The structure of IL2 bound to the three chains of the IL2 receptor and how signaling occurs

Adoptive Cell Therapy for Solid Tumors: Current Status in Melanoma and Next-Generation Therapies

Lifileucel or TIL has recently been FDA approved for metastatic melanoma patients as first cell therapy for a solid tumor. We discuss roll-out of TIL as new SOC and other upcoming new cell therapies.

A CD25-biased interleukin-2 for autoimmune therapy engineered via a semi-synthetic organism

BACKGROUND

Natural cytokines are poorly suited as therapeutics for systemic administration due to suboptimal pharmacological and pharmacokinetic (PK) properties. Recombinant human interleukin-2 (rhIL-2) has shown promise for treatment of autoimmune (AI) disorders yet exhibits short systemic half-life and opposing immune responses that negate an appropriate therapeutic index.

METHODS

A semi-synthetic microbial technology platform was used to engineer a site-specifically pegylated form of rhIL-2 with enhanced PK, specificity for induction of immune-suppressive regulatory CD4 + T cells (Tregs), and reduced stimulation of off-target effector T and NK cells. A library of rhIL-2 molecules was constructed with single site-specific, biorthogonal chemistry-compatible non-canonical amino acids installed near the interface where IL-2 engages its cognate receptor βγ (IL-2Rβγ) signaling complex. Biorthogonal site-specific pegylation and functional screening identified variants that retained engagement of the IL-2Rα chain with attenuated potency at the IL-2Rβγ complex.

RESULTS

Phenotypic screening in mouse identifies SAR444336 (SAR'336; formerly known as THOR-809), rhIL-2 pegylated at H16, as a potential development candidate that specifically expands peripheral CD4+ Tregs with upregulation of markers that correlate with their suppressive function including FoxP3, ICOS and Helios, yet minimally expands CD8 + T or NK cells. In non-human primate, administration of SAR'336 also induces dose-dependent expansion of Tregs and upregulated suppressive markers without significant expansion of CD8 + T or NK cells. SAR'336 administration reduces inflammation in a delayed-type hypersensitivity mouse model, potently suppressing CD4+ and CD8 + T cell proliferation.

CONCLUSION

SAR'336 is a specific Treg activator, supporting its further development for the treatment of AI diseases.

Tumor-Infiltrating Lymphocyte and Other Cell Therapies for Metastatic Melanoma

ABSTRACT

Major progress in prolonging survival of patients with advanced melanoma has been made in the past decade because of the development and approval of immune checkpoint inhibitor and targeted therapies. However, for nonresponding or relapsing patients, their prognosis is still dismal. Based on clinical trial data, treatment with adoptive cell therapies holds great promise. In patients with metastatic melanoma progressing on or nonresponsive to single-agent anti-programmed cell death 1, infusion of tumor-infiltrating lymphocytes can produce responses in up to half of patients, with durable complete responses in up to 20%. Genetic modification of peripheral blood T cells with T-cell receptors derived from tumor-specific T cells, or with chimeric antigen receptors, has the potential to further improve treatment outcomes in this refractory population. In this review, we will discuss the historical development, current status, and future perspectives of adoptive T-cell therapies in melanoma.

Distinct transcriptomic and epigenomic modalities underpin human memory T cell subsets and their activation potential

Human memory T cells (MTC) are poised to rapidly respond to antigen re-exposure. Here, we derived the transcriptional and epigenetic programs of resting and ex vivo activated, circulating CD4+ and CD8+ MTC subsets. A progressive gradient of gene expression from naïve to TCM to TEM is observed, which is accompanied by corresponding changes in chromatin accessibility. Transcriptional changes suggest adaptations of metabolism that are reflected in altered metabolic capacity. Other differences involve regulatory modalities comprised of discrete accessible chromatin patterns, transcription factor binding motif enrichment, and evidence of epigenetic priming. Basic-helix-loop-helix factor motifs for AHR and HIF1A distinguish subsets and predict transcription networks to sense environmental changes. Following stimulation, primed accessible chromatin correlate with an augmentation of MTC gene expression as well as effector transcription factor gene expression. These results identify coordinated epigenetic remodeling, metabolic, and transcriptional changes that enable MTC subsets to ultimately respond to antigen re-encounters more efficiently.

