Protective Role of Subdominant Responses to HIV Restricted by Common HLA Alleles

描述（由申请人提供）： HLA I类等位基因B57和B27与HIV的控制相关。不幸的是，大多数人不表达这些保护性等位基因，因此无法控制病毒复制和减缓疾病进展。如果我们能够理解这种控制的机制，我们是否能够通过疫苗接种将这些等位基因的保护作用灌输给更常见的HLA等位基因？越来越多的数据支持，由HLA-B57和-B27引起的免疫控制部分是由它们通过CD 8 + T细胞应答对HIV的高度保守区域的显性靶向介导的，这表明病毒逃避这些应答是以病毒复制的实质性代价来的。最近的研究表明，由这些保护性HLA等位基因选择的CTL逃逸突变实质上损害病毒复制，而相反，由其他常见HLA等位基因限制的显性CD 8应答选择的逃逸突变不影响病毒复制。因此，大多数个体引起的一线CD 8应答被迅速逃避，对病毒几乎没有成本。然而，许多对常见HLA等位基因的亚显性CD 8应答确实靶向整个HIV的高度保守区域，其中逃逸突变可能会损害病毒复制。不幸的是，由于显性CD 8应答“掩盖”了亚显性应答的扩展，这些亚显性应答在急性感染期间不会出现。我们假设，如果特定的亚显性反应不被掩盖，这些反应可能介导的早期控制艾滋病毒。为了验证这一假设，我们将鉴定亚显性CD 8应答，其选择HIV中独特有害的CTL逃逸突变，并在BLT人源化小鼠模型中测试其增强HIV控制的能力。作为概念验证，我们将集中于四种常见的HLA等位基因（A02、A03、B 07、B 08），并将用HIV毒株感染BLT小鼠，其中显性CD 8表位已被“敲除”，以确定重新聚焦针对HIV更关键区域的CD 8应答是否会导致更有效的控制。我们将解决以下具体目标：目标1：确定亚显性CD 8 + T细胞反应常见的HLA等位基因，选择高度有害的CTL逃逸突变，使用体外复制试验，超深测序，检测变异特异性CTL反应。目标二：确定人类和表达共同HLA等位基因的BLT人源化小鼠之间HIV特异性CD 8 + T细胞免疫优势模式和病毒逃逸途径是否相似。目标3：确定在人源化小鼠中重新聚焦针对关键亚显性CD 8表位的早期CD 8应答是否能够在常见HLA等位基因的情况下早期控制HIV。这项研究将确定亚显性CD 8 + T细胞反应，能够选择高度有害的逃逸突变的艾滋病毒，大大削弱病毒复制。这些反应的效力将在一种新的人源化小鼠模型中进行测试，以确定对设计有效的HIV疫苗至关重要的免疫反应。

DESCRIPTION (provided by applicant): The HLA class I alleles B57 and B27 are associated with control of HIV. Unfortunately, most individuals do not express these protective alleles, and are thus unable to control viral replication and slow disease progression. If we could understand the mechanisms of this control, might we be able to instill the protective effects of these alleles to more common HLA alleles through vaccination? Growing data supports that the immune control elicited by HLA-B57 and -B27 is mediated in part by their dominant targeting of highly conserved regions of HIV by CD8+ T cell responses, suggesting that viral escape from these responses comes at a substantial cost to viral replication. Recent studies now illustrate that CTL escape mutations selected by these protective HLA alleles do substantially impair viral replication, while in contrast escape mutations selected by dominant CD8 responses restricted by other common HLA alleles do not impact viral replication. Therefore, the front-line CD8 responses elicited by most individuals are rapidly evaded with little to no cost to the virus. Many subdominant CD8 responses to common HLA alleles do, however, target highly conserved regions throughout HIV in which escape mutations might impair viral replication. Unfortunately, these subdominant responses don't arise during acute infection due to dominant CD8 responses that 'mask' the expansion of subdominant responses. We hypothesize that if specific subdominant responses were not masked that these responses might mediate early control of HIV. To test this hypothesis we will identify subdominant CD8 responses that select for uniquely deleterious CTL escape mutations in HIV and test their ability to enhance control of HIV in the BLT humanized mouse model. As a proof of concept, we will focus on four common HLA alleles (A02, A03, B07, B08) and will infect BLT mice with HIV strains in which the dominant CD8 epitopes have been 'knocked out' to determine whether refocusing CD8 responses against more critical regions of HIV results in more effective control. We will address the following specific aims: Aim 1: Identify subdominant CD8+ T cell responses for common HLA alleles that select for highly deleterious CTL escape mutations using in vitro replication assays, ultra-deep sequencing, and detection of variant-specific CTL responses. Aim 2: Determine whether HIV-specific CD8+ T cell immunodominance patterns and viral escape pathways are similar between humans and BLT humanized mice expressing common HLA alleles. Aim 3: Determine whether refocusing early CD8 responses against critical subdominant CD8 epitopes in humanized mice can enable early control of HIV in the setting of common HLA alleles. This study will identify subdominant CD8+ T cell responses capable of selecting for highly deleterious escape mutations in HIV that substantially impair viral replication. The potency of these responses will be tested in a new humanized mouse model to identify immune responses critical to the design of an effective HIV vaccine.