Type I interferons (IFNs) are produced early upon virus infection and signal through the alpha/beta interferon (IFN-α/β) receptor (IFNAR) to induce genes that encode proteins important for limiting viral replication and directing immune responses. To investigate the extent to which type I IFNs play a role in the local regulation of inflammation in the airways, we examined their importance in early lung responses to infection with respiratory syncytial virus (RSV). IFNAR1-deficient (IFNAR1(-/-)) mice displayed increased lung viral load and weight loss during RSV infection. As expected, expression of IFN-inducible genes was markedly reduced in the lungs of IFNAR1(-/-) mice. Surprisingly, we found that the levels of proinflammatory cytokines and chemokines in the lungs of RSV-infected mice were also greatly reduced in the absence of IFNAR signaling. Furthermore, low levels of proinflammatory cytokines were also detected in the lungs of IFNAR1(-/-) mice challenged with noninfectious innate immune stimuli such as selected Toll-like receptor (TLR) agonists. Finally, recombinant IFN-α was sufficient to potentiate the production of inflammatory mediators in the lungs of wild-type mice challenged with innate immune stimuli. Thus, in addition to its well-known role in antiviral resistance, type I IFN receptor signaling acts as a central driver of early proinflammatory responses in the lung. Inhibiting the effects of type I IFNs may therefore be useful in dampening inflammation in lung diseases characterized by enhanced inflammatory cytokine production.

Bluetongue (BT) is a noncontagious, insect-transmitted disease of ruminants caused by the bluetongue virus (BTV). A laboratory animal model would greatly facilitate the studies of pathogenesis, immune response and vaccination against BTV. Herein, we show that adult mice deficient in type I IFN receptor (IFNAR((-/-))) are highly susceptible to BTV-4 and BTV-8 infection when the virus is administered intravenously. Disease was characterized by ocular discharges and apathy, starting at 48 hours post-infection and quickly leading to animal death within 60 hours of inoculation. Infectious virus was recovered from the spleen, lung, thymus, and lymph nodes indicating a systemic infection. In addition, a lymphoid depletion in spleen, and severe pneumonia were observed in the infected mice. Furthermore, IFNAR((-/-)) adult mice immunized with a BTV-4 inactivated vaccine showed the induction of neutralizing antibodies against BTV-4 and complete protection against challenge with a lethal dose of this virus. The data indicate that this mouse model may facilitate the study of BTV pathogenesis, and the development of new effective vaccines for BTV.

The resistance of adult immunocompetent mice to infection with ebolaviruses has led to the development of alternative small animal models that utilise immunodeficient mice, for example the interferon α/β receptor knock-out mouse (IFNR(-/-)). IFNR(-/-) mice have been shown to be susceptible to infection with ebolaviruses by multiple routes but it is not known if this murine model is suitable for testing therapeutics that rely on the generation of an immune response for efficacy. We have tested recombinant adenovirus vectors for their ability to protect IFNR(-/-) mice from challenge with Ebola virus and have analysed the humoral response generated after immunisation. The recombinant vaccines elicited good levels of protection in the knock-out mouse and the antibody response in IFNR(-/-) mice was similar to that observed in vaccinated wild-type mice. These results indicate that the IFNR(-/-) mouse is a relevant small animal model for studying ebolavirus-specific therapeutics.

