Recognition of Viral RNA by Pattern Recognition Receptors in the Induction of Innate Immunity and Excessive Inflammation During Respiratory Viral Infections

Hypervirulent fowl adenovirus serotype 4 elicits early innate immune response and promotes virus-induced cellular autophagy in the spleen

The recent emergence of hepatitis-hydropericardium syndrome caused by highly pathogenic fowl adenovirus serotype 4 (FAdV-4) has resulted in significant economic losses to the poultry industry. However, the early innate immune response of immune organs within 24 hpi and the induction of autophagy in vivo after FAdV-4 infection have not been fully elucidated. In this study, 35-day-old specific pathogen-free (SPF) chickens were artificially infected with hypervirulent FAdV-4, which resulted in a mortality rate of up to 90%. The results showed that FAdV-4 infection rapidly triggered the innate immune response in vivo of chickens, with the spleen eliciting a stronger innate immune response than the thymus and bursa. During the early stage of viral infection within 24 hpi, the main receptors TLR3/7/21, MDA5, and cGAS were activated via the NF-κB and TBK1/IRF7-dependent signaling pathways, which up-regulated production of inflammatory cytokines and type I interferons. Additionally, the expression levels of the autophagy-related molecules LC3B, Beclin1, and ATG5 were significantly up-regulated at 24 hpi, while degradation of SQSTM1/p62 was observed, suggesting that FAdV-4 infection elicits a complete autophagy response in the spleen. Besides, the colocalization of Fiber2 and LC3B suggested that FAdV-4 infection induced autophagy which benefits FAdV-4 replication in vivo. This study provides new insights into the immunoregulation signal pathways of the early innate immunity in response to hypervirulent FAdV-4 infection in vivo within 24 hpi and the close relationship between viral replication and autophagy.

Activation of the cGAS-STING pathway by viral dsDNA leading to M1 polarization of macrophages mediates antiviral activity against hepatitis B virus

BACKGROUND AND AIMS

Activation of the cGAS-STING pathway induces the production of type I interferons, initiating the antiviral immune response, which contributes to the clearance of pathogens. Previous studies have shown that STING agonists promote hepatitis B virus (HBV) clearance; however, few studies have investigated the effect of activating the cGAS-STING pathway in macrophages on HBV.

METHODS

The polarization status of HBV particle-stimulated RAW264.7 macrophages was analyzed. After stimulation with HBV particles, the analysis focused on determining whether the DNA sensors in RAW264.7 macrophages recognized the viral double-stranded DNA (dsDNA) and evaluating the activation of the cGAS-STING pathway. Coculture of mouse macrophages and hepatocytes harboring HBV was used to study the antiviral activity of HBV-stimulated RAW264.7 macrophages.

RESULTS

After stimulation with HBV particles, HBV relaxed circular DNA (rcDNA) was detected in RAW264.7 macrophages, and the protein expression of phospho-STING, phospho-TBK1, and phospho-IRF3 in the STING pathway was increased, as shown by Western blot analysis, which revealed that M1 polarization of macrophages was caused by increased expression of CD86. RT-PCR analyses revealed elevated expression of M1 macrophage polarization-associated cytokines such as TNFα, IL-1β, iNOS, and IFNα/β. In the coculture experiment, both HBsAg and HBeAg expression levels were significantly decreased in AML12-HBV1.3 cells cocultured with the supernatants of HBV-stimulated RAW264.7 macrophages.

CONCLUSION

The results suggest that macrophages can endocytose HBV particles. Additionally, viral dsDNA can be recognized by DNA pattern recognition receptors, which in turn activate the cGAS-STING pathway, promoting the M1 polarization of macrophages, while no significant M2 polarization is observed. Macrophages stimulated with HBV particles exhibit enhanced antiviral activity against HBV.

Differential Type-I Interferon Response in Buffy Coat Transcriptome of Individuals Infected with SARS-CoV-2 Gamma and Delta Variants

The innate immune system is the first line of defense against pathogens such as the acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The type I-interferon (IFN) response activation during the initial steps of infection is essential to prevent viral replication and tissue damage. SARS-CoV and SARS-CoV-2 can inhibit this activation, and individuals with a dysregulated IFN-I response are more likely to develop severe disease. Several mutations in different variants of SARS-CoV-2 have shown the potential to interfere with the immune system. Here, we evaluated the buffy coat transcriptome of individuals infected with Gamma or Delta variants of SARS-CoV-2. The Delta transcriptome presents more genes enriched in the innate immune response and Gamma in the adaptive immune response. Interactome and enriched promoter analysis showed that Delta could activate the INF-I response more effectively than Gamma. Two mutations in the N protein and one in the nsp6 protein found exclusively in Gamma have already been described as inhibitors of the interferon response pathway. This indicates that the Gamma variant evolved to evade the IFN-I response. Accordingly, in this work, we showed one of the mechanisms that variants of SARS-CoV-2 can use to avoid or interfere with the host Immune system.

E3 ligase HECTD3 promotes RNA virus replication and virus-induced inflammation via K33-linked polyubiquitination of PKR

Uncontrolled viral replication and excessive inflammation are the main causes of death in the host infected with virus. Hence inhibition of intracellular viral replication and production of innate cytokines, which are the key strategies of hosts to fight virus infections, need to be finely tuned to eliminate viruses while avoid harmful inflammation. The E3 ligases in regulating virus replication and subsequent innate cytokines production remain to be fully characterized. Here we report that the deficiency of the E3 ubiquitin-protein ligase HECTD3 results in accelerated RNA virus clearance and reduced inflammatory response both in vitro and in vivo. Mechanistically, HECTD3 interacts with dsRNA-dependent protein kinase R (PKR) and mediates Lys33-linkage of PKR, which is the first non-proteolytic ubiquitin modification for PKR. This process disrupts the dimerization and phosphorylation of PKR and subsequent EIF2α activation, which results in the acceleration of virus replication, but promotes the formation of PKR-IKK complex and subsequent inflammatory response. The finding suggests HECTD3 is the potential therapeutic target for simultaneously restraining RNA virus replication and virus-induced inflammation once pharmacologically inhibited.

The roles of critical pro-inflammatory cytokines in the drive of cytokine storm during SARS-CoV-2 infection

In patients with severe COVID-19, acute respiratory distress syndrome (ARDS), multiple organ dysfunction syndrome (MODS), and even mortality can result from cytokine storm, which is a hyperinflammatory medical condition caused by the excessive and uncontrolled release of pro-inflammatory cytokines. High levels of numerous crucial pro-inflammatory cytokines, such as interleukin-1 (IL-1), IL-2, IL-6, tumor necrosis factor-α, interferon (IFN)-γ, IFN-induced protein 10 kDa, granulocyte-macrophage colony-stimulating factor, monocyte chemoattractant protein-1, and IL-10 and so on, have been found in severe COVID-19. They participate in cascade amplification pathways of pro-inflammatory responses through complex inflammatory networks. Here, we review the involvements of these critical inflammatory cytokines in SARS-CoV-2 infection and discuss their potential roles in triggering or regulating cytokine storm, which can help to understand the pathogenesis of severe COVID-19. So far, there is rarely effective therapeutic strategy for patients with cytokine storm besides using glucocorticoids, which is proved to result in fatal side effects. Clarifying the roles of key involved cytokines in the complex inflammatory network of cytokine storm will help to develop an ideal therapeutic intervention, such as neutralizing antibody of certain cytokine or inhibitor of some inflammatory signal pathways.

