IFN-α Enhances TLR3-Mediated Antiviral Cytokine Expression in Human Endothelial and Epithelial Cells by Up-Regulating TLR3 Expression

Interferons prime the endothelium for toll-like receptor-mediated thrombin generation

BACKGROUND

Respiratory infection is associated with microvascular thrombus formation and marked elevation in cytokine levels. The role of cytokines elaborated by the pulmonary epithelium in thrombotic responses is poorly understood.

OBJECTIVES

Our goal was to identify cytokines of pulmonary epithelial cell origin that enhance thrombin generation in the endothelium at concentrations equal to or less than those found in the circulation during infection.

METHODS

We screened multiple cytokines produced by the pulmonary epithelium for the ability to enhance toll-like receptor (TLR)-mediated endothelial thrombin generation. Effects of cytokines on tissue factor and thrombomodulin expression, cytokine selectivity for different TLRs, and prothrombotic activity of endogenous cytokines in conditioned medium from pulmonary human epithelial cells were evaluated.

RESULTS

MIP-1β, MCP-1, IL-10, IL-6, IL-1β, TNFα, IFNα, IFNβ, and IFNγ were tested for their ability to enhance TLR3-mediated thrombin generation on endothelial cells. Only interferons (IFNs) and TNFα promoted TLR3-mediated thrombin generation at levels that circulate during infection. IFNs robustly enhanced tissue factor expression when used in conjunction with TLR agonists and reduced thrombomodulin expression in the endothelium independently of TLRs. IFNα, which is typically elevated with viral infection, only synergized with TLR3 agonists mimicking viral pathogen-associated molecular patterns. In contrast, IFNγ, which is typically observed in bacterial infection, synergized more effectively with TLR4 agonists released by bacteria. Conditioned media from inflamed pulmonary epithelial cells primed the endothelium for TLR-mediated thrombin generation. Anti-IFN type I antibodies blocked this effect, indicating that endogenous IFNs prime the endothelium for TLR-mediated thrombin generation.

CONCLUSION

IFNs elaborated by the pulmonary epithelium are necessary and sufficient to enhance TLR-mediated thrombin generation.

A Razor's Edge: Vascular Responses to Acute Inflammatory Lung Injury/Acute Respiratory Distress Syndrome

Historically considered a metabolically inert cellular layer separating the blood from the underlying tissue, the endothelium is now recognized as a highly dynamic, metabolically active tissue that is critical to organ homeostasis. Under homeostatic conditions, lung endothelial cells (ECs) in healthy subjects are quiescent, promoting vasodilation, platelet disaggregation, and anti-inflammatory mechanisms. In contrast, lung ECs are essential contributors to the pathobiology of acute respiratory distress syndrome (ARDS), as the quiescent endothelium is rapidly and radically altered upon exposure to environmental stressors, infectious pathogens, or endogenous danger signals into an effective and formidable regulator of innate and adaptive immunity. These dramatic perturbations, produced in a tsunami of inflammatory cascade activation, result in paracellular gap formation between lung ECs, sustained lung edema, and multi-organ dysfunction that drives ARDS mortality. The astonishing plasticity of the lung endothelium in negotiating this inflammatory environment and efforts to therapeutically target the aberrant ARDS endothelium are examined in further detail in this review.

Systemic infusion of TLR3-ligand and IFN-α in patients with breast cancer reprograms local tumor microenvironments for selective CTL influx

BACKGROUND

Presence of cytotoxic T lymphocytes (CTL) in the tumor microenvironment (TME) predicts the effectiveness of cancer immunotherapies. The ability of toll-like receptor 3 (TLR3) ligands, interferons (IFNs) and COX2 inhibitors to synergistically induce CTL-attracting chemokines (but not regulatory T cell (Treg)-attractants) in the TME, but not in healthy tissues, observed in our preclinical studies, suggested that their systemic application can reprogram local TMEs.

METHODS

Six evaluable patients (33-69 years) with metastatic triple-negative breast cancer received six doses of systemic chemokine-modulating (CKM) regimen composed of TLR3 ligand (rintatolimod; 200 mg; intravenous), IFN-α2b (20 MU/m2; intravenous) and COX2 inhibitor (celecoxib; 2×200 mg; oral) over 2 weeks. The predetermined primary endpoint was the intratumoral change in the expression of CTL marker, CD8α, in the post-CKM versus pre-CKM tumor biopsies. Patients received follow-up pembrolizumab (200 mg, intravenously, every 3 weeks), starting 3-8 days after completion of CKM.

RESULTS

Post-CKM biopsies showed selectively increased CTL markers CD8α (average 10.2-fold, median 5.5-fold, p=0.034) and granzyme B (GZMB; 6.1-fold, median 5.8-fold, p=0.02), but not FOXP3 (Treg marker) relative to HPRT1 expression, resulting in the increases in average CD8α/FOXP3 ratio and GZMB/FOXP3 ratio. CKM increased intratumoral CTL-attractants CCL5 and CXCL10, but not Treg-attractants CCL22 or CXCL12. In contrast, CD8+ T cells and their CXCR3+ subset showed transient decreases in blood. One clinical response (breast tumor autoamputation) and three stable diseases were observed. The patient with clinical response remains disease free, with a follow-up of 46 months as of data cut-off.

CONCLUSIONS

Short-term systemic CKM selectively increases CTL numbers and CTL/Treg ratios in the TME, while transiently decreasing CTL numbers in the blood. Transient effects of CKM suggest that its simultaneous application with checkpoint blockade and other forms of immunotherapy may be needed for optimal outcomes.

Activation of Toll-like receptor 3 inhibits HIV infection of human iPSC-derived microglia

As a key immune cell in the brain, microglia are essential for protecting the central nervous system (CNS) from viral infections, including HIV. Microglia possess functional Toll-like receptor 3 (TLR3), a key viral sensor for activating interferon (IFN) signaling pathway-mediated antiviral immunity. We, therefore, studied the effect of poly (I:C), a synthetic ligand of TLR3, on the activation of the intracellular innate immunity against HIV in human iPSC-derived microglia (iMg). We found that poly (I:C) treatment of iMg effectively inhibits HIV infection/replication at both mRNA and protein levels. Investigations of the mechanisms revealed that TLR3 activation of iMg by poly (I:C) induced the expression of both type I and type III IFNs. Compared with untreated cells, the poly (I:C)-treated iMg expressed significantly higher levels of IFN-stimulated genes (ISGs) with known anti-HIV activities (ISG15, MxB, Viperin, MxA, and OAS-1). In addition, TLR3 activation elicited the expression of the HIV entry coreceptor CCR5 ligands (CC chemokines) in iMg. Furthermore, the transcriptional profile analysis showed that poly (I:C)-treated cells had the upregulated IFN signaling genes (ISG15, ISG20, IFITM1, IFITM2, IFITM3, IFITM10, APOBEC3A, OAS-2, MxA, and MxB) and the increased CC chemokine signaling genes (CCL1, CCL2, CCL3, CCL4, and CCL15). These observations indicate that TLR3 is a potential therapy target for activating the intracellular innate immunity against HIV infection/replication in human microglial cells. Therefore, further studies with animal models and clinical specimens are necessary to determine the role of TLR3 activation-driven antiviral response in the control and elimination of HIV in infected host cells.

A surgically optimized intraoperative poly(I:C)-releasing hydrogel prevents cancer recurrence

Recurrences frequently occur following surgical removal of primary tumors. In many cancers, adjuvant therapies have limited efficacy. Surgery provides access to the tumor microenvironment, creating an opportunity for local therapy, in particular immunotherapy, which can induce local and systemic anti-cancer effects. Here, we develop a surgically optimized biodegradable hyaluronic acid-based hydrogel for sustained intraoperative delivery of Toll-like receptor 3 agonist poly(I:C) and demonstrate that it significantly reduces tumor recurrence after surgery in multiple mouse models. Mechanistically, poly(I:C) induces a transient interferon alpha (IFNα) response, reshaping the tumor/wound microenvironment by attracting inflammatory monocytes and depleting regulatory T cells. We demonstrate that a pre-existing IFN signature predicts response to the poly(I:C) hydrogel, which sensitizes tumors to immune checkpoint therapy. The safety, immunogenicity, and surgical feasibility are confirmed in a veterinary trial in canine soft tissue tumors. The surgically optimized poly(I:C)-loaded hydrogel provides a safe and effective approach to prevent cancer recurrence.

