Selective Targeting of IL-15Rα Is Sufficient to Reduce Inflammation

Cytokines are crucial molecules for maintaining the proper functioning of the immune system. Nevertheless, a dysregulation of cytokine expression could be involved in the pathogenesis of autoimmune diseases. Interleukin (IL)-15 is a key factor for natural killer cells (NK) and CD8 T cells homeostasis, necessary to fight cancer and infections but could also be considered as a pro-inflammatory cytokine involved in autoimmune inflammatory disease, including rheumatoid arthritis, psoriasis, along with tumor necrosis factor alpha (TNF-α), IL-6, and IL-1β. The molecular mechanisms by which IL-15 exerts its inflammatory function in these diseases are still unclear. In this study, we generated an IL-15-derived molecule called NANTIL-15 (New ANTagonist of IL-15), designed to selectively inhibit the action of IL-15 through the high-affinity trimeric IL-15Rα/IL-2Rβ/γc receptor while leaving IL-15 signaling through the dimeric IL-2Rβ/γc receptor unaffected. Administrating of NANTIL-15 in healthy mice did not affect the IL-15-dependent cell populations such as NK and CD8 T cells. In contrast, we found that NANTIL-15 efficiently reduced signs of inflammation in a collagen-induced arthritis model. These observations demonstrate that the inflammatory properties of IL-15 are linked to its action through the trimeric IL-15Rα/IL-2Rβ/γc receptor, highlighting the interest of selectively targeting this receptor.

IL-15 superagonist RLI has potent immunostimulatory properties on NK cells: implications for antimetastatic treatment

Background

As the immune system is compromised in patients with cancer, therapeutic strategies to stimulate immunity appear promising, to avoid relapse and increase long-term overall survival. Interleukin-15 (IL-15) has similar properties to IL-2, but does not cause activation-induced cell death nor activation and proliferation of regulatory T cells (Treg), which makes it a serious candidate for anticancer immunotherapy. However, IL-15 has a short half-life and high doses are needed to achieve responses. Designed to enhance its activity, receptor-linker-IL-15 (RLI) (SO-C101) is a fusion molecule of human IL-15 covalently linked to the human IL-15Rα sushi+ domain currently assessed in a phase I/Ib clinical trial on patients with advanced/metastatic solid cancer.

Methods

We investigated the antimetastatic activity of RLI in a 4T1 mouse mammary carcinoma that spontaneously metastasizes and evaluated its immunomodulatory role in the metastatic lung microenvironment. We further characterized the proliferation, maturation and cytotoxic functions of natural killer (NK) cells in tumor-free mice treated with RLI. Finally, we explored the effect of RLI on human NK cells from healthy donors and patients with non-small cell lung cancer (NSCLC).

Results

RLI treatment displayed antimetastatic properties in the 4T1 mouse model. By characterizing the lung microenvironment, we observed that RLI restored the balance between NK cells and neutrophils (CD11b⁺ Ly6G^high Ly6C^low) that massively infiltrate lungs of 4T1-tumor bearing mice. In addition, the ratio between NK cells and Treg was strongly increased by RLI treatment. Further pharmacodynamic studies in tumor-free mice revealed superior proliferative and cytotoxic functions on NK cells after RLI treatment compared with IL-15 alone. Characterization of the maturation stage of NK cells demonstrated that RLI favored accumulation of CD11b⁺ CD27^high KLRG1⁺ mature NK cells. Finally, RLI demonstrated potent immunostimulatory properties on human NK cells by inducing proliferation and activation of NK cells from healthy donors and enhancing cytotoxic responses to NKp30 crosslinking in NK cells from patients with NSCLC.

Conclusions

Collectively, our work demonstrates superior activity of RLI compared with rhIL-15 in modulating and activating NK cells and provides additional evidences for a therapeutic strategy using RLI as antimetastatic molecule.

High neutralizing potency of swine glyco-humanized polyclonal antibodies against SARS-CoV-2

Heterologous polyclonal antibodies might represent an alternative to the use of convalescent plasma or monoclonal antibodies (mAbs) in coronavirus disease (COVID‐19) by targeting multiple antigen epitopes. However, heterologous antibodies trigger human natural xenogeneic antibody responses particularly directed against animal‐type carbohydrates, mainly the N‐glycolyl form of the neuraminic acid (Neu5Gc) and the α1,3‐galactose, potentially leading to serum sickness or allergy. Here, we immunized cytidine monophosphate‐N‐acetylneuraminic acid hydroxylase and α1,3‐galactosyl‐transferase (GGTA1) double KO pigs with the Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) spike receptor binding domain to produce glyco‐humanized polyclonal neutralizing antibodies lacking Neu5Gc and α1,3‐galactose epitopes. Animals rapidly developed a hyperimmune response with anti‐SARS‐CoV‐2 end‐titers binding dilutions over one to a million and end‐titers neutralizing dilutions of 1:10 000. The IgG fraction purified and formulated following clinical Good Manufacturing Practices, named XAV‐19, neutralized spike/angiotensin converting enzyme‐2 interaction at a concentration <1 μg/mL, and inhibited infection of human cells by SARS‐CoV‐2 in cytopathic assays. We also found that pig GH‐pAb Fc domains fail to interact with human Fc receptors, thereby avoiding macrophage‐dependent exacerbated inflammatory responses and a possible antibody‐dependent enhancement. These data and the accumulating safety advantages of using GH‐pAbs in humans warrant clinical assessment of XAV‐19 against COVID‐19.

High neutralizing potency of swine glyco-humanized polyclonal antibodies against SARS-CoV-2

Perfusion of convalescent plasma (CP) has demonstrated a potential to improve the pneumonia induced by SARS-CoV-2, but procurement and standardization of CP are barriers to its wide usage. Many monoclonal antibodies (mAbs) have been developed but appear insufficient to neutralize SARS-CoV-2 unless two or three of them are being combined. Therefore, heterologous polyclonal antibodies of animal origin, that have been used for decades to fight against infectious agents might represent a highly efficient alternative to the use of CP or mAbs in COVID-19 by targeting multiple antigen epitopes. However, conventional heterologous polyclonal antibodies trigger human natural xenogeneic antibody responses particularly directed against animal-type carbohydrate epitopes, mainly the N-glycolyl form of the neuraminic acid (Neu5Gc) and the Gal α1,3-galactose (αGal), ultimately forming immune complexes and potentially leading to serum sickness or allergy. To circumvent these drawbacks, we engineered animals lacking the genes coding for the cytidine monophosphate-N-acetylneuraminic acid hydroxylase (CMAH) and α1,3-galactosyl-transferase (GGTA1) enzymes to produce glyco-humanized polyclonal antibodies (GH-pAb) lacking Neu5Gc and α-Gal epitopes. We found that pig IgG Fc domains fail to interact with human Fc receptors and thereby should confer the safety advantage to avoiding macrophage dependent exacerbated inflammatory responses, a drawback possibly associated with antibody responses against SARS-CoV-2 or to avoiding a possible antibody-dependent enhancement (ADE). Therefore, we immunized CMAH/GGTA1 double knockout (DKO) pigs with the SARS-CoV-2 spike receptor-binding domain (RBD) to elicit neutralizing antibodies. Animals rapidly developed a hyperimmune response with anti-SARS-CoV-2 end-titers binding dilutions over one to a million and end-titers neutralizing dilutions of 1:10,000. The IgG fraction purified and formulated following clinical Good Manufacturing Practices, named XAV-19, neutralized Spike/angiotensin converting enzyme-2 (ACE-2) interaction at a concentration < 1μg/mL and inhibited infection of human cells by SARS-CoV-2 in cytopathic assays. These data and the accumulating safety advantages of using glyco-humanized swine antibodies in humans warranted clinical assessment of XAV-19 to fight against COVID-19.

