IFN-λ Treatment Research Articles

MiR-124-3p negatively impacts embryo implantation via suppressing uterine receptivity formation and embryo development

During embryo implantation, blastocyst interacts with the receptivity endometrium and the endometrial epithelium secretes nurturing fluid to support embryonic development. Interferon-λ (IFN-λ) is a novel, non-redundant regulator that participates in the fetal–maternal interaction; however, the precise molecular mechanism underlying its impact on uterine receptivity remains elusive. Here, microarray profiling revealed that 149 specific miRNAs were differentially expressed in the human endometrial cells following IFN-λ treatment. In particular, miR-124-3p expression was significantly reduced after IFN-λ treatment (p < 0.05). An in vivo mouse pregnancy model showed that miR-124-3p overexpression notably decreased embryo implantation rate and led to an aberrant epithelial phenotype. Furthermore, miR-124-3p negatively impacted the migration and proliferation of endometrial cells, and hindered embryonic developmental competence in terms of blastocyst formation and global DNA re-methylation. Downstream analysis showed that LIF, MUC1 and BCL2 are potential target genes for miR-124-3p, which was confirmed using western blotting and immunofluorescence assays. In conclusion, IFN-λ-driven downregulation of miR-124-3p during embryo implantation modulates uterine receptivity. The dual functional role of miR-124-3p suggests a cross-talk model wherein, maternal endometrial miRNA acts as a transcriptomic modifier of the peri-implantation endometrium and embryo development.

The transcriptional foundations of interferon-λ-mediated endometrial cell to uterine receptivity.

Interferon-λ (IFN-λ) is a novel non-redundant regulator that participates in the fetal-maternal immune interaction, including immune regulation, uterine receptivity, cell migration and adhesion, and endometrium apoptosis. However, the exact transcriptional foundation for endometrial signaling of IFN-λ is not completely understood, and studies regarding IFN-λ to implantation failure in vivo are limited. The gene expression profile of human endometrial Ishikawa cell line treated with IFN-λ or IFN-α (100ng/mL) for 6h was analyzed using RNA-sequencing. Real-time qPCR, western blotting, and enzyme-linked immunosorbent assay (ELISA) tests were used to validate these sequencing data. An in vivo IFN-λ knock-down mouse pregnancy model was performed, and the phenotype analysis and the intrauterine biomarkers detection were applied with the uterus samples. High levels of messenger RNA (mRNA) were detected for genes previously associated with endometrial receptivity, including LIF, AXL, CRYAB, EPHB2, CCL5, and DDX58, following IFN-λ treatment. Moreover, the data indicated IFN-λ reduced pro-inflammatory gene activity compared with IFN-α, including members of the ISG, TNF, SP100 and interleukin genes. The in vivo mouse pregnancy model showed that inhibition of intrauterine IFN-λ results in aberrant epithelial phenotype and significantly decreases the embryo implantation rates and derails normal uterine receptivity. These findings demonstrate the antagonistic and agonistic roles of IFNs in the endometrial cell, suggesting a selective role of IFN-λ in endometrial receptivity and immunological tolerance regulation. Moreover, the findings provide valuable insight into potential biomarkers related to endometrial receptivity and facilitate an understanding of the molecular changes observed during infertility treatment and contraception usage.

Current Landscape of IFN-λ: Induction, Inhibition, and Potential Clinical Applications to Treat Respiratory Viral Infections.

IFN-λ or type III IFN is an important mediator of antiviral response. Several respiratory viruses induce the production of IFN-λ during their course of infection. However, they have also developed intricate mechanisms to inhibit its expression and activity. Despite a considerable amount of research on the regulatory mechanisms of respiratory viruses on the IFN-λ response, little is still known about the effect of this cytokine on immune cells and the antiviral effects of all IFN-λ isoforms, and a better understanding of the detrimental effects of IFN-λ treatment is required. Here we highlight the relevance of IFN-λ as an antiviral cytokine in the respiratory tract. Data from studies invitro, ex vivo, experimental animal models, and ongoing clinical trials emphasize the therapeutic opportunity that IFN-λ represents to treat and prevent different types of respiratory viral infections.

