Regulation of type I interferon responses

In Vivo Conditions Enable IFNAR-Independent Type I Interferon Production by Peritoneal CD11b+ Cells upon Thogoto Virus Infection

Type I interferons (IFNs) crucially contribute to host survival upon viral infections. Robust expression of type I IFNs (IFN-α/β) and induction of an antiviral state critically depend on amplification of the IFN signal via the type I IFN receptor (IFNAR). A small amount of type I IFN produced early upon virus infection binds the IFNAR and activates a self-enhancing positive feedback loop, resulting in induction of large, protective amounts of IFN-α. Unexpectedly, we found robust, systemic IFN-α expression upon infection of IFNAR knockout mice with the orthomyxovirus Thogoto virus (THOV). The IFNAR-independent IFN-α production required in vivo conditions and was not achieved during in vitro infection. Using replication-incompetent THOV-derived virus-like particles, we demonstrate that IFNAR-independent type I IFN induction depends on viral polymerase activity but is largely independent of viral replication. To discover the cell type responsible for this effect, we used type I IFN reporter mice and identified CD11b(+) F4/80(+) myeloid cells within the peritoneal cavity of infected animals as the main source of IFNAR-independent type I IFN, corresponding to the particular tropism of THOV for this cell type.

IMPORTANCE

Type I IFNs are crucial for the survival of a host upon most viral infections, and, moreover, they shape subsequent adaptive immune responses. Production of protective amounts of type I IFN critically depends on the positive feedback amplification via the IFNAR. Unexpectedly, we observed robust IFNAR-independent type I IFN expression upon THOV infection and unraveled molecular mechanisms and determined the tissue and cell type involved. Our data indicate that the host can effectively use alternative pathways to induce type I IFN responses if the classical feedback amplification is not available. Understanding how type I IFN can be produced in large amounts independently of IFNAR-dependent enhancement will identify mechanisms which might contribute to novel therapeutic strategies to fight viral pathogens.

Immune-Mediated Nephropathy and Systemic Autoimmunity in Mice Does Not Require Receptor Interacting Protein Kinase 3 (RIPK3)

Immune mediated nephropathy is one of the most serious manifestations of lupus and is characterized by severe inflammation and necrosis that, if untreated, eventually leads to renal failure. Although lupus has a higher incidence in women, both sexes can develop lupus glomerulonephritis; nephritis in men develops earlier and is more severe than in women. It is therefore important to understand the cellular and molecular mechanisms mediating nephritis in each sex. Previous work by our lab found that the absence or pharmacological inhibition of Poly [ADP-ribose] polymerase 1 (PARP-1), an enzyme involved in DNA repair and necrotic cell death, affects only male mice and results in milder nephritis, with less in situ inflammation, and diminished incidence of necrotic lesions, allowing for higher survival rates. A second pathway mediating necrosis involves Receptor-Interacting Serine-Threonine Kinase 3 (RIPK3); in this study we sought to investigate the impact of RIPK3 on the development of lupus and nephritis in both sexes. To this end, we used two inducible murine models of lupus: chronic graft versus host disease (cGvHD) and pristane-induced lupus; and nephrotoxic serum (NTS)-induced nephritis as a model of immune mediated nephropathy. We found that the absence of RIPK3 has neither positive nor negative impact on the disease development or progression of lupus and nephritis in all three models, and in both male and female mice. We conclude that RIPK3 is dispensable for the pathogenesis of lupus and immune mediated nephropathy as to accelerate, worsen or ameliorate the disease.

Safe and Effective Treatment of Experimental Neuroblastoma and Glioblastoma Using Systemically Delivered Triple MicroRNA-Detargeted Oncolytic Semliki Forest Virus

Background: Glioblastoma multiforme and high-risk neuroblastoma are cancers with poor outcome. Immunotherapy in the form of neurotropic oncolytic viruses is a promising therapeutic approach for these malignancies. Here we evaluate the oncolytic capacity of the neurovirulent and partly IFNβ-resistant Semliki Forest virus (SFV)-4 in glioblastoma multiformes and neuroblastomas. To reduce neurovirulence we constructed SFV4miRT, which is attenuated in normal central nervous system (CNS) cells through insertion of microRNA target sequences for miR124, miR125, miR134.Methods: Oncolytic activity of SFV4miRT was examined in mouse neuroblastoma and glioblastoma multiforme cell lines and in patient-derived human glioblastoma cell cultures (HGCC). In vivo neurovirulence and therapeutic efficacy was evaluated in two syngeneic orthotopic glioma models (CT-2A, GL261) and a syngeneic subcutaneous neuroblastoma model (NXS2). The role of IFNβ in inhibiting therapeutic efficacy was investigated.Results: The introduction of miRNA target sequences reduced neurovirulence of SFV4 in terms of attenuated replication in mouse CNS cells and ability to cause encephalitis when administered intravenously. A single intravenous injection of SFV4miRT prolonged survival and cured four of eight mice (50%) with NXS2 and three of 11 mice (27%) with CT-2A, but not for GL261 tumor-bearing mice. In vivo therapeutic efficacy in different tumor models inversely correlated to secretion of IFNβ by respective cells upon SFV4 infection in vitro Similarly, killing efficacy of HGCC lines inversely correlated to IFNβ response and interferon-α/β receptor-1 expression.Conclusions: SFV4miRT has reduced neurovirulence, while retaining its oncolytic capacity. SFV4miRT is an excellent candidate for treatment of glioblastoma multiforme and neuroblastoma with low IFN-β secretion. Clin Cancer Res; 23(6); 1519-30. ©2016 AACR.

The Brain Proteome of the Ubiquitin Ligase Peli1 Knock-Out Mouse during Experimental Autoimmune Encephalomyelitis

The ubiquitin ligase Peli1 has previously been suggested as a potential treatment target in multiple sclerosis. In the multiple sclerosis disease model, experimental autoimmune encephalomyelitis, Peli1 knock-out led to less activated microglia and less inflammation in the central nervous system. Despite being important in microglia, Peli1 expression has also been detected in glial and neuronal cells. In the present study the overall brain proteomes of Peli1 knock-out mice and wild-type mice were compared prior to experimental autoimmune encephalomyelitis induction, at onset of the disease and at disease peak. Brain samples from the frontal hemisphere, peripheral from the extensive inflammatory foci, were analyzed using TMT-labeling of sample pools, and the discovered proteins were verified in individual mice using label-free proteomics. The greatest proteomic differences between Peli1 knock-out and wild-type mice were observed at the disease peak. In Peli1 knock-out a higher degree of antigen presentation, increased activity of adaptive and innate immune cells and alterations to proteins involved in iron metabolism were observed during experimental autoimmune encephalomyelitis. These results unravel global effects to the brain proteome when abrogating Peli1 expression, underlining the importance of Peli1 as a regulator of the immune response also peripheral to inflammatory foci during experimental autoimmune encephalomyelitis.

The proteomics data is available in PRIDE with accession PXD003710.

