Exosomal Interferon-Induced Transmembrane Protein 2 Transmitted to Dendritic Cells Inhibits Interferon Alpha Pathway Activation and Blocks Anti-Hepatitis B Virus Efficacy of Exogenous Interferon Alpha

Unveiling the immunoregulatory role of interferon-induced transmembrane protein 2 through the JAK/STAT3/PDL1 pathway in gastric cancer

Programmed cell death ligand 1 (PDL1) has been implicated in immune evasion in various tumor types. The objective of this investigation was to assess the correlation between metastasis-associated interferon-induced transmembrane protein 2 (IFITM2) and PDL1, and explore their impact on tumor immunity in gastric cancer (GC). The expression of IFITM2 and PDL1 in human GC tissues was initially evaluated using The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases, as well as immunohistochemistry (IHC). Subsequently, the relationship between IFITM2 and PDL1 was analyzed through Real-time quantitative PCR (RT-qPCR) and western blotting after cell transfection and inhibitor treatment in vitro. The role of IFITM2 and PDL1 in immune killing was further elucidated in both in vitro and in vivo settings. Our study revealed frequent overexpression of IFITM2 and PDL1 in GC. Notably, IFITM2 expression was significantly associated with lymphatic metastasis, clinical stage, and poor survival. Moreover, a positive correlation between PDL1 expression and IFITM2 expression in GC was identified. The activation of tumor-derived IFITM2 was found to enhance PDL1 expression via the JAK/STAT3 pathway in human GC cells (MKN28 and MKN45), leading to apoptosis of Jurkat T cells. Furthermore, IFITM2 induced PDL1 expression in a xenograft mouse model of GC. Based on our findings, we propose that IFITM2 modulates PDL1 expression and tumor immunity through the JAK/STAT3 pathway in GC cells, highlighting the potential of IFITM2 as a therapeutic target for GC immunotherapy.

The Yin and the Yang of extracellular vesicles during viral infections

The role of extracellular vesicles (EVs) as key players in the intercellular communication is a subject of growing interest in all areas of physiology and pathophysiology, and the field of viral infections is no exception to the rule. In this review, we focus on the current state of knowledge and remaining gaps regarding the entanglement of viruses and EVs during infections. These two entities share many similarities, mainly due to their intricated biogenesis pathways that are in constant interaction. EVs can promote the replication and dissemination of viruses within the organism, through the dysregulation of their cargo and the modulation of the innate and adaptive immune response that occurs upon infection, but they can also promote the mitigation of viral infections. Here, we examine how viruses hijack EV biogenesis pathways and describe the consequences of dysregulated EV secretion during viral infections, beneficial or not for viruses, revealing the duality of their possible effects.

Exosomes target HBV-host interactions to remodel the hepatic immune microenvironment

Chronic hepatitis B poses a significant global burden, modulating immune cells, leading to chronic inflammation and long-term damage. Due to its hepatotropism, the hepatitis B virus (HBV) cannot infect other cells. The mechanisms underlying the intercellular communication among different liver cells in HBV-infected individuals and the immune microenvironment imbalance remain elusive. Exosomes, as important intercellular communication and cargo transportation tools between HBV-infected hepatocytes and immune cells, have been shown to assist in HBV cargo transportation and regulate the immune microenvironment. However, the role of exosomes in hepatitis B has only gradually received attention in recent years. Minimal literature has systematically elaborated on the role of exosomes in reshaping the immune microenvironment of the liver. This review unfolds sequentially based on the biological processes of exosomes: exosomes' biogenesis, release, transport, uptake by recipient cells, and their impact on recipient cells. We delineate how HBV influences the biogenesis of exosomes, utilizing exosomal covert transmission, and reshapes the hepatic immune microenvironment. And based on the characteristics and functions of exosomes, potential applications of exosomes in hepatitis B are summarized and predicted.

