1 2242 117 EPIGENETIC MODULATION OF CD8(+) T CELL FUNCTION IN LENTIVIRUS INFECTIONS: A REVIEW. CD8(+) T CELLS ARE CRITICAL FOR CONTROLLING VIREMIA DURING HUMAN IMMUNODEFICIENCY VIRUS (HIV) INFECTION. THESE CELLS PRODUCE CYTOLYTIC FACTORS AND ANTIVIRAL CYTOKINES THAT ELIMINATE VIRALLY- INFECTED CELLS. DURING THE CHRONIC PHASE OF HIV INFECTION, CD8(+) T CELLS PROGRESSIVELY LOSE THEIR PROLIFERATIVE CAPACITY AND ANTIVIRAL FUNCTIONS. THESE DYSFUNCTIONAL CELLS ARE UNABLE TO CLEAR THE PRODUCTIVELY INFECTED AND REACTIVATED CELLS, REPRESENTING A ROADBLOCK IN HIV CURE. THEREFORE, MECHANISMS TO UNDERSTAND CD8(+) T CELL DYSFUNCTION AND STRATEGIES TO BOOST CD8(+) T CELL FUNCTION NEED TO BE INVESTIGATED. USING THE FELINE IMMUNODEFICIENCY VIRUS (FIV) MODEL FOR LENTIVIRAL PERSISTENCE, WE HAVE DEMONSTRATED THAT CD8(+) T CELLS EXHIBIT EPIGENETIC CHANGES SUCH AS DNA DEMETHYLATION DURING THE COURSE OF INFECTION AS COMPARED TO UNINFECTED CATS. WE HAVE ALSO DEMONSTRATED THAT LENTIVIRUS-ACTIVATED CD4(+)CD25(+) T REGULATORY CELLS INDUCE FORKHEAD BOX P3 (FOXP3) EXPRESSION IN VIRUS-SPECIFIC CD8(+) T CELL TARGETS, WHICH BINDS THE INTERLEUKIN (IL)-2, TUMOR NECROSIS FACTOR (TNF)-Α, AND INTERFERON (IFN)-Γ PROMOTERS IN THESE CD8(+) T CELLS. FINALLY, WE HAVE REPORTED THAT EPIGENETIC MODULATION REDUCES FOXP3 BINDING TO THESE PROMOTER REGIONS. THIS REVIEW COMPARES AND CONTRASTS OUR CURRENT UNDERSTANDING OF CD8(+) T CELL EPIGENETICS AND MECHANISMS OF LYMPHOCYTE SUPPRESSION DURING THE COURSE OF LENTIVIRAL INFECTION FOR TWO ANIMAL MODELS, FIV AND SIMIAN IMMUNODEFICIENCY VIRUS (SIV). 2018 2 5081 31 PI3KDELTA COORDINATES TRANSCRIPTIONAL, CHROMATIN, AND METABOLIC CHANGES TO PROMOTE EFFECTOR CD8(+) T CELLS AT THE EXPENSE OF CENTRAL MEMORY. PATIENTS WITH ACTIVATED PHOSPHATIDYLINOSITOL 3-KINASE DELTA (PI3KDELTA) SYNDROME (APDS) PRESENT WITH SINOPULMONARY INFECTIONS, LYMPHADENOPATHY, AND CYTOMEGALVIRUS (CMV) AND/OR EPSTEIN-BARR VIRUS (EBV) VIREMIA, YET WHY PATIENTS FAIL TO CLEAR CERTAIN CHRONIC VIRAL INFECTIONS REMAINS INCOMPLETELY UNDERSTOOD. USING PATIENT SAMPLES AND A MOUSE MODEL (PIK3CD(E1020K/+) MICE), WE DEMONSTRATE THAT, UPON ACTIVATION, PIK3CD(E1020K/+) CD8(+) T CELLS EXHIBIT EXAGGERATED FEATURES OF EFFECTOR POPULATIONS BOTH IN VITRO AND AFTER VIRAL INFECTION THAT ARE ASSOCIATED WITH INCREASED FAS-MEDIATED APOPTOSIS DUE TO SUSTAINED FOXO1 PHOSPHORYLATION AND FASL DEREPRESSION, ENHANCED MTORC1 AND C-MYC SIGNATURES, METABOLIC PERTURBATIONS, AND AN ALTERED CHROMATIN LANDSCAPE. CONVERSELY, PIK3CD(E1020K/+) CD8(+) CELLS FAIL TO SUSTAIN EXPRESSION OF PROTEINS CRITICAL