Protective immunity to systemic infection with attenuated Salmonella enterica serovar enteritidis in the absence of IL-12 is associated with IL-23-dependent IL-22, but not IL-17

IL-12 and IL-23 pathway inhibition in inflammatory bowel disease

Interleukin-12 (IL-12) and interleukin-23 (IL-23), which belong to the IL-12 family of cytokines, have a key role in intestinal homeostasis and inflammation and are implicated in the pathogenesis of inflammatory bowel disease. Upon their secretion by antigen-presenting cells, they exert both pro-inflammatory and anti-inflammatory receptor-mediated effects. An increased understanding of these biological effects, particularly the pro-inflammatory effects mediated by IL-12 and IL-23, has led to the development of monoclonal antibodies that target a subunit common to IL-12 and IL-23 (p40; targeted by ustekinumab and briakinumab), or the IL-23-specific subunit (p19; targeted by risankizumab, guselkumab, brazikumab and mirikizumab). This Review provides a summary of the biology of the IL-12 family cytokines IL-12 and IL-23, discusses the role of these cytokines in intestinal homeostasis and inflammation, and highlights IL-12- and IL-23-directed drug development for the treatment of Crohn's disease and ulcerative colitis.

Immunogenicity and protective efficacy of nanoparticle formulations of L-SseB against Salmonella infection

Salmonella enterica, a Gram-negative pathogen, has over 2500 serovars that infect a wide range of hosts. In humans, S. enterica causes typhoid or gastroenteritis and is a major public health concern. In this study, SseB (the tip protein of the Salmonella pathogenicity island 2 type III secretion system) was fused with the LTA1 subunit of labile-toxin from enterotoxigenic E. coli to make the self-adjuvanting antigen L-SseB. Two unique nanoparticle formulations were developed to allow multimeric presentation of L-SseB. Mice were vaccinated with these formulations and protective efficacy determined via challenging the mice with S. enterica serovars. The polysaccharide (chitosan) formulation was found to elicit better protection when compared to the squalene nanoemulsion. When the polysaccharide formulation was used to vaccinate rabbits, protection from S. enterica challenge was elicited. In summary, L-SseB in a particulate polysaccharide formulation appears to be an attractive candidate vaccine capable of broad protection against S. enterica.

BTNL2 promotes colitis-associated tumorigenesis in mice by regulating IL-22 production

Interleukin 22 (IL-22) has an important role in colorectal tumorigenesis and many colorectal diseases such as inflammatory bowel disease and certain infections. However, the regulation of IL-22 production in the intestinal system is still unclear. Here, we present evidence that butyrophilin-like protein 2 (BTNL2) is required for colorectal IL-22 production, and BTNL2 knockout mice show decreased colonic tumorigenesis and more severe colitis phenotypes than control mice due to defective production of IL-22. Mechanistically, BTNL2 acts on group 3 innate lymphoid cells (ILC3s), CD4+ T cells, and γδ T cells to promote the production of IL-22. Importantly, we find that a monoclonal antibody against BTNL2 attenuates colorectal tumorigenesis in mice and that the mBTNL2-Fc recombinant protein has a therapeutic effect in a dextran sulfate sodium (DSS)-induced colitis model. This study not only identifies a regulatory mechanism of IL-22 production in the colorectal system but also provides a potential therapeutic target for the treatment of human colorectal cancer and inflammatory bowel diseases.

Elevated IL-6 and IL-22 in Early Pregnancy Are Associated with Worse Disease Course in Women with Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD), including Ulcerative Colitis (UC) and Crohn’s disease (CD), are inflammatory conditions of the intestinal tract that affect women in their reproductive years. Pregnancy affects Th1- and Th2-cytokines, but how these changes occur during pregnancy in IBD is unclear. We performed a longitudinal profiling of serum cytokines in a cohort of 11 healthy pregnant women and 76 pregnant women with IBD from the first trimester of pregnancy to the first 12 months post-partum. Participants were monitored for biochemical disease activity (C-reactive protein [CRP] and fecal calprotectin [FCP]) and clinical activities. Maternal cytokines were measured using ELISA. We identified changes in Th1 and Th17 cytokines throughout pregnancy in healthy pregnant women. During pregnancy, maternal serum cytokine expressions were influenced by IBD, disease activity, and medications. Active UC was associated with an elevation in IL-21, whereas active CD was associated with elevated IFN-γ, IL-6, and IL-21. Interestingly, T1 serum cytokine levels of IL-22 (>0.624 pg/mL) and IL-6 (>0.648 pg/mL) were associated with worse IBD disease activity throughout pregnancy in women with UC and CD, respectively. This shows serum cytokines in pregnancy differ by IBD, disease activity, and medications. We show for the first time that T1 IL-22 and IL-6 correlate with IBD disease course throughout pregnancy.

Aryl Hydrocarbon Receptor Activation by Benzo[a]pyrene Prevents Development of Septic Shock and Fatal Outcome in a Mouse Model of Systemic Salmonella enterica Infection

This study focused on immunomodulatory effects of aryl hydrocarbon receptor (AhR) activation through benzo[a]pyrene (BaP) during systemic bacterial infection. Using a well-established mouse model of systemic Salmonella enterica (S.E.) infection, we studied the influence of BaP on the cellular and humoral immune response and the outcome of disease. BaP exposure significantly reduced mortality, which is mainly caused by septic shock. Surprisingly, the bacterial burden in BaP-exposed surviving mice was significantly higher compared to non-exposed mice. During the early phase of infection (days 1-3 post-infection (p.i.)), the transcription of proinflammatory factors (i.e., IL-12, IFN-γ, TNF-α, IL-1β, IL-6, IL-18) was induced faster under BaP exposure. Moreover, BaP supported the activity of antigen-presenting cells (i.e., CD64 (FcγRI), MHC II, NO radicals, phagocytosis) at the site of infection. However, early in infection, the anti-inflammatory cytokines IL-10 and IL-22 were also locally and systemically upregulated in BaP-exposed S.E.-infected mice. BaP-exposure resulted in long-term persistence of salmonellae up to day 90 p.i., which was accompanied by significantly elevated S.E.-specific antibody responses (i.e., IgG1, IgG2c). In summary, these data suggest that BaP-induced AhR activation is capable of preventing a fatal outcome of systemic S.E. infection, but may result in long-term bacterial persistence, which, in turn, may support the development of chronic inflammation.

ROLE OF MACROPHAGE MIGRATION INHIBITORY FACTOR, CLUSTER OF DIFFERENTIATION 19 AND INTERLEUKIN 23 IN INDIVIDUALS INFECTED WITH Salmonella typhi

Salmonella enterica serovar typhi (S.typhi) is one of the most important gram negative bacteria that cause enteric fever and stimulate the immune response in infected patients. This study aimed to compare the humoral and cellular immune responses in patients infected with S.typhi. For this, the concentration of three immunological markers viz., Macrophage migration inhibitory factor (MIF), Cluster of Differentiation 19 (CD19), and Interleukin 23 (IL-23) were measured by the Enzyme-Linked Immunosorbent Assay in the serum of 54 S.typhi infected patients, and 31 healthy individuals. The results demonstrated a significant increase (P =<0.05) in the serum concentration of MIF in patients infected with acute infection of S. typhi compared with healthy individuals but there were no significant differences in chronic infection. While there was a significant increase (P =<0.05) in serum concentration of CD19 and IL-23 in patients infected with acute and chronic infection of S.typhi as compared with healthy individuals. In conclusion, macrophage migration inhibitory factor plays a vital role in patients infected with acute infection of S. typhi and has no synergism with T-cell and B-cell in acute and chronic infection.