Extremes of Interferon-Stimulated Gene Expression Associate with Worse Outcomes in the Acute Respiratory Distress Syndrome

Acute Respiratory Distress Syndrome (ARDS) severity may be influenced by heterogeneity of neutrophil activation. Interferon-stimulated genes (ISG) are a broad gene family induced by Type I interferons, often as a response to viral infections, which evokes extensive immunomodulation. We tested the hypothesis that over- or under-expression of immunomodulatory ISG by neutrophils is associated with worse clinical outcomes in patients with ARDS. Genome-wide transcriptional profiles of circulating neutrophils isolated from patients with sepsis-induced ARDS (n = 31) and healthy controls (n = 19) were used to characterize ISG expression. Hierarchical clustering of expression identified 3 distinct subject groups with Low, Mid and High ISG expression. ISG accounting for the greatest variability in expression were identified (MX1, IFIT1, and ISG15) and used to analyze a prospective cohort at the Colorado ARDS Network site. One hundred twenty ARDS patients from four urban hospitals were enrolled within 72 hours of initiation of mechanical ventilation. Circulating neutrophils were isolated from patients and expression of ISG determined by PCR. Samples were stratified by standard deviation from the mean into High (n = 21), Mid, (n = 82) or Low (n = 17) ISG expression. Clinical outcomes were compared between patients with High or Low ISG expression to those with Mid-range expression. At enrollment, there were no differences in age, gender, co-existing medical conditions, or type of physiologic injury between cohorts. After adjusting for age, race, gender and BMI, patients with either High or Low ISG expression had significantly worse clinical outcomes than those in the Mid for number of 28-day ventilator- and ICU-free days (P = 0.0006 and 0.0004), as well as 90-day mortality and 90-day home with unassisted breathing (P = 0.02 and 0.004). These findings suggest extremes of ISG expression by circulating neutrophils from ARDS patients recovered early in the syndrome are associated with poorer clinical outcomes.

Identification of Two Subgroups of Type I IFNs in Perciforme Fish Large Yellow Croaker Larimichthys crocea Provides Novel Insights into Function and Regulation of Fish Type I IFNs

Like mammals, fish possess an interferon regulatory factor (IRF) 3/IRF7-dependent type I IFN responses, but the exact mechanism by which IRF3/IRF7 regulate the type I IFNs remains largely unknown. In this study, we identified two type I IFNs in the Perciforme fish large yellow croaker Larimichthys crocea, one of which belongs to the fish IFNd subgroup and the other is assigned to a novel subgroup of group I IFNs in fish, tentatively termed IFNh. The two IFN genes are constitutively expressed in all examined tissues, but with varied expression levels. Both IFN genes can be rapidly induced in head kidney and spleen tissues by polyinosinic-polycytidylic acid. The recombinant IFNh was shown to be more potent to trigger a rapid induction of the antiviral genes MxA and protein kinase R than the IFNd, suggesting that they may play distinct roles in regulating early antiviral immunity. Strikingly, IFNd, but not IFNh, could induce the gene expression of itself and IFNh through a positive feedback loop mediated by the IFNd-dependent activation of IRF3 and IRF7. Furthermore, our data demonstrate that the induction of IFNd can be enhanced by the dimeric formation of IRF3 and IRF7, while the IFNh expression mainly involves IRF3. Taken together, our findings demonstrate that the IFN responses are diverse in fish and are likely to be regulated by distinct mechanisms.

Type I IFN Signaling Is Dispensable during Secondary Viral Infection

Innate immune responses in general, and type I interferons (T1IFNs) in particular, play an important and often essential role during primary viral infections, by directly combatting the virus and by maximizing the primary adaptive immune response. Several studies have suggested that T1IFNs also contribute very substantially to the secondary (recall) response; they are thought (i) to be required to drive the early attrition of memory T cells, (ii) to support the subsequent expansion of surviving virus-specific memory cells, and (iii) to assist in the suppression and clearance of the infectious agent. However, many of these observations were predicated upon models in which T1IFN signaling was interrupted prior to a primary immune response, raising the possibility that the resulting memory cells might be intrinsically abnormal. We have directly addressed this by using an inducible-Cre model system in which the host remains genetically-intact during the primary response to infection, and in which T1IFN signaling can be effectively ablated prior to secondary viral challenge. We report that, in stark contrast to primary infection, T1IFN signaling is not required during the recall response. IFNαβR-deficient memory CD8+ and CD4+ memory T cells undergo attrition and expansion with kinetics that are indistinguishable from those of receptor-sufficient cells. Moreover, even in the absence of functional T1IFN signaling, the host's immune capacity to rapidly suppress, and then to eradicate, a secondary infection remains intact. Thus, this study shows that T1IFN signaling is dispensable during the recall response to a virus infection. Moreover, two broader implications may be drawn. First, a T cell's requirement for a cytokine is highly dependent on the cell's maturation / differentiation status. Consequently, second, these data underscore the importance of evaluating a gene's impact by modulating its expression or function in a temporally-controllable manner.

The Golgi apparatus acts as a platform for TBK1 activation after viral RNA sensing

BACKGROUND

After viral infection and the stimulation of some pattern-recognition receptors, TANK-binding kinase I (TBK1) is activated by K63-linked polyubiquitination followed by trans-autophosphorylation. While the activated TBK1 induces type I interferon production by phosphorylating the transcription factor IRF3, the precise molecular mechanisms underlying TBK1 activation remain unclear.

RESULTS

We report here the localization of the ubiquitinated and phosphorylated active form of TBK1 to the Golgi apparatus after the stimulation of RIG-I-like receptors (RLRs) or Toll-like receptor-3 (TLR3), due to TBK1 K63-linked ubiquitination on lysine residues 30 and 401. The ubiquitin-binding protein optineurin (OPTN) recruits ubiquitinated TBK1 to the Golgi apparatus, leading to the formation of complexes in which TBK1 is activated by trans-autophosphorylation. Indeed, OPTN deficiency in various cell lines and primary cells impairs TBK1 targeting to the Golgi apparatus and its activation following RLR or TLR3 stimulation. Interestingly, the Bluetongue virus NS3 protein binds OPTN at the Golgi apparatus, neutralizing its activity and thereby decreasing TBK1 activation and downstream signaling.

CONCLUSIONS

Our results highlight an unexpected role of the Golgi apparatus in innate immunity as a key subcellular gateway for TBK1 activation after RNA virus infection.

DNA nanomaterials for preclinical imaging and drug delivery

Besides being the carrier of genetic information, DNA is also an excellent biological organizer to establish well-designed nanostructures in the fields of material engineering, nanotechnology, and biomedicine. DNA-based materials represent a diverse nanoscale system primarily due to their predictable base pairing and highly regulated conformations, which greatly facilitate the construction of DNA nanostructures with distinct shapes and sizes. Integrating the emerging advancements in bioconjugation techniques, DNA nanostructures can be readily functionalized with high precision for many purposes ranging from biosensors to imaging to drug delivery. Recent progress in the field of DNA nanotechnology has exhibited collective efforts to employ DNA nanostructures as smart imaging agents or delivery platforms within living organisms. Despite significant improvements in the development of DNA nanostructures, there is limited knowledge regarding the in vivo biological fate of these intriguing nanomaterials. In this review, we summarize the current strategies for designing and purifying highly-versatile DNA nanostructures for biological applications, including molecular imaging and drug delivery. Since DNA nanostructures may elicit an immune response in vivo, we also present a short discussion of their potential toxicities in biomedical applications. Lastly, we discuss future perspectives and potential challenges that may limit the effective preclinical and clinical employment of DNA nanostructures. Due to their unique properties, we predict that DNA nanomaterials will make excellent agents for effective diagnostic imaging and drug delivery, improving patient outcome in cancer and other related diseases in the near future.

Understanding Interferon Subtype Therapy for Viral Infections: Harnessing the Power of the Innate Immune System

Type I and III interferons (IFNs) of the innate immune system belong to a polygenic family, however the individual subtype mediators of the antiviral response in viral infections have been hindered by a lack of reagents. Evaluation studies using different IFN subtypes have distinguished distinct protein properties with different efficacies towards different viruses, opening promising avenues for immunotherapy. This review largely focuses on the application of IFN-α/β and IFN-λ therapies for viral infections, influenza, herpes, HIV and hepatitis. Such IFN subtype therapies may help to cure patients with virus infections where no vaccine exists. The ability of cell types to secrete a number of IFN subtypes from a multi-gene family may be an intuitive counterattack on viruses that evade IFN subtype responses. Hence, clinical use of virus-targeted IFN subtypes may restore antiviral immunity in viral infections. Accumulating evidence suggests that individual IFN subtypes have differential efficacies in selectively activating immune cell subsets to enhance antiviral immune responses leading to production of sustained B and T cell memory. Cytokine therapy can augment innate immunity leading to clearance of acute virus infections but such treatments may have limited effects on chronic virus infections that establish lifelong latency. Therefore, exploiting individual IFN subtypes to select those with the ability to sculpt protective responses as well as reinstating those targeted by viral evasion mechanisms may inform development of improved antiviral therapy.

