TGF-β triggers HBV cccDNA degradation through AID-dependent deamination

Current Status and Challenges in Anti-Hepatitis B Virus Agents Based on Inactivation/Inhibition or Elimination of Hepatitis B Virus Covalently Closed Circular DNA

There has been over half a century since the discovery of hepatitis B virus (HBV) to now, but approximately 300 million patients with chronic hepatitis B (CHB) still live in the world, resulting in about one million deaths every year. Although currently approved antivirals (e.g., nucleoside analogues) are effective at reducing HBV replication, they have almost no impact on the existing HBV covalently closed circular DNA (cccDNA) reservoir. HBV cccDNA is a critical obstacle to the complete elimination of the virus via antiviral therapy. The true cure of HBV infection requires the eradication of viral cccDNA from HBV-infected cells; thus, the development of new agents directly or indirectly targeting HBV cccDNA is urgently needed due to the limitations of current available drugs against HBV infection. In this regard, it is the major focus of current anti-HBV research worldwide via different mechanisms to either inactivate/inhibit (functional cure) or eliminate (complete cure) HBV cccDNA. Therefore, this review discussed and summarized recent advances and challenges in efforts to inactivate/silence or eliminate viral cccDNA using anti-HBV agents from different sources, such as small molecules (including epigenetic drugs) and polypeptides/proteins, and siRNA or gene-editing approaches targeting/attenuating HBV cccDNA via different mechanisms, as well as future directions that may be considered in efforts to truly cure chronic HBV infection. In conclusion, no breakthrough has been made yet in attenuating HBV cccDNA, although a number of candidates have advanced into the phase of clinical trials. Furthermore, the overwhelming majority of the candidates function to indirectly target HBV cccDNA. No outstanding candidate directly targets HBV cccDNA. Relatively speaking, CCC_R08 and nitazoxanide may be some of the most promising agents to clear HBV infection in small molecule compounds. Additionally, CRISPR-Cas9 systems can directly target HBV cccDNA for decay and demonstrate significant anti-HBV activity. Consequently, gene-editing approaches targeting HBV cccDNA may be one of the most promising means to achieve the core goal of anti-HBV therapeutic strategies. In short, more basic studies on HBV infection need to be carried out to overcome these challenges.

Chronic inflammation and the hallmarks of aging

BACKGROUND

Recently, the hallmarks of aging were updated to include dysbiosis, disabled macroautophagy, and chronic inflammation. In particular, the low-grade chronic inflammation during aging, without overt infection, is defined as "inflammaging," which is associated with increased morbidity and mortality in the aging population. Emerging evidence suggests a bidirectional and cyclical relationship between chronic inflammation and the development of age-related conditions, such as cardiovascular diseases, neurodegeneration, cancer, and frailty. How the crosstalk between chronic inflammation and other hallmarks of aging underlies biological mechanisms of aging and age-related disease is thus of particular interest to the current geroscience research.

SCOPE OF REVIEW

This review integrates the cellular and molecular mechanisms of age-associated chronic inflammation with the other eleven hallmarks of aging. Extra discussion is dedicated to the hallmark of "altered nutrient sensing," given the scope of Molecular Metabolism. The deregulation of hallmark processes during aging disrupts the delicate balance between pro-inflammatory and anti-inflammatory signaling, leading to a persistent inflammatory state. The resultant chronic inflammation, in turn, further aggravates the dysfunction of each hallmark, thereby driving the progression of aging and age-related diseases.

MAIN CONCLUSIONS

The crosstalk between chronic inflammation and other hallmarks of aging results in a vicious cycle that exacerbates the decline in cellular functions and promotes aging. Understanding this complex interplay will provide new insights into the mechanisms of aging and the development of potential anti-aging interventions. Given their interconnectedness and ability to accentuate the primary elements of aging, drivers of chronic inflammation may be an ideal target with high translational potential to address the pathological conditions associated with aging.