Reprogramming Intestinal Epithelial Cell Polarity by Interleukin-22

Background: Interleukin-22 (IL-22) impacts the integrity of intestinal epithelia and has been associated with the development of colitis-associated cancer and inflammatory bowel diseases (IBD). Previous data suggest that IL-22 protects the mucosal barrier and promotes wound healing and barrier defect. We hypothesized, that IL-22 modulates cell polarity of intestinal epithelial cells (IECs) acting on tight junction assembly. The aim of the study was to investigate IL-22-dependent mechanisms in the reprogramming of intestinal epithelia.

Methods: IECs were exposed to IL-22 at various concentrations. IECs in Matrigel® were grown to 3-dimensional cysts in the presence or absence of IL-22 and morphology and expression of polarity proteins were analyzed by confocal microscopy. Epithelial cell barrier (TER and sandwich assay) and TJ assembly analysis (calcium-switch assay) were performed. TJ and cell polarity protein expression were assessed by western blotting and confocal microscopy. Cell migration and invasion assays were performed. Induction of epithelial-mesenchymal transition (EMT) was assessed by RT-qPCR analysis and western blotting. Signaling pathway analyses were performed by phosphoblotting and functional assays after blocking STAT3 and ERK signaling pathways. Using the toxoplasma-model of terminal ileitis, IL-22-knock-out mice were compared to wild-type littermates, analyzed for barrier function using one-path-impedance-analysis and macromolecular flux (H3-mannitol, Ussing-chambers).

Results: IECs exhibited a barrier defect after IL-22 exposure. TJ protein distribution and expression were severely impaired. Delayed recovery in the calcium-switch assay was observed suggesting a defect in TJ assembly. Analyzing the 3D-cyst model, IL-22 induced multi-lumen and aberrant cysts, and altered the localization of cell polarity proteins. Cell migration and invasion was caused by IL-22 as well as induction of EMT. Interestingly, only inhibition of the MAPK pathway, rescued the TJal barrier defect, while blocking STAT3 was relevant for cell survival. In addition, ileal mucosa of IL-22 deficient mice was protected from the barrier defect seen in Toxoplasma gondii-induced ileitis in wild type mice shown by significantly higher Re values and correspondingly lower macromolecule fluxes.

Conclusion: IL-22 impairs intestinal epithelial cell barrier by inducing EMT, causing defects in epithelial cell polarity and increasing cell motility and cell invasion. IL-22 modulates TJ protein expression and mediates tight junctional (TJal) barrier defects via ERK pathway.

A Double Edged Sword Role of Interleukin-22 in Wound Healing and Tissue Regeneration

Wound healing and tissue regeneration is an intricate biological process that involves repair of cellular damage and maintenance of tissue integrity. Cascades involved in wound healing and tissue regeneration highly overlap with cancer causing pathways. Usually, subsequent tissue damage events include release of a number of cytokines to accomplish post-trauma restoration. IL-22 is one of the cytokines that are immediately produced to initiate immune response against several tissue impairments. IL-22 is a fundamental mediator in inflammation, mucous production, protective role against pathogens, wound healing, and tissue regeneration. However, accumulating evidence suggests pivotal role of IL-22 in instigation of various cancers due to its pro-inflammatory and tissue repairing activity. In this review, we summarize how healing effects of IL-22, when executed in an uncontrollable fashion can lead to carcinogenesis.

Considerations for safety in the use of systemic medications for psoriasis and atopic dermatitis during the COVID-19 pandemic

Coronavirus disease 2019 (COVID‐19) is responsible for at least 2 546 527 cases and 175 812 deaths as of April 21, 2020. Psoriasis and atopic dermatitis (AD) are common, chronic, inflammatory skin conditions, with immune dysregulation as a shared mechanism; therefore, mainstays of treatment include systemic immunomodulating therapies. It is unknown whether these therapies are associated with increased COVID‐19 susceptibility or worse outcomes in infected patients. In this review, we discuss overall infection risks of nonbiologic and biologic systemic medications for psoriasis and AD and provide therapeutic recommendations. In summary, in patients with active infection, systemic conventional medications, the Janus kinase inhibitor tofacitinib, and biologics for psoriasis should be temporarily held until there is more data; in uninfected patients switching to safer alternatives should be considered. Interleukin (IL)‐17, IL‐12/23, and IL‐23 inhibitors are associated with low infection risk, with IL‐17 and IL‐23 favored over IL‐12/23 inhibitors. Pivotal trials and postmarketing data also suggest that IL‐17 and IL‐23 blockers are safer than tumor necrosis factor alpha blockers. Apremilast, acitretin, and dupilumab have favorable safety data and may be safely initiated and continued in uninfected patients. Without definitive COVID‐19 data, these recommendations may be useful in guiding treatment of psoriasis and AD patients during the COVID‐19 pandemic.

IL23 Promotes Antimicrobial Pathways in Human Macrophages, Which Are Reduced With the IBD-Protective IL23R R381Q Variant

BACKGROUND & AIMS

Interleukin (IL)23 is a major contributor to inflammatory bowel disease (IBD) pathogenesis and is being pursued as a therapeutic target, both through targeting IL23 alone or in combination with IL12. Unexpected trial outcomes highlight the importance of understanding the cell types through which IL23 regulates immune responses, and how IL23 and IL12 compare in these responses. Macrophages are key players in IBD, and IL23 recently was found to promote inflammatory outcomes in human macrophages. This raises the possibility that IL23 may be required for additional essential macrophage functions, in particular microbial clearance, such that either blocking the IL23 pathway or the IL23R-R381Q IBD-protective variant may reduce macrophage-mediated microbial clearance.

METHODS

We analyzed protein expression, signaling, bacterial uptake, and intracellular bacterial clearance in human monocyte-derived macrophages through Western blot, flow cytometry, and gentamicin protection.

RESULTS

Autocrine/paracrine IL23 was critical for optimal levels of pattern-recognition-receptor (PRR)-induced intracellular bacterial clearance in human macrophages. Mechanisms regulated by IL23 included induction of pyruvate dehydrogenase kinase 1-dependent bacterial uptake, and up-regulation of reactive oxygen species through nicotinamide adenine dinucleotide phosphate oxidase members, nitric oxide synthase 2, and autophagy through ATG5 and ATG16L1. Complementing these pathways in IL23R-deficient macrophages restored PRR-induced bacterial uptake and clearance. Janus kinase 2, TYK2, and STAT3 were required for IL23-induced mechanisms. IL23 and IL12 induced antimicrobial pathways to similar levels in human macrophages. Relative to IL23R-R381, transfected IL23R-Q381, or monocyte-derived macrophages from IL23R-Q381 carriers showed reduced bacterial uptake and clearance.

CONCLUSIONS

We identify that autocrine/paracrine IL23 is required for optimal PRR-enhanced macrophage bacterial uptake and intracellular bacterial clearance, define mechanisms regulating IL23R-induced bacterial clearance, and determine how the IBD-protective IL23R-R381Q variant modulates these processes.