Herpesvirus-Associated Lymphadenitis Distorts Fibroblastic Reticular Cell Microarchitecture and Attenuates CD8 T Cell Responses to Neurotropic Infection in Mice Lacking the STING-IFNα/β Defense Pathways

Type I IFN (IFN-α/β)-driven immune responses to acute viral infection are critical to counter replication and prevent dissemination. However, the mechanisms underlying host resistance to HSV type 1 (HSV-1) are incompletely understood. In this study, we show that mice with deficiencies in IFN-α/β signaling or stimulator of IFN genes (STING) exhibit exacerbated neurovirulence and atypical lymphotropic dissemination of HSV-1 following ocular infection. Synergy between IFN-α/β signaling and efficacy of early adaptive immune responses to HSV-1 were dissected using bone marrow chimeras and adoptive cell transfer approaches to profile clonal expansion, effector function, and recruitment of HSV-specific CD8(+) T cells. Lymphotropic viral dissemination was commensurate with abrogated CD8(+) T cell responses and pathological alterations of fibroblastic reticular cell networks in the draining lymph nodes. Our results show that resistance to HSV-1 in the trigeminal ganglia during acute infection is conferred in part by STING and IFN-α/β signaling in both bone marrow-derived and -resident cells, which coalesce to support a robust HSV-1-specific CD8(+) T cell response.

Cytokine Regulation of Metastasis and Tumorigenicity

The human body combats infection and promotes wound healing through the remarkable process of inflammation. Inflammation is characterized by the recruitment of stromal cell activity including recruitment of immune cells and induction of angiogenesis. These cellular processes are regulated by a class of soluble molecules called cytokines. Based on function, cell target, and structure, cytokines are subdivided into several classes including: interleukins, chemokines, and lymphokines. While cytokines regulate normal physiological processes, chronic deregulation of cytokine expression and activity contributes to cancer in many ways. Gene polymorphisms of all types of cytokines are associated with risk of disease development. Deregulation RNA and protein expression of interleukins, chemokines, and lymphokines have been detected in many solid tumors and hematopoetic malignancies, correlating with poor patient prognosis. The current body of literature suggests that in some tumor types, interleukins and chemokines work against the human body by signaling to cancer cells and remodeling the local microenvironment to support the growth, survival, and invasion of primary tumors and enhance metastatic colonization. Some lymphokines are downregulated to suppress tumor progression by enhancing cytotoxic T cell activity and inhibiting tumor cell survival. In this review, we will describe the structure/function of several cytokine families and review our current understanding on the roles and mechanisms of cytokines in tumor progression. In addition, we will also discuss strategies for exploiting the expression and activity of cytokines in therapeutic intervention.

Mx oligomer: a novel capsid pattern sensor?

Myxovirus resistance proteins represent a family of interferon-induced restriction factors of the innate and adaptive immune system. Human MxB acts as a novel restriction factor with antiviral activity against a range of HIV-1 and other retroviruses mainly by inhibiting the uncoating process after reverse transcription but prior to integration. Based on published data and conservation analysis, we propose a novel hypothesis, in which MxB dimers form higher order oligomers that restrict retroviral replication by binding to the viral capsid. Insights into the mechanistic basis of structural and functional characteristics of MxB will greatly advance our understanding of MxB.

Viruses and the Diversity of Cell Death

Cell death is a common outcome of virus infection. In some cases, cell death curbs virus replication. In others, cell death enhances virus dissemination and contributes to tissue injury, exacerbating viral disease. Three forms of cell death are observed following virus infection-apoptosis, necroptosis, and pyroptosis. In this review, I describe the core machinery needed for each of these forms of cell death. Using representative viruses, I highlight how distinct stages of virus replication initiate signaling pathways that elicit these forms of cell death. I also discuss viral strategies to overcome the deleterious effects of cell death on virus propagation and the consequences of cell death for host physiology.

Oncolytic viruses-immunotherapeutics on the rise

The oncolytic virus (OV) field has entered an exciting period in its evolution in which our basic understanding of viral biology and anti-cancer potential are being actively translated into viable therapeutic options for aggressive malignancies. OVs are naturally occurring or engineered viruses that are able to exploit cancer-specific changes in cellular signaling to specifically target cancers and their microenvironment. The direct cytolytic effect of OVs on cancer cells is known to release antigens, which can begin a cascade of events that results in the induction of anti-cancer adaptive immunity. This response is now regarded as the most critical mechanism of OV action and harnessing it can lead to the elimination of distant micrometastases as well as provide long-term anti-cancer immune surveillance. In this review, we highlight the development of the OV field, why OVs are gaining an increasingly elevated standing as members of the cancer immunotherapy armamentarium, and finally, ongoing clinical studies that are aimed at translating unique OV therapies into approved therapies for aggressive cancers.

Molecular dissection of HBV evasion from restriction factor tetherin: A new perspective for antiviral cell therapy

Viruses have evolved various strategies to escape from the innate cellular mechanisms inhibiting viral replication and spread. Extensive evidence has highlighted the ineffectiveness of interferon (IFN) therapy against chronic hepatitis B virus (HBV) infection, implying the existence of mechanisms by which HBV evades IFN-induced antiviral responses. In our current study, we demonstrate that HBV surface protein (HBs) plays a crucial role in counteracting the IFN-induced antiviral response mediated by tetherin (also known as BST-2). The type I IFN treatment of HBV-producing cells marginally but significantly inhibited the release of HBsAg and viral DNA, but this release was recovered by the knockdown of tetherin. HBs can interact with tetherin via its fourth transmembrane domain thereby inhibiting its dimerization and antiviral activity. The expression of a tetherin mutant devoid of the HBs-binding domain promoted a prominent restriction of HBV particle production that eventually resulted in the alleviation of caspase-1-mediated cytotoxicity and interleukin-1β secretion in induced pluripotent stem cell (iPSC)-derived hepatocytes. Our current results thus reveal a previously undescribed molecular link between HBV and tetherin during the course of an IFN-induced antiviral response. In addition, strategies to augment the antiviral activity of tetherin by impeding tetherin-HBs interactions may be viable as a therapeutic intervention against HBV.

Molecular Mechanisms of Innate Immune Inhibition by Non-Segmented Negative-Sense RNA Viruses

The host innate immune system serves as the first line of defense against viral infections. Germline-encoded pattern recognition receptors detect molecular patterns associated with pathogens and activate innate immune responses. Of particular relevance to viral infections are those pattern recognition receptors that activate type I interferon responses, which establish an antiviral state. The order Mononegavirales is composed of viruses that possess single-stranded, non-segmented negative-sense (NNS) RNA genomes and are important human pathogens that consistently antagonize signaling related to type I interferon responses. NNS viruses have limited encoding capacity compared to many DNA viruses, and as a likely consequence, most open reading frames encode multifunctional viral proteins that interact with host factors in order to evade host cell defenses while promoting viral replication. In this review, we will discuss the molecular mechanisms of innate immune evasion by select NNS viruses. A greater understanding of these interactions will be critical in facilitating the development of effective therapeutics and viral countermeasures.

