Role of APOBEC3 in in vivo Restriction of Retrovirus Infection

描述（由申请人提供）：传染因子在进化过程中感染了原核生物和真核生物。事实上，生物体和它们的感染因子之间存在着共同进化，宿主产生了保护反应，感染因子对它们采取了适应性对策。最近发现的一个病毒限制系统是载脂蛋白B编辑复合体（APOBEC或A）蛋白家族。人类APOBEC3G首次被确定为HIV感染中的抗病毒因子。人类基因组编码多种A3蛋白，包括hA3G和hA3F. hA3G和hA3F限制vif缺陷人类免疫缺陷病毒1 （HIV-1）的感染。A3蛋白被包装成病毒粒子，在新感染的细胞中抑制逆转录病毒的复制，部分是通过对负链DNA中间体上的胞嘧啶脱氨和尚未确定的机制。我们最近首次在体内证明了A3蛋白的抗病毒功能。我们发现小鼠乳腺肿瘤病毒（MMTV）的复制在体内受到内源性mA3的抑制，因为靶向缺失该基因的小鼠比野生型小鼠更容易受到感染。我们还发现，hA3G被包装成MMTV病毒粒子，并抑制培养细胞的感染。我们建议使用MMTV进一步探索mA3和hA3蛋白的功能。我们将研究A3蛋白被包装成病毒粒子，在体外和体内限制逆转录病毒感染的机制，A3基因多态性在影响病毒限制中的作用，以及A3在乳腺组织中的表达是否限制病毒的乳传。作为这些研究的结果，我们将知道/s A3蛋白在外源病毒感染中起什么作用。这些研究将为了解这一内在免疫因子家族如何抑制外源病毒（包括人类HIV-1感染）对小鼠和其他物种的病毒感染提供基础。

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.