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

描述(由申请人提供)： 人类白细胞抗原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来向更常见的HLA等位基因灌输这些等位基因的保护作用？越来越多的数据支持，人类白细胞抗原-B57和-B27诱导的免疫控制在一定程度上是通过CD8+T细胞反应主导针对HIV高度保守的区域而介导的，这表明病毒逃避这些反应是以病毒复制为代价的。最近的研究表明，由这些保护性的HLA等位基因选择的CTL逃逸突变确实会大大削弱病毒的复制，而相反，由其他常见的HLA等位基因限制的显性CD8反应选择的逃逸突变不会影响病毒的复制。因此，大多数人引发的一线CD8反应被迅速逃避，而病毒几乎没有成本。然而，许多针对常见HLA等位基因的亚显性CD8反应确实针对整个HIV中高度保守的区域，在这些区域中，逃逸突变可能会损害病毒的复制。不幸的是，这些亚显性反应不会在急性感染期间出现，因为显性CD8反应掩盖了亚显性反应的扩展。我们假设，如果特定的亚显性反应不被掩盖，这些反应可能会调节对艾滋病毒的早期控制。为了验证这一假设，我们将识别CD8亚显性反应，这些反应选择HIV中唯一有害的CTL逃逸突变，并在BLT人源化小鼠模型中测试它们增强控制HIV的能力。作为概念的证明，我们将集中在四个常见的人类白细胞抗原等位基因(A02，A03，B07，B08)，并将感染BLT小鼠的HIV毒株，其中主要的CD8表位已经被敲除，以确定重新将CD8反应集中在HIV的更关键区域是否可以产生更有效的控制。我们将解决以下具体目标：目标1：利用体外复制分析、超深度测序和变异体特异性CTL反应的检测，识别针对常见HLA等位基因的亚显性CD8+T细胞反应，选择高度有害的CTL逃逸突变。目的：确定人类免疫缺陷病毒(HIV)特异性CD8+T细胞免疫优势模式和病毒逃逸途径在人类和表达共同等位基因的BLT人源化小鼠之间是否相似。目的：确定在人源化小鼠中重新聚焦针对关键的亚优势CD8表位的早期CD8反应是否能够在常见的HLA等位基因设置下实现对HIV的早期控制。这项研究将识别亚显性CD8+T细胞反应，能够选择HIV中高度有害的逃逸突变，这些突变大大损害了病毒的复制。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艾滋病毒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.