An endogenously activated antiviral state restricts SARS-CoV-2 infection in differentiated primary airway epithelial cells.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of the coronavirus disease-19 (COVID-19) pandemic, was identified in late 2019 and caused >5 million deaths by February 2022. To date, targeted antiviral interventions against COVID-19 are limited. The spectrum of SARS-CoV-2 infection ranges from asymptomatic to fatal disease. However, the reasons for varying outcomes to SARS-CoV-2 infection are yet to be elucidated. Here we show that an endogenously activated interferon lambda (IFNλ1) pathway leads to resistance against SARS-CoV-2 infection. Using a well-differentiated primary nasal epithelial cell (WD-PNEC) culture model derived from multiple adult donors, we discovered that susceptibility to SARS-CoV-2 infection, but not respiratory syncytial virus (RSV) infection, varied. One of four donors was resistant to SARS-CoV-2 infection. High baseline IFNλ1 expression levels and associated interferon stimulated genes correlated with resistance to SARS-CoV-2 infection. Inhibition of the JAK/STAT pathway in WD-PNECs with high endogenous IFNλ1 secretion resulted in higher SARS-CoV-2 titres. Conversely, prophylactic IFNλ treatment of WD-PNECs susceptible to infection resulted in reduced viral titres. An endogenously activated IFNλ response, possibly due to genetic differences, may be one explanation for the differences in susceptibility to SARS-CoV-2 infection in humans. Importantly, our work supports the continued exploration of IFNλ as a potential pharmaceutical against SARS-CoV-2 infection.

Inhibition of PI3Kδ Differentially Regulates Poly I:C- and Human Metapneumovirus-Induced PD-L1 and PD-L2 Expression in Human Bronchial Epithelial Cells.

Bronchial epithelial cells are front sentinels eliciting innate and adaptive immunity to respiratory viral pathogens. Recognition of viral double-stranded RNA induces antiviral interferon (IFN) responses in bronchial epithelial cells. Co-inhibitory molecules programmed cell death 1 ligand 1 (PD-L1) and ligand 2 (PD-L2) were also induced on bronchial epithelial cells, which bind programmed cell death 1 on T cell and inhibit the function of virus-specific cytotoxic T lymphocyte. A previous study showed that antiviral type I IFN increased PD-L1 and PD-L2 expression in cultured melanoma cells. However, it remains unknown whether antiviral IFNs affect PD-L1 and PD-L2 expression in bronchial epithelial cells. In addition, we previously reported that inhibition of PI3Kδ signaling enhanced antiviral IFN responses in human primary bronchial epithelial cells (PBECs). Here we assessed the effect of exogenous IFNs or a selective PI3Kδ inhibitor IC87114 on PD-L1 and PD-L2 in PBECs stimulated with a synthetic double-stranded RNA poly I:C or human metapneumovirus. Treatment with IFNβ or IFNλ increased PD-L1 and PD-L2, and IFNβ or IFNλ treatment plus poly I:C further increased both expressions. Treatment with IC87114 or transfection with siRNA targeting PI3K p110δ enhanced poly I:C–induced gene and protein expression of PD-L2, whereas IC87114 suppressed poly I:C–induced PD-L1. IC87114 enhanced poly I:C–induced gene expression of IFNβ, IFNλ, and IFN-regulated genes via increased TBK1 and IRF3 phosphorylation. Transfection with siIRF3 counteracted the enhancement of poly I:C–induced PD-L2 by IC87114, whereas IC87114 suppressed poly I:C–induced PD-L1 regardless of transfection with siNC or siIRF3. Similar effects of IC87114 on PD-L1 and PD-L2 expression were observed in human metapneumovirus–infected PBECs. We showed for the first time that type I and type III IFNs induced the expression of PD-L1 and PD-L2 in PBECs. Our findings suggest that during viral infections, inhibition of PI3Kδ differentially regulates PD-L1 and PD-L2 expression in bronchial epithelial cells.

IFN-λ Modulates the Migratory Capacity of Canine Mammary Tumor Cells via Regulation of the Expression of Matrix Metalloproteinases and Their Inhibitors.

