Modulation of human plasmacytoid DC function by IFN-lambda1 (IL-29)

Interferon lambda in respiratory viral infection: immunomodulatory functions and antiviral effects in epithelium

Type III interferon (IFN-λ), a new member of the IFN family, was initially considered to possess antiviral functions similar to those of type I interferon, both of which are induced via the JAK/STAT pathway. Nevertheless, recent findings demonstrated that IFN-λ exerts a nonredundant antiviral function at the mucosal surface, preferentially produced in epithelial cells in contrast to type I interferon, and its function cannot be replaced by type I interferon. This review summarizes recent studies showing that IFN-λ inhibits the spread of viruses from the cell surface to the body. Further studies have found that the role of IFN-λ is not only limited to the abovementioned functions, but it can also can exert direct and/or indirect effects on immune cells in virus-induced inflammation. This review focuses on the antiviral activity of IFN-λ in the mucosal epithelial cells and its action on immune cells and summarizes the pathways by which IFN-λ exerts its action and differentiates it from other interferons in terms of mechanism. Finally, we conclude that IFN-λ is a potent epidermal antiviral factor that enhances the respiratory mucosal immune response and has excellent therapeutic potential in combating respiratory viral infections.

Bestatin, A Pluripotent Immunomodulatory Small Molecule, Drives Robust and Long-Lasting Immune Responses as an Adjuvant in Viral Vaccines

An inactivated whole-virus vaccine is currently used to prevent foot-and-mouth disease (FMD). Although this vaccine is effective, it offers short-term immunity that requires regular booster immunizations and has several side effects, including local reactions at the vaccination site. To address these limitations, herein, we evaluated the efficacy of bestatin as a novel small molecule adjuvant for inactivated FMD vaccines. Our findings showed that the FMD vaccine formulated with bestatin enhanced early, intermediate-, and particularly long-term immunity in experimental animals (mice) and target animals (pigs). Furthermore, cytokines (interferon (IFN)α, IFNβ, IFNγ, and interleukin (IL)-29), retinoic acid-inducible gene (RIG)-I, and T-cell and B-cell core receptors (cluster of differentiation (CD)28, CD19, CD21, and CD81) markedly increased in the group that received the FMD vaccine adjuvanted with bestatin in pigs compared with the control. These results indicate the significant potential of bestatin to improve the efficacy of inactivated FMD vaccines in terms of immunomodulatory function for the simultaneous induction of potent cellular and humoral immune response and a long-lasting memory response.

Characterization of Monoclonal Antibodies to Measure Cell Surface Protein Levels of Human Interferon-Lambda Receptor 1

Type III interferons (IFN-lambdas, IFN-λs) are important antiviral cytokines that can also modulate immune responses by acting through a heterodimeric receptor composed of the specific and limited expressed IFN-λR1 chain and the ubiquitous IL-10R2 chain, which is shared with IL-10 family cytokines. Conflicting data have been reported regarding which cells express the IFN-λR1 subunit and directly respond to IFN-λs. This is, in part, owing to transcript levels of the IFN-λR1 gene, IFNLR1, not always correlating with cell surface protein levels. In this study, we tested a panel of novel monoclonal antibodies (mAbs) that specifically recognize human IFN-λR1. Initially, antigen specificity was confirmed by enzyme-linked immunosorbent assay (ELISA), from which a subset of antibodies was selected for additional flow cytometry and neutralization assays. We further characterized two antibodies based on their strong ELISA binding activity (HLR1 and HLR14) and found only HLR14 could reliably detect cell surface IFN-λR1 protein on a variety of cell lines by flow cytometry. HLR14 could also detect IFN-λR1 protein on certain primary human blood cells, including plasmacytoid dendritic cells and B cells from peripheral blood. Availability of the HLR14 mAb will enable the quantification of IFN-λR1 protein levels on cells and better characterization of the cell specificity of the IFN-λ response.

The role of antigen-presenting cells in the pathogenesis of COVID-19

Coronavirus Disease 2019 (COVID-19) is one of the three lethal coronavirus outbreaks in the recent two decades and a serious threat to global health all over the world. The principal feature of the COVID-19 infection is the so-called "cytokine storm" exaggerated molecular response to virus distribution, which plays massive tissue and organ injury roles. Immunological treatments, including monoclonal antibodies and vaccines, have been suggested as the main approaches in treating and preventing this disease. Therefore, a proper investigation of the roles of antigen-presenting cells (APCs) in the aforementioned immunological responses appears essential. The present review will provide detailed information about APCs' role in the infection and pathogenesis of SARS-CoV-2 and the effect of monoclonal antibodies in diagnosis and treatment.

Regulation and Function of Interferon-Lambda (IFNλ) and Its Receptor in Asthma

Asthma is a chronic respiratory disease affecting people of all ages, especially children, worldwide. Origins of asthma are suggested to be placed in early life with heterogeneous clinical presentation, severity and pathophysiology. Exacerbations of asthma disease can be triggered by many factors, including viral respiratory tract infections. Rhinovirus (RV) induced respiratory infections are the predominant cause of the common cold and also play a crucial role in asthma development and exacerbations. Rhinovirus mainly replicates in epithelial cells lining the upper and lower respiratory tract. Type III interferons, also known as interferon-lambda (IFNλ), are potent immune mediators of resolution of infectious diseases but they are known to be involved in autoimmune diseases as well. The protective role of type III IFNs in antiviral, antibacterial, antifungal and antiprotozoal functions is of major importance for our innate immune system. The IFNλ receptor (IFNλR) is expressed in selected types of cells like epithelial cells, thus orchestrating a specific immune response at the site of viruses and bacteria entry into the body. In asthma, IFNλ restricts the development of TH2 cells, which are induced in the airways of asthmatic patients. Several studies described type III IFNs as the predominant type of interferon increased after infection caused by respiratory viruses. It efficiently reduces viral replication, viral spread into the lungs and viral transmission from infected to naive individuals. Several reports showed that bronchial epithelial cells from asthmatic subjects have a deficient response of type III interferon after RV infection ex vivo. Toll like Receptors (TLRs) recognize pathogen-associated molecular patterns (PAMPs) expressed on infectious agents, and induce the development of antiviral and antibacterial immunity. We recently discovered that activation of TLR7/8 resulted in enhanced IFNλ receptor mRNA expression in PBMCs of healthy and asthmatic children, opening new therapeutic frontiers for rhinovirus-induced asthma. This article reviews the recent advances of the literature on the regulated expression of type III Interferons and their receptor in association with rhinovirus infection in asthmatic subjects.

Monocytes differentiated into macrophages and dendritic cells in the presence of human IFN-λ3 or IFN-λ4 show distinct phenotypes

Human IFN-λ4 is expressed by only a subset of individuals who possess the ΔG variant allele at the dinucleotide polymorphism rs368234815. Recent genetic studies have shown an association between rs368234815 and different infectious and inflammatory disorders. It is not known if IFN-λ4 has immunomodulatory activity. The expression of another type III IFN, IFN-λ3, is also controlled by genetic polymorphisms that are strongly linked to rs368234815. Therefore, it is of interest to compare these two IFNs for their effects on immune cells. Herein, using THP-1 cells, it was confirmed that IFN-λ4 could affect the differentiation status of macrophage-like cells and dendritic cells (DCs). The global gene expression changes induced by IFN-λ4 were also characterized in in vitro generated primary macrophages. Next, human PBMC-derived CD14+ monocytes were used to obtain M1 and M2 macrophages and DCs in the presence of IFN-λ3 or IFN-λ4. These DCs were cocultured with CD4+ Th cells derived from allogenic donors and their in vitro cytokine responses were measured. The specific activity of recombinant IFN-λ4 was much lower than that of IFN-λ3, as shown by induction of IFN-stimulated genes. M1 macrophages differentiated in the presence of IFN-λ4 showed higher IL-10 secretion than those differentiated in IFN-λ3. Coculture experiments suggested that IFN-λ4 could confer a Th2-biased phenotype to allogenic Th cells, wherein IFN-λ3, under similar circumstances, did not induce a significant bias toward either a Th1 or Th2 phenotype. This study shows for the first time that IFN-λ4 may influence immune responses by immunomodulation.