TL-532, a novel specific Toll-like receptor 3 agonist rationally designed for targeting cancers: discovery process and biological characterization

Toll-like receptor 3 (TLR3) is an innate immune receptor that recognizes double-stranded RNA (dsRNA) and induces inflammation in immune and normal cells to initiate anti-microbial responses. TLR3 acts also as a death receptor only in cancer cells but not in their normal counterparts, making it an attractive target for cancer therapies. To date, all of the TLR3-activating dsRNAs used at preclinical or clinical stages have major drawbacks such as structural heterogeneity, toxicity, and lack of specificity and/or efficacy. We conducted the discovery process of a new family of TLR3 agonists that are chemically manufactured on solid-phase support and perfectly defined in terms of sequence and size. A stepwise discovery process was performed leading to the identification of TL-532, a 70 base pair dsRNA that is potent without transfection reagent and is highly specific for TLR3 without activating other innate nucleic sensors such as RIG-I/MDA5, TLR7, TLR8, and TLR9. TL-532 induces inflammation in murine RAW264.7 myeloid macrophages, in human NCI-H292 lung cancer cells, and it promotes immunogenic apoptosis in tumor cells in vitro and ex vivo without toxicity towards normal primary cells. In conclusion, we identified a novel TLR3 agonist called TL-532 that has promising anticancer properties.

Pellino3 ligase negatively regulates influenza B dependent RIG-I signalling through downregulation of TRAF3-mediated induction of the transcription factor IRF3 and IFNβ production

Viral infection activates the innate immune system, which recognizes viral components by a variety of pattern recognition receptors and initiates signalling cascades leading to the production of pro-inflammatory cytokines. To date, signalling cascades triggered after virus recognition are not fully characterized and are investigated by many research groups. The critical role of the E3 ubiquitin ligase Pellino3 in antibacterial and antiviral response is now widely accepted, but the precise mechanism remains elusive. In this study, we sought to explore Pellino3 role in the retinoic acid-inducible gene I (RIG-I)-dependent signalling pathway. In this work, the molecular mechanisms of the innate immune response, regulated by Pellino3, were investigated in lung epithelial cells during influenza B virus infection. We used wild-type and Pellino3-deficient A549 cells as model cell lines to examine the role of Pellino3 ligase in the type I interferon (IFN) signalling pathway. Our results indicate that Pellino3 is involved in direct ubiquitination and degradation of the TRAF3, suppressing interferon regulatory factor 3 (IRF3) activation and interferon beta (IFNβ) production.

The Latest Approach of Immunotherapy with Endosomal TLR Agonists Improving NK Cell Function: An Overview

Toll-like receptors (TLRs) are the most well-defined pattern recognition receptors (PRR) of several cell types recognizing pathogens and triggering innate immunity. TLRs are also expressed on tumor cells and tumor microenvironment (TME) cells, including natural killer (NK) cells. Cell surface TLRs primarily recognize extracellular ligands from bacteria and fungi, while endosomal TLRs recognize microbial DNA or RNA. TLR engagement activates intracellular pathways leading to the activation of transcription factors regulating gene expression of several inflammatory molecules. Endosomal TLR agonists may be considered as new immunotherapeutic adjuvants for dendritic cell (DC) vaccines able to improve anti-tumor immunity and cancer patient outcomes. The literature suggests that endosomal TLR agonists modify TME on murine models and human cancer (clinical trials), providing evidence that locally infused endosomal TLR agonists may delay tumor growth and induce tumor regression. Recently, our group demonstrated that CD56^bright NK cell subset is selectively responsive to TLR8 engagement. Thus, TLR8 agonists (loaded or not to nanoparticles or other carriers) can be considered a novel strategy able to promote anti-tumor immunity. TLR8 agonists can be used to activate and expand in vitro circulating or intra-tumoral NK cells to be adoptively transferred into patients.

ACE2-containing defensosomes serve as decoys to inhibit SARS-CoV-2 infection

Extracellular vesicles of endosomal origin, exosomes, mediate intercellular communication by transporting substrates with a variety of functions related to tissue homeostasis and disease. Their diagnostic and therapeutic potential has been recognized for diseases such as cancer in which signaling defects are prominent. However, it is unclear to what extent exosomes and their cargo inform the progression of infectious diseases. We recently defined a subset of exosomes termed defensosomes that are mobilized during bacterial infection in a manner dependent on autophagy proteins. Through incorporating protein receptors on their surface, defensosomes mediated host defense by binding and inhibiting pore-forming toxins secreted by bacterial pathogens. Given this capacity to serve as decoys that interfere with surface protein interactions, we investigated the role of defensosomes during infection by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the etiological agent of Coronavirus Disease 2019 (COVID-19). Consistent with a protective function, exosomes containing high levels of the viral receptor ACE2 in bronchoalveolar lavage fluid (BALF) from critically ill COVID-19 patients was associated with reduced intensive care unit (ICU) and hospitalization times. We found ACE2+ exosomes were induced by SARS-CoV-2 infection and activation of viral sensors in cell culture, which required the autophagy protein ATG16L1, defining these as defensosomes. We further demonstrate that ACE2+ defensosomes directly bind and block viral entry. These findings suggest that defensosomes may contribute to the antiviral response against SARS-CoV-2 and expand our knowledge on the regulation and effects of extracellular vesicles during infection.

Autophagy proteins mediate the production of extracellular vesicles termed defensosomes in response to innate immune ligands. This study reveals that ACE2-containing defensosomes bind and inhibit SARS-CoV-2 infection, and are associated with reduced length of hospital stay for patients with COVID-19.

Self-assembling short immunostimulatory duplex RNAs with broad-spectrum antiviral activity

The current coronavirus disease 2019 (COVID-19) pandemic highlights the need for broad-spectrum antiviral therapeutics. Here we describe a new class of self-assembling immunostimulatory short duplex RNAs that potently induce production of type I and type III interferon (IFN-I and IFN-III). These RNAs require a minimum of 20 base pairs, lack any sequence or structural characteristics of known immunostimulatory RNAs, and instead require a unique sequence motif (sense strand, 5'-C; antisense strand, 3'-GGG) that mediates end-to-end dimer self-assembly. The presence of terminal hydroxyl or monophosphate groups, blunt or overhanging ends, or terminal RNA or DNA bases did not affect their ability to induce IFN. Unlike previously described immunostimulatory small interfering RNAs (siRNAs), their activity is independent of Toll-like receptor (TLR) 7/8, but requires the RIG-I/IRF3 pathway that induces a more restricted antiviral response with a lower proinflammatory signature compared with immunostimulant poly(I:C). Immune stimulation mediated by these duplex RNAs results in broad-spectrum inhibition of infections by many respiratory viruses with pandemic potential, including severe acute respiratory syndrome coronavirus (SARS-CoV)-2, SARS-CoV, Middle East respiratory syndrome coronavirus (MERS-CoV), human coronavirus (HCoV)-NL63, and influenza A virus in cell lines, human lung chips that mimic organ-level lung pathophysiology, and a mouse SARS-CoV-2 infection model. These short double-stranded RNAs (dsRNAs) can be manufactured easily, and thus potentially could be harnessed to produce broad-spectrum antiviral therapeutics.

Comprehensive screening for drugs that modify radiation-induced immune responses

BACKGROUND

Combination therapy based on radiotherapy and immune checkpoint inhibitors (ICIs) was recently reported as effective for various cancers. The radiation-induced immune response (RIIR) is an essential feature in ICI-combined radiotherapy; however, the effects of drugs used concomitantly with RIIR remain unclear. We screened for drugs that can modify RIIR to understand the mutual relationship between radiotherapy and combined drugs in ICI-combined radiotherapy.

METHODS

We established a high-throughput system with reporter gene assays for evaluating RIIR, focusing on factors acting downstream of the STING-IRF pathway, which can stimulate cancer cells, T cells, and dendritic cells. We further quantified the effects of 2595 drugs, including those approved by the Food and Drug Administration, on RIIR in vitro.

RESULTS

The reporter assay results correlated well with the expression of immune response proteins such as programmed death-ligand 1. This high-throughput system enabled the identification of drugs including cytotoxic agents, molecular-targeted agents, and other agents that activate or suppress RIIR.

CONCLUSIONS

Our study provides an encyclopedic catalogue of clinically approved drugs based on their effect on RIIR. In ICIs combined radiotherapy, activation of STING-IFN may improve the therapeutic effect and our result could form a biological basis for further clinical trials combining radiotherapy with ICIs.

Functional Hallmarks of Healthy Macrophage Responses: Their Regulatory Basis and Disease Relevance

Macrophages are first responders for the immune system. In this role, they have both effector functions for neutralizing pathogens and sentinel functions for alerting other immune cells of diverse pathologic threats, thereby initiating and coordinating a multipronged immune response. Macrophages are distributed throughout the body-they circulate in the blood, line the mucosal membranes, reside within organs, and survey the connective tissue. Several reviews have summarized their diverse roles in different physiological scenarios and in the initiation or amplification of different pathologies. In this review, we propose that both the effector and the sentinel functions of healthy macrophages rely on three hallmark properties: response specificity, context dependence, and stimulus memory. When these hallmark properties are diminished, the macrophage's biological functions are impaired, which in turn results in increased risk for immune dysregulation, manifested by immune deficiency or autoimmunity. We review the evidence and the molecular mechanisms supporting these functional hallmarks.