S-palmitoylation regulates innate immune signaling pathways: molecular mechanisms and targeted therapies

S-palmitoylation is a reversible posttranslational lipid modification that targets cysteine residues of proteins and plays critical roles in regulating the biological processes of substrate proteins. The innate immune system serves as the first line of defense against pathogenic invaders and participates in the maintenance of tissue homeostasis. Emerging studies have uncovered the functions of S-palmitoylation in modulating innate immune responses. In this review, we focus on the reversible palmitoylation of innate immune signaling proteins, with particular emphasis on its roles in the regulation of protein localization, protein stability, and protein-protein interactions. We also highlight the potential and challenge of developing therapies that target S-palmitoylation or de-palmitoylation for various diseases.

Bmp4 in Zebrafish Enhances Antiviral Innate Immunity through p38 MAPK (Mitogen-Activated Protein Kinases) Pathway

Bone morphogenetic proteins (BMPs) are a group of structurally and functionally related signaling molecules that comprise a subfamily, belonging to the TGF-β superfamily. Most BMPs play roles in the regulation of embryonic development, stem cell differentiation, tumor growth and some cardiovascular and cerebrovascular diseases. Although evidence is emerging for the antiviral immunity of a few BMPs, more BMPs are needed to determine whether this function is universal. Here, we identified the zebrafish bmp4 ortholog, whose expression is up-regulated through challenge with grass carp reovirus (GCRV) or its mimic poly(I:C). The overexpression of bmp4 in epithelioma papulosum cyprini (EPC) cells significantly decreased the viral titer of GCRV-infected cells. Moreover, compared to wild-type zebrafish, viral load and mortality were significantly increased in both larvae and adults of bmp4-/- mutant zebrafish infected with GCRV virus. We further demonstrated that Bmp4 promotes the phosphorylation of Tbk1 and Irf3 through the p38 MAPK pathway, thereby inducing the production of type I IFNs in response to virus infection. These data suggest that Bmp4 plays an important role in the host defense against virus infection. Our study expands the understanding of BMP protein functions and opens up new targets for the control of viral infection.

Intercellular communication within the virus microenvironment affects the susceptibility of cells to secondary viral infections

Communication between infected cells and cells in the surrounding tissue is a determinant of viral spread. However, it remains unclear how cells in close or distant proximity to an infected cell respond to primary or secondary infections. We establish a cell-based system to characterize a virus microenvironment, distinguishing infected, neighboring, and distal cells. Cell sorting, microscopy, proteomics, and cell cycle assays allow resolving cellular features and functional consequences of proximity to infection. We show that human cytomegalovirus (HCMV) infection primes neighboring cells for both subsequent HCMV infections and secondary infections with herpes simplex virus 1 and influenza A. Neighboring cells exhibit mitotic arrest, dampened innate immunity, and altered extracellular matrix. Conversely, distal cells are poised to slow viral spread due to enhanced antiviral responses. These findings demonstrate how infection reshapes the microenvironment through intercellular signaling to facilitate spread and how spatial proximity to an infection guides cell fate.

Exosomes: A potential tool for immunotherapy of ovarian cancer

Ovarian cancer is a malignant tumor of the female reproductive system, with a very poor prognosis and high mortality rates. Chemotherapy and radiotherapy are the most common treatments for ovarian cancer, with unsatisfactory results. Exosomes are a subpopulation of extracellular vesicles, which have a diameter of approximately 30-100 nm and are secreted by many different types of cells in various body fluids. Exosomes are highly stable and are effective carriers of immunotherapeutic drugs. Recent studies have shown that exosomes are involved in various cellular responses in the tumor microenvironment, influencing the development and therapeutic efficacy of ovarian cancer, and exhibiting dual roles in inhibiting and promoting tumor development. Exosomes also contain a variety of genes related to ovarian cancer immunotherapy that could be potential biomarkers for ovarian cancer diagnosis and prognosis. Undoubtedly, exosomes have great therapeutic potential in the field of ovarian cancer immunotherapy. However, translation of this idea to the clinic has not occurred. Therefore, it is important to understand how exosomes could be used in ovarian cancer immunotherapy to regulate tumor progression. In this review, we summarize the biomarkers of exosomes in different body fluids related to immunotherapy in ovarian cancer and the potential mechanisms by which exosomes influence immunotherapeutic response. We also discuss the prospects for clinical application of exosome-based immunotherapy in ovarian cancer.