FOR CENTRAL MEMORY, INCLUDING TCF1. STRIKINGLY, ACTIVATED PIK3CD(E1020K/+) CD8(+) CELLS EXHIBIT ALTERED TRANSCRIPTIONAL AND EPIGENETIC CIRCUITS CHARACTERIZED BY PRONOUNCED INTERLEUKIN-2 (IL-2)/STAT5 SIGNATURES AND HEIGHTENED IL-2 RESPONSES THAT PREVENT DIFFERENTIATION TO MEMORY-LIKE CELLS IN IL-15. OUR DATA POSITION PI3KDELTA AS INTEGRATING MULTIPLE SIGNALING NODES THAT PROMOTE CD8(+) T CELL EFFECTOR DIFFERENTIATION, PROVIDING INSIGHT INTO PHENOTYPES OF PATIENTS WITH APDS. 2021 3 6712 23 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 4 3189 33 HBX RELIEVES CHROMATIN-MEDIATED TRANSCRIPTIONAL REPRESSION OF HEPATITIS B VIRAL CCCDNA INVOLVING SETDB1 HISTONE METHYLTRANSFERASE. BACKGROUND & AIMS: MAINTENANCE OF THE COVALENTLY CLOSED CIRCULAR HBV DNA (CCCDNA) THAT SERVES AS A TEMPLATE FOR HBV TRANSCRIPTION IS RESPONSIBLE FOR THE FAILURE OF ANTIVIRAL THERAPIES. WHILE STUDIES IN CHRONIC HEPATITIS PATIENTS HAVE SHOWN THAT HIGH VIREMIA CORRELATES WITH HYPERACETYLATION OF CCCDNA-ASSOCIATED HISTONES, THE MOLECULAR MECHANISMS CONTROLLING CCCDNA STABILITY AND TRANSCRIPTIONAL REGULATION ARE STILL POORLY UNDERSTOOD. THIS STUDY AIMED TO DECIPHER THE ROLE OF CHROMATIN AND CHROMATIN MODIFIER PROTEINS ON HBV TRANSCRIPTION. METHODS: WE ANALYZED THE CHROMATIN STRUCTURE OF ACTIVELY TRANSCRIBED OR SILENCED CCCDNA BY INFECTING PRIMARY HUMAN HEPATOCYTES AND DIFFERENTIATED HEPARG CELLS WITH WILD-TYPE VIRUS OR VIRUS DEFICIENT (HBVX-) FOR THE EXPRESSION OF HEPATITIS B VIRUS X PROTEIN (HBX), THAT IS REQUIRED FOR HBV EXPRESSION. RESULTS: IN THE ABSENCE OF HBX, HBV CCCDNA WAS TRANSCRIPTIONALLY SILENCED WITH THE CONCOMITANT DECREASE OF HISTONE 3 (H3) ACETYLATION AND H3K4ME3, INCREASE OF H3 DI- AND TRI-METHYLATION (H3K9ME) AND THE RECRUITMENT OF HETEROCHROMATIN PROTEIN 1 FACTORS (HP1) THAT CORRELATE WITH CONDENSED CHROMATIN. SETDB1 WAS FOUND TO BE THE MAIN HISTONE METHYLTRANSFERASE RESPONSIBLE FOR THE DEPOSITION OF H3K9ME3 AND HBV REPRESSION. FINALLY, FULL TRANSCRIPTIONAL REACTIVATION OF HBVX- UPON HBX RE-EXPRESSION CORRELATED WITH AN INCREASE OF HISTONE ACETYLATION AND H3K4ME3, AND A CONCOMITANT DECREASE OF HP1 BINDING AND OF H3K9ME3 ON THE CCCDNA. CONCLUSION: UPON HBV INFECTION, CELLULAR MECHANISMS INVOLVING SETDB1-MEDIATED H3K9ME3 AND HP1 INDUCE SILENCING OF HBV CCCDNA TRANSCRIPTION THROUGH MODULATION OF CHROMATIN STRUCTURE. HBX IS ABLE TO RELIEVE THIS REPRESSION AND ALLOW THE ESTABLISHMENT OF ACTIVE CHROMATIN. 