The Latest Cellular and Molecular Mechanisms of COVID-19 on Non-Lung Organs

Understanding the transmission pathways of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) will aid in developing effective therapies directed at the virus’s life cycle or its side effects. While severe respiratory distress is the most common symptom of a coronavirus 2019 (COVID-19) infection, the virus is also known to cause damage to almost every major organ and system in the body. However, it is not obvious whether pathological changes in extra-respiratory organs are caused by direct infection, indirect, or combination of these effects. In this narrative review, we first elaborate on the characteristics of SARS-CoV-2, followed by the mechanisms of this virus on various organs such as brain, eye, and olfactory nerve and different systems such as the endocrine and gastrointestinal systems.

Immunometabolic Signature during Respiratory Viral Infection: A Potential Target for Host-Directed Therapies

RNA viruses are known to induce a wide variety of respiratory tract illnesses, from simple colds to the latest coronavirus pandemic, causing effects on public health and the economy worldwide. Influenza virus (IV), parainfluenza virus (PIV), metapneumovirus (MPV), respiratory syncytial virus (RSV), rhinovirus (RhV), and coronavirus (CoV) are some of the most notable RNA viruses. Despite efforts, due to the high mutation rate, there are still no effective and scalable treatments that accompany the rapid emergence of new diseases associated with respiratory RNA viruses. Host-directed therapies have been applied to combat RNA virus infections by interfering with host cell factors that enhance the ability of immune cells to respond against those pathogens. The reprogramming of immune cell metabolism has recently emerged as a central mechanism in orchestrated immunity against respiratory viruses. Therefore, understanding the metabolic signature of immune cells during virus infection may be a promising tool for developing host-directed therapies. In this review, we revisit recent findings on the immunometabolic modulation in response to infection and discuss how these metabolic pathways may be used as targets for new therapies to combat illnesses caused by respiratory RNA viruses.

Strategies Tackling Viral Replication and Inflammatory Pathways as Early Pharmacological Treatment for SARS-CoV-2 Infection: Any Potential Role for Ketoprofen Lysine Salt?

COVID-19 is an infective disease resulting in widespread respiratory and non-respiratory symptoms prompted by SARS-CoV-2 infection. Interaction between SARS-CoV-2 and host cell receptors prompts activation of pro-inflammatory pathways which are involved in epithelial and endothelial damage mechanisms even after viral clearance. Since inflammation has been recognized as a critical step in COVID-19, anti-inflammatory therapies, including both steroids and non-steroids as well as cytokine inhibitors, have been proposed. Early treatment of COVID-19 has the potential to affect the clinical course of the disease regardless of underlying comorbid conditions. Non-steroidal anti-inflammatory drugs (NSAIDs), which are widely used for symptomatic relief of upper airway infections, became the mainstay of early phase treatment of COVID-19. In this review, we discuss the current evidence for using NSAIDs in early phases of SARS-CoV-2 infection with focus on ketoprofen lysine salt based on its pharmacodynamic and pharmacokinetic features.

Forsythiaside A improves Influenza A virus infection through TLR7 signaling pathway in the lungs of mice

Background

Influenza A virus infection due to drug resistance and side effects of the conventional antiviral drugs yet remains a serious public health threat for humans and animals. Forsythiaside A is an effective ingredient isolated from the Chinese herbal medicine forsythia. It has various pharmacological effects and has a good therapeutic effect against a variety of infectious diseases. This study aimed to further explore the immunological mechanism of Forsythiaside A in the treatment of influenza virus-infected mice and its effect on the Toll-like receptor 7 (TLR7) signaling pathway in the lungs of these mice.

Methods

C57/BL6J mice and TLR7−/− mice were infected with the FM1 strains (H1N1 and A/FM/1/4) of the Influenza A virus. Each group of experimental mice were divided into the mock, virus, oseltamivir, and Forsythiaside A groups. Weight change, lung index change, and the mRNA and protein expression levels of key factors in the TLR7 signaling pathway were detected. Flow cytometry was used to detect the changes in the Th1/Th2 and Th17/Treg ratios.

Results

After infection with the Influenza A virus, the weight loss of C57/BL6J mice treated with forsythoside A and oseltamivir decreased, and the pathological tissue sections showed that the inflammatory damage was reduced. The expression levels of the key factors, TLR7, myeloid differentiation factor 88(Myd88), and nuclear factor-kappa B (NF-κB) in the TLR7 signaling pathway were significantly reduced. Flow cytometry showed that Th1/Th2 and Th17/Treg ratios decreased after Forsythiaside A treatment. In the TLR7−/− mice, there was no significant change after Forsythiaside A treatment in the virus group.

Conclusions

Forsythiaside A affects the TLR7 signaling pathway in mouse lung immune cells and reduces the inflammatory response caused by the Influenza A virus FM1 strain in mouse lungs.

TLR2 axis on peripheral blood mononuclear cells regulates inflammatory responses to non-infectious immature dengue virus particles

Severe dengue virus (DENV) infection is characterized by exacerbated inflammatory responses that lead to endothelial dysfunction and plasma leakage. We have recently demonstrated that Toll-like receptor 2 (TLR2) on blood monocytes senses DENV infection leading to endothelial activation. Here, we report that non-infectious immature DENV particles, which are released in large numbers by DENV-infected cells, drive endothelial activation via the TLR2 axis. We show that fully immature DENV particles induce a rapid, within 6 hours post-infection, inflammatory response in PBMCs. Furthermore, pharmacological blocking of TLR2/TLR6/CD14 and/or NF-kB prior to exposure of PBMCs to immature DENV reduces the initial production of inter alia TNF-α and IL-1β by monocytes and prevents endothelial activation. However, prolonged TLR2 block induces TNF-α production and leads to exacerbated endothelial activation, indicating that TLR2-mediated responses play an important role not only in the initiation but also the resolution of inflammation. Altogether, these data indicate that the maturation status of the virus has the potential to influence the kinetics and extent of inflammatory responses during DENV infection.

H1N1 Influenza Virus-Infected Nasal Mucosal Epithelial Progenitor Cells Promote Dendritic Cell Recruitment and Maturation

The barrier function of nasal mucosal epithelial cells plays an irreplaceable role in the spread and expansion of viruses in the body. This study found that influenza A virus H1N1 could induce apoptosis of nasal mucosal epithelial progenitor cells, cause an inflammatory response, and trigger the maturation and recruitment of nasal submucosal dendritic cells (DCs), but the mechanism remained unclear. Therefore, we used RNA sequencing and high-resolution untargeted metabolomics to sequence and perform combined bioinformatic analysis of H1N1 virus-infected nasal mucosal epithelial cells from 6 different patients. The abnormal arginine metabolism signaling pathway caused by H1N1 virus infection was screened out, and arginase inhibitors were used to interfere with the abnormal arginine metabolism and the maturation and recruitment of submucosal DCs caused by the H1N1 virus in vitro and in vivo. We conclude that H1N1 influenza virus promotes the recruitment and maturation of submucosal DCs by causing abnormal arginine metabolism in nasal mucosal epithelial cells, thereby triggering respiratory mucosal immunity.

