Different mutation rates in the basal core promoter and precore regions between hepatitis B virus subgenotype F1b clusters.

Hepatitis B virus (HBV) is the main etiological agent of hepatocellular carcinoma (HCC) worldwide. It has been classified into nine genotypes and several subgenotypes, with uneven global distribution. There is growing evidence that the viral genotype influences the course and outcome of chronic hepatitis B infection. Two evolutionarily different clusters of the subgenotype F1b, called basal and cosmopolitan, have been described. The two clusters have constrained geographical distribution, with the particular feature that the basal cluster is present in regions of high HCC incidence, while the Cosmopolitan cluster is found in regions of low HCC incidence. The BCP/pC region was sequenced in 68 cases chronically infected with the F1b subgenotype to determine if there was a differential pattern of pathogenic-associated mutations between both clusters. Twenty-two of the 68 cases belonged to the subgenotype F1b basal cluster and 46 to the cosmopolitan cluster. Among the HBeAg-negative patients the A1762T/G1764A and G1896A mutations were more frequently found in the basal samples (85.7 and 92.9%) compared to the cosmopolitan ones (50 and 18.2%). Interestingly, no HBeAg loss-associated mutations were observed in 7.1 and 36.4% of the basal and cosmopolitan cases, respectively. The different rate of mutations associated with a more severe course of chronic hepatitis in the basal cluster would support the difference in the HCC incidence rate in the geographical regions where the basal cluster is restricted.

Impact of core protein naturally selected mutants associated with HBeAg-negative status in HBV biosynthesis.

Hepatitis B e antigen (HBeAg) loss represents a late stage of chronic hepatitis B virus (HBV) infection associated with a drastic decrease in HBV-DNA, a lower risk of disease progression, and the occurrence of several mutations in the preCore/core region. However, the underlying mechanisms supporting the downregulation of viral replication have yet to be elucidated. In the present study, the analysis of the frequency of subgenotype D1 core protein (HBc) mutations associated with HBeAg status revealed a higher mutation rate in HBeAg-negative sequences compared to HBeAg-positive ones. Particularly, 22 amino acids exhibited a higher frequency of mutation in HBeAg-negative sequences, while the remaining residues showed a high degree of conservation. Subsequently, the assessment of HBc mutants derived from HBeAg-negative patients in viral structure and replicative capacity revealed that HBc mutations have the ability to modulate the subcellular localization of the protein (either when the protein was expressed alone or in the context of viral replication), capsid assembly, and, depending on specific mutation patterns, alter covalently closed circular DNA (cccDNA) recycling and up- or downregulate viral replication. In conclusion, HBc mutations associated with HBeAg-negative status impact on various stages of the HBV life cycle modulating viral replication during the HBeAg-negative stage of infection.

Intrahepatic immune infiltrate in chronic hepatitis B and chronic hepatitis C: Similar but not the same.

In chronic hepatitis B (CHB) and C (CHC) infections, the composition of the immune cell microenvironment at the site of infection is poorly understood. Thus, our aim was to characterize and compare liver infiltrates to identify shared and exclusive hepatic immune components. Immunohistochemistry was performed on 26 CHB and 42 CHC liver biopsies to determine Th (CD4+), Th1 (T-bet+), Th17 (IL-17A+), Treg (Foxp3+) and CTL (CD8+) cells frequency in portal/periportal and intralobular areas and relate them to liver damage. CHB and CHC cases shared a portal/periportal CD4+ lymphocyte predominance and a lobular CD8+ lymphocyte majority. However, CHC exhibited a concomitant lobular T-bet+ cell dominance while in CHB FoxP3+ cells prevail. CHC disclosed higher frequencies of P/P FoxP3+, IL-17A+ and T-bet+ cells and intralobular CD4+, IL-17A+ and T-bet+ lymphocytes. HBeAg+ chronic hepatitis and CHC cell frequencies were similar except for lobular T-bet+ that remained higher among CHC cases. Comparison among cases with less severe liver disease revealed lower lymphocyte frequencies in CHB samples, while no differences were observed between patients with more severe stages. Interestingly, in CHB portal/periportal CD4+ and lobular CD4+, CD8+ and IL-17A+ cells were associated with severe hepatitis. Even when all studied populations were identified in both infections preferential lymphocyte frequencies and prevalence at different areas along with their association with liver damage highlighted that CHB and CHC immune responses are not the same.