Immunomodulatory Effects of IL-7 in Primate Immunodeficiency Virus Infections

IL-7 在灵长类免疫缺陷病毒感染中的免疫调节作用

• 批准号: 7964559
• 负责人: paolo lusso
• 金额: $ 84.11万
• 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/7964559
• 关键词: Acquired Immunodeficiency Syndrome; Acute; Adolescent; Affect; Anemia; Animals; Anti-Retroviral Agents; Apoptosis; Apoptotic; B-Cell Activation; B-Lymphocytes; Binding; Blood Platelets; CCR9 gene; CD4 Positive T Lymphocytes; CD8B1 gene; Cell Count; Cells; Cessation of life; Chronic; Chronic Phase; Clinical; Clinical Trials; Complex; Cytokine Receptors; Data; Development; Disease; Disease Progression; Dose; Erythrocytes; Gene Expression; Genes; Genetic Transcription; Gut associated lymphoid tissue; HIV Envelope Protein gp120; HIV Infections; HIV-1; Hemoglobin concentration result; Homeostasis; Homing; Immune; Immune system; Immunoglobulin Genes; Immunologic Deficiency Syndromes; Induction of Apoptosis; Infection; Integrin alpha4; Integrins; Interleukin 7 Receptor; Interleukin-7; Interruption; Ligands; Link; Lymphocyte; Lymphoid Tissue; Lymphopenia; MHC Class II Genes; Macaca; Macaca mulatta; Mediating; Megakaryocytes; Memory; Messenger RNA; Microarray Analysis; Modeling; Molecular; Molecular Profiling; Monitor; Mononuclear; Neurologic; Pathogenesis; Patients; Peripheral; Peripheral Blood Mononuclear Cell; Phase; Phase I Clinical Trials; Phenotype; Play; Predisposition; Primate Lentiviruses; Protocols documentation; Receptor Gene; Recombinants; Research; Retreatment; Role; SIV; Side; Signal Transduction; Site; Stimulus; T cell regulation; T memory cell; T-Lymphocyte; T-Lymphocyte Subsets; TNFRSF1B gene; Tumor Necrosis Factor Receptor; Tumor Necrosis Factor-Beta; Tumor Necrosis Factor-alpha; Up-Regulation; Viral; Viral Load result; Virus Diseases; antiretroviral therapy; chemokine receptor; clinical effect; cytokine; design; human TNF protein; in vivo; insight; lymph nodes; memory CD4 T lymphocyte; nonhuman primate; peripheral blood; prevent; pro-apoptotic protein; receptor; reconstitution; treatment duration