Current Status of Epitranscriptomic Marks Affecting lncRNA Structures and Functions

Long non-coding RNAs (lncRNAs) belong to a class of non-protein-coding RNAs with their lengths longer than 200 nucleotides. Most of the mammalian genome is transcribed as RNA, yet only a small percent of the transcribed RNA corresponds to exons of protein-coding genes. Thus, the number of lncRNAs is predicted to be several times higher than that of protein-coding genes. Because of sheer number of lncRNAs, it is often difficult to elucidate the functions of all lncRNAs, especially those arising from their relationship to their binding partners, such as DNA, RNA, and proteins. Due to their binding to other macromolecules, it has become evident that the structures of lncRNAs influence their functions. In this regard, the recent development of epitranscriptomics (the field of study to investigate RNA modifications) has become important to further elucidate the structures and functions of lncRNAs. In this review, the current status of lncRNA structures and functions influenced by epitranscriptomic marks is discussed.

Exploring the total flavones of Abelmoschus manihot against IAV-induced lung inflammation by network pharmacology

Background

Abelmoschus manihot (L.) Medicus (AM) is a medicinal plant with various biological activities, including anti-inflammatory, antioxidant, antiviral and immunomodulatory. Previous studies have identified total flavones as the primary bioactive ingredient of AM (termed TFA). However, its role and mechanism in counteracting Influenza A virus (IAV) infection are yet to be explored. Therefore, the study aims to study the antiviral and anti-inflammatory effects of TFA on IAV in vitro and in vivo.

Methods

A network pharmacology-based approach was applied to identify the antiviral mechanism of TFA against IAV. For the mechanism validation, the cytopathic effect reduction assay evaluated the antiviral activity of TFA in vitro. Meanwhile, the mice were intranasally infected with IAV to induce lung infection. The antiviral effect of TFA was observed in vivo. Further investigation whether the reprogramming microbiome in the TFA treatment group affected antiviral, we conducted a microbial-transfer study with co-housing experiments.

Results

By applying the network pharmacology-based methods (PPI, GO, and KEGG), we identified 167 potential targets of TFA action, among which 62 targets were related to IAV pathogenesis. A core network containing the pro-inflammatory TNFα, IL-6, IL-1β, MAPKs, and RIG-I receptor signaling pathway was further confirmed as the crucial targets for anti-influenza efficacy of TFA. We demonstrate that TFA provided profound protection against pulmonary IAV infection, which alleviated inflammatory responses, decreased MAPK signaling pathway and expedited viral eradiation.

Conclusions

Our study unveils a pivotal role for TFA in controlling viral infection and dampening pathology, making it a promising strategy for treating IAV-induced pneumonia.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03509-0.

SARS-CoV-2-Specific Immune Response and the Pathogenesis of COVID-19

The review aims to consolidate research findings on the molecular mechanisms and virulence and pathogenicity characteristics of coronavirus disease (COVID-19) causative agent, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and their relevance to four typical stages in the development of acute viral infection. These four stages are invasion; primary blockade of antiviral innate immunity; engagement of the virus's protection mechanisms against the factors of adaptive immunity; and acute, long-term complications of COVID-19. The invasion stage entails the recognition of the spike protein (S) of SARS-CoV-2 target cell receptors, namely, the main receptor (angiotensin-converting enzyme 2, ACE2), its coreceptors, and potential alternative receptors. The presence of a diverse repertoire of receptors allows SARS-CoV-2 to infect various types of cells, including those not expressing ACE2. During the second stage, the majority of the polyfunctional structural, non-structural, and extra proteins SARS-CoV-2 synthesizes in infected cells are involved in the primary blockage of antiviral innate immunity. A high degree of redundancy and systemic action characterizing these pathogenic factors allows SARS-CoV-2 to overcome antiviral mechanisms at the initial stages of invasion. The third stage includes passive and active protection of the virus from factors of adaptive immunity, overcoming of the barrier function at the focus of inflammation, and generalization of SARS-CoV-2 in the body. The fourth stage is associated with the deployment of variants of acute and long-term complications of COVID-19. SARS-CoV-2's ability to induce autoimmune and autoinflammatory pathways of tissue invasion and development of both immunosuppressive and hyperergic mechanisms of systemic inflammation is critical at this stage of infection.

Molecular cloning and functional analysis of Macaca mulatta STING

Stimulator of interferon gene (STING), an adaptor molecule in the immune system, is involved in mediating the response to viral and bacterial infections, anti-tumor immunity, autoimmune diseases, and lipid metabolism. There have been reports on the cloning and function of STING in humans, pigs, chickens, and cats; however, STING has not been characterized in non-human primates or monkeys to date. Therefore, in this study, the rhesus macaque (Macaca mulata) STING gene was cloned, and we performed preliminary functional tests to examine its role in the interferon (IFN) pathway. The M. mulatta STING complementary DNA was 1140 bp in length and encoded 380 amino acid residues. Phylogenetic analysis showed that Homo sapiens and M. mulatta STING are closely related and clustered on the same branch. M. mulatta STING was confirmed to increase the promoter activities of IFN-β, nuclear factor-κB, and interferon-sensitive response element, and STING overexpression increased the mRNA levels of IFN-α, IFN-β, and interferon regulatory factor 3. Infection of Marc-145 cells with porcine reproductive and respiratory syndrome virus activated STING, and its expression increased along with increases in viral multiplicity of infection titer and time. Moreover, STING expression was time- and dose-dependently up-regulated by poly (I:C) and poly (dA:dT) treatments in Marc-145 cells. In summary, these results highlight STING as a vital immune system signal protein in the IFN pathway. This study provides a basis for understanding the immune characteristics of M. mulatta, and may have important implications for both monkey and human diseases.

Interferon-Inducible LINC02605 Promotes Antiviral Innate Responses by Strengthening IRF3 Nuclear Translocation

Non-coding RNAs represent a class of important regulators in immune response. Previously, LINC02605 was identified as a candidate regulator in innate immune response by lncRNA microarray assays. In this study, we systematically analyzed the functions and the acting mechanisms of LINC02605 in antiviral innate immune response. LINC02605 was up-regulated by RNA virus, DNA virus, and type I IFNs in NF-κB and Jak-stat dependent manner. Overexpression of LINC02605 promotes RNA virus-induced type I interferon production and inhibited viral replication. Consistently, knockdown of LINC02605 resulted in reduced antiviral immune response and increased viral replication. Mechanistically, LINC02605 released the inhibition of hsa-miR-107 on the expression of phosphatase and tensin homolog (PTEN). By microRNA mimics and inhibitors, hsa-miR-107 was demonstrated to not only inhibit PTEN’s expression but also negatively regulate the antiviral immune response. Knockdown of LINC02605 led to the reduction of PTEN expression both in mRNA and protein levels. Overexpression of LINC02605 had an opposite impact. Moreover, LINC02605 attenuated the serine 97 phosphorylation level of interferon regulatory factor 3 (IRF3) by promoting PTEN expression. Nucleoplasmic fragmentation assay showed that knocking down LINC02605 inhibited the nuclear translocation of IRF3, rendering the host cells more susceptible to viral invasion, while overexpression showed opposite effects. Therefore, LINC02605 is an induced lncRNA by viral infection and plays a positive feedback in antiviral immune response through modulating the nuclear translocation of IRF3.