Immune response and treatment targets of chronic hepatitis B virus infection: innate and adaptive immunity

Chronic hepatitis B virus (HBV) infection is a major global public health risk that threatens human life and health, although the number of vaccinated people has increased. The clinical outcome of HBV infection depends on the complex interplay between viral replication and the host immune response. Innate immunity plays an important role in the early stages of the disease but retains no long-term immune memory. However, HBV evades detection by the host innate immune system through stealth. Therefore, adaptive immunity involving T and B cells is crucial for controlling and clearing HBV infections that lead to liver inflammation and damage. The persistence of HBV leads to immune tolerance owing to immune cell dysfunction, T cell exhaustion, and an increase in suppressor cells and cytokines. Although significant progress has been made in HBV treatment in recent years, the balance between immune tolerance, immune activation, inflammation, and fibrosis in chronic hepatitis B remains unknown, making a functional cure difficult to achieve. Therefore, this review focuses on the important cells involved in the innate and adaptive immunity of chronic hepatitis B that target the host immune system and identifies treatment strategies.

Transient and tunable CRISPRa regulation of APOBEC/AID genes for targeting hepatitis B virus

APOBEC/AID cytidine deaminases play an important role in innate immunity and antiviral defenses and were shown to suppress hepatitis B virus (HBV) replication by deaminating and destroying the major form of HBV genome, covalently closed circular DNA (cccDNA), without toxicity to the infected cells. However, developing anti-HBV therapeutics based on APOBEC/AID is complicated by the lack of tools for activating and controlling their expression. Here, we developed a CRISPR-activation-based approach (CRISPRa) to induce APOBEC/AID transient overexpression (>4-800,000-fold increase in mRNA levels). Using this new strategy, we were able to control APOBEC/AID expression and monitor their effects on HBV replication, mutation, and cellular toxicity. CRISPRa prominently reduced HBV replication (∼90%-99% decline of viral intermediates), deaminated and destroyed cccDNA, but induced mutagenesis in cancer-related genes. By coupling CRISPRa with attenuated sgRNA technology, we demonstrate that APOBEC/AID activation can be precisely controlled, eliminating off-site mutagenesis in virus-containing cells while preserving prominent antiviral activity. This study untangles the differences in the effects of physiologically expressed APOBEC/AID on HBV replication and cellular genome, provides insights into the molecular mechanisms of HBV cccDNA mutagenesis, repair, and degradation, and, finally, presents a strategy for a tunable control of APOBEC/AID expression and for suppressing HBV replication without toxicity.

Interaction between the Hepatitis B Virus and Cellular FLIP Variants in Viral Replication and the Innate Immune System

During viral evolution and adaptation, many viruses have utilized host cellular factors and machinery as their partners. HBx, as a multifunctional viral protein encoded by the hepatitis B virus (HBV), promotes HBV replication and greatly contributes to the development of HBV-associated hepatocellular carcinoma (HCC). HBx interacts with several host factors in order to regulate HBV replication and evolve carcinogenesis. The cellular FADD-like IL-1β-converting enzyme (FLICE)-like inhibitory protein (c-FLIP) is a major factor that functions in a variety of cellular pathways and specifically in apoptosis. It has been shown that the interaction between HBx and c-FLIP determines HBV fate. In this review, we provide a comprehensive and detailed overview of the interplay between c-FLIP and HBV in various environmental circumstances. We describe strategies adapted by HBV to establish its chronic infection. We also summarize the conventional roles of c-FLIP and highlight the functional outcome of the interaction between c-FLIP and HBV or other viruses in viral replication and the innate immune system.

Transforming growth factor-β: An early predictor of a functional cure in chronic hepatitis B treated with interferon

BACKGROUND

The relationship between the serum transforming growth factor (TGF)-β level and HBsAg loss has not been clearly elaborated in patients with chronic hepatitis B (CHB).

METHODS

Two cohorts of patients with CHB were studied. Cohort A: A total of 207 hepatitis B e antigen (HBeAg)-negative CHB patients who finished ≥1 year nucleos(t)ide analogue monotherapy and sequentially received PEGylated interferon treatment for less than 96 weeks were included. Cohort B: Forty HBeAg-positive patients who initially received entecavir therapy for at least 96 weeks were included. Their viral markers and serum TGF-β levels were measured at different time points during therapy.

