The structure of human interferon lambda and what it has taught us

Interferon-Regulated Expression of Cellular Splicing Factors Modulates Multiple Levels of HIV-1 Gene Expression and Replication

Type I interferons (IFN-Is) are pivotal in innate immunity against human immunodeficiency virus I (HIV-1) by eliciting the expression of IFN-stimulated genes (ISGs), which encompass potent host restriction factors. While ISGs restrict the viral replication within the host cell by targeting various stages of the viral life cycle, the lesser-known IFN-repressed genes (IRepGs), including RNA-binding proteins (RBPs), affect the viral replication by altering the expression of the host dependency factors that are essential for efficient HIV-1 gene expression. Both the host restriction and dependency factors determine the viral replication efficiency; however, the understanding of the IRepGs implicated in HIV-1 infection remains greatly limited at present. This review provides a comprehensive overview of the current understanding regarding the impact of the RNA-binding protein families, specifically the two families of splicing-associated proteins SRSF and hnRNP, on HIV-1 gene expression and viral replication. Since the recent findings show specifically that SRSF1 and hnRNP A0 are regulated by IFN-I in various cell lines and primary cells, including intestinal lamina propria mononuclear cells (LPMCs) and peripheral blood mononuclear cells (PBMCs), we particularly discuss their role in the context of the innate immunity affecting HIV-1 replication.

The Role of Structure in the Biology of Interferon Signaling

Interferons (IFNs) are a family of cytokines with the unique ability to induce cell intrinsic programs that enhance resistance to viral infection. Induction of an antiviral state at the cell, tissue, organ, and organismal level is performed by three distinct IFN families, designated as Type-I, Type-II, and Type-III IFNs. Overall, there are 21 human IFNs, (16 type-I, 12 IFNαs, IFNβ, IFNϵ, IFNκ, and IFNω; 1 type-II, IFNγ; and 4 type-III, IFNλ1, IFNλ2, IFNλ3, and IFNλ4), that induce pleotropic cellular activities essential for innate and adaptive immune responses against virus and other pathogens. IFN signaling is initiated by binding to distinct heterodimeric receptor complexes. The three-dimensional structures of the type-I (IFNα/IFNAR1/IFNAR2), type-II (IFNγ/IFNGR1/IFNGR2), and type-III (IFNλ3/IFNλR1/IL10R2) signaling complexes have been determined. Here, we highlight similar and unique features of the IFNs, their cell surface complexes and discuss their role in inducing downstream IFN signaling responses.

The Arabian camel, Camelus dromedarius interferon epsilon: Functional expression, in vitro refolding, purification and cytotoxicity on breast cancer cell lines

The current study highlights, for the first time, cloning, overexpression and purification of the novel interferon epsilon (IFNƐ), from the Arabian camel Camelus dromedaries. The study then assesses the cytotoxicity of IFNε against two human breast cancer cell lines MDA-MB-231 and MCF-7. Full-length cDNA encoding interferon epsilon (IFNε) was isolated and cloned from the liver of the Arabian camel, C. dromedarius using reverse transcription-polymerase chain reaction. The sequence analysis of the camel IFNε cDNA showed a 582-bp open reading frame encoding a protein of 193 amino acids with an estimated molecular weight of 21.230 kDa. A BLAST search analysis revealed that the C. dromedarius IFNε shared high sequence identity with the IFN genes of other species, such as Camelus ferus, Vicugna pacos, and Homo sapiens. Expression of the camel IFNε cDNA in Escherichia coli gave a fusion protein band of 24.97 kDa after induction with either isopropyl β-D-1-thiogalactopyranoside or lactose for 5 h. Recombinant IFNε protein was overexpressed in the form of inclusion bodies that were easily solubilized and refolded using SDS and KCl. The solubilized inclusion bodies were purified to apparent homogeneity using nickel affinity chromatography. We examined the effect of IFNε on two breast cancer cell lines MDA-MB-231 and MCF-7. In both cell lines, IFNε inhibited cell survival in a dose dependent manner as observed by MTT assay, morphological changes and apoptosis assay. Caspase-3 expression level was found to be increased in MDA-MB-231 treated cells as compared to untreated cells.

