Pattern recognition receptors and the innate immune response to viral infection

Role of alternative splicing in fish immunity

Alternative splicing serves as a pivotal source of complexity in the transcriptome and proteome, selectively connecting various coding elements to generate a diverse array of mRNAs. This process encodes multiple proteins with either similar or distinct functions, contributing significantly to the intricacies of cellular processes. The role of alternative splicing in mammalian immunity has been well studied. Remarkably, the immune system of fish shares substantial similarities with that of humans, and alternative splicing also emerges as a key player in the immune processes of fish. In this review, we offer an overview of alternative splicing and its associated functions in the immune processes of fish, and summarize the research progress on alternative splicing in the fish immunity. Furthermore, we review the impact of alternative splicing on the fish immune system's response to external stimuli. Finally, we present our perspectives on future directions in this field. Our aim is to provide valuable insights for the future investigations into the role of alternative splicing in immunity.

High-risk HPV oncoproteins E6 and E7 and their interplay with the innate immune response: Uncovering mechanisms of immune evasion and therapeutic prospects

Human papillomaviruses (HPVs) are double-stranded DNA (dsDNA) tumor viruses causally associated with 5% of human cancers, comprising both anogenital and upper aerodigestive tract carcinomas. Despite the availability of prophylactic vaccines, HPVs continue to pose a significant global health challenge, primarily due to inadequate vaccine access and coverage. These viruses can establish persistent infections by evading both the intrinsic defenses of infected tissues and the extrinsic defenses provided by professional innate immune cells. Crucial for their evasion strategies is their unique intraepithelial life cycle, which effectively shields them from host detection. Thus, strategies aimed at reactivating the innate immune response within infected or transformed epithelial cells, particularly through the production of type I interferons (IFNs) and lymphocyte-recruiting chemokines, are considered viable solutions to counteract the adverse effects of persistent infections by these oncogenic viruses. This review focuses on the complex interplay between the high-risk HPV oncoproteins E6 and E7 and the innate immune response in epithelial cells and HPV-associated cancers. In particular, it details the molecular mechanisms by which E6 and E7 modulate the innate immune response, highlighting significant progress in our comprehension of these processes. It also examines forward-looking strategies that exploit the innate immune system to ameliorate existing anticancer therapies, thereby providing crucial insights into future therapeutic developments.

Analysis of Selected Toll-like Receptors in the Pathogenesis and Advancement of Non-Small-Cell Lung Cancer

(1) Background: Non-small-cell lung cancer (NSCLC) represents a significant global health challenge, contributing to numerous cancer deaths. Despite advances in diagnostics and therapy, identifying reliable biomarkers for prognosis and therapeutic stratification remains difficult. Toll-like receptors (TLRs), crucial for innate immunity, now show potential as contributors to cancer development and progression. This study aims to investigate the role of TLR expression as potential biomarkers in the development and progression of NSCLC. (2) Materials and Methods: The study was conducted on 89 patients diagnosed with NSCLC and 40 healthy volunteers, for whom the prevalence of TLR2, TLR3, TLR4, TLR7, TLR8, and TLR9 was assessed on selected subpopulations of T and B lymphocytes in the peripheral blood of recruited patients along with the assessment of their serum concentration. (3) Result: Our study showed several significant changes in NSCLC patients at the beginning of the study. This resulted in a 5-year follow-up of changes in selected TLRs in recruited patients. Due to the high mortality rate of NSCLC patients, only 16 patients survived the 5 years. (4) Conclusions: The results suggest that TLRs may constitute real biomarker molecules that may be used for future prognostic purposes in NSCLC. However, further validation through prospective clinical and functional studies is necessary to confirm their clinical utility. These conclusions may lead to better risk stratification and tailored interventions, benefiting NSCLC patients and bringing medicine closer to precision.

The Dynamic Relationship between Dengue Virus and the Human Cutaneous Innate Immune Response

Dengue virus (DENV) is a continuing global threat that puts half of the world's population at risk for infection. This mosquito-transmitted virus is endemic in over 100 countries. When a mosquito takes a bloodmeal, virus is deposited into the epidermal and dermal layers of human skin, infecting a variety of permissive cells, including keratinocytes, Langerhans cells, macrophages, dermal dendritic cells, fibroblasts, and mast cells. In response to infection, the skin deploys an array of defense mechanisms to inhibit viral replication and prevent dissemination. Antimicrobial peptides, pattern recognition receptors, and cytokines induce a signaling cascade to increase transcription and translation of pro-inflammatory and antiviral genes. Paradoxically, this inflammatory environment recruits skin-resident mononuclear cells that become infected and migrate out of the skin, spreading virus throughout the host. The details of the viral-host interactions in the cutaneous microenvironment remain unclear, partly due to the limited body of research focusing on DENV in human skin. This review will summarize the functional role of human skin, the cutaneous innate immune response to DENV, the contribution of the arthropod vector, and the models used to study DENV interactions in the cutaneous environment.

Revitalizing antitumor immunity: Leveraging nucleic acid sensors as therapeutic targets

Nucleic acid sensors play a critical role in recognizing and responding to pathogenic nucleic acids as danger signals. Upon activation, these sensors initiate downstream signaling cascades that lead to the production and release of pro-inflammatory cytokines, chemokines, and type I interferons. These immune mediators orchestrate diverse effector responses, including the activation of immune cells and the modulation of the tumor microenvironment. However, careful consideration must be given to balancing the activation of nucleic acid sensors to avoid unwanted autoimmune or inflammatory responses. In this review, we provide an overview of nucleic acid sensors and their role in combating cancer through the perception of various aberrant nucleic acids and activation of the immune system. We discuss the connections between different programmed cell death modes and nucleic acid sensors. Finally, we outline the development of nucleic acid sensor agonists, highlighting how their potential as therapeutic targets opens up new avenues for cancer immunotherapy.

Roles of airway and intestinal epithelia in responding to pathogens and maintaining tissue homeostasis

Epithelial cells form a resilient barrier and orchestrate defensive and reparative mechanisms to maintain tissue stability. This review focuses on gut and airway epithelia, which are positioned where the body interfaces with the outside world. We review the many signaling pathways and mechanisms by which epithelial cells at the interface respond to invading pathogens to mount an innate immune response and initiate adaptive immunity and communicate with other cells, including resident microbiota, to heal damaged tissue and maintain homeostasis. We compare and contrast how airway and gut epithelial cells detect pathogens, release antimicrobial effectors, collaborate with macrophages, Tregs and epithelial stem cells to mount an immune response and orchestrate tissue repair. We also describe advanced research models for studying epithelial communication and behaviors during inflammation, tissue injury and disease.

Innate immune response against vector-borne bunyavirus infection and viral countermeasures

Bunyaviruses are a large group of important viral pathogens that cause significant diseases in humans and animals worldwide. Bunyaviruses are enveloped, single-stranded, negative-sense RNA viruses that infect a wide range of hosts. Upon entry into host cells, the components of viruses are recognized by host innate immune system, leading to the activation of downstream signaling cascades to induce interferons (IFNs) and other proinflammatory cytokines. IFNs bind to their receptors and upregulate the expression of hundreds of interferon-stimulated genes (ISGs). Many ISGs have antiviral activities and confer an antiviral state to host cells. For efficient replication and spread, viruses have evolved different strategies to antagonize IFN-mediated restriction. Here, we discuss recent advances in our understanding of the interactions between bunyaviruses and host innate immune response.