RESULTS

The levels of serum TGF-β and HBsAg (0-24 W) were significantly lower in the patients who had HBsAg< 0.05 IU/mL at 48 weeks than in patients who did not in cohort A. We got the same results when we further divided the patients into subgroups according to the initial HBsAg cut-off values (1000 IU/mL, 100 IU/mL, 50 IU/mL) in cohort A. However, HBeAg seroconversion did not lead to the downregulation of TGF-β levels. The levels of serum TGF-β were significantly correlated with HBsAg quantitation in cohort A (12-24 W) but not in cohort B (0-48 W). The levels of TGF-β at week 12 could be used as an early index to predict a functional cure (AUC=0.818) as well as the levels of HBsAg itself (AUC=0.882) in HBeAg-negative chronic hepatitis B patients treated with PEGylated interferon.

CONCLUSIONS

The levels of serum TGF-β were significantly associated with HBsAg loss but not with HBeAg seroconversion and could be used as an early index to predict a functional cure in CHB patients treated with PEGylated interferon.

The Hepatitis B Virus Interactome: A Comprehensive Overview

Despite the availability of a prophylactic vaccine, chronic hepatitis B (CHB) caused by the hepatitis B virus (HBV) is a major health problem affecting an estimated 292 million people globally. Current therapeutic goals are to achieve functional cure characterized by HBsAg seroclearance and the absence of HBV-DNA after treatment cessation. However, at present, functional cure is thought to be complicated due to the presence of covalently closed circular DNA (cccDNA) and integrated HBV-DNA. Even if the episomal cccDNA is silenced or eliminated, it remains unclear how important the high level of HBsAg that is expressed from integrated HBV DNA is for the pathology. To identify therapies that could bring about high rates of functional cure, in-depth knowledge of the virus' biology is imperative to pinpoint mechanisms for novel therapeutic targets. The viral proteins and the episomal cccDNA are considered integral for the control and maintenance of the HBV life cycle and through direct interaction with the host proteome they help create the most optimal environment for the virus whilst avoiding immune detection. New HBV-host protein interactions are continuously being identified. Unfortunately, a compendium of the most recent information is lacking and an interactome is unavailable. This article provides a comprehensive review of the virus-host relationship from viral entry to release, as well as an interactome of cccDNA, HBc, and HBx.

Immunity and Viral Infections: Modulating Antiviral Response via CRISPR-Cas Systems

Viral infections cause a variety of acute and chronic human diseases, sometimes resulting in small local outbreaks, or in some cases spreading across the globe and leading to global pandemics. Understanding and exploiting virus-host interactions is instrumental for identifying host factors involved in viral replication, developing effective antiviral agents, and mitigating the severity of virus-borne infectious diseases. The diversity of CRISPR systems and CRISPR-based tools enables the specific modulation of innate immune responses and has contributed impressively to the fields of virology and immunology in a very short time. In this review, we describe the most recent advances in the use of CRISPR systems for basic and translational studies of virus-host interactions.

Interferon-induced degradation of the persistent hepatitis B virus cccDNA form depends on ISG20

Hepatitis B virus (HBV) persists by depositing a covalently closed circular DNA (cccDNA) in the nucleus of infected cells that cannot be targeted by available antivirals. Interferons can diminish HBV cccDNA via APOBEC3-mediated deamination. Here, we show that overexpression of APOBEC3A alone is not sufficient to reduce HBV cccDNA that requires additional treatment of cells with interferon indicating involvement of an interferon-stimulated gene (ISG) in cccDNA degradation. Transcriptome analyses identify ISG20 as the only type I and II interferon-induced, nuclear protein with annotated nuclease activity. ISG20 localizes to nucleoli of interferon-stimulated hepatocytes and is enriched on deoxyuridine-containing single-stranded DNA that mimics transcriptionally active, APOBEC3A-deaminated HBV DNA. ISG20 expression is detected in human livers in acute, self-limiting but not in chronic hepatitis B. ISG20 depletion mitigates the interferon-induced loss of cccDNA, and co-expression with APOBEC3A is sufficient to diminish cccDNA. In conclusion, non-cytolytic HBV cccDNA decline requires the concerted action of a deaminase and a nuclease. Our findings highlight that ISGs may cooperate in their antiviral activity that may be explored for therapeutic targeting.

