Reconciling id, ego, and superego within interleukin-23

Granzyme K mediates IL-23-dependent inflammation and keratinocyte proliferation in psoriasis

Psoriasis is an inflammatory disease with systemic manifestations that most commonly presents as itchy, erythematous, scaly plaques on extensor surfaces. Activation of the IL-23/IL-17 pro-inflammatory signaling pathway is a hallmark of psoriasis and its inhibition is key to clinical management. Granzyme K (GzmK) is an immune cell-secreted serine protease elevated in inflammatory and proliferative skin conditions. In the present study, human psoriasis lesions exhibited elevated GzmK levels compared to non-lesional psoriasis and healthy control skin. In an established murine model of imiquimod (IMQ)-induced psoriasis, genetic loss of GzmK significantly reduced disease severity, as determined by delayed plaque formation, decreased erythema and desquamation, reduced epidermal thickness, and inflammatory infiltrate. Molecular characterization in vitro revealed that GzmK contributed to macrophage secretion of IL-23 as well as PAR-1-dependent keratinocyte proliferation. These findings demonstrate that GzmK enhances IL-23-driven inflammation as well as keratinocyte proliferation to exacerbate psoriasis severity.

Hepatitis B Virus Reactivation and Mycobacterial Infections Associated With Ustekinumab: A Retrospective Study of an International Pharmacovigilance Database

Background: Reports were recently published on hepatitis B virus reactivation (HBVr), tuberculosis (TB), and atypical mycobacterial infection (AMI) in patients with ustekinumab treatment. However, the literature is limited to case reports and series. The study was aimed to investigate their relationships by using an extensive population-based database.

Methods: Using the United States Food and Drug Administration Adverse Event Reporting System (FAERS) database, we collected all cases of HBVr, TB, and AMI between 1 January 2009 and 30 September 2021, for ustekinumab and other drugs. Disproportionality was analyzed using the reporting odds ratio (ROR), which was considered significant when the lower limit of the 95% confidence interval (95% CI) was >1.

Results: Of the 18,760,438 adverse cases reported to FAERS for all drugs, 56,581 cases had been exposed to ustekinumab. Adverse events of HBVr, TB, and AMI were reported in 21, 210, and 20 cases, respectively. The ROR for HBVr with ustekinumab was 2.33 (95% CI, 1.52–3.58), for TB was 5.09 (95% CI, 4.44–5.84), and for AMI was 2.09 (95% CI, 1.35–3.24). In the ustekinumab exposure group, no death occurred in patients with HBVr, but one patient experienced life-threatening liver failure. For those with TB, 24 cases experienced hospitalization and 2 deaths occurred. No death occurred in patients with AMI but eight experienced hospitalization.

Conclusion: We identified positive signals between ustekinumab exposure and HBVr, TB, and AMI in FAERS. Although these complications are rare, clinicians using ustekinumab should be aware of the risks.

Role of the IL-23/IL-17 Pathway in Rheumatic Diseases: An Overview

Interleukin-23 (IL-23) is a pro-inflammatory cytokine composed of two subunits, IL-23A (p19) and IL-12/23B (p40), the latter shared with Interleukin-12 (IL-12). IL-23 is mainly produced by macrophages and dendritic cells, in response to exogenous or endogenous signals, and drives the differentiation and activation of T helper 17 (Th17) cells with subsequent production of IL-17A, IL-17F, IL-6, IL-22, and tumor necrosis factor α (TNF-α). Although IL-23 plays a pivotal role in the protective immune response to bacterial and fungal infections, its dysregulation has been shown to exacerbate chronic immune-mediated inflammation. Well-established experimental data support the concept that IL-23/IL-17 axis activation contributes to the development of several inflammatory diseases, such as PsA, Psoriasis, Psoriatic Arthritis; AS, Ankylosing Spondylitis; IBD, Inflammatory Bowel Disease; RA, Rheumatoid Arthritis; SS, Sjogren Syndrome; MS, Multiple Sclerosis. As a result, emerging clinical studies have focused on the blockade of this pathogenic axis as a promising therapeutic target in several autoimmune disorders; nevertheless, a greater understanding of its contribution still requires further investigation. This review aims to elucidate the most recent studies and literature data on the pathogenetic role of IL-23 and Th17 cells in inflammatory rheumatic diseases.