MST1/2 exerts a pivotal role in inducing neuroinflammation and Coxsackievirus-A10 replication by interacting with innate immunity

Coxsackievirus-A10 (CV-A10), responsible for the hand, foot and mouth disease (HFMD) pandemic, could cause serious central nervous system (CNS) complications. The underlying molecular basis of CV-A10 and host interactions inducing neuropathogenesis is still unclear. The Hippo signaling pathway, historically known for a dominator of organ development and homeostasis, has recently been implicated as an immune regulator. However, its role in host defense against CV-A10 has not been investigated. Herein, it was found that CV-A10 proliferated in HMC3 cells and promoted the release of inflammatory cytokines. Moreover, pattern recognition receptors (PRRs)-mediated pathways, including TLR3-TRIF-TRAF3-TBK1-NF-κB axis, RIG-I/MDA5-MAVS-TRAF3-TBK1-NF-κB axis and TLR7-MyD88-IRAK1/IRAK4-TRAF6-TAK1-NF-κB axis, were examined to be elevated under CV-A10 infection. Meanwhile, it was further uncovered that Hippo signaling pathway was inhibited in HMC3 cells with CV-A10 infection. Previous studies have been reported that there exist complex relations between innate immune and Hippo signaling pathway. Then, plasmids of knockdown and overexpression of MST1/2 were transfected into HMC3 cells. Our results showed that MST1/2 suppressed the levels of inflammatory cytokines via interacting with TBK1 and IRAK1, and also enhanced virus production via restricting IRF3 and IFN-β expressions. Overall, these data obviously pointed out that CV-A10 accelerated the formation of neuroinflammation by the effect of the Hippo pathway on the PRRs-mediated pathway, which delineates a negative immunoregulatory role for MST1/2 in CV-A10 infection and the potential for this pathway to be pharmacologically targeted to treat CV-A10.

Virus-Induced Epilepsy vs. Epilepsy Patients Acquiring Viral Infection: Unravelling the Complex Relationship for Precision Treatment

The intricate relationship between viruses and epilepsy involves a bidirectional interaction. Certain viruses can induce epilepsy by infecting the brain, leading to inflammation, damage, or abnormal electrical activity. Conversely, epilepsy patients may be more susceptible to viral infections due to factors, such as compromised immune systems, anticonvulsant drugs, or surgical interventions. Neuroinflammation, a common factor in both scenarios, exhibits onset, duration, intensity, and consequence variations. It can modulate epileptogenesis, increase seizure susceptibility, and impact anticonvulsant drug pharmacokinetics, immune system function, and brain physiology. Viral infections significantly impact the clinical management of epilepsy patients, necessitating a multidisciplinary approach encompassing diagnosis, prevention, and treatment of both conditions. We delved into the dual dynamics of viruses inducing epilepsy and epilepsy patients acquiring viruses, examining the unique features of each case. For virus-induced epilepsy, we specify virus types, elucidate mechanisms of epilepsy induction, emphasize neuroinflammation's impact, and analyze its effects on anticonvulsant drug pharmacokinetics. Conversely, in epilepsy patients acquiring viruses, we detail the acquired virus, its interaction with existing epilepsy, neuroinflammation effects, and changes in anticonvulsant drug pharmacokinetics. Understanding this interplay advances precision therapies for epilepsy during viral infections, providing mechanistic insights, identifying biomarkers and therapeutic targets, and supporting optimized dosing regimens. However, further studies are crucial to validate tools, discover new biomarkers and therapeutic targets, and evaluate targeted therapy safety and efficacy in diverse epilepsy and viral infection scenarios.

Interferons in Viral Infections

Interferons (IFNs) are cytokines that inhibit viral replication in host cells by triggering innate immune responses through the transcriptional induction of various IFN-stimulated genes (ISGs) [...].

Endosomal escape: A bottleneck for LNP-mediated therapeutics

Lipid nanoparticles (LNPs) have recently emerged as a powerful and versatile clinically approved platform for nucleic acid delivery, specifically for mRNA vaccines. A major bottleneck in the field is the release of mRNA-LNPs from the endosomal pathways into the cytosol of cells where they can execute their encoded functions. The data regarding the mechanism of these endosomal escape processes are limited and contradicting. Despite extensive research, there is no consensus regarding the compartment of escape, the cause of the inefficient escape and are currently lacking a robust method to detect the escape. Here, we review the currently known mechanisms of endosomal escape and the available methods to study this process. We critically discuss the limitations and challenges of these methods and the possibilities to overcome these challenges. We propose that the development of currently lacking robust, quantitative high-throughput techniques to study endosomal escape is timely and essential. A better understanding of this process will enable better RNA-LNP designs with improved efficiency to unlock new therapeutic modalities.

A Synthetic Multivalent Lipopeptide Derived from Pam3CSK4 with Irreversible Influenza Inhibition and Immuno-Stimulating Effects

The activation of the host adaptive immune system is crucial for eliminating viruses. However, influenza infection often suppresses the innate immune response that precedes adaptive immunity, and the adaptive immune responses are typically delayed. Dendritic cells, serving as professional antigen-presenting cells, have a vital role in initiating the adaptive immune response. In this study, an immuno-stimulating antiviral system (ISAS) is introduced, which is composed of the immuno-stimulating adjuvant lipopeptide Pam3CSK4 that acts as a scaffold onto which it is covalently bound 3 to 4 influenza-inhibiting peptides. The multivalent display of peptides on the scaffold leads to a potent inhibition against H1N1 (EC50  = 20 nM). Importantly, the resulting lipopeptide, Pam3FDA, shows an irreversible inhibition mechanism. The chemical modification of peptides on the scaffold maintains Pam3CSK4's ability to stimulate dendritic cell maturation, thereby rendering Pam3FDA a unique antiviral. This is attributed to its immune activation capability, which also acts in synergy to expedite viral elimination.

Amphiprion clarkii DDX41 modulates fish immune responses: Characterization by expression profiling, antiviral assay, and macrophage polarization analysis

DDX41, a member of the DEAD-box helicase family, serves as a vital cytosolic DNA sensor and plays a pivotal role in controlling the activation of type I interferon responses in mammals. However, the functional aspects of fish DDX41 remain relatively unexplored. In this study, we identified and characterized the DDX41 gene in Amphiprion clarkii transcriptomes and designated the gene as AcDDX41. The complete open reading frame of AcDDX41 encoded a putative protein comprising 617 amino acids. Notably, the predicted AcDDX41 protein shared several structural features that are conserved in DDX41, including DEXDc, HELICc, and zinc finger domains, as well as conserved sequence "Asp-Glu-Ala-Asp (D-E-A-D)." AcDDX41 exhibited the highest sequence homology (99.68 % similarity) with DDX41 from Acanthochromis polyacanthus. Phylogenetic analysis revealed that DDX41s from fish formed a branch distinct from that in other animals. All investigated tissues were shown to express AcDDX41 constitutively, with blood showing the highest expression levels, followed by the brain. Furthermore, AcDDX41 expression was significantly induced upon stimulation with poly I:C, lipopolysaccharide, and Vibrio harveyi, indicating its responsiveness to immune stimuli. We confirmed the antiviral function of AcDDX41 by analyzing gene expression and viral replication during viral hemorrhagic septicemia virus infection. Additionally, using a luciferase reporter assay, we validated the ability of AcDDX41 to activate the NF-κB signaling pathway upon stimulation with poly I:C. Finally, AcDDX41 influenced cytokine gene expression and played a regulatory role in macrophage M1 polarization in RAW 264.7 cells. Collectively, these results highlight the significance of AcDDX41 as an immune-related gene that contributes substantially to antiviral defense and regulation of NF-κB activity.

