1 3806 157 INTRACELLULAR INTERFERON SIGNALLING PATHWAYS AS POTENTIAL REGULATORS OF COVALENTLY CLOSED CIRCULAR DNA IN THE TREATMENT OF CHRONIC HEPATITIS B. INFECTION WITH THE HEPATITIS B VIRUS (HBV) IS STILL A MAJOR GLOBAL HEALTH THREAT AS 250 MILLION PEOPLE WORLDWIDE CONTINUE TO BE CHRONICALLY INFECTED WITH THE VIRUS. WHILE PATIENTS MAY BE TREATED WITH NUCLEOSIDE/NUCLEOTIDE ANALOGUES, THIS ONLY SUPPRESSES HBV TITRE TO SUB-DETECTION LEVELS WITHOUT ELIMINATING THE PERSISTENT HBV COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) GENOME. AS A RESULT, HBV INFECTION CANNOT BE CURED, AND THE VIRUS REACTIVATES WHEN CONDITIONS ARE FAVORABLE. INTERFERONS (IFNS) ARE CYTOKINES KNOWN TO INDUCE POWERFUL ANTIVIRAL MECHANISMS THAT CLEAR VIRUSES FROM INFECTED CELLS. THEY HAVE BEEN SHOWN TO INDUCE CCCDNA CLEARANCE, BUT THEIR USE IN THE TREATMENT OF HBV INFECTION IS LIMITED AS HBV-TARGETING IMMUNE CELLS ARE EXHAUSTED AND HBV HAS EVOLVED MULTIPLE MECHANISMS TO EVADE AND SUPPRESS IFN SIGNALLING. THUS, TO FULLY UTILIZE IFN-MEDIATED INTRACELLULAR MECHANISMS TO EFFECTIVELY ELIMINATE HBV, INSTEAD OF DIRECT IFN ADMINISTRATION, NOVEL STRATEGIES TO SUSTAIN IFN-MEDIATED ANTI-CCCDNA AND ANTIVIRAL MECHANISMS NEED TO BE DEVELOPED. THIS REVIEW WILL CONSOLIDATE WHAT IS KNOWN ABOUT HOW IFNS ACT TO ACHIEVE ITS INTRACELLULAR ANTIVIRAL EFFECTS AND HIGHLIGHT THE CRITICAL INTERFERON-STIMULATED GENE TARGETS AND EFFECTOR MECHANISMS WITH POTENT ANTI-CCCDNA FUNCTIONS. THESE INCLUDE CCCDNA DEGRADATION BY APOBECS AND CCCDNA SILENCING AND TRANSCRIPTION REPRESSION BY EPIGENETIC MODIFICATIONS. IN ADDITION, THE MECHANISMS THAT HBV EMPLOYS TO DISRUPT IFN SIGNALLING WILL BE DISCUSSED. DRUGS THAT HAVE BEEN DEVELOPED OR ARE IN THE PIPELINE FOR COMPONENTS OF THE IFN SIGNALLING PATHWAY AND HBV TARGETS THAT DETRACT IFN SIGNALLING MECHANISMS WILL ALSO BE IDENTIFIED AND DISCUSSED FOR UTILITY IN THE TREATMENT OF HBV INFECTIONS. TOGETHER, THESE WILL PROVIDE USEFUL INSIGHTS INTO DESIGN STRATEGIES THAT SPECIFICALLY TARGET CCCDNA FOR THE ERADICATION OF HBV. 2021 2 6115 42 THE EPIGENETIC CONTROL OF HEPATITIS B VIRUS MODULATES THE OUTCOME OF INFECTION. EPIGENETIC MODIFICATIONS ARE STABLE ALTERATIONS IN GENE EXPRESSION THAT DO NOT INVOLVE MUTATIONS OF THE GENETIC SEQUENCE ITSELF. IT HAS BECOME INCREASINGLY CLEAR THAT EPIGENETIC FACTORS CONTRIBUTE TO THE OUTCOME OF CHRONIC HEPATITIS B VIRUS (HBV) INFECTION BY AFFECTING CELLULAR AND VIRION GENE EXPRESSION, VIRAL REPLICATION AND THE DEVELOPMENT OF HEPATOCELLULAR CARCINOMA. HBV PERSISTS IN THE NUCLEUS OF INFECTED HEPATOCYTES AS A STABLE NON-INTEGRATED COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) WHICH FUNCTIONS AS A MINICHROMOSOME. THERE ARE TWO MAJOR FORMS OF HBV EPIGENETIC REGULATION: POSTTRANSLATIONAL MODIFICATION OF HISTONE PROTEINS ASSOCIATED WITH THE CCCDNA MINICHROMOSOME AND DNA METHYLATION OF VIRAL AND HOST GENOMES. THIS REVIEW EXPLORES HOW HBV CAN INTERPHASE WITH HOST EPIGENETIC REGULATION IN ORDER TO EVADE HOST DEFENCES AND TO PROMOTE ITS OWN SURVIVAL AND PERSISTENCE. WE FOCUS ON THE EFFECT OF CCCDNA BOUND-HISTONE MODIFICATIONS AND THE METHYLATION STATUS OF HBV DNA IN REGULATING VIRAL REPLICATION. INVESTIGATION OF HBV EPIGENETIC CONTROL HAS IMPORTANT CLINICAL CORRELATES WITH REGARDS TO THE DEVELOPMENT OF POTENTIAL THERAPEUTIC REGIMENS THAT WILL SUCCESSFULLY ERADICATE HBV INFECTION AND DEAL WITH HBV REACTIVATION IN THOSE UNDERGOING TREATMENT WITH DEMETHYLATING AGENTS. 