Interleukin-7 Treatment Research Articles

Interleukin-7 potentiates MAPK10-elicited host-protective vaccine against Leishmania donovani

Leishmania donovani causes the potentially fatal disease visceral leishmaniasis for which neither a vaccine nor an adjuvant for human use exists. Although interleukin-7 (IL-7) is implicated in CD4+ T-cell response stabilization, its anti-leishmanial function is uncertain. Therefore, we examined whether IL-7 would potentiate the efficacy of Leishmania major-expressed MAPK10 (LmjMAPK10; M10)-elicited anti-leishmanial host-protective response. We observed that aligning with IL-7R expression, IL-7 increased IFN-γ-secreting TH1 cell but reduced IL-4-producing TH2 cells and production of IL-10 and TGF-β effectuating anti-leishmanial functions in susceptible BALB/c mouse-derived macrophages. Co-culturing IL-7-pre-treated L. donovani-infected macrophages with L. donovani-infected BALB/c-derived T cells induced IFN-γ-dominated TH1 type anti-leishmanial function. IL-7 treatment of L. donovani-infected BALB/c mice significantly reduced splenic and hepatic parasite loads. Co-culturing CD4+ T cells from IL to 7-treated mice with L. donovani-infected macrophages reduced amastigote numbers suggesting IL-7-elicited host-protective effector T cells. Priming BALB/c with M10 + IL-7 reduced the splenic parasite burden more effectively than that was observed in M10-primed mice. An enhanced protection against L. donovani infection was accompanied by enhanced IL-12 and IFN-γ, but suppressed IL-10 and IL-4, response and host-protective TH1 and memory T cells. These results indicate IL-7-induced leishmanial antigen-specific memory T cell response that protects a susceptible host against L. donovani infection.

Severe persistent mycobacteria antigen stimulation causes lymphopenia through impairing hematopoiesis.

Miliary tubersculosis (TB), an acute systemic blood disseminated tuberculosis mainly caused by Mycobacterium tuberculosis (M. tuberculosis), can cause signs of lymphopenia in clinical patients. To investigate whether/how persistent mycobacteria antigen stimulation impairs hematopoiesis and the therapeutic effect of interleukin-7 (IL-7), a mouse model of Mycobacterium Bovis Bacillus Calmette-Guérin (BCG) intravenous infection with/without an additional stimulation with M. tuberculosis multi-antigen cocktail containing ESAT6-CFP10 (EC) and Mtb10.4-HspX (MH) was established. Consistent with what happened in miliary TB, high dose of BCG intravenous infection with/without additional antigen stimulation caused lymphopenia in peripheral blood. In which, the levels of cytokines IFN-γ and TNF-α in serum increased, and consequently the expression levels of transcription factors Batf2 and IRF8 involved in myeloid differentiation were up-regulated, while the expression levels of transcription factors GATA2 and NOTCH1 involved in lymphoid commitment were down-regulated, and the proliferating activity of bone marrow (BM) lineage- c-Kit+ (LK) cells decreased. Furthermore, recombinant Adeno-Associated Virus 2-mediated IL-7 (rAAV2-IL-7) treatment could significantly promote the elevation of BM lymphoid progenitors. It suggests that persistent mycobacteria antigen stimulation impaired lymphopoiesis of BM hematopoiesis, which could be restored by complement of IL-7.

In vitro Interleukin-7 treatment partially rescues MAIT cell dysfunction caused by SARS-CoV-2 infection

MAIT cells have been shown to be activated upon several viral infections in a TCR-independent manner by responding to inflammatory cytokines secreted by antigen-presenting cells. Recently, a few studies have shown a similar activation of MAIT cells in response to severe acute respiratory coronavirus 2 (SARS-CoV-2) infection. In this study, we investigate the effect of SARS-CoV-2 infection on the frequency and phenotype of MAIT cells by flow cytometry, and we test in vitro stimulation conditions on the capacity to enhance or rescue the antiviral function of MAIT cells from patients with coronavirus disease 2019 (COVID-19). Our study, in agreement with recently published studies, confirmed the decline in MAIT cell frequency of hospitalized donors in comparison to healthy donors. MAIT cells of COVID-19 patients also had lower expression levels of TNF-alpha, perforin and granzyme B upon stimulation with IL-12 + IL-18. 24 h’ incubation with IL-7 successfully restored perforin expression levels in COVID-19 patients. Combined, our findings support the growing evidence that SARS-CoV-2 is dysregulating MAIT cells and that IL-7 treatment might improve their function, rendering them more effective in protecting the body against the virus.

