Nicole Anne De Weerd

Type I interferon receptors : Biochemistry and biological functions

The type I interferon (IFN)2 receptor (IFNAR) is comprised, as other cytokine receptors, of multiple components, in this case designated IFNAR1 and IFNAR2. However it is unique among cytokine receptors in the number of cognate ligands, including 13 IFN subtypes, , , , , and others in some species. The type I IFN receptors are distinct from those required for the type II IFN (IFNGR1 and IFNGR2) and type III IFNs (IFNLR and IL10R ). Nevertheless, genes encoding a component of each type of IFN receptor, namely IFNAR1, IFNAR2, IFNGR2, and IL10R , are located on human chromosome 21q22.1 in a cytokine receptor gene cluster, as typical of functionally related genes. Although IFNswere identified 50 years ago and the existence of IFN receptors 10 years later, it was in 1990when the first type I IFN receptor, now designated IFNAR1, was cloned. This was achieved utilizing human gene libraries expressed in murine cells and rescue of the definitive, species specific antiviral activity of human IFN 8 (1). IFNAR2 cloning was achieved first by identifying a human IFN binding activity in urine, peptide sequencing, and then by gene library screening with derived oligonucleotides (2). It was subsequently discovered that the original cDNA encoded only one isoform of the IFNAR2 gene, which also encoded a long transmembrane isoform that transduced a signal, a truncated transmembrane isoform, and a soluble/secreted isoform (3) (Fig. 1A). Subsequently, the functions of the type I IFN receptors have been elucidated with respect to ligand interaction, mechanisms of signal transduction, and biological responses. The pioneering studies that discovered IFNARs and their mechanisms of actions in vitro have been largely validated in vivo using genetargetedmice. This body of work has highlighted the important roles of IFNARs inmediating type I IFN responses in hemopoiesis and innate and acquired immunity to infection and cancer. However, IFNs elicit many biological effects that can even be opposite in different cell types. For example, type I IFN inhibits proliferation and is proapoptotic for many cell types (4), yet it prolongs the survival of memory T cells (5). Understanding the function of the IFNAR complexwill elucidate how such a diversity of biological outcomes is generated.

Silencing of Irf7 pathways in breast cancer cells promotes bone metastasis through immune escape

Breast cancer metastasis is a key determinant of long-term patient survival. By comparing the transcriptomes of primary and metastatic tumor cells in a mouse model of spontaneous bone metastasis, we found that a substantial number of genes suppressed in bone metastases are targets of the interferon regulatory factor Irf7. Restoration of Irf7 in tumor cells or administration of interferon led to reduced bone metastases and prolonged survival time. In mice deficient in the interferon (IFN) receptor or in natural killer (NK) and CD8+ T cell responses, metastasis was accelerated, indicating that Irf7-driven suppression of metastasis was reliant on IFN signaling to host immune cells. We confirmed the clinical relevance of these findings in over 800 patients in which high expression of Irf7-regulated genes in primary tumors was associated with prolonged bone metastasis–free survival. This gene signature may identify patients that could benefit from IFN-based therapies. Thus, we have identified an innate immune pathway intrinsic to breast cancer cells, the suppression of which restricts immunosurveillance to enable metastasis.

The interferons and their receptors--distribution and regulation.

The interferons (IFNs) were originally described over 50 years ago, identified by their ability to confer viral resistance to cells. We now know that they are much more than just anti‐viral cytokines collectively having roles in both innate and adaptive immune responses, in tumor surveillance and defense, and modulation of immune cell function. Three types of IFN have now been described, simply referred to as type I, II and III. Distinguishable by the unique receptors that they rely on for signal transduction, the three types of IFN have specific and varied roles in the maintenance of human health and defense against pathogens. In mounting an IFN‐mediated immune response, the human body has developed the ability to regulate IFN‐mediated signal transduction. Like all cytokines, the ability of a cell to respond to IFN is completely dependent on the presence of its cognate receptor on the surface of the target cell. Thus, one of the major mechanisms used by the human body to regulate the strength and duration of the IFN response is through regulation of receptor levels, thereby altering the cytokine‐specific responsiveness of the target cell. This review will discuss the receptor system utilized by the type I IFNs and compare it with that of the type II and III IFNs, which also regulate immune responses through controlling receptor level on the cell surface.