2015 3 2240 50 EPIGENETIC MODULATION IN CHRONIC HEPATITIS B VIRUS INFECTION. THE HUMAN HEPATITIS B VIRUS (HBV) IS A SMALL-ENVELOPED DNA VIRUS CAUSING ACUTE AND CHRONIC HEPATITIS. DESPITE THE EXISTENCE OF AN EFFECTIVE PROPHYLACTIC VACCINE AND THE STRONG CAPACITY OF APPROVED ANTIVIRAL DRUGS TO SUPPRESS VIRAL REPLICATION, CHRONIC HBV INFECTION (CHB) CONTINUES TO BE A MAJOR HEALTH BURDEN WORLDWIDE. BOTH THE INABILITY OF THE IMMUNE SYSTEM TO RESOLVE CHB AND THE UNIQUE REPLICATION STRATEGY EMPLOYED BY HBV, WHICH FORMS A STABLE VIRAL COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) MINICHROMOSOME IN THE HEPATOCYTE NUCLEUS, ENABLE INFECTION PERSISTENCE. KNOWLEDGE OF THE COMPLEX NETWORK OF INTERACTIONS THAT HBV ENGAGES WITH ITS HOST IS STILL LIMITED BUT ACCUMULATING EVIDENCE INDICATES THAT EPIGENETIC MODIFICATIONS OCCURRING BOTH ON THE CCCDNA AND ON THE HOST GENOME IN THE COURSE OF INFECTION ARE ESSENTIAL TO MODULATE VIRAL ACTIVITY AND LIKELY CONTRIBUTE TO PATHOGENESIS AND CANCER DEVELOPMENT. THUS, A DEEPER UNDERSTANDING OF EPIGENETIC REGULATORY PROCESSES MAY OPEN NEW VENUES TO CONTROL AND EVENTUALLY CURE CHB. THIS REVIEW SUMMARIZES MAJOR FINDINGS IN HBV EPIGENETIC RESEARCH, FOCUSING ON THE EPIGENETIC MECHANISMS REGULATING CCCDNA ACTIVITY AND THE MODIFICATIONS DETERMINED IN INFECTED HOST CELLS AND TUMOR LIVER TISSUES. 2020 4 5368 37 RECENT ADVANCES IN THE STUDY OF HEPATITIS B VIRUS COVALENTLY CLOSED CIRCULAR DNA. CHRONIC HEPATITIS B INFECTION IS CAUSED BY HEPATITIS B VIRUS (HBV) AND A TOTAL CURE IS YET TO BE ACHIEVED. THE VIRAL COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) IS THE KEY TO ESTABLISH A PERSISTENT INFECTION WITHIN HEPATOCYTES. CURRENT ANTIVIRAL STRATEGIES HAVE NO EFFECT ON THE PRE-EXISTING CCCDNA RESERVOIR. THEREFORE, THE STUDY OF THE MOLECULAR MECHANISM OF CCCDNA FORMATION IS BECOMING A MAJOR FOCUS OF HBV RESEARCH. THIS REVIEW SUMMARIZES THE CURRENT ADVANCES IN CCCDNA MOLECULAR BIOLOGY AND THE LATEST STUDIES ON THE ELIMINATION OR INACTIVATION OF CCCDNA, INCLUDING THREE MAJOR AREAS: (1) EPIGENETIC REGULATION OF CCCDNA BY HBV X PROTEIN, (2) IMMUNE-MEDIATED DEGRADATION, AND (3) GENOME-EDITING NUCLEASES. ALL THESE ASPECTS PROVIDE CLUES ON HOW TO FINALLY ATTAIN A CURE FOR CHRONIC HEPATITIS B INFECTION. 2017 5 5952 52 TARGETING VIRAL CCCDNA FOR CURE OF CHRONIC HEPATITIS B. PURPOSE OF REVIEW: CHRONIC HEPATITIS B (CHB), CAUSED BY HEPATITIS B VIRUS (HBV), IS A MAJOR CAUSE OF ADVANCED LIVER DISEASE AND HEPATOCELLULAR CARCINOMA (HCC) WORLDWIDE. HBV REPLICATION IS CHARACTERIZED BY THE SYNTHESIS OF COVALENTLY CLOSED CIRCULAR (CCC) DNA WHICH IS NOT TARGETED BY ANTIVIRAL NUCLEOS(T)IDE ANALOGUES (NUCS) THE KEY MODALITY OF STANDARD OF CARE. WHILE HBV REPLICATION IS SUCCESSFULLY SUPPRESSED IN TREATED PATIENTS, THEY REMAIN AT RISK FOR DEVELOPING HCC. WHILE FUNCTIONAL CURE, CHARACTERIZED BY LOSS OF HBSAG, IS THE FIRST GOAL OF NOVEL ANTIVIRAL THERAPIES, CURATIVE TREATMENTS ELIMINATING CCCDNA REMAIN THE ULTIMATE GOAL. THIS REVIEW SUMMARIZES RECENT ADVANCES IN THE DISCOVERY AND DEVELOPMENT OF NOVEL THERAPEUTIC STRATEGIES AND THEIR IMPACT ON CCCDNA BIOLOGY. RECENT FINDINGS: WITHIN THE LAST DECADE, SUBSTANTIAL PROGRESS HAS BEEN MADE IN THE UNDERSTANDING OF CCCDNA BIOLOGY INCLUDING THE DISCOVERY OF HOST DEPENDENCY FACTORS, EPIGENETIC REGULATION OF CCCDNA TRANSCRIPTION AND IMMUNE-MEDIATED DEGRADATION. SEVERAL APPROACHES TARGETING CCCDNA EITHER IN A DIRECT OR INDIRECT MANNER ARE CURRENTLY AT