Investigating the Function of Human Jumping Translocation Breakpoint Protein (hJTB) and Its Interacting Partners through In-Solution Proteomics of MCF7 Cells

Human jumping translocation breakpoint (hJTB) gene is located on chromosome 1q21 and is involved in unbalanced translocation in many types of cancer. JTB protein is ubiquitously present in normal cells but it is found to be overexpressed or downregulated in various types of cancer cells, where this protein and its isoforms promote mitochondrial dysfunction, resistance to apoptosis, genomic instability, proliferation, invasion and metastasis. Hence, JTB could be a tumor biomarker for different types of cancer, such as breast cancer (BC), and could be used as a drug target for therapy. However, the functions of the protein or the pathways through which it increases cell proliferation and invasiveness of cancer cells are not well-known. Therefore, we aim to investigate the functions of JTB by using in-solution digestion-based cellular proteomics of control and upregulated and downregulated JTB protein in MCF7 breast cancer cell line, taking account that in-solution digestion-based proteomics experiments are complementary to the initial in-gel based ones. Proteomics analysis allows investigation of protein dysregulation patterns that indicate the function of the protein and its interacting partners, as well as the pathways and biological processes through which it functions. We concluded that JTB dysregulation increases the epithelial-mesenchymal transition (EMT) potential and cell proliferation, harnessing cytoskeleton organization, apical junctional complex, metabolic reprogramming, and cellular proteostasis. Deregulated JTB expression was found to be associated with several proteins involved in mitochondrial organization and function, oxidative stress (OS), apoptosis, and interferon alpha and gamma signaling. Consistent and complementary to our previous results emerged by using in-gel based proteomics of transfected MCF7 cells, JTB-related proteins that are overexpressed in this experiment suggest the development of a more aggressive phenotype and behavior for this luminal type A non-invasive/poor-invasive human BC cell line that does not usually migrate or invade compared with the highly metastatic MDA-MB-231 cells. This more aggressive phenotype of MCF7 cells related to JTB dysregulation and detected by both in-gel and in-solution proteomics could be promoted by synergistic upregulation of EMT, Mitotic spindle and Fatty acid metabolism pathways. However, in both JTB dysregulated conditions, several downregulated JTB-interacting proteins predominantly sustain antitumor activities, attenuating some of the aggressive phenotypical and behavioral traits promoted by the overexpressed JTB-related partners.

IFITM protein regulation and functions: Far beyond the fight against viruses

Interferons (IFNs) are important cytokines that regulate immune responses through the activation of hundreds of genes, including interferon-induced transmembrane proteins (IFITMs). This evolutionarily conserved protein family includes five functionally active homologs in humans. Despite the high sequence homology, IFITMs vary in expression, subcellular localization and function. The initially described adhesive and antiproliferative or pro-oncogenic functions of IFITM proteins were diluted by the discovery of their antiviral properties. The large set of viruses that is inhibited by these proteins is constantly expanding, as are the possible mechanisms of action. In addition to their beneficial antiviral effects, IFITM proteins are often upregulated in a broad spectrum of cancers. IFITM proteins have been linked to most hallmarks of cancer, including tumor cell proliferation, therapeutic resistance, angiogenesis, invasion, and metastasis. Recent studies have described the involvement of IFITM proteins in antitumor immunity. This review summarizes various levels of IFITM protein regulation and the physiological and pathological functions of these proteins, with an emphasis on tumorigenesis and antitumor immunity.

Hepatitis Viruses Control Host Immune Responses by Modifying the Exosomal Biogenesis Pathway and Cargo

The development of smart immune evasion mechanisms is crucial for the establishment of acute and chronic viral hepatitis. Hepatitis is a major health problem worldwide arising from different causes, such as pathogens, metabolic disorders, and xenotoxins, with the five hepatitis viruses A, B, C, D, and E (HAV, HBV, HCV, HDV, and HEV) representing the majority of the cases. Most of the hepatitis viruses are considered enveloped. Recently, it was reported that the non-enveloped HAV and HEV are, in reality, quasi-enveloped viruses exploiting exosomal-like biogenesis mechanisms for budding. Regardless, all hepatitis viruses use exosomes to egress, regulate, and eventually escape from the host immune system, revealing another key function of exosomes apart from their recognised role in intercellular communication. This review will discuss how the hepatitis viruses exploit exosome biogenesis and transport capacity to establish successful infection and spread. Then, we will outline the contribution of exosomes in viral persistence and liver disease progression.