ACE2-containing defensosomes serve as decoys to inhibit SARS-CoV-2 infection

Extracellular vesicles of endosomal origin, exosomes, mediate intercellular communication by transporting substrates with a variety of functions related to tissue homeostasis and disease. Their diagnostic and therapeutic potential has been recognized for diseases such as cancer in which signaling defects are prominent. However, it is unclear to what extent exosomes and their cargo inform the progression of infectious diseases. We recently defined a subset of exosomes termed defensosomes that are mobilized during bacterial infection in a manner dependent on autophagy proteins. Through incorporating protein receptors on their surface, defensosomes mediated host defense by binding and inhibiting pore-forming toxins secreted by bacterial pathogens. Given this capacity to serve as decoys that interfere with surface protein interactions, we investigated the role of defensosomes during infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiological agent of COVID-19. Consistent with a protective function, exosomes containing high levels of the viral receptor ACE2 in bronchioalveolar lavage fluid from critically ill COVID-19 patients was associated with reduced ICU and hospitalization times. We found ACE2+ exosomes were induced by SARS-CoV-2 infection and activation of viral sensors in cell culture, which required the autophagy protein ATG16L1, defining these as defensosomes. We further demonstrate that ACE2+ defensosomes directly bind and block viral entry. These findings suggest that defensosomes may contribute to the antiviral response against SARS-CoV-2 and expand our knowledge on the regulation and effects of extracellular vesicles during infection.

Interferon-Induced Transmembrane Proteins Inhibit Infection by the Kaposi's Sarcoma-Associated Herpesvirus and the Related Rhesus Monkey Rhadinovirus in a Cell-Specific Manner

The interferon-induced transmembrane proteins (IFITMs) are broad-spectrum antiviral proteins that inhibit the entry of enveloped viruses. We analyzed the effect of IFITMs on the gamma-2 herpesviruses Kaposi's sarcoma-associated herpesvirus (KSHV) and the closely related rhesus monkey rhadinovirus (RRV). We used CRISPR/Cas9-mediated gene knockout to generate A549 cells, human foreskin fibroblasts (HFF), and human umbilical vein endothelial cells (HUVEC) with combined IFITM1/2/3 knockout and identified IFITMs as cell-dependent inhibitors of KSHV and RRV infection in A549 cells and HFF but not HUVEC. IFITM overexpression revealed IFITM1 as the relevant IFITM that inhibits KSHV and RRV infection. Fluorescent KSHV particles did not pronouncedly colocalize with IFITM-positive compartments. However, we found that KSHV and RRV glycoprotein-mediated cell-cell fusion is enhanced upon IFITM1/2/3 knockout. Taken together, we identified IFITM1 as a cell-dependent restriction factor of KSHV and RRV that acts at the level of membrane fusion. Of note, our results indicate that recombinant IFITM overexpression may lead to results that are not representative for the situation at endogenous levels. Strikingly, we observed that the endotheliotropic KSHV circumvents IFITM-mediated restriction in HUVEC despite high IFITM expression, while influenza A virus (IAV) glycoprotein-driven entry into HUVEC is potently restricted by IFITMs even in the absence of interferon. Mechanistically, we found that KSHV colocalizes less with IFITM1 and IFITM2 in HUVEC than in A549 cells immediately after attachment, potentially contributing to the observed difference in restriction. IMPORTANCE IFITM proteins are the first line of defense against infection by many pathogens and may also have therapeutic importance, as they, among other effectors, mediate the antiviral effect of interferons. Neither their function against herpesviruses nor their mechanism of action is well understood. We report here that in some cells but not in, for example, primary umbilical vein endothelial cells, IFITM1 restricts KSHV and RRV and that, mechanistically, this is likely effected by reducing the fusogenicity of the cell membrane. Further, we demonstrate potent inhibition of IAV glycoprotein-driven infection of cells of extrapulmonary origin by high constitutive IFITM expression.

Self-assembling short immunostimulatory duplex RNAs with broad spectrum antiviral activity

The current COVID-19 pandemic highlights the need for broad-spectrum antiviral therapeutics. Here we describe a new class of self-assembling immunostimulatory short duplex RNAs that potently induce production of type I and type III interferon (IFN-I and IFN-III), in a wide range of human cell types. These RNAs require a minimum of 20 base pairs, lack any sequence or structural characteristics of known immunostimulatory RNAs, and instead require a unique conserved sequence motif (sense strand: 5'-C, antisense strand: 3'-GGG) that mediates end-to-end dimer self-assembly of these RNAs by Hoogsteen G-G base-pairing. The presence of terminal hydroxyl or monophosphate groups, blunt or overhanging ends, or terminal RNA or DNA bases did not affect their ability to induce IFN. Unlike previously described immunostimulatory siRNAs, their activity is independent of TLR7/8, but requires the RIG-I/IRF3 pathway that induces a more restricted antiviral response with a lower proinflammatory signature compared with poly(I:C). Immune stimulation mediated by these duplex RNAs results in broad spectrum inhibition of infections by many respiratory viruses with pandemic potential, including SARS-CoV-2, SARS-CoV, MERS-CoV, and influenza A, as well as the common cold virus HCoV-NL63 in both cell lines and human Lung Chips that mimic organ-level lung pathophysiology. These short dsRNAs can be manufactured easily, and thus potentially could be harnessed to produce broad-spectrum antiviral therapeutics at low cost.

Aedes aegypti Toll pathway is induced through dsRNA sensing in endosomes

Mosquito anti-pathogen immune responses, including those controlling infection with arboviruses are regulated by multiple signal transduction pathways. While the Toll pathway is critical in the defense against arboviruses such as dengue and Zika viruses, the factors and mechanisms involved in virus recognition leading to the activation of the Toll pathway are not fully understood. In this study we evaluated the role of virus-produced double-stranded RNA (dsRNA) intermediates in mosquito immune activation by utilizing the synthetic dsRNA analog polyinosinic-polycytidylic acid (poly I:C). Poly I:C treatment of Aedes aegypti mosquitoes and Aag2 cells reduced DENV infection. Transcriptomic analyses of Aag2 cell responses to poly I:C indicated putative activation of the Toll pathway. We found that poly I:C is translocated to the endosomal compartment of Aag2 cells, and that the A. aegypti Toll 6 receptor is a putative dsRNA recognition receptor. This study elucidates the role of dsRNAs in the immune activation of non-RNAi pathways in mosquitoes.

PolyI:C suppresses TGF-β1-induced Akt phosphorylation and reduces the motility of A549 lung carcinoma cells

BACKGROUNDS

Epithelial mesenchymal transition (EMT) is a critical process involved in the invasion and metastasis of cancer, including lung cancer (LC). Transforming growth factor (TGF)-β is one of factors capable of inducing EMT. Polyinosinic-polycytidylic acid (polyI:C), a synthetic agonist for toll-like receptor (TLR) 3, can enhance immune responses and has been used as an adjuvant for cancer vaccines; however, it remains unclear whether it influences other process, such as EMT. In the present study, we examined the effects of polyI:C on TGF-β-treated A549 human LC cells.

METHODS AND RESULTS

By in vitro cell proliferation assay, polyI:C showed no effect on the growth of A549 cells treated with TGF-β1 at the concentration range up to 10 μg/ml; however, it markedly suppressed the motility in a cell scratch and a cell invasion assay. By Western blotting, polyI:C dramatically decreased TGF-β1-induced Ak strain transforming (Akt) phosphorylation and increased phosphatase and tensin homologue (PTEN) expression without affecting the Son of mothers against decapentaplegic (Smad) 3 phosphorylation or the expression level of E-cadherin, N-cadherin or Snail, indicating that polyI:C suppressed cell motility independently of the 'cadherin switching'. The Akt inhibitor perifosine inhibited TGF-β1-induced cell invasion, and the PTEN-specific inhibitor VO-OHpic appeared to reverse the inhibitory effect of polyI:C.

CONCLUSION

PolyI:C has a novel function to suppress the motility of LC cells undergoing EMT by targeting the phosphatidylinositol 3-kinase/Akt pathway partly via PTEN and may prevent or reduce the metastasis of LC cells.

Inflammation and Cell Death of the Innate and Adaptive Immune System during Sepsis

Sepsis is a life-threatening medical condition that occurs when the host has an uncontrolled or abnormal immune response to overwhelming infection. It is now widely accepted that sepsis occurs in two concurrent phases, which consist of an initial immune activation phase followed by a chronic immunosuppressive phase, leading to immune cell death. Depending on the severity of the disease and the pathogen involved, the hosts immune system may not fully recover, leading to ongoing complications proceeding the initial infection. As such, sepsis remains one of the leading causes of morbidity and mortality world-wide, with treatment options limited to general treatment in intensive care units (ICU). Lack of specific treatments available for sepsis is mostly due to our limited knowledge of the immuno-physiology associated with the disease. This review will provide a comprehensive overview of the mechanisms and cell types involved in eliciting infection-induced immune activation from both the innate and adaptive immune system during sepsis. In addition, the mechanisms leading to immune cell death following hyperactivation of immune cells will be explored. The evaluation and better understanding of the cellular and systemic responses leading to disease onset could eventuate into the development of much needed therapies to combat this unrelenting disease.