Interferon alpha/beta (IFN-α/β) is a critical mediator of protection against most viruses, with host survival frequently impossible in its absence. Many studies have investigated the pathways involved in the induction of IFN-α/β after virus infection and the resultant upregulation of antiviral IFN-stimulated genes (ISGs) through IFN-α/β receptor complex signaling. However, other than examining the effects of genetic deletion of induction or effector pathway components, little is known regarding the functionality of these responses in intact hosts and whether host genetic or environmental factors might influence their potency. Here, we demonstrate that the IFN-α/β response against multiple arthropod-vectored viruses, which replicate over a wide temperature range, is extremely sensitive to fluctuations in temperature, exhibiting reduced antiviral efficacy at subnormal cellular temperatures and increased efficacy at supranormal temperatures. The effect involves both IFN-α/β and ISG upregulation pathways with a major aspect of altered potency reflecting highly temperature-dependent transcription of IFN response genes that leads to altered IFN-α/β and ISG protein levels. Discordantly, signaling steps prior to transcription that were examined showed the opposite effect from gene transcription, with potentiation at low temperature and inhibition at high temperature. Finally, we demonstrate that by lowering the temperature of mice, chikungunya arbovirus replication and disease are exacerbated in an IFN-α/β-dependent manner. This finding raises the potential for use of hyperthermia as a therapeutic modality for viral infections and in other contexts such as antitumor therapy. The increased IFN-α/β efficacy at high temperatures may also reflect an innate immune-relevant aspect of the febrile response.IMPORTANCE The interferon alpha/beta (IFN-α/β) response is a first-line innate defense against arthropod-borne viruses (arboviruses). Arboviruses, such as chikungunya virus (CHIKV), can infect cells and replicate across a wide temperature range due to their replication in both mammalian/avian and arthropod hosts. Accordingly, these viruses can cause human disease in tissues regularly exposed to temperatures below the normal mammalian core temperature, 37°C. We questioned whether temperature variation could affect the efficacy of IFN-α/β responses against these viruses and help to explain some aspects of human disease manifestations. We observed that IFN-α/β efficacy was dramatically lower at subnormal temperatures and modestly enhanced at febrile temperatures, with the effects involving altered IFN-α/β response gene transcription but not IFN-α/β pathway signaling. These results provide insight into the functioning of the IFN-α/β response in vivo and suggest that temperature elevation may represent an immune-enhancing therapeutic modality for a wide variety of IFN-α/β-sensitive infections and pathologies.

Zika virus (ZIKV) belongs to mosquito-borne flaviviruses. Unlike other members in the family, ZIKV can be sexually transmitted, and the female genital tracts are susceptible to ZIKV. However, the impact of ZIKV infection on nonpregnant female reproductive health is not understood. In this study, we investigated the effects of ZIKV infection on the ovary by using nonpregnant female interferon α/β receptor-deficient (Ifnar1-/-) mice. The results showed that the ovary supported ZIKV replication, and the granulosa and theca cells of antral follicles were susceptible. ZIKV replication in situ significantly reduced the numbers of antral follicles, aggravated follicular atresia, and disrupted folliculogenesis. Notably, ZIKV replication in the ovary caused disordered ovarian steroidogenesis manifested by decreased expression of key enzymes linked to sex hormone synthesis, including the cytochrome P450 17A1 (CYP17A1) and aromatase (CYP19A1). Further, we observed that ZIKV infection disrupted the estrous cycle and thus prolonged the time to conceive. More importantly, although ZIKV RNA could not be detected at 3 months postinfection, damaged ovarian structure and dysfunction were also observed. Taken together, our study demonstrates that ZIKV infection in nonpregnant female mice cause ovarian damage and dysfunction, even long after ZIKV clearance. These data provide important information to understand the effects of ZIKV infection in female reproductive tissues and basic evidence for further studies. IMPORTANCE Zika virus (ZIKV), a flavivirus, is primarily transmitted by mosquito bites. But it can also be transmitted vertically and sexually. Although ZIKV-associated Guillain-Barré syndrome and microcephaly have drawn great attention, there have been few studies on the potential effects of ZIKV on the genital tract of nonpregnant females. This study investigated the effects of ZIKV on the ovaries in mice. We found that ZIKV replicated in the ovary and the granulosa and theca cells of antral follicles were susceptible. ZIKV replication in situ significantly damaged ovarian structure and function and disrupted folliculogenesis. Notably, ZIKV infection further disrupted the estrous cycle and prolonged the time to conceive in mice by causing disordered ovarian steroidogenesis. These effects were observed in both the acute phase and the recovery phase after viral elimination. Overall, the new findings provide important additions to make out the potential adverse impacts of ZIKV on reproductive health in females.