Preserved MAIT cell numbers and function in idiopathic CD4 lymphocytopenia.

Mucosal-associated invariant T (MAIT) cells constitute a subset of unconventional, MR1-restricted T-cells involved in antimicrobial responses as well as inflammatory, allergic and autoimmune diseases. Chronic infection and inflammatory disorders as well as immunodeficiencies are often associated with decline and/or dysfunction of MAIT cells. Herein, we investigate the MAIT cells in patients with idiopathic CD4 + lymphocytopenia (ICL), a syndrome characterized by consistently low CD4 T-cell counts (<300 cell/µL) in the absence of HIV infection or other known immunodeficiency, and by susceptibility to certain opportunistic infections. The numbers, phenotype and function of MAIT cells in peripheral blood were preserved in ICL patients compared to healthy controls. Furthermore, administration of IL-7 to ICL patients expanded the CD8 + MAIT cell subset, with maintained responsiveness and effector functions after IL-7 treatment. In conclusion, ICL patients maintain normal levels and function of MAIT cells preserving some antibacterial responses despite the deficiency in CD4 + T cells.

CAR T cells get a STAT tune-up

Tumor Immunology Adoptive cell therapies using chimeric antigen receptor (CAR) T cells display potent antitumor immunity, but T cell exhaustion can compromise their efficacy. Building on a previous observation that interleukin-7 treatment induced polyfunctional CD4+ T cells producing multiple cytokines, Ding et al. expressed a constitutively active variant of the signaling protein STAT5 called CASTAT5 in mouse CD4+ T cells specific for a tumor antigen. CASTAT5-expressing T cells underwent epigenetic remodeling, developed polyfunctionality, and promoted CD8+ T cell–dependent elimination of tumors. In a mouse model of CAR T cells targeting the B cell antigen CD19, CASTAT5 expression in both CD4+ and CD8+ T cells resulted in improved tumor elimination. These findings introduce a new T cell–engineering approach for CAR T cells that could yield improved resistance to exhaustion and more robust antitumor activity. Sci. Immunol. 5 , eaba5962 (2020).

Interleukin-7 protects against bacterial respiratory infection by promoting IL-17A-producing innate T-cell response.

Interleukin-7 (IL-7) is a critical cytokine in B- and T-lymphocyte development and maturation. Recent evidence suggests that IL-7 is a preferential homeostatic and survival factor for RORγt+ innate T cells such as natural killer T (NKT) cells, γδT cells, and mucosal-associated invariant T (MAIT) cells in the periphery. Given the important contribution of these populations in antibacterial immunity at barrier sites, we questioned whether IL-7 could be instrumental in boosting the local host immune response against respiratory bacterial infection. By using a cytokine-monoclonal antibody approach, we illustrated a role for topical IL-7 delivery in increasing the pool of RORγt+ IL-17A-producing innate T cells. Prophylactic IL-7 treatment prior to Streptococcus pneumoniae infection led to better bacterial containment, a process associated with increased neutrophilia and that depended on γδT cells and IL-17A. Last, combined delivery of IL-7 and α-galactosylceramide (α-GalCer), a potent agonist for invariant NKT (iNKT) cells, conferred an almost total protection in terms of survival, an effect associated with enhanced IL-17 production by innate T cells and neutrophilia. Collectively, we provide a proof of concept that IL-7 enables fine-tuning of innate T- cell functions. This might pave the way for considering IL-7 as an innovative biotherapeutic against bacterial infection.

IL-7 treatment augments and prolongs sepsis-induced expansion of IL-10-producing B lymphocytes and myeloid-derived suppressor cells.

