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

描述（由申请人提供）：自然杀伤（NK）细胞是先天淋巴细胞，在对病毒的免疫监视中至关重要。然而，NK细胞不能控制HIV-1。尽管HIV-1 Nef能够下调NK细胞抑制性受体HLA-A和-B的配体，但NK细胞不能有效地裂解hiv感染的细胞。此外，HIV-1 Vpr诱导配体ULBP-1和-2到激活受体NKG2D。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作用

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.