B7-H1/PD-1共刺激途径与病毒感染

B7-H1及其受体PD-1是共刺激分子B7-CD28家族的重要成员.B7-H1在淋巴组织及外周非淋巴组织广泛诱导性表达,PD-1则主要表达在活化的T细胞、B细胞及髓系细胞表面.B7-H1/PD-1共刺激途径主要作用是负性调节T、B细胞的免疫反应,参与维持外周组织的免疫耐受.病毒感染可以上调B7-H1及PD-1的表达,抑制病毒特异性T细胞的免疫功能,B7-H1/PD-1途径是病毒逃避免疫监视,引发慢性感染的重要通路,因而阻断B7-H1/PD-1共刺激途径能够恢复病毒特异性T细胞的功能,清除病毒感染,这对于病毒感染的免疫治疗,尤其是病毒慢性感染的免疫治疗具有重要意义.     

程序性死亡受体-1与丙型病毒性肝炎

死亡受体-1 ( PD-1)可导致病毒特异性CD8+T细胞的功能耗竭,在HCV感染过程中PD-1表达增强,阻断PD-1信号通路可恢复CD8+T细胞的免疫功能,有助于病毒清除。     

PD-1／PD-L信号通路研究进展

PD-1是近年新发现的一个负性共刺激信号分子，其配体为PD-L1和PD-L2，共属于CD28／B7家族。PD-1／PD-L通路削弱、限制和／或终止T细胞、B细胞和骨髓细胞的活化及外周炎症的效应器功能；二者相互作用导致T细胞增殖抑制和细胞因子IL-2、IL-10和IFN-γ的分泌下降，在移植免疫、自身免疫及肿瘤免疫等体系中发挥着重要作用。     

PD-1/PD-L信号通路研究进展

PD-1是近年新发现的一个负性共刺激信号分子,其配体为PD-L1和PD-L2,共属于CD28/B7家族。PD-1/PD-L通路削弱、限制和/或终止T细胞、B细胞和骨髓细胞的活化及外周炎症的效应器功能;二者相互作用导致T细胞增殖抑制和细胞因子IL-2I、L-10和IFN-γ的分泌下降,在移植免疫、自身免疫及肿瘤免疫等体系中发挥着重要作用。     

PD-1／PD-L与慢性病毒性肝炎

PD-1／PD—L信号途径在保持对机体自身成分的免疫耐受中发挥作用,同时在对外来抗原的免疫反应中发挥负向调控作用。病毒慢性持续感染、T细胞耗竭、T细胞或其它组织细胞PD-1／PD—L表达的增加常同时俘在。肝脏多种非实质细胞和肝细胞均可表达PD-L1,具有抑制T细胞活性的作用。目前,PD-1／PD—L与慢性病毒性肝炎的发病机制和治疗对策关系的研究方兴未艾。     

慢性乙型肝炎患者HBV特异性细胞毒性T细胞PD-1的表达研究

目的 检测慢性乙型病毒性肝炎患者外周血中HBV特异性CD8 细胞毒性T淋巴细胞表面细胞程序性死亡受体1(programmed cell death 1,PD-1)的表达情况.方法 采集慢性乙型肝炎患者外周血,直接离体情况下利用MHC-I-肽-五聚体技术标定HBV表位特异性细胞毒性T淋巴细胞以及荧光抗体标记细胞表面PD-1分子,经流式细胞仪检测分析.结果 在慢性乙型肝炎患者,HBV核心抗原18-27特异性CTL表达PD-1上调,达(79.0±12.5)%,显著高于总CD8 T细胞(27.7±14.8)%,以及CMV特异性CTL(20.6±5.9)%.结论 慢性乙肝患者HBV特异性CTL高表达PD-1分子,可能与慢性乙肝患者HBV特异性CTL功能低下密切相关.     

HIV-1感染过程中CD8~+T细胞PD-1水平增高与其活化状态正相关

目的分析人类免疫缺陷病毒1型(HIV-1)感染者CD8+T细胞程序性死亡蛋白1(PD-1)、CD38、人白细胞抗原DR(HLA-DR)及KI-67抗原(ki67)的表达水平,探讨HIV-1感染过程中CD8~+T细胞PD-1表达水平与免疫活化和免疫耗竭的关系及意义。方法收集HIV-1感染者87例,健康志愿者22例,密度梯度法分离外周血单个核细胞;采用流式细胞术分析其CD8+T细胞PD-1、CD38、HLA-DR、ki67的表达水平;观察用抗PD-L1 m Ab阻断PD-1/PD-L1通路后CD8~+T细胞分泌肿瘤坏死因子α(TNF-α)、γ干扰素(IFN-γ)的水平变化。结果 HIV-1感染者CD8~+T细胞PD-1表达水平显著高于健康对照组;CD8~+T细胞PD-1水平与病毒载量呈正相关,与CD4~+T细胞数呈负相关;CD8~+T细胞PD-1与CD38、HLA-DR表达呈正相关,与ki67表达无相关性;体外阻断PD-1/PD-L1通路后TNF-α、IFN-γ的表达量增加。结论 HIV-1感染者外周血CD8~+T细胞PD-1表达增加;PD-1过表达与HIV感染过程中CD8~+T细胞功能受抑、免疫耗竭及疾病进程相关;体外阻断PD-1/PD-L1通路可恢复CD8~+T细胞功能。     