Exosome-mediated effects and applications in inflammatory diseases of the digestive system

Exosomes are membranous vesicles containing RNA and proteins that are specifically secreted in vivo. Exosomes have many functions, such as material transport and signal transduction between cells. Many studies have proven that exosomes can not only be used as biomarkers for disease diagnosis but also as carriers to transmit information between cells. Exosomes participate in a variety of physiological and pathological processes, including the immune response, antigen presentation, cell migration, cell differentiation, and tumour development. Differences in exosome functions depend on cell type. In recent years, exosome origin, cargo composition, and precise regulatory mechanisms have been the focus of research. Although exosomes have been extensively reported in digestive tumours, few articles have reviewed their roles in inflammatory diseases of the digestive system, especially inflammatory-related diseases (such as reflux oesophagitis, gastritis, inflammatory bowel disease, hepatitis, and pancreatitis). This paper briefly summarizes the roles of exosomes in inflammatory diseases of the digestive system to provide a basis for research on the mechanism of inflammatory diseases of the digestive system targeted by exosomes.

Hepatic exosomes with declined MiR-27b-3p trigger RIG-I/TBK1 signal pathway in macrophages

BACKGROUND AND AIMS

Evidence suggests that interferon alpha (IFNα) plays an essential role in decreasing the HBsAg quantification and elevating the rate of clinical cure in chronic hepatitis B (CHB). However, the mechanisms underlying the effects of the exosomes on the expression of host genes in IFNα treatment remain unclear.

METHODS

CHB patients with IFNα treatment were divided into responders and non-responders according to the degree of HBsAg decline. Through microRNA sequencing and a series of molecular biology methods, the key microRNAs in serum exosomes associated with clinical antiviral response of Peg-IFNα treatment in nucleotide analogue-treated CHB patients were investigated. The roles of exosomal miRNAs on the IFNα signal pathway were explored in macrophages.

RESULTS

MicroRNA sequencing and RT-qPCR assays confirmed six distinctly declined miRNAs in serum exosomes of responders at week 12 compared with levels at baseline. Exosomes with declined miR27b-3p in the serum of Peg-IFNα-treated responders activated phosphorylation of interferon regulatory factor 3/7 (IRF3/7) in IFNα synthesis pathway in macrophages. However, miR27b-3p overexpression in HepAD38 cells suppressed IFNα synthesis in macrophages, resulting in insufficient ability to eliminate HBV, whereas the inhibitory effect could be blocked by inhibitors of exosomes release. Luciferase assay showed miR-27b-3p directly suppressed retinoic acid-inducible gene I (RIG-I) and TANK-binding kinase 1 (TBK1) expressions, and these effects could be abrogated in mutation experiments.

CONCLUSIONS

In IFNα treatment, exosomes with declined miR-27b-3p triggered activation of RIG-I/TBK1 signalling in macrophages against HBV. Serum exosomal miR-27-3p might represent a potential biomarker for patients with CHB.

Mesenchymal Stem Cells and Their Small Extracellular Vesicles as Crucial Immunological Efficacy for Hepatic Diseases

Mesenchymal stem cell small extracellular vesicles (MSC-sEVs) are a priority for researchers because of their role in tissue regeneration. sEVs act as paracrine factors and carry various cargos, revealing the state of the parent cells and contributing to cell–cell communication during both physiological and pathological circumstances. Hepatic diseases are mainly characterized by inflammatory cell infiltration and hepatocyte necrosis and fibrosis, bringing the focus onto immune regulation and other regulatory mechanisms of MSCs/MSC-sEVs. Increasing evidence suggests that MSCs and their sEVs protect against acute and chronic liver injury by inducing macrophages (MΦ) to transform into the M2 subtype, accelerating regulatory T/B (Treg/Breg) cell activation and promoting immunosuppression. MSCs/MSC-sEVs also prevent the proliferation and differentiation of T cells, B cells, dendritic cells (DCs), and natural killer (NK) cells. This review summarizes the potential roles for MSCs/MSC-sEVs, including immunomodulation and tissue regeneration, in various liver diseases. There is also a specific focus on the use of MSC-sEVs for targeted drug delivery to treat hepatitis.