Nonclinical safety of tildrakizumab, a humanized anti-IL-23p19 monoclonal antibody, in nonhuman primates

Tildrakizumab (also known as MK-3222), is a high-affinity, humanized, immunoglobin G1κ monoclonal antibody targeting the p19 subunit of interleukin-23 recently approved for the treatment of moderate to severe plaque psoriasis in the US, Europe, and Australia. The safety profile of tildrakizumab was characterized in nonclinical studies using a pharmacologically relevant cynomolgus monkey model. In repeat-dose toxicity studies, cynomolgus monkeys were chronically treated with subcutaneous (SC) injections of 100 mg/kg of tildrakizumab every 2 weeks up to 9 months. Tildrakizumab was well tolerated, with no toxicological findings (including assessment of reproductive organs; hormonal effects; and cardiovascular, respiratory, and central nervous system function) at systemic exposures approximately 90 times higher than the recommended human dose of 100 mg. An embryofetal developmental study conducted in pregnant monkeys revealed no treatment-related effects to the developing fetus following SC administration of tildrakizumab 100 mg/kg. In a pre- and postnatal development study, 2 neonatal deaths due to potential viral infection at 100 mg/kg were considered of uncertain relationship to the treatment based on a lack of historical data on the occurrence of viral infection in neonate cynomolgus monkeys. The results of this comprehensive nonclinical safety program support the safe use of tildrakizumab.

Intracellular Pathogens: Host Immunity and Microbial Persistence Strategies

Infectious diseases caused by pathogens including viruses, bacteria, fungi, and parasites are ranked as the second leading cause of death worldwide by the World Health Organization. Despite tremendous improvements in global public health since 1950, a number of challenges remain to either prevent or eradicate infectious diseases. Many pathogens can cause acute infections that are effectively cleared by the host immunity, but a subcategory of these pathogens called "intracellular pathogens" can establish persistent and sometimes lifelong infections. Several of these intracellular pathogens manage to evade the host immune monitoring and cause disease by replicating inside the host cells. These pathogens have evolved diverse immune escape strategies and overcome immune responses by residing and multiplying inside host immune cells, primarily macrophages. While these intracellular pathogens that cause persistent infections are phylogenetically diverse and engage in diverse immune evasion and persistence strategies, they share common pathogen type-specific mechanisms during host-pathogen interaction inside host cells. Likewise, the host immune system is also equipped with a diverse range of effector functions to fight against the establishment of pathogen persistence and subsequent host damage. This article provides an overview of the immune effector functions used by the host to counter pathogens and various persistence strategies used by intracellular pathogens to counter host immunity, which enables their extended period of colonization in the host. The improved understanding of persistent intracellular pathogen-derived infections will contribute to develop improved disease diagnostics, therapeutics, and prophylactics.

CNBP controls IL-12 gene transcription and Th1 immunity

These studies reveal a previously unrecognized role for Cnbp as a novel transcriptional regulator engaged downstream of innate immune receptors controlling the c-Rel–IL-12–Th1 axis, which has important implications for both host defense and inflammatory disease.

An inducible program of inflammatory gene expression is a hallmark of antimicrobial defenses. Recently, cellular nucleic acid–binding protein (CNBP) was identified as a regulator of nuclear factor-kappaB (NF-κB)–dependent proinflammatory cytokine gene expression. Here, we generated mice lacking CNBP and found that CNBP regulates a very restricted gene signature that includes IL-12β. CNBP resides in the cytosol of macrophages and translocates to the nucleus in response to diverse microbial pathogens and pathogen-derived products. Cnbp-deficient macrophages induced canonical NF-κB/Rel signaling normally but were impaired in their ability to control the activation of c-Rel, a key driver of IL-12β gene transcription. The nuclear translocation and DNA-binding activity of c-Rel required CNBP. Lastly, Cnbp-deficient mice were more susceptible to acute toxoplasmosis associated with reduced production of IL-12β, as well as a reduced T helper type 1 (Th1) cell IFN-γ response essential to controlling parasite replication. Collectively, these findings identify CNBP as important regulator of c-Rel–dependent IL-12β gene transcription and Th1 immunity.

Th17 cytokine profiling of colorectal cancer patients with or without enterovirus 71 antigen expression

OBJECT

Th17 cytokines have been identified in several types of human cancers. In this pilot study, the expression of Th17 cytokines profiling in enteroviruses 71 (EV71) associated colorectal cancer (CRC) were explored.

METHODS

66 patients with CRC were enrolled in this study; immune- histochemical analyses were performed on cancerous tissues and adjacent non- cancerous tissues of the patients. Serum Th17 cytokines of CRC patients and healthy controls were measured using a Luminex 200 analyzer.

RESULTS

Cancerous tissues had more positive EV71 antigen expression than adjacent non- cancerous tissues. In TNM II-III CRC, 59.9% of cancerous tissues were observed to be EV71 positive; on the contrary, 65.2% of the adjacent non- cancerous epithelium was EV71 negative. In TNM I CRC, all adjacent non- cancerous epithelium was virus negative, but in TNM IV, half of adjacent non- cancerous tissues were virus positive. Serum IL-10 were significantly higher in CRC patients than in healthy controls, and IL-10 concentrations in the EV71 positive group were higher than those of the EV71 negative group, with the highest IL-10 levels being observed in CRC patients with strong positive group (P < 0.05). Similar results were found for IL-21 and IL-23. IL-17 levels were higher in CRC patients than in healthy controls, there was no significant difference in IL-17 between the viral positive and viral negative groups (P > 0.05).

CONCLUSION

Persistent existing EV71 viral antigens in intestinal tissues are positively associated with TNM III/IV CRC. EV71 latent infection recruits Th17 cells in the colorectal tumor site, stimulating Th17 cytokine production that closely associated with CRC carcinogenesis.

Clinical importance of IL-22 cascade in IBD

IL-22 is a relatively new cytokine that is characterized by several unique biological properties. In the intestines, the effect of IL-22 is restricted mainly to non-lymphoid cells such as epithelial cells. Interestingly, the expression pattern and major cellular source of IL-22 have distinct difference between large and small intestines. IL-22 possesses an ability to constitutively activate STAT3 for promoting epithelial cell regeneration and reinforcing mucosal barrier integrity through stimulating the expression of anti-bacterial peptide and mucins. Of note, IL-22 is characterized as a two-faced cytokine that can play not only protective but also deleterious roles in the intestinal inflammation depending on the cytokine environment such as the expression levels of IL-23, T-bet, and IL-22 binding protein. Most importantly, clinical relevance of IL-22 to inflammatory bowel disease has been well highlighted. Mucosal healing, which represents the current therapeutic goal for IBD, can be induced by IL-22. Indeed, indigo naturalis, which can activate IL-22 pathway through Ahr, has been shown in a clinical trial to exhibit a strong therapeutic effect on ulcerative colitis. Despite the beneficial effect of IL-22, continuous activation of the IL-22 pathway increases the risk of colitis-associated cancer, particularly in patients with an extended history of IBD. This review article discusses how IL-22 regulates colitis, how beneficial versus deleterious effects of IL-22 is determined, and why IL-22 represents a promising target for IBD therapy.

The Immunoregulation of Th17 in Host against Intracellular Bacterial Infection

T helper 17 cells (Th17) constitute a distinct subset of helper T cells with a unique transcriptional profile (STAT3, RORγ, and RORα), cytokine production pattern (IL17 family), and requirement of specific cytokines for their differentiation (TGF-β, IL6, IL21, and IL23). Recent studies involving experimental animals and humans have shown that Th17/IL17 plays a crucial role in host defense against a variety of pathogens, including bacteria and viruses. The underlying mechanisms by which Th17 performs include dendritic cell (DC) regulation, neutrophil recruitment, Th1 modulation, and T regulatory cell (Treg) balance. In recent years, researchers have generated an accumulating wealth of evidence on the role of Th17/IL17 in protective immunity to intracellular bacterial pathogens, such as Mycobacterium tuberculosis and Chlamydia trachomatis, which are one of the most important pathogens that inflict significant socioeconomic burden across the globe. In this article, we reviewed the current literature on the functions and mechanisms by which Th17/IL17 responds to intracellular bacterial infections. A better understanding of Th17/IL17 immunity to pathogens would be crucial for developing effective prophylactics and therapeutics.

