The soluble IL-2 receptor α/CD25 as a modulator of IL-2 function

The pleiotropic cytokine interleukin-2 (IL-2) is an integral regulator of healthy and pathological immune responses, with the most important role in regulating the homeostasis of regulatory T cells. IL-2 signalling involves three distinct receptors: The IL-2 receptor α (IL-2Rα/CD25), IL-2Rβ, and IL-2Rγ/γc . While IL-2Rβ and γc are essential for signal transduction, IL-2Rα regulates the affinity of the receptor complex towards IL-2. A soluble form of the IL-2Rα (sIL-2Rα) is present in the blood of healthy individuals and increased under various pathological conditions. Although it is known that the sIL-2Rα retains its ability to bind IL-2, it is not fully understood how this molecule affects IL-2 function and thus immune responses. Here, we summarize the current knowledge on the generation and function of the sIL-2Rα. We describe the molecular mechanisms leading to sIL-2Rα generation and discuss the different IL-2 modulating functions that have been attributed to the sIL-2Rα. Finally, we describe attempts to utilize the sIL-2Rα as a therapeutic tool.

Importance of Atezolizumab Plus Bevacizumab Combination Treatment as First-line Therapy for Immunological Changes in Patients With Unresectable Hepatocellular Carcinoma

BACKGROUND/AIM

The atezolizumab plus bevacizumab (AteBev) therapy is recommended as first-line treatment for unresectable hepatocellular carcinoma (uHCC). However, there remains a need to examine its efficacy with and without previous chemotherapy. Therefore, in patients with uHCC who underwent AteBev therapy, we aimed to clarify the effects of previous chemotherapy by examining serum immunological changes.

PATIENTS AND METHODS

We retrospectively analyzed data of 29 patients with uHCC treated by AteBev therapy as part of a prospective study and divided participants into two groups depending on whether they had received prior chemotherapy. Dynamic computed tomography was performed after 6 weeks of treatment. Blood samples were collected at baseline and after 3 weeks of treatment.

RESULTS

The group with prior treatment included 15 patients and the group without prior treatment included 14 patients. Objective response rates after six weeks of treatment were 13.3% and 28.6% in the groups with and without prior treatment, respectively. Serum levels of interleukin (IL)-6 and tumor necrosis factor-alpha showed no significant change in the group with prior treatment but increased significantly in the group without prior treatment. The percentage of regulatory T cells decreased significantly after treatment only in the group without prior treatment.

CONCLUSION

In patients with uHCC, AteBev therapy can be expected to elicit an effective immune response in patients without prior treatment, but it may not do so in patients with prior treatment. Thus, AteBev appears to be more effective when used as first-line chemotherapy.

Serum Soluble Interleukin-2 Receptor Is a Biomarker for Pneumocystis jirovecii Pneumonia among Patients with Rheumatoid Arthritis under Methotrexate Therapy

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by systemic joint inflammation and may manifest as interstitial pneumonia (IP). Methotrexate (MTX) is one of the main therapeutic drugs used for RA, but MTX could cause severe side effects, including Pneumocystis jirovecii pneumonia (PCP) and IP. Owing to similar symptoms, it is sometimes difficult to discriminate MTX therapy-associated PCP (MTX-PCP) and MTX therapy-associated IP (MTX-IP). Soluble interleukin-2 receptor (sIL-2R) is considered a marker of T-cell activation, and serum sIL-2R levels are elevated in RA and PCP. This led us to hypothesize that serum sIL-2R is a potential biomarker for discriminating MTX-PCP and MTX-IP. Accordingly, we carried out a retrospective analysis of 20 MITX-PCP cases, 30 MTX-IP cases, and as controls, 16 patients with RA-associated IP (RA-IP) and 13 patients with PCP without MTX treatment (PCP group). C-reactive protein and alveolar-arterial oxygen differences were higher in the MTX-PCP group than those in the RA-IP and MTX-IP groups. Importantly, serum levels of sIL-2R in MTX-PCP were significantly higher than those in other three groups. Based on the receiver operating characteristic curve, the cut-off level of sIL-2R resulting in the highest diagnostic accuracy for MTX-PCP was 1,311.5 U/mL, discriminating between MTX-PCP and other groups with 91.7% sensitivity and 78.6% specificity. Thus, patients with MTX-PCP show a higher degree of systemic inflammation, severe hypoxemia, and increased sIL-2R levels compared with those in MTX-IP cases. In conclusion, serum sIL-2R could be a biomarker for PCP diagnosis among patients with RA under MTX therapy.

