Murine model of colonization with fungal pathogen Candida auris to explore skin tropism, host risk factors and therapeutic strategies

Candida auris is an emerging multi-drug-resistant human fungal pathogen. C. auris skin colonization results in environmental shedding, which underlies hospital transmissions, and predisposes patients to subsequent infections. We developed a murine skin topical exposure model for C. auris to dissect risk factors for colonization and to test interventions that might protect patients. We demonstrate that C. auris establishes long-term residence within the skin tissue compartment, which would elude clinical surveillance. The four clades of C. auris, with geographically distinct origins, differ in their abilities to colonize murine skin, mirroring epidemiologic findings. The IL-17 receptor signaling and specific arms of immunity protect mice from long-term C. auris skin colonization. We further determine that commonly used chlorhexidine antiseptic serves as a protective and decolonizing agent against C. auris. This translational model facilitates an integrated approach to develop strategies to combat the unfolding global outbreaks of C. auris and other skin-associated microbial pathogens.

Recapture Rate of Brodalumab in Patients With a Lapse in Treatment

The National Psoriasis Foundation has emphasized the importance of achieving skin clearance targets throughout the course of treatment. However, patients with psoriasis often stop and restart treatment for reasons such as psychological distress, dissatisfaction with treatment, inconvenience, cost, or comorbidities. Brodalumab is a fully human anti-interleukin-17 receptor A monoclonal antibody efficacious for the treatment of moderate-to-severe plaque psoriasis. This review discusses the efficacy and safety of brodalumab and other biologic therapies in patients with psoriasis who stop and restart treatment. These clinically relevant and important findings can help inform real-world treatment decisions. J Drugs Dermatol. 2020;19(4):384-387. doi:10.36849/JDD.2020.5026.

New Targeted Therapies for Uncontrolled Asthma

Mechanistic studies have improved our understanding of molecular and cellular components involved in asthma and our ability to treat severe patients. An mAb directed against IgE (omalizumab) has become an established add-on therapy for patients with uncontrolled allergic asthma and mAbs specific for IL-5 (reslizumab, mepolizumab), IL-5R (benralizumab), and IL-4R (dupilumab) have been approved as add-on treatments for uncontrolled eosinophilic (type 2) asthma. While these medications have proven highly effective, some patients with severe allergic and/or eosinophilic asthma, as well as most patients with severe non-type-2 disease, have poorly controlled disease. Agents that have recently been evaluated in clinical trials include an antibody directed against thymic stromal lymphopoietin, small molecule antagonists to the chemoattractant receptor-homologous molecule expressed on T_H2 cells (CRTH2) and the receptor for stem cell factor on mast cells (KIT), and a DNA enzyme directed at GATA3. Antibodies to IL-33 and its receptor, ST2, are being evaluated in ongoing clinical studies. In addition, a number of antagonists directed against other potential targets are under consideration for future trials, including IL-25, IL-6, TNF-like ligand 1A, CD6, and activated cell adhesion molecule (ALCAM). Clinical data from ongoing and future trials will be important in determining whether these new medications will offer benefits in place of or in addition to existing therapies for asthma.

Malignancy Rates in Brodalumab Clinical Studies for Psoriasis

Background

Brodalumab is a fully human anti–interleukin-17 receptor A monoclonal antibody efficacious for the treatment of adults with moderate-to-severe plaque psoriasis.

Objective

This study summarizes malignancy rates in psoriasis clinical studies of brodalumab.

Methods

Data were pooled from one phase II study and three large, multicenter, phase III randomized studies of brodalumab for the treatment of psoriasis, including two studies with randomization to brodalumab, ustekinumab, or placebo. Data from the 52-week (brodalumab and ustekinumab) and long-term (brodalumab) pools were summarized as exposure-adjusted or follow-up time-adjusted event rates per 100 patient-years (PY).

Results

Exposure-adjusted event rates per 100 PY at 52 weeks were lower with brodalumab (n = 4019; 3446 total PY of exposure) than with ustekinumab (n = 613; 495 total PY of exposure), including adjudicated malignancies (0.9 vs 2.6) and Surveillance, Epidemiology, and End Results (SEER)-adjudicated malignancies (0.3 vs 0.4). The exposure-adjusted event rate of adjudicated malignancies in the brodalumab group remained stable in the long-term analysis (0.9 [82 events]).

Conclusions

Rates of malignancy among brodalumab-treated patients with psoriasis were generally low.

Trial registry

ClinicalTrials.gov identifier NCT00975637; NCT01101100; NCT01708590 (AMAGINE-1); NCT01708603 (AMAGINE-2); NCT01708629 (AMAGINE-3).

Electronic supplementary material

The online version of this article (10.1007/s40257-020-00512-4) contains supplementary material, which is available to authorized users.

Treatment of Recalcitrant Acrodermatitis Continua of Hallopeau With Brodalumab

To the Editor: Acrodermatitis continua of Hallopeau (ACH) is a relatively rare chronic disorder with clinical findings of pustules and erythematous plaques on the digits.1 Although it is a variant of pustular psoriasis, it can be resistant to multiple lines of therapy. We describe for the first time a patient with recalcitrant ACH successfully treated with brodalumab, an interleukin-17 receptor A (IL-17RA) blocking antibody.

Protease activated receptor-2 mediated upregulation of IL-17 receptor signaling on airway epithelial cells is responsible for neutrophilic infiltration during acute exposure of house dust mite allergens in mice

Asthma, a chronic inflammatory disease affecting the airways is primarily caused due to immune system dysfunction. Different inhaled allergens such as house dust mites (HDM), fungi, cockroach allergens are the main contributors to allergic asthma. Protease activated receptor-2 (PAR-2) signaling plays an important role in allergic asthma through modulation of immune mediators in airway epithelial cells (AECs). Interleukin-17A (IL-17A) signals via subunits of IL-17 receptor (IL-17R), i.e. interleukin-17 receptor A (IL-17RA) and interleukin-17 receptor C (IL-17RC), and plays a necessary role in neutrophilic infiltration in response to infectious/allergenic stimuli, however it is not known if PAR-2 activation affects IL-17A/IL-17R signaling during acute exposure to house dust mite (HDM) allergens. Therefore, our study exposed mice to HDM allergens for five days and evaluated its effect on IL-17A/IL-17R signaling, chemokine/cytokines and neutrophilic inflammation in mice. Our study shows that HDM allergens upregulate IL-17A levels in the lung and IL-17RA/IL-17RC expression in AECs. PAR-2 activation by trypsin also upregulates neutrophilic influx and IL-17A/IL-17R signaling in the lung. Upregulated IL-17A/IL-17R signaling was associated with increased BAL neutrophils, pulmonary MPO activity and proinflammatory chemokines and cytokines (IL-23, IL-6, and MCP-1 in AECs/lung) in HDM exposed mice. Further, HDM-induced IL-17A, IL-17R and chemokines/cytokines were attenuated by PAR-2 antagonist, ENMD-1068. Furthermore, HDM-primed mice treated with IL-17A had greater neutrophilic inflammation and higher levels of inflammatory cytokines/chemokines than PBS-exposed mice treated with IL-17A. This proposes that acute exposure to HDM allergens activate AECs at a very early stage where PAR-2/IL-17R signaling serves a crucial role in neutrophilic inflammation.