Immunological dysregulation in sepsis is associated with often lethal secondary infections. Loss of effector cells and an expansion of immunoregulatory cell populations both contribute to sepsis-induced immunosuppression. The extent and duration of this immunosuppression are unknown. Interleukin 7 (IL-7) is important for the maintenance of lymphocytes and can accelerate the reconstitution of effector lymphocytes in sepsis. How IL-7 influences immunosuppressive cell populations is unknown. We have used the mouse model of peritoneal contamination and infection (PCI) to investigate the expansion of immunoregulatory cells as long-term sequelae of sepsis with or without IL-7 treatment. We analysed the frequencies and numbers of regulatory T cells (Tregs), double negative T cells, IL-10 producing B cells and myeloid-derived suppressor cells (MDSCs) for 3.5 months after sepsis induction. Sepsis induced an increase in IL-10+ B cells, which was enhanced and prolonged by IL-7 treatment. An increased frequency of MDSCs in the spleen was still detectable 3.5 months after sepsis induction and this was more pronounced in IL-7-treated mice. MDSCs from septic mice were more potent at suppressing T cell proliferation than MDSCs from control mice. Our data reveal that sepsis induces a long lasting increase in IL-10+ B cells and MDSCs. Late-onset IL-7 treatment augments this increase, which should be relevant for clinical interventions.

According to Hepatitis C Virus (HCV) Infection Stage, Interleukin-7 Plus 4-1BB Triggering Alone or Combined with PD-1 Blockade Increases TRAF1low HCV-Specific CD8+ Cell Reactivity.

Hepatitis C virus (HCV)-specific CD8+ T cells suffer a progressive exhaustion during persistent infection (PI) with HCV. This process could involve the positive immune checkpoint 4-1BB/4-1BBL through the loss of its signal transducer, TRAF1. To address this issue, peripheral HCV-specific CD8+ T cells (pentamer-positive [pentamer+]/CD8+ T cells) from patients with PI and resolved infection (RI) after treatment were studied. The duration of HCV infection and the liver fibrosis progression rate inversely correlated with the likelihood of detection of peripheral pentamer+/CD8+ cells. In PI, pentamer+/CD8+ cells had impaired antigen-specific reactivity that worsened when these cells were not detectable ex vivo Short/midduration PI was characterized by detectable peripheral PD-1+ CD127low TRAF1low cells. After triggering of T cell receptors (TCR), the TRAF1 level positively correlated with the levels of CD127, Mcl-1, and CD107a expression and proliferation intensity but negatively with PD-1 expression, linking TRAF1low to exhaustion. In vitro treatment with interleukin-7 (IL-7) upregulated TRAF1 expression, while treatment with transforming growth factor-β1 (TGF-β1) did the opposite, suggesting that the IL-7/TGF-β1 balance, besides TCR stimulation, could be involved in TRAF1 regulation. In fact, the serum TGF-β1 concentration was higher in patients with PI than in patients with RI, and it negatively correlated with TRAF1 expression. In line with IL-7 increasing the level of TRAF1 expression, IL-7 plus 4-1BBL treatment in vitro enhanced T cell reactivity in patients with short/midduration infection. However, in patients with long-lasting PI, anti-PD-L1, in addition to the combination of IL-7 and 4-1BBL, was necessary to reestablish T cell proliferation in individuals with slowly progressing liver fibrosis (slow fibrosers) but had no effect in rapid fibrosers. In conclusion, a peripheral hyporeactive TRAF1low HCV-specific CD8+ T cell response, restorable by IL-7 plus 4-1BBL treatment, characterizes short/midduration PI. In long-lasting disease, HCV-specific CD8+ T cells are rarely detectable ex vivo, but treatment with IL-7, 4-1BBL, and anti-PD-L1 recovers their reactivity in vitro in slow fibrosers.IMPORTANCE Hepatitis C virus (HCV) infects 71 million people worldwide. Two-thirds develop a chronic disease that can lead to cirrhosis and hepatocellular carcinoma. Direct-acting antivirals clear the infection, but there are still patients who relapse. In these cases, additional immunotherapy could play a vital role. A successful anti-HCV immune response depends on virus-specific CD8+ T cells. During chronic infection, these cells are functionally impaired, which could be due to the failure of costimulation. This study describes exhausted specific T cells, characterized by low levels of expression of the signal transducer TRAF1 of the positive costimulatory pathway 4-1BB/4-1BBL. IL-7 upregulated TRAF1 expression and improved T cell reactivity in patients with short/midduration disease, while in patients with long-lasting infection, it was also necessary to block the negative PD-1/PD-L1 checkpoint. When the results are taken together, this work supports novel ways of restoring the specific CD8+ T cell response, shedding light on the importance of TRAF1 signaling. This could be a promising target for future immunotherapy.

