕期间，巨细胞病毒由母体传播给胎儿导致约40,000名巨细胞病毒感染婴儿的出生。虽然大多数感染没有明显的不良影响，但约8000人在出生时表现出严重的并发症，约400人在出生后的第一周内死亡。在那些出生时看起来正常的人中，约8000人可能在童年后期发展为进行性和永久性听力丧失。减毒活疫苗和亚单位巨细胞病毒疫苗正在开发中。在这两种情况下，糖蛋白B （gB）的中和抗体都被强调，因为这种蛋白质是病毒附着和进入的关键角色。然而，过去的研究已经测量了抗血清阻断巨细胞病毒进入成纤维细胞的能力。最近发现巨细胞病毒可以通过“内吞”途径进入并感染内皮细胞、上皮细胞和树突状细胞，这与用于感染成纤维细胞的途径截然不同。这一途径在体内可能比成纤维细胞进入更相关。我们假设病毒进入上皮细胞和内皮细胞可能被特异性靶向介导内吞进入的病毒蛋白的抗体阻断。此外，现有的减毒活疫苗策略可能缺乏效力，因为它们不能诱导针对这些内吞进入表位的特异性中和抗体。我们的目标是通过(1)确定疫苗接种和自然感染诱导特异性靶向内吞进入的中和抗体的程度，促进有效疫苗的开发，以预防巨细胞病毒相关的出生缺陷；(2)克隆Townelong病毒，确定其遗传组成，并表征其细胞趋向性的遗传和机制基础。Townelong病毒是汤恩减毒活疫苗的主要成分。拟议研究的结果将指导新疫苗的设计或对现有疫苗战略提出修改建议，这些战略有可能显著提高疫苗效力。项目简介：人类巨细胞病毒（CMV）是美国出生缺陷的主要感染性原因。为了促进有效的巨细胞病毒疫苗的开发，我们建议评估抗体对最近发现的特异性参与巨细胞病毒进入内皮细胞和上皮细胞的蛋白的重要性，并确定现有候选疫苗能够诱导此类抗体并阻止上皮/内皮细胞进入的程度。拟议研究的结果可能揭示出在设计新疫苗时可以解决的重要缺陷，或建议对现有疫苗策略进行修改，以改善针对这一进入途径的抗体的诱导。

DESCRIPTION (provided by applicant): Human cytomegalovirus (CMV) is the major infectious cause of birth defects in the United States. Each year transmission of CMV from mother-to-fetus during pregnancy results in the birth of ~40,000 CMV-infected babies. While most suffer no overt ill effects from infection, ~8000 exhibit severe complications at birth and ~400 die within the first week of life. Of those that appear normal at birth another ~8000 may develop progressive and permanent hearing loss later in childhood. Both live attenuated and subunit CMV vaccines are under development. In both cases neutralizing antibodies to glycoprotein B (gB) have been emphasized as this protein is a key player in viral attachment and entry. However, past studies have measured the ability of antisera to block entry of CMV into fibroblast cells. Very recently it has been discovered that CMV can enter and infect endothelial, epithelial, and dendritic cells by an "endocytic" pathway that is quite distinct from the pathway used to infect fibroblasts. This pathway may be far more relevant in vivo than fibroblast entry. We hypothesize that viral entry into epithelial and endothelial cells may be blocked by antibodies specifically targeting viral proteins that mediate endocytic entry. Moreover, existing live attenuated vaccine strategies may lack efficacy because they fail to induce neutralizing antibodies specific for these endocytic-entry epitopes. Our objective is to promote development of an effective vaccine to prevent CMV-associated birth defects by (1) determining the extent to which neutralizing antibodies specifically targeting endocytic entry are induced by vaccination and natural infection; and (2) cloning the Townelong virus, which comprises a major component of the live attenuated Towne vaccine, defining its genetic composition, and characterizing the genetic and mechanistic basis of its cellular tropisms. The results of the proposed studies will guide the design of new vaccines or suggest modifications to existing vaccine strategies that have the potential to significantly improve vaccine efficacy. Project Narrative: Human cytomegalovirus (CMV) is the major infectious cause of birth defects in the United States. To promote development of an effective CMV vaccine, we propose to evaluate the importance of antibodies to recently identified proteins that are specifically involved in CMV entry into endothelial and epithelial cells and to determine the extent to which existing candidate vaccines are able to induce such antibodies and block epithelial/endothelial cell entry. The results of the proposed studies may reveal important shortcomings that could be addressed in the design of new vaccines or suggest modifications to existing vaccine strategies that will improve induction of antibodies targeting this entry pathway.