Targeting the IL-23/IL-17 Pathway in Psoriasis: the Search for the Good, the Bad and the Ugly

New promising treatments have been developed for psoriasis that target different parts of the interleukin (IL)-23/IL-17 pathway. This approach is believed to be more disease specific, and sparing the T helper 1 pathway might prevent serious long-term adverse events. Moreover, superior Psoriasis Area and Severity Index improvements are observed, which has redefined treatment goals in psoriasis. The new molecules can be divided into different categories, according to the target: blocking agents can target the upstream cytokine IL-23 or the downstream IL-17. In the latter, a variety of targets exist, such as the ligands IL-17A and IL-17F, or a combination thereof, or a subunit of the receptor, IL-17RA. Each target seems to have its own set of advantages and pitfalls, which will impact the treatment decision in clinical practice. In this review, we summarize the current knowledge on the different inhibitors of the IL-23/IL-17 pathway. Furthermore, we briefly discuss the role of IL-17 in other diseases and comorbidities. Finally, we discuss how comprehensive knowledge is needed for the prescribing physician in order to make the most appropriate therapeutic choice for each individual patient.

Act1 is a negative regulator in T and B cells via direct inhibition of STAT3

Although Act1 (adaptor for IL-17 receptors) is necessary for IL-17-mediated inflammatory responses, Act1- (but not Il17ra-, Il17rc-, or Il17rb-) deficient mice develop spontaneous SLE- and Sjögren's-like diseases. Here, we show that Act1 functions as a negative regulator in T and B cells via direct inhibition of STAT3. Mass spectrometry analysis detected an Act1-STAT3 complex, deficiency of Act1 (but not Il17ra-, Il17rc-, or Il17rb) results in hyper IL-23- and IL-21-induced STAT3 activation in T and B cells, respectively. IL-23R deletion or blockade of IL-21 ameliorates SLE- and Sjögren's-like diseases in Act1-/- mice. Act1 deficiency results in hyperactivated follicular Th17 cells with elevated IL-21 expression, which promotes T-B cell interaction for B cell expansion and antibody production. Moreover, anti-IL-21 ameliorates the SLE- and Sjögren's-like diseases in Act1-deficient mice. Thus, IL-21 blocking antibody might be an effective therapy for treating SLE- and Sjögren's-like syndrome in patients containing Act1 mutation.

Bacteroides fragilis Toxin Coordinates a Pro-carcinogenic Inflammatory Cascade via Targeting of Colonic Epithelial Cells

Pro-carcinogenic bacteria have the potential to initiate and/or promote colon cancer, in part via immune mechanisms that are incompletely understood. Using ApcMin mice colonized with the human pathobiont enterotoxigenic Bacteroides fragilis (ETBF) as a model of microbe-induced colon tumorigenesis, we show that the Bacteroides fragilis toxin (BFT) triggers a pro-carcinogenic, multi-step inflammatory cascade requiring IL-17R, NF-κB, and Stat3 signaling in colonic epithelial cells (CECs). Although necessary, Stat3 activation in CECs is not sufficient to trigger ETBF colon tumorigenesis. Notably, IL-17-dependent NF-κB activation in CECs induces a proximal to distal mucosal gradient of C-X-C chemokines, including CXCL1, that mediates the recruitment of CXCR2-expressing polymorphonuclear immature myeloid cells with parallel onset of ETBF-mediated distal colon tumorigenesis. Thus, BFT induces a pro-carcinogenic signaling relay from the CEC to a mucosal Th17 response that results in selective NF-κB activation in distal colon CECs, which collectively triggers myeloid-cell-dependent distal colon tumorigenesis.

IL-17 Receptor A Maintains and Protects the Skin Barrier To Prevent Allergic Skin Inflammation

Atopic dermatitis (AD) is a common inflammatory skin disease affecting up to 20% of children and 3% of adults worldwide and is associated with dysregulation of the skin barrier. Although type 2 responses are implicated in AD, emerging evidence indicates a potential role for the IL-17A signaling axis in AD pathogenesis. In this study we show that in the filaggrin mutant mouse model of spontaneous AD, IL-17RA deficiency (Il17ra-/- ) resulted in severe exacerbation of skin inflammation. Interestingly, Il17ra-/- mice without the filaggrin mutation also developed spontaneous progressive skin inflammation with eosinophilia, as well as increased levels of thymic stromal lymphopoietin (TSLP) and IL-5 in the skin. Il17ra-/- mice have a defective skin barrier with altered filaggrin expression. The barrier dysregulation and spontaneous skin inflammation in Il17ra-/- mice was dependent on TSLP, but not the other alarmins IL-25 and IL-33. The associated skin inflammation was mediated by IL-5-expressing pathogenic effector Th2 cells and was independent of TCRγδ T cells and IL-22. An absence of IL-17RA in nonhematopoietic cells, but not in the hematopoietic cells, was required for the development of spontaneous skin inflammation. Skin microbiome dysbiosis developed in the absence of IL-17RA, with antibiotic intervention resulting in significant amelioration of skin inflammation and reductions in skin-infiltrating pathogenic effector Th2 cells and TSLP. This study describes a previously unappreciated protective role for IL-17RA signaling in regulation of the skin barrier and maintenance of skin immune homeostasis.

Intraepithelial neutrophils in pediatric severe asthma are associated with better lung function

BACKGROUND

Neutrophils and IL-17A have been linked mechanistically in models of allergic airways disease and have been associated with asthma severity. However, their role in pediatric asthma is unknown.

OBJECTIVES

We sought to investigate the role of neutrophils and the IL-17A pathway in mediating pediatric severe therapy-resistant asthma (STRA).

METHODS

Children with STRA (n = 51; age, 12.6 years; range, 6-16.3 years) and controls without asthma (n = 15; age, 4.75 years; range, 1.6-16 years) underwent clinically indicated fiberoptic bronchoscopy, bronchoalveolar lavage (BAL), endobronchial brushings, and biopsy. Neutrophils, IL-17A, and IL-17RA-expressing cells and levels of IL-17A and IL-22 were quantified in BAL and biopsies and related to clinical features. Primary bronchial epithelial cells were stimulated with IL-17A and/or IL-22, with and without budesonide.

RESULTS

Children with STRA had increased intraepithelial neutrophils, which positively correlated with FEV1 %predicted (r = 0.43; P = .008). Neutrophilhigh patients also had better symptom control, despite lower dose maintenance inhaled steroids. Submucosal neutrophils were not increased in children with STRA. Submucosal and epithelial IL-17A-positive cells and BAL IL-17A and IL-22 levels were similar in children with STRA and controls. However, there were significantly more IL-17RA-positive cells in the submucosa and epithelium in children with STRA compared with controls (P = .001). Stimulation of primary bronchial epithelial cells with IL-17A enhanced mRNA expression of IL-17RA and increased release of IL-8, even in the presence of budesonide.

CONCLUSIONS

A proportion of children with STRA exhibit increased intraepithelial airway neutrophilia that correlated with better lung function. STRA was also characterized by increased airway IL-17RA expression. These data suggest a potential beneficial rather than adverse role for neutrophils in pediatric severe asthma pathophysiology.

Blocking IL-17A Alleviates Diabetic Retinopathy in Rodents

BACKGROUND/AIMS

Interleukin (IL)-17A, a proinflammatory cytokine, has been implicated in several autoimmune diseases. However, it is unclear whether IL-17A is involved in diabetic retinopathy (DR), one of the most serious complications of autoimmune diabetes. This study aimed to demonstrate that IL-17A exacerbates DR by affecting retinal Müller cell function.

METHODS

High glucose (HG)-treated rat Müller cell line (rMC-1) was exposed to IL-17A, anti-IL-17A-neutralizing monoclonal antibody (mAb) or/and anti-IL-17 receptor (R)A-neutralizing mAb for 24 h. For in vivo study, DR was induced by intraperitoneal injections of streptozotocin (STZ). DR model mice were treated with anti-IL-17A mAb or anti-IL-17RA mAb in the vitreous cavity. Mice that were prepared for retinal angiography were sacrificed two weeks after intravitreal injection, while the rest were sacrificed two days after intravitreal injection.