A high-throughput, 28-day, microfluidic model of gingival tissue inflammation and recovery

Nearly half of American adults suffer from gum disease, including mild inflammation of gingival tissue, known as gingivitis. Currently, advances in therapeutic treatments are hampered by a lack of mechanistic understanding of disease progression in physiologically relevant vascularized tissues. To address this, we present a high-throughput microfluidic organ-on-chip model of human gingival tissue containing keratinocytes, fibroblast and endothelial cells. We show the triculture model exhibits physiological tissue structure, mucosal barrier formation, and protein biomarker expression and secretion over several weeks. Through inflammatory cytokine administration, we demonstrate the induction of inflammation measured by changes in barrier function and cytokine secretion. These states of inflammation are induced at various time points within a stable culture window, providing a robust platform for evaluation of therapeutic agents. These data reveal that the administration of specific small molecule inhibitors mitigates the inflammatory response and enables tissue recovery, providing an opportunity for identification of new therapeutic targets for gum disease with the potential to facilitate relevant preclinical drug efficacy and toxicity testing.

Cordycepin Enhances the Cytotoxicity of Human Natural Killer Cells against Cancerous Cells

Cancer treatment with natural killer (NK) cell immunotherapy is promising. NK cells can recognize and kill cancer cells without sensitization, making them a potential cancer treatment alternative. To improve clinical efficacy and safety, more research is needed. Enhancing NK cell function improves therapeutic efficacy. Due to its potent apoptosis induction, Cordycepin, a bioactive compound from Cordyceps spp., inhibits cancer cell growth. Cordycepin has immunoregulatory properties, making it a promising candidate for combination therapy with NK cell-based immunotherapy. Cordycepin may enhance NK cell function and have clinical applications, but more research is needed. In this study, cordycepin treatment of NK-92 MI cells increased THP-1 and U-251 cell cytotoxicity. Cordycepin also significantly increased the mRNA expression of cytokine-encoding genes, including tumour necrosis factor (TNF), interferon gamma (IFNG), and interleukin 2 (IL2). NK-92 MI cells notably secreted more IFNG and granzyme B. Cordycepin also decreased CD27 and increased CD11b, CD16, and NKG2D in NK-92 MI cells, which improved its anti-cancer ability. In conclusion, cordycepin could enhance NK cell cytotoxicity against cancerous cells for the first time, supporting its use as an alternative immunoactivity agent against cancer cells. Further studies are needed to investigate its efficacy and safety in clinical settings.

Imaging of Activated T Cells

The adaptive immune response plays a critical role in detecting, eliminating, and creating a memory toward foreign pathogens and malignant cells. Demonstration of the specific and effective target killing of T cells in cancer has reignited interest in the study and therapeutic manipulation of the interaction between tumor and immune system. To both improve therapeutic efficacy and reduce adverse events, accurate monitoring of the activation of T cells is required. Several approaches to monitoring not just the presence, but importantly the activation, of T cells have been developed. Here, we review the recent advances in T-cell activation imaging and future directions for potential implementation into clinical utility.

Engineering IL-2 for immunotherapy of autoimmunity and cancer

Preclinical studies of the T cell growth factor activity of IL-2 resulted in this cytokine becoming the first immunotherapy to be approved nearly 30 years ago by the US Food and Drug Administration for the treatment of cancer. Since then, we have learnt the important role of IL-2 in regulating tolerance through regulatory T cells (Treg cells) besides promoting immunity through its action on effector T cells and memory T cells. Another pivotal event in the history of IL-2 research was solving the crystal structure of IL-2 bound to its tripartite receptor, which spurred the development of cell type-selective engineered IL-2 products. These new IL-2 analogues target Treg cells to counteract the dysregulated immune system in the context of autoimmunity and inflammatory disorders or target effector T cells, memory T cells and natural killer cells to enhance their antitumour responses. IL-2 biologics have proven to be effective in preclinical studies and clinical assessment of some is now underway. These studies will soon reveal whether engineered IL-2 biologics are truly capable of harnessing the IL-2-IL-2 receptor pathway as effective monotherapies or combination therapies for autoimmunity and cancer.

