The lambda interferons: guardians of the immune-epithelial interface and the T-helper 2 response

Pathogenicity of Type I Interferons in Mycobacterium tuberculosis

Tuberculosis (TB) is a leading cause of mortality due to infectious disease and rates have increased during the emergence of COVID-19, but many of the factors determining disease severity and progression remain unclear. Type I Interferons (IFNs) have diverse effector functions that regulate innate and adaptive immunity during infection with microorganisms. There is well-documented literature on type I IFNs providing host defense against viruses; however, in this review, we explore the growing body of work that indicates high levels of type I IFNs can have detrimental effects to a host fighting TB infection. We report findings that increased type I IFNs can affect alveolar macrophage and myeloid function, promote pathological neutrophil extracellular trap responses, inhibit production of protective prostaglandin 2, and promote cytosolic cyclic GMP synthase inflammation pathways, and discuss many other relevant findings.

Functions of IFNλs in Anti-Bacterial Immunity at Mucosal Barriers

Type III interferons (IFNs), or IFNλs, are cytokines produced in response to microbial ligands. They signal through the IFNλ receptor complex (IFNLR), which is located on epithelial cells and select immune cells at barrier sites. As well as being induced during bacterial or viral infection, type III IFNs are produced in response to the microbiota in the lung and intestinal epithelium where they cultivate a resting antiviral state. While the multiple anti-viral activities of IFNλs have been extensively studied, their roles in immunity against bacteria are only recently emerging. Type III IFNs increase epithelial barrier integrity and protect from infection in the intestine but were shown to increase susceptibility to bacterial superinfections in the respiratory tract. Therefore, the effects of IFNλ can be beneficial or detrimental to the host during bacterial infections, depending on timing and biological contexts. This duality will affect the potential benefits of IFNλs as therapeutic agents. In this review, we summarize the current knowledge on IFNλ induction and signaling, as well as their roles at different barrier sites in the context of anti-bacterial immunity.

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.

Interferon lambda 4 can directly activate human CD19+ B cells and CD8+ T cells

Compared with the ubiquitous expression of type I (IFNα and IFNβ) interferon receptors, type III (IFNλ) interferon receptors are mainly expressed in epithelial cells of mucosal barriers of the of the intestine and respiratory tract. Consequently, IFNλs are important for innate pathogen defense in the lung and intestine. IFNλs also determine the outcome of hepatitis C virus (HCV) infections, with IFNλ4 inhibiting spontaneous clearance of HCV. Because viral clearance is dependent on T cells, we explored if IFNλs can directly bind to and regulate human T cells. We found that human B cells and CD8+ T cells express the IFNλ receptor and respond to IFNλs, including IFNλ4. IFNλs were not inhibitors but weak stimulators of B- and T-cell responses. Furthermore, IFNλ4 showed neither synergistic nor antagonistic effects in co-stimulatory experiments with IFNλ1 or IFNα. Multidimensional flow cytometry of cells from liver biopsies of hepatitis patients from IFNλ4-producers showed accumulation of activated CD8+ T cells with a central memory-like phenotype. In contrast, CD8+ T cells with a senescent/exhausted phenotype were more abundant in IFNλ4-non-producers. It remains to be elucidated how IFNλ4 promotes CD8 T-cell responses and inhibits the host immunity to HCV infections.

Plasmacytoid dendritic cells and asthma: a review of current knowledge

INTRODUCTION

While medications are available to treat asthma symptoms and control inflammation, no treatments can cure asthma, and efforts to develop primary prevention strategies or improved exacerbation management are limited by incomplete knowledge of the mechanisms responsible for asthma development and progression. Plasmacytoid dendritic cells (pDC) are involved in anti-viral host defense and immune regulation, and increasing evidence suggests a role for pDC in asthma pathogenesis.

AREAS COVERED

We undertook a literature search using PubMed for articles including the phrase 'plasmacytoid dendritic cells and asthma' published from 2015 to 2020. We reviewed the remarkable progress made over the past 5 years in understanding the role of pDC in asthma pathogenesis and how pDC regulate anti-viral immune function. This review highlights key recent findings in asthma pathogenesis and virus-triggered asthma exacerbations; pDC biology and functionality; how pDC regulate the immune response; and pDC function in asthma.

EXPERT OPTION

A deeper understanding of pDC function provides an important foundation for future pDC-targeted therapies that might prevent and treat asthma.

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.

