A role for IL-27 in limiting T regulatory cell populations

An updated advancement of bifunctional IL-27 in inflammatory autoimmune diseases

Interleukin-27 (IL-27) is a member of the IL-12 family. The gene encoding IL-27 is located at chromosome 16p11. IL-27 is considered as a heterodimeric cytokine, which consists of Epstein-Barr virus (EBV)-induced gene 3 (Ebi3) and IL-27p28. Based on the function of IL-27, it binds to receptor IL-27rα or gp130 and then regulates downstream cascade. To date, findings show that the expression of IL-27 is abnormal in different inflammatory autoimmune diseases (including systemic lupus erythematosus, rheumatoid arthritis, Sjogren syndrome, Behcet's disease, inflammatory bowel disease, multiple sclerosis, systemic sclerosis, type 1 diabetes, Vogt-Koyanagi-Harada, and ankylosing spondylitis). Moreover, in vivo and in vitro studies demonstrated that IL-27 is significantly in3volved in the development of these diseases by regulating innate and adaptive immune responses, playing either an anti-inflammatory or a pro-inflammatory role. In this review, we comprehensively summarized information about IL-27 and autoimmunity based on available evidence. It is hoped that targeting IL-27 will hold great promise in the treatment of inflammatory autoimmune disorders in the future.

IL-27 in combination with anti-PD-1 can be anti-cancer or pro-cancer

Interleukin-27 (IL-27) is known to play opposing roles in immunology. The present paper considers, specifically, the role IL-27 plays in cancer immunotherapy when combined with immune checkpoint inhibitor anti-PD-1. We first develop a mathematical model for this combination therapy, by a system of Partial Differential Equations, and show agreement with experimental results in mice injected with melanoma cells. We then proceed to simulate tumor volume with IL-27 injection at a variable dose F and anti-PD-1 at a variable dose g. We show that in some range of "small" values of g, as f increases tumor volume decreases as long as fFc(g), where Fc(g) is a monotone increasing function of g. This demonstrates that IL-27 can be both anti-cancer and pro-cancer, depending on the ranges of both anti-PD-1 and IL-27.

IL-27p28 specifically regulates MHC II expression in macrophages through CIITA

Antigen-presenting cells (APCs) constantly express major histocompatibility complex II (MHC II), including macrophages and dendritic cells (DCs) which deliver antigens to CD4+ T cells and play an important role in adaptive immunity. The expression of MHC II is controlled by the transcriptional coactivator CIITA. Interleukin-27 (IL-27), a newly discovered IL-12 family cytokine, is composed of p28 and EBI3 subunits. In this study, we used IL-27p28 conditional knock-out mice to investigate the regulatory effects of IL-27p28 on macrophage polarization and the expression of MHC II in macrophages. We found that MHC II expression was upregulated in the bone marrow-derived and peritoneal exudate macrophages (BMDMs; PEMs) from IL-27p28-deficient mice, with their inflammation regulating function unaffected. We also demonstrated that in the APCs, IL-27p28 selectively regulated MHC II expression in macrophages but not in dendritic cells. During Pseudomonas aeruginosa (P. aeruginosa) reinfection, higher survival rate, bacterial clearance, and ratio of CD4+/CD8+ T cells in the spleen during the specific immune phase were observed in IL-27p28 defect mice, as well as an increased MHC II expression in alveolar macrophages (AMs). But these did not occur in the first infection. For the first time we discovered that IL-27p28 specifically regulates the expression of MHC II in macrophages by regulating CIITA, while its absence enhances antigen presentation and adaptive immunity against P. aeruginosa.

IL-27 Gene Therapy Induces Stat3-Mediated Expansion of CD11b+Gr1+ Myeloid Cells and Promotes Accumulation of M1 Macrophages in the Tumor Microenvironment

IL-27 is a pleiotropic cytokine that exhibits stimulatory/regulatory functions on multiple lineages of immune cells and has a potential to be used as a therapeutic for cancer. We have recently demonstrated that administration of IL-27 producing adeno-associated virus (AAV-IL-27) exhibits potent inhibition of tumor growth in mouse models. In this study, we demonstrate that AAV-IL-27 treatment leads to significant expansion of CD11b+Gr1+ myeloid cells. AAV-IL-27-induced expansion of CD11b+Gr1+ cells is IL-27R-dependent and requires Stat3 signaling, but it is inhibited by Stat1 signaling. AAV-IL-27 treatment does not increase the self-renewal capacity of CD11b+Gr1+ cells but induces significant expansion of Lin-Sca1+c-Kit+ (LSK) and granulocyte-monocyte progenitor cells. Despite exhibiting significant suppression of T cells in vitro, IL-27-induced CD11b+Gr1+ cells lost the tumor-promoting activity in vivo and overall play an antitumor role. In tumors from AAV-IL-27-treated mice, CD11b+Gr1+ cells are largely F4/80+ and express high levels of MHC class I/II and M1 macrophage markers. Thus, IL-27 gene therapy induces Stat3-mediated expansion of CD11b+Gr1+ myeloid cells and promotes accumulation of M1 macrophages in the tumor microenvironment.

Tr1 cell-mediated protection against autoimmune disease by intranasal administration of a fusion protein targeting cDC1 cells

Curative therapies against autoimmune diseases are lacking. Indeed, most of the currently available treatments are only targeting symptoms. We have developed a novel strategy for a therapeutic vaccine against autoimmune diseases based on intranasal administration of a fusion protein tolerogen, which consists of a mutant, enzymatically inactive, cholera toxin A1 (CTA1)-subunit genetically fused to disease-relevant high-affinity peptides and a dimer of D-fragments from protein A (DD). The CTA1 R7K mutant - myelin oligodendrocyte glycoprotein (MOG), or proteolipid protein (PLP) - DD (CTA1R7K-MOG/PLP-DD) fusion proteins effectively reduced clinical symptoms in the experimental autoimmune encephalitis model of multiple sclerosis. The treatment induced Tr1 cells, in the draining lymph node, which produced interleukin (IL)-10 and suppressed effector clusters of differentiation 4+ T-cell responses. This effect was dependent on IL-27 signaling because treatment was ineffective in bone marrow chimeras lacking IL-27Ra within their hematopoietic compartment. Single-cell RNA sequencing of dendritic cells in draining lymph nodes demonstrated distinct gene transcriptional changes of classic dendritic cells 1, including enhanced lipid metabolic pathways, induced by the tolerogenic fusion protein. Thus, our results with the tolerogenic fusion protein demonstrate the possibility to vaccinate and protect against disease progression by reinstating tolerance in multiple sclerosis and other autoimmune diseases.

Antiviral response and immunopathogenesis of interleukin 27 in COVID-19

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with a high mortality rate. The clinical course is attributed to the severity of pneumonia and systemic complications. In COVID-19 patients and murine models of SARS-CoV-2 infection, the disease may be accompanied by excessive production of cytokines, leading to an accumulation of immune cells in affected organs such as lungs. Previous reports have shown that SARS-CoV-2 infection antagonizes interferon (IFN)-dependent antiviral response, thereby preventing the expression of IFN-stimulated genes (ISGs). Lower IFN levels have been linked to more-severe COVID-19. Interleukin 27 (IL27) is a heterodimeric cytokine composed of IL27p28 and EBI3 subunits, which induce both pro- and anti-inflammatory responses. Recently, we and others have reported that IL27 also induces a strong antiviral response in an IFN-independent manner. Here, we investigated transcription levels of both IL27 subunits in COVID-19 patients. The results show that SARS-CoV-2 infection modulates TLR1/2-MyD88 signaling in PBMCs and monocytes and induces NF-κB activation and expression of NF-κB-target genes that are dependent on a robust pro-inflammatory response, including EBI3; and activates IRF1 signaling which induces IL27p28 mRNA expression. The results suggest that IL27 induces a robust STAT1-dependent pro-inflammatory and antiviral response in an IFN-independent manner in COVID-derived PBMCs and monocytes as a function of a severe clinical course of COVID-19. Similar results were observed in macrophages stimulated with the SARS-CoV-2 spike protein. Thus, IL27 can trigger an antiviral response in the host, suggesting the possibility of novel therapeutics against SARS-CoV-2 infection in humans.