Discovery of All Three Types in Cartilaginous Fishes Enables Phylogenetic Resolution of the Origins and Evolution of Interferons

Interferons orchestrate host antiviral responses in jawed vertebrates. They are categorized into three classes; IFN1 and IFN3 are the primary antiviral cytokine lineages, while IFN2 responds to a broader variety of pathogens. The evolutionary relationships within and between these three classes have proven difficult to resolve. Here, we reassess interferon evolution, considering key phylogenetic pitfalls including taxon sampling, alignment quality, model adequacy, and outgroup choice. We reveal that cartilaginous fishes, and hence the jawed vertebrate ancestor, possess(ed) orthologs of all three interferon classes. We show that IFN3 groups sister to IFN1, resolve the origins of the human IFN3 lineages, and find that intronless IFN3s emerged at least three times. IFN2 genes are highly conserved, except for IFN-γ-rel, which we confirm resulted from a teleost-specific duplication. Our analyses show that IFN1 phylogeny is highly sensitive to phylogenetic error. By accounting for this, we describe a new backbone IFN1 phylogeny that implies several IFN1 genes existed in the jawed vertebrate ancestor. One of these is represented by the intronless IFN1s of tetrapods, including mammalian-like repertoires of reptile IFN1s and a subset of amphibian IFN1s, in addition to newly-identified intron-containing shark IFN1 genes. IFN-f, previously only found in teleosts, likely represents another ancestral jawed vertebrate IFN1 family member, suggesting the current classification of fish IFN1s into two groups based on the number of cysteines may need revision. The providence of the remaining fish IFN1s and the coelacanth IFN1s proved difficult to resolve, but they may also be ancestral jawed vertebrate IFN1 lineages. Finally, a large group of amphibian-specific IFN1s falls sister to all other IFN1s and was likely also present in the jawed vertebrate ancestor. Our results verify that intronless IFN1s have evolved multiple times in amphibians and indicate that no one-to-one orthology exists between mammal and reptile IFN1s. Our data also imply that diversification of the multiple IFN1s present in the jawed vertebrate ancestor has occurred through a rapid birth-death process, consistent with functional maintenance over a 450-million-year host-pathogen arms race. In summary, this study reveals a new model of interferon evolution important to our understanding of jawed vertebrate antiviral immunity.

Interferon-Inducible Myxovirus Resistance Proteins: Potential Biomarkers for Differentiating Viral from Bacterial Infections

BACKGROUND

In 2015, the 68th World Health Assembly declared that effective, rapid, low-cost diagnostic tools were needed for guiding optimal use of antibiotics in medicine. This review is devoted to interferon-inducible myxovirus resistance proteins as potential biomarkers for differentiating viral from bacterial infections.

CONTENT

After viral infection, a branch of the interferon (IFN)-induced molecular reactions is triggered by the binding of IFNs with their receptors, a process leading to the activation of mx1 and mx2, which produce antiviral Mx proteins (MxA and MxB). We summarize current knowledge of the structures and functions of type I and III IFNs. Antiviral mechanisms of Mx proteins are discussed in reference to their structural and functional data to provide an in-depth picture of protection against viral attacks. Knowing such a mechanism may allow the development of countermeasures and the specific detection of any viral infection. Clinical research data indicate that Mx proteins are biomarkers for many virus infections, with some exceptions, whereas C-reactive protein (CRP) and procalcitonin have established positions as general biomarkers for bacterial infections.

SUMMARY

Mx genes are not directly induced by viruses and are not expressed constitutively; their expression strictly depends on IFN signaling. MxA protein production in peripheral blood cells has been shown to be a clinically sensitive and specific marker for viral infection. Viral infections specifically increase MxA concentrations, whereas viruses have only a modest increase in CRP or procalcitonin concentrations. Therefore, comparison of MxA and CRP and/or procalcitonin values can be used for the differentiation of infectious etiology.

Species Specificity of Type III Interferon Activity and Development of a Sensitive Luciferase-Based Bioassay for Quantitation of Mouse Interferon-λ