Transcription of endogenous retroviruses in senescent cells contributes to the accumulation of double-stranded RNAs that trigger an anti-viral response that reinforces senescence

An important epigenetic switch marks the onset and maintenance of senescence. This allows transcription of the genetic programs that arrest the cell cycle and alter the microenvironment. Transcription of endogenous retroviruses (ERVs) is also a consequence of this epigenetic switch. In this manuscript, we have identified a group of ERVs that are epigenetically silenced in proliferating cells but are upregulated during replicative senescence or during various forms of oncogene-induced senescence, by RAS and Akt, or after HDAC4 depletion. In a HDAC4 model of senescence, removal of the repressive histone mark H3K27me3 is the plausible mechanism that allows the transcription of intergenic ERVs during senescence. We have shown that ERVs contribute to the accumulation of dsRNAs in senescence, which can initiate the antiviral response via the IFIH1-MAVS signaling pathway and thus contribute to the maintenance of senescence. This pathway, and MAVS in particular, plays an active role in shaping the microenvironment and maintaining growth arrest, two essential features of the senescence program.

Immunological mechanisms of the nucleocapsid protein in COVID-19

The emergence of corona virus disease 2019 (COVID-19), resulting from Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has left an indelible mark on a global scale, causing countless infections and fatalities. This investigation delves into the role of the SARS-CoV-2 nucleocapsid (N) protein within the HEK293 cells, shedding light on its influence over apoptosis, interferon signaling, and cytokines production. The N gene was amplified, inserted into the pAdTrack-CMV vector, and then transfected to the HEK293 cells. Changes in the expression of IRF3, IRF7, IFN-β, BAK, BAX, and BCL-2 genes were evaluated. The levels of proinflammatory cytokines of IL-6, IL-12, IL-1β, and TNF-α were also determined. The N protein exhibited an anti-apoptotic effect by modulating critical genes associated with apoptosis, including BAK, BAX, and BCL-2. This effect potentially prolonged the survival of infected cells. The N protein also played a role in immune evasion by suppressing the interferon pathway, evidenced by the downregulation of essential interferon regulatory factors of IRF3 and IRF7, and IFN-β expression. The N protein expression led to a substantial increase in the production of proinflammatory cytokines of IL-6, IL-12, IL-1β, and TNF-α. The N protein emerged as a versatile factor and was exerted over apoptosis, interferon signaling, and cytokine production. These findings carry potential implications for the development of targeted therapies to combat COVID-19 and mitigate its global health impact.

The potential of IFN-λ, IL-32γ, IL-6, and IL-22 as safeguards against human viruses: a systematic review and a meta-analysis

Many studies have investigated the antiviral activity of cytokines, including interleukin-6 (IL-6), interleukin-22 (IL-22), interleukin-32 gamma (IL-32γ), and interferon-lambda (IFN-λ) in diverse populations. This study aims to evaluate the role of these cytokines in inhibition of various human and animal viruses when administered exogenously. A comprehensive meta-analysis and systematic review were conducted on all the relevant studies from three databases. Standard mean differences (SMDs) of overall viral inhibition were used to generate the difference in the antiviral efficacy of these cytokines between control and experimental groups. A total of 4,618 abstracts for IL-6, 3,517 abstracts for IL-22, 2,160 abstracts for IL-32γ, and 1,026 abstracts for IFN-λ were identified, and 7, 4, 8, and 35 studies were included, respectively, for each cytokine. IFN-λ (SMD = 0.9540; 95% CI: 0.69-0.22) and IL-32γ (SMD = 0.459; 95% CI: 0.02-0.90) showed the highest influence followed by IL-6 (SMD = 0.456; CI: -0.04-0.95) and IL-22 (SMD = 0.244; 95% CI: -0.33-0.81). None of the cytokines represented heterogeneity (tau² > 0), but only IFN-λ indicated the funnel plot asymmetry (p = 0.0097). Results also indicated that IFN-λ and IL-32γ are more potent antivirals than IL-6 and IL-22. The collective findings of this study emphasize that exogenously administered pro-inflammatory cytokines, specifically IFN-λ and IL-32, exhibit a significant antiviral activity, thereby underscoring them as potent antiviral agents. Nonetheless, additional research is required to ascertain their clinical utility and potential for integration into combinatorial therapeutic regimens against viral infections.

Ovarian sex steroid and epithelial control of immune responses in the uterus and oviduct: human and animal models†

The female reproductive tract (FRT), including the uterus and oviduct (Fallopian tube), is responsible for maintaining an optimal microenvironment for reproductive processes, such as gamete activation and transportation, sperm capacitation, fertilization, and early embryonic and fetal development. The mucosal surface of the FRT may be exposed to pathogens and sexually transmitted microorganisms due to the opening of the cervix during mating. Pathogens and endotoxins may also reach the oviduct through the peritoneal fluid. To maintain an optimum reproductive environment while recognizing and killing pathogenic bacterial and viral agents, the oviduct and uterus should be equipped with an efficient and rigorously controlled immune system. Ovarian sex steroids can affect epithelial cells and underlying stromal cells, which have been shown to mediate innate and adaptive immune responses. This, in turn, protects against potential infections while maintaining an optimal milieu for reproductive events, highlighting the homeostatic involvement of ovarian sex steroids and reproductive epithelial cells. This article will discuss how ovarian sex steroids affect the immune reactions elicited by the epithelial cells of the non-pregnant uterus and oviduct in the bovine, murine, and human species. Finally, we propose that there are regional and species-specific differences in the immune responses in FRT.

TREM-2: friend or foe in infectious diseases?

The triggering receptor expressed on myeloid cells-2 (TREM-2) is an immune receptor expressed on immune and non-immune cells, more frequently investigated in neurodegenerative disorders and considered a marker for microglia activation. In infectious diseases, the receptor was initially believed to be an anti-inflammatory molecule, opposing the inflammation triggered by TREM-1. Currently, TREM-2 is associated with different aspects in response to infectious stimuli, including the induction of bacterial phagocytosis and clearance, containment of exacerbated pro-inflammatory responses, induction of M2 differentiation and activation of Th1 lymphocytes, besides of neurological damage after viral infection. Here, we present and discuss results published in the last two decades regarding the expression, activation and functions of TREM-2 during the course of bacterial, viral, fungal and parasitic infections. A surprisingly plasticity was observed regarding the roles of the receptor in the aforementioned contexts, which largely varied according to the cell/organ and pathogen type, besides influencing disease outcome. Therefore, our review aimed to critically overview the role of TREM-2 in infectious diseases, highlighting its potential to be used as a clinical biomarker or therapeutic target.

Advances in Poultry Vaccines: Leveraging Biotechnology for Improving Vaccine Development, Stability, and Delivery

With the rapidly increasing demand for poultry products and the current challenges facing the poultry industry, the application of biotechnology to enhance poultry production has gained growing significance. Biotechnology encompasses all forms of technology that can be harnessed to improve poultry health and production efficiency. Notably, biotechnology-based approaches have fueled rapid advances in biological research, including (a) genetic manipulation in poultry breeding to improve the growth and egg production traits and disease resistance, (b) rapid identification of infectious agents using DNA-based approaches, (c) inclusion of natural and synthetic feed additives to poultry diets to enhance their nutritional value and maximize feed utilization by birds, and (d) production of biological products such as vaccines and various types of immunostimulants to increase the defensive activity of the immune system against pathogenic infection. Indeed, managing both existing and newly emerging infectious diseases presents a challenge for poultry production. However, recent strides in vaccine technology are demonstrating significant promise for disease prevention and control. This review focuses on the evolving applications of biotechnology aimed at enhancing vaccine immunogenicity, efficacy, stability, and delivery.