Interleukin 7 promotes motility of naive T cells in the lymph node

Abstract Naïve T cells interact with dendritic cells (DCs) in lymph nodes to become activated and effect a specific immune response. The chemokine CCL21 and lysophosphatidic acid (LPA) have both been demonstrated to be important for T cell movement within the T cell zone of the lymph node. However, the residual motility in the absence of both CCL21 signaling via CCR7 and LPA suggest that additional molecules can play a role in driving T cell movement within lymph nodes. Using two photon microscopy, we show interleukin-7 (IL-7) promotes T cell motility in vitro and in vivo, in addition to its known function as a survival factor. Blocking IL-7 signaling in the lymph node elicited a reduction in T cell speed. IL-7 treatment of primary T cells in vitro resulted in increased migration across a permeable barrier and small GTPase RhoA activation. We further demonstrate that IL-7 combines with CCL21 and LPA to promote naïve T cell motility. Our results indicate that IL-7 is a novel regulator of T cell motion in lymph nodes, in addition to its effect on T cell survival.

Interleukin-7 treatment of PML in a patient with idiopathic lymphocytopenia

Objective:To describe the compassionate use of interleukin-7 (IL-7) for treatment of progressive multifocal leukoencephalopathy (PML) in the setting of idiopathic CD8+ greater than CD4+ lymphocytopenia.Methods:A 66-year-old HIV-seronegative man presented with progressive language dysfunction. MRI showed hyperintense lesions in the left hemispheric white matter with mild contrast enhancement. A brain biopsy performed 4 months after symptom onset established the diagnosis of PML. The patient had profound lymphocytopenia with absolute lymphocyte count (ALC) at 168 cells/μL, 87 CD4+ T cells/μL, and 7 CD8+ T cells/μL. There was no evidence of hematologic malignancy or rheumatologic disease.Results:The patient received 3 intramuscular injections of IL-7 at a dose of 10 μg/kg per week with no adverse effects. ALC peaked at 595 cells/μL, CD4+ T cells at 301 cells/μL, and CD8+ T cells at 34 cells/μL 3 weeks after completion of treatment. His lesions on MRI stabilized and neurologic examination mildly improved. JCV-specific T-cell responses measured by intracellular cytokine staining were not altered after treatment with IL-7 but there was a marked increase in regulatory T cells.Conclusion:This case further supports the investigational use of IL-7 in patients who develop PML in the setting of ICL.Classification of evidence:This study provides Class IV evidence that for patients with ICL and PML, IL-7 improves PML-related-outcomes. The study is rated Class IV because it is a case report.

P27KIP1 is involved in ERK1/2-mediated MMP-9 expression via the activation of NF-κB binding in the IL-7-induced migration and invasion of 5637 cells

Interleukin-7 (IL-7) plays a pivotal role in the development and survival of lymphocytes, but its role in cancer cell responses remains unexplained. In this study, IL-7 treatment resulted in a significant induction in the wound-healing migration and Matrigel invasion of the 5637 bladder cancer cells, but it did not result in cell proliferation. In addition, IL-7 treatment strongly induced MMP-9 expression, and increased the binding activation of NF-κB and AP-1 motifs, the important transcription factors that regulate MMP-9 expression. Moreover, the treatment of 5637 cells with IL-7 stimulated the phosphorylation of ERK1/2. U0126, an ERK1/2-specific inhibitor, blocked IL-7-induced cell migration and invasion, and also suppressed the expression of MMP-9 in the presence of IL-7. Inhibition of the ERK1/2 function consistently reversed the binding activity of NF-κB without altering AP-1 activation in IL-7-stimulated cells. Among the cell cycle regulators examined, only the expression of the cell cycle inhibitor p27KIP1 was induced by IL-7. Moreover, the inhibition of p27KIP1 by small interfering RNA (siRNA) abolished the migration, invasion and phosphorylation of ERK1/2, the expression of MMP-9, and the binding activity of the NF-κB motif in IL-7-stimulated 5637 cells. These results demonstrated that the cell cycle inhibitor p27KIP1 is involved in ERK1/2-mediated MMP-9 expression via activation of the NF-κB binding motif, which leads to the migration and invasion of bladder cancer cells induced by IL-7. These novel results could help explain the migration and invasion of bladder tumor cells.