Herpesviruses and the Type III Interferon System

Type III interferons (IFNs) represent the most recently discovered group of IFNs. Together with type I IFNs (e.g. IFN-α/β), type III IFNs (IFN-λ) are produced as part of the innate immune response to virus infection, and elicit an anti-viral state by inducing expression of interferon stimulated genes (ISGs). It was initially thought that type I IFNs and type III IFNs perform largely redundant functions. However, it has become evident that type III IFNs particularly play a major role in antiviral protection of mucosal epithelial barriers, thereby serving an important role in the first-line defense against virus infection and invasion at contact areas with the outside world, versus the generally more broad, potent and systemic antiviral effects of type I IFNs. Herpesviruseses are large DNA viruses, which enter their host via mucosal surfaces and establish lifelong, latent infections. Despite the importance of mucosal epithelial cells in the pathogenesis of herpesviruses, our current knowledge on the interaction of herpesviruses with type III IFN is limited and largely restricted to studies on the alphaherpesvirus herpes simplex virus (HSV). This review summarizes the current understanding about the role of IFN-λ in the immune response against herpesvirus infections.

Molecular and Structural Basis of DNA Sensors in Antiviral Innate Immunity

DNA viruses are a source of great morbidity and mortality throughout the world by causing many diseases; thus, we need substantial knowledge regarding viral pathogenesis and the host’s antiviral immune responses to devise better preventive and therapeutic strategies. The innate immune system utilizes numerous germ-line encoded receptors called pattern-recognition receptors (PRRs) to detect various pathogen-associated molecular patterns (PAMPs) such as viral nucleic acids, ultimately resulting in antiviral immune responses in the form of proinflammatory cytokines and type I interferons. The immune-stimulatory role of DNA is known for a long time; however, DNA sensing ability of the innate immune system was unraveled only recently. At present, multiple DNA sensors have been proposed, and most of them use STING as a key adaptor protein to exert antiviral immune responses. In this review, we aim to provide molecular and structural underpinnings on endosomal DNA sensor Toll-like receptor 9 (TLR9) and multiple cytosolic DNA sensors including cyclic GMP-AMP synthase (cGAS), interferon-gamma inducible 16 (IFI16), absent in melanoma 2 (AIM2), and DNA-dependent activator of IRFs (DAI) to provide new insights on their signaling mechanisms and physiological relevance. We have also addressed less well-understood DNA sensors such as DEAD-box helicase DDX41, RNA polymerase III (RNA pol III), DNA-dependent protein kinase (DNA-PK), and meiotic recombination 11 homolog A (MRE11). By comprehensive understanding of molecular and structural aspects of DNA-sensing antiviral innate immune signaling pathways, potential new targets for viral and autoimmune diseases can be identified.

BDCA1+ cDC2s, BDCA2+ pDCs and BDCA3+ cDC1s reveal distinct pathophysiologic features and impact on clinical outcomes in melanoma patients

Objectives

Dendritic cells play a pivotal but still enigmatic role in the control of tumor development. Composed of specialised subsets (cDC1s, cDC2s, pDCs), DCs are critical in triggering and shaping antitumor immune responses. Yet, tumors exploit plasticity of DCs to subvert their functions and escape from immune control. This challenging controversy prompted us to explore the pathophysiological role of cDCs and pDCs in melanoma, where their precise and coordinated involvement remains to be deciphered.

Methods

We investigated in melanoma patients the phenotypic and functional features of circulating and tumor‐infiltrating BDCA1⁺ cDC2s, BDCA2⁺ pDCs and BDCA3⁺ cDC1s and assessed their clinical impact.

Results

Principal component analyses (PCA) based on phenotypic or functional parameters of DC subsets revealed intra‐group clustering, highlighting specific features of DCs in blood and tumor infiltrate of patients compared to healthy donors. DC subsets exhibited perturbed frequencies in the circulation and actively infiltrated the tumor site, while harbouring a higher activation status. Whereas cDC2s and pDCs displayed an altered functionality in response to TLR triggering, circulating and tumor‐infiltrating cDC1s preserved potent competences associated with improved prognosis. Notably, the proportion of circulating cDC1s predicted the clinical outcome of melanoma patients.

Conclusion

Such understanding uncovers critical and distinct impact of each DC subset on clinical outcomes and unveils fine‐tuning of interconnections between DCs in melanoma. Elucidating the mechanisms of DC subversion by tumors could help designing new therapeutic strategies exploiting the potentialities of these powerful immune players and their cross‐talks, while counteracting their skewing by tumors, to achieve immune control and clinical success.

Protective Potentials of Type III Interferons in COVID-19 Patients: Lessons from Differential Properties of Type I- and III Interferons

While an appropriately regulated production of interferons (IFNs) performs a fundamental role in the defense against coronaviruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), dysregulated overproduction of inflammatory mediators can play an important role in the development of SARS-CoV-2 infection-related complications, such as acute respiratory distress syndrome. As the principal constituents of innate immunity, both type I and III IFNs share antiviral features. However, important properties, including preferential expression at mucosal barriers (such as respiratory tract), local influences, lower receptor distribution, smaller target cell types, noninflammatory effects, and immunomodulatory impacts, were attributed only to type III IFNs. Accordingly, type III IFNs can establish an optimal effective antiviral response, without triggering exaggerated systemic inflammation that is generally attributed to the type I IFNs. However, some harmful effects were attributed to the III IFNs and there are also major differences between human and mouse concerning the immunomodulatory effects of III IFNs. Here, we describe the differential properties of type I and type III IFNs and present a model of IFN response during SARS-COV-2 infection, while highlighting the superior potential of type III IFNs in COVID-19.

Immune response in SARS-CoV-2 infection: the role of interferons type I and type III

BACKGROUND

There is scarce information on the human immune response to the SARS-CoV-2 infection, and on the exacerbated inflammatory reaction observed in severe COVID-19 cases.

OBJECTIVE

To review the available evidence on the role of interferons type I and type III to SARS-CoV-2 infection.

METHODS

We reviewed the available published evidence on the role of immune response to SARS-CoV-2 infection as well as recent publications on characteristics and outcomes of COVID-19, and their relationship with interferons type I and type III.

RESULTS

The available data indicates that immune response plays an important role in controlling SARS-CoV-2 infection and the immune dysregulation can significantly modify the clinical outcomes of affected patients. In addition, the evidence suggests that IFN type I and III can play an important role in controlling viremia and modulating the immune response in COVID-19.

CONCLUSIONS

Due to their central role in immune response against SARS-CoV-2 infection, IFN type I and III could be considered for treatment of COVID-19.

The pros and cons of interferons for oncolytic virotherapy

Interferons (IFN) are potent immune stimulators that play key roles in both innate and adaptive immune responses. They are considered the first line of defense against viral pathogens and can even be used as treatments to boost the immune system. While viruses are usually seen as a threat to the host, an emerging class of cancer therapeutics exploits the natural capacity of some viruses to directly infect and kill cancer cells. The cancer-specificity of these bio-therapeutics, called oncolytic viruses (OVs), often relies on defective IFN responses that are frequently observed in cancer cells, therefore increasing their vulnerability to viruses compared to healthy cells. To ensure the safety of the therapy, many OVs have been engineered to further activate the IFN response. As a consequence of this IFN over-stimulation, the virus is cleared faster by the immune system, which limits direct oncolysis. Importantly, the therapeutic activity of OVs also relies on their capacity to trigger anti-tumor immunity and IFNs are key players in this aspect. Here, we review the complex cancer-virus-anti-tumor immunity interplay and discuss the diverse functions of IFNs for each of these processes.