Guselkumab in patients with active psoriatic arthritis who were biologic-naive or had previously received TNFα inhibitor treatment (DISCOVER-1): a double-blind, randomised, placebo-controlled phase 3 trial

BACKGROUND

Many patients with psoriatic arthritis have an inadequate response to tumor necrosis factor (TNF) inhibitors. Guselkumab, a specific inhibitor of interleukin-23 (IL-23) via IL-23 p19 subunit binding, significantly improved psoriatic arthritis signs and symptoms with an acceptable safety profile in a phase 2 trial.

METHODS

This multicentre, double-blind, randomised, placebo-controlled, phase 3 trial was done at 86 sites in 13 countries across Asia, Australasia, Europe, and North America and enrolled adults with active psoriatic arthritis (at least three swollen and three tender joints; and C-reactive protein ≥0·3 mg/dL) despite standard therapies. Eligibility criteria included inadequate response to or intolerance of standard treatment, including at least 4 months of apremilast, at least 3 months of non-biologic disease-modifying antirheumatic drugs (DMARDs), or at least 4 weeks of non-steroidal anti-inflammatory drugs for psoriatic arthritis. About 30% of study participants could have previously received one or two TNF inhibitors. Patients were randomly assigned (1:1:1, computer-generated permuted blocks; stratified by baseline DMARD and previous TNF inhibitor use) to subcutaneous guselkumab 100 mg every 4 weeks; guselkumab 100 mg at weeks 0, 4, then every 8 weeks; or matching placebo. The primary endpoint was American College of Rheumatology 20% improvement (ACR20) at week 24 in all patients per assigned treatment group using non-responder imputation. Safety was assessed in all patients per treatment received. This trial is registered at ClinicalTrials.gov, NCT03162796 (active, not recruiting).

FINDINGS

From Aug 28, 2017, to Aug 17, 2018, we screened 624 patients, of whom 381 were randomly assigned and treated with guselkumab every 4 weeks (n=128), guselkumab every 8 weeks (n=127), or placebo (n=126). 362 patients continued study treatment up to week 24. The primary endpoint was met: ACR20 at week 24 was achieved by significantly greater proportions of patients in the guselkumab every 4 weeks group (76 [59%] of 128 [95% CI 50-68]) and every 8 weeks group (66 [52%] of 127 [43-61]) than in the placebo group (28 [22%] of 126 [15-30]), with percentage differences versus placebo of 37% (95% CI 26-48) for the every 4 weeks group and 30% (19-41) for the every 8 weeks group (both p<0·0001). Serious adverse events up to week 24 occurred in no patients receiving guselkumab every 4 weeks, four (3%) patients receiving guselkumab every 8 weeks, and five (4%) patients receiving placebo. Up to week 24, one patient in the placebo group died from cardiac failure and two had serious infections; no guselkumab-treated patient died or had serious infections.

INTERPRETATION

Guselkumab demonstrated a favourable benefit-risk profile and might be an effective treatment option for patients with active psoriatic arthritis.

FUNDING

Janssen Research and Development.

Analysis of interleukin 23 and 7G10 interactions for computational design of lead antibodies against immune-mediated inflammatory diseases