Interferon Lambda: Modulating Immunity in Infectious Diseases

Interferon lambdas (IFN-λs; IFNL1-4) modulate immunity in the context of infections and autoimmune diseases, through a network of induced genes. IFN-λs act by binding to the heterodimeric IFN-λ receptor (IFNLR), activating a STAT phosphorylation-dependent signaling cascade. Thereby hundreds of IFN-stimulated genes are induced, which modulate various immune functions via complex forward and feedback loops. When compared to the well-characterized IFN-α signaling cascade, three important differences have been discovered. First, the IFNLR is not ubiquitously expressed: in particular, immune cells show significant variation in the expression levels of and susceptibilities to IFN-λs. Second, the binding affinities of individual IFN-λs to the IFNLR varies greatly and are generally lower compared to the binding affinities of IFN-α to its receptor. Finally, genetic variation in the form of a series of single-nucleotide polymorphisms (SNPs) linked to genes involved in the IFN-λ signaling cascade has been described and associated with the clinical course and treatment outcomes of hepatitis B and C virus infection. The clinical impact of IFN-λ signaling and the SNP variations may, however, reach far beyond viral hepatitis. Recent publications show important roles for IFN-λs in a broad range of viral infections such as human T-cell leukemia type-1 virus, rotaviruses, and influenza virus. IFN-λ also potentially modulates the course of bacterial colonization and infections as shown for Staphylococcus aureus and Mycobacterium tuberculosis. Although the immunological processes involved in controlling viral and bacterial infections are distinct, IFN-λs may interfere at various levels: as an innate immune cytokine with direct antiviral effects; or as a modulator of IFN-α-induced signaling via the suppressor of cytokine signaling 1 and the ubiquitin-specific peptidase 18 inhibitory feedback loops. In addition, the modulation of adaptive immune functions via macrophage and dendritic cell polarization, and subsequent priming, activation, and proliferation of pathogen-specific T- and B-cells may also be important elements associated with infectious disease outcomes. This review summarizes the emerging details of the IFN-λ immunobiology in the context of the host immune response and viral and bacterial infections.

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.

Transcriptional profiling of the ovine abomasal lymph node reveals a role for timing of the immune response in gastrointestinal nematode resistance

Gastrointestinal nematodes are a serious cause of morbidity and mortality in grazing ruminants. The major ovine defence mechanism is acquired immunity, with protective immunity developing over time in response to infection. Nematode resistance varies both within and between breeds and is moderately heritable. A detailed understanding of the genes and mechanisms involved in protective immunity, and the factors that regulate this response, is required to aid both future breeding strategies and the development of effective and sustainable nematode control methods. The aim of this study was to compare the abomasal lymph node transcriptome of resistant and susceptible lambs in order to determine biological processes differentially expressed between resistant and susceptible individuals. Scottish Blackface lambs, with divergent phenotypes for resistance, were challenged with 30,000 Teladorsagia circumcincta larvae (L3), and abomasal lymph nodes recovered at 7 and 14days post-infection (dpi). High-throughput sequencing of cDNA from the abomasal lymph node was used to quantitatively sample the transcriptome with an average of 32 million reads per sample. A total of 194 and 144 genes were differentially expressed between resistant and susceptible lambs at 7 and 14 dpi respectively. Differentially expressed networks and biological processes were identified using Ingenuity Pathway Analysis. Genes involved in the inflammatory response, attraction of T lymphocytes and binding of leukocytes were more highly expressed in resistant animals at 7 dpi and in susceptible animals at 14 dpi indicating that resistant animals respond to infection earlier than susceptible animals. Twenty-four Single Nucleotide Polymorphisms (SNP) within 11 differentially expressed genes, were tested for association with gastrointestinal nematode resistance in the Scottish Blackface lambs. Four SNP, in 2 genes (SLC30A2 and ALB), were suggestively associated with faecal egg count. In conclusion, a large number of genes were differentially expressed in the abomasal lymph node of resistant and susceptible lambs responding to gastrointestinal nematode challenge. Resistant Scottish Blackface lambs appear to generate an earlier immune response to T. circumcincta. In susceptible lambs this response appears to be delayed. SNP in 2 differentially expressed genes were suggestively associated with faecal egg count indicating that differentially expressed genes may be considered candidate loci for mediating nematode resistance.

Design and evaluation of novel interferon lambda analogs with enhanced antiviral activity and improved drug attributes