Ligand-induced endocytosis and lysosomal degradation of cognate receptors regulate the extent of cell signaling. Along with linear endocytic motifs that recruit the adaptin protein complex 2 (AP2)-clathrin molecules, monoubiquitination of receptors has emerged as a major endocytic signal. By investigating ubiquitin-dependent lysosomal degradation of the interferon (IFN)-alpha/beta receptor 1 (IFNAR1) subunit of the type I IFN receptor, we reveal that IFNAR1 is polyubiquitinated via both Lys48- and Lys63-linked chains. The SCF(betaTrcp) (Skp1-Cullin1-F-box complex) E3 ubiquitin ligase that mediates IFNAR1 ubiquitination and degradation in cells can conjugate both types of chains in vitro. Although either polyubiquitin linkage suffices for postinternalization sorting, both types of chains are necessary but not sufficient for robust IFNAR1 turnover and internalization. These processes also depend on the proximity of ubiquitin-acceptor lysines to a linear endocytic motif and on its integrity. Furthermore, ubiquitination of IFNAR1 promotes its interaction with the AP2 adaptin complex that is required for the robust internalization of IFNAR1, implicating cooperation between site-specific ubiquitination and the linear endocytic motif in regulating this process.

Interferon (IFN)-alpha/beta and interleukin (IL)-12 are cytokines critical in defense against viruses, but their cellular sources and mechanisms of regulation for in vivo expression remain poorly characterized. The studies presented here identified a novel subset of dendritic cells (DCs) as major producers of the cytokines during murine cytomegalovirus (MCMV) but not lymphocytic choriomeningitis virus (LCMV) infections. These DCs differed from those activated by Toxoplasma antigen but were related to plasmacytoid cells, as assessed by their CD8alpha(+)Ly6G/C(+)CD11b(-) phenotype. Another DC subset (CD8alpha(2)Ly6G/C(-)CD11b(+)) also contributed to IL-12 production in MCMV-infected immunocompetent mice, modestly. However, it dramatically increased IL-12 expression in the absence of IFN-alpha/beta functions. Conversely, IFN-alpha/beta production was greatly reduced under these conditions. Thus, a cross-regulation of DC subset cytokine responses was defined, whereby secretion of type I IFNs by CD8alpha(+) DCs resulted in responses limiting IL-12 expression by CD11b(+) DCs but enhancing overall IFN-alpha/beta production. Taken together, these data indicate that CD8alpha(+)Ly6G/C(+)CD11b(-) DCs play important roles in limiting viral replication and regulating immune responses, through cytokine production, in some but not all viral infections. They also illustrate the plasticity of cellular sources for innate cytokines in vivo and provide new insights into the roles of IFNs in shaping immune responses to viruses.

Contact sensitivity (CS) responses to reactive hapten Ag, such as picryl chloride (PCl) or oxazolone (OX), are classical examples of T cell-mediated immune responses in vivo that are clearly subject to multifaceted regulation. There is abundant evidence that downregulation of CS may be mediated by T cells exposed to high doses of Ag. This is termed high dose Ag tolerance. To clarify the T cell types that effect CS responses and mediate their downregulation, we have undertaken studies of CS in mice congenitally deficient in specific subsets of lymphocytes. The first such studies, using alpha beta T cell-deficient (TCR alpha -/-) mice, are presented here. The results clearly show that TCR alpha -/- mice cannot mount CS, implicating alpha beta T cells as the critical CS-effector cells. However, TCR alpha -/- mice can, after high dose tolerance, downregulate alpha +/+ CS-effector T cells adoptively transferred into them. By mixing ex vivo and then adoptive cell transfers in vivo, the active downregulatory cells in tolerized alpha -/- mice are shown to include gamma delta TCR+ cells that also can downregulate interferon-gamma production by the targeted CS-effector cells in vitro. Downregulation by gamma delta cells showed specificity for hapten, but was not restricted by the MHC. Together, these findings establish that gamma delta T cells cannot fulfill CS-effector functions performed by alpha beta T cells, but may fulfill an Ag-specific downregulatory role that may be directly comparable to reports of Ag-specific downregulation of IgE antibody responses by gamma delta T cells. Comparisons are likewise considered with downregulation by gamma delta T cells occurring in immune responses to pathogens, tumors, and allografts, and in systemic autoimmunity.