RESULTS

IL-17A production and IL-17RA expression were increased in both HG-treated rMC-1 and DR retina. HG induced rMC-1 activation and dysfunction, as determined by the increased GFAP, VEGF and glutamate levels as well as the downregulated GS and EAAT1 expression. IL-17A exacerbated the HG-induced rMC-1 functional disorders, whereas either anti-IL-17A mAb or anti-IL-17RA mAb alleviated the HG-induced rMC-1 disorders. Intravitreal injections with anti-IL-17A mAb or anti-IL-17RA mAb in DR model mice reduced Müller cell dysfunction, vascular leukostasis, vascular leakage, tight junction protein downregulation and ganglion cell apoptosis in the retina.

CONCLUSIONS

IL-17A aggravates DR-like pathology at least partly by impairing retinal Müller cell function. Blocking IL-17A is a potential therapeutic strategy for DR.

The flavonoid cyanidin blocks binding of the cytokine interleukin-17A to the IL-17RA subunit to alleviate inflammation in vivo

Cyanidin, a key flavonoid that is present in red berries and other fruits, attenuates the development of several diseases, including asthma, diabetes, atherosclerosis, and cancer, through its anti-inflammatory effects. We investigated the molecular basis of cyanidin action. Through a structure-based search for small molecules that inhibit signaling by the proinflammatory cytokine interleukin-17A (IL-17A), we found that cyanidin specifically recognizes an IL-17A binding site in the IL-17A receptor subunit (IL-17RA) and inhibits the IL-17A/IL-17RA interaction. Experiments with mice demonstrated that cyanidin inhibited IL-17A-induced skin hyperplasia, attenuated inflammation induced by IL-17-producing T helper 17 (TH17) cells (but not that induced by TH1 or TH2 cells), and alleviated airway hyperreactivity in models of steroid-resistant and severe asthma. Our findings uncover a previously uncharacterized molecular mechanism of action of cyanidin, which may inform its further development into an effective small-molecule drug for the treatment of IL-17A-dependent inflammatory diseases and cancer.

Interluekin-17A (IL17A)

The discovery of the key roles of interleukin-17A (IL-17A) and IL-17A producing cells in inflammation, autoimmune diseases and host defense has led to the experimental targeting of the IL-17A pathway in animal models of diseases as well as in clinical trials in humans. These therapeutic agents include biological products that target IL-17A and IL-23, an upstream regulator of IL-17A production. IL-17A producing T helper cells (Th17 cells) are a distinct lineage from the Th1 and Th2 CD4+ lineages and have been suggested to represent a good drug target in certain inflammatory conditions. Targeting IL-17A has been proven to be a good approach as anti-IL-17A is FDA approved for the treatment of psoriasis in 2015. In host defense, IL-17A has been shown to be mostly beneficial against infection caused by extracellular bacteria and fungi. This review will overview the discovery of IL-17A, the receptors used by this cytokine and its role in mucosal immunity and inflammation.

Controlled Mycobacterium tuberculosis infection in mice under treatment with anti-IL-17A or IL-17F antibodies, in contrast to TNFα neutralization

Antibodies targeting IL-17A or its receptor IL-17RA show unprecedented efficacy in the treatment of autoimmune diseases such as psoriasis. These therapies, by neutralizing critical mediators of immunity, may increase susceptibility to infections. Here, we compared the effect of antibodies neutralizing IL-17A, IL-17F or TNFα on murine host responses to Mycobacterium tuberculosis infection by evaluating lung transcriptomic, microbiological and histological analyses. Coinciding with a significant increase of mycobacterial burden and pathological changes following TNFα blockade, gene array analyses of infected lungs revealed major changes of inflammatory and immune gene expression signatures 4 weeks post-infection. Specifically, gene expression associated with host-pathogen interactions, macrophage recruitment, activation and polarization, host-antimycobacterial activities, immunomodulatory responses, as well as extracellular matrix metallopeptidases, were markedly modulated by TNFα blockade. IL-17A or IL-17F neutralization elicited only mild changes of few genes without impaired host resistance four weeks after M. tuberculosis infection. Further, the absence of both IL-17RA and IL-22 pathways in genetically deficient mice did not profoundly compromise host control of M. tuberculosis over a 6-months period, ruling out potential compensation between these two pathways, while TNFα-deficient mice succumbed rapidly. These data provide experimental confirmation of the low clinical risk of mycobacterial infection under anti-IL-17A therapy, in contrast to anti-TNFα treatment.

IL-17 Promotes Neutrophil-Mediated Immunity by Activating Microvascular Pericytes and Not Endothelium

A classical hallmark of acute inflammation is neutrophil infiltration of tissues, a multistep process that involves sequential cell-cell interactions of circulating leukocytes with IL-1- or TNF-activated microvascular endothelial cells (ECs) and pericytes (PCs) that form the wall of the postcapillary venules. The initial infiltrating cells accumulate perivascularly in close proximity to PCs. IL-17, a proinflammatory cytokine that acts on target cells via a heterodimeric receptor formed by IL-17RA and IL-17RC subunits, also promotes neutrophilic inflammation but its effects on vascular cells are less clear. We report that both cultured human ECs and PCs strongly express IL-17RC and, although neither cell type expresses much IL-17RA, PCs express significantly more than ECs. IL-17, alone or synergistically with TNF, significantly alters inflammatory gene expression in cultured human PCs but not ECs. RNA sequencing analysis identifies many IL-17-induced transcripts in PCs encoding proteins known to stimulate neutrophil-mediated immunity. Conditioned media from IL-17-activated PCs, but not ECs, induce pertussis toxin-sensitive neutrophil polarization, likely mediated by PC-secreted chemokines, and they also stimulate neutrophil production of proinflammatory molecules, including TNF, IL-1α, IL-1β, and IL-8. Furthermore, IL-17-activated PCs, but not ECs, can prolong neutrophil survival by producing G-CSF and GM-CSF, delaying the mitochondrial outer membrane permeabilization and caspase-9 activation. Importantly, neutrophils exhibit enhanced phagocytic capacity after activation by conditioned media from IL-17-treated PCs. We conclude that PCs, not ECs, are the major target of IL-17 within the microvessel wall and that IL-17-activated PCs can modulate neutrophil functions within the perivascular tissue space.

IL-17RA in Non-Hematopoietic Cells Controls CXCL-1 and 5 Critical to Recruit Neutrophils to the Lung of Mycobacteria-Infected Mice during the Adaptive Immune Response

During chronic infection with Mycobacterium tuberculosis (Mtb), bacilli multiplication is constrained within lung granulomas until excessive inflammation destroys the lung. Neutrophils are recruited early and participate in granuloma formation, but excessive neutrophilia exacerbates the tuberculosis disease. Neutrophils thus appear as potential targets for therapeutic interventions, especially in patients for whom no antibiotic treatment is possible. Signals that regulate neutrophil recruitment to the lung during mycobacterial infection need to be better understood. We demonstrated here, in the mouse model, that neutrophils were recruited to the lung in two waves after intranasal infection with virulent Mtb or the live attenuated vaccine strain Bacillus Calmette Guérin (BCG). A first wave of neutrophils was swiftly recruited, followed by a subsequent adaptive wave that reached the lung together with IFN-γ- and IL-17A-producing T cells. Interestingly, the second neutrophil wave did not participate to mycobacteria control in the lung and established contacts with T cells. The adaptive wave was critically dependent on the expression of IL-17RA, the receptor for IL-17A, expressed in non-hematopoietic cells. In absence of this receptor, curtailed CXCL-1 and 5 production in the lung restrained neutrophil recruitment. CXCL-1 and 5 instillation reconstituted lung neutrophil recruitment in BCG-infected IL17RA-/- mice.