Dendritic cells-derived interferon-λ1 ameliorated inflammatory bone destruction through inhibiting osteoclastogenesis

Bone infection contributing to inflammatory osteolysis is common in orthopedic surgery. The dynamic balance between bone formation and bone resorption is destroyed due to excessive osteoclast fusion and differentiation, which results in severe bone matrix loss. Many therapeutic approaches that restrain osteoclast formation and function act as efficient ways to prevent inflammatory bone erosion. We have demonstrated for the first time that dendritic cells-derived interferon-λ1 (IFN-λ1) inhibited inflammatory bone destruction in vivo and explored its underlying mechanisms on osteoclast formation in vitro. We found that IFN-λ1 was highly expressed in infectious bone tissue compared with that of non-infectious bone tissue. Additionally, dendritic cells marker genes such as CD80, CD86, and CD1a were higher expressed in infectious bone tissue than that of non-infectious bone tissue. Dendritic cells that were pretreated with LPS showed high expression of IFN-λ1. Moreover, conditioned medium of LPS-pretreated dendritic cells significantly inhibited osteoclast differentiation, as determined by TRAP staining assay. This suppressive effect was reversed by adding an IFN-λ1 monoclonal antibody. It was also investigated whether exogenous IFN-λ1 restrained osteoclastogenesis, bone resorption, F-actin ring formation, osteoclast-specific gene expression, release of pro-inflammatory cytokines, and translocation of p65 and NFATc1 by preventing the NF-κB signaling pathway and NLRP3 inflammasome formation, as well as by inducing the JAK-STAT signaling pathways in vitro. In vivo study indicated that IFN-λ1 prevents lipopolysaccharide (LPS)-induced inflammatory bone destruction by inhibiting excessive osteoclast fusion and bone resorption activity. In conclusion, our findings confirmed that dendritic cells-derived IFN-λ1 could attenuate osteoclast formation and bone resorptive activity in vitro and in vivo. These novel findings pave the way for the use of exogenous IFN-λ1 as a potential therapeutic treatment for excessive osteoclast-related diseases, such as inflammatory osteolysis, by regulating osteoclastogenesis to maintain the dynamic balance between bone formation and bone resorption.

Plasmacytoid dendritic cell biology and its role in immune-mediated diseases

Plasmacytoid dendritic cells (pDCs) are a unique subset of dendritic cells specialised in secreting high levels of type I interferons. pDCs play a crucial role in antiviral immunity and have been implicated in the initiation and development of many autoimmune and inflammatory diseases. This review summarises the latest advances in recent years in several aspects of pDC biology, with special focus on pDC heterogeneity, pDC development via the lymphoid pathway, and newly identified proteins/pathways involved in pDC trafficking, nucleic acid sensing and interferon production. Finally, we also highlight the current understanding of pDC involvement in autoimmunity and alloreactivity, and opportunities for pDC‐targeting therapies in these diseases. These new insights have contributed to answers to several fundamental questions remaining in pDC biology and may pave the way to successful pDC‐targeting therapy in the future.

Differential expression of interferon-lambda receptor 1 splice variants determines the magnitude of the antiviral response induced by interferon-lambda 3 in human immune cells

Type III interferons (IFN-lambdas(λ)) are important cytokines that inhibit viruses and modulate immune responses by acting through a unique IFN-λR1/IL-10RB heterodimeric receptor. Until now, the primary antiviral function of IFN-λs has been proposed to be at anatomical barrier sites. Here, we examine the regulation of IFN-λR1 expression and measure the downstream effects of IFN-λ3 stimulation in primary human blood immune cells, compared with lung or liver epithelial cells. IFN-λ3 directly bound and upregulated IFN-stimulated gene (ISG) expression in freshly purified human B cells and CD8+ T cells, but not monocytes, neutrophils, natural killer cells, and CD4+ T cells. Despite similar IFNLR1 transcript levels in B cells and lung epithelial cells, lung epithelial cells bound more IFN-λ3, which resulted in a 50-fold greater ISG induction when compared to B cells. The reduced response of B cells could be explained by higher expression of the soluble variant of IFN-λR1 (sIFN-λR1), which significantly reduced ISG induction when added with IFN-λ3 to peripheral blood mononuclear cells or liver epithelial cells. T-cell receptor stimulation potently, and specifically, upregulated membrane-bound IFNLR1 expression in CD4+ T cells, leading to greater antiviral gene induction, and inhibition of human immunodeficiency virus type 1 infection. Collectively, our data demonstrate IFN-λ3 directly interacts with the human adaptive immune system, unlike what has been previously shown in published mouse models, and that type III IFNs could be potentially utilized to suppress both mucosal and blood-borne viral infections.

Human Plasmacytoid Dendritic Cells and Cutaneous Melanoma

The prognosis of metastatic melanoma (MM) patients has remained poor for a long time. However, the recent introduction of effective target therapies (BRAF and MEK inhibitors for BRAFV600-mutated MM) and immunotherapies (anti-CTLA-4 and anti-PD-1) has significantly improved the survival of MM patients. Notably, all these responses are highly dependent on the fitness of the host immune system, including the innate compartment. Among immune cells involved in cancer immunity, properly activated plasmacytoid dendritic cells (pDCs) exert an important role, bridging the innate and adaptive immune responses and directly eliminating cancer cells. A distinctive feature of pDCs is the production of high amount of type I Interferon (I-IFN), through the Toll-like receptor (TLR) 7 and 9 signaling pathway activation. However, published data indicate that melanoma-associated escape mechanisms are in place to hijack pDC functions. We have recently reported that pDC recruitment is recurrent in the early phases of melanoma, but the entire pDC compartment collapses over melanoma progression. Here, we summarize recent advances on pDC biology and function within the context of melanoma immunity.

Insights into IL-29: Emerging role in inflammatory autoimmune diseases

Interleukin-29 (IL-29) is a newly discovered member of type III interferon. It mediates signal transduction via binding to its receptor complex and activates downstream signalling pathways, and therefore induces the generation of inflammatory components. Recent studies reported that expression of IL-29 is dysregulated in inflammatory autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus, osteoarthritis, Sjögren's syndrome, psoriasis and systemic sclerosis. Furthermore, functional analysis revealed that IL-29 may involve in the pathogenesis of the inflammatory autoimmune disorders. In this review, we will systematically review the current knowledge about IL-29. The information collected revealed the regulatory role of IL-29 and may give important implications for its potential in clinical treatment.

Diminished secretion and function of IL-29 is associated with impaired IFN-α response of neonatal plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDCs) are key players in the antiviral immune response and type III IFNs such as IL-29 appear to play a pivotal role in pDC function. Pronounced susceptibility to viral infections in neonates is partly resulting from diminished antiviral immune mechanisms. Accordingly, the aim of the present study was to investigate the impact of IL-29 in the altered immune response of neonatal pDCs. PBMCs of adult and term newborns were stimulated with CpG-ODN2216 in the presence or absence of IL-29 and assessed for IFN-α production, downstream-signaling, and activation marker expression. A significantly lower IL-29 production after TLR9-specific stimulation was demonstrated in neonatal pDCs. IL-29 enhanced the IFN-α production of pDCs in adults compared to newborns. Newborn pDCs displayed a significantly lower surface expression of IL-10 and IL-28Rα receptor resulting in diminished STAT1 and IRF7 activation. Interestingly, concomitant stimulation with CpG-ODN2216/IL-29 had no impact on the expression of surface activation and maturation markers of pDCs in neither population. The diminished antiviral immune response of neonatal pDCs is associated with reduced production and cellular responses toward IL-29. Potential therapeutic agents enhancing the IL-29 response in neonatal pDCs possibly augment viral protection in newborns.