THE STAGE OF DISCOVERY, PRECLINICAL OR EARLY CLINICAL DEVELOPMENT. EXAMPLES INCLUDE GENOME-EDITING APPROACHES, STRATEGIES TARGETING HOST DEPENDENCY FACTORS OR EPIGENETIC GENE REGULATION, NUCLEOCAPSID MODULATORS AND IMMUNE-MEDIATED DEGRADATION. SUMMARY: WHILE DIRECT-TARGETING CCCDNA STRATEGIES ARE STILL LARGELY AT THE PRECLINICAL STAGE OF DEVELOPMENT, CAPSID ASSEMBLY MODULATORS AND IMMUNE-BASED APPROACHES HAVE REACHED THE CLINICAL PHASE. CLINICAL TRIALS ARE ONGOING TO ASSESS THEIR EFFICACY AND SAFETY IN PATIENTS INCLUDING THEIR IMPACT ON VIRAL CCCDNA. COMBINATION THERAPIES PROVIDE ADDITIONAL OPPORTUNITIES TO OVERCOME CURRENT LIMITATIONS OF INDIVIDUAL APPROACHES. 2020 6 5547 45 ROLE OF EPIGENETIC MODIFICATION IN INTERFERON TREATMENT OF HEPATITIS B VIRUS INFECTION. HUMAN HEPATITIS B VIRUS (HBV) IS A SMALL, ENVELOPED DNA VIRUS THAT CAUSES ACUTE AND CHRONIC HEPATITIS. CHRONIC HEPATITIS B (CHB) IS ASSOCIATED WITH HEPATOCELLULAR CARCINOMA PATHOGENESIS. INTERFERONS (IFNS) HAVE BEEN USED FOR THE TREATMENT OF CHB FOR A LONG TIME, WITH ADVANTAGES INCLUDING LESS TREATMENT DURATION AND SUSTAINED VIROLOGICAL RESPONSE. PRESENTLY, VARIOUS EVIDENCE SUGGESTS THAT EPIGENETIC MODIFICATION OF THE VIRAL COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) AND THE HOST GENOME IS CRUCIAL FOR THE REGULATION OF VIRAL ACTIVITY. THIS MODIFICATION INCLUDES HISTONE ACETYLATION, DNA METHYLATION, N6-METHYLADENOSINE, AND NON-CODING RNA MODIFICATION. IFN TREATMENT FOR CHB CAN STIMULATE MULTIPLE IFN-STIMULATED GENES FOR INHIBITING VIRUS REPLICATION. IFNS CAN ALSO AFFECT THE HBV LIFE CYCLE THROUGH EPIGENETIC MODULATION. IN THIS REVIEW, WE SUMMARIZED THE DIFFERENT MECHANISMS THROUGH WHICH IFN-ALPHA INHIBITS HBV REPLICATION, INCLUDING EPIGENETIC REGULATION. MOREOVER, THE MECHANISMS UNDERLYING IFN ACTIVITY ARE DISCUSSED, WHICH INDICATED ITS POTENTIAL AS A NOVEL TREATMENT FOR CHB. IT IS PROPOSED THAT EPIGENETIC CHANGES SUCH AS HISTONE ACETYLATION, DNA METHYLATION, M6A METHYLATION COULD BE THE TARGETS OF IFN, WHICH MAY OFFER A NOVEL APPROACH TO HBV TREATMENT. 2022 7 1178 38 CONTROL OF CCCDNA FUNCTION IN HEPATITIS B VIRUS INFECTION. THE TEMPLATE OF HEPATITIS B VIRUS (HBV) TRANSCRIPTION, THE COVALENTLY CLOSED CIRCULAR DNA (CCCDNA), PLAYS A KEY ROLE IN THE LIFE CYCLE OF THE VIRUS AND PERMITS THE PERSISTENCE OF INFECTION. NOVEL MOLECULAR TECHNIQUES HAVE OPENED NEW POSSIBILITIES TO INVESTIGATE THE ORGANIZATION AND THE ACTIVITY OF THE CCCDNA MINICHROMOSOME IN VIVO, AND RECENT ADVANCES HAVE STARTED TO SHED LIGHT ON THE COMPLEXITY OF THE MECHANISMS CONTROLLING CCCDNA FUNCTION. NUCLEAR CCCDNA ACCUMULATES IN HEPATOCYTE NUCLEI AS A STABLE MINICHROMOSOME ORGANIZED BY HISTONE AND NON-HISTONE VIRAL AND CELLULAR PROTEINS. IDENTIFICATION OF THE MOLECULAR MECHANISMS REGULATING CCCDNA STABILITY AND ITS TRANSCRIPTIONAL ACTIVITY AT THE RNA, DNA AND EPIGENETIC LEVELS IN THE COURSE OF CHRONIC HEPATITIS B (CH-B) INFECTION MAY REVEAL NEW POTENTIAL THERAPEUTIC TARGETS FOR ANTI-HBV DRUGS AND HENCE ASSIST IN THE DESIGN OF STRATEGIES AIMED AT SILENCING AND EVENTUALLY DEPLETING THE CCCDNA RESERVOIR. 