Human mast cells are major IL-22 producers in patients with psoriasis and atopic dermatitis

BACKGROUND

Psoriasis is a systemic inflammatory disease in which IL-17 and IL-22 levels are markedly increased in the skin and blood. The prevalent concept, using skin cells that are isolated from psoriatic plaques and examined after cell expansion and in vitro stimulation, is that IL-17 and IL-22 production essentially results from T cells and the rare type 3 innate lymphoid cells.

OBJECTIVE

We sought to examine the cellular source of IL-17A and IL-22 at the protein and transcriptional single-cell level immediately after ex vivo skin cell isolation from psoriatic plaques.

METHODS

Skin biopsy specimens were collected from patients with psoriasis, as well as from patients with atopic dermatitis. Cell suspensions were prepared by combining mild enzymatic digestion and mechanical dissociation and analyzed for cytokine expression without prior in vitro culture and stimulation. Expression of IL-17 and IL-22 was quantified at the protein and mRNA single-cell level by using flow cytometry.

RESULTS

IL-22 is predominantly expressed by CD3(-)c-Kit(+) cells relative to CD3(+) T cells in lesional skin of patients with psoriasis and patients with atopic dermatitis. Strikingly, we identified c-Kit(+)FcεRI(+) mast cells as major IL-22 producers. The proportion of mast cells that produce IL-22 ranges from 20% to 80% in patients with psoriasis or those with atopic dermatitis. Skin mast cells express IL-22 and IL-17 mRNA. Conversely, IL-17-producing T cells outnumber IL-17-producing mast cells, which also express IL-17 receptor.

CONCLUSION

Human skin mast cells are previously unrecognized IL-22 producers. We further established that skin mast cells express IL-17. Thus mast cells might play an important role in the physiopathology of chronic inflammatory skin disorders.

IL-17-Mediated Immunity to the Opportunistic Fungal Pathogen Candida albicans

IL-17 (IL-17A) has emerged as a key mediator of protection against extracellular microbes, but this cytokine also drives pathology in various autoimmune diseases. Overwhelming data in both humans and mice reveal a clear and surprisingly specific role for IL-17 in protection against the fungus Candida albicans, a commensal microbe of the human oral cavity, gastrointestinal tract, and reproductive mucosa. The IL-17 pathway regulates antifungal immunity through upregulation of proinflammatory cytokines, including IL-6, neutrophil-recruiting chemokines (e.g., CXCL1 and CXCL5), and antimicrobial peptides (e.g., defensins), which act in concert to limit fungal overgrowth. This review focuses on diseases caused by C. albicans, the role of IL-17-mediated immunity in candidiasis, and the implications for clinical therapies for both autoimmune conditions and fungal infections.

Unexpected Role for Adaptive αβTh17 Cells in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a devastating disorder characterized by increased alveolar permeability with no effective treatment beyond supportive care. Current mechanisms underlying ARDS focus on alveolar endothelial and epithelial injury caused by products of innate immune cells and platelets. However, the role of adaptive immune cells in ARDS remains largely unknown. In this study, we report that expansion of Ag-specific αβTh17 cells contributes to ARDS by local secretion of IL-17A, which in turn directly increases alveolar epithelial permeability. Mice with a highly restrictive defect in Ag-specific αβTh17 cells were protected from experimental ARDS induced by a single dose of endotracheal LPS. Loss of IL-17 receptor C or Ab blockade of IL-17A was similarly protective, further suggesting that IL-17A released by these cells was responsible for this effect. LPS induced a rapid and specific clonal expansion of αβTh17 cells in the lung, as determined by deep sequencing of the hypervariable CD3RβVJ region of the TCR. Our findings could be relevant to ARDS in humans, because we found significant elevation of IL-17A in bronchoalveolar lavage fluid from patients with ARDS, and rIL-17A directly increased permeability across cultured human alveolar epithelial monolayers. These results reveal a previously unexpected role for adaptive immune responses that increase alveolar permeability in ARDS and suggest that αβTh17 cells and IL-17A could be novel therapeutic targets for this currently untreatable disease.

High IFN-γ and low SLPI mark severe asthma in mice and humans

Severe asthma (SA) is a challenge to control, as patients are not responsive to high doses of systemic corticosteroids (CS). In contrast, mild-moderate asthma (MMA) is responsive to low doses of inhaled CS, indicating that Th2 cells, which are dominant in MMA, do not solely orchestrate SA development. Here, we analyzed broncholalveolar lavage cells isolated from MMA and SA patients and determined that IFN-γ (Th1) immune responses are exacerbated in the airways of individuals with SA, with reduced Th2 and IL-17 responses. We developed a protocol that recapitulates the complex immune response of human SA, including the poor response to CS, in a murine model. Compared with WT animals, Ifng-/- mice subjected to this SA model failed to mount airway hyperresponsiveness (AHR) without appreciable effect on airway inflammation. Conversely, AHR was not reduced in Il17ra-/- mice, although airway inflammation was lower. Computer-assisted pathway analysis tools linked IFN-γ to secretory leukocyte protease inhibitor (SLPI), which is expressed by airway epithelial cells, and IFN-γ inversely correlated with SLPI expression in SA patients and the mouse model. In mice subjected to our SA model, forced SLPI expression decreased AHR in the absence of CS, and it was further reduced when SLPI was combined with CS. Our study identifies a distinct immune response in SA characterized by a dysregulated IFN-γ/SLPI axis that affects lung function.

The elevated expression of Th17-related cytokines and receptors is associated with skin lesion severity in early systemic sclerosis

OBJECTIVE

The objective was to survey the expression and localization of Th17-related cytokines and their correlation with skin lesion severity in early systemic sclerosis (SSc).

METHODS

The mRNA expression was detected by real-time quantitative polymerase chain reaction (RT-qPCR) from 21 SSc patients and 12 healthy controls (HC). The protein expression was examined by immunohistochemistry (IHC) and Western blotting.

RESULTS

The RT-qPCR analysis showed a significantly higher expression of IL-17A, IL-21, IL-22, IL-26, IL-17RA, IL-21R, and IL-22R1 mRNA; consistently, the IHC analysis showed an over-expression of IL-17RA, IL-21R and IL-22R1 and the Western blotting analysis showed an over-expression of IL-17A, IL-21, IL-21R and IL-22R1 in early SSc skin lesions. The mRNA levels of IL-21 were higher in diffuse cutaneous than limited cutaneous SSc lesions. The mRNA expression of IL-26, IL-22, IL-22R1, mRNA and protein expression of IL-17A, IL-21, IL-21R were positively correlated with the modified Rodnan skin score of SSc. In addition, the mRNA levels of ICAM-1 were positively correlated with IL-17A/IL-17RA, and VEGFA and IL-4 were both positively correlated with IL-21/IL-21R, while TGF-β were moderately negatively correlated with IL-22/IL-22R1.

CONCLUSIONS

Th17 cytokines contribute to progression in early SSc skin lesions. IL-21/IL-21R could act as potential biomarkers presenting early SSc skin lesions severity.

