Abstract
AimsThe aim of this study was to investigate the genomic mutations in the circulating Hepatitis B virus strains causing infection in the Indian population. Further, we wanted to analyze the biological significance of these mutations in HBV mediated disease.Methods222 HBsAg positive patients were enrolled in the study. The genotype and mutation profile was determined for the infecting HBV isolate by sequencing overlapping fragments. These sequences were analyzed by using different tools and compared with previously available HBV sequence information. Mutation Frequency Index (MFI) for the Genes and Diagnosis group was also calculated.ResultsHBV Genotype D was found in 55% (n = 121) of the patient group and genotype A was found in 30% (n = 66) of samples. The majority (52%) of the HBV-infected individuals in the present study were HBeAg-negative in all the age groups studied. Spontaneous drug associated mutations implicated in resistance to antiviral therapy were also identified in about quarter of our patients, which is of therapeutic concern. The MFI approach used in the study indicated that Core peptide was the most conserved region in both genotypes and Surface peptide had highest mutation frequency. Few mutations in X gene (T36A and G50R) showed high frequency of association with HCC. A rare recombinant strain of HBV genotype A and D was also identified in the patient group.ConclusionsHBV genotype D was found out to be most prevalent. More than half of the patients studied had HBeAg negative disease. Core region was found to be most conserved. Drug Associated mutations were detected in 22% of the patient group and T36A and G50R mutations in X gene were found to be associated with HCC.
Highlights
Hepatitis B virus (HBV) is the most common cause of chronic hepatitis, Cirrhosis and Hepatocellular Carcinoma (HCC) globally [1,2]
Diagnosis of chronic HBV infection was made by documenting hepatitis B surface antigen (HBsAg) positivity at 6 month interval in each (N = 217), or by persistence presence of Anti-HBc with detectable HBV DNA in sera over 6 months duration (N = 5)
Patient’s Profile The basic demographic, virological and biochemical properties from 222 patients have been depicted in Table 1. 95 patients were found out to be HBeAg positive (43%) and 115 were HBeAg negative (52%)
Summary
Hepatitis B virus (HBV) is the most common cause of chronic hepatitis, Cirrhosis and Hepatocellular Carcinoma (HCC) globally [1,2]. HBV is a DNA Virus with 3200 nucleotides and has four Open Reading Frames (ORFs) encoding for hepatitis B surface or envelope proteins, core peptide, X peptide and DNA-polymerase enzyme. It replicates through RNA intermediate and uses a reverse transcriptase to form a c DNA. The reverse transcriptase being a poor proof reader is known to introduce synonymous (silent) as well non-synonymous substitutions in the HBV genome. Depending upon the genetic heterogeneity of HBV(.8%) 8 genotypes A through H has been identified [3,4,5,6,7,8,9,10,11]. The genotypes and the non-synonymous mutations has been reported to be clinically relevant, in the spontaneous HBeAg clearance, transmission potential, disease progression, hepatocarcinogenesis, and response to therapy [1,15,16]
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