Dendritic cell subsets and locations

Dendritic cells (DCs) are a unique class of immune cells that act as a bridge between innate and adaptive immunity. The discovery of DCs by Cohen and Steinman in 1973 laid the foundation for DC biology, and the advances in the field identified different versions of DCs with unique properties and functions. DCs originate from hematopoietic stem cells, and their differentiation is modulated by Flt3L. They are professional antigen-presenting cells that patrol the environmental interphase, sites of infection, or infiltrate pathological tissues looking for antigens that can be used to activate effector cells. DCs are critical for the initiation of the cellular and humoral immune response and protection from infectious diseases or tumors. DCs can take up antigens using specialized surface receptors such as endocytosis receptors, phagocytosis receptors, and C type lectin receptors. Moreover, DCs are equipped with an array of extracellular and intracellular pattern recognition receptors for sensing different danger signals. Upon sensing the danger signals, DCs get activated, upregulate costimulatory molecules, produce various cytokines and chemokines, take up antigen and process it and migrate to lymph nodes where they present antigens to both CD8 and CD4 T cells. DCs are classified into different subsets based on an integrated approach considering their surface phenotype, expression of unique and conserved molecules, ontogeny, and functions. They can be broadly classified as conventional DCs consisting of two subsets (DC1 and DC2), plasmacytoid DCs, inflammatory DCs, and Langerhans cells.

Signaling Pathways of Type I and Type III Interferons and Targeted Therapies in Systemic Lupus Erythematosus

Type I and type III interferons (IFNs) share several properties in common, including the induction of signaling pathways, the activation of gene transcripts, and immune responses, against viral infection. Recent advances in the understanding of the molecular basis of innate and adaptive immunity have led to the re-examination of the role of these IFNs in autoimmune diseases. To date, a variety of IFN-regulated genes, termed IFN signature genes, have been identified. The expressions of these genes significantly increase in systemic lupus erythematosus (SLE), highlighting the role of type I and type III IFNs in the pathogenesis of SLE. In this review, we first discussed the signaling pathways and the immunoregulatory roles of type I and type III IFNs. Next, we discussed the roles of these IFNs in the pathogenesis of autoimmune diseases, including SLE. In SLE, IFN-stimulated genes induced by IFN signaling contribute to a positive feedback loop of autoimmunity, resulting in perpetual autoimmune inflammation. Based on this, we discussed the use of several specific IFN blocking strategies using anti-IFN-α antibodies, anti-IFN-α receptor antibodies, and IFN-α-kinoid or downstream small molecules, which intervene in Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathways, in clinical trials for SLE patients. Hopefully, the development of novel regimens targeting IFN signaling pathways will shed light on promising future therapeutic applications for SLE patients.

Interleukin 29 inhibits RANKL-induced osteoclastogenesis via activation of JNK and STAT, and inhibition of NF-κB and NFATc1

Interleukin (IL)-29 is known to modulate immune functions of monocytes or macrophages. In this study, we investigated the effect and its underlying mechanism of IL-29 on receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclastogenesis using murine macrophage cell line RAW264.7 cells and bone-marrow-derived monocyte/macrophage precursor cells (BMMs), and human peripheral blood mononuclear cells (PBMCs). In response to human recombinant IL-29, cell viability and apoptosis were assessed by Cell Counting Kit-8 and flow cytometry; the osteoclast formation and activity by tartrate-resistant acid phosphatase (TRAP) staining and pit formation assay, respectively; the expression and activation of molecules that associated with osteoclastogenesis by real time-PCR, immunoblotting or immunofluorescent analysis. IL-28 receptor α (IL-28Rα), a specific receptor of IL-29 was expressed on RAW264.7 cells. Although IL-29 did not affect the viability and apoptosis of RAW264.7 cells, it inhibited multinucleated cells in the differentiation of osteoclastogenesis, the bone-resorbing activity of mature osteoclasts and osteoclastic specific genes expression including TRAP, cathepsin K (CTSK), nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), C-Fos and matrix metallopeptidase 9 (MMP-9). This inhibitory effect of IL-29 was confirmed on BMMs and PBMCs and mediated via IL-28Rα through the activation of Stat1 and 3 and the suppression of nuclear factor kappa B (NF-κB) and NFATc1 nuclear translocation in RAW264.7 cells. In conclusion, IL-29 inhibited osteoclastogenesis via activation of STAT signaling pathway, prevention of NF-κB activation and NFATc1 translocation, and suppression of downstream osteoclastogenic genes expression.

Elevated Systemic and Parasite-Antigen Stimulated Levels of Type III IFNs in a Chronic Helminth Infection and Reversal Following Anthelmintic Treatment

Type III IFNs are important players in immunity to viral and bacterial infections. However, their association with helminth infections has not been examined. To explore the association of Type III IFNs with Strongyloides stercoralis (Ss) infection, we examined the systemic levels of IFN lambda-1, IFN lambda-2 and IFN lambda-3, IL-10, and CXCL10/IP-10 in Ss infected (INF, n = 44), helminth—uninfected (UN, n = 44) and in post-treatment INF individuals. We also examined the levels of IFN lambda-1, IFN lambda-2 and IFN lambda-3, IL-10, and CXCL10/IP-10 in whole blood culture supernatants stimulated with Ss somatic antigens, or PPD or LPS. Finally, we performed correlations of systemic Type III IFN levels with absolute numbers of dendritic cell subsets. Ss infection is characterized by elevated systemic levels of IFN lambda-1, IFN lambda-2 and IFN lambda-3, IL-10, and CXCL10/IP-10 in comparison to UN individuals and a significant reduction following anthelmintic treatment. Ss infection is also characterized by elevated levels of unstimulated or Ss antigen stimulated levels of IFN lambda-1, IFN lambda-2 and IFN lambda-3, CXCL10/IP-10 and a significant reduction following treatment. In addition, Ss infection is characterized by increased numbers of plasmacytoid and myeloid dendritic cells in comparison to UN individuals, with a significant reduction following anthelmintic treatment of INF individuals. Finally, Ss infection exhibits a significant positive correlation between the systemic levels of IFN lambda-2 and IFN lambda-3 and the numbers of plasmacytoid dendritic cells. Thus, Ss infection is characterized by elevations in systemic and antigen—induced levels of Type III IFNs, which is positively associated with the numbers of plasmacytoid dendritic cells and reversed upon anthelmintic treatment.

Interleukin 29 activates expression of tissue inhibitor of metalloproteinase 1 in macrophages via toll‑like receptor 2

Obesity and diabetes are characterized by low grade chronic inflammation status and insulin resistance in adipose tissue associated with metalloproteinase inhibitor 1 (TIMP1). Interleukin (IL)29, exhibits multiple immune regulatory activities. However, the role of IL29 and its effects on TIMP1 remain to be elucidated. The present study was designed to investigate the effects of IL29 on expression of TIMP1 in macrophages associated with inflammation in adipose tissue. IL29 and high glucose were used to activate Raw264.7 cells and primary macrophages with or without antibody‑mediated inhibition of toll like receptor (TLR) 2 and TLR4. TIMP1 was measured in culture media of Raw264.7 cells and primary macrophages by ELISA. IL29 and high glucose increased TIMP1 levels in Raw264.7 cells and primary macrophages. Antibody‑mediated inhibition of TLR2 or TLR2 gene knockout decreased TIMP1 levels activated by IL29, however not by high glucose in the medium of Raw264.7 cells and primary macrophages. Furthermore, antibody‑mediated inhibition of TLR4 or TLR4 gene knockout decreased TIMP1 levels which were stimulated by high glucose, not by IL29 in the medium of Raw264.7 cells and primary macrophages. The results of the present study indicate that TLR2 is involved in IL29‑stimulated TIMP1 expression in Raw264.7 cells and primary macrophages.