Interleukin-27 Ameliorates Atherosclerosis in ApoE-/- Mice through Regulatory T Cell Augmentation and Dendritic Cell Tolerance

Atherosclerosis, which is characterized by chronic inflammation in the arterial wall, is driven by immune cells and cytokines. Recent evidence indicated that interleukin (IL)-27 showed pleiotropic properties in immune diseases. However, precise mechanisms of IL-27, especially in atherosclerosis remains unknown. In our research, we examined the influence of the administration of IL-27 and an anti-IL-27p28 antibody (anti-IL-27p28-Ab) on both the initiation and the progression of atherosclerosis. In the groups (both the initiation and the progression) receiving recombinant IL-27 administration, the formation of atherosclerotic plaques was suspended, and the percentage of regulatory T cells (LAP⁺ or Foxp3⁺) in the spleen and peripheral blood was increased. Meanwhile, the number of T helper 1 (Th1) and T helper 17 (Th17) cells was decreased. In the peripheral blood plasma, TGF-β and IL-10 expression were increased, while the levels of IFN-γ and IL-17 were reduced. As for lesions, the mRNA expression of Foxp3, TGF-β, and IL-10 was increased, while that of IFN-γ and IL-17 was reduced. In the anti-IL-27p28 antibody groups, we obtained opposite results. We also observed that DCs treated with IL-27 display a tolerogenic phenotype and that IL-27–treated tolerogenic DCs (tDCs) are likely to play a protective role during atherosclerosis. Our study indicates that IL-27 or adoptive transfer of IL-27 loaded tDCs may be a new therapeutic approach in atherosclerosis.

The dual role of IL-27 in CD4+T cells

Interleukin-27 (IL-27), a member of the IL-6/IL-12 family, has diverse regulatory functions in various immune responses, and is recognised as a potent agonist and antagonist of CD4+T cells in different contexts. However, this dual role and underlying mechanisms have not been completely defined. In the present review, we summarise the dual role of IL-27 in CD4+T cells. In particular, we aimed to decipher its mechanism to better understand the context-dependent function of IL-27 in CD4+T cells. Furthermore, we propose a possible mechanism for the dual role of IL-27. This may be helpful for the development of appropriate IL-27 treatments in various clinical settings.

IL-30† (IL-27A): a familiar stranger in immunity, inflammation, and cancer

Over the years, interleukin (IL)-27 has received much attention because of its highly divergent, sometimes even opposing, functions in immunity. IL-30, the p28 subunit that forms IL-27 together with Ebi3 and is also known as IL-27p28 or IL-27A, has been considered a surrogate to represent IL-27. However, it was later discovered that IL-30 can form complexes with other protein subunits, potentially leading to overlapping or discrete functions. Furthermore, there is emerging evidence that IL-30 itself may perform immunomodulatory functions independent of Ebi3 or other binding partners and that IL-30 production is strongly associated with certain cancers in humans. In this review, we will discuss the biology of IL-30 and other IL-30-associated cytokines and their functions in inflammation and cancer.

Studying the ways that interleukin IL-30 regulates immune responses may provide novel insights into tumor development and inflammatory conditions. Interleukins are a diverse family of proteins involved in intercellular communications and immunity, where they can exert divergent and even opposing functions. Booki Min at Northwestern University in Chicago, USA, and co-workers reviewed the current understanding of IL-30 and its links to inflammation and cancer. IL-30 forms the IL-27 complex with the Ebi3 protein and was thought to be a surrogate for IL-27 in terms of activity. However, recent insights suggest that IL-30 may perform discrete immune modulation functions. Elevated IL-30 secretion is linked to prostate and breast cancer development. Extensive research is needed into the formation of IL-30, its associated protein interactions, and the development of a suitable animal model.

Is AAV-delivered IL-27 a potential immunotherapeutic for cancer?

Cytokines are one of the first immunotherapeutics utilized in trials of human cancers with significant success. However, due to their significant toxicity and often lack of efficacy, cytokines have given their spotlight to other cancer immunotherapeutics such as immune checkpoint inhibitors. Nevertheless, only a subset of cancer patients respond to checkpoint inhibitors. Therefore, developing a novel cytokine-based immunotherapy is still necessary. Among an array of cytokine candidates, IL-27 is a unique one that exhibits clear anti-tumor activity with low toxicity. Systemically delivered IL-27 by adeno-associated virus (AAV-IL-27) is very well tolerized by mice and exhibits potent anti-tumor activity in a variety of tumor models. AAV-IL-27 exerts its anti-tumor activity through directly stimulation of immune effector cells and systemic depletion of Tregs, and is particularly suitable for delivery in combination with checkpoint inhibitors or vaccines. Additionally, AAV-IL-27 can also be delivered locally to tumors to exert its unique actions. In this review, we summarize the evidence that support these points and propose AAV-delivered IL-27 as a potential immunotherapeutic for cancer.

The immunomodulatory potentials of interleukin-27 in airway allergies

Allergic airway disorders such as asthma and allergic rhinitis are mainly caused by inhaled allergen-induced improper activation and responses of immune and non-immune cells. One important response is the production of IL-27 by macrophages and dendritic cells (DCs) during the early stage of airway allergies. IL-27 exerts powerful modulatory influences on the cells of innate immunity [eg neutrophils, eosinophils, mast cells, monocytes, macrophages, dendritic cells (DCs), innate lymphoid cells (ILCs), natural killer (NK) cells and NKT cells)] and adaptive immunity (eg Th1, Th2, Th9, Th17, regulatory T, CD8⁺ cytotoxic T and B cells). The IL-27-mediated signalling pathways may be modulated to attenuate asthma and allergic rhinitis. In this review, a comprehensive discussion concerning the roles carried out by IL-27 in asthma and allergic rhinitis was provided, while evidences are presented favouring the use of IL-27 in the treatment of airway allergies.

Influence of age on the diagnostic accuracy of soluble biomarkers for tuberculous pleural effusion: a post hoc analysis

BACKGROUND

Accurately diagnosing pleural effusion is a frequent and significant problem in clinical practice. Combining pleural biomarkers with patients' age may be a valuable method for diagnosing TPE. We sought to evaluate the influence of age on diagnostic values of pleural adenosine deaminase (ADA), interferon-gamma (IFN-γ), and interleukin 27 (IL-27) for tuberculous pleural effusion (TPE).

METHODS

Two hundred seventy-four consecutive adult patients with pleural effusion were selected from Beijing and Wuhan between January 1, 2014 and June 30, 2015, and their pleural fluid concentrations of ADA, IFN-γ, and IL-27 were tested. Biomarker performance was analyzed by standard receiver operating characteristic (ROC) curves according to different ages.