Targeted Association and Intracellular Delivery of Nanocargoes into Primary T Lymphocytes via Interleukin-2 Receptor-Mediated Endocytosis

Despite the tremendous progress in immunotherapy regimens using T cells, efforts to modulate the functions of T cells are still significantly hampered by the lack of reliable methods to deliver various cargoes into the T cells. This ongoing challenge originates from the intrinsic resistance of T cells in taking up exogenous materials. Here, we strategically aimed to hijack the natural endocytosis of Interleukin-2 (IL2) by the activated T cells for the targeted association and intracellular delivery of cargoes in varying sizes. First, we carefully characterized the fluctuations in the expression levels of IL2 receptor (IL2R) subunits (CD25, CD122, and CD132) during the murine primary T cell cultures over 12 days. We identified the highest fraction of T cells that would express the high-affinity trimeric IL2R on Day 3. By examining the association and uptake efficiencies of IL2 molecules that are biotinylated via either random lysine-targeting chemical reaction (using NHS-PEG4-Biotin) or site-specific enzymatic modification (using Avitag sequence), we demonstrated that the most efficient delivery of cargo can be achieved by C-terminal conjugation. Upon confirmation of successful delivery of a small model cargo, streptavidin, we employed superparamagnetic iron oxide nanoparticles (SPIONs) as bigger model cargoes having core diameters of 50, 100, and 200 nm. We examined the association and intracellular delivery of the IL2-conjugated nanocargoes using flow cytometry, confocal laser scanning microscopy, and transmission electron microscopy. While cargoes of all tested sizes were successfully associated with the IL2R-expressing T cells in comparable efficiencies, the uptake efficiencies were inversely proportional to the sizes of the cargoes. Nevertheless, our current definitive report confirms that nanocargoes with a practical maximum size limit around 100-200 nm can be intracellularly delivered into activated primary T cells using IL2R-mediated endocytosis, which opens a new horizon for engineering and manufacturing of various T cell immunotherapeutics.

PRDM1 decreases sensitivity of human NK cells to IL2-induced cell expansion by directly repressing CD25 (IL2RA)

IL2 receptor signaling is crucial for human NK cell activation and gain of effector functions. The molecular mechanisms involved in termination of IL2 activation are largely unknown in human NK cells. PR/SET domain 1 was previously reported to decrease cell growth and increase apoptosis in an IL2-dependent manner in malignant NK cell lines, suggesting the possibility of down-regulation of IL2 signaling pathway gene(s) through direct transcriptional repression. Using ChIP-Seq, we identified a PRDM1 binding site on the first intron of CD25 (IL2RA), which codes for the IL2 receptor subunit regulating sensitivity to IL2 signaling, in primary NK cells activated with engineered K562 cells or IL2. Ectopic expression of PRDM1 down-regulated CD25 expression at transcript and protein levels in two PRDM1 nonexpressing NK cell lines. shRNA-mediated knockdown of CD25 in two malignant NK cell lines led to progressive depletion of NK cells in low IL2 concentrations. By contrast, ectopic CD25 expression in primary human NK cells led to progressive increase in cell number in CD25-transduced cells in low IL2 concentrations. Altogether these results reveal a pivotal role of PRDM1 in inhibition of IL2-induced NK cell expansion through direct repression of CD25 in activated human NK cells. These observations provide additional support for the role of PRDM1 in attenuation of NK cell activation and growth, with implications on neoplastic transformation or NK cell function when it is deregulated.