Wealth of structural data on theurapeutic targets in complex with monoclonal antibodies (mAbs) and advances in molecular modeling algorithms present exciting opportunities in the field of novel biologic design. Interleukin 23 (IL23), a well-known drug target for autoimmune diseases, in complex with mAb 7G10 offers prospect to design potent lead antibodies by traversing the complete epitope-paratope interface. Herein, key interactions aiding antibody-based neutralization in IL23-7G10 complex are resolute through PyMOL, LigPlot⁺, Antibody i-Patch, DiscoTope and FoldX. Six amino acids Ser31, Val33, Asn55, Lys59 in heavy chain and His34, Ser93 in light chain are subjected to in silico mutagenesis with residues Met, Trp, Ile, Leu and Arg. A set of 431 mutant macromolecules are outlined. Binding affinities of these molecules with IL23 are estimated through protein-protein docking by employing ZDOCK, ClusPro and RosettaDock. Subsequently, the macromolecules revealed comparable result with 7G10 are cross validated through binding free-energy calculations by applying Molecular Mechanics/Poisson Boltzman Surface Area method in CHARMM. Thirty nine designed theoretical antibodies showed improved outcome in all evaluations; from these, top 10 molecules showed at least nine unit better binding affinity compared to the known mAb. These molecules have the potential to act as lead antibodies. Subsequent molecular dynamics simulations too favored prospective of best ranked molecule to have therapeutic implications in autoimmune and inflammatory diseases. Abbreviations: IL23: interleukin 23; IL17: interleukin17; Ab: antibody; Ag: antigen; mAbs: monoclonal antibodies; STAT3: signal transducer and activator of transcription 3; STAT4: signal transducer and activator of transcription 4; PDB: protein databank; MM/PBSA: molecular mechanics Poisson-Boltzmann surface area; Ag-Ab: antigen- antibody complex; SPC/E: extended simple point charge; SD: steepest descents; PME: particle mesh ewald; dG: binding free energies; Fv: variable fragment.

IL-23 promotes TCR-mediated negative selection of thymocytes through the upregulation of IL-23 receptor and RORγt

Transient thymic involution is frequently found during inflammation, yet the mode of action of inflammatory cytokines is not well defined. Here we report that interleukin-23 (IL-23) production by the thymic dendritic cells (DCs) promotes apoptosis of the CD4^hiCD8^hi double positive (DP) thymocytes. A deficiency in IL-23 signaling interferes with negative selection in the male D^b/H-Y T-cell receptor (TCR) transgenic mice. IL-23 plus TCR signaling results in significant up-regulation of IL-23 receptor (IL-23R) expressed predominantly on CD4^hiCD8^hiCD3⁺αβTCR⁺ DP thymocytes, and leads to RORγt dependent apoptosis. These results extend the action of IL-23 beyond its peripheral effects to a unique role in TCR mediated negative selection including elimination of natural T regulatory cells in the thymus.

Recognition strategies of group 3 innate lymphoid cells

During the early phase of an inflammatory response, innate cells can use different strategies to sense environmental danger. These include the direct interaction of specific activating receptors with pathogen-encoded/danger molecules or the engagement of cytokine receptors by pro-inflammatory mediators produced by antigen presenting cells in the course of the infection. These general recognition strategies, which have been extensively described for innate myeloid cells, are shared by innate lymphoid cells (ILC), such as Natural Killer (NK) cells. The family of ILC has recently expanded with the discovery of group 2 (ILC2) and group 3 ILC (ILC3), which play an important role in the defense against extracellular pathogens. Although ILC3 and NK cells share some phenotypic characteristics, the recognition strategies employed by the various ILC3 subsets have been only partially characterized. In this review, we will describe and comparatively discuss how ILC3 sense environmental cues and how the triggering of different receptors may regulate their functional behavior during an immune response.

Role of IL-23 in the pathogenesis of psoriasis: a novel potential therapeutic target?

INTRODUCTION

Psoriasis is a chronic inflammatory skin disorder determined by the activation of several immune cells and resident tissue cells. Various cytokines mediate inflammatory signals, including IL-23, which is an important factor involved in the differentiation of T helper (Th17) cells.

AREAS COVERED

Increasing evidence suggests that IL-23 is a central cytokine to the pathogenesis of psoriasis. An overview on both experimental and human data will be reported in order to support the hypothesis of a key pathogenic role of IL-23/Th17 axis.

EXPERT OPINION

Targeting IL-23 might be a more selective, valid and effective therapeutic approach, which, potentially, may show important advantages in terms of long-term efficacy and safety in the treatment of psoriasis.