Chemo-Immunotherapy with Oxaliplatin and Interleukin-7 Inhibits Colon Cancer Metastasis in Mice

Combination of immunotherapy and chemotherapy has shown promise for cancer. Interleukin-7 (IL-7) can potentially enhance immune responses against tumor, while oxaliplatin (OXP), a platinum-based drug, can promote a favorable immune microenvironment and stimulate anticancer immune responses. We evaluated the anti-tumor activity of IL-7 combining OXP against a murine colon carcinoma in vitro and in vivo and studied the tumor immune microenvironment to investigate whether the combined treatment affects on the local immune cell populations. Utilizing lung and abdomen metastasis models by inoculation of CT26 mice colon cancer cells, we evaluated the anti-tumor efficacy of combining IL-7 and OXP in mice models. Tumor immune microenvironment was evaluated by flow cytometric analysis and immunohistochemical staining. Our study showed that the in vivo administration of IL-7 combined with OXP markedly inhibited the growth of tumors in lung and abdomen metastasis models of colon cancer. IL-7 alone had no effect on tumor growth in mice and IL-7 did not alter cell sensitivity to OXP in culture. The antitumor effect of combining IL-7 and OXP correlated with a marked increase in the number of tumor-infiltrating activated CD8+ T cells and a marked decrease in the number of regulatory T (Treg) cells in spleen. Our data suggest that OXP plus IL-7 treatment inhibits tumor cell growth by immunoregulation rather than direct cytotoxicity. Our findings justify further evaluation of combining IL-7 and chemotherapy as a novel experimental cancer therapy.

A Novel Synthetic GMCSF and IL7 Fusion Cytokine (GIFT7) Leads to T Cell Neogenesis by Reversing Age-Related Thymic Atrophy and Overcoming PD-1-Assocaited CD8 Exhaustion

AbstractAbstract 3289Functional T cell immunity depends on the diversity of T cell receptor (TCR) repertoire. Numerous cytolytic assaults can perturb effector cell fitness by inhibiting thymic de novo T cell production or predisposing peripheral CD8+ T cells to exhaustion. In fact, age-associated thymic atrophy and PD-1 upregulation remain the critical components of immune dysfunction.Normal thymopoiesis arises from marrow-derived CD3−CD4−CD8− triple-negative T cell progenitors (TN) which seed the thymic cortex. Thereafter, TN develop into mature single-positive (SP) CD4 or CD8 T cells after expressing both CD4 and CD8 (double-positive-DP) transiently, leading to de novo T cell production. Interleukin-7 (IL7) is a singularly important common γ-chain interleukin involved in this process. In order to pharmacologically enhance thymopoiesis, we report the development of a novel biopharmaceutical based on the fusion of GMCSF and IL7, hereafter GIFT7. Systemic administration of GIFT7 compared to IL7 in young immune competent mice leads to a transient increase in the number of DN1 (5.48±1.01 v.s. 2.74±1.07 × 106, p=0.046) by day 7. Total thymic cellularity significantly increases in GIFT7-treated group by day 14 (237±51.3 v.s. 123±25.6 × 106, p=0.026). GIFT7-mediated hypertrophic effect is significantly more pronounced in aged thymi: 111±21.8, 67.8±13.9, 60.3±4.6 × 106 for 7-dose of (5ug kg−1) GIFT7, IL7, or PBS treatment respectively. We observed a significant increase in DN1 and DN4 subsets with the greatest fold difference in the CD44int DN1 subset. Histologically, GIFT7 administration leads to significant cortical thymic hyperplasia (cortex: medulla ratio 2.67:1). Functionally, GIFT7 enhances viral-specific CTL responsiveness as modeled by murine cytomegalovirus (MCMV) peptide MHC+ tetramer enumeration (10.4±3.8 v.s. 2.9±1.4 × 106 for GIFT7 and untreated respectively, p<0.05).In the periphery, GIFT7 selectively expand a CD8+ subset with a Central Memory (CM) phenotype defined as CD8+CD44+CD62L+CCR7+KLRG−CD27+PD1−. This unique expansive effect of GIFT7 is also demonstrated on peripheral blood mononuclear cells (PBMC) derived from non-human primates (NHP), in that GIFT7 stimulation of pre-activated NHP-PBMC leads to a two-fold increase in total cell number after 3 days and >80% of Ki67+ expression in both CD4+ and CD8+ compartments. Interestingly, GIFT7-mediated proliferation in CD8+ T cells is accompanied by a 40% decrease in the mean fluorescent intensity (MFI) of PD1 expression.Our work identifies a CD44intCD25− subset of DN thymocytes most responsive to IL7R-mediated STAT5 hypersignalling and their function as T cell progenitors in GIFT7-driven thymic reconstitution. This points to the translational potential of GIFT7 or GIFT7-primed T lineage cells as treatment of immune malfunction. Disclosures:No relevant conflicts of interest to declare.

