1 5365 103 RECENT ADVANCES IN HEPATITIS B TREATMENT. HEPATITIS B VIRUS INFECTION AFFECTS OVER 250 MILLION CHRONIC CARRIERS, CAUSING MORE THAN 800,000 DEATHS ANNUALLY, ALTHOUGH A SAFE AND EFFECTIVE VACCINE IS AVAILABLE. CURRENTLY USED ANTIVIRAL AGENTS, PEGYLATED INTERFERON AND NUCLEOS(T)IDE ANALOGUES, HAVE MAJOR DRAWBACKS AND FAIL TO COMPLETELY ERADICATE THE VIRUS FROM INFECTED CELLS. THUS, ACHIEVING A "FUNCTIONAL CURE" OF THE INFECTION REMAINS A REAL CHALLENGE. RECENT FINDINGS CONCERNING THE VIRAL REPLICATION CYCLE HAVE LED TO DEVELOPMENT OF NOVEL THERAPEUTIC APPROACHES INCLUDING VIRAL ENTRY INHIBITORS, EPIGENETIC CONTROL OF CCCDNA, IMMUNE MODULATORS, RNA INTERFERENCE TECHNIQUES, RIBONUCLEASE H INHIBITORS, AND CAPSID ASSEMBLY MODULATORS. PROMISING PRECLINICAL RESULTS HAVE BEEN OBTAINED, AND THE LEADING MOLECULES UNDER DEVELOPMENT HAVE ENTERED CLINICAL EVALUATION. THIS REVIEW SUMMARIZES THE KEY STEPS OF THE HBV LIFE CYCLE, EXAMINES THE CURRENTLY APPROVED ANTI-HBV DRUGS, AND ANALYZES NOVEL HBV TREATMENT REGIMENS. 2021 2 5952 43 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 3 5368 28 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 4 5689 35 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 5 2915 36 GENE THERAPY FOR CHRONIC HBV-CAN WE ELIMINATE CCCDNA? CHRONIC INFECTION WITH THE HEPATITIS B VIRUS (HBV) IS A GLOBAL HEALTH CONCERN AND ACCOUNTS FOR APPROXIMATELY 1 MILLION DEATHS ANNUALLY. AMONGST OTHER LIMITATIONS OF CURRENT ANTI-HBV TREATMENT, FAILURE TO ELIMINATE THE VIRAL COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) AND EMERGENCE OF RESISTANCE REMAIN THE MOST WORRISOME. VIRAL REBOUND FROM LATENT EPISOMAL CCCDNA RESERVOIRS OCCURS FOLLOWING CESSATION OF THERAPY, PATIENT NON-COMPLIANCE, OR THE DEVELOPMENT OF ESCAPE MUTANTS. SIMULTANEOUS VIRAL CO-INFECTIONS, SUCH AS BY HIV-1, FURTHER COMPLICATE THERAPEUTIC INTERVENTIONS. THESE CHALLENGES HAVE PROMPTED DEVELOPMENT OF NOVEL TARGETED HEPATITIS B THERAPIES. GIVEN THE EASE WITH WHICH HIGHLY SPECIFIC AND POTENT NUCLEIC ACID THERAPEUTICS CAN BE RATIONALLY DESIGNED, GENE THERAPY HAS GENERATED INTEREST FOR ANTIVIRAL APPLICATION. GENE THERAPY STRATEGIES DEVELOPED FOR HBV INCLUDE GENE SILENCING BY HARNESSING RNA INTERFERENCE, TRANSCRIPTIONAL INHIBITION THROUGH EPIGENETIC MODIFICATION OF TARGET DNA, GENOME EDITING BY DESIGNER NUCLEASES, AND IMMUNE MODULATION WITH CYTOKINES. DNA-BINDING DOMAINS AND EFFECTORS BASED ON THE ZINC FINGER (ZF), TRANSCRIPTION ACTIVATOR-LIKE EFFECTOR (TALE), AND CLUSTERED REGULARLY INTERSPACED SHORT PALINDROMIC REPEAT (CRISPR) SYSTEMS ARE REMARKABLY WELL SUITED TO TARGETING EPISOMAL CCCDNA. THIS REVIEW DISCUSSES RECENT DEVELOPMENTS AND CHALLENGES FACING THE FIELD OF ANTI-HBV GENE THERAPY, ITS POTENTIAL CURATIVE SIGNIFICANCE AND THE PROGRESS TOWARDS CLINICAL APPLICATION. 