Interactions between neoplastic and immune cells taking place in tumors drive cancer regulatory mechanisms both in humans and animals. IFN-λ, a potent antiviral factor, is also secreted in the tumor; however, its role in tumor development is still unclear. In our study, we investigate the influence of IFN-λ on the canine mammary tumor (CMT) cell survival and their metastatic potential in vitro. First, we examined, by Western blot, the expression of the IFN-λ receptor complex in three CMT cell lines (P114, CMT-U27 and CMT-U309). We showed that only two cell lines (P114 and CMT-U27) express both (IL-28RA and IL-10Rb) receptor subunits and respond to IFN-λ treatment by STAT phosphorylation and the expression of interferon-stimulated genes. Using MTT, crystal violet and annexin-V assays, we showed a minimal role of IFN-λ in CMT viability. However, IFN-λ administration had a contradictory effect on cell migration in the scratch test, namely, it increased P114 and decreased CMT-U27 motility. Moreover, we demonstrated that this process is related to the expression of extracellular matrix metalloproteinases and their inhibitors; furthermore, it is independent of Akt and ERK signaling pathways. To conclude, we showed that IFN-λ activity is reliant on the expression of two receptor subunits and tumor type, but further investigations are needed.

Interferon Lambda Inhibits Bacterial Uptake during Influenza Superinfection.

Influenza kills 30,000 to 40,000 people each year in the United States and causes 10 times as many hospitalizations. A common complication of influenza is bacterial superinfection, which exacerbates morbidity and mortality from the viral illness. Recently, methicillin-resistant Staphylococcus aureus (MRSA) has emerged as the dominant pathogen found in bacterial superinfection, with Streptococcus pneumoniae a close second. However, clinicians have few tools to treat bacterial superinfection. Current therapy for influenza/bacterial superinfection consists of treating the underlying influenza infection and adding various antibiotics, which are increasingly rendered ineffective by rising bacterial multidrug resistance. Several groups have recently proposed the use of the antiviral cytokine interferon lambda (IFN-λ) as a therapeutic for influenza, as administration of pegylated IFN-λ improves lung function and survival during influenza by reducing the overabundance of neutrophils in the lung. However, our data suggest that therapeutic IFN-λ impairs bacterial clearance during influenza superinfection. Specifically, mice treated with an adenoviral vector to overexpress IFN-λ during influenza infection exhibited increased bacterial burdens upon superinfection with either MRSA or S. pneumoniae Surprisingly, adhesion molecule expression, antimicrobial peptide production, and reactive oxygen species activity were not altered by IFN-λ treatment. However, neutrophil uptake of MRSA and S. pneumoniae was significantly reduced upon IFN-λ treatment during influenza superinfection in vivo Together, these data support the theory that IFN-λ decreases neutrophil motility and function in the influenza-infected lung, which increases the bacterial burden during superinfection. Thus, we believe that caution should be exercised in the possible future use of IFN-λ as therapy for influenza.

Interferon lambda protects the female reproductive tract against Zika virus infection

Although Zika virus (ZIKV) can be transmitted sexually and cause congenital birth defects, immune control mechanisms in the female reproductive tract (FRT) are not well characterized. Here we show that treatment of primary human vaginal and cervical epithelial cells with interferon (IFN)-α/β or IFN-λ induces host defense transcriptional signatures and inhibits ZIKV infection. We also assess the effects of IFNs on intravaginal infection of the FRT using ovariectomized mice treated with reproductive hormones. We find that mice receiving estradiol are protected against intravaginal ZIKV infection, independently of IFN-α/β or IFN-λ signaling. In contrast, mice lacking IFN-λ signaling sustain greater FRT infection when progesterone is administered. Exogenous IFN-λ treatment confers an antiviral effect when mice receive both estradiol and progesterone, but not progesterone alone. Our results identify a hormonal stage-dependent role for IFN-λ in controlling ZIKV infection in the FRT and suggest a path for minimizing sexual transmission of ZIKV in women.

Type III interferons are critical host factors that determine susceptibility to Influenza A viral infection in allergic nasal mucosa.

