Role of IL-7 in Human Immunodeficiency Virus Infection

IL-7 在人类免疫缺陷病毒感染中的作用

• 批准号: 8946392
• 负责人: paolo lusso
• 金额: $ 29.16万
• 依托单位: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8946392
• 关键词: Acquired Immunodeficiency Syndrome; Acute; Affect; Aftercare; Animals; Apoptosis; Autologous; Binding; CD4 Positive T Lymphocytes; CD8B1 gene; Cell Cycle; Cell Proliferation; Chronic; Clinical Trials; Cytokine Network Pathway; Cytokine Receptors; Data; Disease; Exposure to; Fostering; Genes; Gut associated lymphoid tissue; HIV; HIV Infections; HIV-1; Homing; Human; Immune; Immune response; Immunologic Deficiency Syndromes; Immunologics; Individual; Infection; Injection of therapeutic agent; Integrins; Interleukin 7 Receptor; Interleukin-7; Intestines; Investigation; Ionomycin; Kinetics; Ligands; Link; Lymphoid Tissue; Lymphopenia; Macaca; Macaca mulatta; Malignant Neoplasms; Memory; Messenger RNA; Microarray Analysis; Modeling; Molecular; Mus; Pathway interactions; Patients; Peripheral; Phase; Phenotype; Phorbol Esters; Physiological; Placebos; Plasma; Population; Predisposition; Process; Proliferating; Research; Role; SIV; Signal Pathway; Small Interfering RNA; Staging; Structure of aggregated lymphoid follicle of small intestine; Surface; T-Lymphocyte; TNF gene; TNFRSF6 gene; Time; Tissues; Transcript; Up-Regulation; Validation; Viremia; Virus Diseases; Virus Replication; cytokine; human subject; immunoregulation; in vivo; in vivo Model; insight; knock-down; lymph nodes; memory CD4 T lymphocyte; model design; programs; receptor expression; reconstitution; research clinical testing; research study; response

The homeostatic cytokine IL-7 is currently under clinical investigation as a potential immune-reconstitution agent in various forms of immunodeficiency, including HIV infection and cancer. We previously demonstrated that IL-7, in the absence of any concomitant stimulation, potently and selectively induces the expression of the principal gut-homing integrin, a4b7, in both CD4+ and CD8+ T cells. We found that this effect: i) is specific for T cells and more marked on the nave subpopulation; ii) is rapidly induced upon IL-7 treatment; iii) requires supra-homeostatic concentrations of IL-7 (those that are typically reached under conditions of lymphopenia); iv) is uncoupled from the expression of classic markers of cellular activation; and v) is associated with the functional activation of the integrin, as indicated by an increased binding activity for its natural ligand, MAdCAM. Investigation of the molecular mechanisms of a4b7 induction by IL-7 revealed the involvement of both major signaling pathways linked to stimulation of the IL-7 receptor, i.e., the JAK/STAT and PI3K/Akt pathways. Induction of a4b7 by IL-7 was also confirmed in vivo, both in HIV-infected human subjects and in SIV-infected macaques treated with IL-7. Of note, we found that induction of a4b7 by IL-7 occurs predominantly in phenotypically naive T cells, which concomitantly acquired a memory-like phenotype, as shown by upregulation of CD95 expression and secretion of TNF-a; upon stimulation with phorbol esters and ionomycin, despite an unaltered expression of CD45RA and CD45RO. This memory-like "masquerade" of T cells is similar to that previously documented in vivo in naive T cells of mice recovering from lymphopenia. Naive T cells were also induced to proliferate by IL-7, in the absence of any concomitant stimulation, albeit with delayed kinetics compared to a4b7 induction. These results are compatible with a new model of host response to lymphopenia whereby supra-homeostatic levels of IL-7 activate an unusual program of phenotypic modulation in naive T cells, characterized by the acquisition of a gut-homing and memory-like phenotype prior to the induction of cell cycling and proliferation. The role of intestinal T-cell homing in the reconstitution of the depleted T-cell pool in lymphopenic hosts remains to be defined. To formally demonstrate the physiological relevance of a4b7 induction by IL-7, we