Expression and purification of soluble and functional fusion protein DAB389 IL-2 into the E. coli strain Rosetta-gami (DE3)

DAB₃₈₉ IL-2 (Denileukin diftitox) is considered an immunotoxin, and it is the first immunotoxin approved by Food and Drug Administration. It is used for the treatment of a cutaneous form of T-cell lymphoma. This fusion protein has two disulfide bonds in its structure that play an essential role in toxicity and functionality of the immunotoxin. Escherichia coli (E. coli) strain BL21 (DE3) is not capable of making disulfide bonds in its reductive cytoplasm, but the E. coli strain Rosetta-gami (DE3) is a proper strain for the correct expression of the protein due to mutations in glutaredoxin reductase and thioredoxin reductase. In this study, a pET21a vector with the His6-tag fused at the N-terminus of DAB₃₈₉ IL-2 was used to express the soluble immunotoxin in E. coli Rosetta-gami (DE3). After the purification of the soluble protein by two-step column chromatographies, the structure of DAB₃₈₉ IL-2 was analyzed using the Native-PAGE and circular dichroism methods. In the following, the nuclease activity of soluble DAB₃₈₉ IL-2 and its cytotoxicity activity were determined. It is concluded that the soluble recombinant protein expressed in the E. coli Rosetta-gami (DE3) has an intact structure and also functional; hence, this form of immunotoxin could be competitive with its commercial counterparts.

Signaling and Function of Interleukin-2 in T Lymphocytes

The discovery of interleukin-2 (IL-2) changed the molecular understanding of how the immune system is controlled. IL-2 is a pleiotropic cytokine, and dissecting the signaling pathways that allow IL-2 to control the differentiation and homeostasis of both pro- and anti-inflammatory T cells is fundamental to determining the molecular details of immune regulation. The IL-2 receptor couples to JAK tyrosine kinases and activates the STAT5 transcription factors. However, IL-2 does much more than control transcriptional programs; it is a key regulator of T cell metabolic programs. The development of global phosphoproteomic approaches has expanded the understanding of IL-2 signaling further, revealing the diversity of phosphoproteins that may be influenced by IL-2 in T cells. However, it is increasingly clear that within each T cell subset, IL-2 will signal within a framework of other signal transduction networks that together will shape the transcriptional and metabolic programs that determine T cell fate.

In Silico and in Vitro Evaluation of Deamidation Effects on the Stability of the Fusion Toxin DAB389IL-2

Background:

DAB389IL-2 (Denileukin diftitox) as an immunotoxin is a targeted pharmaceutical protein and is the first immunotoxin approved by FDA. It is used for the treatment of various kinds of cancer such as CTCL lymphoma, melanoma, and Leukemia but among all of these, treatment of CTCL has special importance. DAB389IL-2 consists of two distinct parts; the catalytic domain of Diphtheria Toxin (DT) that genetically fused to the whole IL-2. Deamidation is the most important reaction for chemical instability of proteins occurs during manufacture and storage. Deamidation of asparagine residues occurs at a higher rate than glutamine residues. The structure of proteins, temperature and pH are the most important factors that influence the rate of deamidation.

Methods:

Since there is not any information about deamidation of DAB389IL-2, we studied in silico deamidation by Molecular Dynamic (MD) simulations using GROMACS software. The 3D model of fusion protein DAB389IL-2 was used as a template for deamidation. Then, the stability of deamidated and native form of the drug was calculated.

Results:

The results of MD simulations were showed that the deamidated form of DAB389IL-2 is more unstable than the normal form. Also, deamidation was carried by incubating DAB389IL-2, 0.3 mg/ml in ammonium hydrogen carbonate for 24 h at 37o C in order to in vitro experiment.

Conclusion:

The results of in vitro experiment were confirmed outcomes of in silico study. In silico and in vitro experiments were demonstrated that DAB389IL-2 is unstable in deamidated form.

Human placental extract ameliorates cytokine and cytokine receptor signaling in the rat hippocampus upon Benzo[a]Pyrene exposure

