Determinants of retroviral replication in non-native hosts for modeling HIV infection

项目总结/摘要 HIV-1由于受到几种特异性宿主因子的限制而不会持续感染猕猴 需要使用嵌合SIV/HIV-1病毒（SHIV）作为替代物来模拟猕猴中的HIV-1感染。 用SHIV感染猕猴是疫苗和预防研究的最优选模型系统 因为SHIV编码HIV-1包膜糖蛋白（Env）-HIV-1中和抗体的关键靶点。 因为疫苗的目标是预防新的感染，所以基于循环、传播形式的Env 需要变体作为攻击病毒。现有的SHIV/猕猴模型通常采用编码 来自实验室适应病毒的HIV-1 Env，其中和敏感性与循环Env变体不同。 这显著限制了现有SHIV/猕猴模型预测SHIV/猕猴中有效干预的能力。 人类编码循环Env变体的SHIV的开发一直极具挑战性，主要是 因为这种SHIV在猕猴体内复制很差，如果有的话。为了增加它们的复制和致病性， 需要在猕猴体内通过连续传代进行广泛的适应。猕猴连续传代的过程 导致Env中适应性突变的积累，这有助于稳健的复制。 连续传代通常在感染的前两周内进行，在此期间， 对感染产生强有力的I型干扰素（IFN）反应。宿主的干扰素反应是一个早期屏障 抗感染，因为IFN的产生上调几种IFN刺激基因（ISG）的表达， 这导致了“抗病毒状态”的诱导。由某些ISG编码的蛋白质，称为限制性内切酶。 因素，作为对抗跨物种慢病毒传播的有效屏障。因此，猕猴限制因子 具有阻断SHIV感染的潜力，因为它们可以拮抗HIV-1 Env。我们最近发现了一种猕猴 干扰素诱导的跨膜蛋白（IFITM）作为选择性限制SHIV复制的ISG 编码循环HIV-1 Env变体。 我们的初步结果表明，未传代的SHIV在猕猴淋巴细胞中被IFN有效抑制。 相反，连续传代的SHIV对IFN具有抗性。我们发现Env中两个N-连接聚糖的丢失 在连续传代时足以增加复制并赋予对IFN的抗性。这项研究提案将： 1)表征连续传代的SHIV的Env的适应性变化，其增加复制和IFN 2）确定N-连接的Env聚糖在SHIV感染原代猕猴免疫细胞中的作用 亚群离体，和粘膜传播和致病性的SHIV在体内;和3）评估的贡献 五种猕猴IFITM同源物，它们被IFN上调，在限制未传代的IFN敏感的 SIV.完成后，这项研究将提供驱动选择的宿主-病毒界面的机制见解， 适应性和致病性。

PROJECT SUMMARY/ABSTRACT HIV-1 does not persistently infect macaques due to restriction by several species-specific host factors necessitating the use of chimeric SIV/HIV-1 viruses (SHIVs) as surrogates to model HIV-1 infection in macaques. Infection of macaques with SHIVs is the most preferred model system for vaccine and prevention studies because SHIVs encode HIV-1 Envelope glycoprotein (Env) – a key target of HIV-1 neutralizing antibodies. Because the goal of vaccines is to prevent new infection, SHIVs based on circulating, transmitted forms of Env variants are desired as challenge viruses. Existing SHIV/macaque models typically employ SHIVs that encode HIV-1 Env from laboratory-adapted viruses, whose neutralization sensitivities differ from circulating Env variants. This significantly limits the ability of the existing SHIV/macaque models to predict efficacious intervention(s) in humans. Development of SHIVs encoding circulating Env variants has been extremely challenging, mainly because such SHIVs replicate poorly in macaques, if at all. To increase their replication and pathogenicity, SHIVs require extensive adaptation in vivo via serial passage in macaques. The process of serial macaque passage results in accumulation of adaptive mutations in Env that facilitates robust replication. Serial passage is typically performed within the first two weeks of infection, a time during which macaques mount a robust type-I interferon (IFN) response to infection. The host IFN response presents an early barrier against infection because production of IFNs upregulates expression of several IFN-stimulated genes (ISGs), which results in induction of an ‘antiviral state’. Proteins encoded by certain ISGs, referred to as restriction factors, act as potent barriers against cross-species lentiviral transmission. Thus, macaque restriction factors have the potential to block SHIV infection as they can antagonize HIV-1 Env. We recently identified macaque interferon-induced transmembrane proteins (IFITMs) as ISGs that selectively restrict replication of SHIVs encoding circulating HIV-1 Env variants. Our preliminary results suggest that unpassaged SHIV is potently inhibited by IFN in macaque lymphocytes. In contrast, serial passaged SHIVs are resistant to IFN. We found that the loss to two N-linked glycans in Env upon serial passage is sufficient to increase replication and confer resistance to IFN. This research proposal will: 1) characterize the adaptive changes in Env of serial passaged SHIVs that increase replication and IFN resistance; 2) determine the role of N-linked Env glycans in SHIV infection of primary macaque immune cell subsets ex vivo, and mucosal transmission and pathogenicity of SHIVs in vivo; and 3) evaluate the contribution of five macaque IFITM homologs, which are upregulated by IFN, in restriction of unpassaged, IFN-sensitive SHIV. Upon completion, this study will provide mechanistic insights at the host-viral interface that drive selection, adaptation, and pathogenicity of SHIVs in macaques.