Interferon-λs: Front-Line Guardians of Immunity and Homeostasis in the Respiratory Tract

Type III interferons (IFNs), also termed lambda IFNs (IFNλs) or interleukins-28/29, constitute a new addition to the IFN family. They are induced upon infection and are particularly abundant at barrier surfaces, such as the respiratory and gastrointestinal tracts. Although they signal through a unique heterodimeric receptor complex comprising IFNLR1 and IL10RB, they activate a downstream signaling pathway remarkably similar to that of type I IFNs and share many functions with them. Yet, they also have important differences which are only now starting to unfold. Here, we review the current literature implicating type III IFNs in the regulation of immunity and homeostasis in the respiratory tract. We survey the common and unique characteristics of type III IFNs in terms of expression patterns, cellular targets, and biological activities and discuss their emerging role in first line defenses against respiratory viral infections. We further explore their immune modulatory functions and their involvement in the regulation of inflammatory responses during chronic respiratory diseases, such as asthma and chronic obstructive pulmonary disease. Type III IFNs are, therefore, arising as front-line guardians of immune defenses in the respiratory tract, fine tuning inflammation, and as potential novel therapeutics for the treatment of diverse respiratory diseases, including influenza virus infection and asthma.

IFN-λ suppresses intestinal inflammation by non-translational regulation of neutrophil function

Interferon-λ (IFN-λ) is a central regulator of mucosal immunity; however, its signaling specificity relative to that of type I interferons is poorly defined. IFN-λ can induce antiviral interferon-stimulated genes (ISGs) in epithelia, while the effect of IFN-λ in non-epithelial cells remains unclear. Here we report that neutrophils responded to IFN-λ. We found that in addition to inducing ISG transcription, IFN-λ (but not IFN-β) specifically activated a translation-independent signaling pathway that diminished the production of reactive oxygen species and degranulation in neutrophils. In mice, IFN-λ was elicited by enteric viruses and acted on neutrophils to decrease oxidative stress and intestinal damage. Thus, IFN-λ acted as a unique immunomodulatory agent by modifying transcriptional and non-translational neutrophil responses, which might permit a controlled development of the inflammatory process.

Interferon-λs and Plasmacytoid Dendritic Cells: A Close Relationship

Interferon lambdas (IFNλs) are recently discovered cytokines acting not only at the first line of defense against viral infections but also at the mucosal barriers. In fact, a peculiar feature of the IFNλ system is the restricted expression of the functional IFNλR, which is known to be limited to epithelial cells and discrete leukocyte subsets, including the plasmacytoid dendritic cells (pDCs). In the latter case, current data, discussed in this minireview, indicate that IFNλs positively regulate various pDC functions, including pDC expression of interferon-dependent gene (ISG) mRNAs, production of cytokines, survival, and phenotype. Although the knowledge of the effects on pDCs by IFNλs is still incomplete, we speculate that the peculiar pDC responsiveness to IFNλs provide unique advantages for these innate immune cells, not only for viral infections but also during autoimmune disorders and/or tumors, in which pDC involvement and activation variably contribute to their pathogenesis.

Involvement of NK Cells in IL-28B-Mediated Immunity against Influenza Virus Infection

IL-28B is a member of the newly discovered type III IFN family and exhibits unique antiviral properties compared with other family members. NK cells play a critical role in defending against viruses; however, little is known about the role of IL-28B in NK cell function. In a mouse model of influenza A virus (mouse adapted influenza A/PR/8/34 strain) infection, long-term overexpression of IL-28B induced by hepatocyte-specific gene delivery exerted a strong antiviral effect in the presence of NK cells. In IL-28B-overexpressing wild-type mice, the percentages and absolute numbers of NK cells in the spleen, liver, and lung were markedly increased, with higher proliferation and accelerated NK cell maturation based on phenotypes staining with CD11b and CD27 or CD11b and KLRG1. Furthermore, the effect of IL-28B on NK cells was macrophage dependent, as confirmed in an in vitro coculture assay and in in vivo macrophage- or alveolar macrophage-depletion experiments. Transwell studies demonstrated that CFSE-labeled NK cell proliferation was driven, in a dose-dependent manner, by unknown soluble factor(s) secreted by IL-28B-stimulated alveolar macrophages, without requiring direct cell-cell contact. An understanding of the NK cell-promoting features of IL-28B will facilitate future clinical application of this cytokine.

A novel method for detection of IFN-lambda 3 binding to cells for quantifying IFN-lambda receptor expression

Type III interferons (IFN-lambdas) are important antiviral cytokines that also modulate immune responses acting through a unique IFN-λR1/IL-10R2 heterodimeric receptor. Conflicting data has been reported for which cells express the IFN-λR1 subunit and directly respond to IFN-λs. In this study we developed a novel method to measure IFN-λ3 binding to IFN-λR1/IL-10R2 on the surface of cells and relate this to a functional readout of interferon stimulated gene (ISG) activity in various cell lines. We show that Huh7.5 hepatoma cells bind IFN-λ3 at the highest levels with the lowest Kd(app), translating to the highest induction of various ISGs. Raji and Jurkat cell lines, representing B and T cells, respectively, moderately bind IFN-λ3 and have lower ISG responses. U937 cells, representing monocytes, did not bind IFN-λ3 well and therefore, did not have any ISG induction. Importantly, knockdown of IFNLR1 in Huh7.5 cells decreased our binding signal proportionally and reduced ISG induction by up to 93%. IFN-λ3 responsiveness increased over time with maximal ISG responses seen at 24h for all but one gene. These data confirm our new IFN-λ3 binding assay can be used to quantify IFN-λ receptor surface expression on a variety of cell types and reflects IFN-λ3 responsiveness.

Peg-Interferon Lambda Treatment Induces Robust Innate and Adaptive Immunity in Chronic Hepatitis B Patients

IFN-lambda (IFNλ) is a member of the type III IFN family and is reported to possess anti-pathogen, anti-cancer, and immunomodulatory properties; however, there are limited data regarding its impact on host immune responses in vivo. We performed longitudinal and comprehensive immunosurveillance to assess the ability of pegylated (peg)-IFNλ to augment antiviral host immunity as part of a clinical trial assessing the efficacy of peg-IFNλ in chronic hepatitis B (CHB) patients. These patients were pretreated with directly acting antiviral therapy (entecavir) for 12 weeks with subsequent addition of peg-IFNλ for up to 32 weeks. In a subgroup of patients, the addition of peg-IFNλ provoked high serum levels of antiviral cytokine IL-18. We also observed the enhancement of natural killer cell polyfunctionality and the recovery of a pan-genotypic HBV-specific CD4⁺ T cells producing IFN-γ with maintenance of HBV-specific CD8⁺ T cell antiviral and cytotoxic activities. It was only in these patients that we observed strong virological control with reductions in both viral replication and HBV antigen levels. Here, we show for the first time that in vivo peg-IFNλ displays significant immunostimulatory properties with improvements in the main effectors mediating anti-HBV immunity. Interestingly, the maintenance in HBV-specific CD8⁺ T cells in the presence of peg-IFNλ is in contrast to previous studies showing that peg-IFNα treatment for CHB results in a detrimental effect on the functionality of this important antiviral T cell compartment.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov NCT01204762.