IL-7 modulates B cells survival and activation by inducing BAFF and CD70 expression in T cells

Interleukin-7 (IL-7) promotes the maintenance and activation of peripheral T cells, whereas it does not act directly on mature B cells due to the lack of IL-7Rα expression on these. We report here that, in spite of the insensitivity of B cells to IL-7, high concentration of IL-7 can lead to increased B cell survival and antibody production in the presence of T cells, without the use of any further B cell stimulatory signal. IL-7 promoted B cell activation through inducing CD70 expression on resting T cells, particularly on CD4+ memory cells. The interaction of CD70 molecules with the B cell costimulatory receptor CD27 led to B cell proliferation, the accumulation of CD38 + CD20- plasmablasts and antibody production. In addition, IL-7 treatment induced BAFF secretion from resting peripheral T cells thereby promoting B cell survival. IL-7 levels can increase in lymphopenic conditions, in autoimmune diseases or in patients receiving T cell regenerative IL-7 therapy. Based on our findings high IL-7 levels can lead to increased B cell activation by inducing the B cell regulatory proteins CD70 and BAFF in resting T cells. Such activity might be beneficial in short term immune-stimulatory IL-7 therapies; permanently increased IL-7 levels, on the other hand, can contribute to impaired B cell tolerance.

Interleukin-7 Inhibits Tumor-Induced CD27−CD28− Suppressor T Cells: Implications for Cancer Immunotherapy

We have previously reported that many types of tumors can induce changes in human T cells that lead to the acquisition of suppressive function and phenotypic alterations resembling those found in senescent T cells. In the present study, we find a role for interleukin 7 (IL-7) in protecting T cells from these changes and further define involved signaling pathways. We evaluated the ability of IL-7 treatment to prevent the gain of suppressive function and phenotypic alterations in human T cells after a short coculture with tumor cells in vitro. We then used inhibitors of components of the phosphoinositide 3-kinase (PI3K)/AKT pathway and short interfering RNA knockdown of Mcl-1 and Bim to evaluate the role of these signaling pathways in IL-7 protection. We found that IL-7 inhibits CD27/CD28 loss and maintains proliferative capacity, IL-2 production, and reduced suppressive function. The protective ability of IL-7 depended on activation of the PI3K/AKT pathway, which inhibited activation of glycogen synthase kinase 3β, which, in turn, prevented the phosphorylation and loss of Mcl-1. We further showed a key role for Mcl-1 in that its knockdown or inhibition abrogated the effects of IL-7. In addition, knockdown of the Mcl-1 binding partner and proapoptotic protein Bim protected T cells from these dysfunctional alterations. These observations confirm the role for Bcl-2 family members in cytokine signaling and suggest that IL-7 treatment in combination with other immunotherapies could lead to new clinical strategies to maintain normal T-cell function and reduce tumor-induced generation of dysfunctional and suppressor T cells.

Interleukin-7 Treatment Reverses Parenteral Nutrition-Induced Impairment of Resistance to Bacterial Pneumonia with Increased Secretory Immunoglobulin A Levels

Absence of enteral delivery of nutrients causes gut associated lymphoid tissue (GALT) atrophy and an imbalance between immunoglobulin A (IgA)-inhibiting Th1 and IgA-stimulating Th2 cytokine levels in the gut, leading to impaired mucosal immunity. We previously demonstrated exogenous IL-7 to reverse parenteral nutrition (PN)-induced GALT cell loss but not to normalize the gut cytokine imbalance or reduce secretory IgA levels, in uninjured mice. Herein, we examined effects of exogenous IL-7 during PN on survival and IgA levels after intra-tracheal bacterial challenge. Sixty-five male Institute of Cancer Research (ICR) mice were randomized to chow, PN or PN+IL-7 (1 μg/kg, administered i.v. twice a day), and jugular vein catheters were inserted. The chow and PN mice received normal saline i.v. infusions instead of IL-7. After 5 d of feeding (chow or PN) and treatment, 8 × 10(7)Pseudomonas aeruginosa were instilled intra-tracheally. Survival was observed in 41 mice, while 24 were killed at 6 h after challenge and small intestinal, nasal and bronchoalveolar washings were obtained for IgA measurement. PN significantly reduced survival time and IgA levels in small intestine and bronchoalveolar washings compared with chow feeding. IL-7 treatment restored these parameters. Therefore, no significant differences in survival or secretory IgA levels were found between the chow and PN+IL-7 groups. Exogenous IL-7 reverses PN-induced impairment of resistance to respiratory tract infections associated with increased secretory IgA levels.

