Pathogenic determinants of the SIV envelope transmembrane cytoplasmic domain

描述（由申请人提供）：HIV-1建立了一种持续感染，其特征是面对强烈的宿主免疫反应，持续的病毒复制，CD4细胞耗竭，最终导致艾滋病。对于艾滋病的SIV模型，减毒SIV提供了了解发病机制的有力工具，因为它们是可以被宿主控制的病毒。这些模型还提供了最好的证据，证明宿主免疫反应可以保护动物免受病原分离物的感染和/或疾病。然而，即使是最具特征的减毒病毒，其减毒的机制以及这种保护的免疫相关性仍是未知的。此外，当获得保护时，通常是针对同源病毒而不是异源病毒，这种情况与有效疫苗所需要的情况相去甚远。我们的实验室已经证明，SIVmac239 Env细胞质尾部保守的GYxxX运输基序的突变产生了一种严重减弱的表型，使这种高致病性病毒对宿主免疫控制敏感。我们还表明，受感染的动物不受同源SIVmac239攻击的感染，并且显著地能够控制异源攻击病毒（sivmace660）。我们建议在该模型中扩展我们的初步结果，以表征GYxxX突变对体外病毒的影响，并在恒河猴体内进行严格的研究，以确定致病性降低和宿主免疫控制的相关性。提出了三个目标。目的1将评估TM尾部突变对病毒粒子结构、组成、传染性和适应性的影响，并探索我们在初步结果中注意到的这些病毒增加中和敏感性的基础。Aim #2将全面评估粘膜和其他淋巴组织部位感染的早期和晚期事件，以确定哪些细胞被感染，发生了哪些细胞病变效应，引发了哪些炎症反应，以及该模型中观察到的衰减是否影响GYxxX突变体粘膜传播的能力。Aim #3将评估细胞和体液对GYxxX突变体的免疫反应，以确定与SIVmac239相比在广度、特异性和程度上存在什么差异。将在病原异源病毒攻击前后评估反应，以确定保护的免疫相关因素。这些目标还将利用已经发生明显代偿性突变的病毒，因为它们将成为未来研究解决这种衰减和宿主免疫控制模型背后的基本细胞机制的有力工具。总的来说，我们的工作表明，合理设计的Env运输信号突变可以被利用来破坏病毒/宿主平衡和感染的结果。该模型对发病机制和疫苗研究都具有重要意义。项目的叙述

DESCRIPTION (provided by applicant): HIV-1 establishes a persistent infection characterized by ongoing viral replication in the face of vigorous host immune responses, CD4 cell depletion, and ultimately AIDS. For SIV models of AIDS, attenuated SIVs have provided powerful tools to understand pathogenesis, as they are viruses that can be controlled by the host. These models have also provided the best evidence that host immune responses can protect animals from infection and/or disease when challenged with pathogenic isolates. However, for even the best characterized attenuated viruses, the mechanism(s) that underlie their attenuation and the immune correlates of this protection are unknown. Moreover, when protection is achieved, it is typically for homologous rather than heterologous viruses, a scenario far removed from what will be required for an effective vaccine. Our laboratory has shown that mutations in a conserved GYxxX trafficking motif in the SIVmac239 Env cytoplasmic tail produce a profoundly attenuated phenotype that renders this highly pathogenic virus susceptible to host immune control. We have also shown that infected animals are protected from infection with a homologous SIVmac239 challenge, and remarkably, are able to control a heterologous challenge virus (SIVmac E660). We propose to extend our preliminary results in this model to characterize the effects of GYxxX mutations on the virus in vitro and, in rigorous in vivo studies in rhesus macaques, to identify the correlates of reduced pathogenicity and host immune control. Three aims are proposed. Aim #1 will evaluate the effects of TM tail mutations on virion structure, composition, infectivity, and fitness, and will explore the basis for the increased neutralization sensitivity of these viruses that we noted in our preliminary results. Aim #2 will comprehensively evaluate early and late events of infection in mucosal and other lymphoid sites to determine what cells are infected, what cytopathic effects occur, what inflammatory responses are elicited, and whether the attenuation observed in this model affects the ability of GYxxX mutants to be transmitted mucosally. Aim #3 will evaluate cellular and humoral immune responses to GYxxX mutants to determine what differences exist compared to SIVmac239 in breadth, specificity and magnitude. Responses will be assessed before and after challenge with a pathogenic heterologous virus to determine what are the immune correlates of protection. These aims will also take advantage of viruses that have developed apparent compensatory mutations, as they will be powerful tools for future studies to address basic cellular mechanisms that underlie this model of attenuation and host immune control. Collectively, our work shows that rationally designed mutations in Env trafficking signals can be exploited to disrupt the viral/host balance and the outcome of infection. This model should be a highly informative for both pathogenesis and vaccine research.Project Narrative Three major obstacles in the development of an effective HIV vaccine have been 1) the lack of animal models that reproducibly show protection from genetically diverse challenge viruses; 2) a poor understanding of what components of the immune response are needed to prevent or control HIV infection; and 3) how a vaccine can be developed that will elicit these immune responses. Our application describes a new model of a live attenuated SIV in which a rationally designed mutation in the viral envelope gene creates a virus that can be completely controlled by the host immune system while conferring the ability to prevent or control infection by pathogenic viruses that are genetically different from the vaccine strain. The proposal describes plans to evaluate the pathological, immunological and virological aspects of this new model with state of the art technologies and addresses issues that are central to HIV vaccine science.