TLR3 agonists: RGC100, ARNAX, and poly-IC: a comparative review

Toll-like receptors 3 (TLR3) have been broadly studied among all TLRs over the last few decades together with its agonists due to their contribution to cancer regression. These agonists undeniably have some shared characteristics such as mimicking dsRNA but pathways through which they exhibit antitumor properties are relatively diverse. In this review, three widely studied agonists RGC100, ARNAX, and poly-IC are discussed along with their structural and physiochemical differences including the signaling cascades through which they exert their actions. Comparison has been made to identify the finest agonist with maximum effectivity and the least side effect profile.

TLR3 activation by Zika virus stimulates inflammatory cytokine production which dampens the antiviral response induced by RIG-I-like receptors

Infection with the Zika virus (ZIKV), a member of the Flaviviridae family, can cause serious neurological disorders, most notably microcephaly in newborns. Here we investigated the innate immune response to ZIKV infection in cells of the nervous system. In human neural progenitor cells (hNPCs), a target for ZIKV infection and likely involved in ZIKV-associated neuropathology, viral infection failed to elicit an antiviral interferon (IFN) response. However, pharmacological inhibition of TLR3 partially restored this deficit. Analogous results were obtained in human iPSC-derived astrocytes, which are capable of mounting a strong antiviral cytokine response. There, ZIKV is sensed by both RIG-I and MDA5 and induces an IFN response as well as expression of pro-inflammatory cytokines such as interleukin-6 (IL-6). Upon inhibition of TLR3, also in astrocytes the antiviral cytokine response was enhanced, whereas amounts of pro-inflammatory cytokines were reduced. To study the underlying mechanism, we used human epithelial cells as an easy to manipulate model system. We found that ZIKV is sensed in these cells by RIG-I to induce a robust IFN response and by TLR3 to trigger the expression of pro-inflammatory cytokines, including IL-6. ZIKV induced upregulation of IL-6 activated the STAT3 pathway, which decreased STAT1 phosphorylation in a SOCS-3 dependent manner, thus reducing the IFN response. In conclusion, we show that TLR3 activation by ZIKV suppresses IFN responses triggered by RIG-I-like receptors.ImportanceZika virus (ZIKV) has a pronounced neurotropism and infections with this virus can cause serious neurological disorders, most notably microcephaly and the Guillain-Barré syndrome. Our studies reveal that during ZIKV infection, recognition of viral RNA by TLR3 enhances the production of inflammatory cytokines and suppresses the interferon response triggered by RIG-I-like receptors (RLR) in a SOCS3-dependent manner, thus facilitating virus replication. The discovery of this crosstalk between antiviral (RLR) and inflammatory (TLR) responses may have important implications for our understanding of ZIKV-induced pathogenesis.

Coronavirus disease-19: The multi-level, multi-faceted vasculopathy

BACKGROUND AND AIMS

The new coronavirus disease (COVID-19) is a systemic disease. Mounting evidence depict signs and symptoms involving multiple organs, most of which supported by pathological data. A plausible link to these manifestations is vascular and endothelial dysfunction/damage. However, much of the current knowledge relies on opinion and incipient evidence. We aim to objectively appraise current evidence on the association between COVID-19 and vascular disease, specifically endotheliitis and vasculitis.

METHODS

Two researchers independently entered the search terms COVID-19 OR SARS-CoV-2 AND vasculitis, endotheliitis OR endothelium in the following online platforms: MedRxiv and LitCovid (PubMed). The search period was set from November 1, 2019 to August 28, 2020. Manuscripts with unavailable full texts, not in English, mainly on pre-clinical data, presenting only study designs or not directly related to the topics of this review were excluded. Retrospective and prospective studies, especially longitudinal ones, were given priority to the purpose of this review. Since there was paucity of prospective controlled evidence, case reports/series were also considered.

RESULTS

A total of 318 manuscripts were initially found. Sixty-seven (21%) were excluded: 59 (18.5%) met exclusion criteria and 8 (2.5%) were duplicates. One hundred and forty-two manuscripts (44,6%) did not provide original data and were also excluded: 35 (11%) were comments, 108 (33.9%) reviews; 1 (0.3%) position paper. One hundred and seven (33.6%) studies were considered for the present scoping review: 81 (25,5%) case reports/series; 18 (5.7%) prospective; 8 (2.5%) retrospective. Viral inclusions in endothelial cells, mononuclear cell infiltrates in the intima of small vessels and markers of endothelial cell apoptosis were demonstrated. Specificities of COVID-19 may lead to diverse vascular manifestations in different levels of the vascular bed.

CONCLUSIONS

Evidence indicates that COVID-19 targets vasculature and endothelium. However, high quality data is still lacking and studies with prospective designs and appropriately matched controls are needed.

Angiotensin-converting enzyme 2 (ACE2): COVID 19 gate way to multiple organ failure syndromes

BACKGROUND

Globally, the current medical emergency for novel coronavirus 2019 (COVID-19) leads to respiratory distress syndrome and death.

PURPOSE

This review highlighted the effect of COVID-19 on systemic multiple organ failure syndromes. This review is intended to fill a gap in information about human physiological response to COVID-19 infections. This review may shed some light on other potential mechanisms and approaches in COVID -19 infections towards systemic multiorgan failure syndromes.

FINDING

SARS-CoV-2 intervened mainly in the lung with progression to pneumonia and acute respiratory distress syndrome (ARDS) via the angiotensin-converting enzyme 2(ACE2) receptor. Depending on the viral load, infection spread through the ACE2 receptor further to various organs such as heart, liver, kidney, brain, endothelium, GIT, immune cell, and RBC (thromboembolism). This may be aggravated by cytokine storm with the extensive release of proinflammatory cytokines from the deregulating immune system.

CONCLUSION

The widespread and vicious combinations of cytokines with organ crosstalk contribute to systemic hyper inflammation and ultimately lead to multiple organ dysfunction (Fig. 1). This comprehensive study comprises various manifestations of different organs in COVID-19 and may assist the clinicians and scientists pertaining to a broad approach to fight COVID 19.

Endothelial activation and dysfunction in COVID-19: from basic mechanisms to potential therapeutic approaches

On 12 March 2020, the outbreak of coronavirus disease 2019 (COVID-19) was declared a pandemic by the World Health Organization. As of 4 August 2020, more than 18 million confirmed infections had been reported globally. Most patients have mild symptoms, but some patients develop respiratory failure which is the leading cause of death among COVID-19 patients. Endothelial cells with high levels of angiotensin-converting enzyme 2 expression are major participants and regulators of inflammatory reactions and coagulation. Accumulating evidence suggests that endothelial activation and dysfunction participate in COVID-19 pathogenesis by altering the integrity of vessel barrier, promoting pro-coagulative state, inducing endothelial inflammation, and even mediating leukocyte infiltration. This review describes the proposed cellular and molecular mechanisms of endothelial activation and dysfunction during COVID-19 emphasizing the principal mediators and therapeutic implications.

Tryptanthrin suppresses double-stranded RNA-induced CXCL10 expression via inhibiting the phosphorylation of STAT1 in human umbilical vein endothelial cells

Tryptanthrin is a bioactive component of indigo plants such as Polygonum tinctrorium and known to have an anti-inflammatory activity. The aim of this study was to investigate the effects of tryptanthrin on Toll-like receptor 3 (TLR3)-mediated cytokine and chemokine expression in human umbilical vein endothelial cells (HUVEC). Herein, we found that tryptanthrin suppressed the expression of CXCL10 in HUVEC upon stimulation with a TLR3 ligand polyinosinic-polycytidylic acid (poly IC). Tryptanthrin did not inhibit poly IC-induced activation of interferon regulatory factor 3 (IRF3) or the mRNA expression of interferon (IFN)-β, while it significantly suppressed the expression of RIG-I, MDA5, and classical IFN-stimulated genes (ISGs). Tryptanthrin attenuated the phosphorylation and nuclear translocation of STAT1 in HUVEC stimulated with not only poly IC but also recombinant IFN-β. These results suggested that tryptanthrin inhibited poly IC-induced expression of CXCL10 and ISGs via suppressing the activation of STAT1 in HUVEC. Our findings indicate that tryptanthrin may be useful for regulating TLR3-mediated vascular inflammation.

HIV infection suppresses TLR3 activation-mediated antiviral immunity in microglia and macrophages

Monocytic-lineage cells in the central nervous system (CNS), including microglia and brain resident macrophages, are the key players in the CNS innate immunity against viral infections, including human immunodeficiency virus (HIV). However, these cells also serve as the major targets and reservoirs for HIV in the CNS. To address the question of how HIV can establish persistent infection in the target cells in the CNS, we examined whether HIV has the ability to counteract Toll-like receptor 3 (TLR3) activation-mediated antiviral immunity in microglia and macrophages. We observed that HIV latently infected microglial cells (HC69·5) expressed reduced levels of TLR3 and TLR3 activation-mediated interferons (IFN-α/β and IFN-λ) as compared with the uninfected control cells (C20). In addition, HIV infection of primary human macrophages suppressed the expression of TLR3 and the IFNs. HIV infection also inhibited the expression of the antiviral IFN-stimulated genes (ISGs) and the HIV-restriction miRNAs. Mechanistically, HIV infection inhibited the phosphorylation of IFN regulatory factors (IRF3 and IRF7) and signal transducer and activator of transcription proteins (STAT1 and STAT3) in both HIV latently infected microglia and acutely infected macrophages. These findings provide previously unrecognized and sound mechanisms for HIV infection and persistence in the primary target and reservoir cells in the brain.