2015 5 3927 34 LIVER ABNORMALITIES AFTER ELIMINATION OF HCV INFECTION: PERSISTENT EPIGENETIC AND IMMUNOLOGICAL PERTURBATIONS POST-CURE. CHRONIC HEPATITIS C (CHC) IS A MAJOR CAUSE OF HEPATOCELLULAR CARCINOMA (HCC) WORLDWIDE. WHILE DIRECTLY ACTING ANTIVIRAL (DAA) DRUGS ARE NOW ABLE TO CURE VIRTUALLY ALL HEPATITIS C VIRUS (HCV) INFECTIONS, EVEN IN SUBJECTS WITH ADVANCED LIVER DISEASE, WHAT HAPPENS TO THE LIVER AND PROGRESSION OF THE DISEASE AFTER DAA-INDUCED CURE OF VIREMIA IS ONLY BEGINNING TO EMERGE. SEVERAL LARGE-SCALE CLINICAL STUDIES IN DIFFERENT PATIENT POPULATIONS HAVE SHOWN THAT PATIENTS WITH ADVANCED LIVER DISEASE MAINTAIN A RISK FOR DEVELOPING HCC EVEN WHEN THE ORIGINAL INSTIGATOR, THE VIRUS, IS ELIMINATED BY DAAS. HERE WE REVIEW EMERGING STUDIES DERIVED FROM MULTIPLE, COMPLEMENTARY EXPERIMENTAL SYSTEMS INVOLVING PATIENT LIVER TISSUES, HUMAN LIVER CELL CULTURES, HUMAN LIVER SLICE CULTURES, AND ANIMAL MODELS, SHOWING THAT HCV INFECTION INDUCES EPIGENETIC, SIGNALING, AND GENE EXPRESSION CHANGES IN THE LIVER ASSOCIATED WITH ALTERED HEPATIC INNATE IMMUNITY AND LIVER CANCER RISK. OF CRITICAL IMPORTANCE IS THE FACT THAT THESE VIRUS-INDUCED ABNORMALITIES PERSIST AFTER DAA CURE OF HCV. THESE NASCENT FINDINGS PORTEND THE DISCOVERY OF PATHWAYS INVOLVED IN POST-HCV IMMUNOPATHOGENESIS, WHICH MAY BE CLINICALLY ACTIONABLE TARGETS FOR MORE COMPREHENSIVE CARE OF DAA-CURED INDIVIDUALS. 2021 6 4849 28 OPIOID-MEDIATED HIV-1 IMMUNOPATHOGENESIS. DESPITE THE ABILITY OF COMBINATION ANTIRETROVIRAL THERAPY TO DRAMATICALLY SUPPRESS VIREMIA, THE BRAIN CONTINUES TO BE A RESERVOIR OF HIV-1 LOW-LEVEL REPLICATION. ADDING FURTHER COMPLEXITY TO THIS IS THE COMORBIDITY OF DRUG ABUSE WITH HIV-1 ASSOCIATED NEUROCOGNITIVE DISORDERS AND NEUROHIV. AMONG SEVERAL ABUSED DRUGS, THE USE OF OPIATES IS HIGHLY PREVALENT IN HIV-1 INFECTED INDIVIDUALS, BOTH AS AN ABUSED DRUG AS WELL AS FOR PAIN MANAGEMENT. OPIOIDS AND THEIR RECEPTORS HAVE ATTAINED NOTABLE ATTENTION OWING TO THEIR ABILITY TO MODULATE IMMUNE FUNCTIONS, IN TURN, IMPACTING DISEASE PROGRESSION. VARIOUS CELL CULTURE, ANIMAL AND HUMAN STUDIES HAVE IMPLICATED THE ROLE OF OPIOIDS AND THEIR RECEPTORS IN MODULATING VIRAL REPLICATION AND VIRUS-MEDIATED PATHOLOGY BOTH POSITIVELY AND NEGATIVELY. FURTHER, THE COMBINATORIAL EFFECTS OF HIV-1/HIV-1 PROTEINS AND MORPHINE HAVE DEMONSTRATED ACTIVATION OF INFLAMMATORY SIGNALING IN THE HOST SYSTEM. HEREIN, WE SUMMARIZED THE CURRENT KNOWLEDGE ON THE ROLE OF OPIOIDS ON PERIPHERAL IMMUNOPATHOGENESIS, VIRAL IMMUNOPATHOGENESIS, EPIGENETIC PROFILES OF THE HOST AND VIRAL GENOME, NEUROPATHOGENESIS OF SIV/SHIV-INFECTED NON-HUMAN PRIMATES, BLOOD-BRAIN-BARRIER, HIV-1 VIRAL LATENCY, AND VIRAL REBOUND. OVERALL, THIS REVIEW PROVIDES RECENT INSIGHTS INTO THE ROLE OF OPIOIDS IN HIV-1 IMMUNOPATHOGENESIS. GRAPHICAL ABSTRACT. 