2018 6 6479 45 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 7 1052 30 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 8 2324 27 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 9 2240 36 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 10 5936 29 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 11 4754 28 NOVEL THERAPEUTIC STRATEGIES FOR CHRONIC HEPATITIS B. THE LAST FEW YEARS HAVE SEEN A RESURGENCE OF ACTIVITY IN THE HEPATITIS B DRUG PIPELINE, WITH MANY COMPOUNDS IN VARIOUS STAGES OF DEVELOPMENT. THIS REVIEW AIMS TO PROVIDE A COMPREHENSIVE OVERVIEW OF THE LATEST ADVANCES IN THERAPEUTICS FOR CHRONIC HEPATITIS B (CHB). WE WILL DISCUSS THE BROAD SPECTRUM OF DIRECT-ACTING ANTIVIRALS IN CLINICAL DEVELOPMENT, INCLUDING CAPSIDS INHIBITORS, SIRNA, HBSAG AND POLYMERASE INHIBITORS. IN ADDITION, HOST-TARGETED THERAPIES (HTT) WILL BE EXTENSIVELY REVIEWED, FOCUSING ON THE LATEST PROGRESS IN IMMUNOTHERAPEUTICS SUCH AS TOLL-LIKE RECEPTORS AND RIG-1 AGONISTS, THERAPEUTIC VACCINES AND IMMUNE CHECKPOINTS MODULATORS. A GROWING NUMBER OF HTT IN PRE-CLINICAL DEVELOPMENT DIRECTLY TARGET THE KEY TO HBV PERSISTENCE, NAMELY THE COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) AND HOLD GREAT PROMISE FOR HBV CURE. THIS EXCITING AREA OF HBV RESEARCH WILL BE HIGHLIGHTED, AND MOLECULES SUCH AS CYCLOPHILINS INHIBITORS, APOBEC3 DEAMINASES AND EPIGENETIC MODIFIERS WILL BE DISCUSSED. 2022 12 6712 27 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 13 3806 36 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 14 6754 34 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 15 3257 38 HEPATITIS B X ANTIGEN (HBX) IS AN IMPORTANT THERAPEUTIC TARGET IN THE PATHOGENESIS OF HEPATOCELLULAR CARCINOMA. HEPATITIS B VIRUS (HBV) IS A HUMAN PATHOGEN THAT HAS INFECTED AN ESTIMATED TWO BILLION PEOPLE WORLDWIDE. DESPITE THE AVAILABILITY OF HIGHLY EFFICACIOUS VACCINES, UNIVERSAL SCREENING OF THE BLOOD SUPPLY FOR VIRUS, AND POTENT DIRECT ACTING ANTI-VIRAL DRUGS, THERE ARE MORE THAN 250 MILLION CARRIERS OF HBV WHO ARE AT RISK FOR THE SEQUENTIAL DEVELOPMENT OF HEPATITIS, FIBROSIS, CIRRHOSIS AND HEPATOCELLULAR CARCINOMA (HCC). MORE THAN 800,000 DEATHS PER YEAR ARE ATTRIBUTED TO CHRONIC HEPATITIS B. MANY DIFFERENT THERAPEUTIC APPROACHES HAVE BEEN DEVELOPED TO BLOCK VIRUS REPLICATION, AND ALTHOUGH EFFECTIVE, NONE ARE CURATIVE. THESE TREATMENTS HAVE LITTLE OR NO IMPACT UPON THE PORTIONS OF INTEGRATED HBV DNA, WHICH OFTEN ENCODE THE VIRUS REGULATORY PROTEIN, HBX. ALTHOUGH GIVEN LITTLE ATTENTION, HBX IS AN IMPORTANT THERAPEUTIC TARGET BECAUSE IT CONTRIBUTES IMPORTANTLY TO (A) HBV REPLICATION, (B) IN PROTECTING INFECTED CELLS FROM IMMUNE MEDIATED DESTRUCTION DURING CHRONIC INFECTION, AND (C) IN THE DEVELOPMENT OF HCC. THUS, THE DEVELOPMENT OF THERAPIES TARGETING HBX, COMBINED WITH OTHER ESTABLISHED THERAPIES, WILL PROVIDE A FUNCTIONAL CURE THAT WILL TARGET VIRUS REPLICATION AND FURTHER REDUCE OR ELIMINATE