Benzo[alpha]Pyrene (B[a]P) causes toxicity via Cytochrome P450 1A1 (CYP1A1) metabolic activity in the brain. Studies have shown that neuronal IL-2 and TNF-α are associated with the hippocampus development and regulation, but their association with the CYP1A1 activity remains unidentified. Limited action of human placental extract (HPE) in the activation of tissue repair and wound healing is known, but their role in B[a]P clearance in the hippocampus is not known so far. Our study has focused on two novel concepts: (1) association of CYP1A1 activity with the inflammatory response in the brain hippocampus and (2) role of HPE in the immunomodulatory mechanisms in the hippocampus upon B[a]P exposure at cytokine receptor and nuclear level. Intrathecal administration of different concentrations of B[a]P and HPE into male wistar rat pups has been conducted. An increased CYP1A1 activity was observed in the presence of 0.25 μM B[a]P alone but in case of HPE followed by 0.25 μM B[a]P, it was equal to control. Herein we report that 5 μl of 0.1 gm HPE followed by 0.25 μM B[a]P administration enabled down-regulation of IL-2 and TNF-α levels in the hippocampus thereby modulating TNFR2 and IL2Rγ_c signals via NF-κB activation. Besides, localization of IL-2, TNF-α, IL2Rγ_c, TNFR1 and TNFR2 in the CA1, CA3 and DG regions of the hippocampus are also depicted. Altogether, these findings will project the clinical importance of HPE in the neuroinflammation suppression in the hippocampus developed due to B[a]P toxicity.

Diffusion of cytokines in live lymph node tissue using microfluidic integrated optical imaging

Communication and drug efficacy in the immune system rely heavily on diffusion of proteins such as cytokines through the tissue matrix. Available methods to analyze diffusion in tissue require microinjection or saturating the tissue in protein, which may alter local transport properties due to damage or rapid cellular responses. Here, we developed a novel, user-friendly method - Microfluidic Integrated Optical Imaging (micro-IOI) - to quantify the effective diffusion coefficient of bioactive proteins in live tissue samples ex vivo. A microfluidic platform was used to deliver picograms of fluorescently labelled cytokines to microscale regions within slices of murine lymph node, and diffusion was monitored by widefield fluorescence microscopy. Micro-IOI was validated against theory and existing methods. Free diffusion coefficients were within 8% and 24% of Stokes-Einstein predictions for dextrans and cytokines, respectively. Furthermore, diffusion coefficients for dextrans and proteins in a model matrix were within 1.5-fold of reported results from fluorescence recovery after photobleaching (FRAP). We used micro-IOI to quantify the effective diffusion of three cytokines from different structural classes and two different expression systems - tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), and interleukin-2 (IL-2), from human and mouse - through live lymph node tissue. This is the first method to directly measure cytokine transport in live tissue slices, and in the future, it should promote a deeper understanding of the dynamics of cell-cell communication and enable targeted immunotherapy design.

Daclizumab high-yield process in the treatment of relapsing-remitting multiple sclerosis

Daclizumab is a humanized monoclonal antibody that binds to the α subunit (CD25) of the interleukin-2 receptor and favorably modulates the immune environment in multiple sclerosis (MS). Blockage of CD25, among other effects, causes expansion and enhanced function of regulatory CD56^bright natural killer cells, which seems to be the leading mechanism of action in MS. Phase II and III clinical trials have demonstrated that monthly subcutaneous injections of daclizumab high yield process (DAC HYP) 150 mg in patients with relapsing MS led to a significant reduction of annualized relapse rate and decreased number of contrast-enhanced lesions on brain magnetic resonance imaging. Treatment with DAC HYP had efficacy superior to treatment with weekly injections of interferon β1a. This review summarizes the development of and clinical experience with daclizumab in MS.

Mathematical Models of the Impact of IL2 Modulation Therapies on T Cell Dynamics

Several reports in the literature have drawn a complex picture of the effect of treatments aiming to modulate IL2 activity in vivo. They seem to promote either immunity or tolerance, probably depending on the specific context, dose, and timing of their application. Such complexity might derive from the pleiotropic role of IL2 in T cell dynamics. To theoretically address the latter possibility, our group has developed several mathematical models for Helper, Regulatory, and Memory T cell population dynamics, which account for most well-known facts concerning their relationship with IL2. We have simulated the effect of several types of therapies, including the injection of: IL2; antibodies anti-IL2; IL2/anti-IL2 immune-complexes; and mutant variants of IL2. We studied the qualitative and quantitative conditions of dose and timing for these treatments which allow them to potentiate either immunity or tolerance. Our results provide reasonable explanations for the existent pre-clinical and clinical data, predict some novel treatments, and further provide interesting practical guidelines to optimize the future application of these types of treatments.