Myeloid Responses to Extracellular Vesicles in Health and Disease

Extracellular vesicles are mediators of cell-cell communication playing a key role in both steady-state and disease conditions. Extracellular vesicles carry diverse donor-derived cargos, including DNA, RNA, proteins, and lipids that induce a complex network of signals in recipient cells. Due to their ability to capture particulate matter and/or capacity to polarize and orchestrate tissue responses, myeloid immune cells (e.g., dendritic cells, macrophages, etc.) rapidly respond to extracellular vesicles, driving local and systemic effects. In cancer, myeloid-extracellular vesicle communication contributes to chronic inflammation, self-tolerance, and therapeutic resistance while in autoimmune disease, extracellular vesicles support inflammation and tissue destruction. Here, we review cellular mechanisms by which extracellular vesicles modulate myeloid immunity in cancer and autoimmune disease, highlighting some contradictory results and outstanding questions. We will also summarize how understanding of extracellular vesicle biology is being utilized for novel therapeutic and diagnostic applications.

Suppression of Interferon-α Treatment Response by Host Negative Factors in Hepatitis B Virus Infection

Chronic hepatitis B virus (CHB) infection remains a major global public health issue for which there is still lacking effective curative treatment. Interferon-α (IFN-α) and its pegylated form have been approved as an anti-HBV drug with the advantage of antiviral activity and host immunity against HBV infection enhancement, however, IFN-α treatment failure in CHB patients is a challenging obstacle with 70% of CHB patients respond poorly to exogenous IFN-α treatment. The IFN-α treatment response is negatively regulated by both viral and host factors, and the role of viral factors has been extensively illustrated, while much less attention has been paid to host negative factors. Here, we summarized evidence of host negative regulators and parameters involved in IFN-α therapy failure, review the mechanisms responsible for these effects, and discuss the possible improvement of IFN-based therapy and the rationale of combining the inhibitors of negative regulators in achieving an HBV cure.

Extracellular Vesicles Regulated by Viruses and Antiviral Strategies

Extracellular vesicles (EVs), consisting of exosomes, micro-vesicles, and other vesicles, mainly originate from the multi-vesicular body (MVB) pathway or plasma membrane. EVs are increasingly recognized as a tool to mediate the intercellular communication and are closely related to human health. Viral infection is associated with various diseases, including respiratory diseases, neurological diseases, and cancers. Accumulating studies have shown that viruses could modulate their infection ability and pathogenicity through regulating the component and function of EVs. Non-coding RNA (ncRNA) molecules are often targets of viruses and also serve as the main functional cargo of virus-related EVs, which have an important role in the epigenetic regulation of target cells. In this review, we summarize the research progress of EVs under the regulation of viruses, highlighting the content alteration and function of virus-regulated EVs, emphasizing their isolation methods in the context of virus infection, and potential antiviral strategies based on their use. This review would promote the understanding of the viral pathogenesis and the development of antiviral research.

Persistence of Hepatitis B Virus Infection: A Multi-Faceted Player for Hepatocarcinogenesis

Hepatitis B virus (HBV) infection has a multi-dimensional effect on the host, which not only alters the dynamics of immune response but also persists in the hepatocytes to predispose oncogenic factors. The virus exists in multiple forms of which the nuclear localized covalently closed circular DNA (cccDNA) is the most stable and the primary reason for viral persistence even after clearance of surface antigen and viral DNA. The second reason is the existence of pregenomic RNA (pgRNA) containing virion particles. On the other hand, the integration of the viral genome in the host chromosome also leads to persistent production of viral proteins along with the chromosomal instabilities. The interferon treatment or administration of nucleot(s)ide analogs leads to reduction in the viral DNA load, but the pgRNA and surface antigen clearance are a slow process and complete loss of serological HBsAg is rare. The prolonged exposure of immune cells to the viral antigens, particularly HBs antigen, in the blood circulation results in T-cell exhaustion, which disrupts immune clearance of the virus and virus-infected cells. In addition, it predisposes immune-tolerant microenvironment, which facilitates the tumor progression. Thus cccDNA, pgRNA, and HBsAg along with the viral DNA could be the therapeutic targets in the early disease stages that may improve the quality of life of chronic hepatitis B patients by impeding the progression of the disease toward hepatocellular carcinoma.

