Mechanism of cell-associated HIV-1 transmission

描述（由申请人提供）：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）是病毒传播到初始宿主后早期被病毒靶向的初始细胞类型之一，在体内建立多产的病毒感染和HIV-1传播中起关键作用。虽然dc本身总是被感染，但dc捕获的HIV-1颗粒有效地传播到CD4+ T细胞，这是HIV-1反式感染的一种机制。尽管研究广泛，但HIV-1颗粒入侵dc和逃避细胞内防御的机制仍然难以捉摸。许多树突状细胞特异性HIV-1附着因子已被提出以HIV-1包膜gp120依赖的方式解释dc介导的病毒捕获。但是，在dc中靶向中和任何或所有这些先前提出的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向T细胞的传播，这表明dc中存在不依赖gp120的病毒捕获机制。我们认为HIV-1可以通过在病毒颗粒膜的脂质双分子层中表达的鞘糖脂结合树突状细胞。该项目的主要目标之一是确定以糖鞘脂依赖的方式捕获HIV-1颗粒的受体。基于我们的初步发现，我们将重点关注dc表面表达的gpi连接蛋白。我们将在这一蛋白质亚群中确定假定的受体，其表达在单核细胞分化为dc时被诱导，并在dc成熟时显着增强。我们将定义当gsl依赖性HIV与这种假定的受体结合时，dc内HIV-1颗粒进入内吞区室的性质，以及随后的细胞内运输机制，该机制将捕获的病毒颗粒从溶酶体降解途径中移除。最后，我们将比较和对比病毒颗粒在获得gp120依赖的附着因子和gsl依赖的附着因子(s)时的命运，并确定病毒颗粒膜中存在的gsl是否对靶向HIV-1颗粒到dc介导的T细胞转感染途径至关重要。了解这种发生的机制将为HIV-树突状细胞相互作用途径的关键步骤提供信息，并为树突状细胞在HIV-1发病机制中的作用提供见解。此外，阐明HIV-1粘附于dc的这一机制可能为设计特异性靶向HIV-1生命周期早期阶段的抗病毒药物提供新的靶点。

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.