AIRE-Deficient Patients Harbor Unique High-Affinity Disease-Ameliorating Autoantibodies

APS1/APECED patients are defined by defects in the autoimmune regulator (AIRE) that mediates central T cell tolerance to many self-antigens. AIRE deficiency also affects B cell tolerance, but this is incompletely understood. Here we show that most APS1/APECED patients displayed B cell autoreactivity toward unique sets of approximately 100 self-proteins. Thereby, autoantibodies from 81 patients collectively detected many thousands of human proteins. The loss of B cell tolerance seemingly occurred during antibody affinity maturation, an obligatorily T cell-dependent step. Consistent with this, many APS1/APECED patients harbored extremely high-affinity, neutralizing autoantibodies, particularly against specific cytokines. Such antibodies were biologically active in vitro and in vivo, and those neutralizing type I interferons (IFNs) showed a striking inverse correlation with type I diabetes, not shown by other anti-cytokine antibodies. Thus, naturally occurring human autoantibodies may actively limit disease and be of therapeutic utility.

Clarithromycin prevents human respiratory syncytial virus-induced airway epithelial responses by modulating activation of interferon regulatory factor-3

Macrolide antibiotics exert immunomodulatory activity by reducing pro-inflammatory cytokine production by airway epithelial cells, fibroblasts, vascular endothelial cells, and immune cells. However, the underlying mechanism of action remains unclear. Here, we examined the effect of clarithromycin (CAM) on pro-inflammatory cytokine production, including interferons (IFNs), by primary human nasal epithelial cells and lung epithelial cell lines (A549 and BEAS-2B cells) after stimulation by Toll-like receptor (TLR) and RIG-I-like receptor (RLR) agonists and after infection by human respiratory syncytial virus (RSV). CAM treatment led to a significant reduction in poly I:C- and RSV-mediated IL-8, CCL5, IFN-β and -λ production. Furthermore, IFN-β promoter activity (activated by poly I:C and RSV infection) was significantly reduced after treatment with CAM. CAM also inhibited IRF-3 dimerization and subsequent translocation to the nucleus. We conclude that CAM acts a crucial modulator of the innate immune response, particularly IFN production, by modulating IRF-3 dimerization and subsequent translocation to the nucleus of airway epithelial cells. This newly identified immunomodulatory action of CAM will facilitate the discovery of new macrolides with an anti-inflammatory role.

CD103+ Conventional Dendritic Cells Are Critical for TLR7/9-Dependent Host Defense against Histoplasma capsulatum, an Endemic Fungal Pathogen of Humans

Innate immune cells shape the host response to microbial pathogens. Here we elucidate critical differences in the molecular response of macrophages vs. dendritic cells (DCs) to Histoplasma capsulatum, an intracellular fungal pathogen of humans. It has long been known that macrophages are permissive for Histoplasma growth and succumb to infection, whereas DCs restrict fungal growth and survive infection. We used murine macrophages and DCs to identify host pathways that influence fungal proliferation and host-cell viability. Transcriptional profiling experiments revealed that DCs produced a strong Type I interferon (IFN-I) response to infection with Histoplasma yeasts. Toll-like receptors 7 and 9 (TLR7/9), which recognize nucleic acids, were required for IFN-I production and restriction of fungal growth in DCs, but mutation of TLR7/9 had no effect on the outcome of macrophage infection. Moreover, TLR7/9 were essential for the ability of infected DCs to elicit production of the critical cytokine IFNγ from primed CD4⁺ T cells in vitro, indicating the role of this pathway in T cell activation. In a mouse model of infection, TLR7/9 were required for optimal production of IFN-I and IFNγ, host survival, and restriction of cerebral fungal burden. These data demonstrate the critical role of this pathway in eliciting an appropriate adaptive immune response in the host. Finally, although other fungal pathogens have been shown to elicit IFN-I in mouse models, the specific host cell responsible for producing IFN-I has not been elucidated. We found that CD103⁺ conventional DCs were the major producer of IFN-I in the lungs of wild-type mice infected with Histoplasma. Mice deficient in this DC subtype displayed reduced IFN-I production in vivo. These data reveal a previously unknown role for CD103⁺ conventional DCs and uncover the pivotal function of these cells in modulating the host immune response to endemic fungi.

Innate immune cells such as macrophages and dendritic cells (DCs) are critical elements of the initial response to pathogens. Whereas both of these cell types utilize robust anti-microbial strategies to kill internalized microbes, intracellular pathogens have developed mechanisms to manipulate the host response and survive within host cells. In the case of the intracellular fungal pathogen Histoplasma capsulatum, the fungus proliferates within macrophages, resulting in host-cell lysis. In contrast, DCs are able to restrict Histoplasma growth. Here we discovered that the ability of DCs to produce Type I interferons (IFN-I) is critical to their capacity to restrict fungal proliferation and survive infection. IFN-I are cytokines that are elicited during a variety of viral, bacterial, and fungal infections. We performed in vivo and in vitro experiments to show that pattern recognition receptors TLR7 and TLR9 are critical for the IFN-I response and host survival in the mouse model of infection. Additionally we defined a specific DC subset (CD103⁺ conventional DCs) in the mouse lung that is responsible for the IFN-I response, revealing a previously unknown role for these cells. These data provide insight on the pivotal role of a specific host-response pathway at both a cellular and organismal level during infection with endemic fungi.

Human Coronaviruses: A Review of Virus-Host Interactions

Human coronaviruses (HCoVs) are known respiratory pathogens associated with a range of respiratory outcomes. In the past 14 years, the onset of severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) have thrust HCoVs into spotlight of the research community due to their high pathogenicity in humans. The study of HCoV-host interactions has contributed extensively to our understanding of HCoV pathogenesis. In this review, we discuss some of the recent findings of host cell factors that might be exploited by HCoVs to facilitate their own replication cycle. We also discuss various cellular processes, such as apoptosis, innate immunity, ER stress response, mitogen-activated protein kinase (MAPK) pathway and nuclear factor kappa B (NF-κB) pathway that may be modulated by HCoVs.

Eudistomin C, an Antitumor and Antiviral Natural Product, Targets 40S Ribosome and Inhibits Protein Translation

Eudistomin C (EudiC), a natural product, shows potent antitumor and antiviral activities, but the target molecule and the mechanism of action remain to be revealed. Here, we show that the 40S ribosome is the target in EudiC cytotoxicity. We isolated EudiC-resistant mutants from a multidrug-sensitive yeast strain, and a genetic analysis classified these YER (yeast EudiC resistance) mutants into three complementation groups. A genome-wide study revealed that the YER1-6 mutation is in the uS11 gene (RPS14A). Biotinylated EudiC pulled down Rps14p-containing complexes from 40S and 80S ribosomes, but not from the 60S ribosome. EudiC strongly inhibited translation of the wild-type strain but not of YER1-6 in cells and in vitro. These results indicate that EudiC is a protein synthesis inhibitor targeting the uS11-containing ribosomal subunit, and shows cytotoxicity by inhibiting protein translation.

Distinct Patterns of Expression of Transcription Factors in Response to Interferonβ and Interferonλ1

After viral infection, type I and III interferons (IFNs) are coexpressed by respiratory epithelial cells (RECs) and activate the ISGF3 transcription factor (TF) complex to induce expression of a cell-specific set of interferon-stimulated genes (ISGs). Type I and III IFNs share a canonical signaling pathway, suggesting that they are redundant. Animal and in vitro models, however, have shown that they are not redundant. Because TFs dictate cellular phenotype and function, we hypothesized that focusing on TF-ISG will reveal critical combinatorial and nonredundant functions of type I or III IFN. We treated BEAS-2B human RECs with increasing doses of IFNβ or IFNλ1 and measured expression of TF-ISG. ISGs were expressed in a dose-dependent manner with a nonlinear jump at intermediate doses. At subsaturating combinations of IFNβ and IFNλ1, many ISGs were expressed in a pattern that we modeled with a cubic equation that mathematically defines this threshold effect. Uniquely, IFNβ alone induced early and transient IRF1 transcript and protein expression, while IFNλ1 alone induced IRF1 protein expression at low levels that were sustained through 24 h. In combination, saturating doses of these 2 IFNs together enhanced and sustained IRF1 expression. We conclude that the cubic model quantitates combinatorial effects of IFNβ and IFNλ1 and that IRF1 may mediate nonredundancy of type I or III IFN in RECs.