Structural basis of a unique interferon-[beta] signaling axis mediated via the receptor IFNAR1

Type I interferons are important in regulating immune responses to pathogens and tumors. All interferons are considered to signal via the heterodimeric IFNAR1-IFNAR2 complex, yet some subtypes such as interferon-β (IFN-β) can exhibit distinct functional properties, although the molecular basis of this is unclear. Here we demonstrate IFN-β can uniquely and specifically ligate to IFNAR1 in an IFNAR2-independent manner, and we provide the structural basis of the IFNAR1–IFN-β interaction. The IFNAR1–IFN-β complex transduced signals that modulated expression of a distinct set of genes independently of Jak-STAT pathways. Lipopolysaccharide-induced sepsis was ameliorated in Ifnar1−/− mice but not Ifnar2−/− mice, suggesting that IFNAR1–IFN-β signaling is pathologically relevant. Thus, we provide a molecular basis for understanding specific functions of IFN-β.

Interferon-ε Protects the Female Reproductive Tract from Viral and Bacterial Infection

A Role for IFN-ɛ Type I interferons (IFNs) are critical cytokines involved in host defense against pathogens, particularly viruses. IFN-ɛ is an IFN-like gene encoded within the type I IFN locus in mice and humans whose function has not been characterized. Fung et al. (p. 1088) created mice with a genetic deletion in Ifn-ɛ and found that, like other type I IFNs, IFN-ɛ signals through the IFN-α receptors 1 and 2. However, unlike these other cytokines, which are primarily expressed by immune cells and are induced upon immune cell triggering, IFN-ɛ was expressed exclusively by epithelial cells of the female reproductive tract in both mice and humans and its expression was hormonally regulated. IFN-ɛ–deficient mice were more susceptible to infection with herpes simplex virus 2 and Chlamydia muridarum, two common sexually transmitted pathogens. The cytokine interferon-ε is expressed in the female reproductive tract and protects against sexually transmitted diseases. The innate immune system senses pathogens through pattern-recognition receptors (PRRs) that signal to induce effector cytokines, such as type I interferons (IFNs). We characterized IFN-ε as a type I IFN because it signaled via the Ifnar1 and Ifnar2 receptors to induce IFN-regulated genes. In contrast to other type I IFNs, IFN-ε was not induced by known PRR pathways; instead, IFN-ε was constitutively expressed by epithelial cells of the female reproductive tract (FRT) and was hormonally regulated. Ifn-ε–deficient mice had increased susceptibility to infection of the FRT by the common sexually transmitted infections (STIs) herpes simplex virus 2 and Chlamydia muridarum. Thus, IFN-ε is a potent antipathogen and immunoregulatory cytokine that may be important in combating STIs that represent a major global health and socioeconomic burden.

Suppressor of cytokine signaling (SOCS) 1 inhibits type I interferon (IFN) signaling via the interferon alpha receptor (IFNAR1)-associated tyrosine kinase Tyk2

Type I IFNs are critical players in host innate and adaptive immunity. IFN signaling is tightly controlled to ensure appropriate immune responses as imbalance could result in uncontrolled inflammation or inadequate responses to infection. It is therefore important to understand how type I IFN signaling is regulated. Here we have investigated the mechanism by which suppressor of cytokine signaling 1 (SOCS1) inhibits type I IFN signaling. We have found that SOCS1 inhibits type I IFN signaling not via a direct interaction with the IFN α receptor 1 (IFNAR1) receptor component but through an interaction with the IFNAR1-associated kinase Tyk2. We have characterized the residues/regions involved in the interaction between SOCS1 and Tyk2 and found that SOCS1 associates via its SH2 domain with conserved phosphotyrosines 1054 and 1055 of Tyk2. The kinase inhibitory region of SOCS1 is also essential for its interaction with Tyk2 and inhibition of IFN signaling. We also found that Tyk2 is preferentially Lys-63 polyubiquitinated and that this activation reaction is inhibited by SOCS1. The consequent effect of SOCS1 inhibition of Tyk2 not only results in a reduced IFN response because of inhibition of Tyk2 kinase-mediated STAT signaling but also negatively impacts IFNAR1 surface expression, which is stabilized by Tyk2.

Mutants of the major ryegrass pollen allergen, Lol p 5, with reduced IgE-binding capacity: candidates for grass pollen-specific immunotherapy.

More than 400 million individuals are sensitized to grass pollen allergens. Group 5 allergens represent the most potent grass pollen allergens recognized by more than 80 % of grass pollen allergic patients. The aim of our study was to reduce the allergenic activity of group 5 allergens for specific immunotherapy of grass pollen allergy. Based on B‐ and T‐cell epitope mapping studies and on sequence comparison of group 5 allergens from different grasses, point mutations were introduced by site‐directed mutagenesis in highly conserved sequence domains of Lol p 5, the group 5 allergen from ryegrass. We obtained Lol p 5 mutants with low IgE‐binding capacity and reduced allergenic activity as determined by basophil histamine release and by skin prick testing in allergic patients. Circular dichroism analysis showed that these mutants exhibited an overall structural fold similar to the recombinant Lol p 5 wild‐type allergen. In addition, Lol p 5 mutants retained the ability to induce proliferation of group 5 allergen‐specific T cell lines and clones. Our results demonstrate that a few point mutations in the Lol p 5 sequence yield mutants with reduced allergenic activitythat represent potential vaccine candidates for immunotherapy of grass pollen allergy.

