The role of APOBEC3 proteins in innate immune responses in developing thymocytes

 描述(申请人提供)：灵长类慢病毒都编码一种Vif蛋白，该蛋白已被证明与载脂蛋白mRNA编辑，催化多肽样3(APOBEC3)超家族的成员相互作用。APOBEC3蛋白是胞苷脱氨酶，被认为在先天抗病毒限制中发挥重要作用。人类和猕猴都编码7个APOBEC3基因(A3A、A3B、A3C、A3D、A3F、A3G和A3H)。APOBEC3蛋白大致可分为单脱氨酶结构域(A3A、A3C和A3H)和双脱氨酶结构域(A3B、A3D、A3F和A3G)。胸腺是维持CD_4~+T细胞动态平衡的重要器官，也是生命中原始CD_4~+T细胞的主要来源。人类感染HIV-1可导致未成熟胸腺细胞的增殖抑制和/或可直接感染CD4+胸腺细胞，导致CD4+T细胞的产生受损。因此，外周CD4+T细胞的产生和破坏之间的不平衡可能会导致它们随着时间的推移而逐渐下降，最终导致艾滋病。对于严重依赖胸腺来产生新的CD4+T细胞的儿科患者来说，胸腺尤其重要。到目前为止，还没有关于A3基因/蛋白在发育中的胸腺细胞中表达的信息。我们提供的初步数据表明，A3G/A3F蛋白不在双阴性(DN：CD4-CD8-)或双阳性(DP：CD4+CD8+)的胸腺细胞中表达，而在人胸腺的单阳性(SP)CD4+细胞中表达。这表明这个重要的病毒限制因子的表达可能是发育调节的。在具体目标1中，我们建议进行一项全面的检查，以确定当A3G/F基因(和其他A3基因)表达激活时胸腺细胞发育的阶段。在特定目标2中，我们建议确定A3基因表达的阶段是否与限制HIV-1和HIV∆vif病毒的能力相关，并确定已知的A3基因表达诱导剂是否会刺激表达。这些研究将为A3基因在发育过程中的表达、病毒在胸腺中的持续存在以及针对Vif/A3相互作用的抗病毒药物的开发提供新的见解。

 DESCRIPTION (provided by applicant): The primate lentiviruses all encode for a Vif protein that has been shown to interact with members of the apolipoprotein mRNA-editing, catalytic polypeptide-like 3 (APOBEC3) superfamily of proteins. The APOBEC3 proteins are cytidine deaminases that are thought to play an important role in innate anti-viral restriction. Humans and macaques both encode for seven APOBEC3 genes (A3A, A3B, A3C, A3D, A3F, A3G, and A3H). The APOBEC3 proteins can be broadly divided into the single deaminase domain (A3A, A3C, and A3H) and double deaminase domain proteins (A3B, A3D, A3F, and A3G). The thymus is essential to CD4+ T cell homeostasis and is the major source of naïve CD4+ T cells throughout life. HIV-1 infection of humans can lead to the inhibition of proliferation of immature thymocytes and/or can directly infect CD4+ thymocytes leading to impaired production of CD4+ T cells. Thus, an imbalance between production and destruction of peripheral CD4+ T cells likely leads to their progressive decline over time and eventually to AIDS. The thymus is particularly important in pediatric patients who depend heavily on their thymus for generation of new CD4+ T cells. To date no information is available on the expression of the A3 genes/proteins in cells of the developing thymus. We present preliminary data that indicate that A3G/A3F proteins are not expressed in the double negative (DN: CD4-CD8-) or double positive (DP:CD4+CD8+) thymocytes but are expressed in single positive (SP CD4+) cells of the human thymus. This indicates that the expression of this important virus restriction factor is likely developmentally regulated. In Specific Aim 1, we propose to perform a comprehensive examination to determine the stage of thymocyte development when A3G/F gene (and other A3 genes) expression becomes activated. In Specific Aim 2, we propose to determine if the stage of A3 gene expression correlates with the ability to restrict HIV-1 and HIV∆vif viruses and determine if known inducers of A3 gene expression will stimulate expression. The proposed studies will provide novel insight into the expression of A3 genes during development, viral persistence in the thymus, and in the development of antiviral drugs targeting Vif/A3 interactions.