Epigenetic Control of Innate Immunity: Consequences of Acute Respiratory Virus Infection

Infections caused by acute respiratory viruses induce a systemic innate immune response, which can be measured by the increased levels of expression of inflammatory genes in immune cells. There is growing evidence that these acute viral infections, alongside transient transcriptomic responses, induce epigenetic remodeling as part of the immune response, such as DNA methylation and histone modifications, which might persist after the infection is cleared. In this article, we first review the primary mechanisms of epigenetic remodeling in the context of innate immunity and inflammation, which are crucial for the regulation of the immune response to viral infections. Next, we delve into the existing knowledge concerning the impact of respiratory virus infections on the epigenome, focusing on Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), Influenza A Virus (IAV), and Respiratory Syncytial Virus (RSV). Finally, we offer perspectives on the potential consequences of virus-induced epigenetic remodeling and open questions in the field that are currently under investigation.

Immunomodulatory properties of bacteriophage derived dsRNA of different size and their use as anticancer vaccine adjuvants

Dendritic cell (DC) based immunotherapy is one of the strategies to combat cancer invoking a patient's immune system. This form of anticancer immunotherapy employs adjuvants to enhance the immune response, triggering mechanisms of innate immunity and thus increase immunotherapeutic efficiency. A conventional adjuvant for DCs maturation during production of anticancer vaccines is bacterial LPS. Nevertheless, synthetic dsRNAs were also shown to stimulate different receptors on innate immune cells and to activate immune responses through induction of cytokines via toll-like receptors. In our study we investigated the potential of Larifan as dsRNA of natural origin to stimulate maturation of DCs with proinflammatory (possible antitumoral) activity and to compare these immunostimulatory properties between Larifan's fractions with different molecular lengths. To explore the suitability of this product for therapy, it is necessary to study the properties of its different fractions and compare them to standard adjuvants. We investigated the effect of Larifan's fractions on immune system stimulation in vivo by monitoring the survival time of tumor-bearing mice. Murine DCs produced in vitro using Larifan and its fractions together with tumor antigens during production were also characterized. All Larifan fractions resulted in inducing high expression of immunogenic markers CD40, CD80, CD86, CCR7, MHC II and lower secretion of the immunosuppressive cytokine IL-10, compared to the maturation with LPS in mDCs. The lowest expression of tolerogenic gene Ido1 and highest expression of the immunogenic genes Clec7a, Tnf, Icosl, Il12rb2, Cd209a were characteristic to the unfractionated dsRNA and short fraction FR15. In the mouse model the best overall survival rate was observed in mice treated with medium-length FR9 and FR15. We can state that both Larifan and its fractions were superior to LPS as vaccine adjuvants in stimulating phenotype and functional activity of mature DCs. DCs maturation using these factors induces a valuable anticancer immune response.

HHV-6B detection and host gene expression implicate HHV-6B as pulmonary pathogen after hematopoietic cell transplant

Limited understanding of the immunopathogenesis of human herpesvirus 6B (HHV-6B) has prevented its acceptance as a pulmonary pathogen after hematopoietic cell transplant (HCT). In this prospective multicenter study of patients undergoing bronchoalveolar lavage (BAL) for pneumonia after allogeneic HCT, we test blood and BAL fluid (BALF) for HHV-6B DNA and mRNA transcripts associated with lytic infection and perform RNA-seq on paired blood. Among 116 participants, HHV-6B DNA is detected in 37% of BALs, 49% of which also have HHV-6B mRNA detection. We establish HHV-6B DNA viral load thresholds in BALF that are highly predictive of HHV-6B mRNA detection and associated with increased risk for overall mortality and death from respiratory failure. Participants with HHV-6B DNA in BALF exhibit distinct host gene expression signatures, notable for enriched interferon signaling pathways in participants clinically diagnosed with idiopathic pneumonia. These data implicate HHV-6B as a pulmonary pathogen after allogeneic HCT.

The Contribution of Microglia and Brain-Infiltrating Macrophages to the Pathogenesis of Neuroinflammatory and Neurodegenerative Diseases during TMEV Infection of the Central Nervous System

The infection of the central nervous system (CNS) with neurotropic viruses induces neuroinflammation and is associated with the development of neuroinflammatory and neurodegenerative diseases, including multiple sclerosis and epilepsy. The activation of the innate and adaptive immune response, including microglial, macrophages, and T and B cells, while required for efficient viral control within the CNS, is also associated with neuropathology. Under healthy conditions, resident microglia play a pivotal role in maintaining CNS homeostasis. However, during pathological events, such as CNS viral infection, microglia become reactive, and immune cells from the periphery infiltrate into the brain, disrupting CNS homeostasis and contributing to disease development. Theiler's murine encephalomyelitis virus (TMEV), a neurotropic picornavirus, is used in two distinct mouse models: TMEV-induced demyelination disease (TMEV-IDD) and TMEV-induced seizures, representing mouse models of multiple sclerosis and epilepsy, respectively. These murine models have contributed substantially to our understanding of the pathophysiology of MS and seizures/epilepsy following viral infection, serving as critical tools for identifying pharmacological targetable pathways to modulate disease development. This review aims to discuss the host-pathogen interaction during a neurotropic picornavirus infection and to shed light on our current understanding of the multifaceted roles played by microglia and macrophages in the context of these two complexes viral-induced disease.

Understanding the Neurotrophic Virus Mechanisms and Their Potential Effect on Systemic Lupus Erythematosus Development

Central nervous system (CNS) pathologies are a public health concern, with viral infections one of their principal causes. These viruses are known as neurotropic pathogens, characterized by their ability to infiltrate the CNS and thus interact with various cell populations, inducing several diseases. The immune response elicited by neurotropic viruses in the CNS is commanded mainly by microglia, which, together with other local cells, can secrete inflammatory cytokines to fight the infection. The most relevant neurotropic viruses are adenovirus (AdV), cytomegalovirus (CMV), enterovirus (EV), Epstein-Barr Virus (EBV), herpes simplex virus type 1 (HSV-1), and herpes simplex virus type 2 (HSV-2), lymphocytic choriomeningitis virus (LCMV), and the newly discovered SARS-CoV-2. Several studies have associated a viral infection with systemic lupus erythematosus (SLE) and neuropsychiatric lupus (NPSLE) manifestations. This article will review the knowledge about viral infections, CNS pathologies, and the immune response against them. Also, it allows us to understand the relevance of the different viral proteins in developing neuronal pathologies, SLE and NPSLE.

