Intrinsic immune sensing of retroviral infections in SAMHD1 knockout mice

DNTP水解酶SAMHD1的突变与自身免疫性疾病艾卡迪-古蒂埃综合征有关，该综合征的一个特征是I型干扰素(干扰素)的自发上调。此外，SAMHD1作为一种抗病毒限制因子，可以阻止HIV-1和其他逆转录病毒在髓系细胞和静止的CD4T细胞中的感染。在没有SAMHD1的情况下，HIV-1在感染人树突状细胞(DC)时诱导I型干扰素反应。新产生的HIV蛋白或对病毒DNA的感知都被认为是触发对感染的免疫反应。目前尚不清楚病毒诱导的反应和在没有SAMHD1的情况下内源性反应是如何触发的，以及这两种反应是由相同还是不同的免疫感受器启动的。因此，我们将使用我们最近描述的SAMHD1基因敲除小鼠模型作为工具，在没有SAMHD1的情况下比较内源性和病毒诱导的免疫反应。缺乏SAMHD1和功能性I型干扰素受体(IFNAR-/-)的小鼠不会出现内源性免疫反应。因此，我们将感染SAMHD1-/-小鼠或缺乏IFNAR的SAMHD1-/-小鼠的骨髓来源的树突状细胞(BMDC)，以确定内源性免疫激活是否具有抗病毒作用，并在体外和体内揭示SAMHD1的全部抗病毒效力。比较这些小鼠感染时BMDCs的转录组，将揭示单个转录是否在感染时特异性上调。因此，这一分析将确定内源性和病毒诱导的先天反应是否源于同一途径的刺激。在这项研究的第二个目标中，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SAMHD1缺失的逆转录病毒感染中的作用。因此，我们将分析缺乏cGAS接头分子的SAMHD1/cGAS和SAMHD1/STING双基因敲除小鼠的内源性和逆转录病毒诱导的免疫应答。我们将使用这些小鼠的BMDCs进行HIV报告病毒感染试验，以确定这两种蛋白是否在小鼠的抗逆转录病毒信号中发挥作用。在感染检测中加入逆转录病毒抑制剂和变异病毒将确定哪些病毒实体被小鼠的免疫受体感知到。在我们的SAMHD1小鼠模型中对cGAS和STING的分析将表明，新发现的传感器cGAS是否与在没有SAMHD1的情况下诱导自身免疫和抗逆转录病毒免疫反应有关。我们将共同利用我们已经建立的SAMHD1基因敲除小鼠模型来分析逆转录病毒感染是如何通过内在免疫来感知的。

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.