Identifying potential biomarkers in hepatitis B virus infection and its response to the antiviral therapy by integrated bioinformatic analysis

The antiviral treatment efficacy varies among chronic hepatitis B (CHB) patients and the underlying mechanism is unclear. An integrated bioinformatics analysis was performed to investigate the host factors that affect the therapeutic responsiveness in CHB patients. Four GEO data sets (GSE54747, GSE27555, GSE66698 and GSE66699) were downloaded from the Gene Expression Omnibus (GEO) database and analysed to identify differentially expressed genes(DEGs). Enrichment analyses of the DEGs were conducted using the DAVID database. Immune cell infiltration characteristics were analysed by CIBERSORT. Upstream miRNAs and lncRNAs of hub DEGs were identified by miRWalk 3.0 and miRNet in combination with the MNDR platform. As a result, seventy‐seven overlapping DEGs and 15 hub genes were identified including CCL5, CXCL9, MYH2, CXCR4, CD74, CCL4, HLA‐DRB1, ACTA1, CD69, CXCL10, HLA‐DRB5, HLA‐DQB1, CXCL13, STAT1 and CKM. The enrichment analyses revealed that the DEGs were mainly enriched in immune response and chemokine signalling pathways. Investigation of immune cell infiltration in liver samples suggested significantly different infiltration between responders and non‐responders, mainly characterized by higher proportions of CD8+ T cells and activated NK cells in non‐responders. The prediction of upstream miRNAs and lncRNAs led to the identification of a potential mRNA‐miRNA‐lncRNA regulatory network composed of 2 lncRNAs (H19 and GAS5) and 5 miRNAs (hsa‐mir‐106b‐5p, hsa‐mir‐17‐5p, hsa‐mir‐20a‐5p, hsa‐mir‐6720‐5p and hsa‐mir‐93‐5p) targeting CCL5 mRNA. In conclusion, our study suggested that host genetic factors could affect therapeutic responsiveness in CHB patients. The antiviral process might be associated with the chemokine‐mediated immune response and immune cell infiltration in the liver microenvironment.

The Mechanisms of HBV-Induced Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a common malignancy, and the hepatitis B virus (HBV) is its major pathogenic factor. Over the past decades, it has been confirmed that HBV infection could promote disease progression through a variety of mechanisms, ultimately leading to the malignant transformation of liver cells. Many factors have been identified in the pathogenesis of HBV-associated HCC (HBV-HCC), including HBV gene integration, genomic instability caused by mutation, and activation of cancer-promoting signaling pathways. As research in the progression of HBV-HCC progresses, the role of many new mechanisms, such as epigenetics, exosomes, autophagy, metabolic regulation, and immune suppression, is also being continuously explored. The occurrence of HBV-HCC is a complex process caused by interactions across multiple genes and multiple steps, where the synergistic effects of various cancer-promoting mechanisms accelerate the process of disease evolution from inflammation to tumorigenesis. In this review, we aim to provide a brief overview of the mechanisms involved in the occurrence and development of HBV-HCC, which may contribute to a better understanding of the role of HBV in the occurrence and development of HCC.

Emerging role and therapeutic application of exosome in hepatitis virus infection and associated diseases

