Efficacy of Strain 68-1 RhCMV Vectors Expressing 5' Leader Polypeptides

 说明(由申请人提供)：开发有效的艾滋病毒/艾滋病疫苗仍然是国际卫生领域的高度优先事项，是遏制艾滋病大流行的最具成本效益的手段。在这一点上，很少有一般的艾滋病毒/艾滋病疫苗策略仍然可以作为预防性甲型肝炎/艾滋病疫苗进行临床开发--也就是说，疫苗平台在临床前研究中显示出有希望的效果，并且在人类临床试验中没有被证明无效。其中一种方法是我们的团队开发的方法，在这种方法中，持久性巨细胞病毒(CMV)衍生的载体被用来诱导高频、无限期地持久的HIV/SIV特异性效应记忆T细胞反应。在临床前恒河猴(RM)-SIV模型中，我们已经证明，用68-1株RhCMV/SIVgag、/SIVpoll、/SIVenv/SIVrevtnef载体接种SIV后，50%的猕猴表现出完全、持久的保护和病毒学和免疫学标准的最终清除。保护很可能取决于效应器T细胞拦截新生T细胞的能力 HIV/SIV感染在感染后立即出现(由于记忆扩展和效应器分化的要求，没有反应延迟)。如果这一假设是正确的，人们可以推测，如果最早的艾滋病毒/SIV免疫原能在最初感染后几个小时内被靶向，可能会取得更大的疗效。最近发现了一组新的5‘前导序列编码的HIV和SIV多肽，这些多肽在HIV/SIV感染细胞中很早就表达，并且具有高度的免疫原性。因此，考虑到每个剪接和非剪接的HIV/SIV mRNA都含有5‘前导序列，因此5’前导多肽(5‘-LP)是一个非常有吸引力的疫苗靶标，因此该区域编码的多肽将在感染后的早期广泛表达。因此，本研究的主要目的将是确定表达SIV 5‘前导多肽的RhCMV载体能否保护恒河猴免受高致病性SIVmac239的黏膜攻击，以及这些载体与表达常规SIV开放阅读框的载体是否能够增强RhCMV载体疫苗的整体保护效果。这些目标将通过实验解决以下特定目标：(I)鉴定68-1株RhCMV/5‘-LP载体在恒河猴体内的免疫原性，并利用这种免疫原性结合生化分析，确定SIV感染的CD4+T细胞表达的5’-LP表位；(Ii)确定68-1株RhCMV/5‘-LP载体疫苗对限制剂量直肠内SIV攻击的有效性；如果满足Go/No-Go标准，(Iii)检测包含68-1株RhCMV/5‘-LP载体和68-1株表达Gag、Rev/Nef/Tat、Pol、Env的组合疫苗的免疫原性和效力。

 DESCRIPTION (provided by applicant): The development of an effective HIV/AIDS vaccine remains a high international health priority as the most cost-effective means to stem the AIDS pandemic. At this point in time, there are very few general HIV/AIDS vaccine strategies that remain viable for clinical development as a prophylactic HAV/AIDS vaccine - that is, vaccine platforms that have shown promising efficacy in preclinical studies and not been proved ineffective in human clinical trials. Among these is the approach developed by our group in which persistent Cytomegalovirus (CMV)-derived vectors are used to elicit high-frequency, indefinitely persistent HIV/SIV- specific effector-memory T cell responses. In the preclinical rhesus macaque (RM) - SIV model, we have demonstrated that after mucosal SIV challenge >50% of monkeys vaccinated with strain 68-1 RhCMV/SIVgag, /SIVpol, /SIVenv, /SIVrevtatnef vectors show complete, durable protection and eventual clearance by virologic and immunologic criteria. Protection is likely determined by the ability of effector T cells to intercept a nascent HIV/SIV infection immediately upon acquisition (with no response delay due to requirement for anamnestic expansion and effector differentiation). If this assumption is correct one could speculate that a greater efficacy could be achieved if the earliest HIV/SIV immunogens could be targeted within hours after initial infection. Recently a novel set of 5' leader sequence-encoded HIV and SIV polypeptides was discovered, and these polypeptides are expressed very early in HIV/SIV-infected cells and were highly immunogenic. Therefore, the 5' leader polypeptides (5'-LP) are an extremely attractive vaccine target considering that every spliced and unspliced HIV/SIV mRNA contains the 5' leader sequence, and thus polypeptides encoded from this region will be ubiquitously expressed rapidly and early following infection. Thus, the major objective of the research proposed here will be to determine whether RhCMV vectors expressing SIV 5' leader polypeptides can protect rhesus macaques from mucosal challenge with highly pathogenic SIVmac239, and if these vectors in combination with vectors expressing conventional SIV open reading frames, can enhance the overall protective efficacy of the RhCMV-vectored vaccine. These objectives will be accomplished by experimentally addressing the following Specific Aims: (i) To characterize the immunogenicity of strain 68-1 RhCMV/5'-LP vectors in rhesus macaques and to use this immunogenicity, in combination with biochemical analysis, to define the 5'-LP epitopes expressed by SIV-infected CD4+ T cells; (ii) To determine the efficacy of strain 68-1 RhCMV/5'-LP vector vaccination against limiting-dose, intra-rectal SIV challenge; and if Go/No-Go criteria are met, (iii) To determine the immunogenicity and efficacy of a combination vaccine containing both strain 68-1 RhCMV/5'- LP vectors and strain 68-1 RhCMV vectors expressing Gag, Rev/Nef/Tat, Pol, Env.