Full Spectrum of LPS Activation in Alveolar Macrophages of Healthy Volunteers by Whole Transcriptomic Profiling

Despite recent advances in understanding macrophage activation, little is known regarding how human alveolar macrophages in health calibrate its transcriptional response to canonical TLR4 activation. In this study, we examined the full spectrum of LPS activation and determined whether the transcriptomic profile of human alveolar macrophages is distinguished by a TIR-domain-containing adapter-inducing interferon-β (TRIF)-dominant type I interferon signature. Bronchoalveolar lavage macrophages were obtained from healthy volunteers, stimulated in the presence or absence of ultrapure LPS in vitro, and whole transcriptomic profiling was performed by RNA sequencing (RNA-Seq). LPS induced a robust type I interferon transcriptional response and Ingenuity Pathway Analysis predicted interferon regulatory factor (IRF)7 as the top upstream regulator of 89 known gene targets. Ubiquitin-specific peptidase (USP)-18, a negative regulator of interferon α/β responses, was among the top up-regulated genes in addition to IL10 and USP41, a novel gene with no known biological function but with high sequence homology to USP18. We determined whether IRF-7 and USP-18 can influence downstream macrophage effector cytokine production such as IL-10. We show that IRF-7 siRNA knockdown enhanced LPS-induced IL-10 production in human monocyte-derived macrophages, and USP-18 overexpression attenuated LPS-induced production of IL-10 in RAW264.7 cells. Quantitative PCR confirmed upregulation of USP18, USP41, IL10, and IRF7. An independent cohort confirmed LPS induction of USP41 and IL10 genes. These results suggest that IRF-7 and predicted downstream target USP18, both elements of a type I interferon gene signature identified by RNA-Seq, may serve to fine-tune early cytokine response by calibrating IL-10 production in human alveolar macrophages.

The type I interferon signature in leukocyte subsets from peripheral blood of patients with early arthritis: a major contribution by granulocytes

Background

The type I interferon (IFN) signature in rheumatoid arthritis (RA) has shown clinical relevance in relation to disease onset and therapeutic response. Identification of the cell type(s) contributing to this IFN signature could provide insight into the signature’s functional consequences. The aim of this study was to investigate the contribution of peripheral leukocyte subsets to the IFN signature in early arthritis.

Methods

Blood was collected from 26 patients with early arthritis and lysed directly or separated into peripheral blood mononuclear cells (PBMCs) and polymorphonuclear granulocytes (PMNs). PBMCs were sorted into CD4⁺ T cells, CD8⁺ T cells, CD19⁺ B cells, and CD14⁺ monocytes by flow cytometry. Messenger RNA expression of three interferon response genes (IRGs RSAD2, IFI44L, and MX1) and type I interferon receptors (IFNAR1 and IFNAR2) was determined in whole blood and blood cell subsets by quantitative polymerase chain reaction. IRG expression was averaged to calculate an IFN score for each sample.

Results

Patients were designated “IFN^high” (n = 8) or “IFN^low” (n = 18) on the basis of an IFN score cutoff in whole peripheral blood from healthy control subjects. The difference in IFN score between IFN^high and IFN^low patients was remarkably large for the PMN fraction (mean 25-fold) compared with the other subsets (mean 6- to 9-fold), indicating that PMNs are the main inducers of IRGs. Moreover, the relative contribution of the PMN fraction to the whole-blood IFN score was threefold higher than expected from its abundance in blood (p = 0.008), whereas it was three- to sixfold lower for the other subsets (p ≤ 0.063), implying that the PMNs are most sensitive to IFN signaling. Concordantly, IFNAR1 and IFNAR2 were upregulated compared with healthy controls selectively in patient PMNs (p ≤ 0.0077) but not in PBMCs.

Conclusions

PMNs are the main contributors to the whole-blood type I IFN signature in patients with early arthritis, which seems due to increased sensitivity of these cells to type I IFN signaling. Considering the well-established role of neutrophils in the pathology of arthritis, this suggests a role of type I IFN activity in the disease as well.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-1065-3) contains supplementary material, which is available to authorized users.

Type I interferon promotes alveolar epithelial type II cell survival during pulmonary Streptococcus pneumoniae infection and sterile lung injury in mice

Protecting the integrity of the lung epithelial barrier is essential to ensure respiration and proper oxygenation in patients suffering from various types of lung inflammation. Type I interferon (IFN-I) has been associated with pulmonary epithelial barrier function, however, the mechanisms and involved cell types remain unknown. We aimed to investigate the importance of IFN-I with respect to its epithelial barrier strengthening function to better understand immune-modulating effects in the lung with potential medical implications. Using a mouse model of pneumococcal pneumonia, we revealed that IFN-I selectively protects alveolar epithelial type II cells (AECII) from inflammation-induced cell death. Mechanistically, signaling via the IFN-I receptor on AECII is sufficient to promote AECII survival. The net effects of IFN-I are barrier protection, together with diminished tissue damage, inflammation, and bacterial loads. Importantly, we found that the protective role of IFN-I can also apply to sterile acute lung injury, in which loss of IFN-I signaling leads to a significant reduction in barrier function caused by AECII cell death. Our data suggest that IFN-I is an important mediator in lung inflammation that plays a protective role by antagonizing inflammation-associated cell obstruction, thereby strengthening the integrity of the epithelial barrier.

Deletion of the type-1 interferon receptor in APPSWE/PS1ΔE9 mice preserves cognitive function and alters glial phenotype

A neuro-inflammatory response is evident in Alzheimer’s disease (AD), yet the precise mechanisms by which neuro-inflammation influences the progression of Alzheimer’s disease (AD) remain poorly understood. Type-1 interferons (IFNs) are master regulators of innate immunity and have been implicated in multiple CNS disorders, however their role in AD progression has not yet been fully investigated. Hence, we generated APP_SWE/PS1_ΔE9 mice lacking the type-1 IFN alpha receptor-1 (IFNAR1, APP_SWE/PS1_ΔE9 x IFNAR1^−/−) aged to 9 months to investigate the role of type-1 IFN signaling in a well-validated model of AD. APP_SWE/PS1_ΔE9 x IFNAR1^−/− mice displayed a modest reduction in Aβ monomer levels, despite maintenance of plaque deposition. This finding correlated with partial rescue of spatial learning and memory impairments in the Morris water maze in comparison to APP_SWE/PS1_ΔE9 mice. Q-PCR identified a reduced type-1 IFN response and modulated pro-inflammatory cytokine secretion in APP_SWE/PS1_ΔE9 x IFNAR1^−/− mice compared to APP_SWE/PS1_ΔE9 mice. Interestingly, immunohistochemistry displayed enhanced astrocyte reactivity but attenuated microgliosis surrounding amyloid plaque deposits in APP_SWE/PS1_ΔE9 x IFNAR1^−/− mice in comparison to APP_SWE/PS1_ΔE9 mice. These APP_SWE/PS1_ΔE9 x IFNAR1^−/− microglial populations demonstrated an anti-inflammatory phenotype that was confirmed in vitro by soluble Aβ1-42 treatment of IFNAR1^−/− primary glial cultures. Our findings suggest that modulating neuro-inflammatory responses by suppressing type-1 IFN signaling may provide therapeutic benefit in AD.