A Review of miRNA Regulation in Japanese Encephalitis (JEV) Virus Infection

Japanese encephalitis (JE) is a mosquito-borne disease that causes neuronal damage and inflammation of microglia, and in severe cases, it can be fatal. JE infection can resist cellular immune responses and survive in host cells. Japanese encephalitis virus (JEV) infects macrophages and peripheral blood lymphocytes. In addition to regulating biological signaling pathways, microRNAs in cells also influence virus-host interactions. Under certain circumstances, viruses can change microRNA production. These changes affect the replication and spread of the virus. Host miRNAs can contain viral pathogenicity by downregulating the antiviral immune response pathways. Simultaneous profiling of miRNA and messenger RNA (mRNA) could help us detect pathogenic factors, and dual RNA detection is possible. This work highlights important miRNAs involved in human JE infection. In this study, we have shown the important miRNAs that play significant roles in JEV infection. We found that during JEV infection, miRNA-155, miRNA-29b, miRNA-15b, miRNA-146a, miRNA-125b-5p, miRNA-30la, miRNA-19b-3p, and miRNA-124, cause upregulation of human genes whereas miRNA-432, miRNA-370, miRNA- 33a-5p, and miRNA-466d-3p are responsible for downregulation of human genes respectively. Further, these miRNAs are also responsible for the inflammatory effects. Although several other miRNAs critical to the JEV life cycle are yet unknown, there is currently no evidence for the role of miRNAs in persistence.

TBK1 upregulates the interferon response against virus by the TBK1-IRF3/7 axis in yellow catfish (Pelteobagrus fulvidraco)

Yellow catfish (Pelteobagrus fulvidraco) is an important economic species of freshwater fish, widely distributed in China. Recently, viral diseases of yellow catfish have been identified in Chian (Hubei province), arising more attention to the viral immunity in P. fulvidraco. Tumor necrosis factor (TNF) receptor-associated factor NF-κB activator (TANK)-binding kinase 1 (TBK1) plays an essential role in IFN production and innate antiviral immunity. In the present study, we characterized the P. fulvidraco TBK1 (PfTBK1) and reported its function in interferon response. The full-length open reading frame (ORF) is 2184 bp encoding a protein with 727 amino acids, which is composed of four conserved domains, including KD, ULD, CCD1, and CCD2, similar to TBK1 in other species. Pftbk1 was widely expressed in all detected tissues by qPCR and was not inducible by the spring viremia of carp virus (SVCV), a single-strand RNA virus. In addition, the cellular distribution indicated that PfTBK1 was only located in the cytoplasm. Moreover, PfTBK1 induced strong IFN promoter activities through the Jak-stat pathway, and PfTBK1 interacted with and significantly phosphorylated IFN regulatory factor 3/7 (IRF3/7) in P. fulvidraco, promoting the nuclear translocation of pfIRF3 and PfIRF7, and PfTBK1 upregulated IFN response by PfTBK1-PfIRF3/7 axis. Above all, PfTBK1 triggered IFN response and strongly inhibited the replication of SVCV in EPC cells through induction of IFN downstream IFN-stimulated genes (ISGs). Summarily, this work reveals that PfTBK1 plays a positive regulatory role in IFN induction through the TBK1-IRF3/7 axis, laying a foundation for further exploring the molecular mechanism of the antiviral process in P. fulvidraco.

Classification of patients with COVID-19 by blood RNA endotype: a prospective cohort study

IMPORTANCE

In this study, whole-blood RNAs (prolactin and toll-like receptor 3) involved in the prognosis of patients with COVID-19 were identified. The RNA endotypes classified by these important RNAs highlight the possibility of stratifying the COVID-19 patient population and the need for targeted therapy based on these phenotypes.

Neddylation Regulation of Immune Responses

Neddylation plays a vital role in post-translational modification, intricately shaping the regulation of diverse biological processes, including those related to cellular immune responses. In fact, neddylation exerts control over both innate and adaptive immune systems via various mechanisms. Specifically, neddylation influences the function and survival of innate immune cells, activation of pattern recognition receptors and GMP-AMP synthase-stimulator of interferon genes pathways, as well as the release of various cytokines in innate immune reactions. Moreover, neddylation also governs the function and survival of antigen-presenting cells, which are crucial for initiating adaptive immune reactions. In addition, neddylation regulates T cell activation, proliferation, differentiation, survival, and their effector functions, thereby ensuring an appropriate adaptive immune response. In this review, we summarize the most recent findings in these aspects and delve into the connection between dysregulated neddylation events and immunological disorders, especially inflammatory diseases. Lastly, we propose future directions and potential treatments for these diseases by targeting neddylation.

A novel protein encoded by circVPS13D attenuates antiviral innate immunity by targeting MAVS in teleost fish

IMPORTANCE

The expression of circVPS13D was upregulated with SCRV invasion, which proved that circVPS13D was involved in the regulation of the antiviral immune response. Our study revealed that the existence of circVPS13D promoted the replication of SCRV. Functionally, circVPS13D negatively regulates the antiviral responses of fish. Mechanistically, we confirmed that circVPS13D inhibited RLRs antiviral signaling pathway via the encoded protein VPS13D-170aa by targeting MAVS. Our study provided novel insights into the roles of protein-coding circRNAs and supported VPS13D-170aa as a negative regulator in the antiviral immune responses of teleost fish.

Toll-like receptor 7 and RIG-I-like receptors expression in peripheral blood mononuclear cells of naïve patients with hepatitis C

BACKGROUND

The proper function of Pattern Recognition Receptors (PRRs) as a part of the host immune system can eliminate numerous pathogens from the body. However, some viruses can manipulate PRRs to escape the innate immune system. As there is controversy in the activation of PRRs in patients infected with HCV, we decided to evaluate the gene expression changes of PRRs in HCV cases compared to the healthy control.

METHODS

In this study, the relative expression of Toll-like receptor 7, RIG-I, and MAD-5 in peripheral mononuclear blood cells of twenty HCV patients and twenty healthy controls of the same gender and age were analyzed by quantitative Real-time PCR.

RESULTS

Our results showed that the expression of RIG-I and MAD-5 significantly increased in HCV-infected samples compared to the controls (P value:0.01; P value:0.05), while the expression of TLR7 was similar between the case and the control group (P value:0.1).

CONCLUSION

It seems in suppressing HCV, RIG-I and MAD-5 receptors are likely to be more activated than TRL7 in HCV patients. The lack of TLR7 gene expression might reflect the defect of the host in the stimulation of the innate immune system through the TLR7 pathway.

NLRP3 Inflammasome Involvement in Heart, Liver, and Lung Diseases-A Lesson from Cytokine Storm Syndrome

Inflammation and inflammasomes have been proposed as important regulators of the host-microorganism interaction, playing a key role in morbidity and mortality due to the coronavirus disease 2019 (COVID-19) in subjects with chronic conditions and compromised immune system. The inflammasome consists of a multiprotein complex that finely regulates the activation of caspase-1 and the production and secretion of potent pro-inflammatory cytokines such as IL-1β and IL-18. The pyrin containing NOD (nucleotide-binding oligomerization domain) like receptor (NLRP) is a family of intracellular receptors, sensing patterns associated to pathogens or danger signals and NLRP3 inflammasome is the most deeply analyzed for its involvement in the innate and adaptive immune system as well as its contribution to several autoinflammatory and autoimmune diseases. It is highly expressed in leukocytes and up-regulated in sentinel cells upon inflammatory stimuli. NLRP3 expression has also been reported in B and T lymphocytes, in epithelial cells of oral and genital mucosa, in specific parenchymal cells as cardiomyocytes, and keratinocytes, and chondrocytes. It is well known that a dysregulated activation of the inflammasome is involved in the pathogenesis of different disorders that share the common red line of inflammation in their pathogenetic fingerprint. Here, we review the potential roles of the NLRP3 inflammasome in cardiovascular events, liver damage, pulmonary diseases, and in that wide range of systemic inflammatory syndromes named as a cytokine storm.