RESULTS

Data from the Beijing cohort showed that ADA, IFN-γ, and IL-27 could all accurately diagnose TPE in young patients (≤ 40 years of age). With a cutoff of 21.4 U/L, the area under the curve (AUC), sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of ADA for diagnosing TPE were 1.000 (95% confidence interval: 0.884-1.000), 100.0, 100.0%, 100.0, and 100.0, respectively. In older patients (> 40 years of age), IL-27 and IFN-γ were excellent biomarkers for discriminating TPE versus non-TPE cases. With a cutoff of 591.4 ng/L, the AUC, sensitivity, specificity, PPV, and NPV of IL-27 for diagnosing TPE were 0.976 (95% confidence interval: 0.932-0.995), 96.3, 99.0%, 96.3, and 99.0, respectively. Similar diagnostic accuracy among the three pleural biomarkers was validated in the Wuhan cohort.

CONCLUSIONS

Among young patients, ADA is reliable for diagnosing TPE. Conversely, in older patients, IL-27 and IFN-γ are excellent biomarkers to differentiate TPE versus non-TPE cases.

Interleukin-27 Is Essential for Type 1 Diabetes Development and Sjögren Syndrome-like Inflammation

Human genetic studies implicate interleukin-27 (IL-27) in the pathogenesis of type 1 diabetes (T1D), but the underlying mechanisms remain largely unexplored. To further define the role of IL-27 in T1D, we generated non-obese diabetic (NOD) mice deficient in IL-27 or IL-27Rα. In contrast to wild-type NOD mice, both NOD.Il27-/- and NOD.Il27ra-/- strains are completely resistant to T1D. IL-27 from myeloid cells and IL-27 signaling in T cells are critical for T1D development. IL-27 directly alters the balance of regulatory T cells (Tregs) and T helper 1 (Th1) cells in pancreatic islets, which in turn modulates the diabetogenic activity of CD8 T cells. IL-27 also directly enhances the effector function of CD8 T cells within pancreatic islets. In addition to T1D, IL-27 signaling in T cells is also required for lacrimal and salivary gland inflammation in NOD mice. Our study reveals that IL-27 contributes to autoimmunity in NOD mice through multiple mechanisms and provides substantial evidence to support its pathogenic role in human T1D.

Impact of Interleukin-27p28 on T and B Cell Responses during Toxoplasmosis

Interleukin-27 (IL-27) is a heterodimeric cytokine composed of the subunits IL-27p28 and EBi3, and while the IL-27 heterodimer influences T cell activities, there is evidence that IL-27p28 can have EBi3-independent activities; however, their relevance to infection is unclear. Therefore, the studies presented here compared how IL-27p28 transgenics and IL-27p28-/- mice responded to the intracellular parasite Toxoplasma gondii While the loss of IL-27p28 and its overexpression both result in increased susceptibility to T. gondii, the basis for this phenotype reveals distinct roles for IL-27p28. As a component of IL-27, IL-27p28 is critical to limit infection-induced T cell-mediated pathology, whereas the ectopic expression of IL-27p28 reduced the effector T cell population and had a major inhibitory effect on parasite-specific antibody titers and a failure to control parasite replication in the central nervous system. Indeed, transfer of immune serum to infected IL-27p28 transgenics resulted in reduced parasite burden and pathology. Thus, IL-27p28, independent of its role as a component of IL-27, can act as a negative regulator of humoral and cellular responses during toxoplasmosis.

IL-27, IL-30, and IL-35: A Cytokine Triumvirate in Cancer

The role of the immune system in anti-tumor immunity cannot be overstated, as it holds the potential to promote tumor eradication or prevent tumor cell escape. Cytokines are critical to influencing the immune responses and interactions with non-immune cells. Recently, the IL-12 and IL-6 family of cytokines have accumulated newly defined members each with specific immune functions related to various cancers and tumorigenesis. There is a need to better understand how cytokines like IL-27, IL-30, and IL-35 interact with one another, and how a developing tumor can exploit these interactions to enhance immune suppression. Current cytokine-based immunotherapies are associated with cytotoxic side effects which limits the success of treatment. In addition to this toxicity, understanding the complex interactions between immune and cancer cells may be one of the greatest challenges to developing a successful immunotherapy. In this review, we bring forth IL-27, IL-30, and IL-35, “sister cytokines,” along with more recent additions to the IL-12 family, which serve distinct purposes despite sharing structural similarities. We highlight how these cytokines function in the tumor microenvironment by examining their direct effects on cancer cells as well their indirect actions via regulatory functions of immune cells that act to either instigate or inhibit tumor progression. Understanding the context dependent immunomodulatory outcomes of these sister cytokines, as well as their regulation within the tumor microenvironment, may shed light onto novel cancer therapeutic treatments or targets.

IL-27 Expression and Responsiveness in Human Uterine Epithelial Cells and Fibroblasts In Vitro and the Role of Estradiol

Interleukin (IL)-27 is a pleiotropic cytokine that regulates multiple aspects of innate and adaptive immunity, but whose role in immune protection of the female reproductive tract is unknown. Although not constitutively expressed by human uterine epithelial cells and fibroblasts in culture, IL-27 secretion was upregulated after treatment with the viral ligand poly (I:C) in a type I interferon (IFN)-dependent manner, with higher levels measured in fibroblasts than epithelial cells. Estradiol increased poly (I:C)-induced IL-27 production by fibroblasts, but not epithelial cells. While both cell types expressed the IL-27 receptor, only fibroblasts responded to recombinant IL-27 with increased expression of the antiviral genes, APOBEC3G (apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G) and MxA, and the tryptophan-catabolizing enzyme, indoleamine 2,3-dioxygenase (IDO). Estradiol inhibited IL-27-mediated induction of IDO in fibroblasts through estrogen receptor alpha, but had no effect on APOBEC3G. IL-27 pretreatment also potentiated poly (I:C) upregulation of the antiviral genes, OAS2 and APOBEC3G, in fibroblasts. Thus, IL-27 is part of the antiviral response by uterine cells against potential pathogens. The effect of estradiol on IL-27 production and sensitivity by fibroblasts demonstrates a selective hormone action on individual cell types in the uterus and suggests that IL-27 may have differential effects during the menstrual cycle.

IL-27 in patients with Chikungunya fever: A possible chronicity biomarker?

BACKGROUND/PURPOSE

Although many patients with chikungunya virus disease (CHIKVD), an arboviral disease characterized by sudden fever and incapacitating poliartralgia, develop chronic articular symptoms, the mechanisms involved in CHIKVD's chronification and its possible biomarkers remain poorly understood. Interleukin (IL)-17A, IL-21, IL-22, IL-29, and transforming growth factor (TGF)-β have been implicated in the pathogenesis of other inflammatory joint diseases, including rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis. Since chronic manifestations of CHIKVD share many clinical and immunological characteristics with those diseases, we assessed the serum levels of those cytokines and analyzed their associations with clinical manifestations in patients with CHIKVD.

METHODS

We evaluated 45 patients (36 female, mean age: 55.2 ± 13.8 years) with CHIKVD serologically confirmed by enzyme-linked immunosorbent assay (ELISA), articular manifestations upon evaluation, and no previous history of inflammatory rheumatologic diseases, along with 49 healthy age- and sex-matched controls. We tested anti-Chikungunya IgM and IgG antibodies and measured IL-17A, IL-21, IL-22, IL-27, IL-29, and TGF-β serum levels with specific ELISA kits.