Inflammatory monocyte recruitment is regulated by interleukin-23 during systemic bacterial infection

Listeria monocytogenes is a gram-positive intracellular pathogen that causes meningitis and septicemia in immunocompromised individuals and spontaneous abortion in pregnant women. The innate immune response against L. monocytogenes is primarily mediated by neutrophils and monocytes. Interleukin-23 (IL-23) is an important proinflammatory cytokine well known for its role in neutrophil recruitment in various infectious and autoimmune diseases. We have previously shown that IL-23 is required for host resistance against L. monocytogenes and for neutrophil recruitment to the liver, but not the spleen, during infection. Despite efficient neutrophil recruitment to the spleen, IL-23p19 knockout (KO) mice have an increased bacterial burden in this organ, suggesting that IL-23 may regulate the recruitment/function of another cell type to the spleen. In this study, we show that specific depletion of neutrophils abrogated the differences in bacterial burdens in the livers but not the spleens of C57BL/6 (B6) and IL-23p19 KO mice. Interestingly, L. monocytogenes-infected IL-23p19 KO mice had fewer monocytes in the spleen than B6 mice, as well as a reduction in the monocyte-recruiting chemokines CCL2 and CCL7. Additionally, the overall concentrations of tumor necrosis factor alpha (TNF-α) and nitric oxide (NO(•)), as well as the percentages and total numbers of monocytes producing TNF-α and NO(•), were reduced in IL-23p19 KO mice compared to levels in B6 mice, leading to increased bacterial burdens in the spleens of L. monocytogenes-infected IL-23p19 KO mice. Collectively, our data establish that IL-23 is required for the optimal recruitment of TNF-α- and NO(•)-producing inflammatory monocytes, thus revealing a novel mechanism by which this proinflammatory cytokine provides protection against bacterial infection.

Interleukin-23: as a drug target for autoimmune inflammatory diseases

Interleukin-23 (IL-23) is a member of the IL-12 family of cytokines with pro-inflammatory properties. Its ability to potently enhance the expansion of T helper type 17 (Th17) cells indicates the responsibility for many of the inflammatory autoimmune responses. Emerging data demonstrate that IL-23 is a key participant in central regulation of the cellular mechanisms involved in inflammation. Both IL-23 and IL-17 form a new axis through Th17 cells, which has evolved in response to human diseases associated with immunoactivation and immunopathogeny, including bacterial or viral infections and chronic inflammation. Targeting of IL-23 or the IL-23 receptor or IL-23 axis is a potential therapeutic approach for autoimmune diseases including psoriasis, inflammatory bowel disease, rheumatoid arthritis and multiple sclerosis. The current review focuses on the immunobiology of IL-23 and summarizes the most recent findings on the role of IL-23 in the pre-clinical and ongoing clinical studies.

Interleukin-23 serum levels in patients affected by peripheral arterial disease

OBJECTIVES

To clarify whether interleukin (IL)-23 is involved in peripheral arterial disease (PAD).

DESIGN AND METHODS

We evaluated IL-23 serum levels, in 29 patients suffering from lower extremity PAD and in 30 healthy subjects.

RESULTS

IL-23 serum levels were higher during the three times (T0, T1 and T2) compared to the control group, although only statistically significant for T0 and T2: T0 (15.83 ± 22.08 vs. 8.08 ± 8.62 pg ml, p=0.026), T1 (16.10 ± 23.71 vs. 8.08 ± 8.62 pg/ml, p=0.101), T2 (15.06 ± 16.72 vs. 8.08 ± 8.62 pg/ml, p=0.005).

CONCLUSION

For the first time, our data gives us reason to believe there is an involvement of IL-23 in PAD.

Interleukin-23: a key cytokine in inflammatory diseases

Interleukin-23 (IL-23) is a pro-inflammatory cytokine composed of two subunits, p19 and p40. The p40 subunit is shared with IL-12. IL-23 and IL-12 have different receptors and different effects. Whereas IL-12 induces development of Th1 cells, which produce interferon-γ, IL-23 is involved in differentiation of Th17 cells in a pro-inflammatory context and especially in the presence of TGF-β and IL-6. Activated Th17 cells produce IL-17A, IL-17F, IL-6, IL-22, TNF-α, and GM-CSF. Inflammatory macrophages express IL-23R and are activated by IL-23 to produce IL-1, TNF-α, and IL-23 itself. These effects identify IL-23 as a central cytokine in autoimmunity and a highly promising treatment target for inflammatory diseases. IL-23 is found in the skin of patients with psoriasis, in the bowel wall of patients with chronic inflammatory bowel disease, and in synovial membrane of patients with rheumatoid arthritis. IL-23 is involved in osteoclastogenesis, independently from IL-17, via induction of RANKL expression. Debate continues to surround the role for IL-23 in the pathophysiology of inflammatory joint diseases (rheumatoid arthritis and spondyloarthritis). Ustekinumab, which inhibits IL-12 and IL-23 by blocking p40, has been found effective in cutaneous psoriasis and psoriatic arthritis, as well as in Crohn's disease. Treatments that specifically target IL-23 (antibodies to p19) are being developed.