IL-15Rα membrane anchorage in either cis or trans is required for stabilization of IL-15 and optimal signaling

Interleukin (IL)-15 plays an important role in the communication between immune cells. It delivers its signal through different modes involving three receptor chains: IL-15Rα, IL-2Rβ and IL-2Rγc. The combination of the different chains result in the formation of IL-15Rα/IL-2Rβ/γc trimeric or IL-2Rβ/γc dimeric receptors. In this study, we have investigated the role of the IL-15Rα chain in stabilizing the cytokine in the IL-2Rβ/γc dimeric receptor. By analyzing the key amino acid residues of IL-15 facing IL-2Rβ, we provide evidence of differential interfaces in the presence or in the absence of membrane-anchored IL-15Rα. Moreover, we found that the anchorage of IL-15Rα to the cell surface regardless its mode of presentation - i.e. cis or trans - is crucial for complete signaling. These observations show how the cells can finely modulate the intensity of cytokine signaling through the quality and the level of expression of the receptor chains.

Emergence of NK Cell Hyporesponsiveness after Two IL-15 Stimulation Cycles

IL-15 is a cytokine playing a crucial role in the function of immune cells, including NK and CD8 T cells. In this study, we demonstrated that in vivo, in mice, IL-15-prestimulated NK cells were no longer able to respond to a second cycle of IL-15 stimulation. This was illustrated by defects in cell maturation, proliferation, and activation, seemingly linked to the environment surrounding NK cells but not related to the presence of CD4 regulatory T cells, TGF-β, or IL-10. Moreover, NK cells from immunodeficient mice could respond to two cycles of IL-15 stimulation, whereas an adoptive transfer of CD44⁺CD8⁺ cells impaired their responsiveness to the second cycle. Conversely, in immunocompetent mice, NK cell responsiveness to a second IL-15 stimulation was restored by the depletion of CD8⁺ cells. These biological findings refine our understanding of the complex mode of action of NK cells in vivo, and they should be taken into consideration for IL-15-based therapy.

Cutting Edge: Differential Fine-Tuning of IL-2- and IL-15-Dependent Functions by Targeting Their Common IL-2/15Rβ/γc Receptor

Interleukin 2 and IL-15 are two closely related cytokines, displaying important functions in the immune system. They share the heterodimeric CD122/CD132 receptor to deliver their signals within target cells. Their specificity of action is conferred by their α receptor chains, IL-2Rα and IL-15Rα. By combining an increased affinity for CD122 and an impaired recruitment of CD132, we have generated an original molecule named IL-2Rβ/γ (CD122/CD132) inhibitor (BiG), targeting the CD122/CD132 receptor. BiG efficiently inhibited IL-15- and IL-2-dependent functions of primary cells, including CD8 T and NK cells, in vitro and in vivo. We also report a differential dynamic of action of these cytokines by highlighting a major role played by the IL-2Rα receptor. Interestingly, due to the presence of IL-2Rα, BiG had no impact on IL-2-dependent regulatory T cell proliferation. Thus, by acting as a fine switch in the immune system, BiG emphasizes the differential roles of these two cytokines.

Abstract B033: A novel IL-2 and IL-15 antagonist shifting the immune balance towards tolerance: Potential therapeutic applications

Interleukin-15 and interleukin-2 are two hematopoietic cytokines belonging to γc family and both share the IL2/15Rβ chain and the common γ chain. The IL-15Rα and IL-2Rα chains confer specific binding and signalling for IL-15 and IL-2 respectively. IL-15 and IL-2 induce T-cell proliferation, effector T-cell differentiation and memory T-cell survival. Unlike IL-15, IL-2 plays a crucial role, in development and activation of regulatory T cells, which constitutively express specific IL-2Rα chain. In order to inhibit IL-2 and IL-15 dependent effector functions, we developed an original antagonist called BinhG which target the shared IL-2/15Rβγ receptor. To characterize BinhG's mechanism and therapeutic potential, we first studied its effect in vitro on IL-15 and IL-2-induced proliferation on cell lines and peripheral blood mononuclear cells. We found that BinhG was able to inhibit IL-15 and IL-2-dependent proliferation of effector NK and CD8 T cells expressing the IL-2/15Rβγ dimeric receptor, whereas it was unable to inhibit IL-2 induced-T-reg cells due to ILtheirs IL-2Rα expression. These results were confirmed in vivo, by inhibition of IL-2 or IL-15 induced activation in mice. Moreover, after PolyIC stimulation in vivo, BinhG was able to reduce IFNγ secretion by NK cells and activation marker CD69 surface expression by CD4 T and CD8 T lymphocytes, but has no effect on T-reg cells. In the light of these observations, BinhG was evaluated in order to induce tolerance. Thus, we set up a murine model of skin graft rejection, and we observed that BinhG prolonged the skin graft survival. The use of the BinhG antagonist appears to have much promise, as it is able to shift immune response towards the tolerance side of the balance. However, further studies are needed to maximize the therapeutic outcome, by improving BinhG in vivo half-life. Moreover, it would be of interest to evaluate BinhG's effect in autoimmune contexts.

Citation Format: Meghnem Dihia, Sebastien Morisseau, Kilian Trillet, Marie Frutoso, Isabelle Barbieux, Agnes Quemener, Yannick Jacques, Erwan Mortier. A novel IL-2 and IL-15 antagonist shifting the immune balance towards tolerance: Potential therapeutic applications [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B033.

[Interleukin 2 revival: a revisited model and new therapeutic applications]

Interleukin-2, a cytokine identified as T-cell growth factor, has long been regarded as central to the development and effector activities of immune responses. Several gene knockout mouse studies and observations in humans, however, have undermined that vision, and the discovery of regulatory T cells showed that IL-2, in contrast to the accepted dogma, has the essential function of promoting (1) homeostasis and (2) the function of these T regulator cells the which, limit the action of the effector cells, in particular to prevent the autoimmune reaction drifts. This new paradigm has major implications on the use of IL-2 in therapy, and creates new strategies to manipulate the Teffectors/Tregulators balance.

