Mechanisms of SAMHD1-mediated HIV-1 restriction in dendritic cells

描述(申请人提供)：免疫激活是HIV-1在体内复制的驱动力，它促进了病毒在靶细胞的感染，并从根本上促进了艾滋病的发病。髓系细胞，包括单核细胞、树突状细胞(DC)和巨噬细胞，在抵抗病毒感染的先天免疫中发挥着关键作用。我们的长期目标是确定在HIV-1感染期间调节髓系细胞免疫激活的机制。SAMHD1是新近发现的一种髓系细胞HIV-1限制性因子。SAMHD1是一种参与 先天免疫，已被认为是干扰素反应的负调节因子。然而，SAMHD1在调节髓系细胞免疫激活中的作用仍不清楚。SAMHD1介导的HIV-1抑制DC的分子机制尚不完全清楚。在本项目中，我们旨在研究SAMHD1介导的HIV-1在原代DC中的限制机制以及SAMHD1在调节DC免疫激活中的作用。在我们的初步研究中，我们观察到HIV-1感染DC显著上调了一些早期促炎细胞因子的释放。有趣的是，我们发现HIV-1感染DC导致SAMHD1从细胞核移位到细胞质。我们的中心假设是：HIV-1感染DC触发SAMHD1细胞质易位，这对DC的HIV-1限制和免疫抑制是重要的。因此，SAMHD1在DC中对HIV-1的限制负面调节了DC介导的CD4T细胞的激活和HIV-1的传播，这为HIV-1的传播建立了一个不那么宽容的环境。我们提出了两个具体的目标来检验这些新的假设。目的1.研究SAMHD1在抑制HIV-1感染过程中树突状细胞(DC)免疫激活中的作用；2.明确SAMHD1介导的DC抑制HIV-1的机制。我们的研究将揭示SAMHD1在调节HIV-1感染期间髓系树突状细胞免疫激活中的独特作用，并明确SAMHD1介导的原代DC限制HIV-1的确切机制。完成所提出的研究还将阐明SAMHD1负面调节DC介导的HIV-1反式感染和CD4T细胞激活的机制。总体而言，我们的结果将为了解髓系树突状细胞对HIV-1感染的内在免疫提供新的见解，这可以帮助我们开发新的干预措施来阻断HIV-1感染和传播。

DESCRIPTION (provided by applicant): Immune activation is the driving force of HIV-1 replication in vivo, which facilitates viral infection in target cells and fundamentally contribute to AIDS pathogenesis. Myeloid cells, including monocytes, dendritic cells (DCs) and macrophages, play a critical role in innate immunity against viral infection. Our long-term goal is to define th mechanisms regulating immune activation of myeloid cells during HIV-1 infection. SAMHD1 is a recently identified HIV-1 restriction factor in myeloid cells. SAMHD1 a nuclear protein involved in innate immunity and has been proposed to act as a negative regulator of the interferon response. However, the role of SAMHD1 in regulating immune activation of myeloid cells remains unknown. The molecular mechanisms of SAMHD1-mediated HIV-1 restriction in DCs are not fully understood. In this project, we aim to study the mechanisms of SAMHD1-mediated HIV-1 restriction in primary DCs and the role of SAMHD1 in regulating immune activation of DCs. In our preliminary studies, we observed that HIV-1 infection of DCs significantly up-regulated the release of some early pro-inflammatory cytokines. Intriguingly, we found that HIV-1 infection of DCs resulted in the translocation of SAMHD1 from the nucleus to the cytoplasm. Our central hypotheses are: HIV-1 infection of DCs triggers SAMHD1 cytoplasmic translocation, which is important for HIV-1 restriction and immune suppression of DCs. As a result, HIV-1 restriction by SAMHD1 in DCs negatively regulates DC-mediated activation of CD4+ T-cells and HIV-1 transmission, which sets up a less permissive environment for HIV-1 spreading. We propose two specific aims to test these novel hypotheses. Aim 1. To examine the role of SAMHD1 in suppression of immune activation of DCs during HIV-1 infection; and Aim 2. To define the mechanisms of SAMHD1-mediated HIV-1 restriction in DCs. Our proposed studies will reveal the unique role of SAMHD1 in regulating immune activation of myeloid DCs during HIV-1 infection and define the precise mechanisms of SAMHD1-mediated HIV-1 restriction in primary DCs. Accomplishing the proposed studies will also elucidate the mechanisms by which SAMHD1 negatively regulates DC-mediated HIV-1 trans-infection and activation of CD4+ T-cells. Overall, our results will provide new insights into intrinsic immunity against HIV-1 infectin in myeloid DCs, which can help us to develop novel interventions to block HIV-1 infection and transmission.