Insights into human antifungal immunity from primary immunodeficiencies

Some mendelian (monogenic) disorders directly conferring increased susceptibility are associated with diverse infectious organisms, whereas others are restricted in scope to specific genera or even to one species. So far, most investigations of primary immunodeficiency disorders have focused on those conferring susceptibility to viral, bacterial, or mycobacterial infections, providing powerful insight into human determinants of host resistance to these microbes. Monogenic disorders that increase susceptibility to fungal infections are increasingly being recognised. Although infections associated with these disorders are probably less common than are iatrogenic associated mycoses, they provide valuable insight into human immunity to fungal infections. Investigation of these immunological pathways will ultimately lead to improvements in management of such infections in secondarily immunocompromised patients.

Regulation of the development of acute hepatitis by IL-23 through IL-22 and IL-17 production

IL-23 plays a critical role in the expansion of highly proinflammatory Th17 cells secreting IL-17 and IL-22. Recently, we demonstrated that Notch signaling drives IL-22 secretion through the aryl hydrocarbon receptor (AHR) and plays a protective role in Con A-induced hepatitis. In this study, we investigated the role of IL-23 in hepatitis using IL-23p19- and IL-17-deficient mice. In WT mice, the injection of Con A induced the upregulation of various cytokines, which included IL-23, IL-22, IL-17, IFN-γ and TNF-α. In IL-23p19-deficient mice, exacerbated hepatitis was observed and serum IL-22 and IL-17 levels were greatly reduced, whereas in IL-17-deficient mice, ameliorated hepatitis was observed. The injection of exogenous IL-22 protected p19-deficient mice from hepatitis, whereas the injection of exogenous IL-23 significantly increased the serum levels of not only IL-22 but also IL-17, and less effectively protected against hepatitis in IL-17-dependent and -independent manners. Finally, it was revealed that STAT3, STAT4 and Notch contributed to the production of both the cytokines, and that the AHR was important only for IL-22 production in response to Con A and IL-23 in liver mononuclear cells. These results suggest that IL-23 plays a protective role in hepatitis through IL-22 production and also a pathological role via IL-17-dependent and -independent mechanisms.

IL-23 in infections, inflammation, autoimmunity and cancer: possible role in HIV-1 and AIDS

The growing family of interleukin (IL)-12-like cytokines produced by activated macrophages and dendritic cells became the important players in the control of infections, development of inflammation, autoimmunity and cancer. However, the role of one of them-heterodimer IL-23, which consists of IL12p40 and the unique p19 subunit in HIV-1 infection pathogenesis and progression to AIDS, represent special interest. We overviewed findings of IL-23 involvement in control of peripheral bacterial pathogens and opportunistic infection, central nervous system (CNS) viral infections and autoimmune disorders, and tumorogenesis, which potentially could be applicable to HIV-1 and AIDS.

CD3+CD4-CD8- (double negative) T cells: saviours or villains of the immune response?

Recent studies have shown that T cells are not just the latecomers in inflammation but might also play a key role in the early phase of this response. In this context, a number of T cell subsets including NKT cells, mucosal-associated invariant T cells and γ/δ T cells have been shown, together with classical innate immune cells, to contribute significantly to the development and establishment of acute and chronic inflammatory diseases. In this commentary we will focus our attention on a somewhat neglected class of T cells called CD3(+)CD4(-)CD8(-) double negative T cells and on their role in inflammation and autoimmunity. We will summarize the most recent views on their origin at the thymic and peripheral levels as well as their tissue localization in immune and non-lymphoid organs. We will then outline their potential pathogenic role in autoimmunity as well as their homeostatic role in suppressing excessive immune responses deleterious to the host. Finally, we will discuss the potential therapeutic benefits or disadvantages of targeting CD3(+)CD4(-)CD8(-) double negative T cells for the treatment of autoimmune disease. We hope that this overview will shed some light on the function of these immune cells and attract the interest of investigators aiming at the design of novel therapeutic approaches for the treatment of autoimmune and inflammatory conditions.

