Host Innate Immunity Against Hepatitis Viruses and Viral Immune Evasion

NS3 of hepatitis C virus drives hepatocellular carcinoma progression through a novel RNA-interference pathway

Hepatocellular carcinoma (HCC), a severe consequence of hepatitis C virus infection, is significantly influenced by the virus's non-structural protein 3 (NS3). This study employed transcriptome sequencing to explore the role of NS3 in promoting HCC progression by comparing gene expression profiles between HCV-infected HCC tissues and healthy liver controls. Key genes regulated by NS3 were identified and validated with quantitative reverse transcription PCR (RT-qPCR) and western blot analyses. Functionality assays, including CCK-8, BrdU, and Transwell migration and invasion tests, were performed to evaluate the effects of NS3 on HCC cell proliferation, migration, and invasion. Further investigation through a dual-luciferase reporter and RNA pull-down assays revealed that NS3 specifically upregulates circ_0001175. This circular RNA interacts with and inhibits miR-130a-5p, diminishing its regulatory impact on P53 by modulating the MDM4 pathway, thereby promoting oncogenic characteristics. The findings highlight the NS3-induced circ_0001175/miR-130a-5p/MDM4/P53 pathway as a potential therapeutic target, offering promising directions for treatment strategies in HCV-related HCC.

Type I interferons induce guanylate-binding proteins and lysosomal defense in hepatocytes to control malaria

Plasmodium parasites undergo development and replication within hepatocytes before infecting erythrocytes and initiating clinical malaria. Although type I interferons (IFNs) are known to hinder Plasmodium infection within the liver, the underlying mechanisms remain unclear. Here, we describe two IFN-I-driven hepatocyte antimicrobial programs controlling liver-stage malaria. First, oxidative defense by NADPH oxidases 2 and 4 triggers a pathway of lysosomal fusion with the parasitophorous vacuole (PV) to help clear Plasmodium. Second, guanylate-binding protein (GBP) 1-mediated disruption of the PV activates the caspase-1 inflammasome, inducing pyroptosis to remove infected host cells. Remarkably, both human and mouse hepatocytes enlist these cell-autonomous immune programs to eliminate Plasmodium, with their pharmacologic or genetic inhibition leading to profound malarial susceptibility in vivo. In addition to identifying IFN-I-mediated cell-autonomous immune circuits controlling Plasmodium infection in the hepatocytes, our study also extends the understanding of how non-immune cells are integral to protective immunity against malaria.

Limited impact of hepatitis A virus 3C protease-mediated cleavage on the functions of NEMO in human hepatocytes

NF-κB essential modulator (NEMO) is critically involved in the induction of interferons (IFNs) and pro-inflammatory cytokines. Hepatitis A virus (HAV) 3C protease was recently identified to cleave NEMO in non-hepatic cells. This study aimed at understanding efficiency and function of HAV 3C-mediated NEMO cleavage in hepatocytes. HAV 3C protease and its precursor 3CD strongly affected NEMO abundance in ectopic expression models, which was not observed in HAV replicon cells and upon HAV infection. Using a cleavage-resistant NEMO mutant, we found that specific cleavage by 3C only marginally contributed to NEMO degradation, whereas the magnitude of the effect was due to cytotoxic effects induced by 3C activity. Cleavage efficiency generally did not suffice to disrupt the type I IFN or NF-κB signaling pathways. Knockout of NEMO indeed abrogated both pathways, whereas efficient knockdown had limited the impact on NEMO-mediated signaling, suggesting that low levels of NEMO are sufficient to maintain antiviral responses in hepatocytes. NEMO cleavage was barely detectable in a cell line harboring a persistent HAV replicon or in HAV-infected cells. HAV infection induced a robust innate immune response, which was not affected by efficient knockdown of NEMO, arguing for a limited potential contribution of NEMO cleavage to innate immune counteraction. Overall, our data suggest that HAV 3C is capable of partially cleaving NEMO as reported. However, since minute expression levels of NEMO were sufficient for induction of innate immunity, inefficient NEMO cleavage by HAV is unlikely to contribute to dampening of innate immune responses in hepatocytes.IMPORTANCEHepatitis A virus (HAV) establishes acute infections of the liver, which are always cleared, while a number of mechanisms have been identified contributing to immune escape. Among those, proteolytic cleavage of NF-κB essential modulator (NEMO) by HAV has been suggested to counteract innate immune responses. This study demonstrates that the HAV 3C protease cleaves NEMO inefficiently and does not result in substantial disruption of antiviral signaling. Importantly, NEMO remains capable of inducing an effective immune response in hepatocytes even at low expression levels. Our findings suggest a limited role for NEMO cleavage in HAV's interaction with host immunity and call for a revision of our understanding of HAV counteraction mechanisms.

