G. Raffa

Nuclear HBx binds the HBV minichromosome and modifies the epigenetic regulation of cccDNA function

HBV cccDNA, the template for transcription of all viral mRNAs, accumulates in the nucleus of infected cells as a stable episome organized into minichromosomes by histones and non-histone viral and cellular proteins. Using a cccDNA-specific chromatin immunoprecipitation (ChIP)-based quantitative assay, we have previously shown that transcription of the HBV minichromosome is regulated by epigenetic changes of cccDNA-bound histones and that modulation of the acetylation status of cccDNA-bound H3/H4 histones impacts on HBV replication. We now show that the cellular histone acetyltransferases CBP, p300, and PCAF/GCN5, and the histone deacetylases HDAC1 and hSirt1 are all recruited in vivo onto the cccDNA. We also found that the HBx regulatory protein produced in HBV replicating cells is recruited onto the cccDNA minichromosome, and the kinetics of HBx recruitment on the cccDNA parallels the HBV replication. As expected, an HBV mutant that does not express HBx is impaired in its replication, and exogenously expressed HBx transcomplements the replication defects. p300 recruitment is severely impaired, and cccDNA-bound histones are rapidly hypoacetylated in cells replicating the HBx mutant, whereas the recruitment of the histone deacetylases hSirt1 and HDAC1 is increased and occurs at earlier times. Finally, HBx mutant cccDNA transcribes significantly less pgRNA. Altogether our results further support the existence of a complex network of epigenetic events that influence cccDNA function and HBV replication and identify an epigenetic mechanism (i.e., to prevent cccDNA deacetylation) by which HBx controls HBV replication.

Molecular and functional analysis of occult hepatitis B virus isolates from patients with hepatocellular carcinoma.

Occult HBV infection is characterized by the persistence of HBV DNA in the liver of individuals negative for HBV surface antigen (HBsAg). Occult HBV may exist in the hepatocytes as a free genome, although the factors responsible for the very low viral replication and gene expression usually observed in this peculiar kind of infection are mostly unknown. Aims of this study were to investigate whether the viral genomic variability might account for the HBsAg negativity and the inhibition of the viral replication in occult HBV carriers, and to verify in vitro the replication capability of occult HBV strains. We studied liver viral isolates from 17 HBV patients, 13 with occult infection and 4 HBsAg‐positive. Full‐length HBV genomes from each case were amplified and directly sequenced. Additionally, full‐length HBV DNA from eight occult‐HBV and two HBsAg‐positive cases were cloned and sequenced. Finally, three entire, linear HBV genomes from occult cases were transiently transfected in HuH7 cells. Direct sequencing showed the absence of mutations capable of interfering with viral replication and gene expression in the major viral population of each case. Cloning experiments showed highly divergent HBV strains both in HBsAg‐positive and HBsAg‐negative individual cases (range of divergence 1.4%‐7.1%). All of the 3 transfected full‐length HBV isolates showed normal patterns of replication in vitro. Conclusion: Multiple viral variants accumulate in the liver of occult HBV‐infected patients. Occult HBV strains are replication‐competent in vitro, suggesting that host, rather than viral factors are responsible for cryptic HBV infection. (HEPATOLOGY 2007;45:277–285.)

The Characteristics of the Cell-Mediated Immune Response Identify Different Profiles of Occult Hepatitis B Virus Infection

BACKGROUND & AIMS Hepatitis B virus (HBV) DNA detection in serum and/or in the liver of hepatitis B surface antigen (HBsAg)-negative patients with or without serologic markers of previous viral exposure is defined as occult HBV infection. Because the role of the adaptive response in keeping HBV replication under control in occult infection still is undefined, this study was performed to characterize the features of the HBV-specific T-cell response in this condition. METHODS HBV-specific T-cell frequency and function were tested ex vivo and after in vitro expansion in 32 HBsAg-negative patients undergoing diagnostic liver biopsy for chronic hepatitis C: 18 with occult HBV infection (11 anti-HBc-negative and 7 anti-HBc-positive patients) defined by the detection of intrahepatic HBV DNA by polymerase chain reaction; 14 without detectable intrahepatic HBV DNA (5 anti-HBc-positive and 9 anti-HBc-negative patients). Six patients with chronic hepatitis B and 7 HBsAg-inactive carriers were studied for comparison. RESULTS The presence or absence of serologic HBV markers defined 2 profiles of HBV-specific T-cell responses in occult infection. Anti-HBc-positive patients showed a T-cell response typical of protective memory, suggesting that this condition represents a resolved infection with immune-mediated virus control. In contrast, HBV-specific T cells in anti-HBc-negative patients did not readily expand and produce interferon-gamma in vitro, suggesting the possibility of a low-dose infection insufficient to allow maturation of protective memory. CONCLUSIONS Our results suggest different mechanisms of control of viral replication in seropositive and seronegative occult infections. Additional studies aimed at understanding possible different clinical implications are needed.