RESULTS

IL-27, IL-17A, and IL-29 appeared in most patients but not in controls. IL-27 serum levels were higher in patients with chronic symptoms (median: 523.0 pg/mL [62.5-1,048]) than in ones in the acute or subacute stage (median: 62.5 pg/mL [62.5-483.8], p = .008). In patients with CHIKVD, we found significant correlations between IL-27 levels and tender joint counts (r = .32, p = .006), along with associations between IL-17A levels and swollen joint counts (r = .315, p = .0352). Furthermore, patients with arthritis had higher IL-17A levels (median: 23.14 pg/mL [20.6-25.86]) than ones without (median: 20.29 pg/mL [3.91-22.43], p = .0352). We did not detect IL-22 in either group or IL-21 in patients with CHIKVD.

CONCLUSION

Serum levels of IL-17A, IL-27, and IL-29 were high in patients with CHIKVD and had important associations with articular manifestations, which might indicate the inflammatory nature of Chikungunya infection in patients with joint symptoms and the roles of those cytokines in the disease's pathophysiology.

Signaling Through gp130 Compromises Suppressive Function in Human FOXP3+ Regulatory T Cells

The CD4⁺FOXP3⁺ regulatory T cell (Treg) subset is an indispensable mediator of immune tolerance. While high and stable expression of the transcription factor FOXP3 is considered a hallmark feature of Treg cells, our previous studies have demonstrated that the human FOXP3⁺ subset is functionally heterogeneous, whereby a sizeable proportion of FOXP3⁺ cells in healthy individuals have a diminished capacity to suppress the proliferation and cytokine production of responder cells. Notably, these non-suppressive cells are indistinguishable from suppressive Treg cells using conventional markers of human Treg. Here we investigate potential factors that underlie loss of suppressive function in human Treg cells. We show that high expression of the IL-6 family cytokine receptor subunit gp130 identifies Treg cells with reduced suppressive capacity ex vivo and in primary FOXP3⁺ clones. We further show that two gp130-signaling cytokines, IL-6 and IL-27, impair the suppressive capacity of human Treg cells. Finally, we show that gp130 signaling reduces the expression of the transcription factor Helios, whose expression is essential for stable Treg function. These results highlight the role of gp130 in regulating human Treg function, and suggest that modulation of gp130 signaling may serve as a potential avenue for the therapeutic manipulation of human Treg function.

The Immunobiology of the Interleukin-12 Family: Room for Discovery

The discovery of interleukin (IL)-6 and its receptor subunits provided a foundation to understand the biology of a group of related cytokines: IL-12, IL-23, and IL-27. These family members utilize shared receptors and cytokine subunits and influence the outcome of cancer, infection, and inflammatory diseases. Consequently, many facets of their biology are being therapeutically targeted. Here, we review the landmark discoveries in this field, the combinatorial biology inherent to this family, and how patient datasets have underscored the critical role of these pathways in human disease. We present significant knowledge gaps, including how similar signals from these cytokines can mediate distinct outcomes, and discuss how a better understanding of the biology of the IL-12 family provides new therapeutic opportunities.

Interleukin-27 Gene Therapy Prevents the Development of Autoimmune Encephalomyelitis but Fails to Attenuate Established Inflammation due to the Expansion of CD11b+Gr-1+ Myeloid Cells

Interleukin-27 (IL-27) and its subunit P28 (also known as IL-30) have been shown to inhibit autoimmunity and have been suggested as potential immunotherapeutic for autoimmune diseases such as multiple sclerosis (MS). However, the potential of IL-27 and IL-30 as immunotherapeutic, and their mechanisms of action have not been fully understood. In this study, we evaluated the efficacy of adeno-associated viral vector (AAV)-delivered IL-27 (AAV-IL-27) and IL-30 (AAV-IL-30) in a murine model of MS. We found that one single administration of AAV-IL-27, but not AAV-IL-30 completely blocked the development of experimental autoimmune encephalomyelitis (EAE). AAV-IL-27 administration reduced the frequencies of Th17, Treg, and GM-CSF-producing CD4+ T cells and induced T cell expression of IFN-γ, IL-10, and PD-L1. However, experiments involving IL-10-deficient mice and PD-1 blockade revealed that AAV-IL-27-induced IL-10 and PD-L1 expression were not required for the prevention of EAE development. Surprisingly, neither AAV-IL-27 nor AAV-IL-30 treatment inhibited EAE development and Th17 responses when given at disease onset. We found that mice with established EAE had significant expansion of CD11b+Gr-1+ cells, and AAV-IL-27 treatment further expanded these cells and induced their expression of Th17-promoting cytokines such as IL-6. Adoptive transfer of AAV-IL-27-expanded CD11b+Gr-1+ cells enhanced EAE development. Thus, expansion of CD11b+Gr-1+ cells provides an explanation for the resistance to IL-27 therapy in mice with established disease.

IL-27 gene therapy induces depletion of Tregs and enhances the efficacy of cancer immunotherapy

Tumor-induced expansion of Tregs is a significant obstacle to cancer immunotherapy. However, traditional approaches to deplete Tregs are often inefficient, provoking autoimmunity. We show here that administration of IL-27-expressing recombinant adeno-associated virus (AAV-IL-27) significantly inhibits tumor growth and enhances T cell responses in tumors. Strikingly, we found that AAV-IL-27 treatment causes rapid depletion of Tregs in peripheral blood, lymphoid organs, and - most pronouncedly - tumor microenvironment. AAV-IL-27-mediated Treg depletion is dependent on IL-27 receptor and Stat1 in Tregs and is a combined result of CD25 downregulation in Tregs and inhibition of IL-2 production by T cells. In combination with a GM-CSF vaccine, AAV-IL-27 treatment not only induced nearly complete tumor rejection, but also resulted in amplified neoantigen-specific T cell responses. AAV-IL-27 also dramatically increased the efficacy of anti-PD-1 therapy, presumably due to induction of PD-L1 in T cells and depletion of Tregs. Importantly, AAV-IL-27 therapy did not induce significant adverse events, partially due to its induction of IL-10. In a plasmacytoma mouse model, we found that IL-10 was required for AAV-IL-27-mediated tumor rejection. Thus, our study demonstrates the potential of AAV-IL-27 as an independent cancer therapeutic and as an efficient adjuvant for cancer immunotherapy.

Tregs: Where We Are and What Comes Next?

Regulatory T cells are usually recognized as a specialized subset of CD4⁺ T cells functioning in establishment and maintenance of immune tolerance. Meanwhile, there is emerging evidence that regulatory T cells (Tregs) are also present in various non-lymphoid tissues, and that they have unique phenotypes credited with activities distinct from regulatory function. Their development and function have been described in plenty of manuscripts in the past two decades. However, with the deepening of research in recent years, emerging evidence revealed some novel mechanisms about how Tregs exert their activities. First, we discuss the expanding family of regulatory lymphocytes briefly and then, try to interpret how fork-head box P3 (Foxp3), a master regulator of the regulatory pathway in the development and function of regulatory T cells, functions. Subsequently, another part of our focus is varieties of tissue Tregs. Next, we primarily discuss recent research on how Tregs work and their faceted functions in terms of soluble mediators, functional proteins, and inhibitory receptors. In particular, unless otherwise noted, the term “Treg” is used here to refer specially to the “CD4⁺CD25⁺Foxp3^+” regulatory cells.