Type III interferons (IFNs) (also called IFN-λ: IFN-λ1, IFN-λ2, IFN-λ3, and IFN-λ4) are critical players in the defense against viral infection of mucosal epithelial cells, where the activity of type I IFNs is weak, and unlike type I IFNs that are associated with severe and diverse side effects, type III IFNs cause minimal side effects due to the highly restricted expression of their receptors, and thus appear to be promising agents for the treatment and prevention of respiratory and gastrointestinal viral infection. However, the antiviral potency of natural type III IFNs is weak compared to type I and, although IFN-λ3 possesses the highest bioactivity among the type III IFNs, IFN-λ1, instead of IFN-λ3, is being developed as a therapeutic drug due to the difficulty to express IFN-λ3 in the prokaryotic expression system. Here, to develop optimal IFN-λ molecules with improved drug attributes, we designed a series of IFN-λ analogs by replacing critical amino acids of IFN-λ1 with the IFN-λ3 counterparts, and vice versa. Four of the designed analogs were successfully expressed in Escherichia coli with high yield and were easily purified from inclusion bodies. Interestingly, all four analogs showed potent activity in inducing the expression of the antiviral genes MxA and OAS and two of them, analog-6 and -7, displayed an unexpected high potency that is higher than that of type I IFN (IFN-α2a) in activating the IFN-stimulated response element (ISRE)-luciferase reporter. Importantly, both analog-6 and -7 effectively inhibited replication of hepatitis C virus in Huh-7.5.1 cells, with an IC50 that is comparable to that of IFN-α2a; and consistent with the roles of IFN-λ in mucosal epithelia, both analogs potently inhibited replication of H3N2 influenza A virus in A549 cells. Together, these studies identified two IFN-λ analogs as candidates to be developed as novel antiviral biologics.

IL28B gene polymorphisms and Th1/Th2 cytokine levels might be associated with HTLV-associated arthropathy

The present study is the first investigation of the association between single nucleotide polymorphisms (SNPs - rs8099917, rs12979860 and rs8103142) of the IL28B gene and the development of human T-lymphotropic virus (HTLV)-associated arthropathy (HAA). Individuals with HAA exhibited low interleukin (IL) 6 (p<0.05) and high IL-10 (p<0.05) levels compared with asymptomatic patients. TNF-α/CD4(+) T cell count, TNF-α/CD8(+) T cell count and IFN-γ/proviral load positively correlated in asymptomatic patients. The allelic and genotypic frequencies did not differ between patients with HAA and asymptomatic patients. Seven haplotypes were detected in the investigated population, with haplotype CCT (p<0.05) being the most frequent among the HTLV-infected individuals, while haplotype TTG (p<0.05) was detected in the group with HAA only. Compared with asymptomatic patients, individuals with HAA and genotype TT (rs8099917) exhibited larger numbers of CD8(+) T cells (p<0.05) and higher proviral load levels (p<0.05). Those patients with HAA and genotypes CC (rs12979860) and TT (rs8103142) exhibited high TNF-β (p<0.05) and IFN-γ (p<0.05) levels. Those patients with HAA and genotype CT/TT (rs12979860) exhibited high IL-10 levels (p<0.05). These results suggest that haplotypes CCT and TTG might be associated with susceptibility to HTLV infection and progression to HAA, respectively. Genotype TT (rs8099917) might be a risk factor for elevation of the proviral load and CD8(+) T cell count. In addition, genotypes CC (rs12979860) and TT (rs8103142) seem to be associated with increased TNF-β and IFN-γ levels.

Type I, II, and III Interferons: Regulating Immunity to Mycobacterium tuberculosis Infection

Interferons (IFNs) are cytokines released by host cells in response to the presence of pathogens or tumor cells. The aim of this review was to present the previously known and new findings about the role of interferons type I and II, and recently discovered type III in Mycobacterium tuberculosis (M. tuberculosis) infection control. Infection of various cell types with M. tuberculosis induce both IFN-α and IFN-β synthesis. The majority of the studies support the findings that IFN type I actually promotes infection with M. tuberculosis. It has been well establish that IFN-γ has protective function against M. tuberculosis and the other mycobacteria and that the primary source of this cytokine are CD4(+) and CD8(+) T cells. Recently, it has been shown that also the innate lymphocytes, γδ T cells, natural killer (NK) T cells, and NK cells can also be the source of IFN-γ in response to mycobacterial infection. Several studies have shown that CD4(+) T cells protect mice against M. tuberculosis independently of IFN-γ. The balance between IFN-γ and different cytokines such as IL-10 and other Th2 cell cytokines is likely to influence disease outcome. Type I IFN appears to be detrimental through at least three separate, but overlapping, type I IFN-mediated mechanisms: induction of excessive apoptosis, specific suppression of Th1 and IFN-γ responses, and dampening of the immune response by strong IL-10 induction. Recently it has been found that M. tuberculosis infection in A549 lung epithelial cells stimulate up-regulation of IFN-λ genes in vitro. IFN-λs also have a role in modulation of Th1/Th2 response. IFN-λs are not essential for M. tuberculosis infection control, but can give some contribution in immune response to this pathogen.