IL-17 Enhances Chemotaxis of Primary Human B Cells during Asthma

IL-17 is a pro-inflammatory mediator that is believed to play a critical role in regulating tissue inflammation during asthma, COPD, as well as other inflammatory disorders. The level of expression of IL-17 has been shown to be upregulated in lung bronchial tissue of asthmatic patients. Several reports have provided further evidence that this cytokine could play a key role in enhancing the migration of inflammatory as well as structural cells of the bronchial lung tissue during asthma and COPD. B cell infiltration to sites of inflammation during inflammatory disorders such as bowel disease, asthma and COPD has been reported. Accordingly, in this study we hypothesized that IL-17 may exert a chemotactic effect on primary B cells during asthma. We observed that B cells from asthmatic patients expressed significantly higher levels of IL-17RA and IL-17RC, compared to those of healthy subjects. Using an in-vitro migration assay, B cells were shown to migrate towards both IL-17A and IL-17F. Interestingly, blocking IL-17A and IL-17F signaling using either anti-IL-17R antibodies or MAP kinase inhibitors prevented in vitro migration of B cell towards IL-17. These observations indicate a direct chemotactic effect of IL-17 cytokines on primary peripheral blood B cells with higher effect being on asthmatic B cells. These findings revealed a key role for IL-17 in enhancing the migration of B cells to the lung tissue during asthma or COPD.

Safety and efficacy of brodalumab for psoriasis after 120 weeks of treatment

BACKGROUND

Brodalumab (anti-interleukin-17-receptor antibody) was effective in treating moderate to severe psoriasis in a 12-week, dose-ranging, placebo-controlled trial.

OBJECTIVE

We sought to evaluate efficacy and safety of long-term brodalumab treatment.

METHODS

In this interim analysis at week 120 of an open-label extension study, patients received brodalumab 210 mg every 2 weeks. Protocol amendments reduced the dose (140 mg) in patients weighing 100 kg or less and subsequently increased the dose (210 mg) in patients with inadequate responses. Efficacy was measured by static physician global assessment and 75% or greater, 90% or greater, or 100% improvement in Psoriasis Area and Severity Index score (PASI-75, PASI-90, and PASI-100, respectively).

RESULTS

Of 181 patients, 144 completed week 120. Static physician global assessment scores of clear/almost clear and clear were achieved by 90% and 63% of patients, respectively, at week 12 and by 72% and 51% at week 120. The PASI-75, PASI-90, and PASI-100 response rates at week 12 (95%/85%/63%) were sustained through week 120 (86%/70%/51%). Most commonly reported adverse events were nasopharyngitis (26.5%), upper respiratory tract infection (19.9%), arthralgia (16.0%), and back pain (11.0%). Four patients had grade-2 absolute neutrophil count.

LIMITATIONS

There was no control group in this open-label extension.

CONCLUSION

Brodalumab demonstrated sustained clinical response and an acceptable safety profile through 120 weeks in patients with moderate to severe psoriasis.

Mitigated Tregs and augmented Th17 cells and cytokines are associated with severity of experimental autoimmune neuritis

Experimental autoimmune neuritis (EAN), an animal model of human Guillain-Barré syndrome, has long been considered as a T helper (Th) 1 cell-mediated autoimmune disorder. However, deficiency of IFN-γ, a signature Th1 cytokine, aggravated EAN, with features of elevated production of IL-17A, despite an alleviated systemic Th1 immune response. We hypothesized that Th17 cells and their cytokines might play a pathogenic role in EAN. To further clarify the roles of these Th and regulatory T cell (Treg) cytokines in the pathogenesis of EAN and their interrelationship, we investigated the expression of Th1/Th2/Th17/Treg cytokines in EAN in this study. We found that the levels of Th17 cells and IL-17A in cauda equina (CE)-infiltrating cells and splenic mononuclear cells (MNCs) as well as in serum paralleled the disease evolution, which increased progressively during the initiation stage and reached higher value at the peak of EAN. The same pattern was also noticed for the expression of IL-22. The diverse expression profiles of FoxP3, IL-17 receptors A and C were seen in CE-infiltrating cells and splenic MNCs in EAN. These findings indicate a major pro-inflammatory role of Th17 cells and IL-17A in the pathogenesis of EAN. Therapeutic interventions may be focused upon inhibiting Th17 cells and their cytokines in the early phase of EAN, so as to delay and suppress clinical signs of the disease, which has relevance for future studies on pathogenesis and treatment of GBS in humans.

Cytokine-regulated neutrophil recruitment is required for brain but not spinal cord inflammation during experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an autoimmune disease in which inflammatory lesions lead to tissue injury in the brain and/or spinal cord. The specific sites of tissue injury are strong determinants of clinical outcome in MS, but the pathways that determine whether damage occurs in the brain or spinal cord are not understood. Previous studies in mouse models of MS demonstrated that IFN-γ and IL-17 regulate lesion localization within the brain; however, the mechanisms by which these cytokines mediate their effects have not been identified. In the present study, we show that IL-17 promoted, but IFN-γ inhibited, ELR(+) chemokine-mediated neutrophil recruitment to the brain, and that neutrophil infiltration was required for parenchymal tissue damage in the brain. In contrast, IFN-γ promoted ELR(+) chemokine expression and neutrophil recruitment to the spinal cord. Surprisingly, tissue injury in the spinal cord did not exhibit the same dependence on neutrophil recruitment that was observed for the brain. Our results demonstrate that the brain and spinal cord exhibit distinct sensitivities to cellular mediators of tissue damage, and that IL-17 and IFN-γ differentially regulate recruitment of these mediators to each microenvironment. These findings suggest an approach toward tailoring therapies for patients with distinct patterns of neuroinflammation.

Propionibacterium acnes Induces an IL-17 Response in Acne Vulgaris that Is Regulated by Vitamin A and Vitamin D

Acne vulgaris is the most common skin disorder affecting millions of people worldwide and inflammation resulting from the immune response targeting Propionibacterium acnes has a significant role in its pathogenesis. In this study, we have demonstrated that P. acnes is a potent inducer of T helper 17 (Th17) and Th1, but not Th2 responses in human peripheral blood mononuclear cells (PBMCs). P. acnes stimulated expression of key Th17-related genes, including IL-17A, RORα, RORc, IL-17RA, and IL-17RC, and triggered IL-17 secretion from CD4(+), but not from CD8(+) T cells. Supernatants from P. acnes-stimulated PBMCs were sufficient to promote the differentiation of naive CD4(+)CD45RA T cells into Th17 cells. Furthermore, we found that the combination of IL-1β, IL-6, and transforming growth factor-β-neutralizing antibodies completely inhibited P. acnes-induced IL-17 production. Importantly, we showed that IL-17-expressing cells were present in skin biopsies from acne patients but not from normal donors. Finally, vitamin A (all-trans retinoic acid) and vitamin D (1,25-dihydroxyvitamin D3) inhibited P. acnes-induced Th17 differentiation. Together, our data demonstrate that IL-17 is induced by P. acnes and expressed in acne lesions and that both vitamin A and D could be effective tools to modulate Th17-mediated diseases such as acne.

A phase Ib multiple ascending dose study evaluating safety, pharmacokinetics, and early clinical response of brodalumab, a human anti-IL-17R antibody, in methotrexate-resistant rheumatoid arthritis

INTRODUCTION

The aim of this study was to evaluate the safety, pharmacokinetics, and clinical response of brodalumab (AMG 827), a human, anti-IL-17 receptor A (IL-17RA) monoclonal antibody in subjects with moderate-to-severe rheumatoid arthritis (RA).