Cross talk between hepatitis B virus and innate immunity of hepatocytes

Innate immunity plays a major role in controlling viral infections. Recent exploration of sodium taurocholate co-transporting polypeptide receptor as specific hepatitis B virus (HBV) receptor in human hepatocytes has provided appropriate cell culture tools to study the innate immunity of hepatocytes and its cross talk with HBV. In this review, we give a brief update on interaction between HBV and innate immunity using the currently available in vitro cellular models that support the complete life cycle of HBV. We will discuss how HBV can act as a 'stealth' virus to counteract the innate immune responses mediated by the pathogen recognition receptors of hepatocytes and escape the first line of surveillance of the host immune system. We give an overview of the cellular components of innate immunity that present in these in vitro models and discuss how activating these innate immunity components may contribute to the eradication of HBV infection.

Potential capacity of interferon-α to eliminate covalently closed circular DNA (cccDNA) in hepatocytes infected with hepatitis B virus

Interferon-alpha (IFN-α) and nucleot(s)ide analogs (NAs) are first-line drugs for the treatment of chronic hepatitis B virus (HBV) infections. Generally, NAs target the reverse transcription of HBV pregenomic RNA, but they cannot eliminate covalently-closed-circular DNA (cccDNA). Although effective treatment with NAs can dramatically decrease HBV proteins and DNA loads, and even promote serological conversion, cccDNA persists in the nucleus of hepatocytes due to the lack of effective anti-cccDNA drugs. Of the medications currently available, only IFN-α can potentially target cccDNA. However, the clinical effects of eradicating cccDNA using IFN-α in the hepatocytes of patients with HBV are not proficient as well as expected and are not well understood. Herein, we review the anti-HBV mechanisms of IFN-α involving cccDNA modification as the most promising approaches to cure HBV infection. We expect to find indications of promising areas of research that require further study to eliminate cccDNA of HBV in patients.

Deaminase-Independent Mode of Antiretroviral Action in Human and Mouse APOBEC3 Proteins

Apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3 (APOBEC3) proteins (APOBEC3s) are deaminases that convert cytosines to uracils predominantly on a single-stranded DNA, and function as intrinsic restriction factors in the innate immune system to suppress replication of viruses (including retroviruses) and movement of retrotransposons. Enzymatic activity is supposed to be essential for the APOBEC3 antiviral function. However, it is not the only way that APOBEC3s exert their biological function. Since the discovery of human APOBEC3G as a restriction factor for HIV-1, the deaminase-independent mode of action has been observed. At present, it is apparent that both the deaminase-dependent and -independent pathways are tightly involved not only in combating viruses but also in human tumorigenesis. Although the deaminase-dependent pathway has been extensively characterized so far, understanding of the deaminase-independent pathway remains immature. Here, we review existing knowledge regarding the deaminase-independent antiretroviral functions of APOBEC3s and their molecular mechanisms. We also discuss the possible unidentified molecular mechanism for the deaminase-independent antiretroviral function mediated by mouse APOBEC3.

Insights for clinical diagnostic indicators of virus and host in chronic hepatitis B infection

Covalently closed circular DNA (cccDNA), which is stably present in the nucleus of hepatocytes, is an important indicator for evaluating antiviral efficacy. Since cccDNA quantification requires an invasive procedure, serum biological markers that can effectively reflect the transcriptional activity of intrahepatic virus and the efficacy of treatment are required. Here, from the aspects of virus and host, we outline the focus of clinical research of HBV in recent years, including HBV RNA, empty virus, hepatitis B core-related antigen and changes in the immune response. We briefly discuss their significance in predicting disease activity and monitoring treatment response in chronic hepatitis B. On this basis, some issues worthy of attention in laboratory diagnosis are proposed.

Replenishment of Hepatitis B Virus cccDNA Pool Is Restricted by Baseline Expression of Host Restriction Factors In Vitro

BACKGROUND

Covalently closed circular DNA (cccDNA) of hepatitis B virus (HBV) is the major cause of viral persistence in patients with chronic HBV infection. Understanding the mechanisms underlying stability and persistence of HBV cccDNA in hepatocytes is critical for developing novel therapeutics and managing chronic hepatitis B. In this study, we observed an unexpected increase in HBV cccDNA levels upon suppression of transcription by de novo DNA methyltransferase DNMT3A and uncovered additional mechanisms potentially involved in HBV cccDNA maintenance.