Maximum-likelihood approaches reveal signatures of positive selection in IL genes in mammals

ILs are part of the immune system and are involved in multiple biological activities. ILs have been shown to evolve under positive selection; however, little information exists regarding which codons are specifically selected. By using different codon-based maximum-likelihood (ML) approaches, signatures of positive selection in mammalian ILs were searched for. Sequences of 46 ILs were retrieved from publicly available databases of mammalian genomes to detect signatures of positive selection in individual codons. Evolutionary analyses were conducted under two ML frameworks, the HyPhy package implemented in the Data Monkey Web Server and CODEML implemented in PAML. Signatures of positive selection were found in 28 ILs: IL-1A and B; IL-2, IL-4 to IL-10, IL-12A and B; IL-14 to IL-17A and C; IL-18, IL-20 to IL-22, IL-25, IL-26, IL-27B, IL-31, IL-34, IL-36A; and G. Codons under positive selection varied between 1 and 15. No evidence of positive selection was detected in IL-13; IL-17B and F; IL-19, IL-23, IL-24, IL-27A; or IL-29. Most mammalian ILs have sites evolving under positive selection, which may be explained by the multitude of biological processes in which ILs are enrolled. The results obtained raise hypotheses concerning the ILs functions, which should be pursued by using mutagenesis and crystallographic approaches.

Dendritic cells control CD4+CD25+ Treg cell suppressor function in vitro through juxtacrine delivery of IL-2

CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) restrict inflammatory responses to self and nonself. Aberrant Treg activity is pathologic: Insufficient Treg activity is implicated in autoimmunity, allergy, and graft-versus-host-disease; overabundant activity is implicated in chronic infection and cancer. Tregs require IL-2 for their expansion and acquisition/execution of suppressor function; however, because Tregs cannot produce IL-2, they depend on IL-2 from an exogenous source. Until now, that IL-2 source had not been established. We asked whether dendritic cells (DCs) could supply IL-2 to Tregs and, if so, what was required for that delivery. We used flow cytometry, IL-2 ELISPOT, RT-qPCR, and IL-2 promoter-driven reporter assays to measure intracytoplasmic IL-2, secreted protein, IL-2 message and IL-2 promoter activity in bone marrow-derived (BMDC) and splenic DCs. We examined conjugate formation between Tregs, conventional CD4(+) cells, and IL-2-expressing DCs. We measured Treg levels of CD25, Foxp3, and suppressor function after co-culture with IL-2 sufficient and IL-2(-/-) DCs. We generated IL-2-mCherry-expressing DCs and used epifluorescence microscopy and flow cytometry to track IL-2 transfer to Tregs and test requirements for transfer. Between 0.7 to 2.4% of DCs constitutively produced IL-2 and diverted IL-2 secretion to Tregs by preferentially forming conjugates with them. Uptake of DC IL-2 by Tregs required cell-cell contact and CD25. Tregs increased levels of CD25 and Foxp3 from baseline and showed greater suppressor function when co-cultured with IL-2-sufficient DCs, but not when co-cultured with IL-2(-/-) DCs. Exogenous IL-2, added in excess of 500 U/ml to co-cultures with IL-2(-/-) DCs, restored Treg suppressor function. These data support a model of juxtacrine delivery of IL-2 from DCs to Tregs and suggest that a subset of DCs modulates Treg function through controlled, spatial delivery of IL-2. Knowledge of how DCs regulate Tregs should be integrated into the design of interventions intended to alter Treg function.

The 20th anniversary of interleukin-2 therapy: bimodal role explaining longstanding random induction of complete clinical responses

Background

This year marks the twentieth anniversary of the approval by the US Food and Drug Administration of interleukin-2 (IL2) for use in cancer therapy, initially for renal cell carcinoma and later for melanoma. IL2 therapy for cancer has stood the test of time, with continued widespread use in Europe, parts of Asia, and the US. Clinical complete responses are variably reported at 5%–20% for advanced malignant melanoma and renal cell carcinoma, with strong durable responses and sustained long-term 5–10-year survival being typical if complete responses are generated.