2009 8 5689 53 SILENCING HEPATITIS B VIRUS COVALENTLY CLOSED CIRCULAR DNA: THE POTENTIAL OF AN EPIGENETIC THERAPY APPROACH. GLOBAL PROPHYLACTIC VACCINATION PROGRAMMES HAVE HELPED TO CURB NEW HEPATITIS B VIRUS (HBV) INFECTIONS. HOWEVER, IT IS ESTIMATED THAT NEARLY 300 MILLION PEOPLE ARE CHRONICALLY INFECTED AND HAVE A HIGH RISK OF DEVELOPING HEPATOCELLULAR CARCINOMA. AS SUCH, HBV REMAINS A SERIOUS HEALTH PRIORITY AND THE DEVELOPMENT OF NOVEL CURATIVE THERAPEUTICS IS URGENTLY NEEDED. CHRONIC HBV INFECTION HAS BEEN ATTRIBUTED TO THE PERSISTENCE OF THE COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) WHICH ESTABLISHES ITSELF AS A MINICHROMOSOME IN THE NUCLEUS OF HEPATOCYTES. AS THE VIRAL TRANSCRIPTION INTERMEDIATE, THE CCCDNA IS RESPONSIBLE FOR PRODUCING NEW VIRIONS AND PERPETUATING INFECTION. HBV IS DEPENDENT ON VARIOUS HOST FACTORS FOR CCCDNA FORMATION AND THE MINICHROMOSOME IS AMENABLE TO EPIGENETIC MODIFICATIONS. TWO HBV PROTEINS, X (HBX) AND CORE (HBC) PROMOTE VIRAL REPLICATION BY MODULATING THE CCCDNA EPIGENOME AND REGULATING HOST CELL RESPONSES. THIS INCLUDES VIRAL AND HOST GENE EXPRESSION, CHROMATIN REMODELING, DNA METHYLATION, THE ANTIVIRAL IMMUNE RESPONSE, APOPTOSIS, AND UBIQUITINATION. ELIMINATION OF THE CCCDNA MINICHROMOSOME WOULD RESULT IN A STERILIZING CURE; HOWEVER, THIS MAY BE DIFFICULT TO ACHIEVE. EPIGENETIC THERAPIES COULD PERMANENTLY SILENCE THE CCCDNA MINICHROMOSOME AND PROMOTE A FUNCTIONAL CURE. THIS REVIEW EXPLORES THE CCCDNA EPIGENOME, HOW HOST AND VIRAL FACTORS INFLUENCE TRANSCRIPTION, AND THE RECENT EPIGENETIC THERAPIES AND EPIGENOME ENGINEERING APPROACHES THAT HAVE BEEN DESCRIBED. 2021 9 2324 38 EPIGENETIC REGULATION OF HEPATITIS B VIRUS COVALENTLY CLOSED CIRCULAR DNA: IMPLICATIONS FOR EPIGENETIC THERAPY AGAINST CHRONIC HEPATITIS B. HEPATITIS B VIRUS (HBV) INFECTION REPRESENTS A SIGNIFICANT PUBLIC HEALTH BURDEN WORLDWIDE. ALTHOUGH CURRENT THERAPEUTICS MANAGE TO CONTROL THE DISEASE PROGRESSION, LIFELONG TREATMENT AND SURVEILLANCE ARE REQUIRED BECAUSE DRUG RESISTANCE DEVELOPS DURING TREATMENT AND REACTIVATIONS FREQUENTLY OCCUR FOLLOWING MEDICATION CESSATION. THUS, THE OCCURRENCE OF HEPATOCELLULAR CARCINOMA IS DECREASED, BUT NOT ELIMINATED. ONE MAJOR REASON FOR FAILURE OF HBV TREATMENT IS THE INABILITY TO ERADICATE OR INACTIVATE THE VIRAL COVALENTLY CLOSED CIRCULAR DNA (CCCDNA), WHICH IS A STABLE EPISOMAL FORM OF THE VIRAL GENOME DECORATED WITH HOST HISTONES AND NONHISTONE PROTEINS. ACCUMULATING EVIDENCE SUGGESTS THAT EPIGENETIC MODIFICATIONS OF CCCDNA CONTRIBUTE TO VIRAL REPLICATION AND THE OUTCOME OF CHRONIC HBV INFECTION. HERE, WE SUMMARIZE CURRENT PROGRESS ON HBV EPIGENETICS RESEARCH AND THE THERAPEUTIC IMPLICATIONS FOR CHRONIC HBV INFECTION BY LEARNING FROM THE EPIGENETIC THERAPIES FOR CANCER AND OTHER VIRAL DISEASES, WHICH MAY OPEN A NEW VENUE TO CURE CHRONIC HEPATITIS B. (HEPATOLOGY 2017;66:2066-2077). 2017 10 1052 49 CLINICAL IMPLICATIONS OF HEPATITIS B VIRUS RNA AND COVALENTLY CLOSED CIRCULAR DNA IN MONITORING PATIENTS WITH CHRONIC HEPATITIS B TODAY WITH A GAZE INTO THE FUTURE: THE FIELD IS UNPREPARED FOR A STERILIZING CURE. . CHRONIC HEPATITIS B VIRUS (HBV) INFECTION HAS LONG REMAINED A CRITICAL GLOBAL HEALTH ISSUE. COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) IS A PERSISTENT FORM OF THE HBV GENOME THAT MAINTAINS HBV CHRONICITY. DECADES OF EXTENSIVE RESEARCH RESULTED IN THE TWO THERAPEUTIC OPTIONS CURRENTLY AVAILABLE: NUCLEOT(S)IDE ANALOGS AND INTERFERON (IFN) THERAPY. A PLETHORA OF RELIABLE MARKERS TO MONITOR HBV PATIENTS HAS BEEN ESTABLISHED, INCLUDING THE RECENTLY DISCOVERED ENCAPSIDATED PREGENOMIC RNA IN SERUM, WHICH CAN BE USED TO DETERMINE TREATMENT END-POINTS AND TO PREDICT THE SUSCEPTIBILITY OF PATIENTS TO IFN. ADDITIONALLY, HBV RNA SPLICE VARIANTS AND CCCDNA AND ITS