METHODS

HBV-expressing cell lines were transfected with a DNMT3A-expressing plasmid. Real-time PCR and HBsAg assays were used to assess the HBV replication rate. Cell cycling was analyzed by fluorescent cell sorting. CRISPR/Cas9 was utilized to abrogate expression of APOBEC3A and APOBEC3B. Alterations in the expression of target genes were measured by real-time PCR.

RESULTS

Similar to previous studies, HBV replication induced DNMT3A expression, which in turn, led to reduced HBV transcription but elevated HBV cccDNA levels (4- to 6-fold increase). Increased levels of HBV cccDNA were not related to cell cycling, as DNMT3A accelerated proliferation of infected cells and could not contribute to HBV cccDNA expansion by arresting cells in a quiescent state. At the same time, DNMT3A suppressed transcription of innate immunity factors including cytidine deaminases APOBEC3A and APOBEC3B. CRISPR/Cas9-mediated silencing of APOBEC3A and APOBEC3B transcription had minor effects on HBV transcription, but significantly increased HBV cccDNA levels, similar to DNMT3A. In an attempt to further analyze the detrimental effects of HBV and DNMT3A on infected cells, we visualized γ-H2AX foci and demonstrated that HBV inflicts and DNMT3A aggravates DNA damage, possibly by downregulating DNA damage response factors. Additionally, suppression of HBV replication by DNMT3A may be related to reduced ATM/ATR expression.

CONCLUSION

Formation and maintenance of HBV cccDNA pools may be partially suppressed by the baseline expression of host inhibitory factors including APOBEC3A and APOBEC3B. HBV inflicts DNA damage both directly and by inducing DNMT3A expression.

An Immortalized Hepatocyte-like Cell Line (imHC) Accommodated Complete Viral Lifecycle, Viral Persistence Form, cccDNA and Eventual Spreading of a Clinically-Isolated HBV

More than 350 million people worldwide have been persistently infected with the hepatitis B virus (HBV). Chronic HBV infection could advance toward liver cirrhosis and hepatocellular carcinoma. The intervention with prophylactic vaccine and conventional treatment could suppress HBV, but could not completely eradicate it. The major obstacle for investigating curative antiviral drugs are the incompetence of hepatocyte models that should have closely imitated natural human infection. Here, we demonstrated that an immortalized hepatocyte-like cell line (imHC) could accommodate for over 30 days the entire life cycle of HBV prepared from either established cultured cells or clinically-derived fresh isolates. Normally, imHCs had intact interferon signaling with anti-viral action. Infected imHCs responded to treatments with direct-acting antiviral drugs (DAAs) and interferons (IFNs) by diminishing HBV DNA, the covalently closed circular DNA (cccDNA) surface antigen of HBV (HBsAg, aka the Australia antigen) and the hepatitis B viral protein (HBeAg). Notably, we could observe and quantify HBV spreading from infected cells to naïve cells using an imHC co-culture model. In summary, this study constructed a convenient HBV culture model that allows the screening for novel anti-HBV agents with versatile targets, either HBV entry, replication or cccDNA formation. Combinations of agents aiming at different targets should achieve a complete HBV eradication.

Revisiting Hepatitis B Virus: Challenges of Curative Therapies

With a yearly death toll of 880,000, hepatitis B virus (HBV) remains a major health problem worldwide, despite an effective prophylactic vaccine and well-tolerated, effective antivirals. HBV causes chronic hepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. The viral genome persists in infected hepatocytes even after long-term antiviral therapy, and its integration, though no longer able to support viral replication, destabilizes the host genome. HBV is a DNA virus that utilizes a virus-encoded reverse transcriptase to convert an RNA intermediate, termed pregenomic RNA, into the relaxed circular DNA genome, which is subsequently converted into a covalently closed circular DNA (cccDNA) in the host cell nucleus. cccDNA is maintained in the nucleus of the infected hepatocyte as a stable minichromosome and functions as the viral transcriptional template for the production of all viral gene products, and thus, it is the molecular basis of HBV persistence. The nuclear cccDNA pool can be replenished through recycling of newly synthesized, DNA-containing HBV capsids. Licensed antivirals target the HBV reverse transcriptase activity but fail to eliminate cccDNA, which would be required to cure HBV infection. Elimination of HBV cccDNA is so far only achieved by antiviral immune responses. Thus, this review will focus on possible curative strategies aimed at eliminating or crippling the viral cccDNA. Newer insights into the HBV life cycle and host immune response provide novel, potentially curative therapeutic opportunities and targets.