IL-15 Trans-Signaling with the Superagonist RLI Promotes Effector/Memory CD8+ T Cell Responses and Enhances Antitumor Activity of PD-1 Antagonists

Tumors with the help of the surrounding environment facilitate the immune suppression in patients, and immunotherapy can counteract this inhibition. Among immunotherapeutic strategies, the immunostimulatory cytokine IL-15 could represent a serious candidate for the reactivation of antitumor immunity. However, exogenous IL-15 may have a limited impact on patients with cancer due to its dependency on IL-15Rα frequently downregulated in cancer patients. In this work, we studied the antitumor activity of the IL-15 superagonist receptor-linker-IL-15 (RLI), designed to bypass the need of endogenous IL-15Rα. RLI consists of human IL-15 covalently linked to the human IL-15Rα sushi(+) domain. In a mouse model of colorectal carcinoma, RLI as a stand-alone treatment could limit tumor outgrowth only when initiated at an early time of tumor development. At a later time, RLI was not effective, coinciding with the strong accumulation of terminally exhausted programmed cell death-1 (PD-1)(high) T cell Ig mucin-3(+) CD8(+) T cells, suggesting that RLI was not able to reactivate terminally exhausted CD8(+) T cells. Combination with PD-1 blocking Ab showed synergistic activity with RLI, but not with IL-15. RLI could induce a greater accumulation of memory CD8(+) T cells and a stronger effector function in comparison with IL-15. Ex vivo stimulation of tumor-infiltrated lymphocytes from 16 patients with renal cell carcinoma demonstrated 56% of a strong tumor-infiltrated lymphocyte reactivation with the combination anti-PD-1/RLI compared with 43 and 6% with RLI or anti-PD-1, respectively. Altogether, this work provides evidence that the sushi-IL-15Rα/IL-15 fusion protein RLI enhances antitumor activity of anti-PD-1 treatment and is a promising approach to stimulate host immunity.

Enriching a cellulose hydrogel with a biologically active marine exopolysaccharide for cell-based cartilage engineering

The development of biologically and mechanically competent hydrogels is a prerequisite in cartilage engineering. We recently demonstrated that a marine exopolysaccharide, GY785, stimulates the in vitro chondrogenesis of adipose stromal cells. In the present study, we thus hypothesized that enriching our silated hydroxypropyl methylcellulose hydrogel (Si-HPMC) with GY785 might offer new prospects in the development of scaffolds for cartilage regeneration. The interaction properties of GY785 with growth factors was tested by surface plasmon resonance (SPR). The biocompatibility of Si-HPMC/GY785 towards rabbit articular chondrocytes (RACs) and its ability to maintain and recover a chondrocytic phenotype were then evaluated in vitro by MTS assay, cell counting and qRT-PCR. Finally, we evaluated the potential of Si-HPMC/GY785 associated with RACs to form cartilaginous tissue in vivo by transplantation into the subcutis of nude mice for 3 weeks. Our SPR data indicated that GY785 was able to physically interact with BMP-2 and TGFβ. Our analyses also showed that three-dimensionally (3D)-cultured RACs into Si-HPMC/GY785 strongly expressed type II collagen (COL2) and aggrecan transcripts when compared to Si-HPMC alone. In addition, RACs also produced large amounts of extracellular matrix (ECM) containing glycosaminoglycans (GAG) and COL2. When dedifferentiated RACs were replaced in 3D in Si-HPMC/GY785, the expressions of COL2 and aggrecan transcripts were recovered and that of type I collagen decreased. Immunohistological analyses of Si-HPMC/GY785 constructs transplanted into nude mice revealed the production of a cartilage-like extracellular matrix (ECM) containing high amounts of GAG and COL2. These results indicate that GY785-enriched Si-HPMC appears to be a promising hydrogel for cartilage tissue engineering. Copyright © 2015 John Wiley & Sons, Ltd.

Highly potent anti-CD20-RLI immunocytokine targeting established human B lymphoma in SCID mouse

Rituximab (RTX), a chimeric IgG1 monoclonal antibody directed against the CD20 antigen, has revolutionized the treatment of B-cell malignancies. Nevertheless, the relapsed/refractory rates are still high. One strategy to increase the clinical effectiveness of RTX is based on antibody-cytokine fusion protein (immunocytokine; ICK) vectorizing together at the tumor site the antibody effector activities and the cytokine co-signal required for the generation of cytotoxic cellular immunity. Such ICKs linking various antibody formats to interleukin (IL)-2 are currently being investigated in clinical trials and have shown promising results in cancer therapies. IL-15, a structurally-related cytokine, is now considered as having a better potential than IL-2 in antitumor immunotherapeutic strategies. We have previously engineered the fusion protein RLI, linking a soluble form of human IL-15Rα-sushi+ domain to human IL-15. Compared with IL-15, RLI displayed better biological activities in vitro and higher antitumor effects in vivo in murine and human cancer models. In this study, we investigated the advantages of fusing RLI to RTX. Anti-CD20-RLI kept its binding capacity to CD20, CD16 and IL-15 receptor and therefore fully retained both antibody effector functions (ADCC and CDC), and the cytokine potential of RLI. In a severe combined immunodeficiency (SCID) mouse model of disseminated residual lymphoma, anti-CD20-RLI was found to induce long-term survival of 90% of mice up to at least 120 days whereas RLI and RTX, alone or in combination, just delayed the disease onset (100% of death at 28, 40 and 51 days respectively). These findings suggest that such ICK could improve the clinical efficacy of RTX, particularly in patients with refractory B-cell lymphoma.

Syndecan-1 regulates the biological activities of interleukin-34

IL-34 is a challenging cytokine sharing functional similarities with M-CSF through M-CSFR activation. It also plays a singular role that has recently been explained in the brain, through a binding to the receptor protein tyrosine phosphatase RPTPβ/ζ. The aim of this paper was to look for alternative binding of IL-34 on other cell types. Myeloid cells (HL-60, U-937, THP-1) were used as cells intrinsically expressing M-CSFR, and M-CSFR was expressed in TF-1 and HEK293 cells. IL-34 binding was studied by Scatchard and binding inhibition assays, using 125I-radiolabelled cytokines, and surface plasmon resonance. M-CSFR activation was analysed by Western blot after glycosaminoglycans abrasion, syndecan-1 overexpression or repression and addition of a blocking anti-syndecan antibody. M-CSF and IL-34 induced different patterns of M-CSFR phosphorylations, suggesting the existence of alternative binding for IL-34. Binding experiments and chondroitinase treatment confirmed low affinity binding to chondroitin sulphate chains on cells lacking both M-CSFR and RPTPβ/ζ. Amongst the proteoglycans with chondroitin sulphate chains, syndecan-1 was able to modulate the IL-34-induced M-CSFR signalling pathways. Interestingly, IL-34 induced the migration of syndecan-1 expressing cells. Indeed, IL-34 significantly increased the migration of THP-1 and M2a macrophages that was inhibited by addition of a blocking anti-syndecan-1 antibody. This paper provides evidence of alternative binding of IL-34 to chondroitin sulphates and syndecan-1 at the cell surface that modulates M-CSFR activation. In addition, IL-34-induced myeloid cell migration is a syndecan-1 dependent mechanism.

