Innate Restriction Factor Modulation of Retrovirus-specific Humoral Immunity

描述（由申请人提供）： 开发一种能激发有效中和抗体反应的HIV-1疫苗是全球卫生的优先事项，但这种反应与自然感染的保护无关。因此，确定提高抗HIV-1体液免疫的机制可能对疫苗开发工作具有重要指导意义。与人类的HIV- 1感染或猕猴的SIV感染相反，感染Friend逆转录病毒（FV）的小鼠的耐药株会产生中和抗体反应，这对恢复至关重要。此外，针对FV的疫苗保护依赖于中和抗体应答。有趣的是，FV特异性中和抗体应答受关键宿主基因Rfv 3的显著影响。我们最近将Rfv 3鉴定为Apobec 3，其是一种对逆转录病毒（包括HIV-1）具有广泛活性的脱氧胞苷脱氨酶（圣地亚哥ML等人，2008年）。Science 321：1343-46）。Apobec 3限制逆转录病毒进入下一个靶细胞，促进可在体内作为“天然B细胞免疫原”发挥功能的具有融合能力的非感染性病毒体的释放。因此，解开Apobec 3和免疫反应的体液分支之间的迷人联系可能对HIV-1疫苗的开发具有重要意义。我们的总体目标是探测两种致病性逆转录病毒系统中的Apobec 3中和抗体连接。在具体目标1中，我们提出确定FV鼠模型中Apobec 3/Rfv 3表型的潜在机制。这将涉及监测病毒特异性B细胞发育，询问I型干扰素在体内调节Apobec 3的作用，并评估区分保护性与非保护性抗体应答的分子性质。值得注意的是，灵长类慢病毒通过Vif的作用拮抗Apobec 3的猿和人类同源物。因此，减弱Vif功能可以拯救Apobec 3并改善中和抗体应答。在具体目标2中，我们建议确定Vif减毒对针对SIV感染的体液免疫的影响。这将涉及比较感染野生型、Vif减毒和Nef缺失的SIVmac 239的恒河猴中Apobec 3功能、病毒进化、B细胞表型和中和抗体形成。SIVmac 239很少激发强烈的中和抗体应答，并在胃肠道中触发快速和广泛的CD 4 + T细胞耗竭，可能削弱粘膜免疫应答。通过分析连续的粪便和尿液样本，我们将测试启用Apobec 3功能是否会改善病毒特异性粘膜伊加应答。如果小鼠中的Apobec 3/Rfv 3表型扩展到灵长类慢病毒感染，则诱导的全身和粘膜病毒特异性抗体的分子特性可能为HIV-1疫苗设计提供关键和创新的见解。关于Apobec 3介导的先天免疫和逆转录病毒特异性中和抗体发展之间相互作用的详细见解可能会对HIV疫苗的构建和评估产生重要指导作用。

DESCRIPTION (provided by applicant): Developing an HIV-1 vaccine that elicits a potent neutralizing antibody response is a global health priority, but this response is not associated with protection in natural infections. Identifying mechanisms to improve humoral immunity against HIV-1 may therefore critically guide vaccine development efforts. In contrast to HIV- 1 infection in humans or SIV infection in macaques, resistant strains of mice infected with Friend retrovirus (FV) develop neutralizing antibody responses that are critical for recovery. Furthermore, vaccine protection against FV is dependent on neutralizing antibody responses. Interestingly, the FV-specific neutralizing antibody response is significantly influenced by a key host gene, Rfv3. We recently identified Rfv3 as Apobec3, a deoxycytidine deaminase with broad activity against retroviruses, including HIV-1 (Santiago ML et al. 2008. Science 321:1343-46). Apobec3 restricts retroviruses in the next target cell, facilitating the release of fusion- competent, non-infectious virions that may function as "natural B-cell immunogens" in vivo. Unraveling the fascinating link between Apobec3 and the humoral arm of the immune response may therefore have important implications for HIV-1 vaccine development. Our overall objective is to probe the Apobec3-neutralizing antibody link in two pathogenic retrovirus systems. In Specific Aim 1, we propose to determine the underlying mechanism for the Apobec3/Rfv3 phenotype in the FV murine model. This would involve monitoring virus- specific B cell development, interrogating the role of Type I Interferon regulation of Apobec3 in vivo, and assessing the molecular properties that distinguish a protective versus a non-protective antibody response. Notably, primate lentiviruses antagonize the simian and human homologues of Apobec3 through the action of Vif. Thus, attenuating Vif function may rescue Apobec3 and improve neutralizing antibody responses. In Specific Aim 2, we propose to determine the impact of Vif attenuation on humoral immunity against SIV infection. This would involve comparing Apobec3 function, viral evolution, B cell phenotypes and neutralizing antibody development in rhesus macaques infected with wild-type, Vif-attenuated and Nef-deleted SIVmac239. SIVmac239 rarely elicits a strong neutralizing antibody response and triggers rapid and extensive CD4+ T cell depletion in the gastrointestinal tract, likely weakening mucosal immune responses. By analyzing sequential fecal and urine samples, we will test whether enabling Apobec3 function will improve virus-specific mucosal IgA responses. If the Apobec3/Rfv3 phenotype in mice extends to primate lentivirus infections, the molecular properties of induced systemic and mucosal virus-specific antibodies may yield crucial and innovative insights for HIV-1 vaccine design. Detailed insights on the interplay between Apobec3-mediated innate immunity and retrovirus-specific neutralizing antibody development may critically guide the construction and evaluation of HIV vaccines.