Suppressor of cytokine signaling (SOCS)1 inhibits type I interferon (IFN) signaling via the IFNAR1 associated tyrosine kinase, Tyk2

Type I IFNs are critical players in host innate and adaptive immunity. IFN signaling is tightly controlled to ensure appropriate immune responses as imbalance could result in uncontrolled inflammation or inadequate responses to infection. It is therefore important to understand how type I IFN signaling is regulated. Here we have investigated the mechanism by which suppressor of cytokine signaling 1 (SOCS1) inhibits type I IFN signaling. We have found that SOCS1 inhibits type I IFN signaling not via a direct interaction with the IFN α receptor 1 (IFNAR1) receptor component but through an interaction with the IFNAR1-associated kinase Tyk2. We have characterized the residues/regions involved in the interaction between SOCS1 and Tyk2 and found that SOCS1 associates via its SH2 domain with conserved phosphotyrosines 1054 and 1055 of Tyk2. The kinase inhibitory region of SOCS1 is also essential for its interaction with Tyk2 and inhibition of IFN signaling. We also found that Tyk2 is preferentially Lys-63 polyubiquitinated and that this activation reaction is inhibited by SOCS1. The consequent effect of SOCS1 inhibition of Tyk2 not only results in a reduced IFN response because of inhibition of Tyk2 kinase-mediated STAT signaling but also negatively impacts IFNAR1 surface expression, which is stabilized by Tyk2.

Genetically Engineered Plant Allergens with Reduced Anaphylactic Activity

Allergy immunotherapy is based on the administration of increasing amounts of the disease–eliciting allergens in order to yield allergen–specific non–responsiveness. Success of this therapy is associated with modulation of the immune response to allergenic molecules at the level of T–helper cells and the induction of blocking antibodies. The extracts used for immunotherapy are highly heterogenous preparations from natural sources and contain additional components, mostly proteins which are not well defined. Recombinant DNA technology offers novel tools for production of pure and well–characterised allergens for specific immunotherapy. However, high IgE reactivity of pure recombinant allergens is associated with an increased risk of potentially life–threatening anaphylactic reactions. A major improvement in allergen–specific immunotherapy may be achieved by using genetically engineered recombinant allergens with reduced anaphylactic activity. Recently the site– directed mutagenesis technique has been applied successfully to produce variants of major grass, birch and oilseed rape allergens with reduced IgE reactivity but retained T–cell reactivity. These modified allergens with reduced anaphylactic potential are novel candidates for safer and more effective allergen–specific immunotherapy.

Molecular Characterization of Polygalacturonases as Grass Pollen-Specific Marker Allergens: Expulsion from Pollen via Submicronic Respirable Particles

Grass pollen belong to the most important allergen sources involved in the elicitation of allergic asthma. We have isolated cDNAs coding for Bermuda grass (Cynodon dactylon) and timothy grass (Phleum pratense) pollen allergens, belonging to a family of pectin-degrading enzymes (i.e., polygalacturonases). The corresponding allergens, termed Cyn d 13 and Phl p 13, represent glycoproteins of ∼42 kDa and isoelectric points of 7.5. rPhl p 13 was expressed in Escherichia coli and purified to homogeneity. Immunogold electron microscopy using rabbit anti-rPhl p 13 Abs demonstrated that in dry pollen group 13, allergens represent primarily intracellular proteins, whereas exposure of pollen to rainwater caused a massive release of cytoplasmic material containing submicronic particles of respirable size, which were coated with group 13 allergens. The latter may explain respiratory sensitization to group 13 allergens and represents a possible pathomechanism in the induction of asthma attacks after heavy rainfalls. rPhl p 13 was recognized by 36% of grass pollen allergic patients, showed IgE binding capacity comparable to natural Phl p 13, and induced specific and dose-dependent basophil histamine release. Epitope mapping studies localized major IgE epitopes to the C terminus of the molecule outside the highly conserved functional polygalacturonase domains. The latter result explains why rPhl p 13 contains grass pollen-specific IgE epitopes and may be used to diagnose genuine sensitization to grass pollen. Our finding that rabbit anti-rPhl p 13 Abs blocked patients’ IgE binding to the allergen suggests that rPhl p 13 may be used for immunotherapy of sensitized patients.