Vascular Endothelial Cells and Innate Immunity

In addition to the roles of endothelial cells (ECs) in physiological processes, ECs actively participate in both innate and adaptive immune responses. We previously reported that, in comparison to macrophages, a prototypic innate immune cell type, ECs have many innate immune functions that macrophages carry out, including cytokine secretion, phagocytic function, antigen presentation, pathogen-associated molecular patterns-, and danger-associated molecular patterns-sensing, proinflammatory, immune-enhancing, anti-inflammatory, immunosuppression, migration, heterogeneity, and plasticity. In this highlight, we introduce recent advances published in both ATVB and many other journals: (1) several significant characters classify ECs as novel immune cells not only in infections and allograft transplantation but also in metabolic diseases; (2) several new receptor systems including conditional danger-associated molecular pattern receptors, nonpattern receptors, and homeostasis associated molecular patterns receptors contribute to innate immune functions of ECs; (3) immunometabolism and innate immune memory determine the innate immune functions of ECs; (4) a great induction of the immune checkpoint receptors in ECs during inflammations suggests the immune tolerogenic functions of ECs; and (5) association of immune checkpoint inhibitors with cardiovascular adverse events and cardio-oncology indicates the potential contributions of ECs as innate immune cells.

Imiquimod suppresses respiratory syncytial virus (RSV) replication via PKA pathway and reduces RSV induced-inflammation and viral load in mice lungs

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract disease and bronchiolitis in children, as well as an important cause of morbidity and mortality in elderly and immunocompromised individuals. However, there is no safe and efficacious RSV vaccine or antiviral treatment. Toll Like Receptors (TLR) are important molecular mediators linking innate and adaptive immunity, and their stimulation by cognate agonists has been explored as antiviral agents. Imiquimod is known as a TLR7 agonist, but additionally acts as an antagonist for adenosine receptors. In this study, we demonstrate that imiquimod, but not resiquimod, has direct anti-RSV activity via PKA pathway in HEp-2 and A549 cells, independently of an innate response. Imiquimod restricts RSV infection after viral entry into the host cell, interfering with viral RNA and protein synthesis. Probably as a consequence of these anti-RSV properties, imiquimod displays cytokine modulating activity in RSV infected epithelial cells. Moreover, in a murine model of RSV infection, imiquimod treatment improves the course of acute disease, evidenced by decreased weight loss, reduced RSV lung titers, and attenuated airway inflammation. Consequently, imiquimod represents a promising therapeutic alternative against RSV infection and may inform the development of novel therapeutic targets to control RSV pathogenesis.

•

Imiquimod has direct anti-RSV activity via PKA pathway, independently of an innate response.

•

Imiquimod restricts RSV infection after viral entry into the host cell, interfering with viral RNA and protein synthesis.

•

Imiquimod reduces cytokine production in RSV infected epithelial cells, probably as a result of its anti-RSV properties.

•

Imiquimod reduces RSV lung titers and decreases weight loss and airway inflammation in a murine model of RSV infection.

Next-Generation Sequencing Analysis of Cellular Response to Influenza B Virus Infection

Influenza B virus (IBV) is a respiratory pathogen that infects humans and causes seasonal influenza epidemics. However, cellular response to IBV infection in humans and mechanisms of host-mediated restriction of IBV replication are not thoroughly understood. In this study, we used next-generation sequencing (NGS) to perform transcriptome profiling of IBV-infected human lung epithelial A549 cells at 0, 6, 12, and 24 h post infection (hpi) and characterized the cellular gene expression dynamics. We observed that more than 4000 host genes were differentially regulated during the study period, which included up regulation of genes encoding proteins, having a role in the innate antiviral immune responses, immune activation, cellular metabolism, autophagy, and apoptosis, as well as down regulation of genes involved in mitosis and cell proliferation. Further analysis of RNA-Seq data coupled with RT-qPCR validation collectively showed that double-strand RNA recognition pathways, including retinoic acid-inducible gene I (RIG-I) and Toll-like receptor 3 (TLR3), were substantially activated following IBV infection. Taken together, these results provide important initial insights into the intimate interaction between IBV and lung epithelial cells, which can be further explored towards elucidation of the cellular mechanisms in restriction or elimination of IBV infections in humans.

Immune Consequences of Endothelial Cells' Activation and Dysfunction During Sepsis

The vascular endothelium provides a direct interface between circulating blood cells and parenchymal cells. Thus, it has a key role in vasomotor tone regulation, primary hemostasis, vascular barrier, and immunity. In the case of systemic inflammation, endothelial cell (EC) activation initiates a powerful innate immune response to eliminate the pathogen. In some specific conditions, ECs may also contribute to the activation of adaptive immunity and the recruitment of antigen-specific lymphocytes. However, the loss of EC functions or an exaggerated activation of ECs during sepsis can lead to multiorgan failure.

Genetic Polymorphisms within Interferon-λ Region and Interferon-λ3 in the Human Pathophysiology: Their Contribution to Outcome, Treatment, and Prevention of Infections with Hepatotropic Viruses

:

Genetic polymorphisms within the interferon λ (IFN-λ) chromosomal region, mainly rs12979860 of IFN-λ4 gene (IFNL4), are known as associated with spontaneous hepatitis C virus (HCV) resolution and sustained viral response to therapy with pegylated interferon- α and ribavirin. Strong linkage disequilibrium of IFNL4 rs12979860 with IFNL4 rs368234815, which is casually associated with HCV spontaneous and therapeutical eradication, at least partially explains favorable HCV outcomes attributed to major homozygosity in rs12979860. Effects of IFN-based antiviral treatment are associated with pretreatment expression of the IFN-λ1 receptor, expression of hepatic IFN-stimulated genes, production of IFN- λ4, and preactivation of the JAK-STAT signaling. Nowadays direct-acting antivirals (DAAs) became a potent tool in the treatment of hepatitis C, but IFN-λs are still under investigation as potential antivirals and might be an option in HCV infection (DAA resistance, recurrent viremia, adverse effects).

:

Patients with altered immunocompetence are especially prone to infections. In uremic subjects, polymorphisms within the IFN-λ chromosomal region associate with spontaneous HCV clearance, similarly like in the non-uremic population. Circulating IFN-λ3 shows a positive correlation with plasma titers of antibodies to surface antigen of hepatitis B virus (anti-HBs), which are crucial for protection against hepatitis B virus. More efficient anti-HBs production in the presence of higher IFN-λ3 levels might occur due to IFN-λ3-induced regulation of indoleamine 2,3-dioxygenase (IDO) expression. IFN-stimulated response element is a part of IDO gene promoter. It is worth further investigation whether IDO gene, circulating IDO, genetic polymorphisms within the IFN-λ region, and circulating IFN-λ3 act in concordance in immunological response to hepatotropic viruses.

Prokaryotic RNA activates endothelial cells promoting neutrophil transmigration

Endothelial cell (EC)-neutrophil (PMN) interactions are crucial in the resolution of bacterial infections. Prokaryotic RNA (pRNA) has been reported as a pathogen-associated molecular pattern that is released from bacteria upon death and is able to activate PMN. In this work, we studied the effects of pRNA on EC and investigated whether these effects could modulate EC-PMN interaction. For this purpose, we purified total pRNA from Escherichia coli and used it as a stimulus for Human Umbilical Vein Endothelial Cells (HUVEC). We found that the incubation of pRNA with HUVEC caused the increase of surface intercellular adhesion molecule 1 (ICAM-1 or CD54) expression on HUVEC, and the secretion of IL-8 and von Willebrand factor, characteristics consistent with HUVEC activation, without causing toxic effects. Moreover, pRNA-treated HUVEC also induced PMN adhesion and the conditioned medium obtained from treated-HUVEC was chemotactic for PMN and caused their activation, as determined by CD11b upregulation. As reported previously, the degradation products of pRNA induced similar biological effects. The treatment of HUVEC with endocytosis inhibitors revealed that the entry of pRNA partially relied on a clathrin-dependent mechanism, whereas the effects of degradation products could not be inhibited by any of the inhibitors tested. Using a transwell system, we found that pRNA or degraded pRNA were also able to stimulate HUVEC when recognized from the basolateral side. Our results indicate that pRNA activates EC, resulting in the modulation of EC-PMN interaction by inducing PMN chemotaxis, adhesion and activation. In the context of infection, pRNA sensed by EC and PMN could favor bacterial clearance.