Interferon-stimulated gene TDRD7 interacts with AMPK and inhibits its activation to suppress viral replication and pathogenesis

IMPORTANCE

Virus infection triggers induction of interferon (IFN)-stimulated genes (ISGs), which ironically inhibit viruses themselves. We identified Tudor domain-containing 7 (TDRD7) as a novel antiviral ISG, which inhibits viral replication by interfering with autophagy pathway. Here, we present a molecular basis for autophagy inhibitory function of TDRD7. TDRD7 interacted with adenosine monophosphate (AMP)-activated protein kinase (AMPK), the kinase that initiates autophagy, to inhibit its activation. We identified domains required for the interaction; deleting AMPK-interacting domain blocked antiAMPK and antiviral activities of TDRD7. We used primary cells and mice to evaluate the TDRD7-AMPK antiviral pathway. TDRD7-deficient primary mouse cells exhibited enhanced AMPK activation and viral replication. Finally, TDRD7 knockout mice showed increased susceptibility to respiratory virus infection. Therefore, our study revealed a new antiviral pathway of IFN and its contribution to host response. Our results have therapeutic potential; a TDRD7-derived peptide may be an effective AMPK inhibitor with application as antiviral agent.

Aedes albopictus salivary adenosine deaminase is an immunomodulatory factor facilitating dengue virus replication

The Asian tiger mosquito, Aedes albopictus, is an important vector for the transmission of arboviruses such as dengue virus (DENV). Adenosine deaminase (ADA) is a well-characterized metabolic enzyme involved in facilitating blood feeding and (or) arbovirus transmission in some hematophagous insect species. We previously reported the immunologic function of ADA by investigating its effect on mast cell activation and the interaction with mast cell tryptase and chymase. The 2-D gel electrophoresis and mass spectrometry analysis in the current study revealed that ADA is present and upregulated following mosquito blood feeding, as confirmed by qRT-PCR and western blot. In addition, the recombinant ADA efficiently converted adenosine to inosine. Challenging the Raw264.7 and THP-1 cells with recombinant ADA resulted in the upregulation of IL-1β, IL-6, TNF-α, CCL2, IFN-β, and ISG15. The current study further identified recombinant ADA as a positive regulator in NF-κB signaling targeting TAK1. It was also found that recombinant Ae. albopictus ADA facilitates the replication of DENV-2. Compared with cells infected by DENV-2 alone, the co-incubation of recombinant ADA with DENV-2 substantially increased IL-1β, IL-6, TNF-α, and CCL2 gene transcripts in Raw264.7 and THP-1 cells. However, the expression of IFN-β and ISG15 were markedly downregulated in Raw264.7 cells but upregulated in THP-1 cells. These findings suggest that the immunomodulatory protein, Ae. albopictus ADA is involved in mosquito blood feeding and may modulate DENV transmission via macrophage or monocyte-driven immune response.

African Swine Fever Virus pF778R Attenuates Type I Interferon Response by Impeding STAT1 Nuclear Translocation

African swine fever virus (ASFV) is an extensive and intricate double-stranded DNA virus with approximately 100% lethality in domestic swine. There is no effective vaccine to combat this virus, and this has led to substantial economic losses in the swine industry. ASFV encodes various proteins that impede interferon-based immune defenses in the host by employing diverse mechanisms. However, the roles of most of these proteins remain unknown. Therefore, understanding the immune evasion mechanisms employed by ASFV may facilitate the development of effective measures against the virus. In this study, we discovered a negative regulation of the type I interferon (IFN) response by the ASFV ribonuclease reductase large subunit pF778R. This novel type Ⅰ IFN response antagonist significantly inhibits IFN-α-induced interferon-stimulated response element promoter activation, precludes the upregulation of various interferon-stimulated genes, and prevents STAT1 nuclear translocation. Mechanistically, pF778R did not affect the protein levels of crucial molecules in the JAK/STAT signaling pathway or engage in direct interactions. However, pF778R expression impedes type I IFN responses mediated by the JAK/STAT signaling pathway. Further investigations revealed that pF778R did not interfere with STAT1 phosphorylation or dimerization, but it inhibited IFN signaling by weakening the nuclear accumulation of activated STAT1. The critical role of the ASFV protein pF778R in evading IFN-I-mediated innate immunity highlights a unique mode of ASFV evasion and provides insights into the pathogenic mechanism of the virus.

Rift Valley Fever Virus-Infection, Pathogenesis and Host Immune Responses

Rift Valley Fever Virus is a mosquito-borne phlebovirus causing febrile or haemorrhagic illness in ruminants and humans. The virus can prevent the induction of the antiviral interferon response through its NSs proteins. Mutations in the NSs gene may allow the induction of innate proinflammatory immune responses and lead to attenuation of the virus. Upon infection, virus-specific antibodies and T cells are induced that may afford protection against subsequent infections. Thus, all arms of the adaptive immune system contribute to prevention of disease progression. These findings will aid the design of vaccines using the currently available platforms. Vaccine candidates have shown promise in safety and efficacy trials in susceptible animal species and these may contribute to the control of RVFV infections and prevention of disease progression in humans and ruminants.

The Battle for Survival: The Role of RNA Non-Canonical Tails in the Virus-Host Interaction

Terminal nucleotidyltransferases (TENTs) could generate a 'mixed tail' or 'U-rich tail' consisting of different nucleotides at the 3' end of RNA by non-templated nucleotide addition to protect or degrade cellular messenger RNA. Recently, there has been increasing evidence that the decoration of virus RNA terminus with a mixed tail or U-rich tail is a critical way to affect viral RNA stability in virus-infected cells. This paper first briefly introduces the cellular function of the TENT family and non-canonical tails, then comprehensively reviews their roles in virus invasion and antiviral immunity, as well as the significance of the TENT family in antiviral therapy. This review will contribute to understanding the role and mechanism of non-canonical RNA tailing in survival competition between the virus and host.

Cholesterol-autoxidation metabolites in host defense against infectious diseases

Cholesterol plays essential roles in biological processes, including cell membrane stability and myelin formation. Cholesterol can be metabolized to oxysterols by enzymatic or nonenzymatic ways. Nonenzymatic cholesterol metabolites, also called cholesterol-autoxidation metabolites, are formed dependent on the oxidation of reactive oxygen species (ROS) such as OH• or reactive nitrogen species, such as ONOO- . Cholesterol-autoxidation metabolites are abundantly produced in diseases such as inflammatory bowel disease and atherosclerosis, which are associated with oxidative stress. Recent studies have shown that cholesterol-autoxidation metabolites can further regulate the immune system. Here, we review the literature and summarize how cholesterol-autoxidation metabolites, such as 25-hydroxycholesterol (25-OHC), 7α/β-OHC, and 7-ketocholesterol, deal with the occurrence and development of infectious diseases through pattern recognition receptors, inflammasomes, ROS production, nuclear receptors, G-protein-coupled receptor 183, and lipid availability. In addition, we include the research regarding the roles of these metabolites in COVID-19 infection and discuss our viewpoints on the future research directions.

The development and function of human monocyte-derived dendritic cells regulated by metabolic reprogramming

Human monocyte-derived dendritic cells (moDCs) that develop from monocytes play a key role in innate inflammatory responses as well as T cell priming. Steady-state moDCs regulate immunogenicity and tolerogenicity by changing metabolic patterns to participate in the body's immune response. Increased glycolytic metabolism after danger signal induction may strengthen moDC immunogenicity, whereas high levels of mitochondrial oxidative phosphorylation were associated with the immaturity and tolerogenicity of moDCs. In this review, we discuss what is currently known about differential metabolic reprogramming of human moDC development and distinct functional properties.