Interferon-λ: Immune Functions at Barrier Surfaces and Beyond

When type III interferon (IFN-λ; also known as interleukin-28 [IL-28] and IL-29) was discovered in 2003, its antiviral function was expected to be analogous to that of type I IFNs (IFN-α and IFN-β) via the induction of IFN-stimulated genes (ISGs). Although IFN-λ stimulates expression of antiviral ISGs preferentially in cells of epithelial origin, recent studies have defined additional antiviral mechanisms in other cell types and tissues. Viral infection models using mice lacking IFN-λ signaling and SNP associations with human disease have expanded our understanding of the contribution of IFN-λ to the antiviral response at anatomic barriers and the immune response beyond these barriers. In this review, we highlight recent insights into IFN-λ functions, including its ability to restrict virus spread into the brain and to clear chronic viral infections in the gastrointestinal tract. We also discuss how IFN-λ modulates innate and adaptive immunity, autoimmunity, and tumor progression and its possible therapeutic applications in human disease.

Interferons and systemic sclerosis: correlation between interferon gamma and interferon-lambda 1 (IL-29)

BACKGROUND

Interferon (IFN)-λ1 is a newly described cytokine, member of type III interferons family, which is known for its antiviral, anti-proliferative and antitumor activity. Recent studies indicated that this cytokine has also immune-regulatory function, but its role in the pathogenesis of autoimmune diseases is not established yet. We evaluated serum levels of IFN-λ1 in systemic sclerosis (SSc) patients and healthy controls and its association with IFN-γ and clinical manifestations.

METHODS

IFN-λ1 and IFN-γ serum levels were measured by ELISA from 52 patients with SSc and 53 healthy controls. Association of cytokines serum levels was sought with clinical parameters.

RESULTS

IFN-λ1 and IFN-γ levels in SSc patients were significantly higher than those in healthy individuals (24.82 ± 8.78 and 11.04 ± 3.04 pg/ml, p < 0.0001; 34.11 ± 8.11 and 10.73 ± 2.77 pg/ml, p < 0.0001, respectively). We found a positive correlation between IFN-λ1 and IFN-γ levels in SSc patients (p = 0.0103, r = 0.3526). IFN-γ levels were associated with muscle involvement (p = 0.0483).

CONCLUSION

We first showed raised IFN-λ1 levels in SSc patients. Furthermore, we found a correlation between IFN-λ1 and IFN-γ levels and an association between IFN-γ and myositis. Additional in vitro and in vivo studies are needed to understand IFN-λ1 role in SSc.

Interleukin-28A enhances autoimmune disease in a retinal autoimmunity model

Interleukin-28A (IL-28A), a member of type III interferons (IFN-λs), promotes antiviral, antitumor and immune responses. However, its ability to regulate autoimmune diseases is poorly understood. In this study, we examined the effect of IL-28A on retinal antigen-induced experimental autoimmune uveoretinitis (EAU), a mouse model of human T-cell-mediated autoimmune eye disease. We found that administration of IL-28A enhanced EAU scores and autoimmune response parameters including delayed-type hypersensitivity (DTH), Ag-specific T cell proliferation and the production of Ag-specific IL-17 and IFN-γ in the priming phase. The effect of IL-28A was abrogated by administration of a neutralizing antibody against IL-28A. Our results suggest that IL-28A is capable of exacerbating a T-cell-mediated autoimmune disease. Thus, targeting IL-28A may provide a new therapeutic approach to T cell-mediated autoimmune diseases such as uveitis.

Interferon lambda-2 levels in sputum of patients with pulmonary Mycobacterium tuberculosis infection

In humans, there are three members of type III interferon family, designated as IFN-λ1 (IL-29), IFN-λ2 (IL-28A) and IFN-λ3 (IL-28B). Bacterial infections, including Mycobacterium tuberculosis infection, trigger the expression of interferon I and II genes, but little is known about their effect on IFN-λ genes. It has been found that M. tuberculosis infection in A549 lung epithelial cells stimulate upregulation of IFN-λ2 genes in vitro. The aim of this study was to determine the IFN-λ2 levels in sputum of patients with active pulmonary tuberculosis comparing with levels in healthy persons sputum and sputum of persons with latent tuberculosis. IFN-λ2 level in the samples was quantified with sandwich enzyme-linked immunoassay kit for quantization of human IFN-λ2 (IL-28A). The IFN-λ2 level in sputum of patients with pulmonary tuberculosis was significantly higher comparing with IFN-λ2 levels in healthy group (P = 0.001) and latent tuberculosis group (P = 0.005). Logistic regression analysis has shown that IFN-λ2 level in sputum is related to culture result (OR = 4.14; 95% CI = 1.28-17.5; P = 0.019). There was the correlation between Bartlett score and IFN-λ2 levels in group with pulmonary tuberculosis (r = 0.641; P < 0.01). In conclusion, we have found that the inflammatory cells in sputum can be source of IFN-λ after receptor stimulation by M. tuberculosis components.