Bloom syndrome protein restrains innate immune sensing of micronuclei by cGAS

Cellular innate immune sensors of DNA are essential for host defense against invading pathogens. However, the presence of self-DNA inside cells poses a risk of triggering unchecked immune responses. The mechanisms limiting induction of inflammation by self-DNA are poorly understood. BLM RecQ-like helicase is essential for genome integrity and is deficient in Bloom syndrome (BS), a rare genetic disease characterized by genome instability, accumulation of micronuclei, susceptibility to cancer, and immunodeficiency. Here, we show that BLM-deficient fibroblasts show constitutive up-regulation of inflammatory interferon-stimulated gene (ISG) expression, which is mediated by the cGAS-STING-IRF3 cytosolic DNA-sensing pathway. Increased DNA damage or down-regulation of the cytoplasmic exonuclease TREX1 enhances ISG expression in BLM-deficient fibroblasts. cGAS-containing cytoplasmic micronuclei are increased in BS cells. Finally, BS patients demonstrate elevated ISG expression in peripheral blood. These results reveal that BLM limits ISG induction, thus connecting DNA damage to cellular innate immune response, which may contribute to human pathogenesis.

Interferon regulatory factor 3 plays a role in macrophage responses to interferon-γ

IFN-γ produced during viral infections activates the IFN-γ receptor (IFNGR) complex for STAT1 transcriptional activity leading to expression of Interferon Regulatory Factors (IRF). Simultaneous activation of TBK/IKKε via TLR3 during viral infections activates the transcription factor IRF3. Together these transcription factors contributes to expression of intracellular proteins (e.g. ISG49, ISG54) and secreted proteins (e.g. IFN-β, IP-10, IL-15) that are essential to innate antiviral immunity. Here we examined the role of IRF3 in expression of innate anti-viral proteins produced in response to IFN-γ plus TLR3 agonist. Wild-type (WT) and IRF3KO RAW264.7 cells, each with ISG54-promoter-luciferase reporter vectors, were stimulated with IFN-γ, poly I:C, or both together. ISG54 promoter activity was significantly reduced in IRF3KO RAW264.7 cells responding to IFN-γ, poly I:C, or IFN-γ plus poly I:C, compared with WT RAW264.7 cells. These data were confirmed with western blot and qRT-PCR. Primary macrophages and dendritic cells (DCs) from IRF3KO mice also showed decreased ISG54 in response to IFN-γ, poly I:C, or IFN-γ plus poly I:C compared with those from WT mice. Moreover, pharmacological inhibition of TBK/IKKε significantly reduced ISG54 promoter activity in response to IFN-γ, poly I:C, or IFN-γ plus poly I:C. Similarly, expression of ISG49 and IL-15, but not IP-10, was impaired in IRF3KO RAW264.7 cells responding to IFN-γ or poly I:C, which also had impaired STAT1 phosphorylation and IRF1 expression. These data show that IRF3 contributes to IFN-γ/IFNGR signaling for expression of innate anti-viral proteins in macrophages.

Chicken endothelial cells are highly responsive to viral innate immune stimuli and are susceptible to infections with various avian pathogens

It is well established that the endothelium plays a prominent role in the pathogenesis of various infectious diseases in mammals. However, little is known about the role of endothelial cells (EC) as targets for avian pathogens and their contribution to the pathogenesis of infectious diseases in galliform birds. First, we explored the innate immune response of primary chicken aortic endothelial cells (pchAEC), obtained from 18-day-old embryos, to stimulation with pathogen-associated molecular patterns or recombinant chicken interferons (type I, II and III IFNs). In spite of the abundant expression of a number of innate immune receptors, marked cytokine responses to stimulation with pathogen-associated molecular patterns were only seen in pchAEC treated with the TLR3 agonist polyI:C (pI:C) and the MDA5 agonist liposome-complexed polyI:C (L-pI:C), as was assessed by quantitative PCR and luciferase-based IFN-I/NFκB reporter assays. Treatments of pchAEC with IFN-α, IFN-γ and IFN-λ resulted in STAT1-phosphorylation/activation, as was revealed by immunoblotting. Next, we demonstrated that pchAEC are susceptible to infection with a variety of poultry pathogens, including Marek's disease virus (MDV), infectious bursal disease virus (IBDV), avian pathogenic Escherichia coli (APEC) and Eimeria tenella. Our data highlight that chicken EC are potential targets for viral, bacterial and protozoan pathogens in gallinaceous poultry and may partake in the inflammatory and antimicrobial response. The pchAEC infection model used herein will allow further studies interrogating avian pathogen interactions with vascular EC. RESEARCH HIGHLIGHTS Use of a well-defined primary chicken aortic endothelial cell (pchAEC) culture model for studying avian host-pathogen interactions. pchAEC are responsive to innate immune stimulation with viral pathogen-associated molecular patterns and chicken type I, II and III interferons. pchAEC are susceptible to infections with economically important poultry pathogens, including MDV, IBDV, APEC and Eimeria tenella.

Helicase-Driven Activation of NFκB-COX2 Pathway Mediates the Immunosuppressive Component of dsRNA-Driven Inflammation in the Human Tumor Microenvironment

Presence of cytotoxic CD8⁺ T cells (CTL) in tumor microenvironments (TME) is critical for the effectiveness of immune therapies and patients' outcome, whereas regulatory T(reg) cells promote cancer progression. Immune adjuvants, including double-stranded (ds)RNAs, which signal via Toll-like receptor-3 (TLR3) and helicase (RIG-I/MDA5) pathways, all induce intratumoral production of CTL-attractants, but also Treg attractants and suppressive factors, raising the question of whether induction of these opposing groups of immune mediators can be separated. Here, we use human tumor explant cultures and cell culture models to show that the (ds) RNA Sendai Virus (SeV), poly-I:C, and rintatolimod (poly-I:C₁₂U) all activate the TLR3 pathway involving TRAF3 and IRF3, and induce IFNα, ISG-60, and CXCL10 to promote CTL chemotaxis to ex vivo-treated tumors. However, in contrast with SeV and poly I:C, rintatolimod did not activate the MAVS/helicase pathway, thus avoiding NFκB- and TNFα-dependent induction of COX2, COX2/PGE2-dependent induction of IDO, IL10, CCL22, and CXCL12, and eliminating Treg attraction. Induction of CTL-attractants by either poly I:C or rintatolimod was further enhanced by exogenous IFNα (enhancer of TLR3 expression), whereas COX2 inhibition enhanced the response to poly-I:C only. Our data identify the helicase/NFκB/TNFα/COX2 axis as the key suppressive pathway of dsRNA signaling in human TME and suggest that selective targeting of TLR3 or elimination of NFκB/TNFα/COX2-driven suppression may allow for selective enhancement of type-1 immunity.Significance: This study characterizes two different poly-I:C-induced signaling pathways in their induction of immunostimulatory and suppressive factors and suggests improved ways to reprogram the TME to enhance the antitumor efficacy of immunotherapies. Cancer Res; 78(15); 4292-302. ©2018 AACR.

Reduction of Marek's Disease Virus Infection by Toll-Like Receptor Ligands in Chicken Embryo Fibroblast Cells

Evolutionarily conserved pattern recognition receptors, including Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns (PAMPs) that are present in microbes. PAMPs induce several pathways downstream of TLRs that lead to induction of antiviral responses. The objective of this study was to investigate the stimulatory effect of various PAMPs (in the form of TLR ligands) in reducing Marek's disease virus (MDV) infection in chicken embryo fibroblast cells (CEFs). To this end, CEFs were pretreated with Pam3CSK4, Poly(IC), lipopolysaccharide (LPS), and CpG ODN as TLR2, TLR3, TLR4, and TLR21 ligands, respectively for 24 h followed by infection with MDV. The results indicated that pretreatment with Poly(IC) resulted in a robust reduction (by about 81%) of MDV infection in CEFs at 96 h postinfection while a moderate reduction was observed with treatment of Pam3CSK4 (35%), LPS (26%), and CpG ODN (23%) PAMPs. Transcriptional analysis of gene expression in CEFs demonstrated that all TLR ligand treatments and MDV infection significantly increased the expression of type I interferons, interleukin (IL)-1β, interferon regulatory factor 7 (IRF7), interferon induced protein with tetratricopeptide repeats 5 (IFIT5), and myxoma-resistance protein (Mx). Further studies are needed to explore the mechanism by which PAMPs, particularly the TLR3 ligands could reduce MDV infection in CEFs, which may play an important role in controlling the replication of MDV in chicken.