Hepatitis viruses are chief pathogens of hepatitis and end-stage liver diseases. Their replication and related pathogenic process highly rely on the host micro-environment and multiple cellular elements, including exosomes. Representing with a sort of cell-derived vesicle structure, exosomes were considered to be dispensable cellular components, even wastes. Along with advancing investigation, a specific profile of exosome in driving hepatitis viruses' infection and hepatic disease progression is revealed. Exosomes greatly affect the pathogenesis of hepatitis viruses by mediating their replication and modulating the host immune responses. The characteristics of host exosomes are markedly changed after infection with hepatitis viruses. Exosomes released from hepatitis virus-infected cells can carry viral nucleic or protein components, thereby acting as an effective subterfuge for hepatitis viruses by participating in viral transportation and immune escape. On the contrary, immune cell-derived exosomes contribute toward the innate antiviral immune defense and virus eradication. There is growing evidence supporting the application of exosomal biomarkers for predicting disease progress or therapeutic outcome, while exosomal nanoshuttles are regarded as promising therapeutic options based on their delivery properties and immune compatibility. In this review, we summarize the biogenesis and secretion mechanism of exosomes, review the recent findings pertaining to the role of exosomes in the interplay between hepatitis viruses and innate immune responses, and conclude their potential in further therapeutic application.

Bmp8a is an essential positive regulator of antiviral immunity in zebrafish

Bone morphogenetic protein (BMP) is a kind of classical multi-functional growth factor that plays a vital role in the formation and maintenance of bone, cartilage, muscle, blood vessels, and the regulation of adipogenesis and thermogenesis. However, understanding of the role of BMPs in antiviral immunity is still limited. Here we demonstrate that Bmp8a is a newly-identified positive regulator for antiviral immune responses. The bmp8a^−/− zebrafish, when infected with viruses, show reduced antiviral immunity and increased viral load and mortality. We also show for the first time that Bmp8a interacts with Alk6a, which promotes the phosphorylation of Tbk1 and Irf3 through p38 MAPK pathway, and induces the production of type I interferons (IFNs) in response to viral infection. Our study uncovers a previously unrecognized role of Bmp8a in regulation of antiviral immune responses and provides a target for controlling viral infection.

Zhang, Liu and colleagues identify the role of Bmp8a in antiviral immunity in zebrafish and provide mechanistic insight into its function. Bmp8a could serve as a future target for investigative studies of antiviral immune responses.

Extracellular Vesicles in Viral Infections: Two Sides of the Same Coin?

Extracellular vesicles are small membrane structures containing proteins and nucleic acids that are gaining a lot of attention lately. They are produced by most cells and can be detected in several body fluids, having a huge potential in therapeutic and diagnostic approaches. EVs produced by infected cells usually have a molecular signature that is very distinct from healthy cells. For intracellular pathogens like viruses, EVs can have an even more complex function, since the viral biogenesis pathway can overlap with EV pathways in several ways, generating a continuum of particles, like naked virions, EVs containing infective viral genomes and quasi-enveloped viruses, besides the classical complete viral particles that are secreted to the extracellular space. Those particles can act in recipient cells in different ways. Besides being directly infective, they also can prime neighbor cells rendering them more susceptible to infection, block antiviral responses and deliver isolated viral molecules. On the other hand, they can trigger antiviral responses and cytokine secretion even in uninfected cells near the infection site, helping to fight the infection and protect other cells from the virus. This protective response can also backfire, when a massive inflammation facilitated by those EVs can be responsible for bad clinical outcomes. EVs can help or harm the antiviral response, and sometimes both mechanisms are observed in infections by the same virus. Since those pathways are intrinsically interlinked, understand the role of EVs during viral infections is crucial to comprehend viral mechanisms and respond better to emerging viral diseases.

The Effects of RKI-1447 in a Mouse Model of Nonalcoholic Fatty Liver Disease Induced by a High-Fat Diet and in HepG2 Human Hepatocellular Carcinoma Cells Treated with Oleic Acid

Background

This study aimed to investigate the effects of RKI-1447, a selective inhibitor of Rho-associated ROCK kinases, in a mouse model of nonalcoholic fatty liver disease (NAFLD) induced by a high-fat diet, and in oleic acid-treated HepG2 human hepatocellular carcinoma cells in vitro.

Material/Methods

Four study groups of mice included: the control group; the high-fat diet (HFD) group; the HFD+RKI-1447 (2 mg/kg) group; and the HFD+RKI-1447 (8 mg/kg) group. Mice were fed a high-fat diet for 12 weeks. Mice in the HFD+RKI-1447 groups were fed a high-fat diet for 12 weeks and treated with RKI-1447 twice weekly for three weeks. The HepG2 human hepatocellular carcinoma cells were treated with or without RKI-1447 for 2 h and treated with oleic acid for 24 h.