Regulation of CD4(+)NKG2D(+) Th1 cells in patients with metastatic melanoma treated with sorafenib: role of IL-15Rα and NKG2D triggering

Beyond cancer-cell intrinsic factors, the immune status of the host has a prognostic impact on patients with cancer and influences the effects of conventional chemotherapies. Metastatic melanoma is intrinsically immunogenic, thereby facilitating the search for immune biomarkers of clinical responses to cytotoxic agents. Here, we show that a multi-tyrosine kinase inhibitor, sorafenib, upregulates interleukin (IL)-15Rα in vitro and in vivo in patients with melanoma, and in conjunction with natural killer (NK) group 2D (NKG2D) ligands, contributes to the Th1 polarization and accumulation of peripheral CD4(+)NKG2D(+) T cells. Hence, the increase of blood CD4(+)NKG2D(+) T cells after two cycles of sorafenib (combined with temozolomide) was associated with prolonged survival in a prospective phase I/II trial enrolling 63 patients with metastatic melanoma who did not receive vemurafenib nor immune checkpoint-blocking antibodies. In contrast, in metastatic melanoma patients treated with classical treatment modalities, this CD4(+)NKG2D(+) subset failed to correlate with prognosis. These findings indicate that sorafenib may be used as an "adjuvant" molecule capable of inducing or restoring IL-15Rα/IL-15 in tumors expressing MHC class I-related chain A/B (MICA/B) and on circulating monocytes of responding patients, hereby contributing to the bioactivity of NKG2D(+) Th1 cells.

Antitumor activity of an immunocytokine composed of an anti-GD2 antibody and the IL-15 superagonist RLI

The use of interleukin (IL)-15 or the IL-15 superagonist RLI as immunological adjuvants presents many advantages over that of IL-2, including a reduced toxicity and an improved efficacy. We have generated an immunocytokine that specifically targets RLI to a tumor-associated antigen, namely, disialoganglioside GD2. This agent displayed robust antitumor activity in 2 syngeneic murine models of malignant disease.

Tumor targeting of the IL-15 superagonist RLI by an anti-GD2 antibody strongly enhances its antitumor potency

Immunocytokines (ICKs) targeting cytokines to the tumor environment using antibodies directed against a tumor-associated antigen often have a higher therapeutic index than the corresponding unconjugated cytokines. Various ICKs displaying significant antitumoral effects in several murine tumor models have already been developed, and some of them, in particular interleukin (IL)-2-based ICKs, are in Phase II clinical trials. Although sharing common biological activities with IL-2 in vitro, IL-15 is now considered as having a better potential in antitumor immunotherapeutical strategies and has been shown to be less toxic than IL-2 in preclinical studies. We previously developed the fusion protein RLI, linking a soluble form of human IL-15Rα-sushi+ domain to human IL-15. RLI showed better biological activities than IL-15 in vitro as well as higher antitumoral effects in vivo in murine and human cancer models. Here, we investigated, in the context of an ICK, the effect of associating RLI with an antibody targeting the GD2 ganglioside, a validated tumoral target expressed on many neurectodermal tumors. Anti-GD2-RLI fully retained the cytokine potential of RLI and the antibody effector functions (antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity). It displayed strong antitumor activities in two syngeneic cancer models in immunocompetent mice (subcutaneous EL4 and metastatic NXS2). Its therapeutic potency was higher than those of RLI and anti-GD2 alone or in combination. We suggest that this is related to its bifunctional (cytokine and antibody) nature.

Multiplexed infectious protein microarray immunoassay suitable for the study of the specificity of monoclonal immunoglobulins

Enzyme-linked immunosorbent assays (ELISAs) used to detect antibodies specific for common infectious agents such as Epstein-Barr virus (EBV), cytomegalovirus (CMV), Toxoplasma gondii (T. gondii), and hepatitis C virus (HCV) are time-consuming and require large volumes of samples, which restrict their use. We propose a new assay based on a multiplexed infectious protein (MIP) microarray combining different epitopes representative of the four germs. Antigens and lysates were printed on nitrocellulose slides to constitute the microarray. First, the microarray was incubated with human serum samples. Then, the suitability of the microarray for analysis of the specificity of purified monoclonal immunoglobulin (mc Ig) was assessed using serum and mc Ig of HCV-positive patients. Bound human immunoglobulin G (IgG) was detected using fluorescently labeled secondary antibodies, and the signals were quantified. Results obtained in serum samples with the new MIP microarray immunoassay were compared with ELISAs; we observed concordances of 95% for EBV, 93% for CMV, 91% for T. gondii, and 100% for HCV. Regarding purified mc Ig of HCV-positive patients, 3 of 3 recognized antigens printed on the microarray. Hence, the novel EBV/CMV/T. gondii/HCV MIP microarray allows simultaneous diagnosis of polyclonal and monoclonal immune response to infectious diseases using very small volume samples.

Interleukin-15 and its soluble receptor mediate the response to infliximab in patients with Crohn's disease

BACKGROUND & AIMS

Infliximab is a monoclonal antibody against tumor necrosis factor that is used to treat patients with inflammatory bowel disease. We investigated serum levels and cellular expression of interleukin (IL)-15 and its receptor (sIL-15Ralpha) in patients with Crohn's disease (CD) treated with infliximab; and the effect on sIL-15Ralpha secretion by epithelial cells.

METHODS

CD patients were given infliximab (n = 40; 3 infusions); 37 healthy controls were studied. Serum levels of IL-15, sIL-15Ralpha, and complex were determined by radioimmunoassay and cytokine levels by enzyme-linked immunosorbent assay. IL-15Ralpha and A Desintegrin and Metalloproteinase 17 levels were assessed by immunohistochemistry. Epithelial cell lines (HT-29 and Caco-2) were cultured with infliximab, adalimumab, or etanercept. Patients were classified as responders and nonresponders according to their Crohn's Disease Activity Index and clinical observations.

RESULTS

Before infliximab, IL-15 was higher in responders than in controls and nonresponders. After infliximab, IL-15 decreased in responders while remaining stable in nonresponders. sIL-15Ralpha and IL-15/sIL-15Ralpha complex levels were higher in CD than in controls and increased only in responders after infliximab. IL-15Ralpha and A Desintegrin and Metalloproteinase 17 colocalized in epithelial cells and were higher in CD patients. In vitro, infliximab but not adalimumab and etanercept induced sIL-15Ralpha secretion by epithelial cells.

CONCLUSIONS

Serum level of sIL-15Ralpha and the IL-15/sIL-15Ralpha complex increased in responder patients and the response was associated with a decrease of IL-15. Infliximab induced the release of the IL-15 receptor alpha, suggesting a specific modulation of IL-15 and its soluble receptor by reverse signaling through transmembrane tumor necrosis factor alpha.