Human Intestinal Epithelial Cells Release Antiviral Factors That Inhibit HIV Infection of Macrophages

As a rich source of CD4⁺ T cells and macrophages, the gastrointestinal (GI) tract is a major target site for HIV infection. The interplay between GI-resident macrophages and intestinal epithelial cells (IECs) constitutes an important element of GI innate immunity against pathogens. In this study, we investigated whether human IECs have the ability to produce antiviral factors that can inhibit HIV infection of macrophages. We demonstrated that IECs possess functional toll-like receptor 3 (TLR3), the activation of which resulted in induction of key interferon (IFN) regulatory factors (IRF3 and IRF7), IFN-β, IFN-λ, and CC chemokines (MIP-1α, MIP-1β, RANTES), the ligands of HIV entry co-receptor CCR5. In addition, TLR3-activated IECs release exosomes that contained the anti-HIV factors, including IFN-stimulated genes (ISGs: ISG15, ISG56, MxB, OAS-1, GBP5, and Viperin) and HIV restriction miRNAs (miRNA-17, miRNA-20, miRNA-28, miRNA-29 family members, and miRNA-125b). Importantly, treatment of macrophages with supernatant (SN) from the activated IEC cultures inhibited HIV replication. Further studies showed that IEC SN could also induce the expression of antiviral ISGs and cellular HIV restriction factors (Tetherin and APOBEC3G/3F) in HIV-infected macrophages. These findings indicated that IECs might act as an important element in GI innate immunity against HIV infection/replication.

Exploiting poly(I:C) to induce cancer cell apoptosis

TLR3 belong to the Toll-like receptors family, it is mainly expressed on immune cells where it senses pathogen-associated molecular patterns and initiates innate immune response. TLR3 agonist poly(I:C) was developed to mimic pathogens infection and boost immune system activation to promote anti-cancer therapy. Accordingly, TLR agonists were included in the National Cancer Institute list of immunotherapeutic agents with the highest potential to cure cancer. Besides well known effects on immune cells, poly(I:C) was also shown, in experimental models, to directly induce apoptosis in cancer cells expressing TLR3.

This review presents the current knowledge on the mechanism of poly(I:C)-induced apoptosis in cancer cells. Experimental evidences on positive or negative regulators of TLR3-mediated apoptosis induced by poly(I:C) are reported and strategies are proposed to successfully promote this event in cancer cells.

Cancer cells apoptosis is an additional arm offered by poly(I:C), besides activation of immune system, for the treatment of various type of cancer. A further dissection of TLR3 signaling would contribute to greater resolution of the critical steps that impede full exploitation of the poly(I:C)-induced apoptosis. Experimental evidences about negative regulator of poly(I:C)-induced apoptotic program should be considered in combinations with TLR3 agonists in clinical trials.

Endothelial cells: source, barrier, and target of defensive mediators

Endothelium is strategically located at the interface between blood and interstitial tissues, placing thus endothelial cell as a key player in vascular homeostasis. Endothelial cells are in a dynamic equilibrium with their environment and constitute concomitantly a source, a barrier, and a target of defensive mediators. This review will discuss the recent advances in our understanding of the complex crosstalk between the endothelium, the complement system and the hemostasis in health and in disease. The first part will provide a general introduction on endothelial cells heterogeneity and on the physiologic role of the complement and hemostatic systems. The second part will analyze the interplay between complement, hemostasis and endothelial cells in physiological conditions and their alterations in diseases. Particular focus will be made on the prototypes of thrombotic microangiopathic disorders, resulting from complement or hemostasis dysregulation-mediated endothelial damage: atypical hemolytic uremic syndrome and thrombotic thrombocytopenic purpura. Novel aspects of the pathophysiology of the thrombotic microangiopathies will be discussed.

The increased concentration of macrophage migration inhibitory factor in serum and cerebrospinal fluid of patients with tick-borne encephalitis

Background

Host factors determining the clinical presentation of tick-borne encephalitis (TBE) are not fully elucidated. The peripheral inflammatory response to TBE virus is hypothesized to facilitate its entry into central nervous system by disrupting the blood-brain barrier with the involvement of a signaling route including Toll-like receptor 3 (TLR3) and pro-inflammatory cytokines macrophage migration inhibitory factor (MIF), tumor necrosis factor-α (TNFα), and interleukin-1 beta (IL-1β).

Methods

Concentrations of MIF, TNFα, and IL-1β were measured with commercial ELISA in serum and cerebrospinal fluid (CSF) from 36 hospitalized TBE patients, 7 patients with non-TBE meningitis, and 6 controls. The CSF albumin quotient (AQ) was used as a marker of blood-brain barrier permeability. Single nucleotide polymorphisms rs3775291, rs5743305 (associated with TLR3 expression), and rs755622 (associated with MIF expression) were assessed in blood samples from 108 TBE patients and 72 non-TBE controls. The data were analyzed with non-parametric tests, and p < 0.05 was considered significant.

Results

The median serum and CSF concentrations of MIF and IL-1β were significantly increased in TBE group compared to controls. MIF concentration in serum tended to correlate with AQ in TBE, but not in non-TBE meningitis. The serum concentration of TNFα was increased in TBE patients bearing a high-expression TLR3 rs5743305 TT genotype, which also associated with the increased risk of TBE. The low-expression rs3775291 TLR3 genotype TT associated with a prolonged increase of CSF protein concentration. The high-expression MIF rs755622 genotype CC tended to correlate with an increased risk of TBE, and within TBE group, it was associated with a mild presentation.

Conclusions

The results point to the signaling route involving TLR3, MIF, and TNFα being active in TBE virus infection and contributing to the risk of an overt neuroinvasive disease. The same factors may play a protective role intrathecally contributing to the milder course of neuroinfection. This suggests that the individual variability of the risk and clinical presentation of TBE might be traced to the variable peripheral and intrathecal expression of the mediators of the inflammatory response, which in turn associates with the host genetic background.

Dysregulation of signaling pathways associated with innate antibacterial immunity in patients with pancreatic cancer

Disorders of innate antibacterial response are of fundamental importance in the development of gastrointestinal cancers, including pancreatic cancer. Multi-regulatory properties of the Toll-like receptors (TLRs) (e.g., regulation of proliferation, the activity of NF-κB, gene transcription of apoptosis proteins, regulation of angiogenesis, HIF-1α protein expression) are used in experimental studies to better understand the pathogenesis of pancreatic cancer, for early diagnosis, and for more effective therapeutic intervention. There are known numerous examples of TLR agonists (e.g., TLR2/5 ligands, TLR6, TLR9) of antitumor effect. The direction of these studies is promising, but a small number of them does not allow for an accurate assessment of the impact of TLR expression disorders, proteins of these signaling pathways, or attempts to block or stimulate them, on the results of treatment of pancreatic cancer patients. It is known, however, that the expression disorders of proteins of innate antibacterial response signaling pathways occur not only in tumor tissue but also in peripheral blood leukocytes of pancreatic cancer patients (e.g., increased expression of TLR4, NOD1, TRAF6), which is one of the most important factors facilitating further tumor development. This review mainly focuses on the genetic aspects of signaling pathway disorders associated with innate antibacterial response in the pathogenesis and diagnosis of pancreatic cancer.

Identification of 5-Methoxy-2-(Diformylmethylidene)-3,3-Dimethylindole as an Anti-Influenza A Virus Agent

Influenza virus is estimated to cause 3–5 million severe complications and about 250–500 thousand deaths per year. Different kinds of anti-influenza virus drugs have been developed. However, the emergence of drug resistant strains has presented a big challenge for efficient antiviral therapy. Indole derivatives have been shown to exhibit both antiviral and anti-inflammatory activities. In this study, we adopted a cell-based system to screen for potential anti-IAV agents. Four indole derivatives (named 525A, 526A, 527A and 528A) were subjected to the antiviral screening, of which 526A was selected for further investigation. We reported that pre-treating cells with 526A protects cells from IAV infection. Furthermore, 526A inhibits IAV replication by inhibiting the expression of IAV genes. Interestingly, 526A suppresses the activation of IRF3 and STAT1 in host cells and thus represses the production of type I interferon response and cytokines in IAV-infected cells. Importantly, 526A also partially blocks the activation of RIG-I pathway. Taken together, these results suggest that 526A may be a potential anti-influenza A virus agent.

Role of invariant NKT cells in lipopolysaccharide-induced lethal shock during encephalomyocarditis virus infection

Viral infections can give rise to secondary bacterial infections. In the present study, we examined the role of invariant natural killer T (iNKT) cells in lipopolysaccharide (LPS)-induced lethal shock during encephalomyocarditis virus (EMCV) infection. Wild-type (WT) mice and Jα18 gene knockout (Jα18 KO) mice were inoculated with EMCV, 5days prior to challenging with LPS. The survival rate of Jα18 KO mice subjected to EMCV and LPS was significantly higher than that of WT mice. TNF-α and nitric oxide (NO) production were increased in WT mice, than that in Jα18 KO mice, after the administration of EMCV and LPS. EMCV infection increased the number of iNKT cells and IFN-γ production by iNKT cells in WT mice. Moreover, EMCV infection enhanced the expression of Toll-like receptor 4 (TLR4) in the lung and spleen. IFN-γ also increased the expression of TLR4 in splenocytes. These findings indicated that EMCV infection activated iNKT cells, and IFN-γ secreted from the iNKT cells up-regulated the expression of TLR4 in various tissues. As a result, EMCV-infected mice were susceptible to LPS and easily developed the lethal shock. In conclusion, iNKT cells were involved in the development of LPS-induced lethal shock during EMCV infection.