Methods

The literature was reviewed for the actions and clinical effects of IL2 on subsets of T cells. The influence of IL2 on clinical efficacy was also sought.

Results

The review revealed that IL2 is capable of stimulating different populations of T cells in humans to induce either T effector or T regulatory responses. This apparent “functional paradox” has confounded a clear understanding of the mechanisms behind the clinical effects that are observed during and following administration of IL2 therapy. An average complete response rate of around 7% in small and large clinical trials using IL2 for advanced renal cell carcinoma and malignant melanoma has been shown from a recent review of the literature.

Conclusion

This review considers the published literature concerning the actions and emerging clinical effects of IL2 therapy, spanning its 20-year period in clinical use. It further details some of the recently described “bimodal” effects of IL2 to explain the apparent functional paradox, and how IL2 might be harnessed to emerge rapidly as a much more effective and predictable clinical agent in the near future.

Modeling the role of IL2 in the interplay between CD4+ helper and regulatory T cells: studying the impact of IL2 modulation therapies

Several reports in the literature have drawn a complex picture of the effect of treatments aiming to modulate IL2 activity in vivo. They seem to promote indistinctly immunity or tolerance, probably depending on the specific context, dose and timing of their application. Such complexity might derives from the dual role of IL2 on T-cell dynamics. To theoretically address the latter possibility, we develop a mathematical model for helper, regulatory and memory T-cells dynamics, which account for most well-known facts relative to their relationship with IL2. We simulate the effect of three types of therapies: IL2 injections, IL2 depletion using anti-IL2 antibodies and IL2/anti-IL2 immune complexes injection. We focus in the qualitative and quantitative conditions of dose and timing for these treatments which allow them to potentate either immunity or tolerance. Our results provide reasonable explanations for the existent pre-clinical and clinical data and further provide interesting practical guidelines to optimize the future application of these types of treatments. Particularly, our results predict that: (i) Immune complexes IL2/anti-IL2 mAbs, using mAbs which block the interaction of IL2 and CD25 (the alpha chain of IL2 receptor), is the best option to potentate immunity alone or in combination with vaccines. These complexes are optimal when a 1:2 molar ratio of mAb:IL2 is used and the mAbs have the largest possible affinity; (ii) Immune complexes IL2/anti-IL2 mAbs, using mAbs which block the interaction of IL2 and CD122 (the beta chain of IL2 receptor), are the best option to reinforce preexistent natural tolerance, for instance to prevent allograft rejection. These complexes are optimal when a 1:2 molar ratio of mAb:IL2 is used and the mAbs have intermediate affinities; (iii) mAbs anti-IL2 can be successfully used alone to treat an ongoing autoimmune disorder, promoting the re-induction of tolerance. The best strategy in this therapy is to start treatment with an initially high dose of the mAbs (one capable to induce some immune suppression) and then scales down slowly the dose of mAb in subsequent applications.

Lactobacillus rhamnosus GG secreting an antigen and Interleukin-2 translocates across the gastrointestinal tract and induces an antigen specific immune response

Lactobacillus rhamnosus strain GG (LGG) is a probiotic organism. In this present study, LGG that express the green fluorescence protein (LGG-GFP) and IL-2 and GFP as a fusion protein (LGG-IL-2-GFP) were used to examine bacterial uptake and the immune response induced by oral immunization. Using TEM to examine the intestinal tissue, the Lactobacilli were localized in M cells and in venules. After oral immunization, most of the bacteria were excreted in feces only a small fraction (0.15%) was retained in the intestine at 48 hr. However, more LGG-IL-2-GFP was found in the MLN and spleen than LGG-GFP. The loop ligation method was used to evaluate LGG uptake and both LGG-GFP and LGG-IL-2-GFP were found to translocate at the same rate. Analysis of LGG internalization in J774 macrophage cells indicated that IL-2 increased survival of LGG and this may explain the increased presence of these bacteria in the MLN for a longer period. After oral immunization, specific mucosal antibody production as well as GFP specific CTL activity was demonstrated. IL-2 co-expression with GFP further enhanced antibody production and CTL activity. In conclusion, Lactobacillus rhamnosus GG expressing an antigen could generate an effective immune response to the antigen and IL-2 improved the response generated probably by increasing LGG expressing antigen survival in immune cells.