Definition and characterization of an inhibitor for interleukin-31

Interleukin-31 (IL-31) is a recently described T cell-derived cytokine, mainly produced by T helper type 2 cells and related to the IL-6 cytokine family according to its structure and receptor. IL-31 is the ligand for a heterodimeric receptor composed of a gp130-like receptor (GPL) associated with the oncostatin M receptor (OSMR). A link between IL-31 and atopic dermatitis was shown by studying the phenotype of IL-31 transgenic mice and IL-31 gene haplotypes in patients suffering from dermatitis. In this study, we generated a potent IL-31 antagonist formed by external portions of OSMR and GPL fused with a linker. This fusion protein, OSMR-L-GPL, consisting of 720 amino acids, counteracted the binding of IL-31 to its membrane receptor complex and the subsequent signaling events involving the STATs and MAPK pathways. Neutralizing effects were found in IL-31-sensitive cell lines, including brain-derived cells and primary cultures of keratinocytes.

High antitumor activity of RLI, an interleukin-15 (IL-15)-IL-15 receptor alpha fusion protein, in metastatic melanoma and colorectal cancer

Interleukin (IL)-15 has an important role in tumor immunosurveillance and has a contemplated use in tumor immunotherapy. We have previously engineered the fusion protein RLI, composed of the NH(2)-terminal (amino acids 1-77, sushi+) domain of IL-15 receptor alpha coupled via a linker to IL-15, and shown that it displayed far better efficacy than IL-15 in vitro. In this report, we investigated in vivo whether RLI would be a better alternative than IL-15 and IL-2 for cancer treatment using two distinct animal models. B16F10 mouse melanoma cells were injected in C57BL/6 mice either i.v. or intrasplenically for lung or liver metastasis, respectively. HCT-116 human colorectal cancer cells were injected in the cecum of nude mice. We show that RLI has a higher efficiency than IL-15 or IL-2 to reduce lung and liver metastasis and enhance survival in the mouse B16F10 melanoma model, a result that was associated with a higher half-life in vivo. We also found that the antitumoral effect of RLI was completely abolished by in vivo depletion of natural killer cells using anti-asialoGM1 antibody. Moreover, RLI was also efficient to reduce by 50% tumor growth and the progression of metastasis of human colon carcinoma cells in an orthotopic nude mouse model. The fusion protein RLI has revealed strong anticancer effect in two different cancer models overcoming the limited effect of IL-15 by increasing its bioavailability and efficiency. These findings hold significant importance for the use of RLI as a potential adjuvant/therapeutic.

IL-15 trans-presentation promotes human NK cell development and differentiation in vivo

The in vivo requirements for human natural killer (NK) cell development and differentiation into cytotoxic effectors expressing inhibitory receptors for self-major histocompatibility complex class I (MHC-I; killer Ig-like receptors [KIRs]) remain undefined. Here, we dissect the role of interleukin (IL)-15 in human NK cell development using Rag2(-/-)gamma c(-/-) mice transplanted with human hematopoietic stem cells. Human NK cell reconstitution was intrinsically low in this model because of the poor reactivity to mouse IL-15. Although exogenous human IL-15 (hIL-15) alone made little improvement, IL-15 coupled to IL-15 receptor alpha (IL-15R alpha) significantly augmented human NK cells. IL-15-IL-15R alpha complexes induced extensive NK cell proliferation and differentiation, resulting in accumulation of CD16(+)KIR(+) NK cells, which was not uniquely dependent on enhanced survival or preferential responsiveness of this subset to IL-15. Human NK cell differentiation in vivo required hIL-15 and progressed in a linear fashion from CD56(hi)CD16(-)KIR(-) to CD56(lo)CD16(+)KIR(-), and finally to CD56(lo)CD16(+)KIR(+). These data provide the first evidence that IL-15 trans-presentation regulates human NK cell homeostasis. Use of hIL-15 receptor agonists generates a robust humanized immune system model to study human NK cells in vivo. IL-15 receptor agonists may provide therapeutic tools to improve NK cell reconstitution after bone marrow transplants, enhance graft versus leukemia effects, and increase the pool of IL-15-responsive cells during immunotherapy strategies.

The exon-3-encoded domain of IL-15ralpha contributes to IL-15 high-affinity binding and is crucial for the IL-15 antagonistic effect of soluble IL-15Ralpha

We previously showed that a natural soluble form of interleukin-15 (IL-15) Ralpha corresponding to the full-length ectodomain of IL-15Ralpha behaved as a potent antagonist of IL-15 action through IL-15Ralpha/beta/gamma, whereas a recombinant soluble IL-15Ralpha sushi domain did not, but instead acted as an agonist of IL-15 action through IL-15Rbeta/gamma. In order to determine precisely the molecular basis governing these antagonistic versus agonistic actions, we compared the binding properties and biological effects of recombinant soluble IL-15Ralpha (sIL-15Ralpha) species containing the sushi domain and different remaining parts of the ectodomain. We first demonstrate that the exon-3-encoded domain and, more particularly, its N-terminal 13-amino-acid (aa) peptide are important, in addition to the adjacent exon-2-encoded sushi domain, for the stabilization of the high-affinity IL-15.IL-15Ralpha complex by slowing down its dissociation rate and by contributing to about 10-20% of the free energy of interaction. We next show that all sushi-containing sIL-15Ralpha are agonists on IL-15Rbeta/gamma, coordinately increasing IL-15 binding and IL-15-induced proliferation. Their agonistic potencies are proportional to their respective affinities for IL-15. We then show that the antagonistic effect of sIL-15Ralpha in the context of IL-15Ralpha/beta/gamma is due to the 13-aa peptide that creates a sterical constraint impeding the binding of the sIL-15Ralpha.IL-15 complex to the membrane-anchored IL-15Ralpha/beta/gamma. In the frame of the soluble IL-15Ralpha sushi domain-IL-15 fusion protein that contains the 13-aa peptide, this constraint is alleviated as a result of a conformational effect due to the covalent linking of the 13-aa peptide to the N-terminus of IL-15. The soluble IL-15Ralpha sushi domain-IL-15 fusion protein is therefore able to bind and activate both the IL-15Rbeta/gamma and the IL-15Ralpha/beta/gamma receptors.

Natural killer cell trafficking in vivo requires a dedicated sphingosine 1-phosphate receptor

Consistent with their function in immune surveillance, natural killer (NK) cells are distributed throughout lymphoid and nonlymphoid tissues. However, the mechanisms governing the steady-state trafficking of NK cells remain unknown. The lysophospholipid sphingosine 1-phosphate (S1P), by binding to its receptor S1P1, regulates the recirculation of T and B lymphocytes. In contrast, S1P5 is detected in the brain and regulates oligodendrocyte migration and survival in vitro. Here we show that S1P5 was also expressed in NK cells in mice and humans and that S1P5-deficient mice had aberrant NK cell homing during steady-state conditions. In addition, we found that S1P5 was required for the mobilization of NK cells to inflamed organs. Our data emphasize distinct mechanisms regulating the circulation of various lymphocyte subsets and raise the possibility that NK cell trafficking may be manipulated by therapies specifically targeting S1P5.