SARS-CoV-2 ORF6 protein does not antagonize interferon signaling in respiratory epithelial Calu-3 cells during infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused millions of deaths, posing a substantial threat to global public health. Viruses evolve different strategies to antagonize or evade host immune responses. While ectopic expression of SARS-CoV-2 accessory protein ORF6 blocks interferon (IFN) production and downstream IFN signaling, the role of ORF6 in IFN signaling during bona fide viral infection of respiratory cells is unclear. By comparing wild-type (WT) and ORF6-deleted (ΔORF6) SARS-CoV-2 infection and IFN signaling in respiratory cells, we found that ΔORF6 SARS-CoV-2 replicates more efficiently than WT virus and, thus, stimulates more robust immune signaling. Loss of ORF6 does not alter innate signaling in infected cells: both WT and ΔORF6 virus induce delayed IFN responses only in bystander cells. Moreover, expression of ORF6 in the context of SARS-CoV-2 infection has no effect on Sendai virus-stimulated IFN induction: robust translocation of IRF3 is observed in both SARS-CoV-2 infected and bystander cells. Furthermore, IFN pretreatment potently blocks WT and ΔORF6 virus replication similarly, and both viruses fail to suppress the induction of interferon-stimulated genes (ISGs) upon IFN-β treatment. However, upon treatment with IFN-β, only bystander cells induce STAT1 translocation during infection with WT virus, whereas ΔORF6 virus-infected cells now show translocation. This suggests that under conditions of high IFN activation, ORF6 can attenuate STAT1 activation. These data provide evidence that ORF6 is not sufficient to antagonize IFN production or IFN signaling in SARS-CoV-2-infected respiratory cells but may impact the efficacy of therapeutics that stimulate innate immune pathways. IMPORTANCE Previous studies identified several SARS-CoV-2 proteins, including ORF6, that antagonize host innate immune responses in the context of overexpression of viral proteins in non-respiratory cells. We set out to determine the role of ORF6 in IFN responses during SARS-CoV-2 infection of respiratory cells. Using a deletion strain, we observed no reduction of infection and no difference in evasion of IFN signaling, with responses limited to bystander cells. Moreover, stimulation of Sendai virus-induced IFN production or IFN-β-stimulated ISG expression was comparable between SARS-CoV-2 virus and SARS-CoV-2 lacking ORF6 virus, suggesting that ORF6 is not sufficient to counteract IFN induction or IFN signaling during viral infection.

Interferons-Implications in the Immune Response to Respiratory Viruses

Interferons (IFN) are an assemblage of signaling proteins made and released by various host cells in response to stimuli, including viruses. Respiratory syncytial virus (RSV), influenza virus, and SARS-CoV-2 are major causes of respiratory disease that induce or antagonize IFN responses depending on various factors. In this review, the role and function of type I, II, and III IFN responses to respiratory virus infections are considered. In addition, the role of the viral proteins in modifying anti-viral immunity is noted, as are the specific IFN responses that underly the correlates of immunity and protection from disease.

Cell-targeted vaccines: implications for adaptive immunity

Recent advancements in immunology and chemistry have facilitated advancements in targeted vaccine technology. Targeting specific cell types, tissue locations, or receptors can allow for modulation of the adaptive immune response to vaccines. This review provides an overview of cellular targets of vaccines, suggests methods of targeting and downstream effects on immune responses, and summarizes general trends in the literature. Understanding the relationships between vaccine targets and subsequent adaptive immune responses is critical for effective vaccine design. This knowledge could facilitate design of more effective, disease-specialized vaccines.

Multiple Porcine Innate Immune Signaling Pathways Are Involved in the Anti-PEDV Response

Porcine epidemic diarrhea virus (PEDV) has caused great damage to the global pig industry. Innate immunity plays a significant role in resisting viral infection; however, the exact role of innate immunity in the anti-PEDV response has not been fully elucidated. In this study, we observed that various porcine innate immune signaling adaptors are involved in anti-PEDV (AJ1102-like strain) activity in transfected Vero cells. Among these, TRIF and MAVS showed the strongest anti-PEDV activity. The endogenous TRIF, MAVS, and STING were selected for further examination of anti-PEDV activity. Agonist stimulation experiments showed that TRIF, MAVS, and STING signaling all have obvious anti-PEDV activity. The siRNA knockdown assay showed that TRIF, MAVS, and STING are also all involved in anti-PEDV response, and their remarkable effects on PEDV replication were confirmed in TRIF-/-, MAVS-/- and STING-/- Vero cells via the CRISPR approach. For further verification, the anti-PEDV activity of TRIF, MAVS, and STING could be reproduced in porcine IPEC-DQ cells treated with siRNAs. In summary, this study reveals that multiple pattern-recognition receptor (PRR) signaling pathways of porcine innate immunity play an important role in the anti-PEDV infection, providing new and useful antiviral knowledge for prevention and control of PEDV spreading.

Know your neighbors: microbial recognition at the intestinal barrier and its implications for gut homeostasis and inflammatory bowel disease

Intestinal epithelial cells (IECs) perform several physiological and metabolic functions at the epithelial barrier. IECs also play an important role in defining the overall immune functions at the mucosal region. Pattern recognition receptors (PRRs) on the cell surface and in other cellular compartments enable them to sense the presence of microbes and microbial products in the intestinal lumen. IECs are thus at the crossroads of mediating a bidirectional interaction between the microbial population and the immune cells present at the intestinal mucosa. This communication between the microbial population, the IECs and the underlying immune cells has a profound impact on the overall health of the host. In this review, we focus on the various PRRs present in different cellular compartments of IECs and discuss the recent developments in the understanding of their role in microbial recognition. Microbial recognition and signaling at the epithelial barrier have implications in the maintenance of intestinal homeostasis, epithelial barrier function, maintenance of commensals, and the overall tolerogenic function of PRRs in the gut mucosa. We also highlight the role of an aberrant microbial sensing at the epithelial barrier in the pathogenesis of inflammatory bowel disease (IBD) and the development of colorectal cancer.

Immunization against Zika by entrapping live virus in a subcutaneous self-adjuvanting hydrogel

The threat of new viral outbreaks has heightened the need for ready-to-use vaccines that are safe and effective. Here we show that a subcutaneous vaccine consisting of live Zika virus electrostatically entrapped in a self-adjuvanting hydrogel recruited immune cells at the injection site and provided mice with effective protection against a lethal viral challenge. The hydrogel prevented the escape of the viral particles and upregulated pattern recognition receptors that activated innate antiviral immunity. The local inflammatory niche facilitated the engulfment of the virus by immune cells infiltrating the hydrogel, the processing and cross-presentation of antigens and the expansion of germinal centre B cells and induced robust antigen-specific adaptive responses and immune memory. Inflammatory immune niches entrapping live viruses may facilitate the rapid development of safe and efficacious vaccines.

The host transcriptome change involved in the inhibitory effect of exogenous interferon-γ on Getah virus replication

Introduction

Getah virus (GETV) has become a growing potential threat to the global livestock industry and public health. However, little is known about the viral pathogenesis and immune escape mechanisms, leading to ineffective control measures.