Allergic respiratory conditions have been associated with increased susceptibility to viral infection due to impaired interferon (IFN)-related immune responses, but the mechanisms for reinforcement of mucosal immunity against viral infection in allergic diseases are largely unknown. To determine whether IFN induction would be impaired in allergic nasal mucosa and to identify whether higher loads of influenza A virus (IAV) in allergic nasal mucosa could be controlled with IFN treatment. Influenza A virus mRNA, viral titres and IFN expression were compared in IAV-infected normal human nasal epithelial (NHNE, N=10) and allergic rhinitis nasal epithelial (ARNE, N=10) cells. We used invivo model of allergic rhinitis (BALB/c mice, N=10) and human nasal mucosa from healthy volunteers (N=72) and allergic rhinitis patients (N=29) to assess the induction of IFNs after IAV infection. Influenza A virus mRNA levels and viral titres were significantly higher in ARNE compared with NHNE cells. IFN-β and IFN-λs were induced in NHNE and ARNE cells up to 3days after IAV infection. Interestingly, induction of IFN-λs mRNA levels and the amount of secreted proteins were considerably lower in ARNE cells. The mean IFN-λs mRNA level was also significantly lower in the nasal mucosa of AR patients, and we found that recombinant IFN-λ treatment attenuated viral mRNA levels and viral titres in IAV-infected ARNE cells. In vivoAR mouse exhibited higher viral load after IAV infection, but intranasal inoculation of IFN-λ completely decreased IAV protein expression and viral titre in nasal mucosa of IAV-infected AR mouse. Higher susceptibility of the allergic nasal mucosa to IAV may depend on impairment of type III IFN induction, and type III IFN is a key mechanistic link between higher viral loads and control of IAV infection in allergic nasal mucosa.

Gestational Stage and IFN-λ Signaling Regulate ZIKV Infection In Utero

Although Zika virus (ZIKV)-induced congenital disease occurs more frequently during early stages of pregnancy, its basis remains undefined. Using established type I interferon (IFN)-deficient mouse models of ZIKV transmission in utero, we found that the placenta and fetus were more susceptible to ZIKV infection at earlier gestational stages. Whereas ZIKV infection at embryonic day 6 (E6) resulted in placental insufficiency and fetal demise, infections at midstage (E9) resulted in reduced cranial dimensions, and infection later in pregnancy (E12) caused no apparent fetal disease. In addition, we found that fetuses lacking type III IFN-λ signaling had increased ZIKV replication inthe placenta and fetus when infected at E12, and reciprocally, treatment of pregnant mice with IFN-λ2 reduced ZIKV infection. IFN-λ treatment analogously diminished ZIKV infection in human midgestation fetal- and maternal-derived tissue explants. Our data establish a model of gestational stage dependence of ZIKV pathogenesis and IFN-λ-mediated immunity at the maternal-fetal interface.

Outcomes of congenital Zika disease depend on timing of infection and maternal-fetal immunophysiological conditions

Abstract Here, we examined outcomes of congenital Zika disease in mice at different times of infection. Female mice lacking interferon alpha receptor (IFNAR−/−) were crossed to their male counterparts (KO×KO), and were subsequently infected with ZIKV at embryonic day (E) 5.5, E10.5 and E15.5, respectively. Dams infected with ZIKV at E5.5 had nearly 100% fetal demise. Dams exposed to ZIKV at E10.5 exhibited fetal demise and IUGR, whereas infection at E15.5 did not result in these clinical outcomes. To gauge the effect of IFN signaling at the maternal-fetal interface on the pregnant outcomes, we established a mouse model in which IFNAR−/−female mice were susceptible to ZIKV infection and their offspring were capable of type I IFN signaling due to a heterozygous breeding scheme (KO×WT). No viral burden was detected in multiple organs; also, no fetal demise was observed in the KO×WT group when they were infected at mid- and late pregnancy. The immune resistance in the heterozygous group was accompanied by high expression of IFN-stimulated genes (ISGs). Type III IFN also induced ISGs similar to type I IFNs through a distinct receptor. To gauge the effect of type III IFN on the host resistance to ZIKV and pregnant outcomes, we i.p. treated the pregnant mice with IFN-λ prior to and after ZIKV infection at E5.5, E10.5, and E15.5. We found that IFN-λ treatment reduced viral burden in maternal and fetal organs, upregulated ISG expression, and relieved fetal growth restriction at mid pregnancy. Thus, our data demonstrated that IFN signaling at the maternal-fetal interface is critical for the outcomes of pregnancy, especially at the mid pregnancy stage, during maternal ZIKV infection. IFN-λ inhibits ZIKV infection and confers protection to infected fetuses.

