Enhancing RhCMV/SIV Vector Efficacy

两项非人灵长类动物功效研究已经令人信服地证明野生型（wt）CMV/SIV载体可以1）再感染CMV+恒河猴（RM），2）在再感染期间，引发具有强“效应记忆”（TEM）偏倚的有效且持久的SIV特异性CD 4+和CD 8 + T细胞应答，和3）在用高致病性嗜CCR 5 SIVmac 239病毒进行有限剂量直肠攻击后，完全保护约50%的接种RM免于进行性SIV感染。这些RM中表现出的保护作用在其突然性和程度上与之前的疫苗不同，受保护的RM在初始感染后在血浆中表现出不同大小的病毒爆发，然后立即控制到无法检测的水平。保护作用与疫苗阶段产生的总SIV特异性CD 8 + T细胞的程度相关，并且在绝大多数受保护的RM（16/17）中稳定>12个月。这些数据表明一种新的保护模式与非常早期的控制一致，可能发生在病毒进入的位点和/或病毒复制和扩增的早期位点，并涉及组织驻留的CD 8 + TEM。值得注意的是，CMV载体的SIV特异性CD 8 + T细胞应答的表位靶向不同于由常规病毒载体或SIV本身引起的应答，排除了在病毒感染细胞中内部加工并由病毒感染细胞呈递的典型免疫显性表位。野生型CMV载体引发的CD 8 + T细胞应答的这种差异表位靶向是由于抑制I类MHC限制性Ag呈递的CMV基因（US 2 -11同源物）的活性，因为US 2 -11缺失CMV/SIV载体引发包括对常规（“内部加工的”）SIV表位的显著应答的CD 8 + T细胞应答。在这个项目中，我们寻求1）通过开发优化的CMV载体介导的保护作用来提高CMV载体介导的保护作用的功效。2）确定重定向CMV/SIV载体的US 2 -11缺失型RhCMV/SIV载体是否引发对典型的CD 8 + TEM应答，（直接呈递的）免疫显性表位，具有增加的功效，3）确定复制缺陷型和细胞向性修饰的CMV载体的功效（分别在项目1和2中开发），和4）进一步定义由CMV-载体引发的免疫应答提供的独特保护的免疫学相关性。

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.