Interleukin-28A promotes IFN-γ production by peripheral blood mononuclear cells from patients with Behçet's disease

Behçet's disease (BD) is an autoimmune disease of unknown etiology. Interleukin-28A (IL-28A) promotes immune responses and may participate in the pathogenesis of autoimmune diseases. To examine the role of IL-28A in the pathogenesis of BD, we measured the expression of IFN-γ and IL-17 by IL-28A-stimulated peripheral blood mononuclear cells (PBMCs) from 19 patients with BD and 16 healthy individuals. We found that IFN-γ and IL-17 were undetectable in the sera from BD patients and control subjects. The mRNA expression and protein production of IFN-γ by IL-28A-stimulated PBMCs from BD patients were significantly increased compared to healthy individuals. No significant difference was observed in the mRNA expression and protein production of IL-17 by IL-28A-stimulated PBMCs between BD patients and normal individuals.

The impact of the interferon-lambda family on the innate and adaptive immune response to viral infections

Type-III interferons (IFN-λ, IFNL) are the most recently described family of IFNs. This family of innate cytokines are increasingly being ascribed pivotal roles in host-pathogen interactions. Herein, we will review the accumulating evidence detailing the immune biology of IFNL during viral infection, and the implications of this novel information on means to advance the development of therapies and vaccines against existing and emerging pathogens. IFNLs exert antiviral effects via induction of IFN-stimulated genes. Common single nucleotide polymorphisms (SNPs) in the IFNL3, IFNL4 and the IFNL receptor α-subunit genes have been strongly associated with IFN-α-based treatment of chronic hepatitis C virus infection. The clinical impact of these SNPs may be dependent on the status of viral infection (acute or chronic) and the potential to develop viral resistance. Another important function of IFNLs is macrophage and dendritic cell polarization, which prime helper T-cell activation and proliferation. It has been demonstrated that IFNL increase Th1- and reduce Th2-cytokines. Therefore, can such SNPs affect the IFNL signaling and thereby modulate the Th1/Th2 balance during infection? In turn, this may influence the subsequent priming of cytotoxic T cells versus antibody-secreting B cells, with implications for the breadth and durability of the host response.

Borrelia burgdorferi RNA induces type I and III interferons via Toll-like receptor 7 and contributes to production of NF-κB-dependent cytokines

Borrelia burgdorferi elicits a potent cytokine response through activation of multiple signaling receptors on innate immune cells. Spirochetal lipoproteins initiate expression of NF-κB-dependent cytokines primarily via TLR2, whereas type I interferon (IFN) production is induced through the endosomal receptors TLR7 and TLR9 in human dendritic cells and TLR8 in monocytes. We demonstrate that DNA and RNA are the B. burgdorferi components that initiate a type I IFN response by human peripheral blood mononuclear cells (PBMCs). IFN-α protein and transcripts for IRF7, MX1, and OAS1 were induced by endosomal delivery of B. burgdorferi DNA, RNA, or whole-cell lysate, but not by lysate that had been treated with DNase and RNase. Induction of IFN-α and IFN-λ1, a type III IFN, by B. burgdorferi RNA or live spirochetes required TLR7-dependent signaling and correlated with significantly enhanced transcription and expression of IRF7 but not IRF3. Induction of type I and type III IFNs by B. burgdorferi RNA could be completely abrogated by a TLR7 inhibitor, IRS661. In addition to type I and type III IFNs, B. burgdorferi RNA contributed to the production of the NF-κB-dependent cytokines, IFN-γ, interleukin-10 (IL-10), IL-1β, IL-6, and tumor necrosis factor alpha (TNF-α), by human PBMCs. Collectively, these data indicate that TLR7-dependent recognition of RNA is pivotal for IFN-α and IFN-λ1 production by human PBMCs, and that RNA-initiated signaling contributes to full potentiation of the cytokine response generated during B. burgdorferi infection.