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.

IFNλ is a potent anti-influenza therapeutic without the inflammatory side effects of IFNα treatment.

Influenza A virus (IAV)‐induced severe disease is characterized by infected lung epithelia, robust inflammatory responses and acute lung injury. Since type I interferon (IFNαβ) and type III interferon (IFNλ) are potent antiviral cytokines with immunomodulatory potential, we assessed their efficacy as IAV treatments. IFNλ treatment of IAV‐infected Mx1‐positive mice lowered viral load and protected from disease. IFNα treatment also restricted IAV replication but exacerbated disease. IFNα treatment increased pulmonary proinflammatory cytokine secretion, innate cell recruitment and epithelial cell death, unlike IFNλ‐treatment. IFNλ lacked the direct stimulatory activity of IFNα on immune cells. In epithelia, both IFNs induced antiviral genes but no inflammatory cytokines. Similarly, human airway epithelia responded to both IFNα and IFNλ by induction of antiviral genes but not of cytokines, while hPBMCs responded only to IFNα. The restriction of both IFNλ responsiveness and productive IAV replication to pulmonary epithelia allows IFNλ to limit IAV spread through antiviral gene induction in relevant cells without overstimulating the immune system and driving immunopathology. We propose IFNλ as a non‐inflammatory and hence superior treatment option for human IAV infection.

Induction and protective effect of innate interferons during human astrovirus infection (VIR1P.1003)

Abstract Members of the relatively new Astroviridae family are non-enveloped, single-stranded RNA viruses that cause diarrheal disease in a wide range species. Human astroviruses, of which there are eight canonical strains, are a leading cause of gastroenteritis in children &amp;lt;2 years old, the elderly, and immunocompromised patients. Because of the lack of a small animal model of astroviral gastroenteritis, little is known about the host response to infection. The role of type I and type III interferons (IFN), IFN-α/β and IFN-λ respectively, in mediating innate antiviral immune responses through a STAT1-dependent mechanism have been well established. Using human astrovirus type 1 (HAstV-1), the most common serotype isolated from human cases of gastroenteritis, we investigated the innate IFN response to astrovirus in cultured colonic epithelial cells (Caco2). HAstV-1 induced modest levels of IFN-β in Caco2 cells by 24 hours post-infection. Pre-treatment of cells with IFN-β protected Caco2 cells from HAstV-1 infection in a dose-dependent manner. Further, viral titers were significantly elevated in the presence of a neutralizing antibody to IFN-β. These data are in contrast to IFN-λ, which is induced by HAstV-1 to levels approximately 10-fold greater than those of IFN-β. However, IFN-λ pretreatment was not protective. Consistent with this, IFN-λ treatment did not induce STAT1 phosphorylation, suggesting that Caco2 cells are not responsive to IFN-λ.

HCV Infection Selectively Impairs Type I but Not Type III IFN Signaling

A stable and persistent Hepatitis C virus (HCV) replication cell culture model was developed to examine clearance of viral replication during long-term treatment using interferon-α (IFN-α), IFN-λ, and ribavirin (RBV). Persistently HCV-infected cell culture exhibited an impaired antiviral response to IFN-α+RBV combination treatment, whereas IFN-λ treatment produced a strong and sustained antiviral response that cleared HCV replication. HCV replication in persistently infected cells induced chronic endoplasmic reticulum (ER) stress and an autophagy response that selectively down-regulated the functional IFN-α receptor-1 chain of type I, but not type II (IFN-γ) or type III (IFN-λ) IFN receptors. Down-regulation of IFN-α receptor-1 resulted in defective JAK-STAT signaling, impaired STAT phosphorylation, and impaired nuclear translocation of STAT. Furthermore, HCV replication impaired RBV uptake, because of reduced expression of the nucleoside transporters ENT1 and CNT1. Silencing ER stress and the autophagy response using chemical inhibitors or siRNA additively inhibited HCV replication and induced viral clearance by the IFN-α+RBV combination treatment. These results indicate that HCV induces ER stress and that the autophagy response selectively impairs type I (but not type III) IFN signaling, which explains why IFN-λ (but not IFN-α) produced a sustained antiviral response against HCV. The results also indicate that inhibition of ER stress and of the autophagy response overcomes IFN-α+RBV resistance mechanisms associated with HCV infection.