Distribution and difference of APOBEC-induced mutations in the TpCpW context of HBV DNA between HCC and non-HCC

Hepatitis B virus (HBV) DNA is vulnerable to editing by human apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like (APOBEC) cytidine deaminases. However, the distribution of APOBEC-induced mutations on HBV DNA is not well characterized. To this end, we obtained the HBV DNA sequence of HBV-infected individuals with and without hepatocellular carcinoma (HCC and non-HCC groups, respectively) from NCBI database and calculated the r_apo values of APOBEC-induced TpCpW→TpKpW mutation prevalence in HBV DNA. The results showed that the APOBEC-induced mutations were mainly distributed in the minus strand of non-HCC-derived HBV DNA (r_apo  = 2.04), while the mutation on the plus-strand was weaker (r_apo  = 0.99). There were high APOBEC-induced mutation regions in the minus strand of HBV DNA 1 to 1000 nucleotides (nts) region and in the plus-strand of HBV DNA 1000 to 1500 nts region; the mutations in the 1 to 1000 nts region were mainly TpCpW→TpTpW mutation types (total T/G: 111/18) and a number of these were missense mutations (missense/synonymous: 35/94 in P gene, 17/15 in S gene, and 5/10 in X gene). The difference between minus to plus-strand r_apo of HCC-derived HBV DNA (1.96) was greater than that of the non-HCC group (1.05). The minus-strand r_apo of HCC-derived HBV DNA regions 1000 to1500nts and 1500 to 2000 nts (r_apo = 4.2 and 4.2) was also higher than that of the same regions of non-HCC-derived HBV DNA (r_apo  = 1.2 and 1.1). Finally, the ratio of minus to plus-strand r_apo was used to distinguish HCC-derived HBV DNA from non-HCC-derived HBV DNA. This study unraveled the distribution characteristics of APOBEC-induced mutations on double strands of HBV DNA from HCC and non-HCC samples. Our findings would help understand the mechanism of APOBECs on HBV DNA and may provide important insights for the screening of HCC.

AID recruits the RNA exosome to degrade HIV-1 nascent transcripts through interaction with the Tat-P-TEFb-TAR RNP complex

Activation-induced cytidine deaminase (AID), a member of the APOBEC family that induces antibody diversification, has been shown to inhibit the replication of hepatitis B virus, Kaposi's sarcoma-associated herpesvirus, and retro-transposons. However, whether AID can inhibit human immunodeficiency virus 1 (HIV-1) replication remains unclear. Here, we report that AID impairs the synthesis of HIV-1 components by interacting with the complex of Tat. This interaction recruits the RNA exosome to degrade the nascent HIV-1 transcript. AID also targets the HIV-1-integrated genome via the Tat-P-TEFb-TAR complex. Thus, we propose a novel function for AID as an adaptor protein that represses viral transcription. Our findings provide insights into developing anti-HIV therapeutics and understanding how host cells restrict integrated virus replication.

Advanced Strategies for Eliminating the cccDNA of HBV

Persistent hepatitis B virus (HBV) infection of hepatocytes is associated with a covalently closed circular DNA (cccDNA) episome. Although serologic hepatitis B surface antigen tests are negative, the presence of cccDNA is obviously increased in HBeAg-positive patients compared with that in HBeAg-negative patients, inactive carriers and patients. Moreover, trace cccDNA levels can also be found in the liver cells of patients with resolved hepatitis B infections. Therefore, clearance of cccDNA in hepatocytes could be an effective cure for HBV. In this review, we summarize the strategies that have been employed to eliminate cccDNA in recent years and discuss the future development of treatments for chronic hepatitis B.

