Enhancing RhCMV/SIV Vector Efficacy

两项非人灵长类动物功效研究令人信服地表明，野生型（wt） CMV/SIV载体可以1)再次感染CMV+恒河猴（RM）， 2)在再次感染期间，引发强效和持久的SIV特异性CD4+和CD8+ T细胞反应，具有很强的“效应记忆”（TEM）偏好，3)在高致病性、CCR5-tropic SIVmac239病毒的有限剂量直肠攻击后，完全保护约50%的接种过疫苗的恒河猴免受SIV进进性感染。在这些RM中表现出的保护在其突发性和程度上与以前的疫苗不同，受保护的RM在初始感染时表现出不同大小的血浆病毒爆发，随后立即控制到无法检测到的水平。保护作用与疫苗期产生的siv特异性CD8+ T细胞的总量相关，并且在绝大多数受保护的RM（16/17）中稳定存在100 - 12个月。这些数据表明了一种与早期控制一致的新型保护模式，可能发生在病毒进入位点和/或病毒复制和扩增的早期位点，并涉及组织驻留CD8+ TEM。值得注意的是，cmv载体、SIV特异性CD8+ T细胞反应的表位靶向不同于传统病毒载体或SIV本身引发的反应，排除了病毒感染细胞内部加工和呈递的典型免疫显性表位。这种针对wt CMV载体引发的CD8+ T细胞反应的差异表位是由于CMV基因抑制I类mhc限制性Ag呈递（US2-11同源物）的活性，因为US2-11缺失的CMV/SIV载体引发CD8+ T细胞反应，包括对传统（“内部加工”）SIV表位的突出反应。在这个项目中，我们寻求1)通过开发优化的（表位“匹配”的）异源引物来提高CMV载体介导的保护效果，以增强CMV/SIV载体；2)确定US2-11缺失的RhCMV/SIV载体是否具有更高的功效，该载体将CMV/SIV载体诱导的CD8+ TEM反应定向到典型的（直接呈现的）免疫优势表位。3)确定复制缺陷和细胞向性修饰的CMV载体（分别在项目1和项目2中开发）的功效，以及4)进一步确定CMV载体所提供的独特保护所引发的免疫反应的免疫学相关性。

Two nonhuman primate efficacy studies have convincingly demonstrated that wildtype (wt) CMV/SIV vectors can 1) re-infect CMV+ rhesus macaques (RM), 2) during re-infection, elicit potent and persistent SIV- specific CD4+ and CD8+ T cell responses with a strong "effector memory" (TEM) bias, and 3) completely protect ~50% of vaccinated RM from progressive SIV infection after limiting dose rectal challenge with the highly pathogenic, CCR5-tropic SIVmac239 virus. The protection manifested in these RM is distinct from previous vaccines in its abruptness and extent, with protected RM exhibiting a viral burst in plasma of varying size upon initial infection, followed by immediate control to undetectable levels. Protection correlates with the extent of total SIV-specific CD8+ T cells generated during the vaccine phase, and is stable in the vast majority of protected RM (16/17) for >12 months. These data indicate a novel pattern of protection consistent with very early control, likely taking place at the site of viral entry and/or early sites of viral replication and amplification, and involving tissue-resident CD8+ TEM. Significantly, the epitope targeting of CMV-vectored, SIV-specific CD8+ T cell responses is distinct from responses elicited by conventional viral vectors or SIV itself, excluding the typical immunodominant epitopes that are internally processed in and presented by virally infected cells. This differential epitope targeting of wt CMV vector-elicited CD8+ T cell responses is due to the activity of CMV genes that inhibit class I MHC-restricted Ag presentation (US2-11 homologues), as US2-11 deletant CMV/SIV vectors elicit CD8+ T cell responses that include prominent responses to the conventional ("internally processed") SIV epitopes. In this project, we seek to 1) improve the efficacy of CMV vector mediated protection with development of an optimized (epitope "matched") heterologous prime for a CMV/SIV vector boost, 2) determine whether US2-11 deletant RhCMV/SIV vectors, which redirect CMV/SIV vector elicited CD8+ TEM responses to typical (directly presented) immunodominant epitopes, have increased efficacy, 3) determine the efficacy of replication-deficient and cell tropism-modified CMV vectors (developed in Projects 1 and 2, respectively), and 4) further define immunologic correlates of the unique protection afforded by CMV-vector elicited immune responses.