Mechanism of cell-associated HIV-1 transmission

描述(申请人提供)：人类免疫缺陷病毒1型(HIV-1)是人类艾滋病的病原体。树突状细胞(DC)是病毒传播到幼稚宿主后早期被病毒靶向的初始细胞类型之一，在建立生产性病毒感染和在体内传播HIV-1方面发挥关键作用。虽然DC本身总是被感染的，但DC捕获的HIV-1颗粒会有效地传播到CD4+T细胞，这是HIV-1反式感染的一种机制。尽管进行了广泛的研究，但HIV-1颗粒侵入DC并逃避细胞内防御的机制仍然难以捉摸。一些树突状细胞特异性的HIV-1附着因子被提出来解释DC介导的HIV-1包膜gp120依赖的病毒捕获。但是，靶向中和任何或所有这些先前提出的DC中的HIV-1附着因子，既不能抑制病毒捕获，也不能抑制捕获的HIV-1颗粒从DC到T细胞的传播，提示DC中存在gp120非依赖的病毒捕获机制(S)。我们认为HIV-1可以通过表达在病毒颗粒膜脂双层中的糖鞘糖脂与DC结合。该项目的主要目标之一是确定以糖鞘糖脂依赖的方式捕获HIV-1颗粒的受体。根据我们的初步发现，我们将重点关注DC表面表达的GPI连接蛋白。我们将在这一亚组蛋白中确定其可能的受体，其表达在从单核细胞分化为DC时被诱导，并且在DC成熟时其表达显著增强。我们将确定树突状细胞内HIV-1颗粒在依赖GSL的HIV与这一假定的受体结合时进入的内细胞室的性质，以及随后以捕获的病毒颗粒为靶点远离溶酶体降解途径的细胞内转运机制。最后，我们将比较和对比病毒颗粒在访问依赖gp120和依赖GSL的附着因子(S)时的命运，并确定存在于病毒颗粒膜上的GSLs是否对于将HIV-1颗粒靶向DC介导的T细胞感染途径至关重要。了解这种情况发生的机制将提供有关HIV-树突状细胞相互作用途径中的关键步骤的信息，并有助于深入了解树突状细胞在HIV-1发病机制中的作用。此外，阐明HIV-1与树突状细胞结合的这种机制可能为针对HIV-1生命周期早期阶段的抗病毒药物的设计提供新的靶点。 公共卫生相关性：该项目的目的是确定人类免疫缺陷病毒1型(S)被树突状细胞捕获的机制，这是确定病毒在体内感染和传播的关键步骤。对以非环境依赖、糖鞘糖脂依赖的方式捕获HIV-1并导致树突状细胞内隔离HIV感染性的受体的详细了解是HIV-1发病机制中的关键一步，并可能导致抗病毒药物的开发，如微生物剂，以防止HIV-1传播到幼稚宿主。

DESCRIPTION (provided by applicant): Human immunodeficiency virus type 1 (HIV-1) is the causative agent of AIDS in humans. Dendritic cells (DCs) are one of the initial cell types that are targeted by the virus early following virus transmission to a naive host, and play a critical role in the establishment of productive virus infection and dissemination of HIV-1 in vivo. While DCs themselves are invariably infected, HIV-1 particles captured by DCs are efficiently transmitted to CD4+ T cells, a mechanism of HIV-1 trans infection. Though studied extensively, the mechanisms by which HIV-1 particles invade DCs and evade intracellular defenses have remained elusive. A number of dendritic cell-specific HIV-1 attachment factors have been proposed to account for DC-mediated virus capture in a HIV-1 envelope gp120 dependent manner. But targeted neutralization of any or all of these previously proposed HIV-1 attachment factors in DCs, fails neither to inhibit virus capture nor transmission of captured HIV-1 particles from DCs to T cells, suggesting the existence of gp120-independent virus capture mechanism(s) in DCs. We propose that HIV-1 can bind DCs using glycosphingolipids expressed in the lipid bilayer of the virus particle membrane. One of the major goals of this project is to identify the receptor that captures HIV-1 particles in a glycosphingolipid-dependent manner. Based on our preliminary findings, we will focus our attentions on GPI-linked proteins expressed on DC-surface. We will identify the putative receptor amongst this subset of proteins whose expression is induced upon differentiation from monocytes into DCs and whose expression is significantly enhanced upon maturation of DCs. We will define the nature of the endocytic compartment accessed by HIV-1 particles within DCs upon GSL-dependent HIV binding to this putative receptor and the ensuing intracellular trafficking mechanism that targets captured virus particles away from lysosomal degradation pathways. Finally, we will compare and contrast the fate of virus particles upon accessing a gp120-dependent versus GSL-dependent attachment factor(s) and determine if GSLs present in the virus particle membrane are crucial for targeting HIV-1 particles to the DC-mediated T cell trans infection pathway. Understanding the mechanism by which this occurs will provide information about a key step in the HIV - dendritic cell interaction pathway, and provide insights into the role of dendritic cells in HIV-1 pathogenesis. Furthermore, elucidation of this mechanism of HIV-1 attachment to DCs might provide novel targets for design of anti-virals that specifically target an early step in the HIV-1 life cycle. PUBLIC HEALTH RELEVANCE: The aim of this project is to identify the mechanism(s) by which human immunodeficiency virus type 1 (HIV-1) is captured by dendritic cells, a critical step in the establishment of infection and dissemination of virus in vivo. A detailed understanding of the receptor that captures HIV-1 in a Env-independent, glycosphingolipid-dependent manner, and results in sequestration of HIV infectivity within DCs is a crucial step in HIV-1 pathogenesis, and could lead to the development of anti-virals such as microbicides that prevent transmission of HIV-1 to a naive host.