Contribution of type III interferons to antiviral immunity: location, location, location

Type I interferons (IFN-α/β) and the more recently identified type III IFNs (IFN-λ) function as the first line of defense against virus infection and regulate the development of both innate and adaptive immune responses. Type III IFNs were originally identified as a novel ligand-receptor system acting in parallel with type I IFNs, but subsequent studies have provided increasing evidence for distinct roles for each IFN family. In addition to their compartmentalized antiviral actions, these two systems appear to have multiple levels of cross-regulation and act coordinately to achieve effective antimicrobial protection with minimal collateral damage to the host.

Identification of Type III Interferon (IFN-λ) in Chinese Goose: Gene Structure, Age-Dependent Expression Profile, and Antiviral Immune Characteristics In Vivo and In Vitro

Type III interferons (IFN-λ1/λ2/λ3, also known as IL-29/28A/28B, and IFN-λ4) are a recently discovered interferon group. In this study, we first identified the Chinese goose IFN-λ (goIFN-λ). The full-length sequence of goIFN-λ was found to be 823 bp. There was only one open reading frame that contained 570 bp, and, encoded 189 amino acids. The predicted goIFN-λ protein showed 78%, 67%, and 40% amino acid identity with duIFN-λ, chIFN-λ, and hIFN-λ3, respectively. The tissue distribution of goIFN-λ existed as a parallel distribution with goIFNLR1 as its functional receptor, which was mainly expressed in epithelium-rich tissues, such as lung, gizzard, proventriculus, skin and pancreas, and immune tissues, such as harderian gland and thymus. Furthermore, the immunological characteristics studies of goIFN-λ showed that there was a significant increase in the mRNA at the transcriptional level of goIFN-λ after the peripheral blood mononuclear cells were stimulated with ploy (I:C) and ODN2006, and infected with Gosling plague virus (GPV). In vivo, the mRNA transcriptional level of goIFN-λ increased nearly 20 times in the lung tissue and nearly 40 times in the pancreatic tissue after being artificially infected with H9N2 AIV. It is suggested that goIFN-λ might play a pivotal role in the mucosal immune protection and antiviral defense.

Type-III interferons and rheumatoid arthritis: Correlation between interferon lambda 1 (interleukin 29) and antimutated citrullinated vimentin antibody levels

AIM

To assess serum type III or lambda (λ) interferons (IFN) levels and its clinical and laboratory associations in rheumatoid arthritis (RA).

METHODS

A cross-sectional study including 43 patients with RA (86% females; age 45.3 ± 10.3 years) and 43 healthy individuals was performed. Clinical data including disease activity, acute-phase reactants, rheumatoid factor and anticyclic citrullinated peptide (anti-CCP) antibodies were collected. Serum IFNλ1, IFNλ2, IFNλ3, CXCL8 and anti-mutated citrullinated vimentin (anti-MCV) antibody levels were measured.

RESULTS

Patients with RA had higher IFNλ1 (113.5 ± 118.6 pg/mL versus 55.9 ± 122.3 pg/mL; p < 0.0001) and IFNλ2 (245.4 ± 327.7 pg/mL versus 5.1 ± 11.0 pg/mL; p = 0.009) levels than controls, but not IFNλ3 levels. Notably, IFNλ1 levels were found to be higher in both patients with active disease (124.9 ± 135.9 pg/mL; p < 0.001) and quiescent disease (99.0 ± 93.7 pg/mL; p < 0.01), while IFNλ2 levels were higher only in patients with active disease (264.0 ± 356.1 pg/mL; p = 0.02). A noteworthy association between serum IFNλ1 levels and anti-MCV antibody titers (Spearman's rho coefficient 0.36, 95% CI 0.36 to 0.61; p = 0.02) was observed.

CONCLUSION

Serum IFNλ1 and IFNλ2 levels are abnormally elevated in patients with RA and the former are linearly associated with circulating anti-MCV antibody levels. These results may place type-III IFN as an attractive new therapeutic target in RA.

Synergistic production of TNFα and IFNα by human pDCs incubated with IFNλ3 and IL-3

In this study, we investigated whether IFNλ3 and IL-3 reciprocally influence their capacity to activate various functions of human plasmacytoid dendritic cells (pDCs). In fact, we preliminarily observed that IFNλ3 upregulates the expression of the IL-3Rα (CD123), while IL-3 augments the expression of IFNλR1 in pDCs. As a result, we found that combination of IFNλ3 and IL-3 induces a strong potentiation in the production of TNFα, IFNα, as well as in the expression of Interferon-Stimulated Gene (ISG) mRNAs by pDCs, as compared to either IFNλ3 or IL-3 alone. In such regard, we found that endogenous IFNα autocrinally promotes the expression of ISG mRNAs in IL-3-, but not in IFNλ3 plus IL-3-, treated pDCs. Moreover, we uncovered that the production of IFNα by IFNλ3 plus IL-3-treated pDCs is mostly dependent on endogenously produced TNFα. Altogether, our data demonstrate that IFNλ3 and IL-3 collaborate to promote, at maximal levels, discrete functional responses of human pDCs.

Immune Cell Profiling of IFN-λ Response Shows pDCs Express Highest Level of IFN-λR1 and Are Directly Responsive via the JAK-STAT Pathway

The interferon lambda (IFN-λ) cytokines have well-known antiviral properties, yet their contribution to immune regulation is not well understood. Epithelial cells represent the major target cell of IFN-λ; peripheral blood mononuclear cells are generally considered nonresponsive, with the exception of plasmacytoid dendritic cells (pDCs). In this study we aimed to define the potential for discrete subpopulations of cells to directly respond to IFN-λ. Analysis of peripheral blood leukocytes reveals that, while pDCs uniformly express the highest levels of IFN-λ receptor, a small proportion of B cells and monocytes also express the receptor. Nevertheless, B cells and monocytes respond poorly to IFN-λ stimulation in vitro, with minimal STAT phosphorylation and interferon-stimulated gene (ISG) induction observed. We confirm that pDCs respond to IFN-λ in vitro, upregulating their expression of pSTAT1, pSTAT3, and pSTAT5. However, we found that pDCs do not upregulate pSTAT6 in response to IFN-λ treatment. Our results highlight unique aspects of the response to IFN-λ and confirm that while the IFN-λ receptor is expressed by a small proportion of several different circulating immune cell lineages, under normal conditions only pDCs respond to IFN-λ stimulation with robust STAT phosphorylation and ISG induction. The difference in STAT6 responsiveness of pDCs to type I and type III interferons may help explain the divergence in their biological activities.

An efficient method for gene silencing in human primary plasmacytoid dendritic cells: silencing of the TLR7/IRF-7 pathway as a proof of concept

Plasmacytoid dendritic cells (pDC) are specialized immune cells that produce massive levels of type I interferon in response to pathogens. Unfortunately, pDC are fragile and extremely rare, rendering their functional study a tough challenge. However, because of their central role in numerous pathologies, there is a considerable need for an efficient and reproducible protocol for gene silencing in these cells. In this report, we tested six different methods for siRNA delivery into primary human pDC including viral-based, lipid-based, electroporation, and poly-ethylenimine (PEI) technologies. We show that lipid-based reagent DOTAP was extremely efficient for siRNA delivery into pDC, and did not induce cell death or pDC activation. We successfully silenced Toll-Like Receptor 7 (TLR7), CXCR4 and IFN regulatory factor 7 (IRF-7) gene expression in pDC as assessed by RT-qPCR or cytometry. Finally, we showed that TLR7 or IRF-7 silencing in pDC specifically suppressed IFN-α production upon stimulation, providing a functional validation of our transfection protocol.