The expanding regulatory network of STING-mediated signaling

The identification and characterization of DNA-sensing pathways has been a subject of intensive investigation for the last decade. This interest, in part, is supported by the fact that the main outcome of DNA-responses is production of type I interferon (IFN-I), which, if produced in excessive amounts, leads to various pathologies. STING (stimulator of interferon genes) is positioned in the center of these responses and is activated either via direct sensing of second messengers or via interaction with upstream sensors of dsDNA. STING mediates responses to pathogens as well as host-derived DNA and is, therefore, linked to various autoimmune diseases, cancer predisposition and ageing. Recent mouse models of DNA damage showed the adaptor STING to be crucial for heightened resting levels of IFN-I. In this review, we will focus on recent advances in understanding the regulation of STING-signaling and identification of its novel components.

HCV RNA Activates APCs via TLR7/TLR8 While Virus Selectively Stimulates Macrophages Without Inducing Antiviral Responses

The innate and adaptive immune systems fail to control HCV infection in the majority of infected individuals. HCV is an ssRNA virus, which suggests a role for Toll-like receptors (TLRs) 7 and 8 in initiating the anti-viral response. Here we demonstrate that HCV genomic RNA harbours specific sequences that initiate an anti-HCV immune response through TLR7 and TLR8 in various antigen presenting cells. Conversely, HCV particles are detected by macrophages, but not by monocytes and DCs, through a TLR7/8 dependent mechanism; this leads to chloroquine sensitive production of pro-inflammatory cytokines including IL-1β, while the antiviral type I Interferon response is not triggered in these cells. Antibodies to DC-SIGN, a c-type lectin selectively expressed by macrophages but not pDCs or mDCs, block the production of cytokines. Novel anti-HCV vaccination strategies should target the induction of TLR7/8 stimulation in APCs in order to establish potent immune responses against HCV.

JC Polyomavirus Infection of Primary Human Renal Epithelial Cells Is Controlled by a Type I IFN-Induced Response

The JC and BK human polyomaviruses (JCPyV and BKPyV, respectively) establish lifelong persistent infections in the kidney. In immunosuppressed individuals, JCPyV causes progressive multifocal leukoencephalopathy (PML), a fatal neurodegenerative disease, and BKPyV causes polyomavirus-associated nephropathy (PVN). In this study, we compared JCPyV and BKPyV infections in primary human renal proximal tubule epithelial (HRPTE) cells. JCPyV established a persistent infection, but BKPyV killed the cells in 15 days. To identify the cellular factors responsible for controlling JCPyV infection and promoting viral persistence, we profiled the transcriptomes of JCPyV- and BKPyV-infected cells at several time points postinfection. We found that infection with both viruses induced interferon production but that interferon-stimulated genes (ISGs) were only activated in the JCPyV-infected cells. Phosphorylated STAT1 and IRF9, which are responsible for inducing ISGs, translocated to the nucleus of JCPyV-infected cells but did not in BKPyV-infected cells. In BKPyV-infected cells, two critical suppressors of cytokine signaling, SOCS3 and SOCS1, were induced. Infection with BKPyV but not JCPyV caused reorganization of PML bodies that are associated with inactivating antiviral responses. Blockade of the interferon receptor and neutralization of soluble interferon alpha (IFN-α) and IFN-β partially alleviated the block to JCPyV infection, leading to enhanced infectivity. Our results show that a type I IFN response contributes to the establishment of persistent infection by JCPyV in HRPTE cells.

The human polyomaviruses JCPyV and BKPyV both establish lifelong persistent infection in the kidneys. In immunosuppressed patients, BKPyV causes significant pathology in the kidney, but JCPyV is only rarely associated with disease in this organ. The reasons behind this striking difference in kidney pathology are unknown. In this study, we show that infection of primary human renal tubule epithelial cells with JCPyV and BKPyV results in divergent innate immune responses that control JCPyV but fail to control BKPyV. This is the first study that directly compares JCPyV and BKPyV infection in vitro in the same cell type they naturally infect, and the significant differences that have been uncovered could in part explain the distinct disease outcomes.

Transcriptome analysis of genes responding to NNV infection in Asian seabass epithelial cells

Asian seabass is an important food fish in Southeast Asia. Viral nervous necrosis (VNN) disease, triggered by nervous necrosis virus (NNV) infection, has caused mass mortality of Asian seabass larvae, resulting in enormous economic losses in the Asian seabass industry. In order to better understand the complex molecular interaction between Asian seabass and NNV, we investigated the transcriptome profiles of Asian seabass epithelial cells, which play an essential role in immune regulation, after NNV infection. Using the next generation sequencing (NGS) technology, we sequenced mRNA from eight samples (6, 12, 24, 48 h post-inoculation) of mock and NNV-infected Asian seabass epithelial cell line, respectively. Clean reads were de novo assembled into a transcriptome consisting of 89026 transcripts with a N50 of 2617 bp. Furthermore, 251 differentially expressed genes (DEGs) in response to NNV infection were identified. Top DEGs include protein asteroid homolog 1-like (ASTE1), receptor-transporting protein 3 (RTP3), heat shock proteins 30 (HSP30) and 70 (HSP70), Viperin, interferon regulatory factor 3 (IRF3) and other genes related to innate immunity. Our data suggest that abundant and diverse genes corresponding to NNV infection. The results of this study could also offer vital information not only for identification of novel genes involved in Asian seabass-NNV interaction, but also for our understanding of the molecular mechanism of Asian seabass' response to viral infection. In addition, 24807 simple sequence repeats (SSRs) were detected in the assembled transcriptome, providing valuable resources for studying genetic variations and accelerating quantitative trait loci (QTL) mapping for disease resistance in Asian seabass in the future.

Approved Antiviral Drugs over the Past 50 Years

Since the first antiviral drug, idoxuridine, was approved in 1963, 90 antiviral drugs categorized into 13 functional groups have been formally approved for the treatment of the following 9 human infectious diseases: (i) HIV infections (protease inhibitors, integrase inhibitors, entry inhibitors, nucleoside reverse transcriptase inhibitors, nonnucleoside reverse transcriptase inhibitors, and acyclic nucleoside phosphonate analogues), (ii) hepatitis B virus (HBV) infections (lamivudine, interferons, nucleoside analogues, and acyclic nucleoside phosphonate analogues), (iii) hepatitis C virus (HCV) infections (ribavirin, interferons, NS3/4A protease inhibitors, NS5A inhibitors, and NS5B polymerase inhibitors), (iv) herpesvirus infections (5-substituted 2'-deoxyuridine analogues, entry inhibitors, nucleoside analogues, pyrophosphate analogues, and acyclic guanosine analogues), (v) influenza virus infections (ribavirin, matrix 2 protein inhibitors, RNA polymerase inhibitors, and neuraminidase inhibitors), (vi) human cytomegalovirus infections (acyclic guanosine analogues, acyclic nucleoside phosphonate analogues, pyrophosphate analogues, and oligonucleotides), (vii) varicella-zoster virus infections (acyclic guanosine analogues, nucleoside analogues, 5-substituted 2'-deoxyuridine analogues, and antibodies), (viii) respiratory syncytial virus infections (ribavirin and antibodies), and (ix) external anogenital warts caused by human papillomavirus infections (imiquimod, sinecatechins, and podofilox). Here, we present for the first time a comprehensive overview of antiviral drugs approved over the past 50 years, shedding light on the development of effective antiviral treatments against current and emerging infectious diseases worldwide.