Methods

In this study, the antiviral activity of exogenous interferons (IFNs) was assessed by using western blotting (WB), real-time quantitative PCR (RT-qPCR) and indirect immunofluorescence assay (IFA). The comparative transcriptomics among mock- and GETV-infected (MOI = 0.1) ST cells with or without IFN-γ was performed by RNA-seq, and then the transcriptome profiling of GETV-infected ST cells and key pathways and putative factors involved in inhibitory effect of IFN-γ on GETV replication were analyzed by bioinformatics methods and RT-qPCR.

Results

The results showed that treatment with IFN-γ could suppress GETV replication, and the inhibitory effect lasted for at least 48 h, while the exogenous IFN-α/ω and IFN-λ3 treatments failed to inhibit the viral infection and early replication in vitro. Furthermore, the blueprint of virus-host interaction was plotted by RNA-seq and RT-qPCR, showing systemic activation of inflammatory, apoptotic, and antiviral pathways in response to GETV infection, indicating viral hijacking and inhibition of innate host immunity such as IFN-I/III responses. Last and most importantly, activation of the JAK-STAT signaling pathway and complement and coagulation cascades may be a primary driver for IFN-γ-mediated inhibition of GETV replication.

Discussion

These findings revealed that GETV possessed the capability of viral immune escape and indicated that IFN-γ aided in the prevention and control of GETV, implying the potential molecular mechanism of suppression of GETV by IFN-γ, all of which warrant emphasis or further clarification.

β-amyloid binds to microglia Dectin-1 to induce inflammatory response in the pathogenesis of Alzheimer's disease

Microglia-mediated neuroinflammation is closely related to the development of Alzheimer's disease (AD). In the early stages of the inflammation response, pattern recognition receptors (PRRs) play a key role in clearing damaged cells and defending against infection by recognizing endogenous and exogenous ligands. However, the regulation of pathogenic microglial activation and its role in AD pathology remains poorly understood. Here we showed that a pattern recognition receptor called Dectin-1, expressed on microglia, mediates the pro-inflammatory responses of beta-amyloid (Aβ). Knockout of Dectin-1 reduced Aβ1-42 (Aβ42)-induced microglial activation, inflammatory responses, and synaptic and cognitive deficits in Aβ42-infused AD mice. Similar results were obtained in the BV2 cell model. Mechanistically, we showed that Aβ42 could directly bind to Dectin-1, causing Dectin-1 homodimerization and activating downstream spleen tyrosine kinase (Syk)/nuclear factor-κB (NF-κB) signaling pathway to induce the expression of inflammatory factors and, in turn, AD pathology. These results suggest the important role of microglia Dectin-1 as a new direct receptor for Aβ42 in microglial activation and AD pathology and provide a potential therapeutic strategy for neuroinflammation in AD.

TLR9 and STING agonists cooperatively boost the immune response to SARS-CoV-2 RBD vaccine through an increased germinal center B cell response and reshaped T helper responses

Vaccines are a powerful medical intervention for preventing epidemic diseases. Efficient inactivated or protein vaccines typically rely on an effective adjuvant to elicit an immune response and boost vaccine activity. In this study, we investigated the adjuvant activities of combinations of Toll-like receptor 9 (TLR9) and stimulator of interferon genes (STING) agonists in a SARS-CoV-2 receptor binding domain protein vaccine. Adjuvants formulated with a TLR9 agonist, CpG-2722, with various cyclic dinucleotides (CDNs) that are STING agonists increased germinal center B cell response and elicited humoral immune responses in immunized mice. An adjuvant containing CpG-2722 and 2'3'-c-di-AM(PS)2 effectively boosted the immune response to both intramuscularly and intranasally administrated vaccines. Vaccines adjuvanted with CpG-2722 or 2'3'-c-di-AM(PS)2 alone were capable of inducing an immune response, but a cooperative adjuvant effect was observed when both were combined. CpG-2722 induced antigen-dependent T helper (Th)1 and Th17 responses, while 2'3'-c-di-AM(PS)2 induced a Th2 response. The combination of CpG-2722 and 2'3'-c-di-AM(PS)2 generated a distinct antigen-dependent Th response profile characterized by higher Th1 and Th17, but lower Th2 responses. In dendritic cells, CpG-2722 and 2'3'-c-di-AM(PS)2 showed a cooperative effect on inducing expression of molecules critical for T cell activation. CpG-2722 and 2'3'-c-di-AM(PS)2 have distinct cytokine inducing profiles in different cell populations. The combination of these two agonists enhanced the expression of cytokines for Th1 and Th17 responses and suppressed the expression of cytokines for Th2 response in these cells. Thus, the antigen-dependent Th responses observed in the animals immunized with different vaccines were shaped by the antigen-independent cytokine-inducing profiles of their adjuvant. The expanded targeting cell populations, the increased germinal center B cell response, and reshaped T helper responses are the molecular bases for the cooperative adjuvant effect of the combination of TLR9 and STING agonists.

Mechanisms of Innate Immune Sensing of HTLV-1 and Viral Immune Evasion

Human T lymphotropic virus-1 (HTLV-1) was the first identified oncoretrovirus, which infects and establishes a persistent infection in approximately 10-20 million people worldwide. Although only ~5% of infected individuals develop pathologies such as adult T-cell leukemia/lymphoma (ATLL) or a neuroinflammatory disorder termed HTLV-1-asssociated myelopathy/tropical spastic paraparesis (HAM/TSP), asymptomatic carriers are more susceptible to opportunistic infections. Furthermore, ATLL patients are severely immunosuppressed and prone to other malignancies and other infections. The HTLV-1 replication cycle provides ligands, mainly nucleic acids (RNA, RNA/DNA intermediates, ssDNA intermediates, and dsDNA), that are sensed by different pattern recognition receptors (PRRs) to trigger immune responses. However, the mechanisms of innate immune detection and immune responses to HTLV-1 infection are not well understood. In this review, we highlight the functional roles of different immune sensors in recognizing HTLV-1 infection in multiple cell types and the antiviral roles of host restriction factors in limiting persistent infection of HTLV-1. We also provide a comprehensive overview of intricate strategies employed by HTLV-1 to subvert the host innate immune response that may contribute to the development of HTLV-1-associated diseases. A more detailed understanding of HTLV-1-host pathogen interactions may inform novel strategies for HTLV-1 antivirals, vaccines, and treatments for ATLL or HAM/TSP.

Amphibian myelopoiesis

Macrophage-lineage cells are indispensable to immunity and physiology of all vertebrates. Amongst these, amphibians represent a key stage in vertebrate evolution and are facing decimating population declines and extinctions, in large part due to emerging infectious agents. While recent studies indicate that macrophages and related innate immune cells are critically involved during these infections, much remains unknown regarding the ontogeny and functional differentiation of these cell types in amphibians. Accordingly, in this review we coalesce what has been established to date about amphibian blood cell development (hematopoiesis), the development of key amphibian innate immune cells (myelopoiesis) and the differentiation of amphibian macrophage subsets (monopoiesis). We explore the current understanding of designated sites of larval and adult hematopoiesis across distinct amphibian species and consider what mechanisms may lend to these species-specific adaptations. We discern the identified molecular mechanisms governing the functional differentiation of disparate amphibian (chiefly Xenopus laevis) macrophage subsets and describe what is known about the roles of these subsets during amphibian infections with intracellular pathogens. Macrophage lineage cells are at the heart of so many vertebrate physiological processes. Thus, garnering greater understanding of the mechanisms responsible for the ontogeny and functionality of these cells in amphibians will lend to a more comprehensive view of vertebrate evolution.