Innate Restriction Factor Modulation of Retrovirus-specific Humoral Immunity

描述(由申请人提供)： 开发一种能引起强有力的中和抗体反应的HIV-1疫苗是全球卫生优先事项，但这种反应与对自然感染的保护无关。因此，确定提高对HIV-1的体液免疫的机制可能对疫苗开发工作起到至关重要的指导作用。与人类感染HIV-1或猕猴感染SIV不同，感染Friend逆转录病毒(FV)的耐药小鼠会产生中和抗体反应，这对康复至关重要。此外，疫苗对FV的保护依赖于中和抗体反应。有趣的是，Fv特异的中和抗体反应受到关键宿主基因Rfv3的显著影响。我们最近确定Rfv3为APOBEC3，一种对包括HIV-1在内的逆转录病毒具有广泛活性的脱氧胞苷脱氨酶(Santiago ML等人)。2008年。科学321：1343-46)。APOBEC3限制下一个靶细胞中的逆转录病毒，促进融合能力强、非感染性的病毒粒子在体内释放，这些病毒粒子可能起到“天然B细胞免疫原”的作用。因此，解开APOBEC3和免疫反应的体液臂之间令人着迷的联系可能对HIV-1疫苗的开发具有重要意义。我们的总体目标是探索APOBEC3中和抗体在两个致病逆转录病毒系统中的联系。在具体目标1中，我们建议在FV小鼠模型中确定APOBEC3/Rfv3表型的潜在机制。这将包括监测病毒特异性B细胞的发育，询问I型干扰素在体内对APOBEC3的调节作用，以及评估区分保护性和非保护性抗体反应的分子特性。值得注意的是，灵长类慢病毒通过Vif的作用对抗猿猴和人类APOBEC3的同源物。因此，减弱Vif功能可能挽救APOBEC3，提高中和抗体反应。在具体目标2中，我们建议确定VIF减毒对SIV感染的体液免疫的影响。这将包括比较感染野生型、Vif减毒和Nef缺失SIVmac239的恒河猴的APOBEC3功能、病毒进化、B细胞表型和中和抗体的发展。SIVmac239很少会引起强烈的中和抗体反应，并会引发胃肠道内快速而广泛的CD4+T细胞耗尽，可能会削弱粘膜免疫反应。通过分析连续的粪便和尿液样本，我们将测试启用APOBEC3功能是否会改善病毒特异性粘膜IgA反应。如果小鼠的APOBEC3/Rfv3表型延伸到灵长类慢病毒感染，诱导的全身和粘膜病毒特异性抗体的分子特性可能会为HIV-1疫苗的设计带来关键和创新的见解。对APOBEC3介导的先天免疫和逆转录病毒特异性中和抗体开发之间的相互作用的详细见解可能对艾滋病毒疫苗的构建和评估起到关键指导作用。

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.