2020 7 3806 40 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 8 5936 25 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 9 5368 27 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 10 3373 62 HISTONE MODULATION BLOCKS TREG-INDUCED FOXP3 BINDING TO THE IL-2 PROMOTER OF VIRUS-SPECIFIC CD8(+) T CELLS FROM FELINE IMMUNODEFICIENCY VIRUS-INFECTED CATS. CD8(+) T CELLS ARE CRITICAL FOR CONTROLLING HIV INFECTION. DURING THE CHRONIC PHASE OF LENTIVIRAL INFECTION, CD8(+) T CELLS LOSE THEIR PROLIFERATIVE CAPACITY AND EXHIBIT IMPAIRED ANTIVIRAL FUNCTION. THIS LOSS OF CD8(+) T CELL FUNCTION IS DUE, IN PART, TO CD4(+)CD25(+) T REGULATORY (TREG) CELL-MEDIATED SUPPRESSION. OUR RESEARCH GROUP HAS DEMONSTRATED THAT LENTIVIRUS-ACTIVATED CD4(+)CD25(+) TREG CELLS INDUCE THE REPRESSIVE TRANSCRIPTION FACTOR FORKHEAD BOX P3 (FOXP3) IN AUTOLOGOUS CD8(+) T CELLS FOLLOWING CO-CULTURE. WE HAVE RECENTLY REPORTED THAT TREG-INDUCED FOXP3 BINDS THE INTERLEUKIN-2 (IL-2), INTERFERON-GAMMA (IFN- GAMMA), AND TUMOR NECROSIS FACTOR-ALPHA (TNF-ALPHA) PROMOTERS IN VIRUS-SPECIFIC CD8(+) T CELLS. THESE DATA SUGGEST AN IMPORTANT ROLE OF FOXP3-MEDIATED CD8(+) T CELL DYSFUNCTION IN LENTIVIRAL INFECTION. TO ELUCIDATE THE MECHANISM OF THIS SUPPRESSION, WE PREVIOUSLY REPORTED THAT DECREASED METHYLATION FACILITATES FOXP3 BINDING IN MITOGEN-ACTIVATED CD8(+) T CELLS FROM FELINE IMMUNODEFICIENCY VIRUS (FIV)-INFECTED CATS. WE DEMONSTRATED THE REDUCED BINDING OF FOXP3 TO THE IL-2 PROMOTER BY INCREASING METHYLATION OF CD8(+) T CELLS. IN THE STUDIES PRESENTED HERE, WE ASK IF ANOTHER FORM OF EPIGENETIC MODULATION MIGHT ALLEVIATE FOXP3-MEDIATED SUPPRESSION IN CD8(+) T CELLS. WE HYPOTHESIZED THAT DECREASING HISTONE ACETYLATION IN VIRUS-SPECIFIC CD8(+) T CELLS WOULD DECREASE TREG-INDUCED FOXP3 BINDING TO THE IL-2 PROMOTER. INDEED, USING ANACARDIC ACID (AA), A KNOWN HISTONE ACETYL TRANSFERASE (HAT) INHIBITOR, WE DEMONSTRATE A REDUCTION IN FOXP3 BINDING TO THE IL-2 PROMOTER IN VIRUS-SPECIFIC CD8(+) T CELLS CO-CULTURED WITH AUTOLOGOUS TREG CELLS. THESE DATA IDENTIFY A NOVEL MECHANISM OF FOXP3-MEDIATED CD8(+) T CELL DYSFUNCTION DURING LENTIVIRAL INFECTION. 