The type III interferon (IFN-λ) family includes 4 IFN-λ subtypes in man. In the mouse, only the genes coding for IFN-λ2 and -λ3 are present. Unlike mouse and human type I IFNs (IFN-α/β), which exhibit strong species specificity, type III IFNs were reported to act in a cross-specific manner. We reexamined the cross-specificity and observed that mouse and human IFN-λ exhibit some species specificity, although much less than type I IFNs. Mouse IFN-λ3 displayed clear species specificity, being 25-fold less active in human cells than the closely related mouse IFN-λ2. This specificity likely depends on amino acids in α helices A and F that diverged from other IFN-λ sequences. Human IFN-λ4, in contrast, retained high activity in mouse cells. We next developed a firefly luciferase-based reporter cell line, named Fawa-λ-luc, to detect IFN-λ in biological fluids with high specificity and sensitivity. Fawa-λ-luc cells, derived from mouse epithelial cells that are responsive to IFN-λ, were made nonresponsive to type I IFNs by inactivation of the Ifnar2 gene and strongly responsive to IFN-λ by overexpression of the mouse IFNLR1. This bioassay was as sensitive as a commercially available enzyme-linked immunosorbent assay in detecting mouse IFN-λ in cell culture supernatant, as well as in serum and bronchoalveolar lavage samples of virus-infected mice. The assay also enabled the sensitive detection of human IFN-λ activity, including that of the divergent IFN-λ4 with a bias, however, due to variable activity of IFN-λ subtypes.

Interferon-λ3/4 genetic variants and interferon-λ3 serum levels are biomarkers of lupus nephritis and disease activity in Taiwanese

BACKGROUND

Type III interferons (IFNs) or IFN-λs are the newly discovered cytokines that primarily target the cells of epithelial and myeloid lineages, which are major components of kidneys. The current study aimed to investigate whether IFN-λs are involved in the pathogenesis of systemic lupus erythematosus (SLE) and lupus nephritis.

METHODS

TaqMan allele discrimination assays were used to determine IFNL3/4 SNP genotypes of 1620 healthy controls and 1013 SLE patients (two independent cohorts consisting of 831 and 182 subjects, respectively) from Taiwan. The distributions of IFNL3/4 SNP genotypes and allele frequencies were compared between SLE patients and healthy controls and among SLE patients stratified by clinical phenotypes. ELISA was used to determine the serum IFN-λ3 concentrations of SLE patients.

RESULTS

All major IFN3/4 SNP alleles were significantly associated with the risk for lupus nephritis (rs8099917T, PFDR = 0.0021, OR 1.75, 95% CI 1.24-2.47; rs12979860C, PFDR = 0.0034, OR 1.65, 95% CI 1.18-2.30; rs4803217C, PFDR = 0.0021, OR 1.76, 95% CI 1.25-2.48; and ss469415590TT, PFDR = 0.0021, OR 1.73, 95% CI 1.23-2.42) among SLE patients. Similarly, the major IFNL3/4 SNP haplotype rs8099917T-ss469415590TT-rs12979860C-rs4803217C (or T-TT-C-C) was a significant risk factor for lupus nephritis (P = 0.0015, OR 1.68, 95% CI 1.22-2.32). Additionally, all minor IFN3/4 SNP alleles were significantly associated with SLE susceptibility in nephritis-negative SLE patients as compared to normal healthy controls (rs8099917G, PFDR = 0.00177, OR 1.68, 95% CI 1.24-2.28; rs12979860T, PFDR = 0.00299, OR 1.58, 95% CI 1.18-2.32; rs4803217A, PFDR = 0.00176, OR 1.65, 95% CI 1.22-2.23; and ss469415590ΔG, PFDR = 0.00176, OR 1.70, 95% CI 1.26-2.29). Furthermore, the elevated serum levels of IFN-λ3 were significantly correlated with the complement depression and the high SLE disease activities in SLE patients.

CONCLUSIONS

IFN-λ3/4 genetic variants play a unique role in the development of lupus nephritis and SLE.

Outcomes of Congenital Zika Disease Depend on Timing of Infection and Maternal-Fetal Interferon Action

Zika virus (ZIKV) infection during pregnancy in humans results in intrauterine growth restriction, spontaneous abortion, and microcephaly. Here, we found that fetus-derived type I interferon (IFN-I) signaling can enhance anti-ZIKV responses and provide clinical benefits to the fetus. Because IFN-λ shares signaling cascades and antiviral functions with IFN-I, we investigated the in vivo effects of IFN-λ in ZIKV-infected pregnant mice. IFN-λ administration during mid-pregnancy reduced ZIKV burden in maternal and fetal organs and alleviated placental injuries and fetal demise. In addition, prophylactic and therapeutic treatment of IFN-λ1 in a human trophoblast line, as well as in primary human amniotic epithelial cells, greatly reduced the ZIKV burden. Our data highlight IFN-λ1 as a potential therapeutic useful for women at risk for congenital Zika disease.

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.