Regulation of interferon lambda-1 (IFNL1/IFN-λ1/IL-29) expression in human colon epithelial cells

The efficient regulation of intestinal immune responses is critical to colon health. Viruses, for example noraviruses, are key pathogens of the intestine. The lambda interferons (comprising three ligands: IFNL1, L2 and L3 - the so-called "Type III" interferons) constitute the most recently discovered IFN family and are known to be important in intestinal anti-viral defense. A fourth family member, IFNL4, was recently described. Expression of the IFN-lambda receptor is restricted to epithelial and immune cells; together, these ligands and their receptor represent an important anti-viral and immunoregulatory component of the immune/epithelial inteface. We investigated control of IFNL1 expression in human colon epithelial cells. We used the TLR3 agonist poly I:C to drive expression of IFNL1 in SW480 cells, and small interfering RNA (siRNA) to knockdown target transcription factors. We identified ZEB1 and BLIMP-1 as transcription factors that strongly inhibited IFNL1 expression in SW480 cells. Interestingly, while BLIMP-1 inhibited both type-III and type-I interferons (IFN-β), the inhibitory action of ZEB1 was specific for IFNL1. We also defined the NF-κB family member, p65 as a key activator of IFNL1 and NF-κB p50 as a key inhibitor. Finally, we demonstrated that siRNA targeting of ZEB1 or NF-κB p50 resulted in a significant elevation of secreted IFN-λ1 protein and expression of the anti-viral gene OAS1, while knockdown of p65 inhibited these events. Our data provide insight to the regulation of IFNL1 expression in the human colon and suggest novel therapeutic approaches to elevate IFNλ-1 protein where required.

Bacterial pathogens activate a common inflammatory pathway through IFNλ regulation of PDCD4

The type III interferon (IFNλ) receptor IL-28R is abundantly expressed in the respiratory tract and has been shown essential for host defense against some viral pathogens, however no data are available concerning its role in the innate immune response to bacterial pathogens. Staphylococcus aureus and Pseudomonas aeruginosa induced significant production of IFNλ in the lung, and clearance of these bacteria from the lung was significantly increased in IL-28R null mice compared to controls. Improved bacterial clearance correlated with reduced lung pathology and a reduced ratio of pro- vs anti-inflammatory cytokines in the airway. In human epithelial cells IFNλ inhibited miR-21 via STAT3 resulting in upregulation of PDCD4, a protein known to promote inflammatory signaling. In vivo 18 hours following infection with either pathogen, miR-21 was significantly reduced and PDCD4 increased in the lungs of wild type compared to IL-28R null mice. Infection of PDCD4 null mice with USA300 resulted in improved clearance, reduced pathology, and reduced inflammatory cytokine production. These data suggest that during bacterial pneumonia IFNλ promotes inflammation by inhibiting miR-21 regulation of PDCD4.

The role of interferons (types I, II, and III) in viral and bacterial infections has been a topic of intense research over the last decade. The contribution of the type I interferons during bacterial pneumonias particularly has been shown to be highly variable depending on the specific pathogen. Our data for the first time demonstrate that type III interferon plays a significant role in the pathogenesis of bacterial pneumonia, and its contribution is similar in both Gram positive and Gram negative infections. We show in epithelial cells that miR-21 and PDCD4 are downstream effectors of type III interferon that prolong production of inflammatory cytokines. Utilizing mice that lack the receptor for type III interferon or PDCD4, we show that inhibiting this pathway improves bacterial clearance from the airways and lung tissue. These data suggest novel targets for therapy in a variety of bacterial pneumonias.

Role of IL28B gene polymorphism and cell-mediated immunity in spontaneous resolution of acute hepatitis C

BACKGROUND

 A single-nucleotide polymorphism (SNP; rs12979860) near the IL28B gene has been associated with spontaneous and treatment-induced hepatitis C virus clearance. We investigated predictors of spontaneous disease resolution in a cohort of patients with acute hepatitis C (AHC), analyzing epidemiological, clinical and virological parameters together with IL28B.rs12979860 genotypes and cell-mediated immunity (CMI).

METHODS

 Fifty-six symptomatic AHC patients were enrolled and followed prospectively. CMI was measured in 31 patients at multiple time points by interferon-γ enzyme-linked immunospot assay and was correlated to the IL28B.rs12979860 SNP.

RESULTS

 Eighteen patients had a self-limiting AHC that was associated with female sex (P = .028), older age (P = .018), alanine aminotransferase level >1000 U/L (P = .027), total bilirubin level >7 mg/dL (P = .036), and IL28B.rs12979860 genotype CC (P = .030). In multivariate analysis, only CC genotype was independently associated with self-limiting AHC (odds ratio, 5.3; 95% confidence interval, 1.1-26.5). Patients with the CC genotype with self-limiting AHC had a stronger (P = .02) and broader (P = .013) CMI than patients with the CT genotype with chronically evolving AHC. In patients with chronically evolving disease, CC genotype was associated with a broader CMI compared to CT genotype (P = .028). A negative CMI was more frequently associated with CT genotype among persistently infected patients (P = .043) and with persistent infection among CT patients (P = .033).

CONCLUSIONS

. Self-limiting AHC was independently associated with CC genotype. The correlation between IL28B.rs12979860 genotypes and CMI is suggestive of a possible important role of CMI in favoring hepatitis C virus clearance in CC patients.