performed an in vivo study in which humanized NSG mice were injected with autologous T cells treated or not with IL-7. The results of these experiments clearly documented a preferential intestinal homing of IL-7-treated naive T cells, while no preferential homing to other tissues was detected. The physiological relevance of these phenomena in the processes of immunologic reconstitution is currently under investigation. We previously demonstrated that IL-7 treatment during the acute phase of SIV infection protected macaques from the dramatic loss of circulating naive and memory CD4(+) T cells that typically occurs upon SIV infection. This effect provides a rationale for the clinical evaluation of IL-7 in patients with acute HIV-1 infection. However, in contrast to the beneficial effects that we documented in acute SIV infection, subsequent studies an opposite effect of IL-7, which may paradoxically foster the progression of HIV-1 disease toward full-blown AIDS. Because endogenous levels of IL-7 naturally increase to supra-homeostatic concentrations in response to lymphopenia during the progression of HIV-1 disease, we hypothesized that the ability of IL-7 to redirect naive T cells to the intestinal compartment could occur in vivo in individuals with progressive HIV-1 disease. To investigate these phenomena and their relevance to AIDS in an in vivo model, we designed a new study in which 6 macaques chronically infected with either SIVmac251 or SIVsmE543 received a single injection of IL-7 (50 ug/kg, s.c.) and were sacrificed seven days later in order to specifically investigate the effects of IL-7 on T-cell homing and SIV replication in peripheral lymphoid tissues, particularly the GALT; three chronically SIV-infected animals received placebo and served as untreated controls. Detailed phenotypic analysis of circulating T cells documented a rapid upregulation of a4b7 in both CD4+ and CD8+ T cells. Comparison of pre-treatment and post-treatment intestinal tissues demonstrated that IL-7 administration resulted in increased numbers of infiltrating T cells within the GALT, associated with increased levels of SIV replication, predominantly in the Peyers patches. Enhanced SIV replication was also detected in lymph nodes. The increased levels of SIV replication in peripheral lymphoid tissues were mirrored by consistent increases in SIV plasma viremia. These in vivo data provide an initial validation of our hypothesis that the surge of endogenous IL-7 that occurs during the late stages of HIV infection may foster the terminal depletion of the CD4+ T-cell pool through the induction and activation of a4b7 leading to increased intestinal homing and HIV susceptibility. More recently, we also investigated whether exposure to HIV-1 can affect the expression of a4b7 in primary human T cells. Strikingly, we observed a marked upregulation of a4b7 on the surface of human T cells in the immediate aftermath of HIV-1 infection, which tends to decrease over time. The significance and mechanisms underlying this phenomenon are currently under investigation. Finally, we investigated the molecular mechanisms underlying the unique physiological effects of IL-7 on different T-cell populations, with particular emphasis on the ability of this cytokine to induce the expression of integrin a4b7 and the unconventional "cold" activation state in naive T cells. Thus, we performed extensive microarray analysis of mRNA transcripts from highly purified subpopulations of naive, memory a4b7high and memory a4b7low CD4+ T cells before and after stimulation with suprahomeostatic levels of IL-7. The results demonstrated upregulation of a panel of specific genes that regulate cytokine networks and cytokine receptor expression, which we are currently investigating, providing new mechanistic insights into the activity of IL-7. If these microarray results are validated by real-time PCR and siRNA knock-down, some of these IL-7-regulated genes may become suitable targets for new strategies of immunomodulation therapy.