Interleukin-22 in human inflammatory diseases and viral infections

Interleukin-22 (IL22) is one of the members of IL10 family. Elevated levels of this cytokine can be seen in diseases caused by T lymphocytes, such as Psoriasis, Rheumatoid arthritis, interstitial lung diseases. IL22 is produced by different cells in both innate and acquired immunities. Different types of T cells are able to produce IL22, but the major IL22-producing T-cell is the TCD4. TH22 cell is a new line of TCD4 cells, which differentiated from naive T cells in the presence of TNFα and IL6; 50% of peripheral blood IL22 is produced by these cells. IL22 has important functions in host defense at mucosal surfaces as well as in tissue repair. In this review, we assess the current understanding of this cytokine and focus on the possible roles of IL-22 in autoimmune diseases.

Salmonella infection: Interplay between the bacteria and host immune system

Salmonella infection causes morbidity and mortality throughout the world with the host immune response varying depending on whether the infection is acute and limited, or systemic and chronic. Additionally, Salmonella bacteria have evolved multiple mechanisms to avoid or subvert immunity to its own benefit and often the anatomical location of infection plays a role in both the immune response and bacterial fate. Here, we provide an overview of the interplay between the immune system and Salmonella, while discussing how different host and bacterial factors influence the outcome of infection.

Genetic and Dietary Iron Overload Differentially Affect the Course of Salmonella Typhimurium Infection

Genetic and dietary forms of iron overload have distinctive clinical and pathophysiological features. HFE-associated hereditary hemochromatosis is characterized by overwhelming intestinal iron absorption, parenchymal iron deposition, and macrophage iron depletion. In contrast, excessive dietary iron intake results in iron deposition in macrophages. However, the functional consequences of genetic and dietary iron overload for the control of microbes are incompletely understood. Using Hfe^+/+ and Hfe^-/- mice in combination with oral iron overload in a model of Salmonella enterica serovar Typhimurium infection, we found animals of either genotype to induce hepcidin antimicrobial peptide expression and hypoferremia following systemic infection in an Hfe-independent manner. As predicted, Hfe^-/- mice, a model of hereditary hemochromatosis, displayed reduced spleen iron content, which translated into improved control of Salmonella replication. Salmonella adapted to the iron-poor microenvironment in the spleens of Hfe^-/- mice by inducing the expression of its siderophore iron-uptake machinery. Dietary iron loading resulted in higher bacterial numbers in both WT and Hfe^-/- mice, although Hfe deficiency still resulted in better pathogen control and improved survival. This suggests that Hfe deficiency may exert protective effects in addition to the control of iron availability for intracellular bacteria. Our data show that a dynamic adaptation of iron metabolism in both immune cells and microbes shapes the host-pathogen interaction in the setting of systemic Salmonella infection. Moreover, Hfe-associated iron overload and dietary iron excess result in different outcomes in infection, indicating that tissue and cellular iron distribution determines the susceptibility to infection with specific pathogens.

Tildrakizumab for treating psoriasis

INTRODUCTION

Agents that block inflammatory pathways other than tumor necrosis factor (TNF) have represented new options for treating psoriasis in recent years. IL-23 is involved in regulating Th17 cells and is a potent activator of keratinocyte proliferation. Targeting IL-23p19 alone may be a promising treatment approach in patients with moderate-to-severe chronic plaque psoriasis, with a downregulation of Th17 and Th22 cell responses, while IL-12 blockade is not required to achieve efficacy in these patients. Areas covered: The authors review and provide an update on tildrakizumab, a humanized IgG1 monoclonal antibody that blocks the p19 subunit of IL-23. Expert opinion: Total skin clearance is an important treatment goal that has both measurable and clinically meaningful benefits. Meeting patient needs about total clearance, IL-23p19 inhibitors will obtain a specific position in the crowded psoriasis market. On the other hand, PASI 75 and PASI 90 response achieved by tildrakizumab in the phase II and III trials are less than the response achieved by the IL-17A inhibitors and other p19 competitors, possibly due to a less intensive dosing regimen, although direct comparisons cannot be made without a head-to-head randomized clinical trial. The main advantage of tildrakizumab is that it is dosed in a maintenance regimen of 12 weeks, and similar to ustekinumab, this is likely to encourage adherence and aid persistence to the drug.

Enhanced effect of BCG vaccine against pulmonary Mycobacterium tuberculosis infection in mice with lung Th17 response to mycobacterial heparin-binding hemagglutinin adhesin antigen

Although the BCG vaccine can prevent tuberculosis (TB) in infants, its ability to prevent adult pulmonary TB is reportedly limited. Therefore, development of a novel effective vaccine against pulmonary TB has become an international research priority. We have previously reported that intranasal vaccination of mice with a mycobacterial heparin-binding hemagglutinin adhesin (HBHA) plus mucosal adjuvant cholera toxin (CT) enhances production of IFN-γ and anti-HBHA antibody and suppresses extrapulmonary bacterial dissemination after intranasal infection with BCG. In the present study, the effects of intranasal HBHA + CT vaccine on murine pulmonary Mycobacterium tuberculosis (Mtb) infection were examined. Intranasal HBHA + CT vaccination alone failed to reduce the bacterial burden in the infected lung. However, a combination vaccine consisting of s.c. BCG priming and an intranasal HBHA + CT booster significantly enhanced protective immunity against pulmonary Mtb infection on day 14 compared with BCG vaccine alone. Further, it was found that intranasal HBHA + CT vaccine enhanced not only IFN-γ but also IL-17A production by HBHA-specific T cells in the lung after pulmonary Mtb infection. Therefore, this combination vaccine may be a good candidate for a new vaccine strategy against pulmonary TB.

AAV-IL-22 modifies liver chemokine activity and ameliorates portal inflammation in murine autoimmune cholangitis

There remain significant obstacles in developing biologics to treat primary biliary cholangitis (PBC). Although a number of agents have been studied both in murine models and human patients, the results have been relatively disappointing. IL-22 is a member of the IL-10 family and has multiple theoretical reasons for predicting successful usage in PBC. We have taken advantage of an IL-22 expressing adeno-associated virus (AAV-IL-22) to address the potential role of IL-22 in not only protecting mice from autoimmune cholangitis, but also in treating animals with established portal inflammation. Using our established mouse model of 2-OA-OVA immunization, including α-galactosylceramide (α-GalCer) stimulation, we treated mice both before and after the onset of clinical disease with AAV-IL-22. Firstly, AAV-IL-22 treatment given prior to 2-OA-OVA and α-GalCer exposure, i.e. before the onset of disease, significantly reduces the portal inflammatory response, production of Th1 cytokines and appearance of liver fibrosis. It also reduced the liver lymphotropic chemokines CCL5, CCL19, CXCL9, and CXCL10. Secondly, and more importantly, therapeutic use of AAV-IL-22, administered after the onset of disease, achieved a greater hurdle and significantly improved portal pathology. Further the improvements in inflammation were negatively correlated with levels of CCL5 and CXCL10 and positively correlated with levels of IL-22. In conclusion, we submit that the clinical use of IL-22 has a potential role in modulating the inflammatory portal process in patients with PBC.