PD-1在慢性病毒感染性疾病中的研究进展

PD-1是1992年发现的免疫共刺激分子。它有两个配体:PD-L1和PD-L2。PD-L1分布很广,PD-L2主要局限于抗原递呈细胞。近年来,发现PD-1在淋巴细胞性脉络丛炎病毒感染、HIV感染、HBV和HCV感染的慢性化过程中明显升高,同时相关的特异性T细胞减少,功能降低。若阻断该途径,则可以明显改善T细胞的功能。     

miR-124靶向镁转运蛋白1调控活化后人T细胞功能耗竭

目的研究miR-124靶向镁转运蛋白1(MagT1)可否调控活化后T细胞功能耗竭。方法 1)分离外周血单个核细胞,用IFN-γ、IL-2、抗-CD3抗体、抗-CD28抗体和IL-1α活化T细胞;流式细胞仪检测T细胞活化标记分子CD25和CD69所占的比例。2)构建miR-124/miR-124 sponge慢病毒载体;包装慢病毒后感染活化T细胞,用RT-qPCR检测感染后T细胞内miR-124和MagT1基因表达。3)生物信息学分析miR-124与MagT1的靶向位点,并用双荧光素酶报告基因系统鉴定。4)Western blot法检测慢病毒感染前后T细胞MagT1和PD-1蛋白水平。5)CCK8法检测慢病毒感染前后T细胞增殖能力;ELISA法检测细胞T分泌细胞因子TNF-α和TGF-β的能力。结果流式细胞仪检测表明T细胞活化成功。RT-qPCR检测表明慢病毒构建成功,miR-124/miR-124 sponge载体分别显著上调或下调miR-124的表达(P0.01)。双荧光素酶报告基因系统证实miR-124靶向MagT1 3′UTR并抑制其表达。Western blot表明miR-124过表达组MagT1蛋白水平低于对照组(P0.05),PD-1蛋白水平高于对照组(P0.05),抑制miR-124后,MagT1蛋白水平高于对照组(P0.05),PD-1蛋白水平低于对照组(P0.05)。miR-124过表达使T细胞增殖能力和分泌TNF-α能力显著降低,而抑制miR-124使T细胞增殖能力和分泌TGF-β能力显著升高(P0.01)。结论 miR-124可以负向调节靶基因MagT1的表达,并对活化后T细胞功能耗竭具有重要的调节作用。     

PD-1/PD-L1在系统性红斑狼疮患者外周血表达水平及其临床意义

本研究旨在检测系统性红斑狼疮(SLE)患者外周血CD4~+T细胞表面PD-1和B细胞表面PD-L1分子的表达并探索其临床意义。采用流式细胞术检测SLE患者及健康对照外周血CD4~+T细胞上PD-1分子及B细胞上PD-L1分子的表达,并分析其与SLE临床指标的相关性。结果显示,SLE患者外周CD4~+T细胞表面PD-1分子及B细胞上PD-L1分子的表达均明显高于健康对照组(均P0.05),且SLE患者CD4~+T细胞上PD-1分子的表达水平与血清Anti-dsDNA的含量及SLEDAI评分呈正相关(均P0.05),B细胞上PD-L1分子的表达水平与血清dsDNA水平呈正相关(P0.05)。上述结果表明,SLE患者外周血CD4+T细胞上PD-1分子及B细胞上PD-L1分子均发生上调,并与SLE病程和自身抗体水平呈现正相关,提示分别表达于T细胞和B细胞表面的PD-1/PD-L1分子,通过相互作用参与SLE的致病和发展过程。     

PD-1 upregulation is associated with HBV-specific T cell dysfunction in chronic hepatitis B patients

