Hepatitis B virus infection--natural history and clinical consequences

Histopathology and clinical correlates of end-stage hepatitis B cirrhosis: a possible mechanism to explain the response to antiviral therapy

In chronic liver disease associated with histological necroinflammation, clinical severity is frequently greater in those with higher grades of activity. Conventional wisdom assumes that necroinflammation is mild or absent in patients with end-stage hepatitis B virus (HBV) cirrhosis due to the frequent presence of mildly elevated aminotransferase levels, the absence of hepatitis B e antigen (HBeAg), and low or undetectable HBV deoxyribonucleic acid (DNA) levels. However, a histopathologic analysis of such patients has not been undertaken. The aims of this study were 1) to assess severity and histological features of inflammation, 2) to correlate the severity of inflammation with biochemical and virologic parameters, and 3) to define the relationship between inflammation and clinical severity in explanted livers from patients undergoing liver transplantation for HBV cirrhosis. Characteristics of 34 consecutive patients undergoing liver transplantation for HBV cirrhosis were correlated with inflammation and immunohistological findings in the explanted livers. High-grade inflammation (grades 3 and 4) was found in many cases (47.1% interface hepatitis; 14.8% lobular inflammation; and 20.6% portal inflammation). The presence of positive cytoplasmic staining for hepatitis B core antigen (HBcAg) was associated with grade 3 or 4 interface hepatitis (P = .046) and lobular hepatitis (P = .005). There was no correlation between inflammatory activity and age, Asian ethnicity, aminotransferase levels, total bilirubin levels, HBeAg seropositivity, and detectable HBV DNA level. Patients with high-grade inflammation had greater degrees of hepatic decompensation. In conclusion, high-grade inflammation is common in end-stage HBV cirrhosis, but it is not readily detected by biochemical and virologic parameters. High-grade inflammation is associated with a greater degree of hepatic decompensation.

Characterization of nonconventional hepatitis B viruses lacking the core promoter

The core gene (C-gene) promoter and regulatory sequences play a central role in the hepatitis B virus (HBV) life cycle. They are essential for the synthesis of the pregenomic and precore mRNA. The pregenomic RNA is the template required for replication and also the template for the synthesis of the core protein and polymerase. Here, we report the in vivo existence and functional characterization of HBV variants that lack the C-gene promoter region and the regulatory sequences located therein. HBV promoter fragments were isolated by PCR from sera of chronic carriers and characterized. Truncated promoter elements were identified, and then tested in the context of wild-type genomes in the HuH-7 cell line. The expression of the recombinant HBV genome resulted in the synthesis of surface proteins, and low level of core protein as well as a transcript pattern similar to, but smaller in size to wild-type virus. The recombinant HBV genome with the truncated promoter region produced pregenomic RNA-like transcripts. These transcripts were encapsidated and reverse transcribed when complemented by sufficient core and polymerase protein. These date provide an explanation as to why such deletion mutants of HBV can be produced at all, they highlight the functional potentials of viral sequences activated by mutations and may be of relevance for viral evolution and persistence.

The conserved amino-terminal region (amino acids 1–20) of the hepatitis B virus X protein shows a transrepression function

The X protein of hepatitis B virus or HBx is a multifunctional regulatory protein that carries the fame of a promiscuous transactivator. Although, the N-terminal 'A' region of HBx (amino acids 1-20) is the most conserved region among mammalian hepadnavirus genomes, it has been found to be dispensable for transactivation function [Proc. Natl. Acad. Sci. U.S.A. 93, 1996, 5647]. To elucidate its biological role, DNA sequence corresponding to the A region of X gene was amplified by polymerase chain reaction and cloned as a 72 base pair HBx mutant X17. In order to augment the intracellular biochemical stability of the expressed protein, the monomeric X17 was multimerized and 2-10 units long tandem repeats of the A region (X17-n) were cloned in a mammalian expression vector. Expression of the X17 constructs was confirmed by in vitro transcription and translation, as well as by RT-PCR after transfection in hepatoma cells. The function of X17 was investigated using the chloramphenicol acetyl transferase reporter constructs of viral (RSV-LTR, HIV1-LTR and HBx) and cellular gene promoters (c-Jun and epidermal growth receptor). Not only did the X17 multimers inhibit the HBx-mediated transactivation of all the reporter genes, but also their basal activities. The inhibition was dependent on the amount of X17 plasmid transfected in cells as well as on the number of repeat units present in the X17 expression vectors. Further, the X17-related inhibition of transactivation was not a cytotoxic effect. Thus, our data suggests that the N-terminal 'A' domain of HBx has a negative regulatory function.

Low rate of occult hepatitis B virus infection among anti-HBc positive blood donors living in a low prevalence region in Brazil

OBJECTIVE

The aim of this study was to determine the rate of occult hepatitis B virus (HBV) infection among blood donors living in a geographic region of low (5.6%) anti-HBc prevalence.

SUBJECTS AND METHODS

Sera from 150 candidate blood donors whose blood was rejected due to total anti-HBc reactivity (despite absence of HBsAg) were tested for anti-HBs and IgM anti-HBc antibodies, as well as for HBeAg/anti-HBe. Serum HBV DNA was sought by using a PCR assay able to amplify part of the surface gene. Viral load was measured in the PCR positive samples.

RESULTS

The pattern 'anti-HBc alone' (without HBsAg and anti-HBs antibodies) was found in 64 (42.7%) subjects. IgM anti-HBc and anti-HBe antibodies were detected in 2 (1.3%) and 80 (53.3%) samples, respectively. No sample was HBeAg-reactive. HBV DNA was repeatedly found in five (3.3%) samples, three of which were anti-HBs positive and two anti-HBs negative. All five HBV DNA positive samples showed a low viral load (<1000copies/ml).

CONCLUSIONS

The data indicated a low rate of occult infection among anti-HBc positive, HBsAg negative blood donors living in a region of low prevalence of infection. Viral load was very low in all HBV infected subjects.