EPIGENETIC MODIFICATIONS ARE ASSOCIATED WITH THE CLINICAL COURSE AND RISKS OF HEPATOCELLULAR CARCINOMA (HCC) AND LIVER FIBROSIS. HOWEVER, NEW ANTIVIRALS, INCLUDING CRISPR/CAS9, APOBEC-MEDIATED DEGRADATION OF CCCDNA, AND T-CELL THERAPIES AIM AT COMPLETELY ELIMINATING HBV, AND IT IS CLEAR THAT THE DIAGNOSTIC ARSENAL FOR DEFINING THE LONG-AWAITED STERILIZING CURE IS MISSING. IN THIS REVIEW, WE DISCUSS THE CURRENTLY AVAILABLE TOOLS FOR DETECTING AND MEASURING HBV RNAS AND CCCDNA, AS WELL AS THE STATE-OF-THE-ART IN CLINICAL IMPLICATIONS OF THESE MARKERS, AND DEBATE NEEDS AND GOALS WITHIN THE CONTEXT OF THE STERILIZING CURE THAT IS SOON TO COME. 2018 11 5936 32 TARGETING HEPATITIS B VIRUS COVALENTLY CLOSED CIRCULAR DNA AND HEPATITIS B VIRUS X PROTEIN: RECENT ADVANCES AND NEW APPROACHES. CHRONIC HEPATITIS B VIRUS (HBV) INFECTION REMAINS A WORLDWIDE CONCERN AND PUBLIC HEALTH PROBLEM. TWO KEY ASPECTS OF THE HBV LIFE CYCLE ARE ESSENTIAL FOR VIRAL REPLICATION AND THUS THE DEVELOPMENT OF CHRONIC INFECTIONS: THE ESTABLISHMENT OF THE VIRAL MINICHROMOSOME, COVALENTLY CLOSED CIRCULAR (CCC) DNA, WITHIN THE NUCLEUS OF INFECTED HEPATOCYTES AND THE EXPRESSION OF THE REGULATORY HEPATITIS B VIRUS X PROTEIN (HBX). INTERESTINGLY, NUCLEAR HBX REDIRECTS HOST EPIGENETIC MACHINERY TO ACTIVATE CCCDNA TRANSCRIPTION. IN THIS PERSPECTIVE, WE PROVIDE AN OVERVIEW OF RECENT ADVANCES IN UNDERSTANDING THE REGULATION OF CCCDNA AND THE MECHANISTIC AND FUNCTIONAL ROLES OF HBX. WE ALSO DESCRIBE THE PROGRESS TOWARD TARGETING BOTH CCCDNA AND HBX FOR THERAPEUTIC PURPOSES. FINALLY, WE OUTLINE STANDING QUESTIONS IN THE FIELD AND PROPOSE COMPLEMENTARY CHEMICAL BIOLOGY APPROACHES TO ADDRESS THEM. 2019 12 6479 57 TOWARD A NEW ERA OF HEPATITIS B VIRUS THERAPEUTICS: THE PURSUIT OF A FUNCTIONAL CURE. HEPATITIS B VIRUS (HBV) INFECTION, ALTHOUGH PREVENTABLE BY VACCINATION, REMAINS A GLOBAL HEALTH PROBLEM AND A MAJOR CAUSE OF CHRONIC LIVER DISEASE. ALTHOUGH CURRENT TREATMENT STRATEGIES SUPPRESS VIRAL REPLICATION VERY EFFICIENTLY, THE OPTIMAL ENDPOINT OF HEPATITIS B SURFACE ANTIGEN (HBSAG) CLEARANCE IS RARELY ACHIEVED. MOREOVER, THE THORNY PROBLEMS OF PERSISTENT CHROMATIN-LIKE COVALENTLY CLOSED CIRCULAR DNA AND THE PRESENCE OF INTEGRATED HBV DNA IN THE HOST GENOME ARE IGNORED. THEREFORE, THE SCIENTIFIC COMMUNITY HAS FOCUSED ON DEVELOPING INNOVATIVE THERAPEUTIC APPROACHES TO ACHIEVE A FUNCTIONAL CURE OF HBV, DEFINED AS UNDETECTABLE HBV DNA AND HBSAG LOSS OVER A LIMITED TREATMENT PERIOD. A DEEPER UNDERSTANDING OF THE HBV LIFE CYCLE HAS LED TO THE INTRODUCTION OF NOVEL DIRECT-ACTING ANTIVIRALS THAT EXERT THEIR FUNCTION THROUGH MULTIPLE MECHANISMS, INCLUDING INHIBITION OF VIRAL ENTRY, TRANSCRIPTIONAL SILENCING, EPIGENETIC MANIPULATION, INTERFERENCE WITH CAPSID ASSEMBLY, AND DISRUPTION OF HBSAG RELEASE. IN PARALLEL, ANOTHER CATEGORY OF NEW DRUGS AIMS TO RESTORE DYSREGULATED IMMUNE FUNCTION IN CHRONIC HEPATITIS B ACCOMPANIED BY LETHARGIC CELLULAR AND HUMORAL RESPONSES. STIMULATION OF INNATE IMMUNITY BY PATTERN-RECOGNITION RECEPTOR AGONISTS LEADS TO UPREGULATION OF ANTIVIRAL CYTOKINE EXPRESSION AND APPEARS TO CONTRIBUTE TO HBV CONTAINMENT. IMMUNE CHECKPOINT INHIBITORS AND ADOPTIVE TRANSFER OF GENETICALLY ENGINEERED T CELLS ARE BREAKTHROUGH TECHNOLOGIES CURRENTLY BEING EXPLORED THAT MAY ELICIT POTENT HBV-SPECIFIC T-CELL RESPONSES. IN ADDITION, SEVERAL CLINICAL TRIALS ARE ATTEMPTING TO CLARIFY THE ROLE OF THERAPEUTIC VACCINATION IN THIS SETTING. ULTIMATELY, IT IS INCREASINGLY RECOGNIZED THAT ELIMINATION OF HBV REQUIRES A TREATMENT REGIMEN BASED ON A COMBINATION OF MULTIPLE DRUGS. THIS REVIEW DESCRIBES THE RATIONALE FOR PROGRESSIVE THERAPEUTIC INTERVENTIONS AND DISCUSSES THE LATEST FINDINGS IN THE FIELD OF HBV THERAPEUTICS. 