Programmed death-1 (PD-1) is demonstrated to have an increased expression on antigen-specific T cells during chronic virus infections, and the blockage of PD-1/PD-ligand (PD-L1) pathway could restore the function of exhausted T cells. We measured the PD-1 expression levels on HBV-specific CD8 T cells and investigated the role of PD-1/PD-L1 pathway in T-cell responses of patients with different HBV infection statuses. Compared to the patients with convalescent acute hepatitis B, PD-1 expression on total CD8 T cells from chronic hepatitis B (CHB) patients was significantly upregulated, especially on the HBV pentamer-positive CD8 T cells. And PD-L1, but not PD-L2, was also significantly upregulated on PBMC from CHB patients. In CHB patients, HBV-specific T cells and cellular proliferation could be observed under the recombinant HBV-Ag stimulation in vitro, and blockade of PD-1 pathway significantly enhanced the IFN-gamma production and cellular proliferation of PBMC. Furthermore, PD-1 expression level on HBV-pentamers positive CD8 T cells was positively associated with plasma viral load in CHB patients. Thus, PD-1 upregulation on HBV-specific CD8 T cells is engaged in the dysfunction of T cells and high viraemia in CHB patients, and the antiviral T-cell responses could be improved by the blockade of this inhibitory PD-1/PD-L1 pathway.     

A new therapeutic strategy to control HIV? The PD1 molecule and its role in inhibiting cellular immune responses

CD8+ T cells are crucial in protecting against viral infections by secreting antiviral factors and lysing infected cells. The loss of these functions is a hallmark of various chronic viral infections. In HIV chronic infection, CD8+ T cells develop this exhausted phenotype and their protection capacities diminish. Recently, it has been shown that a co-inhibitory molecule called PD-1 plays an important role on this exhausted phenotype. These findings open up the possibility of research targeted to develop therapeutic interventions that may restore CD8+ T cell function in chronic HIV infection.     

Emerging concepts in PD-1 checkpoint biology

The PD-1 pathway is a cornerstone in immune regulation. While the PD-1 pathway has received considerable attention for its role in contributing to the maintenance of T cell exhaustion in chronic infection and cancer, the PD-1 pathway plays diverse roles in regulating host immunity beyond T cell exhaustion. Here, we discuss emerging concepts in the PD-1 pathway, including (1) the impact of PD-1 inhibitors on diverse T cell differentiation states including effector and memory T cell development during acute infection, as well as T cell exhaustion during chronic infection and cancer, (2) the role of PD-1 in regulating Treg cells, NK cells, and ILCs, and (3) the functions of PD-L1/B7-1 and PD-L2/RGMb/neogenin interactions. We then discuss the emerging use of neoadjuvant PD-1 blockade in the treatment of early-stage cancers and how the timing of PD-1 blockade may improve clinical outcomes. The diverse binding partners of PD-1 and its associated ligands, broad expression patterns of the receptors and ligands, differential impact of PD-1 modulation on cells depending on location and state of differentiation, and timing of PD-1 blockade add additional layers of complexity to the PD-1 pathway, and are important considerations for improving the efficacy and safety of PD-1 pathway therapeutics.     

Programmed death-1 (PD-1)/PD-1 ligand pathway-mediated immune responses against human T-lymphotropic virus type 1 (HTLV-1) in HTLV-1-associated myelopathy/tropical spastic paraparesis and carriers with autoimmune disorders

Human T-lymphotropic virus-1 (HTLV-1) causes HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T-cell leukemia-lymphoma in individuals with dysfunctional immune responses. In this study, to characterize the HTLV-1-specific cytotoxic T lymphocyte (CTL) populations in asymptomatic HTLV-1 carriers (ACs), HAM/TSP patients, and carriers with autoimmune disorders (CAIDs), we examined the role of programmed death-1 and its ligand (PD-1/PD-L1) in HTLV-1-specific CTL functions using an HTLV-1 Tax/HLA-A*0201 tetramer and an HTLV-1 Tax/HLA-A*2402 tetramer. Interestingly, the percentage of HTLV-1 Tax301-309/HLA-A*2402 tetramer(+)CD8(+) cells expressing PD-1 in ACs was significantly higher than the percentage of HTLV-1 Tax11-19/HLA-A*0201 tetramer(+)CD8(+) cells expressing PD-1. PD-1 expression was significantly downregulated on HTLV-1-specific CTLs in HAM/TSP compared with ACs. PD-L1 expression was observed in a small proportion of unstimulated lymphocytes from ACs and was greater in ACs than in HAM/TSP and CAIDs after short-term culture. Furthermore, CTL degranulation was impaired in HAM/TSP, whereas anti-PD-L1 blockade significantly increased CTL function in ACs. Downregulation of PD-1 on HTLV-1-specific CTLs and loss of PD-L1 expression in HAM/TSP and CAIDs, along with impaired function of HTLV-1-specific CTLs in HAM/TSP, may underlie the apparently dysfunctional immune response against HTLV-1.     