Antidepressant therapies inhibit inflammation and microglial M1-polarization

Macrophages and their counterparts in the central nervous system, the microglia, detect and subsequently clear microbial pathogens and injured tissue. These phagocytic cells alter and adapt their phenotype depending on their prime activity, i.e., whether they participate in acute defence against pathogenic organisms ('M1'-phenotype) or in clearing damaged tissues and performing repair activities ('M2'-phenotype). Stimulation of pattern recognition receptors by viruses (vaccines), bacterial membrane components (e.g., LPS), alcohol, or long-chain saturated fatty acids promotes M1-polarization. Vaccine or LPS administration to healthy human subjects can result in sickness symptoms and low mood. Alcohol abuse and abdominal obesity are recognized as risk factors for depression. In the M1-polarized form, microglia and macrophages generate reactive oxygen and nitrogen radicals to eradicate microbial pathogens. Inadvertently, also tetrahydrobiopterin (BH4) may become oxidized. This is an irreversible reaction that generates neopterin, a recognized biomarker for depression. BH4 is a critical cofactor for the synthesis of dopamine, noradrenaline, and serotonin, and its loss could explain some of the symptoms of depression. Based on these aspects, the suppression of M1-polarization would limit the inadvertent catabolism of BH4. In the current review, we evaluate the evidence that antidepressant treatments (monoamine reuptake inhibitors, PDE4 inhibitors, lithium, valproate, agomelatine, tianeptine, electroconvulsive shock, and vagus nerve stimulation) inhibit LPS-induced microglia/macrophage M1-polarization. Consequently, we propose that supplementation with BH4 could limit the reduction in central monoamine synthesis and might represent an effective treatment for depressed mood.

A STING-dependent innate-sensing pathway mediates resistance to corneal HSV-1 infection via upregulation of the antiviral effector tetherin

Type 1 interferons (IFNs; IFNα/β) mediate immunological host resistance to numerous viral infections, including herpes simplex virus type 1 (HSV-1). The pathways responsible for IFNα/β signaling during the innate immune response to acute HSV-1 infection in the cornea are incompletely understood. Using a murine ocular infection model, we hypothesized that the stimulator of IFN genes (STING) mediates resistance to HSV-1 infection at the ocular surface and preserves the structural integrity of this mucosal site. Viral pathogenesis, tissue pathology, and host immune responses during ocular HSV-1 infection were characterized by plaque assay, esthesiometry, pachymetry, immunohistochemistry, flow cytometry, and small interfering RNA transfection in wild-type C57BL/6 (WT), STING-deficient (STING(-/-)), and IFNα/β receptor-deficient (CD118(-/-)) mice at days 3-5 postinfection. The presence of STING was critical for sustained control of HSV-1 replication in the corneal epithelium and resistance to viral neuroinvasion, but loss of STING had a negligible impact with respect to gross tissue pathology. Auxiliary STING-independent IFNα/β signaling pathways were responsible for maintenance of corneal integrity. Lymphatic vessels, mast cells, and sensory innervation were compromised in CD118(-/-) mice concurrent with increased tissue edema. STING-dependent signaling led to the upregulation of tetherin, a viral restriction factor we identify is important in containing the spread of HSV-1 in vivo.

Targeted immunotherapy using anti-CD138-interferon α fusion proteins and bortezomib results in synergistic protection against multiple myeloma

Although recent advances have substantially improved the management of multiple myeloma, it remains an incurable malignancy. We now demonstrate that anti-CD138 molecules genetically fused to type I interferons (IFN) synergize with the approved therapeutic bortezomib in arresting the proliferation of human multiple myeloma cell lines both in vitro and in vivo. The anti-CD138-IFNα14 fusion protein was active in inducing increased expression of signal transducer and activator of transcription 1 (STAT1) and its phosphorylation while the cell death pathway induced by bortezomib included generation of reactive oxygen species. Interferon regulatory factor 4 (IRF4), an important survival factor for myeloma cells, was down regulated following combination treatment. Induction of cell death appeared to be caspase-independent because treatment with inhibitors of caspase activation did not decrease the level of cell death. The observed caspase-independent synergistic cell death involved mitochondrial membrane depolarization, and poly(ADP-ribose) polymerase-1 (PARP-1) cleavage, and resulted in enhanced induction of apoptosis. Importantly, using 2 different in vivo xenograft models, we found that combination therapy of anti-CD138-IFNα14 and bortezomib was able to cure animals with established tumors (7 of 8 using OCI-My5 or 8 of 8 using NCI-H929). Thus, the combination of anti-CD138-IFNα with bortezomib shows great promise as a novel therapeutic approach for the treatment of multiple myeloma, a malignancy for which there are currently no cures.

Expansion of amphibian intronless interferons revises the paradigm for interferon evolution and functional diversity

Interferons (IFNs) are key cytokines identified in vertebrates and evolutionary dominance of intronless IFN genes in amniotes is a signature event in IFN evolution. For the first time, we show that the emergence and expansion of intronless IFN genes is evident in amphibians, shown by 24–37 intronless IFN genes in each frog species. Amphibian IFNs represent a molecular complex more complicated than those in other vertebrate species, which revises the established model of IFN evolution to facilitate re-inspection of IFN molecular and functional diversity. We identified these intronless amphibian IFNs and their intron-containing progenitors, and functionally characterized constitutive and inductive expression and antimicrobial roles in infections caused by zoonotic pathogens, such as influenza viruses and Listeria monocytogenes. Amphibians, therefore, may serve as overlooked vectors/hosts for zoonotic pathogens, and the amphibian IFN system provides a model to study IFN evolution in molecular and functional diversity in coping with dramatic environmental changes during terrestrial adaption.

Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus Nsp4 Cleaves VISA to Impair Antiviral Responses Mediated by RIG-I-like Receptors

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most significant etiological agents in the swine industry worldwide. It has been reported that PRRSV infection can modulate host immune responses, and innate immune evasion is thought to play a vital role in PRRSV pathogenesis. In this study, we demonstrated that highly pathogenic PRRSV (HP-PRRSV) infection specifically down-regulated virus-induced signaling adaptor (VISA), a unique adaptor molecule that is essential for retinoic acid induced gene-I (RIG-I) and melanoma differentiation associated gene 5 (MDA5) signal transduction. Moreover, we verified that nsp4 inhibited IRF3 activation induced by signaling molecules, including RIG-I, MDA5, VISA, and TBK1, but not IRF3. Subsequently, we demonstrated that HP-PRRSV nsp4 down-regulated VISA and suppressed type I IFN induction. Importantly, VISA was cleaved by nsp4 and released from mitochondrial membrane, which interrupted the downstream signaling of VISA. However, catalytically inactive mutant of nsp4 abolished its ability to cleave VISA. Interestingly, nsp4 of typical PRRSV strain CH-1a had no effect on VISA. Taken together, these findings reveal a strategy evolved by HP-PRRSV to counteract anti-viral innate immune signaling, which complements the known PRRSV-mediated immune-evasion mechanisms.

The Type I Interferon-IRF7 Axis Mediates Transcriptional Expression of Usp25 Gene

Viral infection or lipopolysaccharide (LPS) treatment induces expression of a large array of genes, the products of which play a critical role in host antipathogen immunity and inflammation. We have previously reported that the expression of ubiquitin-specific protease 25 (USP25) is significantly up-regulated after viral infection or LPS treatment, and this is essential for innate immune signaling. However, the mechanism behind this phenomenon is unclear. In this study, we found that viral infection-induced up-regulation of Usp25 is diminished in cells lacking interferon regulatory factor 7 (IRF7) or interferon α receptor 1 (IFNAR1) but not p65. Sendai virus- or type I interferon-induced up-regulation of Usp25 requires de novo protein synthesis of IRF7. Furthermore, IRF7 directly binds to the two conserved IRF binding sites on the USP25 promoter to drive transcription of Usp25, and mutation of these two sites abolished Sendai virus-induced IRF7-mediated activation of the USP25 promoter. Our study has uncovered a previously unknown mechanism by which viral infection or LPS induces up-regulation of USP25.