Treg-specific IL-27Rα deletion uncovers a key role for IL-27 in Treg function to control autoimmunity

Dysregulated Foxp3+ Treg functions result in uncontrolled immune activation and autoimmunity. Therefore, identifying cellular factors modulating Treg functions is an area of great importance. Here, using Treg-specific Il27ra-/- mice, we report that IL-27 signaling in Foxp3+ Tregs is essential for Tregs to control autoimmune inflammation in the central nervous system (CNS). Following experimental autoimmune encephalomyelitis (EAE) induction, Treg-specific Il27ra-/- mice develop more severe EAE. Consistent with the severe disease, the numbers of IFNγ- and IL-17-producing CD4 T cells infiltrating the CNS tissues are greater in these mice. Treg accumulation in the inflamed CNS tissues is not affected by the lack of IL-27 signaling in Tregs, suggesting a functional defect of Il27ra-/- Tregs. IL-10 production by conventional CD4 T cells and their CNS accumulation are rather elevated in Treg-specific Il27ra-/- mice. Analysis with Treg fate-mapping reporter mice further demonstrates that IL-27 signaling in Tregs may control stability of Foxp3 expression. Finally, systemic administration of recombinant IL-27 in Treg-specific Il27ra-/- mice fails to ameliorate the disease even in the presence of IL-27-responsive conventional CD4 T cells. These findings uncover a previously unknown role of IL-27 in regulating Treg function to control autoimmune inflammation.

Dysregulated homeostasis of target tissues or autoantigens - A novel principle in autoimmunity

Monogenic autoimmune disorders provide a powerful tool for our understanding of the principles of autoimmunity due to the obvious impact of a single gene on the disease. So far, approximately 100 single gene defects causing murine monogenic autoimmune disorders have been reported and the functional characterization of these genes will provide significant progress in understanding the nature of autoimmunity. According to their function, genes leading to monogenic autoimmune disorders can be categorized into two groups. An expectable first group contains genes involved in the homeostasis of the immune system, including homeostasis of immune organs and immune cells. Intriguingly, the second group consists of genes functionally involved in the homeostasis of target tissues or autoantigens. According to our novel hypothesis, we propose that autoimmunity represents a consequence of a dysregulated homeostasis of the immune system and/or its targets including autoantigens and target tissues. In this review we refer to both aspects of homeostasis in autoimmunity with a highlight on the role of the homeostasis of target tissues and autoantigens.

Treg cells as potential cellular targets for functionalized nanoparticles in cancer therapy

Treg cell-mediated immune suppression appears to represent a significant barrier to effective anticancer immune responses and their inactivation or removal is viewed as a potential therapeutic approach. Although suitable tools for selective Treg cell manipulation in man are missing, their number and function can be altered by a number of drugs and biologicals and by reprogramming tumor-infiltrating antigen presenting cells. Nanoparticles offer exceptional new options in drug and gene delivery by prolonging the circulation time of their cargo, protecting it from degradation and promoting its local accumulation in cells and tissues. In tumor therapy, the use of nanoparticles is expected to overcome limitations in drug delivery and provide novel means for cell-specific functional alteration. In this perspective, we summarize strategies suitable for interference with Treg-mediated suppression, discuss the potential use of nanoparticles for this purpose and identify additional, unexplored opportunities.

Interleukin-27 as a Novel Therapy for Inflammatory Bowel Disease: A Critical Review of the Literature

Inflammatory bowel disease (IBD) is an inflammatory disorder of the intestine that affects an estimated 329 per 100,000 people in the United States and is increasing in incidence within a number of cultures worldwide. Likely due to its incompletely understood pathophysiology and etiology, the standard treatments for IBD are only efficacious in subsets of patients and often do not induce lasting remission. As a result, novel therapies are needed. The success of anti-tumor necrosis factor-α treatment in a subset of patients with IBD demonstrated that therapy targeting a single cytokine could be efficacious in IBD, and clinical trials investigating the blockade of a variety of cytokines have commenced. Interleukin (IL) 27 is a relatively recently discovered type I cytokine with established roles in infectious disease, autoimmunity, and cancer in a variety of organs. IL-27 was identified as a candidate gene for IBD, and a number of studies in mouse models of IBD have demonstrated that IL-27 therapy is protective. However, in contrast to these investigations, genetic deletion of the IL-27 receptor has been shown to be protective in some mouse models of IBD. The purpose of this review is to highlight the recent literature investigating the role of IL-27 in IBD and to discuss the possible explanations for the sometimes conflicting results of these studies. Evidence supporting IL-27 therapy as a treatment for IBD will also be discussed.

Blockade of interleukin-27 signaling reduces GVHD in mice by augmenting Treg reconstitution and stabilizing Foxp3 expression

Reestablishment of competent regulatory pathways has emerged as a strategy to reduce the severity of graft-versus-host disease (GVHD), and recalibrate the effector and regulatory arms of the immune system. However, clinically feasible, cost-effective strategies that do not require extensive ex vivo cellular manipulation have remained elusive. In the current study, we demonstrate that inhibition of the interleukin-27p28 (IL-27p28) signaling pathway through antibody blockade or genetic ablation prevented lethal GVHD in multiple murine transplant models. Moreover, protection from GVHD was attributable to augmented global reconstitution of CD4⁺ natural regulatory T cells (nTregs), CD4⁺ induced Tregs (iTregs), and CD8⁺ iTregs, and was more potent than temporally concordant blockade of IL-6 signaling. Inhibition of IL-27p28 also enhanced the suppressive capacity of adoptively transferred CD4⁺ nTregs by increasing the stability of Foxp3 expression. Notably, blockade of IL-27p28 signaling reduced T-cell-derived-IL-10 production in conventional T cells; however, there was no corresponding effect in CD4⁺ or CD8⁺ Tregs, indicating that IL-27 inhibition had differential effects on IL-10 production and preserved a mechanistic pathway by which Tregs are known to suppress GVHD. Targeting of IL-27 therefore represents a novel strategy for the in vivo expansion of Tregs and subsequent prevention of GVHD without the requirement for ex vivo cellular manipulation, and provides additional support for the critical proinflammatory role that members of the IL-6 and IL-12 cytokine families play in GVHD biology.

Systemic delivery of IL-27 by an adeno-associated viral vector inhibits T cell-mediated colitis and induces multiple inhibitory pathways in T cells

IL-27 is a heterodimeric cytokine that is composed of two subunits, i.e., EBV-induced gene 3 and IL-27p28 (also known as IL-30). Although the role of endogenous IL-27 in the pathogenesis of autoimmune colitis, an experimental model of human inflammatory bowel disease, remains controversial, IL-27 local delivery has been shown to inhibit autoimmune colitis. IL-30 has been shown to inhibit Th1 and Th17 responses and is considered a potential therapeutic for certain autoimmune diseases. In this study, we have compared the therapeutic efficacy of adeno-associated viral vector-delivered IL-27 and IL-30 in a murine model of autoimmune colitis. We found that 1 single administration of adeno-associated viral vector-delivered IL-27, but not adeno-associated viral vector-delivered IL-30, nearly completely inhibited autoimmune colitis. Adeno-associated viral vector-delivered IL-27 administration inhibited Th17 responses and induced T cell expression of IL-10, programmed death ligand 1, and stem cell antigen 1. Intriguingly, adeno-associated viral vector-delivered IL-27 treatment enhanced Th1 responses and inhibited regulatory T cell responses. Experiments involving the adoptive transfer of IL-10-deficient T cells revealed that adeno-associated viral vector-delivered IL-27-induced IL-10 production was insufficient to mediate inhibition of autoimmune colitis, whereas anti-programmed death 1 antibody treatment resulted in the breaking of adeno-associated viral vector-delivered IL-27-induced T cell tolerance. Thus, systemic delivery of IL-27 inhibits Th17 responses and induces multiple inhibitory pathways, including programmed death ligand 1 in T cells, and adeno-associated viral vector-delivered IL-27, but not IL-30, may have a therapeutic potential for the treatment of human inflammatory bowel disease.

