Viral Constraints on SIV Escape from Cytotoxic T Lymphocytes

描述（由申请人提供）：估计全世界有3900万人感染艾滋病毒-1，艾滋病毒流行病已成为一个严重的全球健康问题。鉴于40%的感染者生活在抗逆转录病毒药物无法广泛获得的发展中国家，开发有效疫苗的必要性至关重要。我们的长期目标是阐明病毒进化和预防感染的免疫相关因素，作为开发有效的艾滋病毒疫苗的必要先决条件。细胞毒性T淋巴细胞（CTL）在控制人类免疫缺陷病毒（HIV）感染和恒河猴猴免疫缺陷病毒（SIV）感染中发挥核心作用。然而，HIV/SIV的高突变率允许不断产生病毒变体，在不断进化的适应性免疫反应中保持最佳适应度。能够破坏有效CTL反应的病毒变异已被证明会导致病毒复制增加和疾病进展。因此，确定病毒分离株用于远离表位特异性CTL反应的突变策略非常重要，这样我们就可以预测关键表位的变化，并制定疫苗方法来避免选择逃逸变体。我们的初步研究表明，在猴-人免疫缺陷病毒（SHIV）毒株89.6P中出现的2 p11C， C-M Gag表位替换，允许病毒从感染的Mamu-A*01+恒河猴的CTL识别中逃脱，这与衣壳蛋白侧下游氨基酸替换的出现有暂时的相关性。我们的假设是，SHIV-89.6P在高度保守的免疫显性Gag p11C CTL表位上的逃逸并不常见，因为需要额外的代偿性突变来促进这种病毒逃逸。在拟议的研究中，我们将使用电子显微镜和x射线结晶检查表位和侧翼突变对病毒核心形成的生化、结构和功能相关性。此外，我们将在体内评估逃逸变异SHIV-89.6P的致病性和免疫学后果。最终，这些研究将有助于设计新的疫苗接种策略，以防止病毒逃逸突变的演变。

DESCRIPTION (provided by applicant): With 39 million people estimated to be infected with HIV-1 worldwide, the HIV epidemic has become a serious global health problem. Given that 40% of infected individuals live in developing countries where antiretroviral medications are not widely available, the need to develop an effective vaccine is of paramount importance. Our long-term goal is to elucidate viral evolution and immune correlates of protection against infection as necessary prerequisites to the development of an effecitve HIV vaccine. Cytotoxic T lymphocytes (CTL) play a central role in controlling human immunodeficiency virus (HIV) infection in humans and simian immunodeficiency virus (SIV) in rhesus monkeys. However, the high mutation rate of HIV/SIV allows for the constant generation of viral variants that maintain optimal fitness in the context of an evolving adaptive immune response. Viral variants that are capable of subverting potent CTL responses have been shown to result in increased virus replication and disease progression. Therefore, it is important to define the strategies used by virus isolates to mutate away from epitope-specific CTL responses, so that we can anticipate variations in key epitopes and formulate vaccine approaches to avert selection of escape variants. Our preliminary work showed that the appearance of a position 2 p11C, C-M Gag epitope substitution in a simian-human immunodeficiency virus (SHIV) strain 89.6P that allowed viral escape from CTL recognition in an infected Mamu-A*01+ rhesus monkey is temporally correlated with the emergence of a flanking downstream amino acid substitution in the capsid protein. Our hypothesis is that the SHIV-89.6P escape at the highly conserved, immunodominant Gag p11C CTL epitope is infrequent because additional compensatory mutations are required to facilitate this viral escape. In the proposed studies, we will examine the biochemical, structural, and functional relevance of the epitope and flanking mutations on viral core formation using electron microscopy and x-ray crystallization. In addition, we will evaluate the pathogenicity and immunological consequences of the escape variant SHIV-89.6P in vivo. Ultimately, these studies will facilitate the design of novel vaccination strategies that may prevent the evolution of viral escape mutations.