Type III IFNs are produced by and stimulate human plasmacytoid dendritic cells.

Plasmacytoid dendritic cells (pDC) are rare cells found in peripheral blood and lymphoid tissues. pDC are considered to be "professional" type I IFN-producing cells and produce 10- to 100-fold more IFN-α than other cell types in response to enveloped viruses or synthetic TLR7 and TLR9 agonists. In this study, purified pDC were found to express high levels of IFN-λ receptor mRNA, as well as cell-surface IFN-λ receptor. We have developed intracellular flow cytometry assays using Abs to IFN-λ1/3 or -λ2 to assess the expression of IFN-λ proteins by pDC. We observed that a subset of human pDC expresses only intracellular IFN-α, whereas another subset produces both IFN-α and IFN-λ after stimulation with virus or the TLR9 agonist, CpG A; the cells that coexpressed IFN-α and IFN-λ were the cells with the highest levels of IFN-α expression. Ab cross-linking of CD4 or CD303 molecules on pDC inhibited both HSV-induced IFN-λ and IFN-α production. Like the production of IFN-α, the HSV-induced IFN-λ production in pDC was mediated through TLR9 and independent of virus replication. Exogenous IFN-λ treatment of pDC resulted in increased virus-induced expression of both IFN-α and IFN-λ. In addition, both exogenous IFN-λ and -α inhibited dexamethasone-induced apoptosis of pDC. We conclude that pDC are major producers of IFN-λ1 and -λ2 in response to viral stimulation and also express functional receptors for this cytokine. Thus, IFN-λ can serve as an autocrine signal to strengthen the antiviral response of pDC by increasing IFN-α and IFN-λ production, resulting in prolonged pDC survival.

Type I interferon inhibits acute IL-5 and IL-13 expression in human memory CD4+ T cells (125.12)

Abstract Type I Interferon (IFN-α/β) is an innate cytokine important for fighting infections and is used to treat hepatitis C infection and multiple sclerosis, among other diseases. Although the innate role of this cytokine has been studied extensively, our group has shown that IFN-α/β plays a role in shaping the adaptive immune response in humans. Recently, we demonstrated that IFN-α/β inhibits Th2 development by regulating mRNA and protein levels of GATA3. Regulation of GATA3 in turn suppresses Th2 cytokine production, without effecting IFN-γ production. In addition to blocking Th2 development, we now demonstrate an acute inhibition of human memory T cell function upon treatment with IFN-α/β. Human memory CD4+ T cells acutely activated with anti-CD3 in the presence of IFN-α/β resulted in reduced mRNA levels of Th2 cytokine genes, IL5 and IL13, but did not effect IL4 expression. GATA3 levels were not affected, suggesting a GATA3-independent mechanism. Further experiments have determined that this regulatory mechanism does not require new protein synthesis. This mechanism seems to be specific to IFN-α/β, as neither IFN-γ nor IFN-λ treatment were able to repress Th2 cytokine mRNA expression to the extent of IFN-α/β. This study has uncovered an additional level of regulation that blocks early TCR signaling events that affect Th2 function. This novel pathway suggests that treatment of atopic asthmatic individuals with IFN-α/β can regulate both Th2 development and memory Th2 function.