Development of an attenuated interleukin-2 fusion protein that can be activated by tumour-expressed proteases

The ability to alter the cytokine microenvironment has the potential to shape immune responses in many physiological settings, including the immunotherapy of tumours. We set out to develop a general approach in which cytokines could be functionally attenuated until activated. We report the development and initial characterization of fusion proteins in which human or mouse interleukin-2 (IL-2), a potent growth factor for immune cells, is joined to a specific IL-2 inhibitory binding component separated by a protease site. The rationale is that upon cleavage by a protease the cytokine is free to dissociate from the inhibitory component and becomes biologically more available. We describe the successful development of two attenuation strategies using specific binding: the first uses the mouse IL-2 receptor alpha chain as the inhibitory binding component whereas the second employs a human antibody fragment (scFv) reactive with human IL-2. We demonstrated that the fusion proteins containing a prostate-specific antigen or a matrix metalloproteinase (MMP) protease cleavage site are markedly attenuated in the intact fusion protein but had enhanced bioactivity of IL-2 in vitro when cleaved. Further, we showed that a fusion protein composed of the IL-2/IL-2 receptor alpha chain with an MMP cleavage site reduced tumour growth in vivo in a peritoneal mouse tumour model. This general strategy should be applicable to other proteases and immune modulators allowing site-specific activation of immunomodulators while reducing unwanted side-effects.

Modified DT-IL2 fusion toxin targeting uniquely IL2Ralpha expressing leukemia cell lines - Construction and characterization

Immunotoxins are fusion proteins of modified toxin conjugated to tumor cell selective ligand. Denileukin diftitox approved by FDA for treatment of CTCL is diphtheria toxin (DT)/IL2 fusion protein targeted to high affinity IL2R. Here, we have attempted to target the more uniquely expressed low affinity IL2R (IL2Ralpha). We designed four immunotoxins, SPRSV1 was designed to code for a single protein of DT (390) and IL2 (133) without any extra amino acids at the junction. SPRSV2 was designed to selectively target low affinity IL2R, it codes for DT (390) and IL2 (69). We also constructed SPRSV3 encoding for only DT (390) without any ligand, as negative control and SPRSV4 was designed similar to commercial equivalent denileukin diftitox, it codes for DT (387) and IL2 (133) with His at the junction. The cytotoxic activities of these immunotoxins were tested in various cell lines, cell lines lacking IL2R expression and healthy MNC were used as controls. The activities of SPRSV1 and SPRSV2 were comparable to that of SPRSV4. SPRSV2 exhibited potent cytotoxicity effectively targeted to alpha subunit of IL2R on various leukemia cell lines. Our studies also showed a negative correlation between CD25 expression and percentage cell viability after treatment with immunotoxins.

Rainbow trout interleukin-2: cloning, expression and bioactivity analysis

In this study the rainbow trout (Oncorhynchus mykiss) interleukin-2 (IL-2) cDNA has been cloned, and its expression and bioactivity analysed in head kidney leucocytes. The IL-2 precursor encoded an open reading frame of 429 bp, that translates into a predicted protein of 142 aa, with a 20 aa signal peptide. The trout IL-2 had moderate protein homology (30.9% identity/48.3% similarity) with Fugu IL-2, the only IL-2 homologue identified in fish to date, with lower homology to avian (17.8% identity/23.2% similarity) and mammalian (34.2 identity/46.5% similarity) IL-2s. IL-2 expression was induced by the T cell mitogen PHA and by the mixed leucocyte reaction, where leucocytes from pairs of fish were cultured together for four days. Expression was also induced in vivo during bacterial (Yersinia ruckeri) infection. The Escherichia coli produced recombinant IL-2 was shown to increase the expression of two transcription factors, STAT5 and Blimp-1, known to be involved in IL-2 signalling in mammals, as well as IFN-gamma, gIP and IL-2 itself. The potential signalling pathways involved and possible use as an adjuvant for fish vaccines are discussed.