Relationship between Multiple Sclerosis-Associated IL2RA Risk Allele Variants and Circulating T Cell Phenotypes in Healthy Genotype-Selected Controls

Single nucleotide polymorphisms (SNPs) in or near the IL2RA gene, that encodes the interleukin-2 (IL-2) receptor α (CD25), are associated with increased risk of immune-mediated diseases including multiple sclerosis (MS). We investigated how the MS-associated IL2RA SNPs rs2104286 and rs11256593 are associated with CD25 expression on T cells ex vivo by multiparameter flow cytometry in paired genotype-selected healthy controls. We observed that MS-associated IL2RA SNPs rs2104286 and rs11256593 are associated with expression of CD25 in CD4⁺ but not CD8⁺ T cells. In CD4⁺ T cells, carriers of the risk genotype had a reduced frequency of CD25⁺ T_FH1 cells (p = 0.001) and an increased frequency of CD25⁺ recent thymic emigrant cells (p = 0.006). Furthermore, carriers of the risk genotype had a reduced surface expression of CD25 in post-thymic expanded CD4⁺ T cells (CD31⁻CD45RA⁺), CD39⁺ T_Reg cells and in several non-follicular memory subsets. Our study found novel associations of MS-associated IL2RA SNPs on expression of CD25 in CD4⁺ T cell subsets. Insight into the associations of MS-associated IL2RA SNPs, as these new findings provide, offers a better understanding of CD25 variation in the immune system and can lead to new insights into how MS-associated SNPs contribute to development of MS.

Prophylactic and Therapeutic Effects of Interleukin-2 (IL-2)/Anti-IL-2 Complexes in Systemic Lupus Erythematosus-Like Chronic Graft-Versus-Host Disease

Murine chronic graft-versus-host-disease (cGvHD) induced by injection of parental lymphocytes into F1 hybrids results in a disease similar to systemic lupus erythematosus. Here, we have used DBA/2 T cell injection into (C57BL/6 × DBA/2)F1 (BDF1) mice as a model system to test the prophylactic and therapeutic effects of interleukin-2 (IL-2)/anti-IL-2 immune complexes on the course of cGvHD. Our findings demonstrate that pretreatment with Treg inducing JES6/IL-2 complexes render BDF1 mice largely resistant to induction of cGvHD, whereas pretreatment with CD8⁺ T cell/NK cell inducing S4B6/IL-2 complexes results in a more severe cGvHD. In contrast, treatment with JES6/IL-2 complexes 4 weeks after induction had no beneficial effect on disease symptoms. However, similar treatment with S4B6/IL-2 complexes led to a significant amelioration of the disease. This therapeutic effect seems to be mediated by donor CD8⁺ T cells. The fact that a much stronger cGvHD is induced in BDF1 mice depleted of donor CD8⁺ T cells strongly supports this conclusion. The contrasting effects of the two different IL-2 complexes are likely due to different mechanisms.

Daclizumab: Development, Clinical Trials, and Practical Aspects of Use in Multiple Sclerosis