Porcine reproductive and respiratory syndrome virus (PRRSV) up-regulates IL-15 through PKCβ1-TAK1-NF-κB signaling pathway

Porcine reproductive and respiratory syndrome (PRRS) caused by PRRS virus (PRRSV) is one of the most important infectious diseases in swine industry. IL-15 is a pleiotropic cytokine and has been shown to be essential to transform NKs, CD8 T cells, and other cells of the immune systems into functional effectors. Here, we demonstrated that the broad-spectrum or conventional PKC inhibitors repressed PRRSV-induced IL-15 expression and NF-κB activation. Subsequently, we found that the PKCβ specific inhibitor inhibited PRRSV-induced IL-15 production, which was also confirmed by knock-down of PKCβ1, suggesting that PKCβ1 is involved in the PRRSV-induced IL-15 expression. In addition, we demonstrated that PRRSV activated NF-κB through PKCβ1-induced TAK1 activation. Finally, we demonstrated that PRRSV activated PKCβ1 dependent on the participation of TRIF and MAVS. These data indicate that PRRSV up-regulates IL-15 through TRIF/MAVS-PKCβ1-TAK1-NF-κB signaling pathway. These findings will provide new insights into the molecular mechanisms of IL-15 production induced by PRRSV.

Age, serum 25-hydroxyvitamin D and vitamin D receptor (VDR) expression and function in peripheral blood mononuclear cells

The relationship between age, vitamin D status, expression and functionality of the vitamin D receptor (VDR), and key genes in the vitamin D pathway in immune cells is unclear. We enrolled adults 50 to 69 years old (20 subjects) and 70+ (20 subjects) and measured: 1) 25(OH)D levels by liquid chromatography/mass spectrometry; and 2) mRNA expression of VDR, 1α-OHase, 1,25D3-MARRS, TREM-1, cathelicidin, RIG-I, and interferon-β by qRT-PCR. Mean serum 25(OH)D was 30 ± 4 ng/mL and was not associated with age. Baseline expression of VDR, 1α-OHase, 1,25D3-MARRS, TREM-1, and RIG-I also did not differ by age; IFN-β expression, however, was higher in the 70+ year old group. 25(OH)D3- and 1,25(OH)2D3-induced VDR, TREM-1 and cathelicidin expression were similar between age groups, as was LPS-induced expression of VDR and of 1α-OHase. Ligand-induced 1,25D3-MARRS expression was higher in subjects ≥ 70 years. Serum 25(OH)D was inversely associated with LPS-stimulated VDR expression and with baseline or vitamin D-induced TREM-1 expression, adjusting for age, self-rated health, and functional status. In healthy adults ≥ 50 years, the expression and functionality of the VDR, 1α-OHase and key vitamin D pathway genes were not consistently associated with age.

Role for phospholipid acyl chains and cholesterol in pulmonary infections and inflammation

Review on how complex mixtures of bioactive lipids and cholesterol may influence the pulmonary immune response during infection.

Bacterial and viral respiratory tract infections result in millions of deaths worldwide and are currently the leading cause of death from infection. Acute inflammation is an essential element of host defense against infection, but can be damaging to the host when left unchecked. Effective host defense requires multiple lipid mediators, which collectively have proinflammatory and/or proresolving effects on the lung. During pulmonary infections, phospholipid acyl chains and cholesterol can be chemically and enzymatically oxidized, as well as truncated and modified, producing complex mixtures of bioactive lipids. We review recent evidence that phospholipids and cholesterol and their derivatives regulate pulmonary innate and adaptive immunity during infection. We first highlight data that oxidized phospholipids generated in the lung during infection stimulate pattern recognition receptors, such as TLRs and scavenger receptors, thereby amplifying the pulmonary inflammatory response. Next, we discuss evidence that oxidation of endogenous pools of cholesterol during pulmonary infections produces oxysterols that also modify the function of both innate and adaptive immune cells. Last, we conclude with data that n‐3 polyunsaturated fatty acids, both in the form of phospholipid acyl chains and through enzymatic processing into endogenous proresolving lipid mediators, aid in the resolution of lung inflammation through distinct mechanisms. Unraveling the complex mechanisms of induction and function of distinct classes of bioactive lipids, both native and modified, may hold promise for developing new therapeutic strategies for improving pulmonary outcomes in response to infection.

Parsing the Interferon Transcriptional Network and Its Disease Associations

Type 1 interferon (IFN) is a key mediator of organismal responses to pathogens, eliciting prototypical "interferon signature genes" that encode antiviral and inflammatory mediators. For a global view of IFN signatures and regulatory pathways, we performed gene expression and chromatin analyses of the IFN-induced response across a range of immunocyte lineages. These distinguished ISGs by cell-type specificity, kinetics, and sensitivity to tonic IFN and revealed underlying changes in chromatin configuration. We combined 1,398 human and mouse datasets to computationally infer ISG modules and their regulators, validated by genetic analysis in both species. Some ISGs are controlled by Stat1/2 and Irf9 and the ISRE DNA motif, but others appeared dependent on non-canonical factors. This regulatory framework helped to interpret JAK1 blockade pharmacology, different clusters being affected under tonic or IFN-stimulated conditions, and the IFN signatures previously associated with human diseases, revealing unrecognized subtleties in disease footprints, as affected by human ancestry.

The Roles of Type I Interferon in Bacterial Infection

Type I interferons (IFNs) are pleiotropic cytokines well recognized for their role in the induction of a potent antiviral gene program essential for host defense against viruses. They also modulate innate and adaptive immune responses. However, the role of type I IFNs in host defense against bacterial infections is enigmatic. Depending on the bacterium, they exert seemingly opposite and capricious functions. In this review, we summarize the effect of type I IFNs on specific bacterial infections and highlight the effector mechanisms regulated by type I IFNs in an attempt to elucidate new avenues to understanding their role.

Beyond autophagy: New roles for ULK1 in immune signaling and interferon responses

The human serine/threonine kinase ULK1 is the human homolog of the Caenorhabditis elegans Unc-51 kinase and of the Saccharomyces cerevisiae autophagy-related protein kinase Atg1. As Unc-51 and Atg1, ULK1 regulates both axon growth and autophagy, respectively, in mammalian cells. However, a novel immunoregulatory role of ULK1 has been recently described. This kinase was shown to be required for regulation of both type I interferon (IFN) production and induction of type I IFN signaling. Optimal regulation of IFN production is crucial for generation of effective IFN-immune responses, and defects in such networks can be detrimental for the host leading to uncontrolled pathogen infection, tumor growth, or autoimmune diseases. Thus, ULK1 plays a central role in IFN-dependent immunity. Here we review the diverse roles of ULK1, with special focus on its importance to type I IFN signaling, and highlight important future study questions.

Adjuvant treatment for stage III melanoma in the era of targeted medicine and immunotherapy

The accelerated development in the treatment of metastatic melanoma, both in molecular targeted therapy and immunotherapy, is already starting to impact on adjuvant therapy in stage III melanoma. Following the approval of ipilimumab for adjuvant therapy in melanoma, clinical trials assessing other checkpoint modulators and MAPK pathway inhibitors as adjuvant treatments for melanoma are currently ongoing. As results from these trials mature in the next few years, a change in the landscape of adjuvant treatment for melanoma is expected, resulting in new challenges in treatment decisions such as optimizing patients selection through predictive and prognostic biomarkers, and management of treatment related adverse events, in particular immune related toxicities.