Nucleotide sequence of precore region of hepatitis B virus DNA in HBsAg-positive carriers in Malaysia

G1896A Precore Mutation and Association With HBeAg Status, Genotype and Clinical Status in Patients With Chronic Hepatitis B

BACKGROUND

Precore stop codon (G1896A) mutation is one of the commonest mutations found in patients with chronic hepatitis B. However, over the years, this mutation was not reported much in Malaysia.

OBJECTIVES

We therefore investigated the presence of G1896A mutation in Malaysian population and its association with HBeAg status, clinical stage, hepatitis B virus (HBV) genotype and e-seroconversion rate.

PATIENTS AND METHODS

Serum samples from 93 patients confirmed as hepatitis B carriers were collected for molecular assay. The whole genome of HBV was amplified by polymerase chain reaction and directly sequenced. The precore and basal core promoter regions were analyzed for presence of mutations.

RESULTS

The most commonly observed mutation in the precore region was C1858T with 64.5% prevalence. The precore mutation of interest (G1896A) was identified in 25.8% of isolates. The basal core promoter mutations detected were A1762T-G1764A (26.9%), C1653T (8.6%), A1752G (10.8%) and C1766T (2.2%). No significant association was observed between G1896A mutation and HBeAg-negativity. Nonetheless, G1896A was highly prevalent among HBV genotype B. Clinical association revealed that subjects with G1896A mutations were mainly detected in asymptomatic chronic hepatitis B (58.3%) and liver cirrhosis (41.7%). One subject was diagnosed with fulminant hepatitis (4.2%) and 8.3% had hepatocellular carcinoma (HCC).

CONCLUSIONS

Our data suggested an intermediate prevalence of G1896A mutation among Malaysian hepatitis B carriers. The stop codon mutation has a significant association with genotype B and patients with chronic hepatitis B and liver cirrhosis.

World-wide epidemiology of HBeAg-negative chronic hepatitis B and associated precore and core promoter variants

Hepatitis B is a serious disease that is endemic in many parts of the world. A significant proportion of patients with chronic hepatitis B (CHB) are infected with a variant form of the hepatitis B virus (HBV) which decreases or abolishes the production of hepatitis B e-antigen (HBeAg). The purpose of this literature review is to describe the epidemiology of HBeAg-negative CHB (e-CHB) worldwide. A literature search was conducted to identify studies pertaining to e-CHB and underlying variants (precore and core promoter). Fifty studies were included in our analysis. The median prevalence of e-CHB among patients with chronic HBV infection was 33% in the Mediterranean, 15% in Asia Pacific, and 14% in the USA and Northern Europe. The pre core stop codon variant was detected in a median of 60% (range 0-100%) of HBeAg-negative patients overall, 92% in the Mediterranean, 50% in Asia Pacific and 24% in the USA and Northern Europe. There were very few data on the prevalence of core promoter variants outside Asia where the median prevalence among HBeAg-negative patients was 77%. This literature review revealed that e-CHB is more common than previously suspected and that it is present worldwide with marked variations in the prevalence of associated HBV variants across different geographical regions. Additional research using population based samples of adequate size based on a consensus definition of e-CHB and using standardized HBV DNA assays is needed to better estimate the true prevalence of e-CHB and its associated HBV variants.

Human hepatitis B virus mutants: significance of molecular changes

Human hepatitis B virus, the leading pathogen for hepatitis B, is a compact DNA virus with viral genes that largely overlap. An increasing number of mutations have emerged following human interventions such as vaccination and anti-viral therapy. While vaccine escape mutants are characterized by mutations on the antigenic hepatitis B surface antigen, those carrying mutations in other viral proteins are either resistant to anti-viral therapy or implicated in acute liver diseases. Molecular identification of these various mutants should shed new lights on the underlying mechanism of hepatitis B virus viral escape and resistance and provide helpful information on their effective eradication.