The contribution of distinct central nervous system (CNS) resident cells to protective alpha/beta interferon (IFN-α/β) function following viral infections is poorly understood. Based on numerous immune regulatory functions of astrocytes, we evaluated the contribution of astrocyte IFN-α/β signaling toward protection against the nonlethal glia- and neuronotropic mouse hepatitis virus (MHV) strain A59. Analysis of gene expression associated with IFN-α/β function, e.g., pattern recognition receptors (PRRs) and interferon-stimulated genes (ISGs), revealed lower basal mRNA levels in brain-derived astrocytes than in microglia. Although astrocytes poorly induced Ifnβ mRNA following infection, they upregulated various mRNAs in the IFN-α/β pathway to a higher extent than microglia, supporting effective IFN-α/β responsiveness. Ablation of the IFN-α/β receptor (IFNAR) in astrocytes using mGFAPcre IFNARfl/fl mice resulted in severe encephalomyelitis and mortality, coincident with uncontrolled virus replication. Further, virus spread was not restricted to astrocytes but also affected microglia and neurons, despite increased and sustained Ifnα/β and ISG mRNA levels within the CNS. IFN-γ, a crucial mediator for MHV control, was not impaired in infected mGFAPcre IFNARfl/fl mice despite reduced T cell CNS infiltration. Unexpectedly however, poor induction of IFN-γ-dependent major histocompatibility complex (MHC) class II expression on microglia supported that defective IFN-γ signaling contributes to uncontrolled virus replication. A link between sustained elevated IFN-α/β and impaired responsiveness to IFN-γ supports the novel concept that temporally limited early IFN-α/β responses are critical for effective antiviral IFN-γ function. Overall, our results imply that IFN-α/β signaling in astrocytes is not only critical in limiting early CNS viral spread but also promotes protective antiviral IFN-γ function.IMPORTANCE An antiviral state established by IFN-α/β contains initial viral spread as adaptive immunity develops. While it is apparent that the CNS lacks professional IFN-α/β producers and that resident cells have distinct abilities to elicit innate IFN-α/β responses, protective interactions between inducer and responder cells require further investigation. Infection with a glia- and neuronotropic coronavirus demonstrates that astrocytes mount a delayed but more robust response to infection than microglia, despite their lower basal mRNA levels of IFN-α/β-inducing components. Lethal, uncontrolled viral dissemination following ablation of astrocyte IFN-α/β signaling revealed the importance of IFN-α/β responses in a single cell type for protection. Sustained global IFN-α/β expression associated with uncontrolled virus did not suffice to protect neurons and further impaired responsiveness to protective IFN-γ. The results support astrocytes as critical contributors to innate immunity and the concept that limited IFN-α/β responses are critical for effective subsequent antiviral IFN-γ function.

Japanese encephalitis virus (JEV) is a single-stranded positive-sense RNA virus belonging to the Flaviviridae family. The JEV is the leading cause of viral encephalitis in children and the elderly which is spread by mosquitoes. JEV infection has been established in different animal models such as mouse, hamster, guinea pig, swine, rat, monkey, rabbit by using the different routes of inoculations. Here, we have shown that the alpha/beta and gamma -receptor deficient AG129 mouse induces fatal encephalitis in both young and aged old mice, when challenged with high titer JEV Indian clinical isolate by both intraperitoneal and intradermal route. The JEV infected AG129 mouse have shown neurological symptoms, JEV-induced pathological features and supported high level viral replication. Additionally, administration of JEV in AG129 mice resulted in the induction of severe peripheral vascular permeability, which is a major hall mark of Dengue infection but not shown in JEV. Taken together, our results demonstrate interferon α/β and γ receptors knock out AG129 mouse does not need adaptation of JEV clinical isolates and could be is a promising JEV challenge mouse model by mimicking the natural intradermal route of administration for rapid screening of novel antivirals and vaccines.