Interleukin-29 Enhances Synovial Inflammation and Cartilage Degradation in Osteoarthritis

We have recently shown that IL-29 was an important proinflammatory cytokine in pathogenesis of rheumatoid arthritis (RA). Inflammation also contributes to the pathogenesis of osteoarthritis (OA). The aim of this study was to investigate the effect and mechanism of IL-29 on cytokine production and cartilage degradation in OA. The mRNA levels of IL-29 and its specific receptor IL-28Ra in peripheral blood mononuclear cells (PBMCs) were significantly increased in OA patients when compared to healthy controls (HC). In the serum, IL-29 protein levels were higher in OA patients than those in HC. Immunohistochemistry revealed that both IL-29 and IL-28Ra were dramatically elevated in OA synovium compared to HC; synovial fibroblasts (FLS) and macrophages were the main IL-29-producing cells in OA synovium. Furthermore, recombinant IL-29 augmented the mRNA expression of IL-1β, IL-6, IL-8, and matrix-metalloproteinase-3 (MMP-3) in OA FLS and increased cartilage degradation when ex vivo OA cartilage explant was coincubated with OA FLS. Finally, in OA FLS, IL-29 dominantly activated MAPK and nuclear factor-κB (NF-κB), but not Jak-STAT and AKT signaling pathway as examined by western blot. In conclusion, IL-29 stimulates inflammation and cartilage degradation by OA FLS, indicating that this cytokine is likely involved in the pathogenesis of OA.

IFN-λ is able to augment TLR-mediated activation and subsequent function of primary human B cells

During the past decade, increased emphasis has been placed on finding alternatives to IFN-α-based therapies. One such alternative, IFN-λ, has shown therapeutic promise in a variety of diseases, but research of this family of cytokines has been primarily focused on their antiviral activities. The goal of the present study was to investigate the role of IFN-λ in the regulation and modulation of B cell function. We show that, similar to IFN-α, IFN-λ1 is able to augment TLR-mediated B cell activation, partially attributed to an upregulation of TLR7 expression, and that both naïve and memory B cells express the limiting type III IFN receptor component, IFN-λR1. Furthermore, this IFN-λ-enhanced B cell activation resulted in increased cytokine and Ig production during TLR7 challenge, most prominently after the addition of helper T cell signals. Ultimately, these elevated cytokine and Ig levels could be partially attributed to the increase in proliferation of TLR7-challenged B cells by both type I and type III IFNs. These findings demonstrate the ability of IFN-λ to boost humoral immunity, an important attribute to consider for further studies on immunity to pathogens, vaccine development, and ongoing advancement of therapeutic strategies aimed at replacing IFN-α-based treatments with IFN-λ.

Endogenously produced TNF-α contributes to the expression of CXCL10/IP-10 in IFN-λ3-activated plasmacytoid dendritic cells

The interplay between IFN-λs and dendritic cells is becoming increasingly relevant, particularly in light of their key role in inducing the antiviral state, including in hepatitis C virus infection. In this work, we have analyzed extensively how human plasmacytoid dendritic cells respond to IFN-λ3. We report that plasmacytoid dendritic cells incubated with IFN-λ3 prolong their survival; alter their expression pattern of surface HLA-DRα, CD123, CD86, and CD303; and time dependently produce IFN-α, CXCL10/IFN-γ-induced protein 10, and even modest quantities of TNF-α. Nevertheless, endogenously produced TNF-α, but not IFN-α, was found to be essential for driving the expression of CXCL10/IFN-γ-induced protein 10 in IFN-λ3-treated plasmacytoid dendritic cells, as revealed by neutralizing experiments by use of adalimumab, etanercept, and infliximab. We also observed that based on the kinetics and levels of IFN-α and CXCL10/IFN-γ-induced protein 10 produced by their IFN-λ3-treated plasmacytoid dendritic cells, healthy donors could be categorized into 2 and 3 groups, respectively. In particular, we identified a group of donors whose plasmacytoid dendritic cells produced modest quantities of CXCL10/IFN-γ-induced protein 10; another one whose plasmacytoid dendritic cells produced elevated CXCL10/IFN-γ-induced protein 10 levels, already after 18 h, declining thereafter; and a 3rd group characterized by plasmacytoid dendritic cells releasing very high CXCL10/IFN-γ-induced protein 10 levels after 42 h only. Finally, we report that in plasmacytoid dendritic cells, equivalent concentrations of IFN-λ3 and IFN-λ1 promote survival, antigen modulation, and cytokine production in a comparable manner and without acting additively/synergistically. Altogether, data not only extend the knowledge on the biologic effects that IFN-λs exert on plasmacytoid dendritic cells but also add novel light to the networking between IFN-λs and plasmacytoid dendritic cells in fighting viral diseases.

Guarding the frontiers: the biology of type III interferons

Type III interferons (IFNs) or IFN-λs regulate a similar set of genes as type I IFNs, but whereas type I IFNs act globally, IFN-λs primarily target mucosal epithelial cells and protect them against the frequent viral attacks that are typical for barrier tissues. IFN-λs thereby help to maintain healthy mucosal surfaces through immune protection, without the significant immune-related pathogenic risk associated with type I IFN responses. Type III IFNs also target the human liver, with dual effects: they induce an antiviral state in hepatocytes, but specific IFN-λ4 action impairs the clearance of hepatitis C virus and could influence inflammatory responses. This constitutes a paradox that has yet to be resolved.

The role of DCs in the immunopathogenesis of chronic HBV infection and the methods of inducing DCs maturation

Chronic hepatitis B virus (HBV) infection is the result of an inadequate immune response towards the virus. Dendritic cells (DCs), as the most efficient professional antigen-presenting cells (APCs), possess the strongest antigen presenting the effect in the body and can stimulate the initial T cell activation and proliferation. DCs of patients with chronic HBV infection are impaired, resulting in more tolerogenic rather than immunogenic responses, which may contribute to viral persistence. Recently, numerous methods have been developed to induce DCs maturation. To date, recombinant human granulocyte-macrophage colony stimulating factor (rhGM-CSF) combined with interleukin-4 (rhIL-4) has been a classic culture combination to DCs. The recently classified type III interferon group interferon-λ (IFN-λ) displays antiviral, antitumor, and immunoregulatory activity. In our laboratory, we demonstrate that IFN-λ1 combined with rhGM-CSF and rhIL-4 can significantly increase the expression of DC surface molecules and the secretion of interleukin-12 (IL-12) and interferon-γ (IFN-γ) in patients with chronic hepatitis B infection. In this review, we emphasize on the role of DCs in the immunopathogenesis of chronic HBV infection. Importantly, we systematic review that the latest update in the current status of knowledge on the methods of inducing DCs maturation in anti-HBV immunity. What's more, we conclude that IFN-λ1 combined with GM-CSF and IL-4 can induce DCs maturation, which could become a possibility to be applied to the autologus dendritic cell vaccine to treat chronic hepatitis B.

Kinetic Differences and Synergistic Antiviral Effects Between Type I and Type III Interferon Signaling Indicate Pathway Independence

The spread of acute respiratory viral infections is controlled by type I and III interferon (IFN) signaling. While the mechanisms of type I IFN signaling have been studied in detail, features that distinguish type III IFN signaling remain poorly understood. Type III IFNs play an essential role in limiting infections of intestinal and respiratory epithelial surfaces; however, type III IFNs have been shown to activate similar genes to type I IFNs, raising the question of how these IFNs differ and their signals interact. We measured the kinetics of type I and III IFN activation, functional stability, and downstream antiviral responses on A549 human lung epithelial cells. Similar kinetics were found for transcriptional upregulation and secretion of type I and III IFNs in response to infection by an RNA virus, peaking at 12 h postinfection, and both protein types had similar stabilities with functional half-lives extending beyond 2 days. Both IFNs activated potent cellular antiviral responses; however, responses to type III IFNs were delayed by 2-6 h relative to type I IFN responses. Combined treatments with type I and III IFNs produced enhanced antiviral effects, and quantitative analysis of these data with a Bliss interaction model provides evidence for independence of type I and III IFN downstream signaling pathways. This novel synergistic interaction has therapeutic implications for treatment of respiratory virus infections.