Results

In the mouse model of NAFLD, RKI-1447 reduced insulin resistance and the levels of alanine aminotransferase (ALT), aspartate transaminase (AST), total cholesterol, triglyceride, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), malondialdehyde (MDA), and superoxide dismutase (SOD). RKI-1447 reduced the histological changes in the mouse model of NAFLD in mice fed a high-fat diet and significantly inhibited the generations of triglyceride, IL-6, and TNF-α. RKI-1447 reduced the levels of oxidative stress in HepG2 cells treated with oleic acid and significantly down-regulated the expression of RhoA, ROCK1, ROCK2, toll-like receptor 4 (TLR4), p-TBK1, and p-IRF3. RKI-1447 treatment also inhibited RhoA expression.

Conclusions

In a mouse model of NAFLD, RKI-1447 inhibited ROCK and modulated insulin resistance, oxidative stress, and inflammation through the ROCK/TLR4/TBK1/IRF3 pathway.

The immunobiology of hepatocellular carcinoma in humans and mice: Basic concepts and therapeutic implications

Basic and clinical studies have demonstrated the efficacy of immunotherapy, a technical and conceptual breakthrough that has revolutionised cancer treatment. Hepatocellular carcinoma (HCC), a deadly malignancy with aetiologic diversity and a chronic course, is strongly influenced by the immune system, and was recently found to partially benefit from immune-checkpoint inhibitor therapy. Notably, HCC onco-immunology depends on diverse genetic and environmental factors that together shape cancer-promoting inflammation and immune dysfunction - critical processes that control HCC malignant progression and response to therapy. Herein, we summarise the current understanding of liver and HCC onco-immunology obtained through basic studies with mouse models and clinical practice in humans. In particular, we discuss preclinical and clinical findings that implicate immunomodulation as a major factor in HCC development and explain the basis for HCC-targeting immunotherapy.

Exosomes in Hepatitis B Virus Transmission and Related Immune Response

The chronicity of Hepatitis B virus (HBV) infection relates to both viral factors and host factors. HBV could result in persistent infection and even serious liver disease, including chronic hepatitis B (CHB), cirrhosis and hepatocellular carcinoma (HCC). Although the HBV vaccine can effectively prevent HBV infection, chronic HBV infection still endangers human health and results in a large social burden. Moreover, the mechanisms underlying the HBV-mediated imbalance of the immune response and persistent infection are not fully understood. Exosomes are extracellular vesicles (EVs) 40-160 nm in size that are released from many cells and transfer specific functional RNAs, proteins, lipids and viral components from donor to recipient cells. These exosome nanovesicles are associated with various biological processes, such as cellular homeostasis, immune response and cancer progression. Besides, previous studies on exosomes have shown that they take part in viral pathogenicity due to the similarity in structure and function between exosomes and enveloped viruses. Moreover, exosome as a novel immunomodulatory carrier plays a significant role in viral immunology. In this review, we focus on the latest progress in understanding the role of exosomes in HBV transmission as well as their vital roles in immune regulation during HBV infection. Furthermore, we discuss the potential clinical applications of exosomes in hepatitis B infection, including the use of exosomes in the auxiliary diagnosis and treatment of hepatitis B.

Shaping of Innate Immune Response by Fatty Acid Metabolite Palmitate

Innate immune cells monitor invading pathogens and pose the first-line inflammatory response to coordinate with adaptive immunity for infection removal. Innate immunity also plays pivotal roles in injury-induced tissue remodeling and the maintenance of tissue homeostasis in physiological and pathological conditions. Lipid metabolites are emerging as the key players in the regulation of innate immune responses, and recent work has highlighted the importance of the lipid metabolite palmitate as an essential component in this regulation. Palmitate modulates innate immunity not only by regulating the activation of pattern recognition receptors in local innate immune cells, but also via coordinating immunological activity in inflammatory tissues. Moreover, protein palmitoylation controls various cellular physiological processes. Herein, we review the updated evidence that palmitate catabolism contributes to innate immune cell-mediated inflammatory processes that result in immunometabolic disorders.