In contrast to conventional T cells, natural killer (NK) 1.1+ T cell receptor (TCR)-alpha/beta+ (NK1+T) cells, NK cells, and intestinal intraepithelial lymphocytes (IELs) bearing CD8-alpha/alpha chains constitutively express the interleukin (IL)-2 receptor (R)beta/15Rbeta chain. Recent studies have indicated that IL-2Rbeta/15Rbeta chain is required for the development of these lymphocyte subsets, outlining the importance of IL-15. In this study, we investigated the development of these lymphocyte subsets in interferon regulatory factor 1-deficient (IRF-1-/-) mice. Surprisingly, all of these lymphocyte subsets were severely reduced in IRF-1-/- mice. Within CD8-alpha/alpha+ intestinal IEL subset, TCR-gamma/delta+ cells and TCR-alpha/beta+ cells were equally affected by IRF gene disruption. In contrast to intestinal TCR-gamma/delta+ cells, thymic TCR-gamma/delta+ cells developed normally in IRF-1-/- mice. Northern blot analysis further revealed that the induction of IL-15 messenger RNA was impaired in IRF-1-/- bone marrow cells, and the recovery of these lymphocyte subsets was observed when IRF-1-/- cells were cultured with IL-15 in vitro. These data indicate that IRF-1 regulates IL-15 gene expression, which may control the development of NK1+T cells, NK cells, and CD8-alpha/alpha+ IELs.

In immunocompetent humans, cat scratch disease (CSD) is elicited by the Gram-negative bacterium Bartonella henselae and is characterized by a benign regional lymphadenopathy, the pathogenesis of which is poorly understood. Here, we describe a novel mouse model of Bartonella-induced CSD-like disease that allowed us to investigate the mechanisms leading to lymphadenopathy in vivo. In wild-type mice, a subcutaneous inoculation of either viable or inactivated B. henselae led to a strong swelling of the draining lymph node, which was long-lasting despite the rapid elimination of the bacteria. Carboxyfluorescein- and bromodesoxyuridine-labeling experiments showed that lymph node enlargement resulted from modified immigration and enhanced proliferation of lymphocytes, preferentially of B cells. A comparative analysis of B. henselae and the rodent pathogen B. grahamii in wild-type versus interferon-alpha/beta-receptor I chain-deficient mice revealed that interferon-alpha/beta is not only differentially induced by these two Bartonella species but also exerts an inhibitory effect on the development of lymphadenopathy both in vitro and in vivo. These data demonstrate that the lymphadenopathy of human CSD can be reproduced and studied in a mouse model and provide the first insights into the underlying immunological mechanisms.

Rubella virus (RuV) infection during pregnancy can lead to abortion, stillbirth, and embryonic defects, resulting in congenital rubella syndrome (CRS). It is estimated that there are still 100,000 cases of CRS per year in developing regions with a mortality rate of over 30%. The molecular pathomechanisms remain largely unexplored. Placental endothelial cells (EC) are frequently infected with RuV. RuV reduced the angiogenic and migratory capacity of primary human EC, as confirmed by treatment of EC with serum from RuV IgM-positive patients. Next generation sequencing analysis revealed the induction of antiviral interferon (IFN) type I and III and CXCL10. The RuV-induced transcriptional profile resembled the effects of IFN-β treatment. The RuV-mediated inhibition of angiogenesis was reversed by treatment with blocking and neutralizing antibodies targeting CXCL10 and the IFN-β receptor. The data identify an important role for antiviral IFN-mediated induction of CXCL10 in the control of EC function during RuV infection.