A novel hypothesis for COVID-19 pathogenesis: Retinol depletion and retinoid signaling disorder

The SARS-CoV-2 virus has caused a worldwide COVID-19 pandemic. In less than a year and a half, more than 200 million people have been infected and more than four million have died. Despite some improvement in the treatment strategies, no definitive treatment protocol has been developed. The pathogenesis of the disease has not been clearly elucidated yet. A clear understanding of its pathogenesis will help develop effective vaccines and drugs. The immunopathogenesis of COVID-19 is characteristic with acute respiratory distress syndrome and multiorgan involvement with impaired Type I interferon response and hyperinflammation. The destructive systemic effects of COVID-19 cannot be explained simply by the viral tropism through the ACE2 and TMPRSS2 receptors. In addition, the recently identified mutations cannot fully explain the defect in all cases of Type I interferon synthesis. We hypothesize that retinol depletion and resulting impaired retinoid signaling play a central role in the COVID-19 pathogenesis that is characteristic for dysregulated immune system, defect in Type I interferon synthesis, severe inflammatory process, and destructive systemic multiorgan involvement. Viral RNA recognition mechanism through RIG-I receptors can quickly consume a large amount of the body's retinoid reserve, which causes the retinol levels to fall below the normal serum levels. This causes retinoid insufficiency and impaired retinoid signaling, which leads to interruption in Type I interferon synthesis and an excessive inflammation. Therefore, reconstitution of the retinoid signaling may prove to be a valid strategy for management of COVID-19 as well for some other chronic, degenerative, inflammatory, and autoimmune diseases.

Polymorphisms of RIG-I-like receptor influence HBV clearance in Chinese Han population

Retinoic acid-inducible gene I-like receptors (RLRs) play an essential role in human innate immune, which may influence the spontaneous clearance of hepatitis B virus (HBV) infection. We aimed to investigate whether the SNPs in RLR family were associated with HBV spontaneous clearance. The current study included 82 participants with spontaneous clearance, 601 asymptomatic hepatitis B surface antigen (HBsAg) carriers, and 168 participants with chronic hepatitis B (CHB). Six SNPs (DDX58 rs3824456, rs3205166, DHX58 rs2074160, rs2074158, IFIH1 rs2111485, rs3747517) were genotyped to explore their association with HBV spontaneous clearance. Patients carrying the mutant allele C at rs3824456 or A at rs2074160 were more likely to achieve spontaneous clearance compared with asymptomatic HBsAg carriers (additive model: odds ratio [OR] = 0.69, 95% confidence interval [CI] =  0.49-0.97; dominant model: OR = 0.54, 95% CI = 0.31-0.95, respectively). In addition, patients carrying the mutant allele G at rs2111485 were more likely to achieve spontaneous clearance compared with CHB (dominant model: OR = 0.47, 95% CI = 0.25-0.87). The mutations were protective factors for HBV spontaneous clearance. These results suggest the DDX58 rs3824456, DHX58 s2074160, IFIH1 rs2111485 were associated with spontaneous clearance of HBV, which may be predictive markers in the Chinese Han population of HBV.

An overview of Betacoronaviruses-associated severe respiratory syndromes, focusing on sex-type-specific immune responses

Emerging beta-coronaviruses (β-CoVs), including Severe Acute Respiratory Syndrome CoV-1 (SARS-CoV-1), Middle East Respiratory Syndrome-CoV (MERS-CoV), and Severe Acute Respiratory Syndrome CoV-2 (SARS-CoV-2, the cause of COVID19) are responsible for acute respiratory illnesses in human. The epidemiological features of the SARS, MERS, and new COVID-19 have revealed sex-dependent variations in the infection, frequency, treatment, and fatality rates of these syndromes. Females are likely less susceptible to viral infections, perhaps due to their steroid hormone levels, the impact of X-linked genes, and the sex-based immune responses. Although mostly inactive, the X chromosome makes the female's immune system more robust. The extra immune-regulatory genes of the X chromosome are associated with lower levels of viral load and decreased infection rate. Moreover, a higher titer of the antibodies and their longer blood circulation half-life are involved in a more durable immune protection in females. The activation rate of the immune cells and the production of TLR7 and IFN are more prominent in females. Although the bi-allelic expression of the immune regulatory genes can sometimes lead to autoimmune reactions, the higher titer of TLR7 in females is further associated with a stronger anti-viral immune response. Considering these sex-related differences and the similarities between the SARS, MERS, and COVID-19, we will discuss them in immune responses against the β-CoVs-associated syndromes. We aim to provide information on sex-based disease susceptibility and response. A better understanding of the evasion strategies of pathogens and the host immune responses can provide worthful insights into immunotherapy, and vaccine development approaches.

TBK1 regulates the induction of innate immune response against GCRV by phosphorylating IRF3 in rare minnow (Gobiocypris rarus)

Rare minnow (Gobiocypris rarus), a small cyprinid species that is highly sensitive to the grass carp reovirus (GCRV), is regarded as an ideal model to study the mechanisms of innate immunity in fish. In the present study, a TBK1 homologue from rare minnow (GrTBK1) was identified and its roles in defence against viral infection were investigated. Sequence analysis showed that GrTBK1 encoded a 727-amino acid peptide which shared 98% and 72% identity to the black carp (Mylopharyngodon piceus) and human (Homo sapiens) orthologues, respectively. The amino acid sequence analysis demonstrated that GrTBK1 contains a conserved Serine/Threonine protein kinases catalytic domain (S_TKc) at the N-terminus. Furthermore, cellular distribution proved that GrTBK1 was located in the cytoplasm region. Quantitative real-time PCR analysis revealed that GrTBK1 was ubiquitously expressed in all examined organs, but especially highly in liver. Temporal expression analysis in vivo showed that the expression levels of GrTBK1 were obviously up-regulated in response to GCRV infection. Meanwhile, qRT-PCR assay revealed that the levels of S7 RNA, an important segment of GCRV genome, were higher in the liver than in other tissues. This indicates that GrTBK1 might play a crucial role in responses to GCRV infection in fish. In addition, GrTBK1 activated several type I interferon (IFN) promoters and induced the expression of downstream type I IFN-stimulated genes (ISGs). Furthermore, GrTBK1 obviously phosphorylated the interferon regulatory factor 3 (IRF3). Furthermore, overexpression of GrTBK1 remarkably decreased the GCRV proliferation. In summary, we systematically characterized GrTBK1 and illustrated its role in the innate immune response to GCRV infections.