Role of interleukin-27 in inflammatory bowel disease

Inflammatory bowel disease (IBD), which is characterized by chronic or recurrent relapsing gastrointestinal inflammation, includes ulcerative colitis (UC) and Crohn's disease (CD). The pathogenesis of IBD remains obscure, however, abnormal immune responses are regarded as the major component of IBD pathogenesis. Interleukin-27 (IL-27) is a new member of the IL-12 family, and it is produced by activated antigen-presenting cells and plays an important role in the differentiation and function of different T cell subsets. IL-27 has various immunoregulatory functions and is implicated in the pathogenesis of many infectious and autoimmune diseases. Recent studies have showed that IL-27 is strongly associated with the genesis and development of IBD. Here we provide an overview of the role of IL-27 in the pathogenesis of IBD.

The role of the cytokines IL-27 and IL-35 in cancer

The cancer-immune interaction is a fast growing field of research in biology, where the goal is to harness the immune system to fight cancer more effectively. In the present paper we review recent work of the interaction between T cells and cancer. CD8+ T cells are activated by IL-27 cytokine and they kill tumor cells. Regulatory T cells produce IL-35 which promotes cancer cells by enhancing angiogenesis, and inhibit CD8+ T cells via TGF-β production. Hence injections of IL-27 and anti-IL-35 are both potentially anti-tumor drugs. The models presented here are based on experimental mouse experiments, and their simulations agree with these experiments. The models are used to suggest effective schedules for drug treatment.

The Yin and Yang aspects of IL-27 in induction of cancer-specific T-cell responses and immunotherapy

Accumulating evidences from animal studies have indicated that both endogenous and exogenous IL-27, an IL-12 family of cytokine, can increase antitumor T-cell activities and inhibit tumor growth. IL-27 can modulate Treg responses, and program effector T cells into a unique T-effector stem cell (TSEC) phenotype, which enhances T-cell survival in the tumor microenvironment. However, animal studies also suggest that IL-27 induces molecular pathways such as IL-10, PD-L1 and CD39, which may downregulate tumor-specific T-cell responses. In this review paper, we will discuss the Yin and Yang aspects of IL-27 in the induction of tumor-specific T-cell responses, and the potential impacts of these functions of IL-27 in the design of cancer immunotherapy.

Elevated Circulating Levels of Inflammatory Markers in Patients with Acute Coronary Syndrome

Objective. We evaluated inflammatory cytokines and chemokine in peripheral blood mononuclear cells (PBMCs) in patients with either acute coronary syndrome (ACS) or stable coronary artery disease (CAD). Methods. We enrolled 20 ACS patients and 50 stable CAD patients without previous history of ACS who underwent cardiac catheterization. Patients with an estimated glomerular filtration rate of ≤30 mL/min/1.73 m(2) and C-reactive protein of ≥1.0 mg/dL were excluded. Blood samples were collected from the patients just before catheterization, and PBMCs were isolated from the whole blood. The levels of inflammatory cytokines and chemokine were measured by using real-time quantitative polymerase chain reaction and immunoassays. Results. The expression of tumor necrosis factor alpha (TNF-α), interleukin- (IL-) 6, IL-10, IL-23A, IL-27, and IL-37 was significantly higher in the ACS group than in the CAD group (P < 0.05). In contrast, the expression of IL-33 was significantly lower in the ACS group than in the CAD group (P < 0.05). The ACS patients had higher plasma levels of TNF-α, IL-6, and IL-10 in the ACS group than in the CAD group. Conclusion. Circulating levels of pro-/anti-inflammatory cytokines, including IL-23A, IL-27, IL-33, and IL-37, may be associated with the pathogenesis of atherosclerosis in ACS patients.

IL-Y, a synthetic member of the IL-12 cytokine family, suppresses the development of type 1 diabetes in NOD mice

The IL-12 family of heterodimeric cytokines, consisting of IL-12, IL-23, IL-27, and IL-35, has important roles in regulating the immune response. IL-12 family members are comprised of a heterodimer consisting of α and β chains: IL-12 (p40 and p35), IL-23 (p40 and p19), IL-27 (Ebi3 and p28), and IL-35 (Ebi3 and p35). Given the combinatorial nature of the IL-12 family, we generated adenoviral vectors expressing two putative IL-12 family members not yet found naturally, termed IL-X (Ebi3 and p19) and IL-Y (p40 and p28), as single-chain molecules. Single chain IL-Y (scIL-Y), but not scIL-X, was able to stimulate significantly a unique cytokine/chemokine expression profile as well as activate STAT3 in mice, in part, through a pathway involving IL-27Rα in splenocytes. Adenoviral-mediated, intratumoral delivery of scIL-Y increased tumor growth in contrast to the anti-tumor effects of scIL-12 and scIL-23. Similarly, treatment of prediabetic NOD mice by intravenous injection of Ad.scIL-Y prevented the onset of hyperglycemia. Analysis of cells from Ad.scIL-Y-treated NOD mice demonstrated that scIL-Y reduced expression of inflammatory mediators such as IFN-γ. Our data demonstrate that a novel, synthetic member of the IL-12 family, termed IL-Y, confers unique immunosuppressive effects in two different disease models and thus could have therapeutic applications.

Helios Enhances Treg Cell Function in Cooperation With FoxP3

OBJECTIVE

Helios+FoxP3+CD4+ (Helios+) Treg cells are believed to be involved in the regulation of various autoimmune diseases; however, the regulatory mechanisms underlying the development of Helios+ Treg cells remain uncertain. This study was undertaken to elucidate the regulatory mechanisms of Helios expression in CD4+ T cells and its roles in transforming growth factor β (TGFβ)-induced Treg cell function.

METHODS

We examined the expression of Helios in CD4+ T cells in patients with rheumatoid arthritis by DNA microarray analysis before and after treatment with biologic agents. We also examined the effect of interleukin-6 (IL-6) and TGFβ on Helios expression in CD4+ T cells in humans and mice. The effect of forced expression of Helios on murine induced Treg cell function was also examined. The role of FoxP3 in the induction and function of Helios was assessed by using CD4+ T cells from FoxP3-deficient scurfy mice.

RESULTS

Tocilizumab, but not tumor necrosis factor (TNF) inhibitors or abatacept, increased Helios expression in CD4+ T cells in patients with a good response. IL-6 inhibited the TGFβ-induced development of Helios+ induced Treg cells in both humans and mice. Both cell-intrinsic FoxP3 expression and TGFβ signaling were required for Helios induction in murine induced Treg cells. The forced expression of Helios enhanced the expression of various Treg cell-related molecules and the suppressive function in murine induced Treg cells. Helios-mediated enhancement of the suppressive function of induced Treg cells was obvious in FoxP3-sufficient CD4+ T cells but not in FoxP3-deficient CD4+ T cells.

CONCLUSION

Our findings indicate that Helios enhances induced Treg cell function in cooperation with FoxP3.