Type-I IFNs induce GBPs and lysosomal defense in hepatocytes to control malaria

Plasmodium parasites undergo development and replication within the hepatocytes before infecting the erythrocytes and initiating clinical malaria. Although type-I interferons (IFNs) are known to hinder Plasmodium infection within the liver, the underlying mechanisms remain unclear. Here, we describe two IFN-I-driven hepatocyte antimicrobial programs controlling liver-stage malaria. First, oxidative defense by NADPH oxidases 2 and 4 triggers a pathway of lysosomal fusion with the parasitophorous vacuole (PV) to help clear Plasmodium . Second, guanylate-binding protein (GBP) 1 disruption of the PV activates caspase-1 inflammasome, inducing pyroptosis to remove the infected host cells. Remarkably, both human and mouse hepatocytes enlist these cell-autonomous immune programs to eliminate Plasmodium ; their pharmacologic or genetic inhibition led to profound malarial susceptibility, and are essential in vivo . In addition to identifying the IFN-I-mediated cell-autonomous immune circuits controlling Plasmodium infection in the hepatocytes, this study extends our understanding of how non-immune cells are integral to protective immunity against malaria.

Understanding how methyltransferase-like 3 functions in lung diseases: From pathogenesis to clinical application

Lung diseases have complex pathogenesis and treatment challenges, showing an obvious increase in the rate of diagnosis and death every year. Therefore, elucidating the mechanism for their pathogenesis and treatment ineffective from novel views is essential and urgent. Methyltransferase-like 3 (METTL3) is a novel post-transcriptional regulator for gene expression that has been implicated in regulating lung diseases, including that observed in chronic conditions such as pulmonary fibrosis (PF), pulmonary arterial hypertension (PAH), and chronic obstructive pulmonary disease (COPD), as well as acute conditions such as pneumonia, severe acute respiratory syndrome coronavirus 2 infection, and sepsis-induced acute respiratory distress syndrome. Notably, a comprehensive summary and analysis of findings from these studies might help understand lung diseases from the novel view of METTL3-regulated mechanism, however, such a review is still lacking. Therefore, this review aims to bridge such shortage by summarising the roles of METTL3 in lung diseases, establishing their interrelationships, and elucidating the potential applications of METTL3 regarding diagnosis, treatment, and prognosis. The analysis collectively suggests METTL3 is contributable to the onset and progression of these lung diseases, thereby prospecting METTL3 as a valuable biomarker for their diagnosis, treatment, and prognosis. In conclusion, this review offers elucidation into the correlation between METTL3 and lung diseases in both research and clinical settings and highlights potential avenues for exploring the roles of METTL3 in the respiratory system.

Viral Hepatitis: Host Immune Interaction, Pathogenesis and New Therapeutic Strategies

Viral hepatitis is a major cause of liver illness worldwide. Despite advances in the understanding of these infections, the pathogenesis of hepatitis remains a complex process driven by intricate interactions between hepatitis viruses and host cells at the molecular level. This paper will examine in detail the dynamics of these host-pathogen interactions, highlighting the key mechanisms that regulate virus entry into the hepatocyte, their replication, evasion of immune responses, and induction of hepatocellular damage. The unique strategies employed by different hepatitis viruses, such as hepatitis B, C, D, and E viruses, to exploit metabolic and cell signaling pathways to their advantage will be discussed. At the same time, the innate and adaptive immune responses put in place by the host to counter viral infection will be analyzed. Special attention will be paid to genetic, epigenetic, and environmental factors that modulate individual susceptibility to different forms of viral hepatitis. In addition, this work will highlight the latest findings on the mechanisms of viral persistence leading to the chronic hepatitis state and the potential implications for the development of new therapeutic strategies. Fully understanding the complex host-pathogen interactions in viral hepatitis is crucial to identifying new therapeutic targets, developing more effective approaches for treatment, and shedding light on the mechanisms underlying progression to more advanced stages of liver damage.