Impact of hepatitis B virus (HBV) preS/S genomic variability on HBV surface antigen and HBV DNA serum levels

To evaluate whether hepatitis B virus (HBV) preS/S gene variability has any impact on serum hepatitis B surface antigen (HBsAg) levels and to analyze the replication capacity of naturally occurring preS/S variants, sera from 40 untreated patients with HBV‐related chronic liver disease (hepatitis B e antigen [HBeAg]‐positive, n = 11; HBeAg‐negative, n = 29) were virologically characterized. Additionally, phenotypic analysis of three different preS/S variant isolates (carrying a 183‐nucleotide deletion within the preS1 region, the deletion of preS2 start codon, and a stop signal at codon 182 within the S gene, respectively) was performed. HBV infecting 14 (35%) patients had single or multiple preS/S genomic mutations (i.e., preS1 and/or preS2 deletions, preS2 start codon mutations, C‐terminally truncated and/or “a” determinant mutated S protein). Presence of preS/S variants negatively correlated with HBsAg titers (r = −0.431; P = 0.005) and its prevalence did not significantly differ between HBeAg‐positive and HBeAg‐negative patients. No correlation was found between HBsAg and HBV DNA levels in patients infected with preS/S mutants, whereas a significant correlation was found between HBsAg and viremia levels (r = 0.607; P = 0.001) in patients infected with wild‐type HBV strains. HepG2 cells replicating the above‐mentioned three preS/S variants showed significant reduction of HBsAg secretion, retention of envelope proteins in the endoplasmic reticulum, less efficient virion secretion and nuclear accumulation of significantly higher amounts of covalently closed circular DNA compared with wild‐type HBV replicating cells. Conclusion: In patients infected with preS/S variants, HBV DNA replication and HBsAg synthesis/secretion appear to be dissociated. Therefore, the use of HBsAg titer as diagnostic/prognostic tool has to take into account the frequent emergence of preS/S variants in chronic HBV infection. (HEPATOLOGY 2012;)

Replicative and Transcriptional Activities of Hepatitis B Virus in Patients Coinfected with Hepatitis B and Hepatitis Delta Viruses

ABSTRACT Hepatitis B virus (HBV) and hepatitis delta virus (HDV) interplay was investigated by examining liver and serum samples from 21 coinfected and 22 HBV-monoinfected patients with chronic liver disease. Different real-time PCR assays were applied to evaluate intrahepatic amounts of HBV DNA, covalently closed circular DNA (cccDNA), pregenomic RNA (pgRNA), pre-S/S RNAs, and HDV RNA. Besides HBV DNA and HDV RNA levels, HBsAg concentrations in the sera were also determined. HDV-coinfected cases showed significantly lower median levels of serum HBV DNA (−5 log), intrahepatic relaxed-circular DNA (−2 log), and cccDNA (−2 log) than those of HBV-monoinfected cases. Interestingly, pgRNA and pre-S/S RNA amounts were significantly lower (both −1 log) in HDV-positive patients, whereas serum HBsAg concentrations were comparable between the two patient groups. Pre-S/S RNA and HBsAg amounts per cccDNA molecule were higher in HDV-positive patients (3-fold and 1 log, respectively), showing that HBV replication was reduced, whereas synthesis of envelope proteins was not specifically decreased. The ratios of cccDNA to intracellular total HBV DNA showed a larger proportion of cccDNA molecules in HDV-positive cases. For these patients, both intrahepatic and serum HDV RNA amounts were associated with cccDNA but not with HBsAg or HBV DNA levels. Finally, HBV genomes with large deletions in the basal core promoter/precore region were detected in 5/21 HDV-positive patients but in no HDV-negative patients and were associated with lower viremia levels. These findings provide significant information about the interference exerted by HDV on HBV replication and transcription activities in the human liver.

Virological profiles in patients with chronic hepatitis C and overt or occult HBV infection

OBJECTIVES:The virological profiles of hepatitis B and C viruses (HBV and HCV) and their interplay in cases of coinfection are undefined. A suppressed and occult HBV infection may occur in hepatitis B surface antigen (HBsAg) negative patients with chronic hepatitis C. The HCV core protein is able to inhibit HBV “in vitro,” and serines at positions 99 and 116 are essential for such inhibition. We aimed to assess the HBV and HCV virological profiles in cases of coinfection and to evaluate the relationship between HCV core gene variability and HBV activity.METHODS:Eighty-two anti-HCV positive patients were examined: 35 cases were HBsAg positive, 24 were HBsAg negative with “occult” HBV infection, and 23 were HBV negative. HBV and HCV viremia levels were evaluated in all cases. HCV genomic region coding for the aminoacid sequence 99–116 of core protein was amplified and sequenced in all HCV RNA positive cases. The entire core gene was amplified and sequenced in three randomly selected cases.RESULTS:Serum HCV RNA was detected in all cases but 13, all HBsAg positive individuals; HCV viremia levels of the other 22 HBsAg positive subjects were similar to those detected in HBsAg negative patients with or without occult HBV infection. Among the 35 HBsAg positive patients both HBV DNA and HCV RNA were detected in five cases, HCV RNA alone in 17, and HBV DNA alone in six, whereas seven cases had undetectable levels of both viruses. Sequencing analyses showed that the HCV core gene was highly preserved in all patients.CONCLUSION:A wide spectrum of HCV and HBV virological patterns may occur in a case of coinfection. HCV core variability is not related to HBV activity “in vivo.”