Host innate immune responses of geese infected with goose origin nephrotic astrovirus

A novel goose astrovirus (GoAstV) outbreak in goslings, characterized by severe articular and visceral gout with high mortality, occurred in China. Although the pathogenesis of GoAstV-infected goslings has been explored in several studies, the host-immune response remains unclear. In this study, a goose astrovirus was isolated from goslings in Xiaogan, and designated as the HBXG strain. The full-length genome of HBXG was 7170 nt. A sequence analysis and phylogenetic trees revealed HBXG belonged to the novel GoAstV. We evaluated the viral distribution systematically and estimated immune related gene expression in HBXG-infected goslings. Results showed that GoAstV replicated quickly in many tissues and the highest titer was observed in the kidney, which reached 10^9.6 copies. TLR3, RIG-I and MDA5 were involved in the host-immune response to GoAstV, and the expression of IFN types I (IFN-α, IFN-β), inflammatory cytokines (IL-8, IL-10, TNF-α), antiviral proteins (Mx, OASL, PKR) and MHC-I were also upregulated during the infection. In contrast, the expression of proinflammatory cytokines (IL-1β, IL-6) and MHC-II were inhibited at 3 dpi. This study suggests that GoAstV is highly pathogenic to goslings, causing multiple systemic infections in tissues and the host-immune response is activated early in infection. However, rapid viral replication, suppression of inflammatory cytokines (IL-1β, IL-6) and MHC-II expressions were the possible reasons why the host-immune response cannot provide enough protection against GoAstV infection. This study is the first report to illuminate the immune response in goslings infected with GoAstV and offers insight into the pathogenesis of GoAstV.

Protein Phosphatase PP1 Negatively Regulates IRF3 in Response to GCRV Infection in Grass Carp (Ctenopharyngodon idella)

Protein phosphatase-1 (PP1) has an important role in many cell functions, such as cell differentiation, development, immune response and tumorigenesis. However, the specific role of PP1 in the antiviral response in fish remains to be elucidated. In this study, the PPP1R3G homolog was identified in the grass carp (Ctenopharyngodon idella) and its role in defence against the GCRV infection was investigated. Phylogenetic analysis demonstrated that CiPPP1R3G clustered with homologues from other teleosts. Temporal expression analysis in vivo revealed that the expression level of CiPPP1R3G was significantly up-regulated in response to GCRV infection in grass carps, especially in the intestine and head-kidney. Cellular distribution analysis revealed that CiPPP1R3G was located in the nucleus and cytoplasm. Overexpression of CiPPP1R3G significantly negatively regulated the expression of CiIRF3, thus inhibiting its activation. In summary, we systematically analyzed the PPP1R3G gene in grass carp and illustrated its function as a negative regulator in the anti-GCRV immune responses.

Role of DAMPs in respiratory virus-induced acute respiratory distress syndrome-with a preliminary reference to SARS-CoV-2 pneumonia

When surveying the current literature on COVID-19, the "cytokine storm" is considered to be pathogenetically involved in its severe outcomes such as acute respiratory distress syndrome, systemic inflammatory response syndrome, and eventually multiple organ failure. In this review, the similar role of DAMPs is addressed, that is, of those molecules, which operate upstream of the inflammatory pathway by activating those cells, which ultimately release the cytokines. Given the still limited reports on their role in COVID-19, the emerging topic is extended to respiratory viral infections with focus on influenza. At first, a brief introduction is given on the function of various classes of activating DAMPs and counterbalancing suppressing DAMPs (SAMPs) in initiating controlled inflammation-promoting and inflammation-resolving defense responses upon infectious and sterile insults. It is stressed that the excessive emission of DAMPs upon severe injury uncovers their fateful property in triggering dysregulated life-threatening hyperinflammatory responses. Such a scenario may happen when the viral load is too high, for example, in the respiratory tract, "forcing" many virus-infected host cells to decide to commit "suicidal" regulated cell death (e.g., necroptosis, pyroptosis) associated with release of large amounts of DAMPs: an important topic of this review. Ironically, although the aim of this "suicidal" cell death is to save and restore organismal homeostasis, the intrinsic release of excessive amounts of DAMPs leads to those dysregulated hyperinflammatory responses-as typically involved in the pathogenesis of acute respiratory distress syndrome and systemic inflammatory response syndrome in respiratory viral infections. Consequently, as briefly outlined in this review, these molecules can be considered valuable diagnostic and prognostic biomarkers to monitor and evaluate the course of the viral disorder, in particular, to grasp the eventual transition precociously from a controlled defense response as observed in mild/moderate cases to a dysregulated life-threatening hyperinflammatory response as seen, for example, in severe/fatal COVID-19. Moreover, the pathogenetic involvement of these molecules qualifies them as relevant future therapeutic targets to prevent severe/ fatal outcomes. Finally, a theory is presented proposing that the superimposition of coronavirus-induced DAMPs with non-virus-induced DAMPs from other origins such as air pollution or high age may contribute to severe and fatal courses of coronavirus pneumonia.

SARS-CoV-2: Immune Response Elicited by Infection and Development of Vaccines and Treatments

The World Health Organization (WHO) announced in March a pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). This new infectious disease was named Coronavirus Disease 19 (COVID-19), and at October 2020, more than 39,000,000 cases of SARS-CoV-2 have been detected worldwide leading to near 1,100,000 deaths. Clinically, COVID-19 is characterized by clinical manifestations, such as fever, dry cough, headache, and in more severe cases, respiratory distress. Moreover, neurological-, cardiac-, and renal-related symptoms have also been described. Clinical evidence suggests that migration of immune cells to the affected organs can produce an exacerbated release of proinflammatory mediators that contribute to disease and render the immune response as a major player during the development of the COVID-19 disease. Due to the current sanitary situation, the development of vaccines is imperative. Up to the date, 42 prototypes are being tested in humans in different clinical stages, with 10 vaccine candidates undergoing evaluation in phase III clinical trials. In the same way, the search for an effective treatment to approach the most severe cases is also in constant advancement. Several potential therapies have been tested since COVID-19 was described, including antivirals, antiparasitic and immune modulators. Recently, clinical trials with hydroxychloroquine-a promising drug in the beginning-were suspended. In addition, the Food and Drug Administration (FDA) approved convalescent serum administration as a treatment for SARS-CoV-2 patients. Moreover, monoclonal antibody therapy is also under development to neutralize the virus and prevent infection. In this article, we describe the clinical manifestations and the immunological information available about COVID-19 disease. Furthermore, we discuss current therapies under study and the development of vaccines to prevent this disease.