Hepatocytes and the art of killing Plasmodium softly

The Plasmodium parasites that cause malaria undergo asymptomatic development in the parenchymal cells of the liver, the hepatocytes, prior to infecting erythrocytes and causing clinical disease. Traditionally, hepatocytes have been perceived as passive bystanders that allow hepatotropic pathogens such as Plasmodium to develop relatively unchallenged. However, now there is emerging evidence suggesting that hepatocytes can mount robust cell-autonomous immune responses that target Plasmodium, limiting its progression to the blood and reducing the incidence and severity of clinical malaria. Here we discuss our current understanding of hepatocyte cell-intrinsic immune responses that target Plasmodium and how these pathways impact malaria.

Beyond schistosomiasis: unraveling co-infections and altered immunity

Schistosomiasis is a neglected tropical disease caused by the helminth Schistosoma spp. and has the second highest global impact of all parasites. Schistosoma are transmitted through contact with contaminated fresh water predominantly in Africa, Asia, the Middle East, and South America. Due to the widespread prevalence of Schistosoma, co-infection with other infectious agents is common but often poorly described. Herein, we review recent literature describing the impact of Schistosoma co-infection between species and Schistosoma co-infection with blood-borne protozoa, soil-transmitted helminths, various intestinal protozoa, Mycobacterium, Salmonella, various urinary tract infection-causing agents, and viral pathogens. In each case, disease severity and, of particular interest, the immune landscape, are altered as a consequence of co-infection. Understanding the impact of schistosomiasis co-infections will be important when considering treatment strategies and vaccine development moving forward.

Recent advances in different interactions between toll-like receptors and hepatitis B infection: a review

Hepatitis B virus (HBV) B infections remain a primary global health concern. The immunopathology of the infection, specifically the interactions between HBV and the host immune system, remains somewhat unknown. It has been discovered that innate immune reactions are vital in eliminating HBV. Toll-like receptors (TLRs) are an essential category of proteins that detect pathogen-associated molecular patterns (PAMPs). They begin pathways of intracellular signals to stimulate pro-inflammatory and anti-inflammatory cytokines, thus forming adaptive immune reactions. HBV TLRs include TLR2, TLR3, TLR4, TLR7 and TLR9. Each TLR has its particular molecule to recognize; various TLRs impact HBV and play distinct roles in the pathogenesis of the disease. TLR gene polymorphisms may have an advantageous or disadvantageous efficacy on HBV infection, and some single nucleotide polymorphisms (SNPs) can influence the progression or prognosis of infection. Additionally, it has been discovered that similar SNPs in TLR genes might have varied effects on distinct populations due to stress, diet, and external physical variables. In addition, activation of TLR-interceded signaling pathways could suppress HBV replication and increase HBV-particular T-cell and B-cell reactions. By identifying these associated polymorphisms, we can efficiently advance the immune efficacy of vaccines. Additionally, this will enhance our capability to forecast the danger of HBV infection or the threat of dependent liver disease development via several TLR SNPs, thus playing a role in the inhibition, monitoring, and even treatment guidance for HBV infection. This review will show TLR polymorphisms, their influence on TLR signaling, and their associations with HBV diseases.

Comparison of HAV and HCV infections in vivo and in vitro reveals distinct patterns of innate immune evasion and activation

BACKGROUND & AIMS

Hepatitis A virus (HAV) infections are considered not to trigger innate immunity in vivo, in contrast to hepatitis C virus (HCV). This lack of induction has been imputed to strong interference by HAV proteases 3CD and 3ABC. We aimed to elucidate the mechanisms of immune activation and counteraction by HAV and HCV in vivo and in vitro.

METHODS

Albumin-urokinase-type plasminogen activator/severe combined immunodeficiency (Alb/uPA-SCID) mice with humanised livers were infected with HAV and HCV. Hepatic cell culture models were used to assess HAV and HCV sensing by Toll-like receptor 3 and retinoic acid-inducible gene I/melanoma differentiation-associated protein 5 (RIG-I/MDA5), respectively. Cleavage of the adaptor proteins TIR-domain-containing adapter-inducing interferon-β (TRIF) and mitochondrial antiviral-signalling protein (MAVS) was analysed by transient and stable expression of HAV and HCV proteases and virus infection.

RESULTS

We detected similar levels of interferon-stimulated gene induction in hepatocytes of HAV- and HCV-infected mice with humanised liver. In cell culture, HAV induced interferon-stimulated genes exclusively upon MDA5 sensing and depended on LGP2 (laboratory of genetics and physiology 2). TRIF and MAVS were only partially cleaved by HAV 3ABC and 3CD, not sufficiently to abrogate signalling. In contrast, HCV NS3-4A efficiently degraded MAVS, as previously reported, whereas TRIF cleavage was not detected.