Daclizumab is a humanized monoclonal antibody directed towards CD25, the alpha subunit of the high-affinity interleukin (IL)-2 receptor. Daclizumab exerts its effects via multiple mechanisms, including reduction of IL-2-mediated lymphocyte activation and upregulation of CD56-bright natural killer cells. Intravenous daclizumab (Zenapax™) was initially approved for prevention of rejection in renal transplant. In subsequent early testing, followed by larger-scale phase II and phase III trials, both intravenous and subcutaneous daclizumab have demonstrated clinical efficacy in the treatment of multiple sclerosis. The subcutaneous daclizumab prepared by high-yield process was utilized in the advanced phase II and phase III trials (SELECT and DECIDE). High-yield process daclizumab is now approved by the US Food and Drug Administration for relapsing-remitting multiple sclerosis, and is now formally termed daclizumab beta (DAC-beta; Zinbryta™). In this review, the early development of anti-IL-2 receptor alpha monoclonal antibodies and the properties of IL-2 and its receptor are discussed, and diverse mechanisms of action for daclizumab are presented. Results of the CHOICE, SELECT, and DECIDE clinical trials are discussed in detail. Adverse events observed in clinical trials included cutaneous reactions, liver enzyme elevations, infections, and autoimmune phenomena. DAC-beta is a monthly, patient-administered subcutaneous injection that requires enrollment in a safety monitoring (REMS) program for monthly liver function testing. Prescribers should be aware of the potential adverse events, as early recognition and management is important, particularly in cutaneous and hepatic reactions. Continued clinical experience with DAC-beta, including observations from the REMS program, will define its place in the armamentarium of immunotherapeutics for relapsing-remitting multiple sclerosis.

The emerging role of anti-CD25 directed therapies as both immune modulators and targeted agents in cancer

CD25 (also termed IL2RA) forms one component of the high-affinity heterotrimeric interleukin 2 (IL2) receptor on activated T cells. Its affinity for IL2 and cellular function are tightly regulated and vary in different cell types. The high frequency of CD25 on the surface of many different haematological tumour cells is now well established and, apart from its prognostic significance, CD25 may be present on leukaemic stem cells and enable oncogenic signalling pathways in leukaemic cells. Additionally, high CD25 expression in activated circulating immune cells and Tregs is a factor that has already been exploited by IL2 immunotherapies for treatment of tumours and autoimmune disease. The relative clinical safety and efficacy of administering anti-CD25 radioimmunoconjugates and immunotoxins in various haematological tumour indications has been established and clinical trials of a novel CD25-directed antibody drug conjugate are underway.

DAB389IL-2 recombinant fusion toxin effect on lymphocyte- and macrophage-producing cytokine subpopulation cells in experimentally induced demyelinating disease in mice

CONTEXT

We have reported previously that DAB389IL-2 recombinant fusion toxin targets IL-2R bearing CD4⁺ cells, and suppresses demyelinating disease in acute (A) - and chronic (C) - experimental autoimmune encephalomyelitis (EAE) animal models of multiple sclerosis.

OBJECTIVES

The present study was undertaken to investigate the effect of DAB389IL-2 treatment on various cytokine-secreting cell populations in A-EAE and C-EAE mice.

MATERIALS AND METHODS

The effects of DAB389IL-2 at doses of 200-, 800-, or 1600 kU administered i.v. on days 11-13 and 15 on the clinical score and cytokine-secreting cell populations were examined using flow cytometry.

RESULTS

C-EAE mice treated with 1600kU DAB389IL-2, but not A-EAE mice treated with 800 kU had significantly reduced disease. The CD3+CD25+ sub-population in spleens and spinal cords of A-EAE mice treated with 800 kU DAB389IL-2 a was increased, whereas in C-EAE mice treated with 1600 kU this population was increased. DAB₃₈₉IL-2 treatment reduced CD3⁺CD4⁺, CD3⁺CD8⁺, CD4⁺CD8⁺, CD3⁺IL-2⁺, CD3⁺IFN-γ⁺ and CD3⁺TNF-α⁺ T cell subpopulations in the spinal cord in A-EAE, and C-EAE mice on day 16. CD11b+ macrophages that were IL-2-, IFN-γ-, and TNF-α- positive were reduced in A-EAE mice. DAB389IL-2 treatment reduced CD19⁺ B-cells positive for IL-2 or CD11b⁺ in the spinal cord in acute and chronic disease. DAB389IL-2 treatment also reduced lymph node CD3⁺CD8⁺, CD4⁺CD8⁺, CD3⁺CD25⁺ populations on day 16, and lymph node CD3⁺IL-10⁺ and peripheral blood CD3⁺CD25⁺ populations on day 24.

DISCUSSION AND CONCLUSIONS

Our study demonstrates that DAB₃₈₉IL-2 fusion toxin suppresses EAE in a dose-dependent manner, and alters inflammatory cell sub-populations during disease development.