The Role of Type III Interferons in Hepatitis C Virus Infection and Therapy

The human interferon (IFN) response is a key innate immune mechanism to fight virus infection. IFNs are host-encoded secreted proteins, which induce IFN-stimulated genes (ISGs) with antiviral properties. Among the three classes of IFNs, type III IFNs, also called IFN lambdas (IFNLs), are an essential component of the innate immune response to hepatitis C virus (HCV). In particular, human polymorphisms in IFNL gene loci correlate with hepatitis C disease progression and with treatment response. To date, the underlying mechanisms remain mostly elusive; however it seems clear that viral infection of the liver induces IFNL responses. As IFNL receptors show a more restricted tissue expression than receptors for other classes of IFNs, IFNL treatment has reduced side effects compared to the classical type I IFN treatment. In HCV therapy, however, IFNL will likely not play an important role as highly effective direct acting antivirals (DAA) exist. Here, we will review our current knowledge on IFNL gene expression, protein properties, signaling, ISG induction, and its implications on HCV infection and treatment. Finally, we will discuss the lessons learnt from the HCV and IFNL field for virus infections beyond hepatitis C.

An ELISA Based Binding and Competition Method to Rapidly Determine Ligand-receptor Interactions

A comprehensive understanding of signaling pathways requires detailed knowledge regarding ligand-receptor interaction. This article describes two fast and reliable point-by-point protocols of enzyme-linked immunosorbent assays (ELISAs) for the investigation of ligand-receptor interactions: the direct ligand-receptor interaction assay (LRA) and the competition LRA. As a case study, the ELISA based analysis of the interaction between different lambda interferons (IFNLs) and the alpha subunit of their receptor (IL28RA) is presented: the direct LRA is used for the determination of dissociation constants (KD values) between receptor and IFN ligands, and the competition LRA for the determination of the inhibitory capacity of an oligopeptide, which was designed to compete with the IFNLs at their receptor binding site. Analytical steps to estimate KD and half maximal inhibitory concentration (IC50) values are described. Finally, the discussion highlights advantages and disadvantages of the presented method and how the results enable a better molecular understanding of ligand-receptor interactions.

Human Cytokinome Analysis for Interferon Response

Cytokines are a group of small secreted proteins that mediate a diverse range of immune and nonimmune responses to inflammatory and microbial stimuli. Only a few of these cytokines mount an antiviral response, including type I, II, and III interferons (IFNs). During viral infections and under inflammatory conditions, a number of cytokines and chemokines are coproduced with IFN; however, no systematic study exists on the interactions of the cytokine repertoire with the IFN response. Here, we performed the largest cytokine and chemokine screen (the human cytokinome, with >240 members) to investigate their modulation of type I and type II IFN responses in a cell line model. We evaluated the cytokine activities in both IFN-stimulated response element (ISRE) and IFN-γ activation sequence (GAS) reporter systems. Several cytokine clusters that augment either or both ISRE- and GAS-mediated responses to IFNs were derived from the screen. We identified novel modulators of IFN response-betacellulin (BTC), interleukin 11 (IL-11), and IL-17F-that caused time-dependent induction of the IFN response. The ability to induce endogenous IFN-β and IFN-stimulated genes varies among these cytokines and was largely dependent on Stat1, as assessed by Stat1 mutant fibroblasts. Certain cytokines appear to augment the IFN-β response through the NF-κB pathway. The novel IFN-like cytokines augmented the antiviral activity of IFN-α against several RNA viruses, including encephalomyocarditis virus, vesicular stomatitis virus, and influenza virus, in susceptible cell lines. Overall, the study represents a large-scale analysis of cytokines for enhancing the IFN response and identified cytokines capable of enhancing Stat1, IFN-induced gene expression, and antiviral activities.

IMPORTANCE

Innate immunity to viruses is an early defense system to ward off viruses. One mediator is interferon (IFN), which activates a cascade of biochemical events that aim to control the virus life cycle. In our work, we examined more than 200 cytokines, soluble mediators produced within the body as a result of infection, for the ability to enhance IFN action. We identified enhanced interactions with specific IFNs and cytokines. We also revealed that betacellulin, IL-17, and IL-11 cytokines have the novel property of enhancing the antiviral action of IFN against several viruses. These results demonstrate that the human genome codes for previously unknown proteins with unrelated functions that can augment the innate immunity to viruses. Knowing these interactions not only helps our understanding of immunity to viruses and emerging diseases, but can also lead to devising possible new therapeutics by enhancing the mediator of antiviral action itself, IFN.