Severe COVID-19 is characterized by lung abnormalities, including the presence of syncytial pneumocytes. Syncytia form when SARS-CoV-2 spike protein expressed on the surface of infected cells interacts with the ACE2 receptor on neighboring cells. The syncytia forming potential of spike variant proteins remain poorly characterized. Here, we first assessed Alpha (B.1.1.7) and Beta (B.1.351) spread and fusion in cell cultures, compared with the ancestral D614G strain. Alpha and Beta replicated similarly to D614G strain in Vero, Caco-2, Calu-3, and primary airway cells. However, Alpha and Beta formed larger and more numerous syncytia. Variant spike proteins displayed higher ACE2 affinity compared with D614G. Alpha, Beta, and D614G fusion was similarly inhibited by interferon-induced transmembrane proteins (IFITMs). Individual mutations present in Alpha and Beta spikes modified fusogenicity, binding to ACE2 or recognition by monoclonal antibodies. We further show that Delta spike also triggers faster fusion relative to D614G. Thus, SARS-CoV-2 emerging variants display enhanced syncytia formation.

We evaluated the safety and immunogenicity of a chimeric alphavirus vaccine candidate in mice with selective immunodeficiencies. This vaccine candidate was highly attenuated in mice with deficiencies in the B and T cell compartments, as well as in mice with deficient gamma-interferon responsiveness. However, the level of protection varied among the strains tested. Wild type mice were protected against lethal VEEV challenge. In contrast, alpha/beta (alphabeta) TCR-deficient mice developed lethal encephalitis following VEEV challenge, while mice deficient in gamma/delta (gammadelta) T cells were protected. Surprisingly, the vaccine potency was diminished by 50% in animals lacking interferon-gamma receptor alpha chain (R1)-chain and a minority of vaccinated immunoglobulin heavy chain-deficient (microMT) mice survived challenge, which suggests that neutralizing antibody may not be absolutely required for protection. Prolonged replication of encephalitic VEEV in the brain of pre-immunized mice is not lethal and adoptive transfer experiments indicate that CD3(+) T cells are required for protection.

Indirect evidence suggests that type-I interferons (IFN-alpha/beta) play a significant role in the pathogenesis of lupus. To directly examine the contribution of these pleiotropic molecules, we created congenic NZB mice lacking the alpha-chain of IFN-alpha/betaR, the common receptor for the multiple IFN-alpha/beta species. Compared with littermate controls, homozygous IFN-alpha/betaR-deleted NZB mice had significantly reduced anti-erythrocyte autoantibodies, erythroblastosis, hemolytic anemia, anti-DNA autoantibodies, kidney disease, and mortality. These reductions were intermediate in the heterozygous-deleted mice. The disease-ameliorating effects were accompanied by reductions in splenomegaly and in several immune cell subsets, including B-1 cells, the major producers of anti-erythrocyte autoantibodies. Decreases of B and T cell proliferation in vitro and in vivo, and of dendritic cell maturation and T cell stimulatory activity in vitro were also detected. Absence of signaling through the IFN-alpha/betaR, however, did not affect increased basal levels of the IFN-responsive p202 phosphoprotein, encoded by a polymorphic variant of the Ifi202 gene associated with the Nba2 predisposing locus in NZB mice. The data indicate that type-I IFNs are important mediators in the pathogenesis of murine lupus, and that reducing their activity in the human counterpart may be beneficial.

An effective type I interferon (IFN-alpha/beta) response is critical for the control of many viral infections. Here we show that in vesicular stomatitis virus (VSV)-infected mouse embryonic fibroblasts (MEFs) the production of IFN-alpha is dependent on type I IFN receptor (IFNAR) triggering, whereas in infected mice early IFN-alpha production is IFNAR independent. In VSV-infected mice type I IFN is produced by few cells located in the marginal zone of the spleen. Unlike other dendritic cell (DC) subsets, FACS((R))-sorted CD11c(int)CD11b(-)GR-1(+) DCs show high IFN-alpha expression, irrespective of whether they were isolated from VSV-infected IFNAR-competent or -deficient mice. Thus, VSV preferentially activates a specialized DC subset presumably located in the marginal zone to produce high-level IFN-alpha largely independent of IFNAR feedback signaling.