BDCA3(+)CLEC9A(+) human dendritic cell function and development

Dendritic cells (DC) are the most potent antigen presenting cells (APC). They comprise a family of different subsets and play an essential role in the induction and regulation of immune responses. Recently, gene expression profiling identified BDCA3(+)CLEC9A(+) DC as a separate human DC subset. This subset was identified in blood, where they represent the smallest population of human DC, as well as in lymphoid and peripheral tissues. This review summarizes the phenotypic, functional and developmental characteristics of BDCA3(+)CLEC9A(+) DC in relation to their mouse equivalents CD8α(+) DC and CD103(+) DC and other human DC subsets. Apart from being potent antigen presenting cells, their specialized functional capacities compared to other human DC subsets, indicate that these BDCA3(+)CLEC9A(+) DC are of major importance in the induction of anti-viral and anti-tumor immunity. Further characterization of their functional properties, developmental pathways and underlying molecular mechanisms may identify target molecules to fully exploit the immune modulatory function of BDCA3(+)CLEC9A(+) DC and potential use of these cells in immunotherapy.

Advanced molecular surveillance of hepatitis C virus

Hepatitis C virus (HCV) infection is an important public health problem worldwide. HCV exploits complex molecular mechanisms, which result in a high degree of intrahost genetic heterogeneity. This high degree of variability represents a challenge for the accurate establishment of genetic relatedness between cases and complicates the identification of sources of infection. Tracking HCV infections is crucial for the elucidation of routes of transmission in a variety of settings. Therefore, implementation of HCV advanced molecular surveillance (AMS) is essential for disease control. Accounting for virulence is also important for HCV AMS and both viral and host factors contribute to the disease outcome. Therefore, HCV AMS requires the incorporation of host factors as an integral component of the algorithms used to monitor disease occurrence. Importantly, implementation of comprehensive global databases and data mining are also needed for the proper study of the mechanisms responsible for HCV transmission. Here, we review molecular aspects associated with HCV transmission, as well as the most recent technological advances used for virus and host characterization. Additionally, the cornerstone discoveries that have defined the pathway for viral characterization are presented and the importance of implementing advanced HCV molecular surveillance is highlighted.

Effect of Interleukin-29 on Interferon-α Secretion by Peripheral Blood Mononuclear Cells

Objective

The effect of interleukin (IL)-29, a new therapeutic agent similar to type I interferons (IFNs), on IFN-α secretion of human plasmacytoid dendritic cells (pDCs) has not been studied. Therefore, in this study, we aimed to clarify the effect of IL-29 on IFN-α secretion of pDCs using human peripheral blood mononuclear cells (PBMCs) in the presence of cytosine-phosphate-guanosinemotif-containing oligodeoxy nucleotides (CpG).

Materials and Methods

In this experimental and prospective study, PBMCs were ob- tained from 11 healthy volunteers and divided into four culture conditions: I. control, II. CpG treatment, III. IL-29 treatment and IV. CpG plus IL-29 treatment. The amount of IFN-α secretion was measured from each culture supernatant by flow cytometry using the flowcytomix apparatus (eBioscience, Vienna, Austria). Fractional IFN-α production of the cultured PBMCs was measured by intracellular staining using the cytomics FC 500 system (Beckman Coulter, Brea, CA, USA) with CXP Software.

Results

The mean ± standard deviation (SD) of supernatant IFN-α secretion per pDC/μL was 5.7 ± 9.3 pg/mL/count/µL for condition I, 1071.5 ± 1026.6 pg/mL/count/µL for condition II, 14.1 ± 21.1 pg/mL/count/µL for condition III, and 1913.9 ± 1525.9 pg/mL/count/µL for condition IV. There were statistically significant differences between conditions I and II as well as betweenconditions II and IV. Intracellular IFN-α production was only detectable in the pDC fraction from one culture; the production amount was similar between the cells treated with CpG and those treated with CpG plus IL-29. Natural killer (NK) cell production of IFN-α was observed in two out of three cultures and one culture showed IFN- α production in the monocyte fraction.

Conclusion

IL-29 alone did not show any effect on IFN-α secretion of PBMCs. However, the addition of CpG along with IL-29 enhanced IFN-α secretion of PBMCs. Given that pDCs are the major secretors of IFN-α in peripheral blood, this result has suggested the possibility that IL-29 has an enhancing effect in human pDC IFN-α secretion. Although the supernatant IFN-α secretion was not directly correlated with pDCs’s intracellular IFN-α production in this study, prolonged incubation of pDC and other PB subsets with CpG or IL-29 for over 4 hours could be applied in future studies. These studies would help to elucidate the mechanism of action of IL-29 in human pDCs associated with viral infections.

Interferon gene expression in sputum cells correlates with the Asthma Index Score during virus-induced exacerbations

Background

The majority of asthma exacerbations are related to viral respiratory infections. Some, but not all, previous studies have reported that low interferon responses in patients with asthma increase the risk for virus‐induced exacerbations.

Objective

We sought to determine the relationship between lower airway inflammatory biomarkers, specifically interferon gene expression, and the severity or presence of an exacerbation in asthmatics experiencing a naturally occurring viral infection.

Methods

Sputum samples were analysed from subjects in an asthma exacerbation study who experienced a confirmed viral infection. Subjects were monitored for daily symptoms, medication use and peak expiratory flow rate until baseline. Sputum samples were assessed for cell counts and gene expression.

Results

Interferon gamma expression was significantly greater in patients with asthma exacerbations compared to non‐exacerbating patients (P = 0.002). IFN‐α1, IFN‐β1 and IFN‐γ mRNA levels correlated with the peak Asthma Index (r = 0.58, P < 0.001; r = 0.57, P = 0.001; and r = 0.51, P = 0.004, respectively). Additionally, IL‐13, IL‐10 and eosinophil major basic protein mRNA levels were greater in patients with asthma exacerbations compared to non‐exacerbating patients (P = 0.03, P = 0.06 and P = 0.02, respectively), and IL‐13 mRNA correlated with the peak Asthma Index (P = 0.006).

Conclusions

Our findings indicate that asthma exacerbations are associated with increased rather than decreased expression of interferons early in the course of infection. These findings raise the possibility that excessive virus‐induced interferon production during acute infections can contribute to airway inflammation and exacerbations of asthma.

IFN-λ-mediated IL-12 production in macrophages induces IFN-γ production in human NK cells

With increasing interest in alternative options to interferon-alpha-based treatments, IFN-λ has shown therapeutic promise in a variety of diseases. Although the antiviral activity of IFN-λ has been extensively studied, there is limited knowledge regarding the immunological functions of IFN-λ and how these differ from those of other classes of IFNs. In this study, we investigated the effects of IFN-λ on primary human NK cells, both in a direct and indirect capacity. We demonstrate that in contrast to interferon-alpha, IFN-λ is unable to directly stimulate NK cells, due to the absence of IFN-λ receptor chain 1 (IFN-λR1) on NK cells. However, IFN-λ, in combination with TLR4 challenge, is able to induce the production of select members of the IL-12 family of cytokines in monocyte-derived macrophages. We further show that through macrophage-mediated IL-12 production, IFN-λ is able to indirectly affect NK cells and ultimately induce IFN-γ production.