METHODS

This phase Ib, randomized, placebo-controlled, double-blind multiple ascending dose study enrolled subjects with moderate to severe RA (≥ 6/66 swollen and ≥ 8/68 tender joints). Subjects were randomized 3:1 to receive brodalumab (50 mg, 140 mg, or 210 mg subcutaneously every two weeks for 6 doses per group; or 420 mg or 700 mg intravenously every 4 weeks for two doses per group) or placebo. Endpoints included incidence of adverse events (AEs) and pharmacokinetics. Exploratory endpoints included pharmacodynamics, and improvements in RA clinical metrics.

RESULTS

Forty subjects were randomized to investigational product; one subject discontinued due to worsening of RA (placebo). The study was not designed to assess efficacy. AEs were reported by 70% (7/10) of placebo subjects and 77% (22/30) of brodalumab subjects. Three serious AEs were reported in two subjects; there were no opportunistic infections. Brodalumab treatment resulted in inhibition of IL-17 receptor signaling and receptor occupancy on circulating leukocytes. No treatment effects were observed with individual measures of RA disease activity. On day 85 (week 13) 37% (11/30) of brodalumab subjects and 22% (2/9) of placebo subjects achieved ACR20; 7% (2/30) brodalumab subjects and 11% (1/9) of placebo subjects achieved ACR50; and 0% (0/30) brodalumab subjects and 0% (0/9) of placebo subjects achieved ACR70.

CONCLUSIONS

Multiple dose administration of brodalumab was tolerated in subjects with active RA. There was no evidence of a clinical response to brodalumab in subjects with RA.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT00771030.

An ACT1 mutation selectively abolishes interleukin-17 responses in humans with chronic mucocutaneous candidiasis

Patients with inborn errors of interleukin-17F (IL-17F) or IL-17RA display chronic mucocutaneous candidiasis (CMC). We report a biallelic missense mutation (T536I) in the adaptor molecule ACT1 in two siblings with CMC. The mutation, located in the SEFIR domain, abolished the homotypic interaction of ACT1 with IL-17 receptors, with no effect on homodimerization. The patients' fibroblasts failed to respond to IL-17A and IL-17F, and their T cells to IL-17E. By contrast, healthy individuals homozygous for the common variant D10N, located in the ACT1 tumor necrosis factor receptor-associated factor-interacting domain and previously associated with psoriasis, had impaired, but not abolished, responses to IL-17 cytokines. SEFIR-independent interactions of ACT1 with other proteins, such as CD40, heat shock protein 70 (HSP70) and HSP90, were not affected by the T536I mutation. Overall, human IL-17A and IL-17F depend on ACT1 to mediate protective mucocutaneous immunity. Moreover, other ACT1-dependent IL-17 cytokines seem to be largely redundant in host defense.

An alternative pathway of imiquimod-induced psoriasis-like skin inflammation in the absence of interleukin-17 receptor a signaling

Topical application of imiquimod (IMQ) on the skin of mice induces inflammation with common features found in psoriatic skin. Recently, it was postulated that IL-17 has an important role both in psoriasis and in the IMQ model. To further investigate the impact of IL-17RA signaling in psoriasis, we generated IL-17 receptor A (IL-17RA)-deficient mice (IL-17RA(del)) and challenged these mice with IMQ. Interestingly, the disease was only partially reduced and delayed but not abolished when compared with controls. In the absence of IL-17RA, we found persisting signs of inflammation such as neutrophil and macrophage infiltration within the skin. Surprisingly, already in the naive state, the skin of IL-17RA(del) mice contained significantly elevated numbers of Th17- and IL-17-producing γδ T cells, assuming that IL-17RA signaling regulates the population size of Th17 and γδ T cells. Upon IMQ treatment of IL-17RA(del) mice, these cells secreted elevated amounts of tumor necrosis factor-α, IL-6, and IL-22, accompanied by increased levels of the chemokine CXCL2, suggesting an alternative pathway of neutrophil and macrophage skin infiltration. Hence, our findings have major implications in the potential long-term treatment of psoriasis by IL-17-targeting drugs.

IL-17RA signaling reduces inflammation and mortality during Trypanosoma cruzi infection by recruiting suppressive IL-10-producing neutrophils

Members of the IL-17 cytokine family play an important role in protection against pathogens through the induction of different effector mechanisms. We determined that IL-17A, IL-17E and IL-17F are produced during the acute phase of T. cruzi infection. Using IL-17RA knockout (KO) mice, we demonstrate that IL-17RA, the common receptor subunit for many IL-17 family members, is required for host resistance during T. cruzi infection. Furthermore, infected IL-17RA KO mice that lack of response to several IL-17 cytokines showed amplified inflammatory responses with exuberant IFN-γ and TNF production that promoted hepatic damage and mortality. Absence of IL-17RA during T. cruzi infection resulted in reduced CXCL1 and CXCL2 expression in spleen and liver and limited neutrophil recruitment. T. cruzi-stimulated neutrophils secreted IL-10 and showed an IL-10-dependent suppressive phenotype in vitro inhibiting T-cell proliferation and IFN-γ production. Specific depletion of Ly-6G+ neutrophils in vivo during T. cruzi infection raised parasitemia and serum IFN-γ concentration and resulted in increased liver pathology in WT mice and overwhelming wasting disease in IL-17RA KO mice. Adoptively transferred neutrophils were unable to migrate to tissues and to restore resistant phenotype in infected IL-17RA KO mice but migrated to spleen and liver of infected WT mice and downregulated IFN-γ production and increased survival in an IL-10 dependent manner. Our results underscore the role of IL-17RA in the modulation of IFN-γ-mediated inflammatory responses during infections and uncover a previously unrecognized regulatory mechanism that involves the IL-17RA-mediated recruitment of suppressive IL-10-producing neutrophils.

IL-17 family is comprised for six members (IL-17A to F) that have been reported to play protective effects in bacterial and fungal infections and contradictory roles in parasite infections. Using mice deficient in IL-17RA, the common receptor subunit for many IL-17 family members, we determined that these cytokines are required for host protection against the parasite Trypanosoma cruzi. In absence of IL-17 signaling, mice developed an aggravated infection with similar levels of parasite in blood but increased inflammation and tissue damage of vital organs such as liver. We evaluated the mechanisms underlying this increased susceptibility and determined that the absence of IL-17RA caused a reduced arrival of neutrophils to organs such as spleen and liver. Neutrophils are phagocytic cells with abilities to directly destroy pathogens and also to regulate the inflammatory response. Indeed, we determined that neutrophils from T. cruzi infected mice are poisoned to secrete the regulatory cytokine IL-10. Finally, by experiments of depletion and adoptive transfer of neutrophils we determined that, during T. cruzi infection, IL-17RA is required for the recruitment of neutrophils that destroy the parasite and that also regulate inflammatory responses and collateral tissue damage by secreting IL-10.

Brodalumab, an anti-interleukin-17-receptor antibody for psoriasis

BACKGROUND

In this phase 2, randomized, double-blind, placebo-controlled, dose-ranging study, we assessed the efficacy and safety of brodalumab (AMG 827), a human anti-interleukin-17-receptor monoclonal antibody, for the treatment of moderate-to-severe plaque psoriasis.

METHODS

We randomly assigned patients with a score of 12 or higher on the psoriasis area-and-severity index (PASI, on which scores range from 0 to 72, with higher scores indicating more severe disease) and with 10% or more of their body-surface area affected by psoriasis to receive brodalumab (70 mg, 140 mg, or 210 mg at day 1 and weeks 1, 2, 4, 6, 8, and 10 or 280 mg monthly) or placebo. The primary end point was the percentage improvement from baseline in the PASI score at week 12. Secondary end points included improvement of at least 75% and at least 90% in the PASI score and the score on the static physician's global assessment at week 12.