IL-17A-Producing γδ T Cells Suppress Early Control of Parasite Growth by Monocytes in the Liver

Intracellular infections, such as those caused by the protozoan parasite Leishmania donovani, a causative agent of visceral leishmaniasis (VL), require a potent host proinflammatory response for control. IL-17 has emerged as an important proinflammatory cytokine required for limiting growth of both extracellular and intracellular pathogens. However, there are conflicting reports on the exact roles for IL-17 during parasitic infections and limited knowledge about cellular sources and the immune pathways it modulates. We examined the role of IL-17 in an experimental model of VL caused by infection of C57BL/6 mice with L. donovani and identified an early suppressive role for IL-17 in the liver that limited control of parasite growth. IL-17-producing γδ T cells recruited to the liver in the first week of infection were the critical source of IL-17 in this model, and CCR2(+) inflammatory monocytes were an important target for the suppressive effects of IL-17. Improved parasite control was independent of NO generation, but associated with maintenance of superoxide dismutase mRNA expression in the absence of IL-17 in the liver. Thus, we have identified a novel inhibitory function for IL-17 in parasitic infection, and our results demonstrate important interactions among γδ T cells, monocytes, and infected macrophages in the liver that can determine the outcome of parasitic infection.

Tildrakizumab (MK-3222), an anti-interleukin-23p19 monoclonal antibody, improves psoriasis in a phase IIb randomized placebo-controlled trial

BACKGROUND

Tildrakizumab is a high-affinity, humanized, IgG1/κ, anti-interleukin (IL)-23p19 monoclonal antibody that does not bind human IL-12 or p40 is being developed for the treatment of chronic plaque psoriasis.

OBJECTIVES

To evaluate the safety and efficacy of subcutaneous tildrakizumab in patients with moderate-to-severe chronic plaque psoriasis.

METHODS

A three-part, randomized, double-blind, phase IIb trial was conducted in 355 adults with chronic plaque psoriasis. Participants were randomized to receive subcutaneous tildrakizumab (5, 25, 100, 200 mg) or placebo at weeks 0 and 4 (part I) and every 12 weeks thereafter until week 52 (part II). Study drug was discontinued at week 52 and participants were followed through week 72 (part III). Primary efficacy end point was Psoriasis Area and Severity Index (PASI) 75 response at week 16. Adverse events (AEs) and vital signs were monitored throughout the study.

RESULTS

At week 16, PASI 75 responses were 33·3% (n = 14), 64·4% (n = 58), 66·3% (n = 59), 74·4% (n = 64) and 4·4% (n = 2) in the 5-, 25-, 100- and 200-mg tildrakizumab and placebo groups, respectively (P ≤ 0·001 for each tildrakizumab dose vs. placebo). PASI 75 response was generally maintained through week 52; only eight of 222 participants who achieved PASI 75 response at week 52 and continued to part III relapsed following discontinuation up to week 72. Possible drug-related serious AEs included bacterial arthritis and lymphoedema (part I), and melanoma, stroke, epiglottitis and knee infection (part II).

CONCLUSIONS

Tildrakizumab had treatment effects that were superior to placebo, maintained for 52 weeks of treatment, and persisted for 20 weeks after cessation. Tildrakizumab was generally safe and well tolerated. These results suggest that IL-23p19 is a key target for suppressing psoriasis.

IL-12 and IL-23 cytokines: from discovery to targeted therapies for immune-mediated inflammatory diseases

The cytokine interleukin-12 (IL-12) was thought to have a central role in T cell-mediated responses in inflammation for more than a decade after it was first identified. Discovery of the cytokine IL-23, which shares a common p40 subunit with IL-12, prompted efforts to clarify the relative contribution of these two cytokines in immune regulation. Ustekinumab, a therapeutic agent targeting both cytokines, was recently approved to treat psoriasis and psoriatic arthritis, and related agents are in clinical testing for a variety of inflammatory disorders. Here we discuss the therapeutic rationale for targeting these cytokines, the unintended consequences for host defense and tumor surveillance and potential ways in which these therapies can be applied to treat additional immune disorders.

The Human IL-22 Receptor Is Regulated through the Action of the Novel E3 Ligase Subunit FBXW12, Which Functions as an Epithelial Growth Suppressor

Interleukin- (IL-) 22 signaling is protective in animal models of pneumonia and bacteremia by Klebsiella pneumoniae and mediates tissue recovery from influenza and Staph aureus infection. We recently described processing of mouse lung epithelial IL-22 receptor (IL-22R) by ubiquitination on the intracellular C-terminal. To identify cellular factors that regulate human IL-22R, we screened receptor abundance while overexpressing constituents of the ubiquitin system and identify that IL-22R can be shuttled for degradation by multiple previously uncharacterized F-box protein E3 ligase subunits. We observe that in human cells IL-22R is destabilized by FBXW12. FBXW12 causes depletion of endogenous and plasmid-derived IL-22R in lung epithelia, binds the E3 ligase constituent Skp-1, and facilitates ubiquitination of IL-22R in vitro. FBXW12 knockdown with shRNA increases IL-22R abundance and STAT3 phosphorylation in response to IL-22 cytokine treatment. FBXW12 shRNA increases human epithelial cell growth and cell cycle progression with enhanced constitutive activity of map kinases JNK and ERK. These findings indicate that the heretofore-undescribed protein FBXW12 functions as an E3 ligase constituent to ubiquitinate and degrade IL-22R and that therapeutic FBXW12 inhibition may enhance IL-22 signaling and bolster mucosal host defense and infection containment.

Interleukin-22: immunobiology and pathology

Interleukin-22 (IL-22) is a recently described IL-10 family cytokine that is produced by T helper (Th) 17 cells, γδ T cells, NKT cells, and newly described innate lymphoid cells (ILCs). Knowledge of IL-22 biology has evolved rapidly since its discovery in 2000, and a role for IL-22 has been identified in numerous tissues, including the intestines, lung, liver, kidney, thymus, pancreas, and skin. IL-22 primarily targets nonhematopoietic epithelial and stromal cells, where it can promote proliferation and play a role in tissue regeneration. In addition, IL-22 regulates host defense at barrier surfaces. However, IL-22 has also been linked to several conditions involving inflammatory tissue pathology. In this review, we assess the current understanding of this cytokine, including its physiologic and pathologic effects on epithelial cell function.

Th17 differentiation and their pro-inflammation function

CD4(+) T helper cells are classical but constantly reinterpreted T-cell subset, playing critical roles in a diverse range of inflammatory responses or diseases. Depending on the cytokines they release and the immune responses they mediate, CD4(+) T cells are classically divided into two major cell populations: Th1 and Th2 cells. However, recent studies challenged this Th1/Th2 paradigm by discovering several T-helper cell subsets with specific differentiation program and functions, including Th17 cells, Treg cells, and Tfh cells. In this chapter, we summarize the current understanding and recent progresses on the Th17 lineage differentiation and its effector impacts on variety of inflammatory responses or disease pathogenesis.

The Jekyll and Hyde story of IL17-Producing γδT Cells

In comparison to conventional αβT cells, γδT cells are considered as specialized T cells based on their contributions in regulating immune response. γδT cells sense early environmental signals and initiate local immune-surveillance. The development of functional subtypes of γδT cells takes place in the thymus but they also exhibit plasticity in response to the activating signals and cytokines encountered in the extrathymic region. Thymic development of Tγδ1 requires strong TCR, CD27, and Skint-1 signals. However, differentiation of IL17-producing γδT cells (Tγδ17) is independent of Skint-1 or CD27 but requires notch signaling along with IL6 and TGFβ cytokines in the presence of weak TCR signal. In response to cytokines like IL23, IL6, and IL1β, Tγδ17 outshine Th17 cells for early activation and IL17 secretion. Despite expressing similar repertoire of lineage transcriptional factors, cytokines, and chemokine receptors, Tγδ17 cells differ from Th17 in spatial and temporal fashion. There are compelling reasons to consider significant role of Tγδ17 cells in regulating inflammation and thereby disease outcome. Tγδ17 cells regulate mobilization of innate immune cells and induce keratinocytes to secrete anti-microbial peptides thus exhibiting protective functions in anti-microbial immunity. In contrast, dysregulated Tγδ17 cells inhibit Treg cells, exacerbate autoimmunity, and are also known to support carcinogenesis by enhancing angiogenesis. The mechanism associated with this dual behavior of Tγδ17 is not clear. To exploit, Tγδ17 cells for beneficial use requires comprehensive analysis of their biology. Here, we summarize the current understanding on the characteristics, development, and functions of Tγδ17 cells in various pathological scenarios.