Induction of interferon‐λ contributes to toll‐like receptor 3‐mediated herpes simplex virus type 1 inhibition in astrocytes

Toll-like receptor 3 (TLR3) recognizes double-stranded RNA and induces type I interferon (IFN)-mediated antiviral immunity against a number of viral infections. Type III IFN (IFN-λ) is a newly identified antiviral cytokine that has biological functions similar to those of type I IFNs. We thus investigated the role of IFN-λ in TLR3 activation-mediated inhibition of herpes simplex virus type 1 (HSV-1) in human primary astrocytes. Human astrocytes express endogenous IFN-λ1 and IFN-λ receptor complex, interleukin-28 receptor α subunit (IL-28Rα), and IL-10Rβ. The activation of TLR3 by poly-I:C treatment significantly induced the expression of IFN-λ1 and IFN-λ2/3 in astrocytes. The induction of IFN-λ contributed to TLR3 activation-mediated HSV-1 inhibition in astrocytes. Investigation of the mechanisms showed that treatment of astrocytes with specific antibody against IFN-λ receptor attenuated the anti-HSV-1 activity of poly-I:C, indicating that endogenous IFN-λ contributes to the anti-HSV-1 effect of TLR3 activation. The anti-HSV-1 effect of endogenous IFN-λ was also confirmed by the finding that recombinant IFN-λ treatment inhibited HSV-1 infection of astrocytes. These results provide direct and compelling evidence that endogenous IFN-λ participates in TLR3-mediated antiviral activity, which may have important implications in host cell innate immunity against HSV-1 infection in the CNS.

Type III IFN Receptor Expression and Functional Characterisation in the Pteropid Bat, Pteropus alecto

Bats are rich reservoir hosts for a variety of viruses, many of which are capable of spillover to other susceptible mammals with lethal consequences. The ability of bats to remain asymptomatic to viral infection may be due to the rapid control of viral replication very early in the immune response through innate antiviral mechanisms. Type I and III interferons (IFNs) represent the first line of defence against viral infection in mammals, with both families of IFNs present in pteropid bats. To obtain further insight into the type III IFN system in bats, we describe the characterization of the type III IFN receptor (IFNλR) in the black flying fox, P. alecto with the characterization of IFNλR1 and IL10R2 genes that make up the type III IFN receptor complex. The bat IFNλR complex has a wide tissue distribution and at the cellular level, both epithelial and immune cells are responsive to IFN-λ treatment. Furthermore, we demonstrate that the bat IFNλR1 chain acts as a functional receptor. To our knowledge, this report represents the first description of an IFN receptor in any species of bat. The responsiveness of bat cells to IFN-λ support a role for the type III IFN system by epithelial and immune cells in bats.

Interferon-β and interferon-λ signaling is not affected by interferon-induced refractoriness to interferon-α in vivo

Therapy of chronic hepatitis C with pegylated interferon α (pegIFN-α) and ribavirin achieves sustained virological responses in approximately half of the patients. Nonresponse to treatment is associated with constitutively increased expression of IFN-stimulated genes in the liver already before therapy. This activation of the endogenous IFN system could prevent cells from responding to therapeutically injected (peg)IFN-α, because prolonged stimulation of cells with IFN-α induces desensitization of the IFN signal transduction pathway. Whether all types of IFNs induce refractoriness in the liver is presently unknown. We therefore treated mice with multiple injections and different combinations of IFN-α, IFN-β, IFN-γ, and IFN-λ. Pretreatment of mice with IFN-α, IFN-β, and IFN-λ induced a strong expression of the negative regulator ubiquitin-specific peptidase 18 in the liver and gut. As a result, IFN-α signaling was significantly reduced when mice where reinjected 16 hours after the first injection. Surprisingly, both IFN-β and IFN-λ could activate the Janus kinase-signal transducer and activator of transcription (STAT) pathway and the expression of IFN-stimulated genes despite high levels of ubiquitin-specific peptidase 18. IFN-λ treatment of human liver biopsies ex vivo resulted in strong and maintained phosphorylation of STAT1, whereas IFN-α-induced STAT1 activation was transient. Contrary to the action of IFN-α, IFN-β, and IFN-λ signaling in the liver does not become refractory during repeated stimulation of the IFN signal transduction pathway. The sustained efficacy of IFN-β and IFN-λ could be an important advantage for the treatment patients who are nonresponders to pegIFN-α, through a preactivated endogenous IFN system.