Docking of human interleukin-15 to its specific receptor alpha chain: correlation between molecular modeling and mutagenesis experimental data

A structural model of the sushi domain of IL-15Ralpha was first obtained by homology modeling to study its interactions with IL-15 by means of molecular modeling, peptide scanning, and site-directed mutagenesis. From these experimental data, a putative interacting surface of IL-15Ralpha with a previously published IL-15 model was inferred: Leu25, Leu44, and Glu46 of IL-15 and Arg35 of IL-15Ralpha were found to be key interfacial residues and were subsequently used as filters for the construction of docking solutions. Human IL-15/IL-15Ralpha complexes were constructed in two stages, with a preliminary docking procedure, treating the two partners as rigid bodies and using these filters. In this first stage, two classes of docking solutions were characterized. From a topological point of view, each solution could be derived from the other by reverse orientation of one partner in relation to the other. In a second stage, several further energy refinements clearly favored one solution. Moreover, this unique docking solution was confirmed by molecular modeling of IL-15 mutants previously built and tested in our laboratory. Finally, this complex model, which is a useful tool to study the IL-15/IL-15Ralpha interface, was topologically compared to IL-2/IL-2Ralpha complexes (previous model in the literature and recent crystal structure).

Loss of oncostatin M receptor beta in metastatic melanoma cells

Oncostatin M (OSM) is an interleukin-6 (IL-6) type cytokine originally described by its capacity to inhibit melanoma proliferation in vitro. Here, the mechanisms involved in resistance to growth inhibition by OSM were analysed for the first time on a large panel of metastatic melanoma cell lines. OSM resistance did not strictly correlate with IL-6, interferon-gamma or tumor necrosis factor-alpha resistance. Rather, it correlated with a specific loss of the OSM receptor-beta (OSMRbeta) subunit, in conjunction with a lower level of histone acetylation in the OSMRbeta promoter region. Treatment of various OSM-resistant melanoma cells with the histone deacetylase inhibitor Trichostatin A increased activity and histone acetylation of the OSMRbeta promoter as well as expression of OSMRbeta mRNA and protein, allowing OSM to activate the signal transducer and activator of transcription 3 (STAT3) and to inhibit proliferation. Other defects associated with OSM resistance were identified at the level of OSMRbeta transcription or protein expression, as well as downstream of or parallel to STAT3 activation. Altogether, our results suggest a role for OSM in the prevention of melanoma progression and that metastatic melanoma cells could escape this growth control by the epigenetic silencing of OSMRbeta.

The structure of the interleukin-15 alpha receptor and its implications for ligand binding

Interleukin (IL)-15 is a member of the small four alpha-helix bundle family of cytokines. IL-15 was discovered by its ability to mimic IL-2-mediated T-cell proliferation. Both cytokines share the beta and gamma receptor chains of the IL-2 receptor for signal transduction. However, in addition, they target specific alpha chain receptors IL-15Ralpha and IL-2Ralpha, respectively. The exceptionally high affinity binding of IL-15 to IL-15Ralpha is mediated by its sushi domain. Here we present the solution structure of the IL-15Ralpha sushi domain solved by NMR spectroscopy and a model of its complex with IL-15. The model shows that, rather than the familiar hydrophobic forces dominating the interaction interface between cytokines and their cognate receptors, the interaction between the IL-15 and IL-15Ralpha complex involves a large network of ionic interactions. This type of interaction explains the exceptionally high affinity of the IL-15.IL-15Ralpha complex, which is essential for the biological effects of this important cytokine and which is not observed in other cytokine/cytokine receptor complexes.

Production of Recombinant Human Trimeric CD137L (4-1BBL)

The interaction between 4-1BB ligand (CD137L), a member of the tumor necrosis factor superfamily, and its receptor 4-1BB provides a co-stimulatory signal for T lymphocyte proliferation and survival. However, the structure of 4-1BBL has not been thoroughly investigated, and none of the human recombinant 4-1BBL molecules available have been described as capable of co-stimulating T cells. The present work provides a model of the three-dimensional structure of the tumor necrosis factor homology domain of 4-1BBL and describes the production of a recombinant human soluble 4-1BBL whose originality lies in that it contains the whole extracellular tail preceding the tumor necrosis factor homology domain and an AviTag peptide (AviTag-4-1BBL) allowing enzymatic biotinylation and multimerization via streptavidin. We provide evidence that this chimeric protein exists as a homotrimer, whereas commercial FLAG-tagged 4-1BBL does not. This resulted in a much higher affinity for 4-1BB (1.2 nM) as compared with FLAG-4-1BBL (55.2 nM). We demonstrate that the single extracellular cysteine residue in the tail (Cys-51) could form a disulfide bond, both in our recombinant protein and in physiologically expressed 4-1BBL. The mutation of this cysteine residue exerted no effect on trimerization but increased the dissociation rate of AviTag-4-1BBL from 4-1BB. In its soluble form, AviTag-4-1BBL did not stimulate purified T cells but dramatically inhibited proliferation of peripheral blood mononuclear cells stimulated with anti-CD3 mAb. In contrast, a very significant co-stimulatory effect was observed on purified T cells once AviTag-4-1BBL was immobilized onto streptavidin beads. In addition, we show that the cross-linking of two trimeric AviTag-4-1BBL molecules was the minimum step required to elicit significant costimulatory activity.

Soluble interleukin-15 receptor alpha (IL-15R alpha)-sushi as a selective and potent agonist of IL-15 action through IL-15R beta/gamma. Hyperagonist IL-15 x IL-15R alpha fusion proteins

Interleukin-15 (IL-15) is crucial for the generation of multiple lymphocyte subsets (natural killer (NK), NK-T cells, and memory CD8 T cells), and transpresentation of IL-15 by monocytes and dendritic cells has been suggested to be the dominant activating process of these lymphocytes. We have previously shown that a natural soluble form of IL-15R alpha chain corresponding to the entire extracellular domain of IL-15R alpha behaves as a high affinity IL-15 antagonist. In sharp contrast with this finding, we demonstrate in this report that a recombinant, soluble sushi domain of IL-15R alpha, which bears most of the binding affinity for IL-15, behaves as a potent IL-15 agonist by enhancing its binding and biological effects (proliferation and protection from apoptosis) through the IL-15R beta/gamma heterodimer, whereas it does not affect IL-15 binding and function of the tripartite IL-15R alpha/beta/gamma membrane receptor. Our results suggest that, if naturally produced, such soluble sushi domains might be involved in the IL-15 transpresentation mechanism. Fusion proteins (RLI and ILR), in which IL-15 and IL-15R alpha-sushi are attached by a flexible linker, are even more potent than the combination of IL-15 plus sIL-15R alpha-sushi. After binding to IL-15R beta/gamma, RLI is internalized and induces a biological response very similar to the IL-15 high affinity response. Such hyper-IL-15 fusion proteins appear to constitute potent adjuvants for the expansion of lymphocyte subsets.