High suppressor of cytokine signaling-3 expression impairs STAT3-dependent protective effects of interleukin-22 in ulcerative colitis in remission

BACKGROUND

High SOCS3 expression in intestinal epithelial cells (IECs) of patients with ulcerative colitis (UC) in remission reflects the shorter time to relapse. We investigated whether high SOCS3 increased risk for relapse through violating STAT3-dependent protective effects of interleukin (IL)-22 during UC remission.

METHODS

Expression of IL-22 and c-Myc in UC remission mucosa was analyzed by immunohistochemistry. Effects of IL-22 on migration and proliferation of IEC cell lines with enforced SOCS3 expression were assessed with wounding assay and CCK-8 assay, respectively. Influence of STAT3 interference and SOCS3 overexpression on IL-22-regulated expression of antimicrobial peptide and proliferation-related molecules, including DMBT1, c-Myc, Survivin, Bcl-2, and Bcl-xL, were performed with quantitative real-time polymerase chain reaction or Western blot.

RESULTS

Patients with UC in remission showed significantly more IL-22-positive immune cells, but no difference of epithelial c-Myc levels, in mucosa compared with healthy controls. Overexpression of SOCS3 nearly abolished IL-22-induced activation of STAT3. By inhibiting STAT3 signaling, SOCS3 influenced IL-22-induced expression of DMBT1, c-Myc, Survivin, and Bcl-2 as well as proliferation and migration processes in cultured IEC cell line.

CONCLUSIONS

SOCS3 overexpression impairs IL-22-mediated epithelial homeostasis and mucosal wound healing, which could be the mechanism for high SOCS3 IEC expression contributed early relapse of mucosal inflammation. Prevention of SOCS3 expression or enhancement of IL-22/STAT3 signaling in IEC seems to be rational therapeutic strategies for UC remission maintenance.

rIL-22 as an adjuvant enhances the immunogenicity of rGroEL in mice and its protective efficacy against S. Typhi and S. Typhimurium

Salmonella infection, ranging from mild, self-limiting diarrhea to severe gastrointestinal, septicemic disease and enteric fever, is a global health problem both in humans and animals. Rapid development of microbial drug resistance has led to a need for efficacious and affordable vaccines against Salmonella. Microbial heat shock proteins (HSPs), including HSP60 and HSP70, are the dominant antigens that promote the host immune response. Co-administration of these antigens with cytokines, such as IL-22, which plays an important role in antimicrobial defense, can enhance the immune response and protection against pathogens. Therefore, the aim of the present study was to determine the immunogenicity of rGroEL (Hsp60) of S. Typhi, alone or administered in combination with murine rIL-22, and its protective efficacy against lethal infection with Salmonella, in mice. There was appreciable stimulation of the humoral and cell-mediated immune responses in mice immunized with rGroEL alone. However, co-administration of rGroEL with rIL-22 further boosted the antibody titers (IgG, IgG1 and IgG2a), T-cell proliferative responses and the secretion of both Th1 and Th2 cytokines. Additionally, rGroEL alone accorded 65%-70% protection against lethal challenge with S. Typhi and S. Typhimurium, which increased to 90% when co-administered with rIL-22.

Preclinical development of AMG 139, a human antibody specifically targeting IL-23

BACKGROUND AND PURPOSE

AMG 139 is a human anti-IL-23 antibody currently in a phase II trial for treating Crohn's disease. To support its clinical development in humans, in vitro assays and in vivo studies were conducted in cynomolgus monkeys to determine the pharmacology, preclinical characteristics and safety of this monoclonal antibody.

EXPERIMENTAL APPROACH

The in vitro pharmacology, pharmacokinetics (PK), pharmacodynamics and toxicology of AMG 139, after single or weekly i.v. or s.c. administration for up to 26 weeks, were evaluated in cynomolgus monkeys.

KEY RESULTS

AMG 139 bound with high affinity to both human and cynomolgus monkey IL-23 and specifically neutralized the biological activity of IL-23 without binding or blocking IL-12. After a single dose, linear PK with s.c. bioavailability of 81% and mean half-life of 8.4-13 days were observed. After weekly s.c. dosing for 3 or 6 months, AMG 139 exposure increased approximately dose-proportionally from 30 to 300 mg·kg(-1) and mean accumulation between the first and last dose ranged from 2- to 3.5-fold. Peripheral blood immunophenotyping, T-cell-dependent antigen responses and bone formation markers were not different between AMG 139 and vehicle treatment. No adverse clinical signs, effects on body weight, vital signs, ophthalmic parameters, clinical pathology, ECG, organ weights or histopathology were observed in the monkeys with the highest dose of AMG 139 tested (300 mg·kg(-1) s.c. or i.v.).

CONCLUSIONS AND IMPLICATIONS

The in vitro pharmacology, PK, immunogenicity and safety characteristics of AMG 139 in cynomolgus monkeys support its continued clinical development for the treatment of various inflammatory diseases.

Interleukin-22 regulates the complement system to promote resistance against pathobionts after pathogen-induced intestinal damage

Pathobionts play a critical role in disease development, but the immune mechanisms against pathobionts remain poorly understood. Here, we report a critical role for interleukin-22 (IL-22) in systemic protection against bacterial pathobionts that translocate into the circulation after infection with the pathogen Clostridium difficile. Infection with C. difficile induced IL-22, and infected Il22(-/-) mice harbored high numbers of pathobionts in extraintestinal organs despite comparable pathogen load and intestinal damage in mutant and wild-type mice. Pathobionts exhibited increased resistant against complement-mediated phagocytosis, and their intravenous administration resulted in high animal mortality. Selective removal of translocated commensals rescued Il22(-/-) mice, and IL-22 administration enhanced the elimination of pathobionts. Mechanistically, IL-22 augmented bacterial phagocytosis by increasing the expression and bacterial binding of complement C3. Our study demonstrates an unexpected role for IL-22 in controlling the elimination of pathobionts that enter the systemic circulation through the regulation of the complement system.

The microbiota and helminths: sharing the same niche in the human host

Human gastrointestinal bacteria often share their environment with parasitic worms, allowing physical and physiological interaction between the two groups. Such associations have the potential to affect host health as well as the bacterial and helminth populations. Although still in its early stages, research on the interaction between the microbiome and parasitic helminths in humans offers the potential to improve health by manipulating the microbiome. Previously, supplementation with various nutritional compounds has been found to increase the abundance of potentially beneficial gut commensal bacteria. Thus, nutritional microbiome manipulation to produce an environment which may decrease malnutrition associated with helminth infection and/or aid host recovery from disease is conceivable. This review discusses the influence of the gut microbiota and helminths on host nutrition and immunity and the subsequent effects on the human host's overall health. It also discusses changes occurring in the microbiota upon helminth infections and the underlying mechanisms leading to these changes. There are still significant knowledge gaps which need to be filled before meaningful progress can be made in translating knowledge from studying the human gut microbiome into therapeutic strategies. Ultimately this review aims to discuss our current knowledge as well as highlight areas requiring further investigation.