Interleukin-28B polymorphism in hepatitis C and liver transplantation

The discovery of interleukin-28B (IL-28B) single-nucleotide polymorphisms has opened an important new area of research in liver transplantation (LT) for hepatitis C virus (HCV). Both recipient- and donor-derived IL-28B genotypes affect the post-LT treatment response, with sustained virological response (SVR) rates oscillating from >50% in homozygotes for the favorable allele (up to 90% when this is present in both the recipient and the donor) to <15% in homozygotes for the unfavorable allele and from 30% to 50% in heterozygotes. Other key posttransplant outcomes affected by the IL-28B genotype are the time to histological recurrence, HCV RNA and alanine aminotransferase levels, histological variables (including the rate of fibrosis progression), and hepatocellular carcinoma. Interactions between donor and recipient IL-28B genotypes are complex and may affect outcomes not directly related to HCV infections, such as acute cellular rejection (ACR) and metabolic diseases. A preferential allocation system in which livers from donors homozygous for the favorable allele are given to HCV patients might be postulated to improve SVR rates and post-LT outcomes in recipients with HCV infections (a 25% increase in SVR and an 8% decrease in mortality at 5 years). Although negative effects from this are difficult to predict, they could include an accelerated progression of fibrosis in patients with failed HCV eradication and an increase in ACR in non-HCV patients. Our knowledge of the precise role of IL-28B genotypes in the course of post-LT HCV is evolving, but existing knowledge suggests the possibility of exploring strategies that use IL-28B genotyping to reduce the impact of post-LT adverse outcomes.

Interferon-λs: special immunomodulatory agents and potential therapeutic targets

Interferon (IFN)-λs are a new addition to the old IFN family and share many similarities, such as antiviral and antiproliferative characteristics, with type I IFNs. IFN-λs also exhibit unique characteristics in immunomodulation. Accumulating studies have indicated the interactions between IFN-λs and immune cells, which lead to the regulation of the latter. IFN-λs can influence dendritic cells (DCs) and their product, IFN-λs-DCs, can then regulate the function of T cells. On the other hand, IFN-λs can also directly affect T cells through inhibition of the T helper 2 cell (Th2) responses. IFN-λs have varying immunomodulatory functions under different physiological conditions or in different organs and can inhibit tumor growth via regulation of the immune system. Diseases associated with IFN-λs include asthma, allergy, and systemic lupus erythematosus. In this review, we summarize the current knowledge of the biology of IFN-λs and their immunomodulatory function in relevant human diseases.

The course of posttransplant hepatitis C infection: comparative impact of donor and recipient source of the favorable IL28B genotype and other variables

BACKGROUND AND AIMS

The IL28B genotype has been linked to sustained virological response (SVR) in hepatitis C virus (HCV). Its role on disease biology and progression is less clear. We characterized the effects of IL28B genotype on HCV recurrence, allograft histology, rate of SVR, and survival after liver transplantation (LT) in HCV.

METHODS

Consecutive patients who underwent LT with HCV were studied. The rs12979860 genotype from both the donor was and recipient was determined. Measured endpoints included histologic HCV recurrence (inflammatory grade and fibrosis stage), acute cellular rejection, SVR, retransplantation, and death.

RESULTS

The study cohort comprised 272 consecutive LT in 255 patients. C-allele frequency was 56% in recipients and 70% in donors (P<0.001). Recipient IL28B CC genotype was associated with lower alanine aminotransferase levels and viral load at recurrence and a lower frequency of F≥2 on liver biopsy at 1 year after LT, when compared with the non-CC genotype (P=0.012). The opposite was observed in LT with donor CC genotype (P=0.003). Both recipient and donor CC genotype favored SVR, and when the two of them occurred together, the SVR rate reached 90%. Survival analysis after 5.5 years of follow-up showed a higher rate of progression to cirrhosis (hazard ratio, 5.96; 95% confidence interval, 1.29-27.6), liver-related death, or retransplantation among liver transplant recipients with a CC genotype donor.

CONCLUSIONS

The IL28B genotype is predictive not only of SVR but also of the histologic diagnosis of posttransplant hepatitis C, with donor CC genotype favoring inflammation and fibrosis, and adverse outcomes during long-term follow-up. A favorable effect of donor CC genotype is manifest only after antiviral therapy.