Expression of a bioactive recombinant human interleukin-11 in chicken HD11 cell line

To direct the synthesis and secretion of recombinant human interleukin-11 (rhIL-11) in chicken HD11 cells, a plasmid targeting the c-lysozyme gene has been constructed which contains the mature cytokine cDNA in frame with the lysozyme leader sequence. The upregulation of rhIL-11 mediated by LPS proves the knock-in of hIL-11 cDNA in the lysozyme gene. The bioactivity of the expressed protein is demonstrated and quantified with the hIL-11 dependent 7TD1 and B9 cell lines. The electrophoretic mobility, receptor binding properties and growth promoting effect of the chicken-derived cytokine are identical to those of a rhIL-11 expressed in Escherichia coli. These results describe the secretion of a biologically active rhIL-11 expressed by an avian cellular machinery.

Natural, Proteolytic Release of a Soluble Form of Human IL-15 Receptor α-Chain That Behaves as a Specific, High Affinity IL-15 Antagonist

IL-15 and IL-2 are two structurally and functionally related cytokines whose high affinity receptors share the IL-2R beta-chain and gamma-chain in association with IL-15R alpha-chain (IL-15R alpha) or IL-2R alpha-chain, respectively. Whereas IL-2 action seems restricted to the adaptative T cells, IL-15 appears to be crucial for the function of the innate immune responses, and the pleiotropic expression of IL-15 and IL-15R alpha hints at a much broader role for the IL-15 system in multiple cell types and tissues. In this report, using a highly sensitive radioimmunoassay, we show the existence of a soluble form of human IL-15R alpha (sIL-15R alpha) that arises from proteolytic shedding of the membrane-anchored receptor. This soluble receptor is spontaneously released from IL-15R alpha-expressing human cell lines as well as from IL-15R alpha transfected COS-7 cells. This release is strongly induced by PMA and ionomycin, and to a lesser extent by IL-1 beta and TNF-alpha. The size of sIL-15R alpha (42 kDa), together with the analysis of deletion mutants in the ectodomain of IL-15R alpha, indicates the existence of cleavage sites that are proximal to the plasma membrane. Whereas shedding induced by PMA was abrogated by the synthetic matrix metalloproteinases inhibitor GM6001, the spontaneous shedding was not, indicating the occurrence of at least two distinct proteolytic mechanisms. The sIL-15R alpha displayed high affinity for IL-15 and behaved as a potent and specific inhibitor of IL-15 binding to the membrane receptor, and of IL-15-induced cell proliferation (IC(50) in the range from 3 to 20 pM). These results suggest that IL-15R alpha shedding may play important immunoregulatory functions.

Identification of an Interleukin-15α Receptor-binding Site on Human Interleukin-15

To identify the epitopes in human interleukin-15 (IL-15) that are responsible for binding to the interleukin-15 receptor alpha chain, antibody and receptor mapping by peptide scanning and site-directed mutagenesis was used. By using peptide scanning, we identified four regions in IL-15. The first region ((85)CKECEELEEKN(95)) is located in the C-D loop and is recognized by a set of non-inhibitory antibodies. The second region ((102)SFVHIVQMFIN(112)) is located in helix D and is recognized by two antibodies that are inhibitory of IL-15 bio-activity but not of IL-15 binding to IL-15Ralpha. The two remaining regions react with a recombinant soluble form of the IL-15Ralpha; the first ((44)LLELQVISL(52), peptide 1) corresponds to a sequence located in the B-helix and the second ((64)ENLII(68), peptide 2) to a sequence located in helix C. The latter is also contained in the epitope recognized by an antibody (monoclonal antibody B-E29) that prevents IL-15 binding to IL-15Ralpha. By site-directed mutagenesis, we confirmed that residues present in peptide 1 (Leu-45, Glu-46, Val-49, Ser-51, and Leu-52) and peptide 2 (Leu-66 and Ile-67) are involved in the binding of IL-15 to IL-15Ralpha. Furthermore, the results presented indicate that residues in the second peptide (Glu-64, Asn-65, and Ile-68) participate in IL-2Rbeta recruitment. This finding could have implications for the dynamics of receptor assembly. These results also indicate that the modes of interaction of IL-15 and IL-2 with their respective alpha chains are not completely analogous. Finally, some of the IL-15 mutants generated in this study displayed agonist or antagonist properties and may be useful as therapeutic agents.

Soluble mannose 6-phosphate/insulin-like growth factor II (IGF-II) receptor inhibits interleukin-6-type cytokine-dependent proliferation by neutralization of IGF-II

The calcium-independent mannose 6-phosphate receptor (CIMPR) is a receptor for multiple ligands, including leukemia inhibitory factor (LIF), an IL-6 type cytokine, and IGF-II. CIMPR targets newly synthesized ligands to lysosomes and induces internalization/degradation of secreted ligands. A natural soluble form of CIMPR (sCIMPR) neutralizes IGF-II mitogenic potency on hepatocytes and fibroblasts. Herein we show that sCIMPR also inhibits LIF-driven proliferation of myeloid and lymphoid cell lines. Similar inhibition was observed with IL-6 and IL-11, two other IL-6-type cytokines that do not interact with CIMPR. Neutralizing anti-IGF-II antibodies inhibited IL-6-, IL-11-, and LIF-driven cell proliferation to the same extent as sCIMPR, suggesting that neutralization of serum IGF-II by sCIMPR plays a major role in IL-6-type cytokine-dependent cell proliferation. Confirming this idea, ERK1/2 and AKT/protein kinase B, the kinases necessary for cell proliferation and survival, were activated by IGF-II alone or by the association of IL-6-type cytokines and IGF-II. IL-6-type cytokines alone (up to 10 ng/ml) did not activate ERK1/2 or AKT, but did activate STAT3 (signal transducer and activator of transcription 3), a transcription factor necessary for the G1 to S phase cell cycle transition. Activation of ERK1/2 and AKT by IGF-II thus appears essential to sustain cellular expansion driven by IL-6-type cytokines.

Characterization of a potent human interleukin-11 agonist

Human interleukin-11 (hIL-11) is a multi-potential cytokine that is involved in numerous biological activities, such as haematopoiesis, osteoclastogenesis, neurogenesis and female fertility, and also displays anti-inflammatory properties. IL-11 is used clinically to treat chemotherapy-induced thrombocytopenia. Because of its broad spectrum of action, improved IL-11 agonists, as well as IL-11 antagonists, could be of interest for numerous clinical applications. IL-11 signalling is dependent on the formation of a tripartite ligand-receptor complex consisting of IL-11, the IL-11R (IL-11 receptor) alpha subunit (responsible for the specificity of the interaction) and gp130 (glycoprotein 130) receptor beta subunit (responsible for signal transduction). The interaction between IL-11 and IL-11Ralpha subunit occurs at its recently assigned site I. We have designed an IL-11 mutein whose hydrophobicity at site I has been increased. The mutein has been characterized in terms of structure, affinity, specificity and bioactivity. Electrophoretic analysis, gel filtration, IR spectroscopy and CD indicate that this new protein is more compact than wild-type IL-11. It binds to IL-11Ralpha with a three-fold-enhanced affinity, and retains the ability to recruit gp130 through site II. However, analysis of its biological activity revealed a complex pattern: although this mutein is 60-400-fold more active than wild-type IL-11 on the proliferation of 7TD1 murine hybridoma cell, it is less active than IL-11 on the proliferation of B9 cells, another murine hybridoma cell line. The results are interpreted on the basis of an IL-11 conformational change induced by the mutations, and the preferential use by the mutein of another unknown transducing receptor chain.