Interleukin-22: a likely target for treatment of autoimmune diseases

Interleukin-22 (IL-22) is a member of IL-10 family cytokines that is produced by many different types of lymphocytes including both those of the innate and adaptive immune systems. This includes activated T cells, most notably Th17 and Th22 cells, and NK cells, γδ T cells, LTi cells and LTi-like cells. IL-22 mediates its effects via the IL-22-IL-22R complex and subsequent Janus kinase-signal transducer and activators of transcription (JAK-STAT) signaling pathway. Recently accumulated evidence has indicated that IL-22 also plays an important role in the pathogenesis of many autoimmune diseases. In this review, we discuss the recent findings and advancement of the role for IL-22 in several autoimmune diseases, such as psoriasis, rheumatoid arthritis (RA), hepatitis, graft versus host disease (GHVD) and allergic diseases, implicating that target IL-22 may have a therapeutic potential in those autoimmune diseases.

Unexpected role for IL-17 in protective immunity against hypervirulent Mycobacterium tuberculosis HN878 infection

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), infects one third of the world's population. Among these infections, clinical isolates belonging to the W-Beijing appear to be emerging, representing about 50% of Mtb isolates in East Asia, and about 13% of all Mtb isolates worldwide. In animal models, infection with W-Beijing strain, Mtb HN878, is considered "hypervirulent" as it results in increased mortality and causes exacerbated immunopathology in infected animals. We had previously shown the Interleukin (IL) -17 pathway is dispensable for primary immunity against infection with the lab adapted Mtb H37Rv strain. However, it is not known whether IL-17 has any role to play in protective immunity against infection with clinical Mtb isolates. We report here that lab adapted Mtb strains, such as H37Rv, or less virulent Mtb clinical isolates, such as Mtb CDC1551, do not require IL-17 for protective immunity against infection while infection with Mtb HN878 requires IL-17 for early protective immunity. Unexpectedly, Mtb HN878 induces robust production of IL-1β through a TLR-2-dependent mechanism, which supports potent IL-17 responses. We also show that the role for IL-17 in mediating protective immunity against Mtb HN878 is through IL-17 Receptor signaling in non-hematopoietic cells, mediating the induction of the chemokine, CXCL-13, which is required for localization of T cells within lung lymphoid follicles. Correct T cell localization within lymphoid follicles in the lung is required for maximal macrophage activation and Mtb control. Since IL-17 has a critical role in vaccine-induced immunity against TB, our results have far reaching implications for the design of vaccines and therapies to prevent and treat emerging Mtb strains. In addition, our data changes the existing paradigm that IL-17 is dispensable for primary immunity against Mtb infection, and instead suggests a differential role for IL-17 in early protective immunity against emerging Mtb strains.

MyD88 and TLR9 dependent immune responses mediate resistance to Leishmania guyanensis infections, irrespective of Leishmania RNA virus burden

Infections with Leishmania parasites of the Leishmania Viannia subgenus give rise to both localized cutaneous (CL), and metastatic leishmaniasis. Metastasizing disease forms including disseminated (DCL) and mutocutaneous (MCL) leishmaniasis result from parasitic dissemination and lesion formation at sites distal to infection and have increased inflammatory responses. The presence of Leishmania RNA virus (LRV) in L. guyanensis parasites contributes to the exacerbation of disease and impacts inflammatory responses via activation of TLR3 by the viral dsRNA. In this study we investigated other innate immune response adaptor protein modulators and demonstrated that both MyD88 and TLR9 played a crucial role in the development of Th1-dependent healing responses against L. guyanensis parasites regardless of their LRV status. The absence of MyD88- or TLR9-dependent signaling pathways resulted in increased Th2 associated cytokines (IL-4 and IL-13), which was correlated with low transcript levels of IL-12p40. The reliance of IL-12 was further confirmed in IL12AB^−/− mice, which were completely susceptible to infection. Protection to L. guyanensis infection driven by MyD88- and TLR9-dependent immune responses arises independently to those induced due to high LRV burden within the parasites.

Interleukin-22: a likely target for treatment of autoimmune diseases

Interleukin-22 (IL-22) is a member of IL-10 family cytokines that is produced by many different types of lymphocytes including both those of the innate and adaptive immune systems. This includes activated T cells, most notably Th17 and Th22 cells, and NK cells, γδ T cells, LTi cells and LTi-like cells. IL-22 mediates its effects via the IL-22-IL-22R complex and subsequent Janus kinase-signal transducer and activators of transcription (JAK-STAT) signaling pathway. Recently accumulated evidence has indicated that IL-22 also plays an important role in the pathogenesis of many autoimmune diseases. In this review, we discuss the recent findings and advancement of the role for IL-22 in several autoimmune diseases, such as psoriasis, rheumatoid arthritis (RA), hepatitis, graft versus host disease (GHVD) and allergic diseases, implicating that target IL-22 may have a therapeutic potential in those autoimmune diseases.

Role of IL-22 in microbial host defense

Interleukin (IL)-22 is a member of the IL-10 family of cytokines, which, besides IL-10, contains seven additional cytokines. Although the founding member IL-10 is an important immunoregulatory cytokine that represses both innate and adaptive immunity, the other family members preferentially target epithelial cells and enhance innate host defense mechanisms against various pathogens such as bacteria, yeast, and viruses. Based on their functions, the IL-10 family can be further divided into three subgroups, IL-10 itself, the IL-20 subfamily, and the IFNλ subfamily. IL-22 is the best-studied member of the IL-20 subfamily, and exemplifies the diverse biological effects of this subfamily. IL-22 elicits various innate immune responses from epithelial cells and is essential for host defense against several invading pathogens, including Citrobacter rodentium and Klebsiella pneumonia. IL-22 also protects tissue integrity and maintains the mucosal homeostasis. On the other hand, IL-22 is a proinflammatory cytokine with the capacity to amplify inflammatory responses, which might result in tissue damage, e.g., the IL-22-dependent necrosis of the small intestine during Toxoplasma gondii infection.

Therapeutic opportunities of the IL-22-IL-22R1 system

Interleukin-22 (IL-22) is a key effector molecule that is produced by activated T cells, including T helper 22 (TH22) cells, TH17 cells and TH1 cells, as well as subsets of innate lymphoid cells. Although IL-22 can act synergistically with IL-17 or tumour necrosis factor, some important functions of IL-22 are unique to this cytokine. Data obtained over the past few years indicate that the IL-22-IL-22 receptor subunit 1 (IL-22R1) system has a high potential clinical relevance in psoriasis, ulcerative colitis, graft-versus-host disease, certain infections and tumours, as well as in liver and pancreas damage. This Review highlights current knowledge of the biology of the IL-22-IL-22R1 system, its role in inflammation, tissue protection, regeneration and antimicrobial defence, as well as the positive and potentially negative consequences of its therapeutic modulation.

The biology and functions of Th22 cells

T helper (Th) cells develop from naïve CD4(+) T cells under lineage-specific culture conditions and are nominated by their lineage-specific cytokines. Th22 cells, new players in adoptive immune responses, are identified by the production of interleukin (IL)-22. Plenty of observations are obtained over the past few years indicating that IL-22 is produced by activated T cells including Th22 cells, Th17 cells, Th1 cells, innate lymphoid cells and some nonlymphocytes. IL-22 functions synergistically with IL-17 or tumor necrosis factor (TNF), however, it plays different roles by IL-22/IL-22 receptor signal transductions in pathologic processes, including inflammations, autoimmunity, tumor, and digestive organs damages. In this chapter, we focus on the biology of IL-22, the generation and regulation of Th22 cells, the possible signal pathways that involved in the functions of Th22 cells, as well as the relationship between Th22 cells and various diseases.