Activation of type III interferon genes by pathogenic bacteria in infected epithelial cells and mouse placenta

Bacterial infections trigger the expression of type I and II interferon genes but little is known about their effect on type III interferon (IFN-λ) genes, whose products play important roles in epithelial innate immunity against viruses. Here, we studied the expression of IFN-λ genes in cultured human epithelial cells infected with different pathogenic bacteria and in the mouse placenta infected with Listeria monocytogenes. We first showed that in intestinal LoVo cells, induction of IFN-λ genes by L. monocytogenes required bacterial entry and increased further during the bacterial intracellular phase of infection. Other Gram-positive bacteria, Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis, also induced IFN-λ genes when internalized by LoVo cells. In contrast, Gram-negative bacteria Salmonella enterica serovar Typhimurium, Shigella flexneri and Chlamydia trachomatis did not substantially induce IFN-λ. We also found that IFN-λ genes were up-regulated in A549 lung epithelial cells infected with Mycobacterium tuberculosis and in HepG2 hepatocytes and BeWo trophoblastic cells infected with L. monocytogenes. In a humanized mouse line permissive to fetoplacental listeriosis, IFN-λ2/λ3 mRNA levels were enhanced in placentas infected with L. monocytogenes. In addition, the feto-placental tissue was responsive to IFN-λ2. Together, these results suggest that IFN-λ may be an important modulator of the immune response to Gram-positive intracellular bacteria in epithelial tissues.

Induction of type I interferon signaling by Pseudomonas aeruginosa is diminished in cystic fibrosis epithelial cells

The clinical manifestations of infection in cystic fibrosis (CF) are restricted to the lung, and involve a limited number of pathogens, suggesting a specific defect in mucosal immunity. We postulated that cystic fibrosis transmembrane conductance regulator (CTFR) mutations could affect the activation of type I interferon signaling in airway epithelial cells, which function in immune surveillance and initiate the recruitment and activation of immune cells. In response to infection with Pseudomonas aeruginosa, Ifnb was induced more than 100-fold in the murine lung, and the phosphorylation of STAT1 was similarly induced by the expected TLR4/TRIF/MD2/TBK1 cascade. The stimulation by P. aeruginosa of CF (IB3) cells and control (C-38) human cell lines similarly resulted in the induction of IFN-β, but to a significantly lower extent in CF airway cells. The potential consequences of diminished type I IFN signaling were demonstrated in a murine model of P. aeruginosa pneumonia, pretreatment with polyinosinic:polycytidylic acid significantly enhanced bacterial clearance and correlated with increased numbers of mature CD11c(+)/CD86(+) dendritic cells (DCs) in the lung. Using culture supernatants from CF or control cell lines stimulated with P. aeruginosa, we similarly demonstrated the diminished activation of human monocyte-derived DCs by incubation with CF compared with normal epithelial cell culture supernatants, which was dependent on IFN-β. These observations suggest that dysfunction of the CFTR in airway epithelial cells may contribute to impaired immune surveillance in the CF airway and resultant colonization by P. aeruginosa.

Regulation of IFN-λ1 promoter activity (IFN-λ1/IL-29) in human airway epithelial cells

The type III (λ) IFNs (IFN-λ1, IFN-λ2, and IFN-λ3) and their receptor are the most recently discovered IFN family. They are induced by viruses and mediate antiviral activity, but type III IFNs have an important, specific functional niche at the immune/epithelial interface, as well as in the regulation of Th2 cytokines. Their expression appears diminished in bronchial epithelial cells of rhinovirus-infected asthmatic individuals. We investigated the regulation of IFN-λ1 expression in human airway epithelial cells using reporter genes analysis, chromatin immunoprecipitation, small interfering RNA knockdown, and DNase footprinting. In this article, we define the c-REL/p65 NF-κB heterodimer and IRF-1 as key transcriptional activators and ZEB1, B lymphocyte-induced maturation protein 1, and the p50 NF-κB homodimer as key repressors of the IFN-λ1 gene. We further show that ZEB1 selectively regulates type III IFNs. To our knowledge, this study presents the first characterization of any type III IFN promoter in its native context and conformation in epithelial cells and can now be applied to understanding pathogenic dysregulation of IFN-λ1 in human disease.

A bacterial protein targets the BAHD1 chromatin complex to stimulate type III interferon response

Intracellular pathogens such as Listeria monocytogenes subvert cellular functions through the interaction of bacterial effectors with host components. Here we found that a secreted listerial virulence factor, LntA, could target the chromatin repressor BAHD1 in the host cell nucleus to activate interferon (IFN)-stimulated genes (ISGs). IFN-λ expression was induced in response to infection of epithelial cells with bacteria lacking LntA; however, the BAHD1-chromatin associated complex repressed downstream ISGs. In contrast, in cells infected with lntA-expressing bacteria, LntA prevented BAHD1 recruitment to ISGs and stimulated their expression. Murine listeriosis decreased in BAHD1(+/-) mice or when lntA was constitutively expressed. Thus, the LntA-BAHD1 interplay may modulate IFN-λ-mediated immune response to control bacterial colonization of the host.