Molecular cloning, functional characterization and expression analysis of P65 subunit in response to GCRV infection in rare minnow (Gobiocypris rarus)

P65, the all-important subunit of the transcription factor NF-κB, plays an important role in the regulation of immune response. In this study, the cDNA of P65 subunit of rare minnow Gobiocypris rarus (GrP65) was cloned, and its expression patterns and functional role in rare minnow were investigated. The GrP65cDNA encodes a polypeptide of 573 amino acids, containing a well-conserved Rel-homology domain (RHD). The amino acid sequence analysis showed that GrP65 shared 81% and 69% identity to the grass carp (Ctenopharyngodon idella) and human (Homo sapiens) orthologous, respectively. Phylogenetic analysis revealed that GrP65 clustered with homologues from other teleosts. Cellular distribution anallysis demonstrated that GrP65 was located in the cytoplasm and nucleus. Quantitative real-time PCR analysis showed that GrP65 was ubiquitously expressed in all examined tissues, but especially highly in liver. Temporal expression analysis in vivo showed that the expression levels of GrP65 were significantly up-regulated in liver in response to GCRV infection, which suggested that GrP65 might play a crucial role in recognition and responses to GCRV infection in fish. In addition, GrP65 activated several interferon (IFN) promoters and induced the expression of downstream IFN-stimulated genes (ISGs). Furthermore, overexpression of P65 remarkably decreased the GCRV proliferation, while knockdown of P65 obtained opposite effects. In summary, we systematically characterized GrP65 and demonstrated its role in the innate immune response to GCRV infections.

Chikungunya virus infection induces differential inflammatory and antiviral responses in human monocytes and monocyte-derived macrophages

Chikungunya virus (CHIKV) is a zoonotic arthropod-borne virus that has caused several outbreaks in tropical and subtropical areas worldwide during the last 50 years. The virus is known to target different human cell types throughout the course of infection including epithelial and endothelial cells, fibroblasts, primary monocytes and monocyte-derived macrophages (MDMs). The two latter are phagocytic cell populations of the innate immune system which are involved in some aspects of CHIKV pathogenesis. However, monocytes and macrophages also potentially contribute to the control of viral replication through the expression of different pattern recognition receptors sensing viral pathogens and subsequently, inducing an type I interferone (IFN-I)-dependent antiviral immune response. The aim of this study was to determine the modulation of the expression of Toll-like receptors (TLRs), cytokine secretion capabilities and antiviral factor production in monocytes and MDMs following infection with CHIKV. Moreover, we sought to determine the replication kinetics of CHIKV in these two cell populations. We found that the maximum peak of CHIKV replication was observed between 18- and 24-hours post-infection (hpi), while after that the is strongly reduced. Furthermore, CHIKV infection induced the pro-inflammatory cytokine production starting from the first 6 hpi in both monocytes and MDMs, with similar kinetics but different protein levels. In contrast, the kinetics of transcriptional expression of some TLRs were different between both cell types. In addition, IFN-I, 2',5'-oligoadenylate synthetase 1 (OAS1), and double-stranded RNA-activated protein kinase R (PKR) mRNA levels were detected in response to CHIKV infection of monocytes and MDMs, resulting the highest expression levels at 48 hpi. In conclusion, our data provides evidence that CHIKV infection activates the TLR pathways in primary monocytes and MDMs, which play a crucial role in CHIKV pathogenesis and/or host defense, differentially. However, additional studies are required to determine the functional role of TLRs in monocytes and MDMs.

Circulating Levels of Interleukin-6 and Interleukin-10, But Not Tumor Necrosis Factor-Alpha, as Potential Biomarkers of Severity and Mortality for COVID-19: Systematic Review with Meta-analysis

PURPOSE

Cytokine storm, an uncontrolled overproduction of inflammatory cytokines contributing to an aberrant systemic inflammatory response, is a major pathological feature of acute respiratory distress syndromes being severe manifestations of COVID-19, thus highlighting its potential as a biomarker and therapeutic target for COVID-19. We aimed to determine associations of circulating levels of inflammatory cytokines with severity and mortality of COVID-19 by systematic review and meta-analysis.

METHODS

A comprehensive literature search in electronic databases consisting of PubMed, Scopus, and Cochrane Library and in a hand searching of reference lists from inception to July 31, 2020, was performed using the following search terms: COVID-19, interleukin (IL)-6, IL-10, and tumor necrosis factor-alpha (TNF-α). Mean difference (MD) from individual studies was pooled using a random-effects model. Quality assessment, publication bias, meta-regression, subgroup, and sensitivity analyses were performed.

RESULTS

A total of 6212 COVID-19 patients from 24 eligible studies were included. Compared with non-severe COVID-19 patients, systemic levels of IL-6 and IL-10, but not TNF-α, were significantly elevated in severe COVID-19 patients (MD = 18.63, 95% CI: 10.91, 26.35, P < 0.00001; MD = 2.61, 95% CI: 2.00, 2.32, P < 0.00001; respectively). For COVID-19 mortality, circulating levels of IL-6, IL-10, and TNF-α were found to be significantly increased in non-survivors when compared with survivors (MD = 57.82, 95% CI: 10.04, 105.59, P = 0.02; MD = 4.94, 95% CI: 3.89, 6.00, P < 0.00001; MD = 5.60, 95% CI: 4.03, 7.17, P < 0.00001; respectively).

CONCLUSION

Circulating levels of IL-6 and IL-10 might have great potential as biomarkers for the disease severity and mortality in COVID-19 patients.

Vaccines for COVID-19: perspectives from nucleic acid vaccines to BCG as delivery vector system

This article discusses standard and new disruptive strategies in the race to develop an anti-COVID-19 vaccine. We also included new bioinformatic data from our group mapping immunodominant epitopes and structural analysis of the spike protein. Another innovative approach reviewed here is the use of BCG vaccine as priming strategy and/or delivery system expressing SARS-CoV-2 antigens.

The role of medicinal products in the treatment of inflammatory bowel diseases (IBD) through inhibition of TLR4/NF-kappaB pathway

Inflammatory bowel disease (IBD) is a lifelong and recurrent disease of the gastrointestinal tract that afflicts many people in the world. Growing evidence has currently indicated that dysfunction of immune system, particularly toll-like receptors 4 (TLR4) signaling pathway dysfunction plays a pivotal part in the pathogenesis of IBD. TLR4 signaling is involved both in the pathogenesis and in the efficacy of treatment of IBD. There are some medicinal products and herbal medicines, which their role in the treatment of IBD through modulation of TLR4 signaling has been implicated. The purpose of this review article is to summarize those medicinal products and herbal medicines.

Pattern Recognition Receptor Signaling and Innate Responses to Influenza A Viruses in the Mallard Duck, Compared to Humans and Chickens

Mallard ducks are a natural host and reservoir of avian Influenza A viruses. While most influenza strains can replicate in mallards, the virus typically does not cause substantial disease in this host. Mallards are often resistant to disease caused by highly pathogenic avian influenza viruses, while the same strains can cause severe infection in humans, chickens, and even other species of ducks, resulting in systemic spread of the virus and even death. The differences in influenza detection and antiviral effectors responsible for limiting damage in the mallards are largely unknown. Domestic mallards have an early and robust innate response to infection that seems to limit replication and clear highly pathogenic strains. The regulation and timing of the response to influenza also seems to circumvent damage done by a prolonged or dysregulated immune response. Rapid initiation of innate immune responses depends on viral recognition by pattern recognition receptors (PRRs) expressed in tissues where the virus replicates. RIG-like receptors (RLRs), Toll-like receptors (TLRs), and Nod-like receptors (NLRs) are all important influenza sensors in mammals during infection. Ducks utilize many of the same PRRs to detect influenza, namely RIG-I, TLR7, and TLR3 and their downstream adaptors. Ducks also express many of the same signal transduction proteins including TBK1, TRIF, and TRAF3. Some antiviral effectors expressed downstream of these signaling pathways inhibit influenza replication in ducks. In this review, we summarize the recent advances in our understanding of influenza recognition and response through duck PRRs and their adaptors. We compare basal tissue expression and regulation of these signaling components in birds, to better understand what contributes to influenza resistance in the duck.