Daclizumab for the treatment of relapsing-remitting multiple sclerosis

INTRODUCTION

Multiple sclerosis (MS) is a common inflammatory disease of the central nervous system. Over the last two decades, the number of therapeutic options for the treatment of relapsing remitting MS (RRMS) has been constantly growing, providing new treatment options to patients. Areas covered: Herein, the authors review the recently approved monoclonal antibody daclizumab for the treatment of RRMS. Based on original articles, they discuss its mode of action and evaluate its efficacy and safety profile compared to other available agents. Expert opinion: The IL-2 receptor modulator daclizumab is a new highly effective agent for the treatment of RRMS with novel immunomodulatory properties. Compared to interferon-beta i.m., daclizumab is more effective in reducing relapse rates and MRI activity. However, its use is limited by the risk of autoimmune disorders and hepatotoxicity. Similar to other monoclonal antibodies for RRMS, therapy with daclizumab needs a strict preselection and monitoring of patients based on individual risk benefit assessment. Given its substantial effectiveness, daclizumab can be an attractive option for patients with highly active MS.

Immunogenic and tolerogenic effects of the chimeric IL-2-diphtheria toxin cytocidal agent Ontak® on CD25+ cells

Ontak^®, a conjugate between IL-2 and a diphtheria toxin fragment, was recently investigated in cancer clinical trials aiming to kill CD25⁺ regulatory T cells (T_regs). We found that the activity of Ontak^® was more complex on T_regs and conventional T cells (T_convs) than anticipated, including a novel strong influence on dendritic cells (DCs).

A review of peripheral biomarkers in major depression: the potential of inflammatory and oxidative stress biomarkers

Biomarkers are regularly used in medicine to provide objective indicators of normal biological processes, pathogenic processes or pharmacological responses to therapeutic interventions, and have proved invaluable in expanding our understanding and treatment of medical diseases. In the field of psychiatry, assessment and treatment has, however, primarily relied on patient interviews and questionnaires for diagnostic and treatment purposes. Biomarkers in psychiatry present a promising addition to advance the diagnosis, treatment and prevention of psychiatric diseases. This review provides a summary on the potential of peripheral biomarkers in major depression with a specific emphasis on those related to inflammatory/immune and oxidative stress/antioxidant defences. The complexities associated with biomarker assessment are reviewed specifically around their collection, analysis and interpretation. Focus is placed on the potential of peripheral biomarkers to aid diagnosis, predict treatment response, enhance treatment-matching, and prevent the onset or relapse of major depression.

Fine epitope specificity of antibodies against interleukin-2 explains their paradoxical immunomodulatory effects

The functional dichotomy of antibodies against interleukin-2 (IL-2) is thought to depend upon recognition of different cytokine epitopes. Beyond functional studies, the only molecular evidence obtained so far located the epitopes recognized by the immunoenhancing antibodies S4B6 and JES6-5H4 within the predicted interface of IL-2 with the α receptor subunit, explaining the preferential stimulation of effector cells displaying only β and γ receptor chains. A consistent functional map of the epitope bound by the immunoregulatory antibody JES6-1A12 has now been delineated by screening the interactions of phage-displayed antigen variants (with single and multiple mutations) and antigen mimotopes. The target determinant resides in a region between the predicted interfaces with α and β/γ receptor subunits, supporting the dual inhibitory role of the antibody on both interactions. Binding by JES6-1A12 would thus convert complexed IL-2 into a very weak agonist, reinforcing the advantage of T regulatory cells (displaying the high affinity αβγ heterotrimeric receptor) to capture the cytokine by competition and expand over effector cells, ultimately resulting in the observed strong tolerogenic effect of this antibody. Detailed knowledge of the epitopes recognized by anti-IL-2 antibodies with either immunoenhancing or immunoregulatory properties completes the molecular scenario underlying their use to boost or inhibit immune responses in multiple experimental systems. The expanded functional mapping platform now available could be exploited to study other interactions involving related molecular pairs with the final goal of optimizing cytokine and anti-cytokine therapies.

Interleukin-2 and its receptor complex (alpha, beta and gamma chains) in in situ and infiltrative human breast cancer: an immunohistochemical comparative study

INTRODUCTION

The presence and distribution of interleukin-2 (IL-2) and its receptor complex (Ralpha, Rbeta, Rgamma) were studied in 52 women who were clinically and histopathologically diagnosed with breast tumours (17 in situ and 35 infiltrating), and in 13 women with benign fibrocystic lesions in the breast.