Antimelanoma immunotherapy: clinical and preclinical applications of IL-12 family members

Malignant melanoma has been considered a prototypical 'immunogenic' tumor through clinical observations, such as the spontaneous regression of primary lesions, their higher incidence in immune-suppressed individuals, and the development of vitiligo after immunotherapy. Among many cytokines, IL-12 is one of the best characterized and the most potent anti-tumor cytokines. Although the systemic application of IL-12 resulted in disappointing results owing to its considerable toxicity, IL-12 is not entirely unusable in the clinical setting. IL-12-related cytokines, IL-23 and IL-27, have also been shown to possess anti-tumor activities in preclinical models. Although belonging to the same cytokine family, IL-12, IL-23 and IL-27 were found to have different anti-tumor mechanisms, adjuvant activity for tumor vaccines and adverse effects in a poorly immunogeneic melanoma model. In addition, their novel activities on melanoma have been clarified. We briefly review the key features of these members of the IL-12 cytokine family and discuss their potential relevance to melanoma immunity and antimelanoma immunotherapy.

Posttranscriptional regulation of IL-23 expression by IFN-gamma through tristetraprolin

IL-23 plays an essential role in maintenance of IL-17-producing Th17 cells that are involved in the pathogenesis of several autoimmune diseases. Regulation of Th17 cells is tightly controlled by multiple factors such as IL-27 and IFN-γ. However, the detailed mechanisms responsible for IFN-γ-mediated Th17 cell inhibition are still largely unknown. In this study, we demonstrate that IFN-γ differentially regulates IL-12 and IL-23 production in both dendritic cells and macrophages. IFN-γ suppresses IL-23 expression by selectively targeting p19 mRNA stability through its 3'-untranslated region (3'UTR). Furthermore, IFN-γ enhances LPS-induced tristetraprolin (TTP) mRNA expression and protein production. Overexpression of TTP suppresses IL-23 p19 mRNA expression and p19 3'UTR-dependent luciferase activity. Additionally, deletion of TTP completely abolishes IFN-γ-mediated p19 mRNA degradation. We further demonstrate that IFN-γ suppresses LPS-induced p38 phosphorylation, and blockade of p38 MAPK signaling pathway with SB203580 inhibits IFN-γ- and LPS-induced p19 mRNA expression, whereas overexpression of p38 increases p19 mRNA expression via reducing TTP binding to the p19 3'UTR. Finally, inhibition of p38 phosphorylation by IFN-γ leads to TTP dephosphorylation that could result in stronger binding of the TTP to the adenosine/uridine-rich elements in the p19 3'UTR and p19 mRNA degradation. In summary, our results reveal a direct link among TTP, IFN-γ, and IL-23, indicating that IFN-γ-mediated Th17 cell suppression might act through TTP by increasing p19 mRNA degradation and therefore IL-23 inhibition.

Differential antitumor effect of interleukin-12 family cytokines on orthotopic hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most difficult cancers to treat. The interleukin (IL)-12 family cytokines, including IL-12, IL-23 and IL-27, display overlapping, but not redundant, roles in regulating lymphocyte subpopulations. IL-12 is known as a potent antitumor cytokine, whereas the results of the antitumor effect of IL-23 and IL-27 are inconsistent. The present study aimed to directly compare the relative antitumor efficacy of these three IL-12 family cytokines on HCC.

METHODS

A murine orthotopic BNL HCC model, in which the tumor is located in an environment heavily populated with different lymphocyte subsets, was established. The hepatotropic adeno-associated virus serotype 8 (AAV8) vector was used to deliver the cytokine genes aiming to achieve sustained cytokine expression in the liver.