RESULTS

A total of 198 patients underwent randomization. At week 12, the mean percentage improvements in the PASI score were 45.0% among patients receiving 70 mg of brodalumab, 85.9% among those receiving 140 mg, 86.3% among those receiving 210 mg, 76.0% among those receiving 280 mg, and 16.0% among those receiving placebo (P<0.001 for all comparisons with placebo). An improvement of at least 75% and at least 90% in the PASI score at week 12 was seen in 77% and 72%, respectively, of the patients in the 140-mg brodalumab group and in 82% and 75%, respectively, of the patients in the 210-mg group, as compared with 0% in the placebo group (P<0.001 for all comparisons). The percentage of patients with a static physician's global assessment of clear or minimal disease was 26%, 85%, 80%, and 69% with the 70-mg, 140-mg, 210-mg, and 280-mg doses, respectively, of brodalumab, as compared with 3% with placebo (P<0.01 for all comparisons with placebo). Two cases of grade 3 neutropenia were reported in the 210-mg brodalumab group. The most commonly reported adverse events in the combined brodalumab groups were nasopharyngitis (8%), upper respiratory tract infection (8%), and injection-site erythema (6%).

CONCLUSIONS

Brodalumab significantly improved plaque psoriasis in this 12-week, phase 2 study. (Funded by Amgen; ClinicalTrials.gov number, NCT00975637.).

IL-17 mediated inflammation promotes tumor growth and progression in the skin

The mechanism for inflammation associated tumor development is a central issue for tumor biology and immunology and remains to be fully elucidated. Although IL-17 is implicated in association with inflammation mediated carcinogenesis, mechanisms are largely elusive. In the current studies, we showed that IL-17 receptor-A gene deficient (IL-17R-/-) mice were resistant to chemical carcinogen-induced cutaneous carcinogenesis, a well-established inflammation associated tumor model in the skin. The deficiency in IL-17R increased the infiltration of CD8+ T cells whereas it inhibited the infiltration of CD11b+ myeloid cells and development of myeloid derived suppressor cells. Inflammation induced skin hyperplasia and production of pro-tumor inflammatory molecules were inhibited in IL-17R-/- mice. We found that pre-existing inflammation in the skin increased the susceptibility to tumor growth, which was associated with increased development of tumor specific IL-17 producing T cells. This inflammation induced susceptibility to tumor growth was abrogated in IL-17R-/- mice. Finally, neutralizing IL-17 in mice that had already developed chemical carcinogen induced skin tumors could inhibit inflammation mediated tumor progression at late stages. These results demonstrate that IL-17 mediated inflammation is an important mechanism for inflammation mediated promotion of tumor development. The study has major implications for targeting IL-17 in prevention and treatment of tumors.

Pivotal role of dermal IL-17-producing γδ T cells in skin inflammation

Interleukin-23 (IL-23) and CD4(+) T helper 17 (Th17) cells are thought to be critical in psoriasis pathogenesis. Here, we report that IL-23 predominantly stimulated dermal γδ T cells to produce IL-17 that led to disease progression. Dermal γδ T cells constitutively expressed the IL-23 receptor (IL-23R) and transcriptional factor RORγt. IL-17 production from dermal γδ T cells was independent of αβ T cells. The epidermal hyperplasia and inflammation induced by IL-23 were significantly decreased in T cell receptor δ-deficient (Tcrd(-/-)) and IL-17 receptor-deficient (Il17ra(-/-)) mice but occurred normally in Tcra(-/-) mice. Imiquimod-induced skin pathology was also significantly decreased in Tcrd(-/-) mice. Perhaps further promoting disease progression, IL-23 stimulated dermal γδ T cell expansion. In psoriasis patients, γδ T cells were greatly increased in affected skin and produced large amounts of IL-17. Thus, IL-23-responsive dermal γδ T cells are the major IL-17 producers in the skin and may represent a novel target for the treatment of psoriasis.

[Eukaryotic expression of human IL17-RD-ECD and generation of its monoclonal antibody]

IL-17 Receptor D (IL-17 RD) is a cytokine receptor that mediates IL-17 signaling and plays an important role in responding to the invasion of extracellular pathogens and many inflammatory and autoimmune diseases such as rheumatoid arthritis. In this study we report the generation of a mouse monoclonal antibody against human IL-17 RD. The recombinant human IL-17RD extracellular domain (hIL-17RD-ECD) was produced in the baculovirus expression system and purified from culture medium of sf9 insect cells. The purified protein was used as a T-dependent antigen to immune Balb/C mice. B cells from the spleen of immunized mice were fused with murine cell SP2/0. Hybridoma cell lines were screened for the production of the monoclonal antibody against hIL-17-RD-ECD using ELISA. A hybridoma cell line 1F8 was found to have a high production of the antibody, which was further confirmed for the specificity by both western blot and ELISA analyses. The monoclonal antibody obtained from hybridoma 1F8 was characterized to be IgG1+Kappa subclass. This study provided a base for the further therapeutic application of the antibody on the autoimmune disease including rheumatoid arthritis.

Upregulation of IL17RB during natural allergen exposure in patients with seasonal allergic rhinitis

BACKGROUND

Seasonal allergic rhinitis (SAR) to Japanese cedar (Cryptomeria japonica; JC) is an IgE-mediated type I allergy affecting the nasal mucosa. However, the molecular mechanisms that underlie SAR are only partially understood. The aim of the study was to identify novel genes related to SAR during natural exposure to pollens, by using microarray analysis.

METHODS

Subjects were 32 SAR patients and 25 controls. Total RNA was extracted from CD4(+) T cells isolated from peripheral blood mononuclear cells and subjected to microarray analysis with Illumina Human Ref8 BeadChip arrays. The Mann-Whitney test was performed to identify genes whose expression was altered during allergen exposure. Quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) was performed on samples collected from SAR patients and controls to verify the microarray results.

RESULTS

Microarray analysis showed that the expression of 3 genes was significantly altered during allergen exposure. Among these 3 genes, the expression of interleukin 17 receptor beta (IL17RB) was confirmed to be upregulated in SAR patients compared to that of the IL17RB gene in healthy, non-allergic controls. The average fold change of IL17RB expression in the real-time RT-PCR experiment was 3.9 (P = 0.003).

CONCLUSIONS

The present study identified upregulation of IL17RB during natural allergen exposure in patients with SAR, which may further elucidate the molecular mechanisms underlying SAR.

Interleukin 17 receptor in multiple sclerosis patients treated with interferon β-1a

Interleukin 17 (IL-17) and its receptor IL-17R1 produced by T-helper cells named Th17 are involved in the pathology of autoimmune diseases. In contrast to the at least partially explained role of IL-17 in pathology of multiple sclerosis, the significance of IL-17R in MS is unclear. Therefore we have studied the expression of IL-17R in the stable phase of multiple sclerosis treated by interferon β-1a. The studied material consisted of 20 MS patients with relapsing-remitting form of the disease, and fulfilling the diagnostic McDonald et al. criteria. The patients were treated subcutaneously every second day with 30 mg of interferon β -1a (Betaferon). The interleukin 17 receptor level was measured by the ELISA immunoassay test using RayBio human IL-17R ELISA kit. After three months of therapy with interferon β -1a the level of IL-17R was significantly higher than that established at the starting point. The level of IL-17R after 6 months of therapy was insignificantly higher than established in the previous study group (3 months of therapy). While it remains difficult to pinpoint the exact significance of upregulation of IL-17R in the early period of therapy, the present findings should be taken into account when considering the pharmacodynamics of interferon action in MS in view of the opinions on the crucial role of IL-17 in pathology of MS and suggestions that it may constitute a drug target in autoimmunological diseases.