2021 13 6016 39 THE ASSOCIATION BETWEEN HEPATOCARCINOGENESIS AND INTRACELLULAR ALTERATIONS DUE TO HEPATITIS B VIRUS INFECTION. CHRONIC HEPATITIS B VIRUS (HBV) INFECTION IS A WORLDWIDE HEALTH PROBLEM LEADING TO SEVERE LIVER DYSFUNCTION, INCLUDING LIVER CIRRHOSIS AND HEPATOCELLULAR CARCINOMA. ALTHOUGH CURRENT ANTIVIRAL THERAPIES FOR CHRONIC HBV INFECTION HAVE BEEN IMPROVED AND CAN LEAD TO A STRONG SUPPRESSION OF VIRAL REPLICATION, IT IS DIFFICULT TO COMPLETELY ELIMINATE THE VIRUS WITH THESE THERAPIES ONCE CHRONIC HBV INFECTION IS ESTABLISHED IN THE HOST. FURTHERMORE, CHRONIC HBV INFECTION ALTERS INTRACELLULAR METABOLISM AND SIGNALLING PATHWAYS, RESULTING IN THE ACTIVATION OF CARCINOGENESIS IN THE LIVER. HBV PRODUCES FOUR VIRAL PROTEINS: HEPATITIS B SURFACE-, HEPATITIS B CORE-, HEPATITIS B X PROTEIN, AND POLYMERASE; EACH PLAYS AN IMPORTANT ROLE IN HBV REPLICATION AND THE INTRACELLULAR SIGNALLING PATHWAYS ASSOCIATED WITH HEPATOCARCINOGENESIS. IN VITRO AND IN VIVO EXPERIMENTAL MODELS FOR ANALYZING HBV INFECTION AND REPLICATION HAVE BEEN ESTABLISHED, AND GENE EXPRESSION ANALYSES USING MICROARRAYS OR NEXT-GENERATION SEQUENCING HAVE ALSO BEEN DEVELOPED. THUS, IT IS POSSIBLE TO CLARIFY THE MOLECULAR MECHANISMS FOR INTRACELLULAR ALTERATIONS, SUCH AS ENDOPLASMIC RETICULUM STRESS, OXIDATIVE STRESS, AND EPIGENETIC MODIFICATIONS. IN THIS REVIEW, THE IMPACT OF HBV VIRAL PROTEINS AND INTRACELLULAR ALTERATIONS IN HBV-ASSOCIATED HEPATOCARCINOGENESIS ARE DISCUSSED. 2021 14 6337 32 THE ROLE OF DNA-METHYLTRANSFERASES IN THE LIFE CYCLE OF HEPATITIS B VIRUS AND PATHOGENESIS OF CHRONIC HEPATITIS B. CHRONIC HEPATITIS B IS CAUSED BY A PERSISTENT FORM OF HEPATITIS B VIRUS, COVALENTLY CLOSED CIRCULAR DNA (CCCDNA). STABILITY OF CCCDNA IS ASSOCIATED WITH INTRACELLULAR LOCALIZATION OF CCCDNA AND FORMATION OF MINICHROMOSOME, REGULATED BY EPIGENETIC MECHANISMS. ONE OF THE KEY MECHANISMS IN EPIGENETICS IS METHYLATION OF DNA ON CPG ISLANDS. EXPRESSION LEVELS OF DNA-METHYLTRANSFERASES (DNMTS) IN CHRONIC HEPATITIS B PATIENTS WERE SHOWN TO BE UPREGULATED. NEVERTHELESS, THE ROLE OF DNMTS IN THE LIFE CYCLE OF HBV AND THEIR EFFECTS ON THE CELL REMAIN ELUSIVE. IN THIS REVIEW, WE DISCUSS LATEST ACHIEVEMENTS ON THE ROLE OF DNMTS IN CHRONIC HEPATITIS B AND HBV IN VITRO MODELS. 2018 15 6712 39 VIRUS-HOST INTERPLAY IN HEPATITIS B VIRUS INFECTION AND EPIGENETIC TREATMENT STRATEGIES. WORLDWIDE, CHRONIC HEPATITIS B VIRUS (HBV) INFECTION IS A MAJOR HEALTH PROBLEM AND NO CURE EXISTS. IMPORTANTLY, HEPATOCYTE INTRUSION BY HBV PARTICLES RESULTS IN A COMPLEX DEREGULATION OF BOTH VIRAL AND HOST CELLULAR GENETIC AND EPIGENETIC PROCESSES. AMONG THE ATTEMPTS TO DEVELOP NOVEL THERAPEUTIC APPROACHES AGAINST HBV INFECTION, SEVERAL OPTIONS TARGETING THE EPIGENOMIC REGULATION OF HBV REPLICATION ARE GAINING ATTENTION. THESE INCLUDE THE EXPERIMENTAL TREATMENT WITH 'EPIDRUGS'. MOREOVER, AS A TARGETED APPROACH, THE PRINCIPLE OF 'EPIGENETIC EDITING' RECENTLY IS BEING EXPLOITED TO CONTROL VIRAL REPLICATION. SILENCING OF HBV BY SPECIFIC REWRITING OF EPIGENETIC MARKS MIGHT DIMINISH VIRAL REPLICATION, VIREMIA, AND INFECTIVITY, EVENTUALLY CONTROLLING THE DISEASE AND ITS