IL-7 is a non-redundant cytokine that plays a critical role in the regulation of the T-cell compartment of the immune system. Due to its ability to maintain the homeostasis of the T-lymphocyte pool and restore it under conditions of lymphopenia, IL-7 is currently under clinical investigation as a potential immune-reconstitution agent in various forms of immunodeficiency, including HIV infection. We previously demonstrated that IL-7 induces a dramatic reduction in the levels of spontaneous ex vivo apoptosis in both CD4+ and CD8+ T cells derived from HIV-infected patients, while having no significant effects on cells from HIV-seronegative subjects. To further investigate the effects of IL-7 in the course of HIV-1 infection, we have performed a study (LIR-9) of in vivo administration of IL-7 in a well-established nonhuman primate model of AIDS. Previous in vivo studies in macaques chronically infected with SIV demonstrated that IL-7 administration causes a marked increase in naive T-cell counts, as well as proliferation and activation of both CD4+ and CD8+ memory T cells, without augmenting the viral load. Phase 1 clinical trials in chronically HIV-infected patients concomitantly receiving antiretroviral treatment have demonstrated that short-term IL-7 treatment is safe and has transient beneficial effects on peripheral CD4+ T-cell counts without inducing sustained increases in viral replication levels. The LIR-9 protocol was designed to evaluate the immunological, virological and clinical effects of administering recombinant macaque IL-7, produced in a fully glycosylated form, during the acute and chronic phases of infection with a pathogenic SIV isolate, SIVmac251, in juvenile Rhesus macaques (Macacamulatta). The animals (n=12) were divided into 2 groups: group 1 (n=6) received only SIV, while group 2 (n=6) received IL-7 and SIV. In the latter group, IL-7 was administered once a week, s.c., at a dose of 50 micrograms/kg. No antiretroviral treatment was administered. During the acute phase, treatment with IL-7 had distinct effects on the immunological profile of SIV-infected macaques. Specifically, the animals showed a significant increase in the mean absolute numbers of total circulating lymphocytes, affecting both CD4+ T cells and CD8+ T cells, which persisted throughout the treatment period. The effect gradually disappeared within 2-3 weeks of treatment interruption. Importantly, treatment with IL-7 prevented the early depletion of peripheral blood central memory (CM) CD4+ T cells during the acute phase of SIV infection without significantly increasing SIV replication levels. This notwithstanding, CM CD4+ T cells started to decline during the course of IL-7 treatment and became significantly depleted within a few weeks of treatment interruption. Treatment with IL-7 also prevented the depletion of peripheral blood nave (N) CD4+ T cells, and induced significant increases in all subsets of CD8+ T cells (N, CM, EM). In lymphoid tissues (gut-associated lymphoid tissue GALT and lymph nodes), IL-7 did not significantly affect the level of spontaneous apoptosis nor the phenotype of CD4+ T cells, while it increased the proportion of EM CD8+ T cells in lymph nodes. During the post-acute phase, the animals were monitored for several months without further administration of IL-7. Unfortunately, two animals in each group showed early signs of disease progression with unusual manifestations such as neurologic and GI disease in the absence of significant depletion of circulating CD4+ T cells. This picture is in line with previous descriptions of rapid SIV-disease progression (RP) in macaques, reportedly associated with a unique pathogenesis mediated by massive SIV replication in cells of the mononuclear phagocytic lineage rather than CD4+ T cells (Brown et al., J. Virol. 2007). Our preliminary microarray data show distinctive gene expression profiles at baseline in PBMC from RP macaques vs. conventional progressors (CP), with upregulation of B-cell-associated genes (immunoglobulins, MHC class II, B-cell activation markers) and downmodulation of T-cell genes, platelet/megakaryocyte genes and the IL-7 receptor gene. During the chronic phase, low-dose IL-7 treatment (10 micrograms/kg) was restarted in the 4 remaining animals in group 2 at month 8 of SIV inoculation. In all the animals, retreatment induced transient increases in both CD4+ and CD8+ T cells, although higher IL-7 doses were required in some. However, these changes were only transient and peripheral T-cell counts returned to baseline levels during the treatment period. Severe anemia developed in two animals during prolonged IL-7 treatment, although it is unclear whether this effect was related to IL-7 treatment because the other two animals did not show reductions in circulating red blood cells or hemoglobin levels. In parallel with the LIR-9 study, we have started to investigate, both ex vivo and in vivo, the molecular mechanisms of spontaneous T-cell apoptosis in HIV-1-infected subjects, as well as the mechanisms of anti-apoptotic activity of IL-7. In vivo studies, which are currently under way, are conducted by microarray analysis of mRNA transcription profiles in IL-7-treated macaques and untreated controls followed longitudinally during the acute phase of SIV infection. We have demonstrated that the two major pathways of apoptosis (endogenous and exogenous) are both activated in PBMC from HIV-infected subjects during ex vivo culture in the absence of activating signals. Likewise, the reduction of apoptosis mediated by IL-7 was found to affect both apoptosis pathways. In line with previous data, the effect of IL-7 was associated with a marked increase in the intracellular levels of Bcl-2. Moreover, we documented a dramatic decrease in the level of activation of the pro-apoptotic protein Bax in both CD4+ and CD8+ T cells from HIV-1-infected subjects treated with IL-7 ex vivo. To gain further insights into the mechanisms of spontaneous apoptosis in HIV-infected subjects and its reduction by IL-7, we also evaluated the levels of expression of several death receptors and their ligands. We found that IL-7 treatment ex vivo results in a significant increase in the expression of two apoptosis-associated receptors, CD95/Fas and lymphotoxin receptor/TNF-receptor III, as well as of the pro-apoptotic cytokine TNF-alpha, despite the reduction of apoptosis levels. CD120b/TNF-receptor II, which is not typically linked to induction of apoptosis, was also upregulated. Altogether, these data suggest a complex immunomodulatory effect of IL-7 with a dominant effect of anti-apoptotic molecules such as Bcl-2, which counteract the action of pro-apoptotic receptors and cytokines. IL-7 is an essential cytokine in the development and homeostasis of the GALT. Thus, we have also investigated the effects of IL-7 on the expression of gut-homing receptors, in particular the chemokine receptor CCR9 and the integrin alpha4-beta7 (a4b7). Preliminary results indicate that IL-7 is a potent inducer of a4b7 expression in both CD4+ and CD8+ T cells, even in the absence of additional activating stimuli. This effect occurs in both phenotypic memory (CD45RO+) and nave (CD45RO-) T cells, and is associated with the induction of the fully activated state of a4b7, as indicated by an increased binding activity of the natural integrin ligands, MAdCAM and HIV-1 gp120. Altogether, these data suggest a dual role for IL-7 in HIV-1 infection: on one side, IL-7 may reduce the levels of apoptosis and increase the pool of CD4+ and CD8+ T cells, thereby favoring the immune reconstitution of subjects concomitantly receiving antiretroviral therapy; on the other side,IL-7 may favor the homing of T cells to the gut, which is a primary site of HIV-1 replication, and, consequently, susceptibility to HIV infection.

IL-7是一种非冗余细胞因子，在免疫系统的t细胞区室调节中起关键作用。由于IL-7能够在淋巴细胞减少的情况下维持t淋巴细胞池的稳态并恢复它，IL-7目前正在临床研究中，作为一种潜在的免疫重建剂，用于各种形式的免疫缺陷，包括HIV感染。我们之前证明，IL-7诱导来自hiv感染患者的CD4+和CD8+ T细胞的自发体外凋亡水平急剧降低，而对hiv血清阴性受试者的细胞没有显著影响。为了进一步研究IL-7在HIV-1感染过程中的作用，我们在一个已建立的非人类艾滋病灵长类动物模型中进行了IL-7体内管理的研究（LIR-9）。先前对慢性SIV感染的猕猴进行的体内研究表明，IL-7的使用会导致初始T细胞计数的显著增加，以及CD4+和CD8+记忆T细胞的增殖和激活，而不会增加病毒载量。在同时接受抗逆转录病毒治疗的慢性hiv感染患者中进行的1期临床试验表明，短期IL-7治疗是安全的，并且对外周血CD4+ t细胞计数有短暂的有益影响，而不会引起病毒复制水平的持续增加。