Targeting Host Innate and Adaptive Immunity to Achieve the Functional Cure of Chronic Hepatitis B

Despite the availability of an effective preventive vaccine for hepatitis B virus (HBV) for over 38 years, chronic HBV (CHB) infection remains a global health burden with around 257 million patients. The ideal treatment goal for CHB infection would be to achieve complete cure; however, current therapies such as peg-interferon and nucleos(t)ide analogs are unable to achieve the functional cure, the newly set target for HBV chronic infection. Considering the fact functional cure has been accepted as an endpoint in the treatment of chronic hepatitis B by scientific committee, the development of alternative therapeutic strategies is urgently needed to functionally cure CHB infection. A promising target for future therapeutic strategies is immune modulation to restore dysfunctional HBV-specific immunity. In this review, we provide an overview of the progress in alternative therapeutic strategies, including immune-based therapeutic approaches that enhance host innate and adaptive immunity to achieve and increase the functional cure from CHB infection.

Toll-like receptor bioactivity in endothelial progenitor cells

Cardiovascular disease is the main cause of death globally that can be mitigated by the modulation of angiogenesis. To achieve this goal, the application of endothelial progenitor cells and other stem cell types is useful. Following the onset of cardiovascular disease and pro-inflammatory conditions as seen during bacterial sepsis, endothelial progenitor cells enter systemic circulation in response to multiple cytokines and activation of various intracellular mechanisms. The critical role of Toll-like receptors has been previously identified in the dynamics of various cell types, in particular, immune cells. To our knowledge, there are a few experiments related to the role of Toll-like receptors in endothelial progenitor cell activity. Emerging data point of endothelial progenitor cells and other stem cells having the potential to express Toll-like receptors to control different activities such as multipotentiality and dynamics of growth. In this review article, we aim to collect data related to the role of Toll-like receptors in endothelial progenitor cells bioactivity and angiogenic potential.

Innate Immune Evasion by Human Respiratory RNA Viruses

The impact of respiratory virus infections on the health of children and adults can be very significant. Yet, in contrast to most other childhood infections as well as other viral and bacterial diseases, prophylactic vaccines or effective antiviral treatments against viral respiratory infections are either still not available, or provide only limited protection. Given the widespread prevalence, a general lack of natural sterilizing immunity, and/or high morbidity and lethality rates of diseases caused by influenza, respiratory syncytial virus, coronaviruses, and rhinoviruses, this difficult situation is a genuine societal challenge. A thorough understanding of the virus-host interactions during these respiratory infections will most probably be pivotal to ultimately meet these challenges. This review attempts to provide a comparative overview of the knowledge about an important part of the interaction between respiratory viruses and their host: the arms race between host innate immunity and viral innate immune evasion. Many, if not all, viruses, including the respiratory viruses listed above, suppress innate immune responses to gain a window of opportunity for efficient virus replication and setting-up of the infection. The consequences for the host's immune response are that it is often incomplete, delayed or diminished, or displays overly strong induction (after the delay) that may cause tissue damage. The affected innate immune response also impacts subsequent adaptive responses, and therefore viral innate immune evasion often undermines fully protective immunity. In this review, innate immune responses relevant for respiratory viruses with an RNA genome will briefly be summarized, and viral innate immune evasion based on shielding viral RNA species away from cellular innate immune sensors will be discussed from different angles. Subsequently, viral enzymatic activities that suppress innate immune responses will be discussed, including activities causing host shut-off and manipulation of stress granule formation. Furthermore, viral protease-mediated immune evasion and viral manipulation of the ubiquitin system will be addressed. Finally, perspectives for use of the reviewed knowledge for the development of novel antiviral strategies will be sketched.

What can we learn about influenza infection and vaccination from transcriptomics?

Transcriptomics studies the set of RNA transcripts produced by the genome using high-throughput sequencing and bioinformatics. This growing field has revolutionized our understanding of host-pathogen interactions, revealing new insights into the host response to influenza infection and vaccination. Studies using transcriptomics have identified a unique immunosignature for influenza discernable from other bacterial and viral pathogens, key transcriptional factors that discriminate early from late, mild versus severe, and symptomatic versus asymptomatic infection. Recent studies evaluating the host response to influenza vaccines have revealed key differences in live versus inactivated influenza vaccines, identified early transcriptional signatures that predict hemagglutinin antibody production following vaccination, increased our understanding of how adjuvants enhance the immune response to influenza vaccine antigens, and demonstrate biologic variability in the response to vaccination due to host factors. These studies demonstrate the potential for influenza transcriptomics to be applied to clinical care, understanding the mechanisms of infection, and informing vaccine development.

Chandipura virus changes cellular miRNome in human microglial cells

Chandipura virus (CHPV) is a neurotropic virus, known to cause encephalitis in humans. The microRNAs (miRNA/miR) play an important role in the pathogenesis of viral infection. The present study is focused on the role of miRNAs during CHPV (strain 1653514) infection in human microglial cells. The deep sequencing of CHPV-infected human microglial cells identified a total of 12 differentially expressed miRNA (DEMs). To elucidate the role of DEMs, the target gene prediction, Gene Ontology term (GO Term), pathway enrichment analysis, and miRNA-messenger RNA (mRNA) interaction network analysis was performed. The GO terms and pathway enrichment analysis provided 146 enriched genes; which were involved in interferon response, cytokine and chemokine signaling. Further, the WGCNA (weighted gene coexpression network analysis) of the enriched genes were discretely categorized into three modules (blue, brown, and turquoise). The hub genes in the blue module may correlate to CHPV induced neuroinflammation. Altogether, the miRNA-mRNA interaction network and WGCNA study revealed the following pairs, hsa-miR-542-3p and FAF1, hsa-miR-92a-1-5p and MYD88, and hsa-miR-3187-3p and TNFRSF21, which may contribute to neuroinflammation during CHPV infection in human microglial cells.

