Role of APOBEC3 in in vivo Restriction of Retrovirus Infection

描述（由申请人提供）：在整个进化过程中，感染性病原体已感染原核生物和真核生物。事实上，在生物体和它们的感染因子之间存在着共同进化，宿主会产生保护性反应，而感染因子则会对它们采取适应性对策。一种最近鉴定的病毒限制系统是载脂蛋白B编辑复合物（APOBEC或A）蛋白质家族。人APOBEC 3G首先被鉴定为HIV感染中的抗病毒因子。人类基因组编码多种A3蛋白，包括hA 3G和hA 3F。hA 3G和hA 3F限制Vif缺陷型人类免疫缺陷病毒1（HIV-1）的感染。A3蛋白被包装到病毒体中，并在新感染的细胞中抑制逆转录病毒复制，部分是通过对负链DNA中间体上的胞嘧啶脱氨基和通过迄今尚未表征的机制。我们最近提供了A3蛋白的抗病毒功能的第一个体内证明。我们发现，小鼠乳腺肿瘤病毒（MMTV）的复制在体内被内源性mA 3抑制，因为该基因的靶向缺失的小鼠比其野生型同窝出生的小鼠更容易感染。我们还发现hA 3G被包装到MMTV病毒颗粒中并抑制培养细胞的感染。我们在这里建议使用MMTV进一步探测mA 3和hA 3蛋白的功能。我们将研究A3蛋白被包装成病毒体的机制，限制逆转录病毒感染的体外和体内，在A3基因多态性的作用，在影响病毒限制和是否A3在乳腺组织中的表达限制了牛奶传播的病毒。作为这些研究的结果，我们将知道A3蛋白在外源性病毒感染中起什么作用。这些研究将为理解这种内在免疫因子家族如何抑制外源病毒对小鼠和其他物种的病毒感染（包括人类的HIV-1感染）提供基础。 公共卫生相关性：该项目将研究一种新发现的抗病毒宿主限制因子APOBEC 3，它抑制HIV-1感染。我们的实验将利用我们实验室开发的独特小鼠模型来研究APOBEC 3在体内限制小鼠逆转录病毒小鼠乳腺肿瘤病毒感染中的作用。这些研究将提供深入了解APOBEC 3蛋白如何在实验易处理的小鼠模型中抑制人类逆转录病毒（如HIV-1）的感染。

DESCRIPTION (provided by applicant): Infectious agents have infected prokaryotes and eukaryotes throughout evolution. Indeed, there is co-evolution among organisms and their infectious agents, with development of protective responses in the hosts and adaptive countermeasures to them by the infectious agents. One recently identified system of viral restriction is the Apolipoprotein B editing complex (APOBEC or A) family of proteins. Human APOBEC3G was first identified as an anti-viral factor in HIV infection. The human genome encodes multiple A3 proteins, including hA3G and hA3F. hA3G and hA3F restrict infection by Vif-deficient human immunodeficiency virus 1 (HIV-1). A3 proteins are packaged into virions and inhibit retroviral replication in newly infected cells, in part by deaminating cytosines on negative strand DNA intermediates and through as of yet uncharacterized mechanisms. We recently provided the first in vivo demonstration of an antiviral function for A3 proteins. We showed that mouse mammary tumor virus (MMTV) replication was inhibited by endogenous mA3 in vivo, since mice with targeted deletion of this gene were more susceptible to infection than their wild type littermates. We also showed that hA3G was packaged into MMTV virions and inhibited infection of cultured cells. We propose here to use MMTV to further probe the function of mA3 and hA3 proteins. We will examine the mechanism by which A3 proteins are packaged into virions, restrict retrovirus infection in vitro and in vivo, the role that polymorphisms in the A3 genes plays in affecting virus restriction and whether A3 expression in mammary tissue restricts milk-borne transmission of virus. As a consequence of these studies, we will know what role/s A3 proteins play in infection by exogenous viruses. These studies will provide a basis for understanding how this family of intrinsic immune factors inhibits viral infection of the mouse and other species by exogenous viruses, including HIV-1 infection of humans. PUBLIC HEALTH RELEVANCE: This project will investigate a newly discovered anti-viral host restriction factor, APOBEC3, which inhibits HIV-1 infection. Our experiments will take advantage of a unique mouse model developed by our lab to examine the role of APOBEC3 in restricting infection by the murine retrovirus mouse mammary tumor virus in vivo. These studies will provide insight into how APOBEC3 proteins inhibit infection by human retroviruses such as HIV-1 in an experimentally tractable mouse model.