A new complementary DNA, p27, has been cloned and sequenced from estradiol-treated MCF7 human breast carcinoma cells. It encodes a putative highly hydrophobic protein of 122 amino acids which has a 33% overall sequence similarity to the product of the 6-16 gene (R. L. Friedman, S. P. Manly, M. McMahon, I. M. Kerr, and G. R. Stark, Cell, 38: 745-755, 1984), which is transcriptionally induced by interferons of the alpha/beta type. We demonstrate here that the p27 gene, which is located in band q32 of human chromosome 14, is also induced by interferon-alpha in human cell lines of different origin and that expression is independent of the presence of estradiol receptor in the cells. High levels of p27 RNA were found in vivo in approximately 50% of primary human breast carcinomas (21 were tested by Northern blotting). In situ hybridization to some of the p27-overexpressing tumors showed that the p27 RNA is localized in cancer cells and sometimes also in fibroblastic cells of tumor stroma. p27 RNA levels in the tumors did not correlate with the presence of estrogen receptor or with the expression of the estrogen-induced pS2 gene. Further studies are now necessary to elucidate the cause of p27 gene overexpression in breast carcinoma and in particular to determine whether it corresponds to chromosomal rearrangements in the 14q32 region and/or to induction by interferons of the alpha/beta type.

Porcine reproductive and respiratory syndrome virus (PRRSV) is the cause of an economically important swine disease that has been devastating the swine industry since the late 1980s. Accumulating evidences have revealed that PRRSV infection fails to induce type I interferon (IFN-alpha/beta), which are normally induced rapidly during virus replication in virus-infected cells. However, the potential mechanisms remain largely unclear. In this study, we showed that PRRSV infection activated the signal transduction components of NF-kappaB and AP-1, but not of interferon regulatory factor 3 (IRF3), an essential IFN-beta transcription factor. Furthermore, PRRSV infection significantly blocked synthetic dsRNA-induced IFN-beta production and IRF3 nuclear translocation. To better understand the upstream signaling events that suppress IRF3 activation, we further investigated the roles of individual components of the retinoic acid-inducible gene I (RIG-I)- and Toll-like receptor 3 (TLR3)-mediated signaling pathway for IFN-beta production during PRRSV infection. We observed that PRRSV infection significantly inhibited dsRNA-induced IRF3 activation and IFN-beta generation by inactivating IFN-beta promoter stimulator 1 (IPS-1), an adaptor molecule of RIG-I. In contrast, PRRSV infection only partially reduced the activation of TIR domain-containing adaptor inducing IFN-beta (TRIF), an adaptor molecule of TLR3. Our results suggest that PRRSV infection suppresses production of IFN-beta primarily by interfering with the IPS-1 activation in the RIG-I signaling pathway.

Down syndrome (DS), the genetic condition caused by trisomy 21, is characterized by variable cognitive impairment, immune dysregulation, dysmorphogenesis and increased prevalence of diverse co-occurring conditions. The mechanisms by which trisomy 21 causes these effects remain largely unknown. We demonstrate that triplication of the interferon receptor (IFNR) gene cluster on chromosome 21 is necessary for multiple phenotypes in a mouse model of DS. Whole-blood transcriptome analysis demonstrated that IFNR overexpression associates with chronic interferon hyperactivity and inflammation in people with DS. To define the contribution of this locus to DS phenotypes, we used genome editing to correct its copy number in a mouse model of DS, which normalized antiviral responses, prevented heart malformations, ameliorated developmental delays, improved cognition and attenuated craniofacial anomalies. Triplication of the Ifnr locus modulates hallmarks of DS in mice, suggesting that trisomy 21 elicits an interferonopathy potentially amenable to therapeutic intervention.