Therapeutically Active RIG-I Agonist Induces Immunogenic Tumor Cell Killing in Breast Cancers

Cancer immunotherapies that remove checkpoint restraints on adaptive immunity are gaining clinical momentum but have not achieved widespread success in breast cancers, a tumor type considered poorly immunogenic and which harbors a decreased presence of tumor-infiltrating lymphocytes. Approaches that activate innate immunity in breast cancer cells and the tumor microenvironment are of increasing interest, based on their ability to induce immunogenic tumor cell death, type I IFNs, and lymphocyte-recruiting chemokines. In agreement with reports in other cancers, we observe loss, downregulation, or mutation of the innate viral nucleotide sensor retinoic acid-inducible gene I (RIG-I/DDX58) in only 1% of clinical breast cancers, suggesting potentially widespread applicability for therapeutic RIG-I agonists that activate innate immunity. This was tested using an engineered RIG-I agonist in a breast cancer cell panel representing each of three major clinical breast cancer subtypes. Treatment with RIG-I agonist resulted in upregulation and mitochondrial localization of RIG-I and activation of proinflammatory transcription factors STAT1 and NF-κB. RIG-I agonist triggered the extrinsic apoptosis pathway and pyroptosis, a highly immunogenic form of cell death in breast cancer cells. RIG-I agonist also induced expression of lymphocyte-recruiting chemokines and type I IFN, confirming that cell death and cytokine modulation occur in a tumor cell-intrinsic manner. Importantly, RIG-I activation in breast tumors increased tumor lymphocytes and decreased tumor growth and metastasis. Overall, these findings demonstrate successful therapeutic delivery of a synthetic RIG-I agonist to induce tumor cell killing and to modulate the tumor microenvironment in vivo Significance: These findings describe the first in vivo delivery of RIG-I mimetics to tumors, demonstrating a potent immunogenic and therapeutic effect in the context of otherwise poorly immunogenic breast cancers. Cancer Res; 78(21); 6183-95. ©2018 AACR.

Programmed Cell Death in the Pathogenesis of Influenza

Influenza is a respiratory disease induced by infection by the influenza virus, which is a member of Orthomyxoviridae family. This infectious disease has serious impacts on public health systems and results in considerable mortality and economic costs throughout the world. Based on several experimental studies, massive host immune reaction is associated with the disease severity of influenza. Programmed cell death is typically induced during virus infection as a consequence of host immune reaction to limit virus spread by eliminating niches for virus propagation without causing inflammation. However, in some viral infectious diseases, such as influenza, in the process of immune reaction, aberrant induction of programmed cell death disturbs the maintenance of organ function. Current reports show that there are different types of programmed cell death that vary in terms of molecular mechanisms and/or associations with inflammation. In addition, these novel types of programmed cell death are associated with pathogenesis rather than suppressing virus propagation in the disease course. Here, we review our current understanding of mechanisms of programmed cell death in the pathogenesis of influenza.

Harnessing RIG-I and intrinsic immunity in the tumor microenvironment for therapeutic cancer treatment

Cancer immunotherapies that remove checkpoint restraints on adaptive immunity are gaining clinical momentum. Approaches aimed at intrinsic cellular immunity in the tumor microenvironment are less understood, but are of intense interest, based on their ability to induce tumor cell apoptosis while orchestrating innate and adaptive immune responses against tumor antigens. The intrinsic immune response is initiated by ancient, highly conserved intracellular proteins that detect viral infection. For example, the RIG-I-like receptors (RLRs), a family of related RNA helicases, detect viral oligonucleotide patterns of certain RNA viruses. RLR activation induces immunogenic cell death of virally infected cells, accompanied by increased inflammatory cytokine production, antigen presentation, and antigen-directed immunity against virus antigens. Approaches aimed at non-infectious RIG-I activation in cancers are being tested as a treatment option, with the goal of inducing immunogenic tumor cell death, stimulating production of pro-inflammatory cytokines, enhancing tumor neoantigen presentation, and potently increasing cytotoxic activity of tumor infiltrating lymphocytes. These studies are finding success in several pre-clinical models, and are entering early phases of clinical trial. Here, we review pre-clinical studies of RLR agonists, including the successes and challenges currently faced RLR agonists on the path to clinical translation.

Integrated Lung and Tracheal mRNA-Seq and miRNA-Seq Analysis of Dogs with an Avian-Like H5N1 Canine Influenza Virus Infection

Avian-like H5N1 canine influenza virus (CIV) causes severe respiratory infections in dogs. However, the mechanism underlying H5N1 CIV infection in dogs is unknown. The present study aimed to identify differentially expressed miRNAs and mRNAs in the lungs and trachea in H5N1 CIV-infected dogs through a next-generation sequencing-based method. Eighteen 40-day-old beagles were inoculated intranasally with CIV, A/canine/01/Guangdong/2013 (H5N1) at a tissue culture infectious dose 50 (TCID₅₀) of 10⁶, and lung and tracheal tissues were harvested at 3 and 7 d post-inoculation. The tissues were processed for miRNA and mRNA analysis. By means of miRNA-gene expression integrative negative analysis, we found miRNA–mRNA pairs. Lung and trachea tissues showed 138 and 135 negative miRNA–mRNA pairs, respectively. One hundred and twenty negative miRNA–mRNA pairs were found between the different tissues. In particular, pathways including the influenza A pathway, chemokine signaling pathways, and the PI3K-Akt signaling pathway were significantly enriched in all groups in responses to virus infection. Furthermore, dysregulation of miRNA and mRNA expression was observed in the respiratory tract of H5N1 CIV-infected dogs and notably, TLR4 (miR-146), NF-κB (miR-34c) and CCL5 (miR-335), CCL10 (miR-8908-5p), and GNGT2 (miR-122) were found to play important roles in regulating pathways that resist virus infection. To our knowledge, the present study is the first to analyze miRNA and mRNA expression in H5N1 CIV-infected dogs; furthermore, the present findings provide insights into the molecular mechanisms underlying influenza virus infection.

TANK-Binding Kinase 1 (TBK1) Isoforms Negatively Regulate Type I Interferon Induction by Inhibiting TBK1-IRF3 Interaction and IRF3 Phosphorylation

TANK-binding kinase 1 (TBK1) is an important serine/threonine-protein kinase that mediates phosphorylation and nuclear translocation of IRF3, which contributes to induction of type I interferons (IFNs) in the innate antiviral response. In mammals, TBK1 spliced isoform negatively regulates the virus-triggered IFN-β signaling pathway by disrupting the interaction between retinoic acid-inducible gene I (RIG-I) and mitochondria antiviral-signaling protein (MAVS). However, it is still unclear whether alternative splicing patterns and the function of TBK1 isoform(s) exist in teleost fish. In this study, we identify two alternatively spliced isoforms of TBK1 from zebrafish, termed TBK1_tv1 and TBK1_tv2. Both TBK1_tv1 and TBK1_tv2 contain an incomplete STKc_TBK1 domain. Moreover, the UBL_TBK1_like domain is also missing for TBK1_tv2. TBK1_tv1 and TBK1_tv2 are expressed in zebrafish larvae. Overexpression of TBK1_tv1 and TBK1_tv2 inhibits RIG-I-, MAVS-, TBK1-, and IRF3-mediated activation of IFN promoters in response to spring viremia of carp virus infection. Also, TBK1_tv1 and TBK1_tv2 inhibit expression of IFNs and IFN-stimulated genes induced by MAVS and TBK1. Mechanistically, TBK1_tv1 and TBK1_tv2 competitively associate with TBK1 and IRF3 to disrupt the formation of a functional TBK1-IRF3 complex, impeding the phosphorylation of IRF3 mediated by TBK1. Collectively, these results demonstrate that TBK1 spliced isoforms are dominant negative regulators in the RIG-I/MAVS/TBK1/IRF3 antiviral pathway by targeting the functional TBK1-IRF3 complex formation. Identification and functional characterization of piscine TBK1 spliced isoforms may contribute to understanding the role of TBK1 expression in innate antiviral response.