COMPLICATIONS. ADDITIONALLY, EPIGENETIC EDITING CAN BE USED AS AN EXPERIMENTAL TOOL TO INCREASE OUR LIMITED UNDERSTANDING REGARDING THE ROLE OF EPIGENETIC MODIFICATIONS IN VIRAL INFECTIONS. AIMING FOR PERMANENT EPIGENETIC REPROGRAMMING OF THE VIRAL GENOME WITHOUT UNSPECIFIC SIDE EFFECTS, THIS BREAKTHROUGH MAY PAVE THE ROADS FOR AN AMBITIOUS TECHNOLOGICAL PURSUIT: TO START DESIGNING A CURATIVE APPROACH UTILIZING MANIPULATIVE MOLECULAR THERAPIES FOR VIRAL INFECTIONS IN VIVO. 2017 16 6637 31 UNRAVELING THE COMPLEXITY OF HEPATITIS B VIRUS: FROM MOLECULAR UNDERSTANDING TO THERAPEUTIC STRATEGY IN 50 YEARS. HEPATITIS B VIRUS (HBV) IS A WELL-KNOWN HEPADNAVIRUS WITH A DOUBLE-STRANDED CIRCULAR DNA GENOME. ALTHOUGH HBV WAS FIRST DESCRIBED APPROXIMATELY 50 YEARS AGO, THE PRECISE MECHANISMS OF HBV INFECTION AND EFFECTIVE THERAPEUTIC STRATEGIES REMAIN UNCLEAR. HERE, WE FOCUS ON SUMMARIZING THE COMPLICATED MECHANISMS OF HBV REPLICATION AND INFECTION, AS WELL AS GENOMIC FACTORS AND EPIGENETIC REGULATION. ADDITIONALLY, WE DISCUSS IN VIVO MODELS OF HBV, AS WELL AS DIAGNOSIS, PREVENTION AND THERAPEUTIC DRUGS FOR HBV. TOGETHER, THE DATA IN THIS 50-YEAR REVIEW MAY PROVIDE NEW CLUES TO ELUCIDATE MOLECULAR MECHANISMS OF HBV PATHOGENESIS AND SHED NEW LIGHT ON THE FUTURE HBV THERAPIES. 2013 17 3401 31 HOW DID HEPATITIS B VIRUS EFFECT THE HOST GENOME IN THE LAST DECADE? THE PRINCIPAL REASON OF CHRONIC LIVER DISEASE, CIRRHOSIS AND HEPATOCELLULAR CARCINOMA IS CHRONIC VIRAL HEPATITIS ALL OVER THE WORLD. HEPATITIS B VIRUS (HBV) HAS SOME MUTAGENIC EFFECTS ON THE HOST GENOME. HBV MAY BE EXHIBITING THESE MUTAGENIC EFFECTS THROUGH INTEGRATING INTO THE HOST GENOME, THROUGH ITS VIRAL PROTEINS OR THROUGH SOME EPIGENETIC MECHANISMS RELATED WITH HBV PROTEINS. THIS REVIEW AIMS TO SUMMARIZE THE MOLECULAR MECHANISMS USED BY HBV FOR EFFECTING HOST GENOME DETERMINED IN THE LAST DECADE. THE FOCUS WILL BE ON THE EFFECTS OF INTEGRATION, HBV PROTEINS, ESPECIALLY HBV X PROTEIN AND EPIGENETIC MECHANISMS ON THE HOST GENOME. THESE INTERACTIONS BETWEEN HBV AND THE HOST GENOME ALSO FORMS THE UNDERLYING MECHANISMS OF THE EVOLUTION OF HEPATOCELLULAR CARCINOMA. 2014 18 3255 39 HEPATITIS B VIRUS X PROTEIN MEDIATED EPIGENETIC ALTERATIONS IN THE PATHOGENESIS OF HEPATOCELLULAR CARCINOMA. CHRONIC HEPATITIS B VIRUS (HBV) INFECTION IS A WORLDWIDE HEALTH PROBLEM. HEPATITIS B VIRUS X PROTEIN (HBX), A PLEIOTROPIC REGULATORY PROTEIN ENCODED BY HBV, IS NECESSARY FOR THE TRANSCRIPTION OF HBV COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) MINICHROMOSOMES, AND AFFECTS THE EPIGENETIC REGULATION OF HOST CELLS. THE EPIGENETIC REPROGRAMMING OF HBX ON HOST CELL GENOME IS STRONGLY INVOLVED IN HBV-RELATED HCC CARCINOGENESIS. HERE, WE REVIEW THE LATEST FINDINGS OF THE EPIGENETIC REGULATION INDUCED BY HBX PROTEIN IN HEPATOCELLULAR CARCINOMA (HCC), INCLUDING DNA METHYLATION, HISTONE MODIFICATION AND NON-CODING RNA EXPRESSION. THE INFLUENCE OF HBX ON THE EPIGENETIC REGULATION OF CCCDNA IS ALSO SUMMARIZED. IN ADDITION, PRELIMINARY STUDIES OF TARGETED DRUGS FOR EPIGENETIC CHANGES INDUCED BY HBX ARE ALSO DISCUSSED. THE EXPLORATION OF EPIGENETIC MARKERS AS POTENTIAL TARGETS WILL HELP TO DEVELOP NEW PREVENTION AND/OR TREATMENT METHODS FOR HBX-RELATED HCC. 2022 19 6754 45 WILL WE NEED NOVEL COMBINATIONS TO CURE HBV INFECTION? CHRONIC HEPATITIS B IS A NUMERICALLY IMPORTANT CAUSE OF CIRRHOSIS AND HEPATOCELLULAR CARCINOMA. NUCLEOSIDE ANALOGUE THERAPY MAY MODIFY THE