Alteration of microRNA profiles by a novel inhibitor of human La protein in HBV-transformed human hepatoma cells

A pyrazolopyridine HBSC11 was previously identified as a novel inhibitor of human La protein with anti‐hepatitis B virus (HBV) activity. However, the underlying mechanism(s) of HBV inhibition by HBSC11 remains unclear. This study aimed to examine the regulation of microRNA (miRNA) by HBSC11 in HBV‐transformed human hepatoma HepG2.2.15 cells using microarray and quantitative real‐time PCR. Target genes of the differentially expressed miRNAs were predicted and subjected to bioinformatics analysis. Results showed that HBSC11 significantly upregulated the expression of miR‐3912‐5p, miR‐6793‐5p, and miR‐7159‐5p in HepG2.2.15 cells. Target genes of the three miRNAs were mainly involved in the regulation of nucleic acid‐templated transcription, negative regulation of gene expression, nucleic acid binding transcription factor activity and regulation of phosphorylation. In addition, target genes were enriched in certain regulatory pathways related to HBV infection and HBV‐associated disease progression, such as the transforming growth factor (TGF)‐β, Wnt, and p53 signaling. Our study demonstrates the involvement of miR‐3912‐5p, miR‐6793‐5p, and miR‐7159‐5p and the potential modulation of specific pathways (TGF‐β, Wnt, and p53 signaling) in HBSC11‐mediated inhibition of HBV replication. This study provides insight into the molecular mechanism of the action of HBSC11 against HBV infection and will support the development of antiviral drugs targeting La protein.

Immune Evasion Strategies during Chronic Hepatitis B and C Virus Infection

Both hepatitis B virus (HBV) and hepatitis C virus (HCV) infections are a major global healthcare problem with more than 240 million and 70 million infected, respectively. Both viruses persist within the liver and result in progressive liver disease, resulting in liver fibrosis, cirrhosis and hepatocellular carcinoma. Strikingly, this pathogenesis is largely driven by immune responses, unable to clear an established infection, rather than by the viral pathogens themselves. Even though disease progression is very similar in both infections, HBV and HCV have evolved distinct mechanisms, by which they ensure persistence within the host. Whereas HCV utilizes a cloak-and-dagger approach, disguising itself as a lipid-like particle and immediately crippling essential pattern-recognition pathways, HBV has long been considered a "stealth" virus, due to the complete absence of innate immune responses during infection. Recent developments and access to improved model systems, however, revealed that even though it is among the smallest human-tropic viruses, HBV may, in addition to evading host responses, employ subtle immune evasion mechanisms directed at ensuring viral persistence in the absence of host responses. In this review, we compare the different strategies of both viruses to ensure viral persistence by actively interfering with viral recognition and innate immune responses.

Circular RNAs: Regulators of Cancer-Related Signaling Pathways and Potential Diagnostic Biomarkers for Human Cancers

Circular RNAs (circRNAs) are newly discovered endogenous non-coding RNAs featuring structural stability, high abundance, and tissue-specific expression. CircRNAs are prevalent and conserved in mammalian cells. They are involved in cellular processes and regulate gene expression at the transcriptional or post-transcriptional level by interacting with microRNAs (miRNAs) and other molecules. Recent studies have shown that circRNAs play an important role in the progression of various human diseases including atherosclerosis, nervous system disorders, diabetes, and cancer. In this review, we summarize the advances on endogenous circRNAs in eukaryotic cells and elucidate their diagnostic and prognostic significance in human cancers. Especially, we highlight the involvement of circRNAs in signal transduction pathways as well as their clinical potential to serve as biomarkers.

Control of Hepatitis B Virus by Cytokines

Hepatitis B virus (HBV) infection remains a major public health problem worldwide with more than 240 million individuals chronically infected. Current treatments can control HBV replication to a large extent, but cannot eliminate HBV infection. Cytokines have been shown to control HBV replication and contribute to HBV cure in different models. Cytokines play an important role in limiting acute HBV infection in patients and mediate a non-cytolytic clearance of the virus. In this review, we summarize the effects of cytokines and cytokine-induced cellular signaling pathways on different steps of the HBV life cycle, and discuss possible strategies that may contribute to the eradication of HBV through innate immune activation.