RESULTS

AAV8/IL-12 treatment significantly reduced hepatic metastases and prolonged survival time, whereas treatment with AAV8/IL-23 or AAV8/IL-27 had only moderate antitumor effects at a high dose. The antitumor efficacy of these cytokines was positively correlated with their ability to regulate hepatic T cells, natural killer cells and natural killer T cells, with IL-12 greatly increasing the number and activation status of these cells, whereas IL-27 had no effect and IL-23 had a negative effect. AAV8/IL-12 treatment also resulted in a marked decrease in tumor vessel density, which was not observed with AAV8/IL-23 and AAV8/IL-27 treatment.

CONCLUSIONS

The data obtained in the present study highlight the importance of local lymphocytes and anti-angiogenesis for influencing the antitumor activity of these three IL-12 family cytokines and suggest that IL-12 is the best candidate for treating HCC.

Modulation of innate and adaptive immune responses by tofacitinib (CP-690,550)

Inhibitors of the JAK family of nonreceptor tyrosine kinases have demonstrated clinical efficacy in rheumatoid arthritis and other inflammatory disorders; however, the precise mechanisms by which JAK inhibition improves inflammatory immune responses remain unclear. In this study, we examined the mode of action of tofacitinib (CP-690,550) on JAK/STAT signaling pathways involved in adaptive and innate immune responses. To determine the extent of inhibition of specific JAK/STAT-dependent pathways, we analyzed cytokine stimulation of mouse and human T cells in vitro. We also investigated the consequences of CP-690,550 treatment on Th cell differentiation of naive murine CD4(+) T cells. CP-690,550 inhibited IL-4-dependent Th2 cell differentiation and interestingly also interfered with Th17 cell differentiation. Expression of IL-23 receptor and the Th17 cytokines IL-17A, IL-17F, and IL-22 were blocked when naive Th cells were stimulated with IL-6 and IL-23. In contrast, IL-17A production was enhanced when Th17 cells were differentiated in the presence of TGF-β. Moreover, CP-690,550 also prevented the activation of STAT1, induction of T-bet, and subsequent generation of Th1 cells. In a model of established arthritis, CP-690,550 rapidly improved disease by inhibiting the production of inflammatory mediators and suppressing STAT1-dependent genes in joint tissue. Furthermore, efficacy in this disease model correlated with the inhibition of both JAK1 and JAK3 signaling pathways. CP-690,550 also modulated innate responses to LPS in vivo through a mechanism likely involving the inhibition of STAT1 signaling. Thus, CP-690,550 may improve autoimmune diseases and prevent transplant rejection by suppressing the differentiation of pathogenic Th1 and Th17 cells as well as innate immune cell signaling.

Targeting IL-23 in human diseases

IMPORTANCE OF THE FIELD

IL-23 is one of the most intriguing cytokine for its many immunological functions, which are the basis of its important role in host defense but also of its possible contribution to the pathogenesis of several diseases.

AREAS COVERED IN THIS REVIEW

The literature and patents about IL-23 pathway and their targeting in therapeutic potential applications. Findings published within the last 5 years receive particular attention.

WHAT THE READER WILL GAIN

An overview of the emerging role of IL-23 in physiological and pathological conditions and a review of the different approaches (IL-23 pathway-based) currently used for autoimmune diseases and cancer therapies and the results obtained both in preclinical models and in clinical trials.

TAKE HOME MESSAGE

Inhibition/targeting of IL-23 may be a good and novel therapeutic strategy, especially in the treatment of diseases like psoriasis, for which current treatments show more pronounced side effects than those of IL-23-blocking and employed as part of specific patient-tailored therapies in inflammatory bowel diseases.

IL-22 defines a novel immune pathway of antifungal resistance

The role of IL-17 and Th17 cells in immunity vs. pathology associated with the human commensal Candida albicans remains controversial. Both positive and negative effects on immune resistance have been attributed to IL-17/Th17 in experimental candidiasis. In this study, we provide evidence that IL-22, which is also produced by Th17 cells, has a critical, first-line defense in candidiasis by controlling the growth of infecting yeasts as well as by contributing to the host's epithelial integrity in the absence of acquired Th1-type immunity. The two pathways are reciprocally regulated, and IL-22 is upregulated under Th1 deficiency conditions and vice versa. Whereas both IL-17A and F are dispensable for antifungal resistance, IL-22 mediates protection in IL-17RA-deficient mice, in which IL-17A contributes to disease susceptibility. Thus, our findings suggest that protective immunity to candidiasis is made up of a staged response involving an early, IL-22-dominated response followed by Th1/Treg reactivity that will prevent fungal dissemination and supply memory.