稳态细胞因子 IL-7 目前正在临床研究中，作为各种形式的免疫缺陷（包括 HIV 感染和癌症）的潜在免疫重建剂。我们之前证明，在没有任何伴随刺激的情况下，IL-7 能够有效且选择性地诱导 CD4+ 和 CD8+ T 细胞中主要肠道归巢整合素 a4b7 的表达。我们发现这种效应：i) 对 T 细胞具有特异性，并且在幼稚亚群上更为明显； ii) IL-7处理后迅速诱导； iii) 需要超稳态浓度的 IL-7（通常在淋巴细胞减少的情况下达到的浓度）； iv) 与细胞激活的经典标志物的表达解偶联； v) 与整合素的功能激活相关，如其天然配体 MAdCAM 的结合活性增加所示。对 IL-7 诱导 a4b7 的分子机制的研究揭示了与 IL-7 受体刺激相关的两条主要信号传导途径的参与，即 JAK/STAT 和 PI3K/Akt 途径。 IL-7 对 a4b7 的诱导也在体内得到证实，无论是在感染 HIV 的人类受试者还是在用 IL-7 治疗的感染 SIV 的猕猴中。值得注意的是，我们发现 IL-7 对 a4b7 的诱导主要发生在表型幼稚 T 细胞中，这些 T 细胞同时获得了类似记忆的表型，如 CD95 表达上调和 TNF-a 分泌所示。尽管 CD45RA 和 CD45RO 的表达未改变，但用佛波酯和离子霉素刺激后。这种类似于记忆的 T 细胞“伪装”与之前在淋巴细胞减少症恢复期小鼠的幼稚 T 细胞体内记录的类似。在没有任何伴随刺激的情况下，IL-7 也诱导初始 T 细胞增殖，尽管与 a4b7 诱导相比动力学延迟。这些结果与宿主对淋巴细胞减少反应的新模型相一致，在该模型中，超稳态水平的 IL-7 激活初始 T 细胞中不寻常的表型调节程序，其特征是在诱导细胞周期和增殖之前获得肠道归巢和记忆样表型。肠道 T 细胞归巢在淋巴细胞减少宿主中耗尽的 T 细胞池重建中的作用仍有待确定。为了正式证明 IL-7 诱导 a4b7 的生理相关性，我们进行了一项体内研究，其中给人源化 NSG 小鼠注射了经过或未经过 IL-7 处理的自体 T 细胞。 这些实验的结果清楚地证明了IL-7处理的初始T细胞优先归巢于肠道，而没有检测到优先归巢于其他组织。这些现象在免疫重建过程中的生理相关性目前正在研究中。 我们之前证明，在 SIV 感染急性期期间使用 IL-7 治疗可以保护猕猴免受 SIV 感染时通常发生的循环幼稚和记忆 CD4(+) T 细胞的急剧损失。这种效应为急性 HIV-1 感染患者的 IL-7 临床评估提供了理论依据。然而，与我们记录的急性 SIV 感染的有益作用相反，随后的研究发现 IL-7 具有相反的作用，这可能会矛盾地促进 HIV-1 疾病向全面艾滋病的发展。由于在 HIV-1 疾病进展过程中，由于淋巴细胞减少，IL-7 的内源性水平自然会增加至超稳态浓度，因此我们假设，在患有进行性 HIV-1 疾病的个体体内，IL-7 能够将幼稚 T 细胞重定向至肠室。为了在体内模型中研究这些现象及其与艾滋病的相关性，我们设计了一项新研究，其中 6 只慢性感染 SIVmac251 或 SIVsmE543 的猕猴接受单次注射 IL-7（50 ug/kg，皮下注射），并在 7 天后处死，以专门研究 IL-7 对 T 细胞归巢和外周 SIV 复制的影响 淋巴组织，特别是 GALT；三只长期感染 SIV 的动物接受安慰剂并作为未经治疗的对照。循环 T 细胞的详细表型分析记录了 CD4+ 和 CD8+ T 细胞中 a4b7 的快速上调。治疗前和治疗后肠道组织的比较表明，IL-7 给药导致 GALT 内浸润性 T 细胞数量增加，这与 SIV 复制水平增加相关，主要在派耶斯集结区。淋巴结中也检测到 SIV 复制增强。外周淋巴组织中 SIV 复制水平的增加与 SIV 血浆病毒血症的持续增加相一致。这些体内数据初步验证了我们的假设，即 HIV 感染后期发生的内源性 IL-7 激增可能通过 a4b7 的诱导和激活促进 CD4+ T 细胞库的最终耗尽，从而导致肠道归巢和 HIV 易感性增加。 最近，我们还研究了暴露于 HIV-1 是否会影响原代人类 T 细胞中 a4b7 的表达。引人注目的是，我们在 HIV-1 感染后立即观察到人类 T 细胞表面 a4b7 的显着上调，但随着时间的推移，这种上调往往会下降。 目前正在研究这种现象的意义和机制。最后，我们研究了IL-7对不同T细胞群的独特生理作用的分子机制，特别强调了这种细胞因子诱导整合素a4b7表达的能力以及幼稚T细胞中非常规的“冷”激活状态。因此，我们在用超稳态水平的 IL-7 刺激之前和之后，对来自高度纯化的初始、记忆 a4b7high 和记忆 a4b7low CD4+ T 细胞亚群的 mRNA 转录本进行了广泛的微阵列分析。结果表明，一组调节细胞因子网络和细胞因子受体表达的特定基因上调，我们目前正在研究这些基因，从而为 IL-7 的活性提供了新的机制见解。如果这些微阵列结果通过实时 PCR 和 siRNA 敲除得到验证，其中一些 IL-7 调节基因可能成为免疫调节治疗新策略的合适靶标。