CONCLUSIONS

HAV induces an innate immune response in hepatocytes via MDA5/LGP2, with limited control of both pathways by proteolytic cleavage. HCV activates Toll-like receptor 3 and lacks TRIF cleavage, suggesting that this pathway mainly contributes to HCV-induced antiviral responses in hepatocytes. Our results shed new light on the induction of innate immunity and counteraction by HAV and HCV.

IMPACT AND IMPLICATIONS

Understanding the mechanisms that determine the differential outcomes of HAV and HCV infections is crucial for the development of effective therapies. Our study provides insights into the interplay between these viruses and the host innate immune response in vitro and in vivo, shedding light on previously controversial or only partially investigated aspects. This knowledge could tailor the development of new strategies to combat HCV persistence, as well as improve our understanding of the factors underlying successful HAV clearance.

Increased liver stiffness promotes hepatitis B progression by impairing innate immunity in CCl4-induced fibrotic HBV+ transgenic mice

BACKGROUND

Hepatitis B virus (HBV) infection develops as an acute or chronic liver disease, which progresses from steatosis, hepatitis, and fibrosis to end-stage liver diseases such as cirrhosis and hepatocellular carcinoma (HCC). An increased stromal stiffness accompanies fibrosis in chronic liver diseases and is considered a strong predictor for disease progression. The goal of this study was to establish the mechanisms by which enhanced liver stiffness regulates HBV infectivity in the fibrotic liver tissue.

METHODS

For in vitro studies, HBV-transfected HepG2.2.15 cells were cultured on polydimethylsiloxane gels coated by polyelectrolyte multilayer films of 2 kPa (soft) or 24 kPa (stiff) rigidity mimicking the stiffness of the healthy or fibrotic liver. For in vivo studies, hepatic fibrosis was induced in C57Bl/6 parental and HBV+ transgenic (HBVTg) mice by injecting CCl4 twice a week for 6 weeks.

RESULTS

We found higher levels of HBV markers in stiff gel-attached hepatocytes accompanied by up-regulated OPN content in cell supernatants as well as suppression of anti-viral interferon-stimulated genes (ISGs). This indicates that pre-requisite "fibrotic" stiffness increases osteopontin (OPN) content and releases and suppresses anti-viral innate immunity, causing a subsequent rise in HBV markers expression in hepatocytes. In vitro results were corroborated by data from HBVTg mice administered CCl4 (HBVTg CCl4). These mice showed higher HBV RNA, DNA, HBV core antigen (HBcAg), and HBV surface antigen (HBsAg) levels after liver fibrosis induction as judged by a rise in Col1a1, SMA, MMPs, and TIMPs mRNAs and by increased liver stiffness. Importantly, CCl4-induced the pro-fibrotic activation of liver cells, and liver stiffness was higher in HBVTg mice compared with control mice. Elevation of HBV markers and OPN levels corresponded to decreased ISG activation in HBVTg CCl4 mice vs HBVTg control mice.

CONCLUSION

Based on our data, we conclude that liver stiffness enhances OPN levels to limit anti-viral ISG activation in hepatocytes and promote an increase in HBV infectivity, thereby contributing to end-stage liver disease progression.

Action Mechanisms and Scientific Rationale of Using Nasal Vaccine (HeberNasvac) for the Treatment of Chronic Hepatitis B

Nasvac (HeberNasvac®) is a novel therapeutic vaccine for chronic hepatitis B (CHB). This product is a formulation of the core (HBcAg) and surface (HBsAg) antigens of the hepatitis B virus (HBV), administered by nasal and subcutaneous routes, in a distinctive schedule of immunizations. In the present review article, we discuss the action mechanisms of HeberNasvac, considering the immunological properties of the product and their antigens. Specifically, we discuss the capacity of HBcAg to activate different pathways of innate immunity and the signal transduction after a multi-TLR agonist effect, and we review the results of recent clinical trials and in vitro studies. Aimed at understanding the clinical results of Nasvac and other therapeutic vaccines under development, we discuss the rationale of administering a therapeutic vaccine through the nasal route and also the current alternatives to combine therapeutic vaccines and antivirals (NUCs). We also disclose potential applications of this product in novel fields of immunotherapy.