Critical role of Th17 responses in a murine model of Neisseria gonorrhoeae genital infection

Host immune responses, including the characteristic influx of neutrophils, against Neisseria gonorrhoeae are poorly understood; adaptive immunity is minimal and non-protective. We hypothesize that N. gonorrhoeae selectively elicits Th17-dependent responses, which trigger innate defense mechanisms, including neutrophils and antimicrobial proteins, that it can resist. We found that N. gonorrhoeae induced the production of interleukin-17 (IL-17) in mouse T-cells and Th17-inducing cytokines in mouse and human APCs in vitro. IL-17 was induced in the iliac lymph nodes in vivo in a female mouse model of genital tract gonococcal infection. Antibody blockade of IL-17 or deletion of the major IL-17 receptor (IL-17R) in IL-17RA(KO) mice led to prolonged infection and diminished neutrophil influx. Genital tract tissue from IL-17RA(KO) mice showed reduced production of neutrophil-attractant chemokines in response to culture with N. gonorrhoeae. These results imply a crucial role for IL-17 and Th17 cells in the immune response to N. gonorrhoeae.

IL-17 promotes tumor development through the induction of tumor promoting microenvironments at tumor sites and myeloid-derived suppressor cells

The role of immune responses in tumor development is a central issue for tumor biology and immunology. IL-17 is an important cytokine for inflammatory and autoimmune diseases. Although IL-17-producing cells are detected in cancer patients and tumor-bearing mice, the role of IL-17 in tumor development is controversial, and mechanisms remain to be fully elucidated. In the current study, we found that the development of tumors was inhibited in IL-17R-deficient mice. A defect in IFN-gammaR increased tumor growth, whereas tumor growth was inhibited in mice that were deficient in both IL-17R and IFN-gammaR compared with wild-type animals. Further experiments showed that neutralization of IL-17 by Abs inhibited tumor growth in wild-type mice, whereas systemic administration of IL-17 promoted tumor growth. The IL-17R deficiency increased CD8 T cell infiltration, whereas it reduced the infiltration of myeloid-derived suppressor cells (MDSCs) in tumors. In contrast, administration of IL-17 inhibited CD8 T cell infiltration and increased MDSCs in tumors. Further analysis indicated that IL-17 was required for the development and tumor-promoting activity of MDSCs in tumor-bearing mice. These data demonstrate that IL-17-mediated responses promote tumor development through the induction of tumor-promoting microenvironments at tumor sites. IL-17-mediated regulation of MDSCs is a primary mechanism for its tumor-promoting effects. The study provides novel insights into the role of IL-17 in tumor development and has major implications for targeting IL-17 in treatment of tumors.

The IL-17 family cytokines in immunity and disease

INTRODUCTION

Accumulating evidence suggests that the interleukin (IL)-17 cytokines are major players in the immune response to foreign pathogens. In addition, the pathogeneses of a number of inflammatory diseases have been linked to uncontrolled expression of these cytokine pathways.

DISCUSSION

Genetic and biochemical analyses have elucidated the cellular and molecular events triggered by these proteins during an inflammatory response. While significant efforts have been placed on understanding the functions of IL-17A, IL-17F, and IL-17E, the significance of the other family members, IL-17B-D, in inflammation remains to be determined.

CONCLUSION

This review will focus on the cellular sources, target cell/receptors that are utilized by these cytokines to control pathogenesis, and the therapeutic potential of targeting these pathways to treat inflammatory disorders.

Interleukin-1 and IL-23 induce innate IL-17 production from gammadelta T cells, amplifying Th17 responses and autoimmunity

Th17 cells, CD4(+) T cells that secrete interleukin-17 (IL-17), are pathogenic in autoimmune diseases and their development and expansion is driven by the cytokines IL-6, TGF-beta, IL-21, IL-1, and IL-23. However, there are also innate sources of IL-17. Here, we show that gammadelta T cells express IL-23R and the transcription factor RORgammat and produce IL-17, IL-21, and IL-22 in response to IL-1beta and IL-23, without T cell receptor engagement. IL-17-producing gammadelta T cells were found at high frequency in the brain of mice with experimental autoimmune encephalomyelitis (EAE). gammadelta T cells activated by IL-1beta and IL-23 promoted IL-17 production by CD4(+) T cells and increased susceptibility to EAE, suggesting that gammadelta T cells act in an amplification loop for IL-17 production by Th17 cells. Our findings demonstrate that gammadelta T cells activated by IL-1beta and IL-23 are an important source of innate IL-17 and IL-21 and provide an alternative mechanism whereby IL-1 and IL-23 may mediate autoimmune inflammation.

Attenuated atherosclerosis upon IL-17R signaling disruption in LDLr deficient mice

Atherosclerosis is an inflammatory disease characterized by the influx of macrophages and T cells and IL-17 may connect innate and adaptive immune responses involved in atherogenesis. We investigated the role of IL-17 receptor signaling in atherosclerosis and transplanted LDLr deficient recipient mice with IL-17R deficient bone marrow. Induction of atherosclerosis by Western-type diet induced a 46% reduction in lesion size in the aortic root and the plaque composition revealed no significant changes in collagen content and neutrophil counts, but a reduction in mast cell number and an increase in macrophage number. In addition, we observed a decrease in anti-oxLDL antibodies of the IgG class upon IL-17R BMT, while introduction of IL-17R deficient bone marrow resulted in a reduced IL-6 production and an increased IL-10 production. In conclusion, signaling via the IL-17 receptor in bone marrow derived cells enhances the process of atherosclerosis.

Interleukin-17 and interferon-gamma are produced concomitantly by human coronary artery-infiltrating T cells and act synergistically on vascular smooth muscle cells

BACKGROUND

Atherosclerosis is an inflammatory disease in which interferon (IFN)-gamma, the signature cytokine of Th1 cells, plays a central role. We investigated whether interleukin (IL)-17, the signature cytokine of Th17 cells, is also associated with human coronary atherosclerosis.

METHODS AND RESULTS

Circulating IL-17 and IFN-gamma were detected in a subset of patients with coronary atherosclerosis and in referent outpatients of similar age without cardiac disease but not in young healthy individuals. IL-17 plasma levels correlated closely with those of the IL-12/IFN-gamma/CXCL10 cytokine axis but not with known Th17 inducers such as IL-1beta, IL-6, and IL-23. Both IL-17 and IFN-gamma were produced at higher levels by T cells within cultured atherosclerotic coronary arteries after polyclonal activation than within nondiseased vessels. Combinations of proinflammatory cytokines induced IFN-gamma but not IL-17 secretion. Blockade of IFN-gamma signaling increased IL-17 synthesis, whereas neutralization of IL-17 responses decreased IFN-gamma synthesis; production of both cytokines was inhibited by transforming growth factor-beta1. Approximately 10-fold fewer coronary artery-infiltrating T helper cells were IL-17 producers than IFN-gamma producers, and unexpectedly, IL-17/IFN-gamma double producers were readily detectable within the artery wall. Although IL-17 did not modulate the growth or survival of cultured vascular smooth muscle cells, IL-17 interacted cooperatively with IFN-gamma to enhance IL-6, CXCL8, and CXCL10 secretion.

CONCLUSIONS

Our findings demonstrate that IL-17 is produced concomitantly with IFN-gamma by coronary artery-infiltrating T cells and that these cytokines act synergistically to induce proinflammatory responses in vascular smooth muscle cells.