Comparison of antiviral activity of lambda-interferons against HIV replication in macrophages

Lambda-interferons (IFN-λs) have been demonstrated as having the ability to inhibit HIV replication in macrophages. However, specific differences in signaling transduction and anti-HIV activity in macrophages between different IFN-λs are unclear. Here, we showed that although all 3 members of (IFN-λ1, λ2, and λ3) IFN-λ family induced the expression of a number of genes of janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway in monocyte-derived macrophages, IFN-λ1 or IFN-λ3 induced higher levels of antiviral IFN-stimulated genes (ISGs) expression than did IFN-λ2. In addition, IFN-λ1 or IFN-λ3 induced higher levels of several pattern recognition receptors (PPRs) than did IFN-λ2. Incubation of IFN-λs with HIV-infected macrophages showed that IFN-λ1 or IFN-λ3 is more potent in anti-HIV activity than IFN-λ2. We also showed that IFN-λ treatment before HIV infection was more potent in HIV inhibition than that after HIV infection. Further investigations showed that the inductions of ISGs and PPRs expression by IFN-λs were largely compromised by HIV infection. These findings provide further experimental evidence that IFN-λs have therapeutic potential in treatment of HIV infection.

Interferon lambda: opportunities, risks, and uncertainties in the fight against HCV

Innate immunity is key to the fight against the daily onslaught from viruses that our bodies are subjected to. Essential to this response are the interferons (IFNs) that prime our cells to block viral pathogens. Recent evidence suggests that the Type III (λ) IFNs are intimately associated with the immune response to hepatitis C virus (HCV) infection. Genome-wide association studies have identified polymorphisms within the IFN-λ gene locus that correlate with response to IFNα-based antiviral therapy and with spontaneous clearance of HCV infection. The mechanisms for these correlations are incompletely understood. Restricted expression of the IFN-λ receptor, and the ability of IFN-λ to induce IFN-stimulated genes in HCV-infected cells, suggest potential roles for IFN-λ in HCV therapy even in this era of directly acting antivirals. This review summarizes our current understanding of the IFN-λ family and the role of λ IFNs in the natural history of HCV infection.

Molecular cloning, expression and characterization of Pekin duck interferon-λ

Interferons (IFNs) are the first line of defense against viral infections in vertebrates. Type III interferon (IFN-λ) is recognized for its key role in innate immunity of tissues of epithelial origin. Here we describe the identification of the Pekin duck IFN-λ ortholog (duIFN-λ). The predicted duIFN-λ protein has an amino acid identity of 63%, 38%, 37% and 33% with chicken IFN-λ and human IFN-λ3, IFN-λ2 and IFN-λ1, respectively. The duck genome contains a single IFN-λ gene that is comprised of five exons and four introns. Recombinant duIFN-λ up-regulated OASL and Mx-1 mRNA in primary duck hepatocytes. Our observations suggest evolutionary conservation of genomic organization and structural features implicated in receptor binding and antiviral activity. The identification and expression of duIFN-λ will facilitate further study of the role of type III IFN in antiviral defense and inflammatory responses of the Pekin duck, a non-mammalian vertebrate and pathogen host with relevance for human and animal health.

Genetic variants at the IFNL3 locus and their association with hepatitis C virus infections reveal novel insights into host-virus interactions

Human genetic variation plays a critical role in both spontaneous clearance of and response to interferon (IFN)-based therapies against hepatitis C virus (HCV) as shown by the success of recent genome-wide association studies (GWAS). Several GWAS and later validation studies have shown that single nucleotide polymorphisms (SNPs) at the IFNL3 (formerly IL28B) locus on chromosome 19 are involved in eliminating HCV in human patients. No doubt that this information is helping clinicians worldwide in making better clinical decisions in anti-HCV therapy, but the biological mechanisms involving the SNPs leading to differential responses to therapy and spontaneous clearance of HCV remain elusive. Recent reports including the discovery of a novel IFN (IFN-λ4) gene at the IFNL3 locus and in vitro functional studies implicating 2 SNPs as causal variants lead to novel conclusions and perhaps to new directions in research. An attempt is made in this review to summarize the major findings of the GWAS, the efforts involved in the discovery of causal SNPs; and to explain the biological basis for spontaneous clearance and response to treatment in HCV infections.

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.