2018 11 1178 23 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 12 2915 29 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 13 442 23 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 14 5689 33 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 15 4771 29 NUCLEAR SENSOR INTERFERON-INDUCIBLE PROTEIN 16 INHIBITS THE FUNCTION OF HEPATITIS B VIRUS COVALENTLY CLOSED CIRCULAR DNA BY INTEGRATING INNATE IMMUNE ACTIVATION AND EPIGENETIC SUPPRESSION. BACKGROUND AND AIMS: NUCLEAR-LOCATED COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) OF HEPATITIS B VIRUS (HBV) IS A DETERMINING FACTOR FOR HBV PERSISTENCE AND THE KEY OBSTACLE FOR A CURE OF CHRONIC HEPATITIS B. HOWEVER, IT REMAINS UNCLEAR WHETHER AND HOW THE HOST IMMUNE SYSTEM SENSES HBV CCCDNA AND ITS BIOLOGICAL CONSEQUENCES. APPROACH AND RESULTS: HERE, WE DEMONSTRATED THAT INTERFERON-INDUCIBLE PROTEIN 16 (IFI16) COULD SERVE AS A UNIQUE INNATE SENSOR TO RECOGNIZE AND BIND TO HBV CCCDNA IN HEPATIC NUCLEI, LEADING TO THE INHIBITION OF CCCDNA TRANSCRIPTION AND HBV REPLICATION. MECHANISTICALLY, OUR DATA SHOWED THAT IFI16 PROMOTED THE EPIGENETIC SUPPRESSION OF HBV CCCDNA BY TARGETING AN INTERFERON-STIMULATED RESPONSE ELEMENT (ISRE) PRESENT IN CCCDNA. IT IS OF INTEREST THAT THIS ISRE WAS ALSO REVEALED TO PLAY AN IMPORTANT ROLE IN IFI16-ACTIVATED TYPE I INTERFERON RESPONSES. FURTHERMORE, OUR DATA REVEALED THAT HBV COULD DOWN-REGULATE THE EXPRESSION LEVEL OF IFI16 IN HEPATOCYTES, AND THERE WAS A NEGATIVE CORRELATION BETWEEN IFI16 AND HBV TRANSCRIPTS IN LIVER BIOPSIES, SUGGESTING THE POSSIBLE ROLE OF IFI16 IN SUPPRESSING CCCDNA FUNCTION UNDER PHYSIOLOGICAL CONDITIONS. CONCLUSIONS: THE NUCLEAR SENSOR IFI16 SUPPRESSES CCCDNA FUNCTION BY INTEGRATING INNATE IMMUNE ACTIVATION AND EPIGENETIC REGULATION BY TARGETING THE ISRE OF CCCDNA, AND IFI16 MAY PRESENT AS A THERAPEUTIC TARGET AGAINST HBV INFECTION. 2020 16 3255 23 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 17 2240 33 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 18 6011 28 THE ANTIRESECTION ACTIVITY OF THE X PROTEIN ENCODED BY HEPATITIS VIRUS B. CHRONIC INFECTION OF HEPATITIS B VIRUS (HBV) IS ASSOCIATED WITH AN INCREASED INCIDENCE OF HEPATOCELLULAR CARCINOMA (HCC). HBV ENCODES AN ONCOPROTEIN, HEPATITIS B X PROTEIN (HBX), THAT IS CRUCIAL FOR VIRAL REPLICATION AND INTERFERES WITH MULTIPLE CELLULAR ACTIVITIES INCLUDING GENE EXPRESSION, HISTONE MODIFICATIONS, AND GENOMIC STABILITY. TO DATE, IT REMAINS UNCLEAR HOW DISRUPTION OF THESE ACTIVITIES CONTRIBUTES TO HEPATOCARCINOGENESIS. HERE, WE REPORT THAT HBV EXHIBITS ANTIRESECTION ACTIVITY BY DISRUPTING DNA END RESECTION, THUS IMPAIRING THE INITIAL STEPS OF HOMOLOGOUS RECOMBINATION (HR). THIS ANTIRESECTION ACTIVITY OCCURS IN PRIMARY HUMAN HEPATOCYTES UNDERGOING A NATURAL VIRAL INFECTION-REPLICATION CYCLE AS WELL AS IN CELLS WITH INTEGRATED HBV GENOMES. AMONG THE SEVEN HBV-ENCODED PROTEINS, WE