METHODS

Immunohistochemistry with antibodies against IL-2, IL-2Ralpha, IL-2Rbeta and IL-2Rgamma was used. A comparative semiquantitative immunohistochemical study between the three breast groups (fibrocystic lesions, in situ tumours and infiltrating tumours) was performed.

RESULTS

IL-2 and its three receptor chains were immunodetected in the cytoplasm of epithelial cells. The three receptor chains were also detected on the cell surface. In fibrocystic lesions, immunoreactions to IL-2 (38.5% of cases), IL-2Ralpha (53.8%) and IL-2Rbeta (30.8%) were very weak, whereas immunoreaction to IL-2Rgamma (46.1%) was somewhat more intense. In in situ tumours, the percentages of cases that immunostained positively for IL-2 and its three receptor chains were similar to those observed in fibrocystic lesions, but immunostainings of the four antibodies were more intense. In infiltrative tumours, the percentages of positively stained cases and also immunostaining intensities were approximately twice that found for in situ tumours. Within infiltrating tumours, the percentage of cases showing immunoreaction to IL-2 and their three receptor chains was higher in the patients with lymph node infiltration at the time of surgery.

CONCLUSION

The development of breast tumour is associated with an increased expression of IL-2 and its three receptor chains, and this expression also seems to be associated with the malignancy of the tumour.

NMR characterization of interleukin-2 in complexes with the IL-2Ralpha receptor component, and with low molecular weight compounds that inhibit the IL-2/IL-Ralpha interaction

Nuclear magnetic resonance (NMR) methods were employed to study the interaction of the cytokine Interleukin-2 (IL-2) with the alpha-subunit of its receptor (IL-2Ralpha), and to help understand the behavior of small molecule inhibitors of this interaction. Heteronuclear (1)H-(15)N HSQC experiments were used to identify the interaction surface of (15)N-enriched Interleukin-2 ((15)N-IL-2) in complex with human IL-2Ralpha. In these experiments, chemical shift and line width changes in the heteronuclear single-quantum coherence (HSQC) spectra upon binding of (15)N-IL-2 enabled classification of NH atoms as either near to, or far from, the IL-2Ralpha interaction surface. These data were complemented by hydrogen/deuterium (H/D) exchange measurements, which illustrated enhanced protection of slowly-exchanging IL-2 NH protons near the site of interaction with IL-2Ralpha. The interaction surface defined by NMR compared well with the IL-2Ralpha binding site identified previously using mutagenesis of human and murine IL-2. Two low molecular weight inhibitors of the IL-2/IL-2Ralpha interaction were studied: one (a cyclic peptide derivative) was found to mimic a part of the cytokine and bind to IL-2Ralpha; the other (an acylphenylalanine derivative) was found to bind to IL-2. For the interaction between IL-2 and the acylphenylalanine, chemical shift perturbations of (15)N and (15)NH backbone resonances were tracked as a function of ligand concentration. The perturbation pattern observed for this complex revealed that the acylphenylalanine is a competitive inhibitor-it binds to the same site on IL-2 that interacts with IL-2Ralpha.

Increased proliferation of a human breast carcinoma cell line by recombinant interleukin-2

Two adenocarcinoma cell lines, Breast M25-SF and Breast M, were established from tumor tissue resected surgically from a patient with breast cancer. One, Breast M25-SF, expresses interleukin-2 receptor (IL-2R) on the cell surface and the other, Breast M does not. The effects of recombinant interleukin-2 (rIL-2) on the proliferation of these cell lines were investigated. The growth of Breast M25-SF was significantly promoted by rIL-2 ranging from 1.25 U/ml to 640 U/ml. Anti-CD25 (Tac) antibody significantly blocked the growth enhancement of Breast M25-SF by rIL-2. Breast M, however, did not respond to rIL-2. To confirm more directly the promotion of Breast M25-SF growth by rIL-2, cloning of IL-2 responders from parent Breast M25-SF cells was carried out by limiting dilution without feeder cells in 96-well microplates. No colony formation was found in 24 wells without rIL-2. Eleven, 13 and 6 clones were established from groups of 24 wells containing rIL-2 at 200, 20 and 2 U/ml respectively. All of the clones expressed IL-2R and respond to rIL-2. By using a sensitive polymerase chain reaction technique, we demonstrated that Breast M25-SF but not Breast M expressed IL-2 mRNA, and IL-2 secretion from Breast M25-SF but not Breast M was also confirmed by radioimmunoassay. These findings suggest a role for IL-2 in autocrine support of Breast M25-SF growth. IL-2 may play an important role in the growth control of breast carcinoma cells.