Comprehensive sequence analysis of the human IL23A gene defines new variation content and high rate of evolutionary conservation

A newly described heterodimeric cytokine, interleukin-23 (IL-23) is emerging as a key player in both the innate and the adaptive T helper (Th)17 driven immune response as well as an initiator of several autoimmune diseases. The rate-limiting element of IL-23 production is believed to be driven by expression of the unique p19 subunit encoded by IL23A. We set out to perform comprehensive DNA sequencing of this previously under-studied gene in 96 individuals from two evolutionary distinct human population groups, Southern African Bantu and European. We observed a total of 33 different DNA variants within these two groups, 22 (67%) of which are currently not reported in any available database. We further demonstrate both inter-population and intra-species sequence conservation within the coding and known regulatory regions of IL23A, supporting a critical physiological role for IL-23. We conclude that IL23A may have undergone positive selection pressure directed towards conservation, suggesting that functional genetic variants within IL23A will have a significant impact on the host immune response.

Functional biology of the IL-22-IL-22R pathway in regulating immunity and inflammation at barrier surfaces

Expression of interleukin (IL)-22, a member of the IL-10 cytokine family, has recently been reported in a number of human diseases, including mucosal-associated infections and inflammatory disorders of the intestine, skin, and joints. Both T cells and an emerging category of innate lymphoid cells are sources of IL-22, while the IL-22 receptor complex is reported to be restricted to cells of nonhematopoietic origin. The ligand-receptor distribution of IL-22-IL-22R permits immune cells to regulate responses of epithelial cells, endothelial cells, fibroblasts, and other tissue-resident stromal cells. This pathway appears to be critically important at barrier surfaces where epithelial cells play an active role in the initiation, regulation, and resolution of immune responses. Functional studies in murine model systems indicate that IL-22 has immunoregulatory properties in infection, inflammation, autoimmunity, and cancer. In these models, the functional consequences of IL-22 expression can be either pathologic or protective, depending on the context in which it is expressed. Therefore, advancing our understanding of the biology of IL-22-IL-22R may yield novel therapeutic targets in multiple human diseases. In this review, we discuss recent findings on the expression, regulation, and function of IL-22 at barrier surfaces, and offer insights into the next frontiers to be studied in this complex cytokine pathway.

T-bet-/- RAG2-/- ulcerative colitis: the role of T-bet as a peacekeeper of host-commensal relationships

Inflammatory bowel disease is a disease that reflects a disequilibrium in host-commensal homeostasis. T-bet-/-xRAG2-/- deficient mice develop a spontaneous juvenile ulcerative colitis resulting from a pro-inflammatory response to the commensal microbiota that is dendritic cell and TNF-alpha driven [schematized in Fig. 1]. The TRUC (T-bet-/- RAG2-/- ulcerative colitis) model is discussed in the broader context of the adaptive and innate immune mechanisms that regulate host-commensal relationships within the intestine.

From interleukin-23 to T-helper 17 cells: human T-helper cell differentiation revisited

Protracted inflammation leading to dysregulation of effector T-cell responses represents a common feature of a wide range of autoimmune diseases. The interleukin-12 (IL-12)/T-helper 1 (Th1) pathway was thought to be responsible for the pathogenesis of multiple chronic inflammatory diseases, including psoriasis, inflammatory bowel disease, arthritis, or multiple sclerosis, mainly through their production of interferon-gamma and its effects on macrophage activation and chemokine production. However, this initial concept of T-cell-mediated chronic inflammation required an adjustment with the discovery of an IL-12-related cytokine, designated IL-23. IL-23 was rapidly recognized for its involvement in the establishment of chronic inflammation and in the development of a Th cell subset producing IL-17, designated Th17, which is distinct from the previously reported Th1 and Th2 populations. This review aims to describe the characterization of IL-23 and its receptor, its biological activities, as well as its involvement in the development of human Th17 cells and autoimmunity.