Vpu inhibits NK cell function through down regulation of NTB-A

描述(申请人提供)：自然杀伤(NK)细胞是天生的淋巴细胞，在对病毒的免疫监控中至关重要。然而，NK细胞无法控制HIV-1。尽管HIV-1Nef能够下调NK细胞抑制受体的配体--人类白细胞抗原-A和-B，但NK细胞并不能有效地裂解HIV感染的细胞。此外，HIV-1VPR诱导配体ULBP-1和-2与激活受体NKG2D结合。Nef和Vpr的作用足以激活NK细胞，但不足以触发NK细胞释放其细胞溶解功能 颗粒。NK细胞要脱颗粒，需要两种受体NKG2D和NTB-A的结合。正常情况下，NK细胞上的NTB-A是由CD4T细胞上的NTB-A触发的。然而，HIV-1VPU能够下调感染细胞表面的NTB-A，并在这样做的过程中阻止有反应的NK细胞脱颗粒。因此，VPU保护受感染的细胞免受NK细胞的裂解。为了了解VPU对NTB-A的调节及其对NK细胞杀伤反应的影响，我们将：1)确定VPU通过NTB-A下调抑制NK细胞杀伤反应的机制；2)确定VPU如何下调NTB-A；3)确定来自不同亚型和组的HIV-1和SIV毒株的VPU是否能够以及如何下调NTB-A。在第一个目标中，我们将检验这样的假设，即NTB-A在HIV感染的靶细胞上的VPU下调阻止了来自NTB-A的特定细胞内信号在NK细胞上诱导下游信号事件的能力，该信号事件涉及促进裂解颗粒的释放。在目标1中，我们还将检查NK细胞激活受体KIR3DS1的激活配体是否能够在NTB-A下调的背景下触发脱颗粒。在第二个目标中，我们将检验VPU的细胞质尾巴干扰宿主细胞蛋白的假设，宿主细胞蛋白参与将NTB-A从跨高尔基网络运输到质膜。在第二个目标中，我们还将确定VPU的跨膜(TM)部分是否以及如何与NTB-A的TM部分相互作用。在最后一个目标中，我们将检验这一假设，即来自特定HIV-1亚型和群体的VPU在调节NTB-A方面具有不同的效率。此外，我们将确定VPU对NTB-A的下调是否仅限于HIV-1，或者SIV VPU是否也下调猿猴和人类NTB-A。对这些机制的了解无疑将导致旨在恢复HIV-1感染期间NK间隔的有效性的新的治疗干预措施。 与公共卫生相关：该项目将确定艾滋病毒如何逃避被称为自然杀伤细胞的免疫细胞。自然杀伤细胞是对抗艾滋病毒第一道防线的一部分。 感染。这项研究的结果将为艾滋病毒通过早期免疫反应避免检测和破坏的机制提供见解。这些见解将为提高免疫系统控制艾滋病毒感染的能力的治疗策略指明方向。

DESCRIPTION (provided by applicant): Natural killer (NK) cells are innate lymphocytes that are crucial in the immune surveillance against viruses. However, NK cells fail to control HIV-1. NK cells do not effectively lyse HIV-infected cells despite the ability of HIV-1 Nef to down modulate the ligands for NK cell inhibitory receptors, HLA-A and -B. Moreover, HIV-1 Vpr induces ligands, ULBP-1 and -2, to the activation receptor, NKG2D. The actions of Nef and Vpr are sufficient to activate NK cells but insufficient to trigger NK cells to release their cytolytic granules. For NK cells to degranulate they require the engagement of two receptors, NKG2D and NTB-A. Under normal conditions, NTB-A on NK cells is triggered by NTB-A on CD4+ T-cells. However, HIV-1 Vpu is able to down modulate NTB-A from the infected cells surface and in doing so prevents the responding NK cells from degranulating. Thus, Vpu protects the infected cell from lysis by NK cells. In order to understand Vpu's modulation of NTB-A and its consequence on the NK cell cytolytic response we will: 1) determine the mechanism by which Vpu, through NTB-A down modulation, suppresses NK cytolytic response, 2) determine how Vpu down modulates NTB-A and 3) determine whether and how Vpu from various subtypes and groups of HIV-1 and SIV strains are able to down modulate NTB-A. In the first aim, we will test the hypothesis that Vpu down modulation of NTB-A on HIV-infected target cells prevents the ability of specific intracellular signals originating from NTB-A on NK cells from inducing down stream signaling events involved in facilitating the release of lytic granules. In Aim 1 we will alo examine whether the activation ligands to NK cell activation receptor, KIR3DS1 is able to trigger degranulation in the context of NTB-A down modulation. In the second aim, we will test the hypothesis that Vpu's cytoplasmic tail interferes with host cell proteins that are involved in transporting NTB-A from the trans-Golgi network to the plasma membrane. In the second Aim we will also determine whether and how the transmembrane (TM) portion of Vpu interacts with the TM portion of NTB-A. In the last aim, we will test the hypothesis that Vpu from specific HIV-1 subtypes and groups will have different efficiencies in modulating NTB-A. Moreover, we will determine whether Vpu's down modulation of NTB-A is limited to HIV-1 or whether SIV Vpu down modulates simian and human NTB-A as well. Knowledge of these mechanisms will undoubtedly lead to novel therapeutic interventions aimed at restoring the effectiveness of the NK compartment during HIV- 1 infection. PUBLIC HEALTH RELEVANCE: This project will determine how HIV evades immune cells called natural killer cells. Natural killer cells are part of the first line of defense against HIV infection. The results from this study will provide insights on the mechanisms by which HIV avoids detection and destruction by the early immune response. These insights will point the way towards treatment strategies that will enhance the immune system's ability to control HIV infection.