Interleukin-7 treatment counteracts IFN-α therapy-induced lymphopenia and stimulates SIV-specific cytotoxic T lymphocyte responses in SIV-infected rhesus macaques

AbstractInterferon-α (IFN-α)–based therapy is presently the standard treatment for hepatitis C virus (HCV)–infected patients. Despite good effectiveness, this cytokine is associated with major side effects, including significant lymphopenia, that limits its use for HIV/HCV-coinfected patients. Interleukin-7 (IL-7) has recently shown therapeutic potential and safety in several clinical trials designed to demonstrate T-cell restoration in immunodeficient patients. The purpose of this study was to evaluate, in simian immunodeficiency virus-infected rhesus macaques, the relevance of IL-7 therapy as a means to overcoming IFN-α–induced lymphopenia. We showed that low-dose IFN-α treatment induced strong lymphopenia in chronically infected monkeys. In contrast, high-dose IFN-α treatment stimulated IL-7 production, leading to increased circulating T-cell counts. Moreover, IL-7 therapy more than abrogated the lymphopenic effect of low-dose IFN-α. Indeed, the association of both cytokines resulted in increased circulating T-cell counts, in particular in the naive compartments, as a consequence of central and peripheral homeostatic functions of the IL-7. Finally, reduced PD-1 expression by memory CD8+ T cells and transient T-cell repertoire diversification were observed under IL-7 therapy. Our data strongly suggest that IL-7 immunotherapy will be of substantial benefit in the treatment of HIV/HCV coinfection and should enhance the likelihood of HCV eradication in poorly responding patients.

Interleukin-7 (IL-7) Treatment Accelerates Neutrophil Recruitment through γδ T-Cell IL-17 Production in a Murine Model of Sepsis

The sepsis syndrome represents an improper immune response to infection and is associated with unacceptably high rates of mortality and morbidity. The interactions between T cells and the innate immune system while combating sepsis are poorly understood. In this report, we observed that treatment with the potent, antiapoptotic cytokine interleukin-7 (IL-7) accelerated neutrophil recruitment and improved bacterial clearance. We first determined that T cells were necessary for the previously observed IL-7-mediated enhanced survival. Next, IL-7 increased Bcl-2 expression in T cells isolated from septic mice as early as 3 h following treatment. This treatment resulted in increased gamma interferon (IFN-γ) and IP-10 production within the septic peritoneum together with local and systemic increases of IL-17 in IL-7-treated mice. We further demonstrate that the increase in IL-17 was largely due to increased recruitment and production by γδ T cells, which express CXCR3. Consistent with increased IL-17 production, IL-7 treatment increased CXCL1/KC production, neutrophil recruitment, and bacterial clearance. Significantly, end-organ tissue injury was not significantly different between vehicle- and IL-7-treated mice. Collectively, these data illustrate that IL-7 can mediate the cross talk between Th1 and Th17 lymphocytes during sepsis such that neutrophil recruitment and bacterial clearance is improved while early tissue injury is not increased. All together, these observations may underlay novel potential therapeutic targets to improve the host immune response to sepsis.

Enhancement of T Cell Development in Murine Bone Marrow Transplant Recipients by Transfer of the IL-7 or SCF Gene into Marrow-Derived Mesenchymal Stem Cells