IDENTIFIED HBX AS THE SOLE VIRAL FACTOR THAT INHIBITS RESECTION. BY DISRUPTING AN EVOLUTIONARILY CONSERVED CULLIN4A-DAMAGE-SPECIFIC DNA BINDING PROTEIN 1-RING TYPE OF E3 LIGASE, CRL4(WDR70) , THROUGH ITS H-BOX, WE SHOW THAT HBX INHIBITS H2B MONOUBIQUITYLATION AT LYSINE 120 AT DOUBLE-STRAND BREAKS, THUS REDUCING THE EFFICIENCY OF LONG-RANGE RESECTION. WE FURTHER SHOW THAT DIRECTLY IMPAIRING H2B MONOUBIQUITYLATION ELICITED TUMORIGENESIS UPON ENGRAFTMENT OF DEFICIENT CELLS IN ATHYMIC MICE, CONFIRMING THAT THE IMPAIRMENT OF CRL4(WDR70) FUNCTION BY HBX IS SUFFICIENT TO PROMOTE CARCINOGENESIS. FINALLY, WE DEMONSTRATE THAT LACK OF H2B MONOUBIQUITYLATION IS MANIFEST IN HUMAN HBV-ASSOCIATED HCC WHEN COMPARED WITH HBV-FREE HCC, IMPLYING CORRESPONDING DEFECTS OF EPIGENETIC REGULATION AND END RESECTION. CONCLUSION: THE ANTIRESECTION ACTIVITY OF HBX INDUCES AN HR DEFECT AND GENOMIC INSTABILITY AND CONTRIBUTES TO TUMORIGENESIS OF HOST HEPATOCYTES. 2019 19 5803 24 STING SIGNALING ACTIVATION INHIBITS HBV REPLICATION AND ATTENUATES THE SEVERITY OF LIVER INJURY AND HBV-INDUCED FIBROSIS. THE COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) OF HBV PLAYS A CRUCIAL ROLE IN VIRAL PERSISTENCE AND IS ALSO A RISK FACTOR FOR DEVELOPING HBV-INDUCED DISEASES, INCLUDING LIVER FIBROSIS. STIMULATOR OF INTERFERON GENES (STING), A MASTER REGULATOR OF DNA-MEDIATED INNATE IMMUNE ACTIVATION, IS A POTENTIAL THERAPEUTIC TARGET FOR VIRAL INFECTION AND VIRUS-RELATED DISEASES. IN THIS STUDY, AGONIST-INDUCED STING SIGNALING ACTIVATION IN MACROPHAGES WAS REVEALED TO INHIBIT CCCDNA-MEDIATED TRANSCRIPTION AND HBV REPLICATION VIA EPIGENETIC MODIFICATION IN HEPATOCYTES. NOTABLY, STING ACTIVATION COULD EFFICIENTLY ATTENUATE THE SEVERITY OF LIVER INJURY AND FIBROSIS IN A CHRONIC RECOMBINANT CCCDNA (RCCCDNA) MOUSE MODEL, WHICH IS A PROVEN SUITABLE RESEARCH PLATFORM FOR HBV-INDUCED FIBROSIS. MECHANISTICALLY, STING-ACTIVATED AUTOPHAGIC FLUX COULD SUPPRESS MACROPHAGE INFLAMMASOME ACTIVATION, LEADING TO THE AMELIORATION OF LIVER INJURY AND HBV-INDUCED FIBROSIS. OVERALL, THE ACTIVATION OF STING SIGNALING COULD INHIBIT HBV REPLICATION THROUGH EPIGENETIC SUPPRESSION OF CCCDNA AND ALLEVIATE HBV-INDUCED LIVER FIBROSIS THROUGH THE SUPPRESSION OF MACROPHAGE INFLAMMASOME ACTIVATION BY ACTIVATING AUTOPHAGIC FLUX IN A CHRONIC HBV MOUSE MODEL. THIS STUDY SUGGESTS THAT TARGETING THE STING SIGNALING PATHWAY MAY BE AN IMPORTANT THERAPEUTIC STRATEGY TO PROTECT AGAINST PERSISTENT HBV REPLICATION AND HBV-INDUCED FIBROSIS. 2022 20 6637 21 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