BOTH THE MORBIDITY AND MORTALITY ASSOCIATED WITH CHRONIC LIVER DISEASE AND HCC. SIMULTANEOUS TARGETING OF ALL THESE CHARACTERISTICS UNDERSCORES THE IMPORTANCE OF DEVELOPING THERAPIES AGAINST HBX. 2021 16 1178 31 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 17 3394 38 HOST EPIGENETIC ALTERATIONS AND HEPATITIS B VIRUS-ASSOCIATED HEPATOCELLULAR CARCINOMA. HEPATOCELLULAR CARCINOMA (HCC) IS THE MOST FREQUENT PRIMARY MALIGNANCY OF THE LIVER AND A LEADING CAUSE OF CANCER-RELATED DEATHS WORLDWIDE. ALTHOUGH MUCH PROGRESS HAS BEEN MADE IN HCC DRUG DEVELOPMENT IN RECENT YEARS, TREATMENT OPTIONS REMAIN LIMITED. THE MAJOR CAUSE OF HCC IS CHRONIC HEPATITIS B VIRUS (HBV) INFECTION. DESPITE THE EXISTENCE OF A VACCINE, MORE THAN 250 MILLION INDIVIDUALS ARE CHRONICALLY INFECTED BY HBV. CURRENT ANTIVIRAL THERAPIES CAN REPRESS VIRAL REPLICATION BUT TO DATE THERE IS NO CURE FOR CHRONIC HEPATITIS B. OF NOTE, INHIBITION OF VIRAL REPLICATION REDUCES BUT DOES NOT ELIMINATE THE RISK OF HCC DEVELOPMENT. HBV CONTRIBUTES TO LIVER CARCINOGENESIS BY DIRECT AND INDIRECT EFFECTS. THIS REVIEW SUMMARIZES THE CURRENT KNOWLEDGE OF HBV-INDUCED HOST EPIGENETIC ALTERATIONS AND THEIR ASSOCIATION WITH HCC, WITH AN EMPHASIS ON THE INTERACTIONS BETWEEN HBV PROTEINS AND THE HOST CELL EPIGENETIC MACHINERY LEADING TO MODULATION OF GENE EXPRESSION. 2021 18 1239 24 CURE AND LONG-TERM REMISSION STRATEGIES. THE MAJORITY OF VIRALLY SUPPRESSED INDIVIDUALS WILL EXPERIENCE RAPID VIRAL REBOUND UPON ANTIRETROVIRAL THERAPY (ART) INTERRUPTION, PROVIDING A STRONG RATIONALE FOR THE DEVELOPMENT OF CURE STRATEGIES. MOREOVER, DESPITE ART VIROLOGICAL CONTROL, HIV INFECTION IS STILL ASSOCIATED WITH CHRONIC IMMUNE ACTIVATION, INFLAMMATION, COMORBIDITIES, AND ACCELERATED AGING. THESE EFFECTS ARE BELIEVED TO BE DUE, IN PART, TO LOW-GRADE PERSISTENT TRANSCRIPTION AND TRICKLING PRODUCTION OF VIRAL PROTEINS FROM THE POOL OF LATENT PROVIRUSES CONSTITUTING THE VIRAL RESERVOIR. IN RECENT YEARS THERE HAS BEEN AN INCREASING INTEREST IN DEVELOPING WHAT HAS BEEN TERMED A FUNCTIONAL CURE FOR HIV. THIS APPROACH ENTAILS THE LONG-TERM, DURABLE CONTROL OF VIRAL EXPRESSION IN THE ABSENCE OF THERAPY, PREVENTING DISEASE PROGRESSION AND TRANSMISSION, DESPITE THE PRESENCE OF DETECTABLE INTEGRATED PROVIRUSES. ONE SUCH STRATEGY, THE BLOCK-AND-LOCK APPROACH FOR A FUNCTIONAL CURE, PROPOSES THE EPIGENETIC SILENCING OF PROVIRAL EXPRESSION, LOCKING THE VIRUS IN A PROFOUND LATENT STATE, FROM WHICH REACTIVATION IS VERY UNLIKELY. THE PROOF-OF-CONCEPT FOR THIS APPROACH WAS DEMONSTRATED WITH THE USE OF A SPECIFIC SMALL MOLECULE TARGETING HIV TRANSCRIPTION. HERE WE REVIEW THE PRINCIPLES BEHIND THE BLOCK-AND-LOCK APPROACH AND SOME OF THE ADDITIONAL STRATEGIES PROPOSED TO SILENCE HIV EXPRESSION. 