PD-L2 is a second ligand for PD-1 and inhibits T cell activation

Programmed death I (PD-I)-deficient mice develop a variety of autoimmune-like diseases, which suggests that this immunoinhibitory receptor plays an important role in tolerance. We identify here PD-1 ligand 2 (PD-L2) as a second ligand for PD-1 and compare the function and expression of PD-L1 and PD-L2. Engagement of PD-1 by PD-L2 dramatically inhibits T cell receptor (TCR)-mediated proliferation and cytokine production by CD4+ T cells. At low antigen concentrations, PD-L2-PD-1 interactions inhibit strong B7-CD28 signals. In contrast, at high antigen concentrations, PD-L2-PD-1 interactions reduce cytokine production but do not inhibit T cell proliferation. PD-L-PD-1 interactions lead to cell cycle arrest in G0/G1 but do not increase cell death. In addition, ligation of PD-1 + TCR leads to rapid phosphorylation of SHP-2, as compared to TCR ligation alone. PD-L expression was up-regulated on antigen-presenting cells by interferon gamma treatment and was also present on some normal tissues and tumor cell lines. Taken together, these studies show overlapping functions of PD-L1 and PD-L2 and indicate a key role for the PD-L-PD-1 pathway in regulatingT cell responses.     

Expression and purification of soluble human programmed death-1 in Escherichia coli

Programmed death-1 （PD-1）, a member of CD28 family, is able to negatively regulate the TCR complex-initiated signaling by interacting with its cognate ligands （PD-L1 and/or PD-L2）. PD-1/PD-L1 pathway plays an important role in down-regulating the effective phase of adaptive immune responses and the blockade of this pathway has been proved to enhance antiviral and antitumoral immunity, suggesting that it might be a potential target for the development of therapies to improve T cell responses in patients with virus infections or malignancies. In present study, the extracellular domain of human PD-1 with a carboxyl terminal His-tag （designated as sPD-1） was expressed as inclusion bodies in Escherichia coll. The product was on-column refolded, purified by immobilized metal affinity chromatography, and characterized by Western blotting. Furthermore, the soluble PD-1 with high purity possessed specific binding activity with its cognate ligand PD-L1, and the dissociation constant was 0.43 nmol/L as determined by Scatchard plot analysis. These results suggest that refolded sPD-1 from prokaryotic cells may be of therapeutic interest in enhancing antivirus and antitumoral immune responses.     

Increased expression of programmed death (PD)‐1 and its ligand PD‐L1 correlates with impaired cell‐mediated immunity in high‐risk human papillomavirus‐related cervical intraepithelial neoplasia

Impaired local cellular immunity contributes to the pathogenesis of persistent high-risk human papillomavirus (HR-HPV) infection and related cervical intraepithelial neoplasia (CIN), but the underlying molecular mechanisms remain unclear. Recently, the programmed death 1/programmed death 1 ligand (PD-1/PD-L1; CD279/CD274) pathway was demonstrated to play a critical role in attenuating T-cell responses and promoting T-cell tolerance during chronic viral infections. In this study, we examined the expression of PD-1 and PD-L1 on cervical T cells and dendritic cells (DCs), respectively, from 40 women who were HR-HPV-negative (−) or HR-HPV-positive (+) with CIN grades 0, I and II–III. We also measured interferon-γ, interleukin-12 (IL-12) and IL-10 in cervical exudates. The most common HPV type was HPV 16, followed by HPV 18, 33, 51 and 58. PD-1 and PD-L1 expression on cervical T cells and DCs, respectively, was associated with HR-HPV positivity and increased in parallel with increasing CIN grade. The opposite pattern was observed for CD80 and CD86 expression on DCs, which decreased in HR-HPV(+) patients in parallel with increasing CIN grade. Similarly, reduced levels of the T helper type 1 cytokines interferon-γ and IL-12 and increased levels of the T helper type 2 cytokine IL-10 in cervical exudates correlated with HR-HPV positivity and CIN grade. Our results suggest that up-regulation of the inhibitory PD-1/PD-L1 pathway may negatively regulate cervical cell-mediated immunity to HPV and contribute to the progression of HR-HPV-related CIN. These results may aid in the development of PD-1/PD-L1 pathway-based strategies for immunotherapy of HR-HPV-related CIN.     

The function of programmed cell death 1 and its ligands in regulating autoimmunity and infection

The programmed cell death 1 (PD-1) surface receptor binds to two ligands, PD-L1 and PD-L2. Studies have shown that PD-1-PD-L interactions control the induction and maintenance of peripheral T cell tolerance and indicate a previously unknown function for PD-L1 on nonhematopoietic cells in protecting tissues from autoimmune attack. PD-1 and its ligands have also been exploited by a variety of microorganisms to attenuate antimicrobial immunity and facilitate chronic infection. Here we examine the functions of PD-1 and its ligands in regulating antimicrobial and self-reactive T cell responses and discuss the therapeutic potential of manipulating this pathway.