Development of Immunogenicity- and Efficacy-Optimized CMV Vectors for an HIV/AIDS Vaccine

总体方案摘要 十多年前，我们的小组开始开发基于持久性β- 巨细胞病毒（CMV），因为CMV的能力，以引发和无限期地保持高 不同组织中的频率效应分化T细胞反应。使用恒河猴（RM）模型， 我们测试了这样一个概念，即由这种“原位”效应记忆T细胞提供的早期病原体拦截 将导致对免疫逃避病原体如HIV/SIV的上级保护，相对于典型的 传统疫苗方法引起的记忆反应。我们发现，不仅是恒河猴（Rh） CMV适合于“载体化”（例如，我们证明，即使在传播缺陷时， 在天然RhCMV+中产生有效的、持久的、外源性插入特异性效应记忆T细胞应答 RM），而且这些载体引起的SIV特异性应答能够重复地严格地表达， 控制，然后从约54%的接种RM中清除粘膜给药的高致病性SIV。虽然 这种前所未有的“控制和清除”保护与早期感染拦截一致， 保护性免疫反应一直难以捉摸，直到我们发现Rh157.5/Rh157.4基因缺失， 作为我们疫苗骨架的rhCMV载体具有另一个非常不寻常的免疫学特性：所有CD 8+细胞都是CD 8+细胞。 发现由该载体引发的T细胞识别受MHC-II或MHC-E限制的表位， 不是MHC-Ia。我们进一步证明，这种非常规表位靶向被恢复到常规表位靶向。 通过修复Rh157.5/Rh157.4表达的MHC-Ia限制，其不另外影响功能性或 载体诱导的CD 8 + T细胞的表型特征。值得注意的是，修复的RhCMV/SIV载体失败了， 保护免受SIV攻击，强烈表明非常规的CD 8 + T细胞表位识别是 RCMV/SIV载体功效所需的。最近的研究表明，传统与非传统 CD 8 + T细胞启动受多个RhCMV基因调控，其修饰有效地编程 RhCMV载体引发具有不同表位识别模式的CD 8 + T细胞应答。在这个项目中，我们 首先寻求确定非常规CD 8 + T细胞应答产生的机制， 开发RhCMV载体，其主要或专门引发MHC-II与MHC-E限制性CD 8 + T细胞 （项目2-4）。然后，我们将使用这些新的向量来1）识别以下操作所需的响应类型： 疗效，2）确定这种反应聚焦是否改善疗效，以及3）定义定量和/或定量的反应聚焦。 这种保护的质量相关性（项目1）。最后，我们将使用这些RM研究中获得的见解 设计（项目4）、生产和临床试验（项目5）一种扩散剂的安全性和免疫原性- 缺陷的、“应答程序化的”HCMV/HIV载体，其设计用于引发保护性应答类型。如果这 如果这项努力取得成功，其结果将是一种非常有效的艾滋病毒/艾滋病疫苗，单独或与一种 补充性抗体靶向疫苗，可以大大有助于结束艾滋病毒/艾滋病的流行。

Overall Program Summary More than a decade ago our group initiated development of vaccine vectors based on the persistent β- herpesvirus Cytomegalovirus (CMV) because of the ability of CMV to elicit and indefinitely maintain high frequency effector-differentiated T cell responses in diverse tissues. Using the rhesus macaque (RM) model, we tested the concept that the early pathogen intercept afforded by such “in place” effector-memory T cells would result in superior protection against immune evasive pathogens like HIV/SIV, relative to the typical memory responses elicited by conventional vaccine approaches. We found that not only was Rhesus (Rh) CMV amenable to “vectorization” (e.g., we demonstrated that, even when spread-deficient, RhCMV vectors generate potent, durable, exogenous insert-specific effector-memory T cell responses in naturally RhCMV+ RM), but also that the SIV-specific responses elicited by these vectors were reproducibly able to stringently control and then clear mucosally-administered, highly pathogenic SIV from ~54% of vaccinated RM. Although this unprecedented “control and clear” protection was consistent with an early infection intercept, the nature of the protective immune response remained elusive until we discovered that the Rh157.5/Rh157.4 gene-deleted RhCMV vector used as the backbone of our vaccine had another very unusual immunologic property: all CD8+ T cell elicited by this vector were found to recognize epitopes that were restricted by either MHC-II or MHC-E, not MHC-Ia. We further demonstrated that this unconventional epitope targeting was reverted to conventional MHC-Ia restriction by repair of Rh157.5/Rh157.4 expression, which did not otherwise affect the functional or phenotypic characteristics of vector-elicited CD8+ T cells. Remarkably, the repaired RhCMV/SIV vectors failed to protect against SIV challenge, strongly suggesting that unconventional CD8+ T cell epitope recognition is required for RCMV/SIV vector efficacy. Recent work has demonstrated that conventional vs. unconventional CD8+ T cell priming is regulated by multiple RhCMV genes, the modification of which effectively programs RhCMV vectors to elicit CD8+ T cell responses with distinct epitope recognition patterns. In this program, we first seek to determine the mechanisms responsible for unconventional CD8+ T cell response generation, and develop RhCMV vectors that predominantly or exclusively elicit MHC-II vs. MHC-E-restricted CD8+ T cell responses (Projects 2-4). We will then use these new vectors to 1) identify the response type(s) needed for efficacy, 2) determine whether such response focusing improves efficacy, and 3) define quantitative and/or qualitative correlates of this protection (Project 1). Finally, we will use the insight gained in these RM studies to design (Project 4), manufacture and clinically test (Project 5) the safety and immunogenicity of a spread- deficient, “response-programmed” HCMV/HIV vector designed to elicit the protective response type. If this effort is successful, the result would be a highly effective HIV/AIDS vaccine that alone, or combined with a complementary antibody-targeted vaccine, could substantially contribute to ending the HIV/AIDS epidemic.