Combining Type I Interferons and 5-Aza-2'-Deoxycitidine to Improve Anti-Tumor Response against Melanoma

Resistance to IFN-I-induced antineoplastic effects has been reported in many tumors and arises, in part, from epigenetic silencing of IFN-stimulated genes by DNA methylation. We hypothesized that restoration of IFN-stimulated genes by co-administration of the demethylating drug 5-aza-2'-deoxycitidine (decitabine [DAC]) may enhance the susceptibility to IFN-I-mediated antitumoral effects in melanoma. We show that combined administration of IFN-I and DAC significantly inhibits the growth of murine and human melanoma cells, both in vitro and in vivo. Compared with controls, DAC/IFN-I-treated melanoma cells exhibited reduced cell growth, augmented apoptosis, and diminished migration. Moreover, IFN-I and DAC synergized to suppress the growth of three-dimensional human melanoma spheroids, altering tumor architecture. These direct antitumor effects correlated with induction of the IFN-stimulated gene Mx1. In vivo, DAC/IFN-I significantly reduced melanoma growth via stimulation of adaptive immunity, promoting tumor-infiltrating CD8⁺ T cells while inhibiting the homing of immunosuppressive CD11b⁺ myeloid cells and regulatory T cells. Accordingly, exposure of human melanoma cells to DAC/IFN-I induced the recruitment of immune cells toward the tumor in a Matrigel (Corning Life Sciences, Kennebunkport, ME)-based microfluidic device. Our findings underscore a beneficial effect of DAC plus IFN-I combined treatment against melanoma through both direct and immune-mediated anti-tumor effects.

Endothelial Dysfunction and Inflammation: Immunity in Rheumatoid Arthritis

Inflammation, as a feature of rheumatoid arthritis (RA), leads to the activation of endothelial cells (ECs). Activated ECs induce atherosclerosis through an increased expression of leukocyte adhesion molecules. Endothelial dysfunction (ED) is recognized as a failure of endothelial repair mechanisms. It is also an early preclinical marker of atherosclerosis and is commonly found in RA patients. RA is now established as an independent cardiovascular risk factor, while mechanistic determinants of ED in RA are still poorly understood. An expanding body of study has shown that EC at a site of RA is both active participant and regulator of inflammatory process. Over the last decade, a role for endothelial dysfunction in RA associated with cardiovascular disease (CVD) has been hypothesized. At the same time, several maintenance drugs targeting this phenomenon have been tested, which has promising results. Assessment of endothelial function may be a useful tool to identify and monitor RA patients.

The role of pattern recognition receptors in the innate recognition of Candida albicans

Candida albicans is both a commensal microorganism in healthy individuals and a major fungal pathogen causing high mortality in immunocompromised patients. Yeast-hypha morphological transition is a well known virulence trait of C. albicans. Host innate immunity to C. albicans critically requires pattern recognition receptors (PRRs). In this review, we summarize the PRRs involved in the recognition of C. albicans in epithelial cells, endothelial cells, and phagocytic cells separately. We figure out the differential recognition of yeasts and hyphae, the findings on PRR-deficient mice, and the discoveries on human PRR-related single nucleotide polymorphisms (SNPs).

The Effect of Glucose on the Release and Bioactivity of Exosomes From First Trimester Trophoblast Cells

CONTEXT

Hyperglycemia and hypoxia are risk factors of metabolic complication during pregnancy. The interactions between oxygen and glucose-sensing pathways that regulate exosome bioactivity from placental cells, however, have not been established.

OBJECTIVE

The aim of this study was to test the hypothesis that exosomal signaling by placental cells (defined as the number of exosomes released per unit time and their bioactivity) is responsive to extracellular glucose concentration.

METHODS

First-trimester primary trophoblast cells were incubated with D-glucose (5 mM or 25 mM) under 1%, 3%, or 8% O2 for 48 hours. Exosomes were isolated from cell-conditioned media by differential and buoyant density centrifugation. The total number of exosome vesicles was determined by quantifying immunoreactive exosomal CD63. The effect of exosomes on cytokine (granulocyte macrophage colony-stimulating factor, IL-2, IL-4, IL-6. IL-8, IL-10, interferon-γ, and TNF-α) release from endothelial cells was established by a protein solution array analysis.

RESULTS

Glucose (25 mM) significantly increased the release of exosomes from trophoblast cells at all oxygen tensions tested (by approximately 2-fold when compared with controls, P < .001). Exosomes (100 μg/mL exosomal protein) released from trophoblast cells significantly increased (P < .05) the release of all cytokines from human umbilical vein endothelial cells when compared with the control (ie, cells without exosomes), with the exception of IL-2 and IL-10 (P > .05).

CONCLUSIONS

The effects of high glucose on exosomes bioactivity may be recapitulated in vivo and is of clinical relevance in association with maternal insulin resistance (resulting in hyperglycemia) and preeclampsia (associated with placental insufficiency and hypoxia).

Vascular endothelial cell Toll-like receptor pathways in sepsis

The endothelium forms a vast network that dynamically regulates vascular barrier function, coagulation pathways and vasomotor tone. Microvascular endothelial cells are uniquely situated to play key roles during infection and injury, owing to their widespread distribution throughout the body and their constant interaction with circulating blood. While not viewed as classical immune cells, endothelial cells express innate immune receptors, including the Toll-like receptors (TLRs), which activate intracellular inflammatory pathways mediated through NF-κB and the MAP kinases. TLR agonists, including LPS and bacterial lipopeptides, directly upregulate microvascular endothelial cell expression of inflammatory mediators. Intriguingly, TLR activation also modulates microvascular endothelial cell permeability and the expression of coagulation pathway intermediaries. Microvascular thrombi have been hypothesized to trap microorganisms thereby limiting the spread of infection. However, dysregulated activation of endothelial inflammatory pathways is also believed to lead to coagulopathy and increased vascular permeability, which together promote sepsis-induced organ failure. This article reviews vascular endothelial cell innate immune pathways mediated through the TLRs as they pertain to sepsis, highlighting links between TLRs and coagulation and permeability pathways, and their role in healthy and pathologic responses to infection and sepsis.

17β-Estradiol enhances the activation of IFN-α signaling in B cells by down-regulating the expression of let-7e-5p, miR-98-5p and miR-145a-5p that target IKKε

The activation of IFN-α signaling in B cells contributes to the pathogenesis of systemic lupus erythematosus (SLE). Many studies suggest that estrogens are closely related to the gender difference in the prevalence of SLE. However, the underlying mechanism of the interaction between estrogens and the activation of IFN-α signaling in SLE B cells remains incompletely understood. In the present study, we first found that healthy female mice showed an up-regulated type I IFN-induced gene signature in B cells compared with age-matched male mice, and an in vivo study revealed that the gender difference was related to 17β-estradiol. Moreover, we found that 17β-estradiol could enhance the activation of IFN-α signaling in an ERα-dependent manner by down-regulating the expression of three microRNAs, including let-7e-5p, miR-98-5p and miR-145a-5p. These microRNAs could target the 3'UTR of the IKKε-encoding gene IKBKE directly and regulate the expression of IKKε, which can promote the activation of IFN-α signaling. In addition, compared with age-matched male mice, female mice showed a higher level of IKKε and lower levels of let-7e-5p, miR-98-5p and miR-145a-5p in B cells. Moreover, peripheral blood mononuclear cells from women showed a higher level of IKKε and lower levels of let-7e-5p, miR-98-5p and miR-145a-5p compared with those from age-matched men. These data suggest that 17β-estradiol amplifies the activation of IFN-α signaling in B cells via IKKε by down-regulating the expression of let-7e-5p, miR-98-5p and miR-145a-5p. Our findings may provide a new perspective for understanding the mechanism underlying the gender difference in the prevalence of SLE.

A cell-based screening system for anti-influenza A virus agents

Emerging of drug resistant influenza A virus (IAV) has been a big challenge for anti-IAV therapy. In this study, we describe a relatively easy and safe cell-based screening system for anti-IAV replication inhibitors using a non-replicative strain of IAV. A nickel (II) complex of polyhydroxybenzaldehyde N4-thiosemicarbazone (NiPT5) was recently found to exhibit anti-inflammatory activity in vivo and in vitro. NiPT5 impedes the signaling cascades that lead to the activation of NF-κB in response to different stimuli, such as LPS and TNFα. Using our cell-based screening system, we report that pretreating cells with NiPT5 protects cells from influenza A virus (IAV) and vesicular stomatitis virus (VSV) infection. Furthermore, NiPT5 inhibits replication of IAV by inhibiting transcription and translation of vRNAs of IAV. Additionally, NiPT5 reduces IAV-induced type I interferon response and cytokines production. Moreover, NiPT5 prevents activation of NF-κB, and IRF3 in response to IAV infection. These results demonstrate that NiPT5 is a potent antiviral agent that inhibits the early phase of IAV replication.