Potential clinical application of interleukin-27 as an antitumor agent

Cancer immunotherapies such as sipuleucel-T and ipilimumab are promising new treatments that harness the power of the immune system to fight cancer and achieve long-lasting remission. Interleukin (IL)-27, a member of the IL-12 heterodimeric cytokine family, has pleiotropic functions in the regulation of immune responses with both pro-inflammatory and anti-inflammatory properties. Evidence obtained using a variety of preclinical mouse models indicates that IL-27 possesses potent antitumor activity against various types of tumors through multiple mechanisms without apparent adverse effects. These mechanisms include those mediated not only by CD8⁺ T cells, natural killer cells and macrophages, but also by antibody-dependent cell-mediated cytotoxicity, antiangiogenesis, direct antiproliferative effects, inhibition of expression of cyclooxygenase-2 and prostaglandin E₂, and suppression of epithelial–mesenchymal transition, depending on the characteristics of individual tumors. However, the endogenous role of IL-27 subunits and one of its receptor subunits, WSX-1, in the susceptibility to tumor development after transplantation of tumor cell lines or endogenously arising tumors seems to be more complicated. IL-27 functions as a double-edged sword: IL-27 increases IL-10 production and the expression of programmed death ligand 1 and T-cell immunoglobulin and mucin domain-3, and promotes the generation of regulatory T cells, and IL-27 receptor α singling enhances transformation; IL-27 may augment protumor effects as well. Here, we review both facets of IL-27, antitumor effects and protumor effects, and discuss the potential clinical application of IL-27 as an antitumor agent.

Potent therapeutic target of inflammation, virus and tumor: focus on interleukin-27

Interleukin (IL)-27 is an important pleiotropic immunological regulator for having dual effects on the immune responses. Several distinct findings have been highlighted that in certain conditions, neutralizing IL-27 or its subunit IL-27p28 might be a useful strategy to limit inflammation. Recently more insights have revealed that IL-27 could also exert potent inhibitory functions in some other immune circumstances including virus infection and tumor immunity. In this review, we describe IL-27 receptor subunits and the mechanisms of individual IL-27, and summarize the advances of their preclinical application trials. In addition, the potential role of IL-27 as a clinical therapeutic target will also be discussed.

Interleukin-27 in T cell immunity

Interleukin (IL)-27, a member of IL-12/IL-23 heterodimeric family of cytokines, has pleiotropic properties that can enhance or limit immune responses. IL-27 acts on various cell types, including T cells, B cells, macrophages, dendritic cells, natural killer (NK) cells and non-hematopoietic cells. Intensive studies have been conducted especially on T cells, revealing that various subsets of T cells respond uniquely to IL-27. IL-27 induces expansion of Th1 cells by activating signal transducer and activator of transcription (STAT) 1-mediated T-bet signaling pathway. On the other hand, IL-27 suppresses immune responses through inhibition of the development of T helper (Th) 17 cells and induction of IL-10 production in a STAT1- and STAT3-dependent manner. IL-27 is a potentially promising cytokine for therapeutic approaches on various human diseases. Here, we provide an overview of the biology of IL-27 related to T cell subsets, its structure, and production mechanism.

Epstein-Barr virus-induced gene 3-deficiency leads to impaired antitumor T-cell responses and accelerated tumor growth

Epstein-Barr virus-induced gene 3 (EBI3) encoded protein can form heterodimers with IL-27P28, and IL-12P35 to form IL-27, and IL-35. However, IL-27 stimulates, whereas IL-35 inhibits antitumor T-cell responses. IL-27 also limits the Foxp3⁺ regulatory T cell (Treg) population, whereas IL-35 has been shown to expand Tregs and foster Treg suppressive functions. It remains unclear which group of forces are dominant during antitumor T-cell responses. In this study, we evaluated the tumor growth and antitumor T-cell responses in EBI3-deficient mice that lack both IL-27 and IL-35. We found that injecting B16 melanoma cells into EBI3-deficient C57BL/6 mice, or J558 plasmacytoma cells into EBI3-deficient BALB/c mice resulted in significantly increased tumor growth relative to those implanted in wild-type control mice. Tumors from EBI3-deficient mice contained significantly decreased proportions of CD8⁺ T cells and increased proportions of CD4⁺FoxP3⁺ Treg cells as compared to those from EBI3-intact mice. Tumor-infiltrating T cells from EBI3-deficient mice were impaired in their capacity to produce IFNγ. Phenotypically, Tregs from EBI3-deficient mice were highly suppressive and produced IL-10 in the tumor microenvironment. Depletion of Tregs or inactivation of the IL-10 pathway significantly abrogated tumor growth enhancement in Ebi3^-/- mice. Finally, we showed that Ebi3^-/- mice administered a melanoma vaccine failed to mount a CD8⁺ T-cell response and the vaccine failed to confer tumor rejection in EBI3-deficient mice. Taken together, these results suggest that Ebi3^-/- mice show a phenotype of IL-27-deficiency rather than IL-35-deficiency during anti-tumor T-cell responses. Thus, our results suggest that endogenous IL-27 is critical for both spontaneous and vaccine-induced antitumor T-cell responses.

IL-27 limits central nervous system viral clearance by promoting IL-10 and enhances demyelination

IL-27 is a pleiotropic member of the IL-6 and IL-12 cytokine family composed of the IL-27p28 and the EBV-induced gene 3. IL-27 and its receptor mRNA are both upregulated in the CNS during acute encephalomyelitis induced by the JHM strain of mouse hepatitis virus (JHMV) and sustained during viral persistence. Contributions of IL-27 to viral pathogenesis were evaluated by infection of IL-27Rα-chain-deficient (IL-27Rα(-/-)) mice. The absence of IL-27 signaling accelerated virus control within the CNS associated with increased IFN-γ secreting virus-specific CD4+ and CD8+ T cells. Abrogation of IL-27 signaling did not affect virus-specific CD8+ T cell-mediated IL-10 production or cytolytic activity or Foxp3+ regulatory T cell populations. However, IL-10 production by virus-specific CD4+ T cells was reduced significantly. Despite increased T cell-mediated antiviral function in IL-27Rα(-/-) mice, the virus persisted in the CNS at similar levels as in wild-type mice. Nevertheless, IL-27Rα(-/-) mice exhibited decreased clinical disease during persistence, coincident with less severe demyelination, the hallmark tissue damage associated with JHMV infection. Overall, these data demonstrate that in contrast to viral infections at other sites, IL-27 does not play a proinflammatory role during JHMV-induced encephalomyelitis. Rather, it limits CNS inflammation and impairs control of CNS virus replication via induction of IL-10 in virus-specific CD4+ T cells. Furthermore, in contrast to its protective role in limiting CNS autoimmunity and preventing immunopathology, these data define a detrimental role of IL-27 in promoting demyelination by delaying viral control.

Homeostasis and function of regulatory T cells (Tregs) in vivo: lessons from TCR-transgenic Tregs

The identification of CD25 and subsequently Forkhead box protein 3 (Foxp3) as markers for regulatory T cells (Tregs) has revolutionized our ability to explore this population experimentally. In a similar vein, our understanding of antigen-specific Treg responses in vivo owes much to the fortuitous generation of T-cell receptor (TCR)-transgenic Tregs. This has permitted tracking of Tregs with a defined specificity in vivo, facilitating analysis of how encounter with cognate antigen shapes Treg homeostasis and function. Here, we review the key lessons learned from a decade of analysis of TCR-transgenic Tregs and set this in the broader context of general progress in the field. Use of TCR-transgenic Tregs has led to an appreciation that Tregs are a highly dynamic proliferative population in vivo, rather than an anergic population as they were initially portrayed. It is now clear that Treg homeostasis is positively regulated by encounter with self-antigen expressed on peripheral tissues, which is likely to be relevant to the phenomenon of peripheral repertoire reshaping that has been described for Tregs and the observation that the Treg TCR specificities vary by anatomical location. Substantial evidence has also accumulated to support the role of CD28 costimulation and interleukin-2 in Treg homeostasis. The availability of TCR-transgenic Tregs has enabled analysis of Treg populations that are sufficient or deficient in particular genes, without the comparison being confounded by repertoire alterations. This approach has yielded insights into genes required for Treg function in vivo, with particular progress being made on the role of ctla-4 in this context. As the prospect of manipulating Treg populations in the clinic becomes reality, a full appreciation of the rules governing their homeostasis will prove increasingly important.

