Evaluation of Protective CMV Vaccines in Rhesus Macaques

描述（由申请方提供）：35年来，对人巨细胞病毒（HCMV）先天性感染的疫苗的探索仍未得到满足。HCMV自然史的复杂性、免疫保护的不完全定义的相关性以及设计充分效力的临床试验中的财务和后勤因素都导致了许可的HCMV疫苗的缺乏。现在从人和恒河猴（RM）的研究中越来越认识到（1）HCMV和恒河猴CMV（RhCMV）进入细胞（如内皮细胞和上皮细胞）的机制不同于成纤维细胞进入的机制，和（2）血清免疫个体产生针对介导上皮/内皮细胞嗜性的病毒蛋白的中和抗体。对HCMV的研究表明，UL 128、131 A、130蛋白与gH和gL一起形成复合物，该复合物是上皮/内皮细胞通过内吞途径嗜性所必需的，并且这些蛋白中任何一种的缺失极大地限制了HCMV感染至gB介导的进入细胞，如成纤维细胞。来自自然史和组织培养研究证据的优势证据表明，疫苗策略需要阻断内吞（UL 128复合物）和成纤维细胞（gB）进入途径，以建立足够水平的保护性免疫，减少或预防先天性感染。HCMV的数据和我们在从rMVA表达分泌形式的RhCMV UL 128作为单个亚基以及表征UL 128复合物在RhCMV自然史中的作用方面的进展导致了这样的假设，即靶向UL 128复合物的疫苗策略将显示对体液中病毒脱落的增强限制。基于这一假设，用UL 128复合物接种RhCMV-naove RM将显著降低全身感染性病毒的频率和滴度，导致脱落病毒水平降低。该假设将通过以下目的在我们的HCMV持久性和发病机制的灵长类动物模型中进行严格测试。(1)UL 128复合物的质粒表达和MVA载体的构建和表征。(2)用目标1中构建的表达载体优化猕猴中的疫苗接种，以及RhCMV感染的猕猴中对UL 128复合物的外周和粘膜抗体应答的表征。(3)通过Aim 2的优化初免/加强方案免疫RhCMV阴性RM，然后通过皮下或粘膜途径进行RhCMV攻毒，能够进入成纤维细胞和内吞细胞。

DESCRIPTION (provided by applicant): The 35 year quest for a vaccine that confers protective efficacy against congenital infection with human cytomegalovirus (HCMV) remains unmet. Complexities in HCMV natural history, incompletely defined correlates of immune protection and financial and logistical factors in designing sufficiently powered clinical trials all contribute to the absence of a licensed HCMV vaccine(s). There is now increased recognition from studies in both humans and rhesus macaques (RM) that (1) the mechanism of HCMV and rhesus CMV (RhCMV) entry into cells, such as endothelial and epithelial cells, is distinct from the mechanism of fibroblast entry, and (2) seroimmune individuals develop neutralizing antibodies against the viral proteins mediating epithelial/endothelial cell tropism. Studies with HCMV show that the UL128, 131A, 130 proteins together form a complex with gH and gL that is essential for epithelial/endothelial cell tropism via an endocytic pathway, and the absence of any one of these proteins greatly restricts HCMV infection to gB-mediated entry into cells, such as fibroblasts. The preponderance of evidence from natural history and tissue culture studies evidence indicates that vaccine strategies will need to block both the endocytic (UL128 complex) and fibroblast (gB) entry pathways to establish a sufficient level of protective immunity to reduce or prevent congenital infection. The data with HCMV and our progress in both expressing a secreted form of RhCMV UL128 from rMVA as a single subunit and characterizing the role of the UL128 complex in RhCMV natural history lead to the hypothesis that vaccine strategies targeting the UL128 complex will show enhanced restriction of virus shedding in bodily fluids. Based on this hypothesis, vaccination of RhCMV-naove RM with the UL128 complex will have a significantly reduced frequency and titer of systemic infectious virus, resulting in reduced levels of shed virus. This hypothesis will be rigorously tested in our primate model of HCMV persistence and pathogenesis through the following Aims. (1) Construction and characterization of plasmid expression and MVA vectors for the UL128 complex. (2) Optimization of vaccination in macaques with expression vectors constructed in Aim 1, and characterization of peripheral and mucosal antibody responses to the UL128 complex in RhCMV-infected macaques. (3) Immunization of RhCMV-negative RM by the optimized prime/boost regimen from Aim 2 followed by either a subcutaneous or mucosal route of RhCMV challenge capable of both fibroblast and endocytic entry.