Intrinsic immune sensing of retroviral infections in SAMHD1 knockout mice

dNTP水解酶SAMHD 1的突变与自身免疫性疾病Aicardi-Goutières综合征相关，其标志是I型干扰素（IFN）的自发上调。此外，SAMHD 1作为一种抗病毒限制因子，阻断HIV-1和其他逆转录病毒在骨髓细胞和静止期CD 4 + T细胞中的感染。在不存在SAMHD 1的情况下，HIV-1在感染人树突状细胞（DC）后诱导I型IFN应答。新产生的HIV蛋白或病毒DNA的感应都被认为是引发这种对感染的免疫反应的原因。目前尚不清楚在SAMHD 1不存在的情况下，病毒诱导的和内源性应答是如何触发的，以及这两种应答是由相同还是不同的免疫传感器引发的。因此，我们将使用我们最近描述的SAMHD 1基因敲除小鼠模型作为工具，比较内源性和病毒诱导的免疫反应，在SAMHD 1的情况下。缺乏SAMHD 1和功能性I型干扰素受体（IFNAR-/-）的小鼠不显示内源性免疫应答。因此，我们将感染小鼠或来自SAMHD 1-/-小鼠的骨髓来源的树突状细胞（BMDC），所述小鼠是IFNAR熟练的或缺乏的，以确定内源性免疫激活是否起抗病毒作用，并揭示SAMHD 1在体外和体内的全部抗病毒效力。比较感染后来自这些小鼠的BMDC的转录组将揭示个体转录物是否响应于感染而特异性上调。因此，该分析将确定内源性和病毒诱导的先天性应答是否是由于相同途径的刺激。在本研究的第二个目标，我们将进一步阐明逆转录病毒传感器的性质。我们将阐明DNA传感器cGAS在检测SAMHD 1缺失的逆转录病毒感染中的作用。因此，我们将分析SAMHD 1/cGAS和SAMHD 1/STING双敲除小鼠中的内源性和逆转录病毒诱导的免疫应答，这些小鼠缺乏cGAS衔接子分子STING。我们将在HIV报告病毒感染试验中使用这些小鼠的BMDC，以确定这两种蛋白质是否在小鼠的抗逆转录病毒信号传导中发挥作用。在感染检测中加入逆转录病毒抑制剂和突变病毒将确定小鼠免疫受体感受到哪些病毒实体。在我们的SAMHD 1小鼠模型中对cGAS和STING的分析将显示新发现的传感器cGAS是否可以与在不存在SAMHD 1的情况下诱导自身免疫和抗逆转录病毒免疫应答相关联。总之，我们将利用我们已经建立的SAMHD 1基因敲除小鼠模型来分析逆转录病毒感染是如何被内在免疫感知的。

Mutations in the dNTP hydrolase SAMHD1 have been associated with the autoimmune disease Aicardi-Goutières syndrome, a hallmark of which is the spontaneous upregulation of type I interferon (IFN). In addition, SAMHD1 acts as an antiviral restriction factor that blocks the infection of HIV-1 and other retroviruses in myeloid cells and quiescent CD4+ T cells. In the absence of SAMHD1, HIV-1 induces a type I IFN response upon infection of human dendritic cells (DC). Newly produced HIV protein or the sensing of viral DNA have both been suggested to trigger this immune response to infection. It is still unclear how the virus-induced and the endogenous response in the absence of SAMHD1 are triggered and whether both responses are initiated by the same or different immune sensors. We will therefore use our recently described SAMHD1 knockout mouse model as a tool to compare the endogenous and the virus-induced immune response in the absence of SAMHD1. Mice deficient for SAMHD1 and a functional type I interferon receptor (IFNAR-/-) do not show an endogenous immune response. Therefore, we will infect mice or bone marrow-derived dendritic cells (BMDC) from SAMHD1-/- mice that are proficient or deficient for IFNAR to determine whether the endogenous immune activation acts antiviral and reveal the full antiviral potency of SAMHD1 in vitro and in vivo. Comparing the transcriptome of BMDCs from these mice upon infection will reveal whether individual transcripts are specifically upregulated in response to infection. Thus, this analysis will determine whether the endogenous and the virus-induced innate response are due to stimulation of the same pathway. Within the second aim of the study, we will further elucidate the nature of the retroviral sensor. We will clarify the role of the DNA sensor cGAS in sensing retroviral infection the absence of SAMHD1. Thus, we will analyze the endogenous and the retrovirus-induced immune response in SAMHD1/cGAS and SAMHD1/STING double knockout mice, which are deficient for the cGAS adaptor molecule STING. We will use BMDCs from these mice in HIV reporter virus infection assays to determine whether both proteins play a role in antiretroviral signaling in mice. Adding retroviral inhibitors and mutated viruses to the infection assays will determine which viral entities are sensed by the immune receptor in mice. The analysis of cGAS and STING in our SAMHD1 mouse model will show whether the newly discovered sensor cGAS can be linked to the induction of autoimmunity and an antiretroviral immune response in the absence of SAMHD1. Together, we will take advantage of our already established SAMHD1 knockout mouse model to analyze how retroviral infections are sensed by intrinsic immunity.