RISK. HOWEVER, MAINTENANCE SUPPRESSIVE THERAPY IS REQUIRED, AS A FUNCTIONAL CURE (GENERALLY DEFINED AS LOSS OF HBSAG OFF TREATMENT) IS AN UNCOMMON OUTCOME OF ANTIVIRAL TREATMENT. CHRONIC HEPATITIS B IS A NUMERICALLY IMPORTANT CAUSE OF CIRRHOSIS AND HEPATOCELLULAR CARCINOMA. NUCLEOSIDE ANALOGUE THERAPY MAY MODIFY THE RISK. HOWEVER, MAINTENANCE SUPPRESSIVE THERAPY IS REQUIRED, AS A FUNCTIONAL CURE (GENERALLY DEFINED AS LOSS OF HBSAG OFF TREATMENT) IS AN UNCOMMON OUTCOME OF ANTIVIRAL TREATMENT. CURRENTLY NUMEROUS INVESTIGATIONAL AGENTS BEING DEVELOPED TO EITHER INTERFERE WITH SPECIFIC STEPS IN HBV REPLICATION OR AS HOST CELLULAR TARGETING AGENTS, THAT INHIBIT VIRAL REPLICATION, AND DEPLETE OR INACTIVATE CCCDNA, OR AS IMMUNE MODULATORS. SYNERGISTIC MECHANISMS WILL BE NEEDED TO INCORPORATE A DECREASE IN HBV TRANSCRIPTION, IMPAIRMENT OF TRANSCRIPTION FROM HBV GENOMES, LOSS OF CCCDNA OR ALTERED EPIGENETIC REGULATION OF CCCDNA TRANSCRIPTION, AND IMMUNE MODULATION OR IMMUNOLOGICALLY STIMULATED HEPATOCYTE CELL TURNOVER. NUCLEOSIDE ANALOGUE SUPPRESSED PATIENTS ARE BEING INCLUDED IN MANY CURRENT TRIALS. TRIALS ARE PROGRESSING TO COMBINATION THERAPY AS ADDITIVE OR SYNERGISTIC EFFECTS ARE SOUGHT. THESE TRIALS WILL PROVIDE IMPORTANT INSIGHTS INTO THE BIOLOGY OF HBV AND PERTURBATIONS OF THE IMMUNE RESPONSE, REQUIRED TO EFFECT HBSAG LOSS AT DIFFERENT STAGES OF THE DISEASE. THE PROSPECT OF CURES OF HEPATITIS B WOULD ENSURE THAT A WIDE RANGE OF PATIENTS COULD BE DEEMED CANDIDATES FOR TREATMENT WITH NEW COMPOUNDS IF THESE WERE HIGHLY EFFECTIVE, FINITE AND SAFE. WITHDRAWAL OF THERAPY IN SHORT-TERM TRIALS IS CHALLENGING BECAUSE SHORT-TERM THERAPIES MAY RISK SEVERE HEPATITIS FLARES, AND HEPATIC DECOMPENSATION. THE LIMITED CLINICAL TRIAL DATA TO DATE SUGGEST THAT COMBINATION THERAPY IS INEVITABLE. 2020 20 4055 47 MAPPING OF HISTONE MODIFICATIONS IN EPISOMAL HBV CCCDNA UNCOVERS AN UNUSUAL CHROMATIN ORGANIZATION AMENABLE TO EPIGENETIC MANIPULATION. CHRONIC HEPATITIS B VIRUS (HBV) INFECTION AFFECTS 240 MILLION PEOPLE WORLDWIDE AND IS A MAJOR RISK FACTOR FOR LIVER FAILURE AND HEPATOCELLULAR CARCINOMA. CURRENT ANTIVIRAL THERAPY INHIBITS CYTOPLASMIC HBV GENOMIC REPLICATION, BUT IS NOT CURATIVE BECAUSE IT DOES NOT DIRECTLY AFFECT NUCLEAR HBV CLOSED CIRCULAR DNA (CCCDNA), THE GENOMIC FORM THAT TEMPLATES VIRAL TRANSCRIPTION AND SUSTAINS VIRAL PERSISTENCE. NOVEL APPROACHES THAT DIRECTLY TARGET CCCDNA REGULATION WOULD THEREFORE BE HIGHLY DESIRABLE. CCCDNA IS ASSEMBLED WITH CELLULAR HISTONE PROTEINS INTO CHROMATIN, BUT LITTLE IS KNOWN ABOUT THE REGULATION OF HBV CHROMATIN BY HISTONE POSTTRANSLATIONAL MODIFICATIONS (PTMS). HERE, USING A NEW CCCDNA CHIP-SEQ APPROACH, WE REPORT, TO OUR KNOWLEDGE, THE FIRST GENOME-WIDE MAPS OF PTMS IN CCCDNA-CONTAINING CHROMATIN FROM DE NOVO INFECTED HEPG2 CELLS, PRIMARY HUMAN HEPATOCYTES, AND FROM HBV-INFECTED LIVER TISSUE. WE FIND HIGH LEVELS OF PTMS ASSOCIATED WITH ACTIVE TRANSCRIPTION ENRICHED AT SPECIFIC SITES WITHIN THE HBV GENOME AND, SURPRISINGLY, VERY LOW LEVELS OF PTMS LINKED TO TRANSCRIPTIONAL REPRESSION EVEN AT SILENT HBV PROMOTERS. WE SHOW THAT TRANSCRIPTION AND ACTIVE PTMS IN HBV CHROMATIN ARE REDUCED BY THE ACTIVATION OF AN INNATE IMMUNITY PATHWAY, AND THAT THIS EFFECT CAN BE RECAPITULATED WITH A SMALL MOLECULE EPIGENETIC MODIFYING AGENT, OPENING THE POSSIBILITY THAT CHROMATIN-BASED REGULATION OF CCCDNA TRANSCRIPTION COULD BE A NEW THERAPEUTIC APPROACH TO CHRONIC HBV INFECTION. 2015