Evaluation of interleukin 28B single nucleotide polymorphisms in infants suffering from bronchiolitis

The genetic diversity of the host is believed to be the key of the diversity in the clinical presentation of bronchiolitis. The aim of this study was to determine whether the known rs12979860 and rs8099917 single nucleotide polymorphisms (SNPs) in interleukin (IL)28B region, influence clinical features and natural history of bronchiolitis. Both SNPs showed no significant association with the risk of hospitalization for respiratory syncytial virus (RSV), viral load, disease severity, and other clinical features of patients. Interestingly infants carrying IL28B rs12979860 TT genotype had lower age at hospital admission than that of infants carrying CC/CT genotypes. Overall our results indicate that both IL28B SNPs had no impact on the clinical course of bronchiolitis with the only exception of the IL28B rs12979860 SNP which increased the risk of hospitalization for bronchiolitis at early age.

Crystal structure of Zebrafish interferons I and II reveals conservation of type I interferon structure in vertebrates

Interferons (IFNs) play a major role in orchestrating the innate immune response toward viruses in vertebrates, and their defining characteristic is their ability to induce an antiviral state in responsive cells. Interferons have been reported in a multitude of species, from bony fish to mammals. However, our current knowledge about the molecular function of fish IFNs as well as their evolutionary relationship to tetrapod IFNs is limited. Here we establish the three-dimensional (3D) structure of zebrafish IFNϕ1 and IFNϕ2 by crystallography. These high-resolution structures offer the first structural insight into fish cytokines. Tetrapods possess two types of IFNs that play an immediate antiviral role: type I IFNs (e.g., alpha interferon [IFN-α] and beta interferon [IFN-β]) and type III IFNs (lambda interferon [IFN-λ]), and each type is characterized by its specific receptor usage. Similarly, two groups of antiviral IFNs with distinct receptors exist in fish, including zebrafish. IFNϕ1 and IFNϕ2 represent group I and group II IFNs, respectively. Nevertheless, both structures reported here reveal a characteristic type I IFN architecture with a straight F helix, as opposed to the remaining class II cytokines, including IFN-λ, where helix F contains a characteristic bend. Phylogenetic trees derived from structure-guided multiple alignments confirmed that both groups of fish IFNs are evolutionarily closer to type I than to type III tetrapod IFNs. Thus, these fish IFNs belong to the type I IFN family. Our results also imply that a dual antiviral IFN system has arisen twice during vertebrate evolution.

Signal transducers and activators of transcription-from cytokine signalling to cancer biology

Signal transducers and activators of transcription (STATs) are, as the name indicates, both signal transducers and transcription factors. STATs are activated by cytokines and some growth factors and thus control important biological processes. These include cell growth, cell differentiation, apoptosis and immune responses. Dysregulation of STATs, either due to constitutive activation or function impairment, can have, therefore, deleterious biological consequences. This review places particular emphasis on their structural organization, biological activities and regulatory mechanisms most commonly utilized by cells to control STAT-mediated signalling. STATs also play important roles in cancer and immune deficiencies and are thus being exploited as therapeutic targets.

Interferon-lambda: a new addition to an old family

The discovery and initial description of the interferon-lambda (IFN-lambda) family in early 2003 opened an exciting new chapter in the field of IFN research. There are 3 IFN-lambda genes that encode 3 distinct but highly related proteins denoted IFN-lambda1, -lambda2, and -lambda3. These proteins are also known as interleukin-29 (IL-29), IL-28A, and IL-28B, respectively. Collectively, these 3 cytokines comprise the type III subset of IFNs. They are distinct from both type I and type II IFNs for a number of reasons, including the fact that they signal through a heterodimeric receptor complex that is different from the receptors used by type I or type II IFNs. Although type I IFNs (IFN-alpha/beta) and type III IFNs (IFN-lambda) signal via distinct receptor complexes, they activate the same intracellular signaling pathway and many of the same biological activities, including antiviral activity, in a wide variety of target cells. Consistent with their antiviral activity, expression of the IFN-lambda genes and their corresponding proteins is inducible by infection with many types of viruses. Therefore, expression of the type III IFNs (IFN-lambdas) and their primary biological activity are very similar to the type I IFNs. However, unlike IFN-alpha receptors which are broadly expressed on most cell types, including leukocytes, IFN-lambda receptors are largely restricted to cells of epithelial origin. The potential clinical importance of IFN-lambda as a novel antiviral therapeutic agent is already apparent. In addition, preclinical studies by several groups indicate that IFN-lambda may also be useful as a potential therapeutic agent for other clinical indications, including certain types of cancer.