Th17 cells in immunity and autoimmunity

Th17 and IL-17 play important roles in the clearance of extracellular bacterial and fungal infections. However, strong evidence also implicates the Th17 lineage in several autoimmune disorders including multiple sclerosis, psoriasis, rheumatoid arthritis, inflammatory bowel disease, systemic lupus erythematosus, and asthma. The Th17 subset has also been connected with type I diabetes, although whether it plays a role in the pathogenicity of or protection from the disease remains a controversial issue. In this review we have provided a comprehensive overview of Th17 pathogenicity and function, including novel evidence for a protective role of Th17 cells in conjunction with the microbiota gut flora in T1D onset and progression.

Co-expression of S. Typhi GroEL and IL-22 gene augments immune responses against Salmonella infection

Recombinant DNA vaccines represent a novel method for generating in situ expression of vaccine antigens. Intramuscular injections of naked DNA are able to elicit potent humoral and cellular immune responses but still numerous factors limit the immunogenicity of DNA vaccines. Co-expression of cytokines with antigen encoding genes in DNA vectors can improve the immune responses and modify Th1/Th2 balance. In this study, the immunomodulatory effect of Interleukin 22 (IL-22) as an adjuvant was studied by DNA vaccination with S. Typhi Heat shock protein 60 (HSP60/GroEL) in mice. Further, DNA construct of IL-22 gene fused with GroEL was developed and immunization studies were carried out in mice. DNA vaccination with GroEL alone stimulated humoral and cell-mediated immune responses. Co-immunization (IL-22+GroEL) further resulted in increase in T-cell proliferative responses, antibody titres (IgG, IgG1, IgG2a) and secretion of IFNγ (Th1), IL-1β and Th2 (IL-4, IL-6) cytokines. Co-expression (IL-22-GroEL DNA) also promoted antibody titres and cytokine levels were significantly higher as compared to co-immunized group. A reduction in bacterial load in spleen, liver and intestine was seen in all the immunized groups as compared to control, with least organ burden in fusion DNA construct group (co-expression). Improved protective efficacy (90%) against lethal challenge by Salmonella was observed with IL-22-GroEL co-expressing DNA vector as compared with plasmid encoding GroEL only (50-60%) or co-immunization group (75-80%). This study thus shows that co-expression of IL-22 and GroEL genes enhances the immune responses and protective efficacy, circumventing the need of any adjuvant.

Nontuberculous mycobacterial infections in children with inborn errors of the immune system

Severe mycobacterial disease is mostly confined to patients who are immunocompromized either by acquired or inherited causes. One such genetic disorder is Mendelian Susceptibility to Mycobacterial Disease (MSMD), a hot topic within the field of primary immunodeficiency. This single gene disorder is characterized by isolated infection with mycobacteria or Salmonella due to a defect in the type-1 cytokine response. In the last two decades, ten genes have been labeled as causing MSMD when they harbor germline mutations, namely IL12B, IL12RB1, IFNGR1, IFNGR2, STAT1, IKBKG, CYBB, TYK2, IRF8 and ISG15. The mutations lead to either insufficient production of IFN-γ, or to an insufficient response to the cytokine. Current treatment options include recombinant IFN-γ and hematologic stem cell transplantation (HSCT). In the future, gene therapy, antisense-mediated exon skipping and chemical intervention in glycosylation problems may become successful alternatives. Furthermore, it is likely that many new candidate genes and pathways crucial for mycobacterial immunity will be identified.

Interleukin-22 as a molecular adjuvant facilitates IL-17-producing CD8+ T cell responses against a HBV DNA vaccine in mice

Interleukin-22 (IL-22) is mainly produced by activated Th1 cells, Th17 cells and NK cells and promotes anti-microbial defense, pro-inflammatory and tissue remodeling responses. However, its potential use as a vaccine adjuvant has not been tested. In this study, we tested if a DNA construct expressing IL-22 (pVAX-IL-22) could be used as a molecular adjuvant to enhance host immune responses induced by HBV DNA vaccination (pcD-S2). After immunizing mice with pcD-S2 combined with pVAX-IL-22, we didn't find enhancement of HBsAg-specific antibody responses in comparison to mice immunized with pcD-S2 alone. However, there was an enhancement of the level of IL-17 expression in antigen specific CD8(+) cytotoxic T lymphocytes (Tc17). By using CD8 T-cell knockout (KO) and IL-17 KO mice, Tc17 cells were found to be a dominant population driving cytotoxicity. Importantly, there was a correlation between pVAX-IL-22 enhancement of T lymphocytes and a reduction of HBsAg-positive hepatocytes in HBsAg transgenic mice. These results demonstrate that IL-22 might be used as an effective adjuvant to enhance cellular immune responses during HBsAg DNA vaccination since it can induce Tc17 cells to break tolerance in HBsAg transgenic mice.

Contribution of interleukin-12 p35 (IL-12p35) and IL-12p40 to protective immunity and pathology in mice infected with Chlamydia muridarum

The p35 molecule is unique to interleukin-12 (IL-12), while p40 is shared by both IL-12 and IL-23. IL-12 promotes Th1 T cell responses, while IL-23 promotes Th17 T cell responses. The roles of IL-12p35- and IL-12p40-mediated responses in chlamydial infection were compared in mice following an intravaginal infection with Chlamydia muridarum. Mice deficient in either IL-12p35 or p40 both developed similar but prolonged infection time courses, confirming the roles of IL-12-mediated immune responses in clearing primary infection. However, all mice, regardless of genotype, cleared reinfection within 2 weeks, suggesting that an IL-12- or IL-23-independent adaptive immunity is protective against chlamydial infection. All infected mice developed severe oviduct hydrosalpinx despite the increased Th2 responses in IL-12p35- or IL-12p40-deficient mice, suggesting that Th2-dominant responses can contribute to Chlamydia-induced inflammatory pathology. Compared to IL-12p35 knockout mice, the IL-12p40-deficient mice exhibited more extensive spreading of chlamydial organisms into kidney tissues, leading to significantly increased incidence of pyelonephritis, which both confirms the role of IL-12 or IL-23-independent host responses in Chlamydia-induced pathologies and suggests that in the absence of IL-12/IFN-γ-mediated Th1 immunity, an IL-23-mediated response may play an important role in restricting chlamydial organisms from spreading into distal organs. These observations together provide important information for both understanding chlamydial pathogenesis and developing anti-Chlamydia vaccines.

Role of murine intestinal interleukin-1 receptor 1-expressing lymphoid tissue inducer-like cells in Salmonella infection

Interleukin (IL)-1 signaling plays a critical role in intestinal immunology. Here, we report that the major population of intestinal lamina propria lymphocytes expressing IL-1 receptor 1 (IL-1R1) is the lymphoid tissue inducer (LTi)-like cell, a type of innate lymphoid cell. These cells are significant producers of IL-22, and this IL-22 production depends on IL-1R1 signaling. LTi-like cells are required for defense against Salmonella enterica serovar Typhimurium. Moreover, colonic LTi-like cell numbers depend on the presence of the intestinal microbiota. LTi-like cells require IL-1R1 for production of protective cytokines and confer protection in infectious colitis, and their cell numbers in the colon depend upon having a microbiome.