Hepatitis B virus (HBV) DNA integration in patients with occult HBV infection and hepatocellular carcinoma

Hepatitis B virus (HBV) DNA integration in the host genome is a major mechanism responsible for the etiopathogenetic role exerted by HBV in hepatocellular carcinoma (HCC) development. Extensive analyses evaluating viral integration in HBV surface antigen (HBsAg) negative patients with occult HBV infection (OBI) have not yet been performed. The aim of this study was to investigate and characterize HBV DNA integration in HCC tissues from OBI patients.

Hepatitis B virus (HBV) induces the expression of interleukin-8 that in turn reduces HBV sensitivity to interferon-alpha

High levels of serum interleukin-8 (IL-8) have been detected in chronic hepatitis B (CHB) patients during episodes of hepatitis flares. We investigated whether hepatitis B virus (HBV) may directly induce IL-8 production and whether IL-8 may antagonize interferon-alpha (IFN-α) antiviral activity against HBV. We showed that CHB patients had significantly higher IL-8 levels both in serum and in liver tissue than controls. In HBV-replicating HepG2 cells, IL-8 transcription was significantly activated. AP-1, C/EBP and NF-kB transcription factors were concurrently necessary for maximum IL-8 induction. Moreover, HBx viral protein was recruited onto the IL-8 promoter and this was paralleled by IL8-bound histone hyperacetylation and by active recruitment of transcriptional coactivators. Inhibition of IL-8 increases the antiviral activity of IFN-α against HBV. Our results indicate that HBV activates IL-8 gene expression by targeting the epigenetic regulation of the IL-8 promoter and that IL-8 may contribute to reduce HBV sensitivity to IFN-α.

Proliferation of primary human hepatocytes and prevention of hepatitis B virus reinfection efficiently deplete nuclear cccDNA in vivo

Objective The stability of the covalently closed circular DNA (cccDNA) in nuclei of non-dividing hepatocytes represents a key determinant of HBV persistence. Contrarily, studies with animal hepadnaviruses indicated that hepatocyte turnover can reduce cccDNA loads but knowledge on the proliferative capacity of HBV-infected primary human hepatocytes (PHHs) in vivo and the fate of cccDNA in dividing PHHs is still lacking. This study aimed to determine the impact of human hepatocyte division on cccDNA stability in vivo. Methods PHH proliferation was triggered by serially transplanting hepatocytes from HBV-infected humanised mice into naïve recipients. Cell proliferation and virological changes were assessed by quantitative PCR, immunofluorescence and RNA in situ hybridisation. Viral integrations were analysed by gel separation and deep sequencing. Results PHH proliferation strongly reduced all infection markers, including cccDNA (median 2.4 log/PHH). Remarkably, cell division appeared to cause cccDNA dilution among daughter cells and intrahepatic cccDNA loss. Nevertheless, HBV survived in sporadic non-proliferating human hepatocytes, so that virological markers rebounded as hepatocyte expansion relented. This was due to reinfection of quiescent PHHs since treatment with the entry inhibitor myrcludex-B or nucleoside analogues blocked viral spread and intrahepatic cccDNA accumulation. Viral integrations were detected both in donors and recipient mice but did not appear to contribute to antigen production. Conclusions We demonstrate that human hepatocyte division even without involvement of cytolytic mechanisms triggers substantial cccDNA loss. This process may be fundamental to resolve self-limiting acute infection and should be considered in future therapeutic interventions along with entry inhibition strategies.

Analysis of occult hepatitis B virus infection in liver tissue of HIV patients with chronic hepatitis C.

Objective:Current data on the prevalence of occult hepatitis B virus (HBV) infection in HIV-positive individuals conflict. As occult HBV infection could have an impact on the outcome of liver disease in HIV-positive patients, we investigated a large number of HIV-positive/HBV-surface-antigen (HBsAg) negative subjects with hepatitis C virus (HCV) infection by using the ‘gold standard’ approach for occult HBV detection—analysis of liver DNA extracts. Methods:The presence or absence of HBV DNA was determined by PCR testing of four different viral genomic regions in DNA extracts of needle liver biopsy specimens of 101 HBsAg negative individuals with HIV/HCV co-infection. HBV genotyping was performed by sequencing analysis of the preS-S gene in occult HBV isolates from 18 cases. Results:Occult HBV infection was diagnosed in 42 of the 101 cases (41%). No clinically relevant difference was found between occult HBV-positive and -negative patients. HBV genotype D and A were detected, respectively, in 11 (61%) and 7 (39%) of 18 cases analysed. Conclusions:Occult HBV infection frequently occurs in HIV/HCV co-infected patients indicating the importance of performing prospective studies able to clarify its clinical impact in these patients. HBV genotype A is highly prevalent in HIV-infected subjects with occult HBV infection in a similar way to HBsAg/HIV-positive individuals.