The ability of the thymus to generate T cells diminishes with increasing age, the use of chemotherapy, bone marrow transplantation (BMT), anti-retroviral therapy for HIV, and graft-versus-host disease (GVHD) which can lead to a major clinical problem. Therefore, developing a clinically relevant strategy for the rapid development of T lymphocytes is crucial for treating immune deficiency. Stem cell factor (SCF: also known as kit ligand) and interleukin-7 (IL-7) are stroma–derived cytokines that induce proliferation, differentiation, and survival of developing immature T cells in the thymus. Studies have shown that administration of recombinant human IL-7 following murine BMT resulted in improved thymopoiesis and immune function. However, our previous studies have shown that that IL-7 treatment post-HSCT to enhance immune reconstitution in the allogeneic setting may have adverse effects because of the dual role of IL-7 in supporting both thymopoiesis and mature T lymphocyte expansion. Therefore it raises the question of whether IL-7 treatment after allogeneic BMT will increase the frequency or severity of GVHD. The purpose of this study was to examine whether:administration of IL-7 and SCF with infusion of mature T cell depleted (TCD) BM cells can induce enhancement of donor-derived immune reconstitution more rapidly than treatment with either cytokine alone andwhether IL-7 and SCF are synergistic and partially complementary signals for the proliferation, survival, and differentiation of immature T cells.To evaluate the combinatory effect of IL-7 and SCF in T cell development following BMT, we developed a gene therapy approach using retrovirally-mediated transduction of BM-derived mesenchymal stem cells (MSC) with the human IL-7 or murine SCF gene (soluble isoform). C57BL/6J (CD45.2) recipient mice were irradiated (1300 cGy) and co-transplanted with 1 × 10 6 T cell depleted (TCD) bone marrow cells from congenic donor B6.SJL mice (CD45.1) and different doses (0.1 × 10 6 or 0.3 × 10 6) of eGFP (control), IL-7, SCF, or combination of IL-7 and SCF MSC. At day 30 following BMT, we observed that transplantation of both IL-7 and SCF MSC resulted in significantly higher numbers of donor-derived thymocytes and peripheral lymphocytes than either IL-7 or SCF MSC transplantation alone. Most noticeably, the number of donor-derived immature and mature T cells recovered from the animals receiving transplantation of 0.1 × 10 6 IL-7 MSC and 0.3 × 10 6 SCF MSC was similar to that of animals receiving 0.3 × 10 6 IL-7 MSC alone, demonstrating that the reduced proliferative signals produced by 0.1 × 10 6 IL-7 MSC can be compensated by co-transplantation of 0.3 × 10 6 SCF MSC. Moreover, transplantation of IL-7 and SCF MSC significantly increased the number of donor-derived common lymphoid progenitors (CLP [Lin-, Sca-1 low, Thy1-, c-Kit low, IL-7R+]) in the BM, suggesting that transplanted CLPs are induced to differentiate or expand more rapidly in response to IL-7 and SCF and may have contributed to increased immune reconstitution. Collectively, our findings demonstrate that IL-7 and SCF gene therapy may be a therapeutically useful method to promote enhancement of T cell development in de novo. Furthermore, the experiments resulted in important knowledge about complementary signals provided between IL-7 and SCF, and suggest various doses of IL-7 and SCF therapy may enhance development of T cells with limited expansion of mature T cells responsible for causing GVHD in allogeneic BMT setting.

Interleukin-7 induced facilitation of immunological reconstitution of sublethally irradiated mice following treatment with alloreactive spleen cells in a murine model of B-cell leukemia/lymphoma (BCL1)

Interleukin-7 (IL-7) plays a key role in maturation and function of both T and B cells. We investigate the potential use of recombinant human IL-7 for facilitation of graft-versus-leukemia (GVL) effects mediated by T cells following transplantation in a murine model. Administration of IL-7 in vivo to allogeneic-transplanted mice improved disease-free survival: 67% of mice treated with IL-7 remained alive and disease free for more than 60 days, in comparison to 17% of the controls (P<0.05). Similar results were obtained when C57BL/6 spleen cells sensitized against irradiated B-cell leukemia (BCL(1)) cells in the presence of IL-7 were transplanted to F(1) mice, followed by IL-7 treatment in vivo. Of the BALB/c mice that received spleen cells from F(1) mice treated with IL-7 following transplantation of C57BL/6 spleen cells sensitized with irradiated BCL(1) in the presence of IL-7, only 29% developed leukemia, as compared to 79% in the control group (P<0.05). Mice treated with IL-7 showed increased splenic and thymic cellularity and improved T cell-dependent proliferative responses compared to the controls (P<0.05). IL-7 may provide a novel tool to enhance immune reconstitution following transplantation of mismatched stem cells and for enhancement of GVL effects mediated by alloreactive lymphocytes.