Mutation Profiling of the Hepatitis B Virus Strains Circulating in North Indian Population

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.

Characterization of Full-Length Genomes of Hepatitis B Virus Quasispecies in Sera of Patients at Different Phases of Infection

“…Regarding those mutants in specific open reading frames (ORFs), the MFI was used to give an overall estimate of the conserved and variable regions. Core and HBx peptides have been shown to be more conserved than surface and polymerase peptides (25,43). However, in our study, specific amino acid regions (aa 90 to 135 in genotype C, aa 60 to 130 in genotype B of HBcAg, and aa 131 to 135 in HBxAg) were observed to have a higher frequency of mutations or deletions in ACLF patients, followed by CHB patients.…”

“…D00330; genotype C, GenBank accession no. AB033556) using the following formula (25): MFI ϭ (x/[y ϫ z]) ϫ 100, where x represents the total number of mutations/deletions observed in the amino acid sequences, y represents the total number of samples in a group, and z represents the length of the amino acid sequence. Heat maps were generated for the individual amino acid data sets to graphically depict the distribution of mutation frequencies across the amino acid regions.…”

“…The Perl programming language was used to calculate the MFI values for each patient, and the heat maps were generated using the ggplot2 package in R language. The number of mutations per 15 amino acids was plotted on the x axis, and regions across were color-coded with red (depicting the highest mutation frequency) and green (depicting the lowest mutation frequency) (25).…”

Hepatitis B genotyping: The utility for the clinicians

“…The HBV genotype landscape in India, with its multiethnic population, is likely to be diverse. Many reports from India have documented HBV genotypes in infected individuals in specific regions of the country [61][62][63][64][65][66][67][68][69][70][71][72]. In this context, a pan-Indian study on the regional variations in HBV genotypes in this issue of the Journal is laudable [73].…”

Current Scenario of Hepatitis B and Its Treatment in India

“…This may be partially related to the relation of genotype to different viral mutations, which can influence the type of liver disease manifested. 51 , 54 , 61 , 63 Also, the patients might be harbouring different genotypes (in blood and liver tissue) simultaneously, but one could be predominant and thereby be the detectable one, as has been exemplified in (a) liver tissue harbouring genotype C whereas peripheral blood harbours genotype D, 64 (b) presence of viral reverse transcriptase mutation in treatment-naïve patients (which is genotype related 67 ) and (c) genotype switch while on therapy. 62 Genotype may also determine the mode of transmission (horizontal vs. vertical).…”