Mutations in the immunoglobulin-like domain of gp190, the leukemia inhibitory factor (LIF) receptor, increase or decrease its affinity for LIF

The leukemia inhibitory factor (LIF) receptor comprises the low affinity binding chain gp190 and the high affinity converter gp130. The ectodomain of gp190 is among the most complex in the hematopoietin receptor family, because it contains two typical cytokine receptor homology domains separated by an immunoglobulin-like (Ig-like) domain. Human and murine gp190 proteins share 76% homology, but murine gp190 binds human LIF with a much higher affinity, a property attributed to the Ig-like domain. Using alanine-scanning mutagenesis of the Ig-like domain, we mapped a LIF binding site at its carboxyl terminus, mainly involving residue Phe-328. Mutation of selected residues into their orthologs in the murine receptor (Q251E and N321D) significantly increased the affinity for human LIF. Interestingly, these residues, although localized at both the amino and carboxyl terminus, make a spatially unique LIF binding site in a structural model of the Ig-like module. These results demonstrate definitively the role of the Ig-like domain in LIF binding and the potential to modulate receptor affinity in this family with very limited amino acid changes.

Abnormal production of interleukin (IL)-11 and IL-8 in polycythaemia vera

We studied the production of interleukin (IL)-11 and IL-8, two cytokines known to affect erythropoiesis, in polycythemia vera (PV). In vivo, IL-11 was detected more frequently in serum and bone marrow (BM) plasma of PV patients than in controls (healthy donors and patients with idiopathic erythrocytosis (IE)). In addition, serum IL-11 levels of PV patients were higher than those of controls. IL-8 was elevated in serum of both PV and IE patients (respective median levels: 38.6 and 242pg/ml, vs 4.4pg/ml for healthy donors). BM plasma IL-8 levels of PV patients (508pg/ml) were significantly higher than those of IE patients (120pg/ml). In vitro, bone marrow (BM) stromal cells (BMSC) of PV patients produced significantly more IL-11 (x6.4) and IL-8 (x8.3) than BMSC of healthy donors or IE patients. In conclusion, both IL-11 and IL-8 are overproduced in PV, apparently by BMSC; IL-8 is also overproduced in IE, by cells other than BMSC.

Engineering and use of (32)P-labeled human recombinant interleukin-11 for receptor binding studies

Human interleukin-11 (hIL-11) is a pleiotropic cytokine that is involved in numerous biological activities such as hematopoiesis, osteoclastogenesis, neurogenesis and female fertility. IL-11 is obviously a key reagent to study the IL-11 receptors. However, conventional radio-iodination techniques lead to a loss of IL-11 bioactivity. Here, we report the construction and the production of a new recombinant human IL-11 (FP Delta IL-11). In this molecule, a specific phosphorylation site (RRASVA) has been introduced at the N-terminus of rhIL-11. It can be specifically phosphorylated by bovine heart protein kinase and accordingly, easily radiolabeled with (32)P. A high radiological specific activity (250,000 c.p.m x ng(-1) of protein) was obtained with the retention of full biological activity of the protein. The binding of (32)P-labeled FP Delta IL-11 to Ba/F3 cells stably transfected with plasmids encoding human IL-11 receptors alpha and beta chains (IL-11R alpha and gp130) was specific and saturable with a high affinity as determined from Scatchard plot analysis. Availability of this new ligand should prompt further studies on IL-11R structure, expression and regulation.

Identification of agonistic and antagonistic antibodies against gp190, the leukemia inhibitory factor receptor, reveals distinct roles for its two cytokine-binding domains

The receptor for the cytokine leukemia inhibitory factor (LIF) associates the low affinity binding component gp190 and the high affinity converter gp130, both of which are members of the family of hematopoietic receptors characterized by the cytokine receptor homology (CRH) domain. The gp190 is among the very few members of this large family to contain two CRH domains. The membrane-distal one (herein called D1) is followed by an Ig-like domain, a membrane-proximal CRH domain called D2, and three type III fibronectin repeats. We raised a series of monoclonal antibodies specific for the human gp190. Among them was the blocking antibody 1C7, which was directed against the D1Ig region and which impaired the binding of LIF to gp190. Another blocking antibody, called 12D3, was directed against domain D2 and interfered with the reconstitution of the high affinity receptor complex, independently of the interaction between LIF and gp190. The blocking effect of these two antibodies concerned four cytokines known to use gp190, i.e. LIF, oncostatin M, ciliary neurotrophic factor, and cardiotrophin-1. Among 23 antibodies tested alone or in combination (two anti-D2 and 21 anti-D1Ig), only the mixture of the two anti-D2 antibodies displayed agonistic activity in the absence of the cytokine. Taken together, these results demonstrate that the two CRH domains of gp190 play different functions in ligand binding and receptor activation.

Characterization of an IL-2 mimetic with therapeutic potential

Human interleukin-2 (IL-2) interacts with two types of functional receptors (IL-2R alpha betagamma and IL-2R betagamma) and acts on a broad range of target cells involved in inflammatory reactions and immune responses. IL-2 is also used in different clinical trials aimed at improving the treatment of some cancers and the recovery of CD4 lymphocytes by HIV patients. The therapeutic index of IL-2 is limited by various side effects dominated by the vascular leak syndrome. We have shown that a chemically synthesised fragment of the IL-2 sequence can fold into a helical tetramer likely mimicking the quatemary structure of an hemopoietin. Indeed, peptide p1-30 (containing amino acids 1 to 30, including the sequence corresponding to the entire alpha helix A of IL-2) spontaneously folds into an alpha-helical homotetramer and stimulates the growth of T-cell lines expressing human IL-2R beta, whereas shorter versions of the peptide lack helical structure and are inactive. At the cellular level, p1-30 induces lymphokine-activated killer (LAK) cells and preferentially activates CD8 low lymphocytes and natural killer cells, which constitutively express IL-2R beta. A significant IFN-gamma production is also detected following p1-30 stimulation. A mutant form of p1-30 (Asp20-->Lys) which is likely unable to induce vascular leak syndrome remains capable to generate LAK cells like the original p1-30 peptide. Altogether our data suggest that p1-30 has therapeutic potential.