Production of interleukin-2 (IL-2) and expression of IL-2 receptor in patients with IgA nephropathy

BACKGROUND

IL-2 production has been measured in several disease including type I diabetes mellitus, systemic lupus erythematosus, acquired immunodeficiency syndrome and active pulmonary sarcoidosis and its pathogenetic role was suggested. In IgA nephropathy, altered T cell subsets were reported to be associated with increased synthesis of IgA. The altered IL-2 production and the expression of IL-2 receptor might be involved in the pathogenesis of IgA nephropathy.

METHODS

To investigate the role of T cell mediated immunity in the pathogenesis of IgA nephropathy, the immune parameters such as T cell subsets, NK cell activity, interleukin-2 (IL-2) production and IL-2 receptor expression on peripheral blood mononuclear cells (PBMC) were measured before and/or after phytohemagglutinin (PHA) stimulation in 15 patients with IgA nephropathy. Age and sex matched 15 healthy controls and the correlations between the IL-2 production and immune parameters were evaluated.

RESULTS

The mean percentages of T helper/inducer cells (CD4), T suppressor/cytotoxic cells (CD8) and the CD4/CD8 ratio of the patients were not different from those of controls and the proportions of CD8 CD11b cell in the patients (21.0 +/- 3.6%) were significantly lower than those in controls (30.5 +/- 5.3%) (p < 0.005). The production of IL-2 by fresh PBMC of both patients and controls was in undetectable ranges. The production of IL-2 by PHA stimulated PBMC of patients was significantly higher than that of controls (140.03 +/- 43.2 U/ml vs 106.5 +/- 42.1 U/ml, p < 0.05). The proportions of lymphocytes expressing the IL-2 receptor (CD25) before the stimulation with PHA in patients were 1.22 +/- 1.00 percent and were not different from those in controls (1.12 +/- 0.78 percent). The correlations between the production of IL-2 and the concentrations of serum IgA, the degrees of histologic alterations and the proportions of CD8 and CD8CD11b cells were not significant. There was a weak tendency of a positive correlation (p < 0.1) between the production of IL-2 and the proportions of CD4 cells, and the CD4/CD8 ratio showed a significant correlation with the production of IL-2 (p < 0.05). After PHA stimulation, the mean percentages of lymphocytes expressing the IL-2 receptors in patients were increased to 47.6 +/- 8.9 percents which is higher than those (40.4 +/- 9.9%) in controls (p < 0.05). The NK cell activity of the patients was higher than that of controls (75.6 +/- 19.6% vs 56.1 +/- 16.2%, p < 0.005), and was well correlated with the production of IL-2 by PBMC (r = 0.89, p < 0.05).

CONCLUSIONS

It seemed that patients with IgA nephropathy have an 'latent' cellular immunoregulatory dysfunction that becomes apparent on the stimulation of extrinsic antigens or mitogens.

ANTI-IL-2 Receptor Antibody Treatment for Lymphoproliferative Disease: Transient Response in A Case of Ki-1+ Anaplastic Large Cell Lymphoma

Most cases of Ki-1 + anaplastic large cell lymphomas (ALCL) express the CD25 antigen, and we have recently shown that IL-2 producing cells can also be detected in these lymphomas. The latter cells may thus constitute targets for anti-CD25 Mab treatment. In one patient with a chemoresistant disseminated Ki-1 + ALCL such a therapeutic approach was undertaken. We report the dramatic antitumoral effect of anti-CD25 Mab obtained in this patient. This confirms the observation, previously reported in adult T cell leukemia, showing that this therapeutic regimen is also efficient in CD25 + solid tumors.