IL-27p28 is essential for parent-to-F1 acute graft-versus-host disease

Acute graft versus host disease (aGVHD) remains a life-threatening complication of bone marrow transplantation. Here we show that IL-27, a member of the IL-12 cytokine family, plays an essential role in a parent-to-F1 murine aGVHD model, using B6 mice as parents and B6D2 mice as F1 recipients. IL-27 is transiently detectable in the serum of B6D2 recipients of B6 spleen cells, with a peak at day 10. Treatment with anti-IL-27p28 mAb MM27.7B1 (αp28Ab), at the time of and six days after B6 cell transfer, blocked GVHD. Protection was associated with host cell survival and undiminished engraftment of donor cells, lack of host B-cell depletion, increased Th2-type immunoglobulin production, a decrease in serum IFN-γ, a drop in anti-H-2D(d) cytotoxic T lymphocyte activity and an increase in Foxp3(+) T cells. We therefore conclude that IL-27 plays a critical role in the parent-to-F1 model of aGVHD and that blocking IL-27 could have therapeutic relevance.

IL-27R-mediated regulation of IL-17 controls the development of respiratory syncytial virus-associated pathogenesis

IL-27 is a heterodimeric cytokine composed of the subunits p28 and Epstein-Barr virus induced gene (EBI)-3 and is known for its effects on T-cell function and differentiation. IL-27 signals through the widely expressed IL-27 receptor (IL-27R), composed of the ligand-specific IL-27Rα chain and gp130. Engagement of the IL-27R activates STAT1 signaling, induces the expression of the type 1 helper T-cell (Th1) cytokine, interferon γ, and suppresses the differentiation of Th2 and Th17 cells. This study investigates the role of IL-27 signaling in respiratory syncytial virus (RSV) infection using IL-27Rα-deficient mice (IL-27rKO). Analysis of lungs from RSV-infected IL-27rKO mice showed exacerbation of mucus secretion compared with wild type, as well as enhanced expression of Muc5ac and Gob5 mRNA, markers of goblet cell metaplasia/hyperplasia. When compared with wild-type mice, RSV-challenged IL-27rKO mice had enhanced expression of Th17-associated cytokine IL-17a and an imbalance between Th1 and Th2 cytokine levels. Neutralization of IL-17 in RSV-infected IL-27rKO mice resulted in a significant decrease in the pulmonary mucus response and inhibition of the Th2-associated cytokines. Interestingly, IL-17 blockage led to an increase in the expression of IL-27 subunits p28 and EBI-3 in the lungs and lymph nodes of RSV-infected mice. Thus, IL-27 functions as a regulatory cytokine during RSV pathogenesis by suppressing the development of Th17 cells, but it also appears to be regulated by IL-17 induced by the virus.

Mathematical modeling of interleukin-27 induction of anti-tumor T cells response

Interleukin-12 is a pro-inflammatory cytokine which promotes Th1 and cytotoxic T lymphocyte activities, such as Interferon- secretion. For this reason Interleukin-12 could be a powerful therapeutic agent for cancer treatment. However, Interleukin-12 is also excessively toxic. Interleukin-27 is an immunoregulatory cytokine from the Interleukin-12 family, but it is not as toxic as Interleukin-12. In recent years, Interleukin-27 has been considered as a potential anti-tumor agent. Recent experiments in vitro and in vivo have shown that cancer cells transfected with IL-27 activate CD8⁺ T cells to promote the secretion of anti-tumor cytokines Interleukin-10, although, at the same time, IL-27 inhibits the secretion of Interferon- by CD8⁺ T cells. In the present paper we develop a mathematical model based on these experimental results. The model involves a dynamic network which includes tumor cells, CD8⁺ T cells and cytokines Interleukin-27, Interleukin-10 and Interferon-. Simulations of the model show how Interleukin-27 promotes CD8⁺ T cells to secrete Interleukin-10 to inhibit tumor growth. On the other hand Interleukin-27 inhibits the secretion of Interferon- by CD8⁺ T cells which somewhat diminishes the inhibition of tumor growth. Our numerical results are in qualitative agreement with experimental data. We use the model to design protocols of IL-27 injections for the treatment of cancer and find that, for some special types of cancer, with a fixed total amount of drug, within a certain range, continuous injection has better efficacy than intermittent injections in reducing the tumor load while the treatment is ongoing, although the decrease in tumor load is only temporary.

IL-27 in human secondary lymphoid organs attracts myeloid dendritic cells and impairs HLA class I-restricted antigen presentation

Different cytokines play crucial roles in inflammation and in polarizing immune responses, including IL-27 that exerts pro- and anti-inflammatory functions. Although the activity of IL-27 is well characterized in murine immune cells, only limited information is available regarding the natural cellular sources of IL-27 in humans and its effects on human immune cells. Dendritic cells (DCs) are the most potent professional APCs that in the immature state are positioned throughout peripheral tissues by acting as sentinels, sensing the presence of Ags. Activated DCs migrate into the lymph nodes and direct Ag-specific T cell responses, thus acting as key players in both adaptive and innate immunity. In this study we asked whether IL-27 is produced by human secondary lymphoid organs and what is its functional role on human DCs. To our knowledge, we provide the first evidence that 1) in lymph nodes, macrophages are the major source for IL-27; 2) immature and mature human DCs express functional IL-27R; 3) IL-27 exerts immunosuppressive activity by crippling the Ag processing machinery in immature DCs under steady-state conditions and after pulsing with a viral Ag; and 4) IL-27 is chemotactic for human DCs. Our findings highlight novel mechanisms underlying the immunosuppressive activity of IL-27, suggesting that this cytokine may function as a homeostatic cytokine in secondary lymphoid organs by limiting duration and/or intensity of ongoing adaptive immune responses. The results presented in this study pave the way to future studies aimed at investigating whether dysregulation of IL-27 expression and function may be involved in pathogenesis of autoimmune disease and cancer.

Homeostatic control of regulatory T cell diversity

Regulatory T (TReg) cells constitute an essential counterbalance to adaptive immune responses. Failure to maintain appropriate TReg cell numbers or function leads to autoimmune, malignant and immunodeficient conditions. Dynamic homeostatic processes preserve the number of forkhead box P3-expressing (FOXP3(+)) TReg cells within a healthy range, with high rates of cell division being offset by apoptosis under steady-state conditions. Recent studies have shown that TReg cells become specialized for different environmental contexts, tailoring their functions and homeostatic properties to a wide range of tissues and immune conditions. In this Review, we describe new insights into the molecular controls that maintain the steady-state homeostasis of TReg cells and the cues that drive TReg cell adaptation to inflammation and/or different locations. We highlight how differing local milieu might drive context-specific TReg cell function and restoration of immune homeostasis, and how dysregulation of these processes can precipitate disease.