2022 19 3782 39 INTERFERON THERAPY OF CHRONIC HEPATITIS B. CHRONIC HEPATITIS B (CHB) RESULTS FROM THE INABILITY OF THE HOST'S IMMUNE SYSTEM TO CONTROL VIRAL REPLICATION. INTERFERON-ALPHA (IFN-ALPHA) THERAPY CAN CONVERT CHB INTO INACTIVE HEPATITIS B VIRUS (HBV) INFECTION IN 20-30% OF THE TREATED PATIENTS. IN SPITE OF THE LOW RESPONSE RATE, IFN-ALPHA THERAPY HAS THE ADVANTAGE OF HAVING A LIMITED DURATION AND BEING EFFECTIVE EVEN AFTER THERAPY, AS DEMONSTRATED BY A MUCH HIGHER INCIDENCE OF HBSAG CLEARANCE IN RESPONDERS TO IFN-ALPHA THAN IN NATURALLY OCCURRING INACTIVE HBSAG CARRIERS. IFN-ALPHA HAS MULTIPLE ANTIVIRAL, ANTIPROLIFERATIVE, AND IMMUNOMODULATORY ACTIVITIES AND TARGETS: CELLULAR GENES (IFN-STIMULATED GENES) ACTIVATING DIFFERENT PATHWAYS OF ANTIVIRAL DEFENSE IN INFECTED AND NONINFECTED CELLS, HBV REPLICATION BLOCKING THE RNA-CONTAINING CORE PARTICLE FORMATION AND ACCELERATING THEIR DECAY, DEGRADING PREGENOMIC RNA, AND MODULATING THE NUCLEAR VIRAL MINICHROMOSOME (COVALENTLY CLOSED CIRCULAR DNA) ACTIVITY BY TARGETING ITS EPIGENETIC REGULATION AND BOTH INNATE AND ADAPTIVE IMMUNE RESPONSE. THE INTERFERENCE OF VIRAL HETEROGENEITY AND GENETIC POLYMORPHISMS OF THE HOST ON IFN-ALPHA SUSCEPTIBILITY IS UNDER INVESTIGATION. ONLY A BETTER UNDERSTANDING OF THE COMPLEX INTERPLAY BETWEEN THE DIFFERENT ACTIVITIES OF IFN-ALPHA WOULD WARRANT THE AMELIORATION OF CURRENT THERAPEUTIC STRATEGIES AND THE DESIGN OF NEW THERAPEUTIC APPROACHES. THE STUDY OF ON-TREATMENT DYNAMICS OF HBV INFECTION BY MEANS OF COMBINED QUANTITATIVE MONITORING OF SERUM HBV DNA AND HBSAG WARRANT TAILORING TREATMENT AT THE SINGLE-PATIENT LEVEL AND CAN HELP TO MAKE TREATMENT MORE COST-EFFECTIVE BY USING THE DIFFERENT COMBINATIONS OF CURRENTLY AVAILABLE ANTIVIRALS, INCLUDING IFN, MORE APPROPRIATELY. INTEGRATED MOLECULAR AND CLINICAL KNOWLEDGE IN A SYSTEMS MEDICINE FASHION IS MANDATORY TO FURTHER IMPROVE ANTIVIRAL THERAPY IN CHB. 2014 20 442 22 ANTIVIRAL THERAPIES FOR HEPATITIS B VIRUS-RELATED HEPATOCELLULAR CARCINOMA. CHRONIC HEPATITIS B VIRUS (HBV) INFECTION IS A CRITICAL RISK FACTOR FOR THE CARCINOGENESIS AND PROGRESSION OF HEPATOCELLULAR CARCINOMA (HCC). IT PROMOTES HCC DEVELOPMENT BY INDUCING LIVER FIBROGENESIS, GENETIC AND EPIGENETIC ALTERATIONS, AND THE EXPRESSION OF ACTIVE VIRAL-CODED PROTEINS. EFFECTIVE ANTIVIRAL TREATMENTS INHIBIT THE REPLICATION OF HBV, REDUCE SERUM VIRAL LOAD AND ACCELERATE HEPATITIS B E ANTIGEN SERUM CONVERSION. TIMELY INITIATION OF ANTIVIRAL TREATMENT IS NOT ONLY ESSENTIAL FOR PREVENTING THE INCIDENCE OF HCC IN CHRONIC HEPATITIS B PATIENTS, BUT ALSO IMPORTANT FOR REDUCING HBV REACTIVATION, IMPROVING LIVER FUNCTION, REDUCING OR DELAYING HCC RECURRENCE, AND PROLONGING OVERALL SURVIVAL OF HBV-RELATED HCC PATIENTS AFTER CURATIVE AND PALLIATIVE THERAPIES. THE SELECTION OF ANTIVIRAL DRUGS, MONITORING OF INDICATORS SUCH AS HBV DNA AND HEPATITIS B SURFACE ANTIGEN, AND TIMELY RESCUE TREATMENT WHEN NECESSARY, ARE ESSENTIAL IN ANTIVIRAL THERAPIES FOR HBV-RELATED HCC. 2015