Sequence Analysis of PreS2 Region of Hepatitis B Virus Genotype D Isolates

Abstract

Hepatitis B virus (HBV) is a well known agent of liver diseases. HBV disease burden varies across the
globe with regions from low to high endemicity. Pakistan lies in the intermediate endemic zone, with
high rate of mortality due to liver disease, cirrhosis and hepatocellular carcinoma. There is a wide range
of heterogeneity in relation to HBV genotypes and sub-genotypes and in their patterns of pathogenesis,
virulence and response to antiviral therapy. A large number of HBV genomic variations are associated
with clinical outcomes such as hepatocellular carcinoma and liver cirrhosis. Thus, the present study aims
to analyze PreS2 gene sequences from HBV isolates and their phylogeny. To investigate this, a study was
conducted on twenty one HBV chronically infected individuals, serum samples were subjected to PCR
with specific primers for PreS2 region of HBV genotype D and then sequenced. Point mutations: A39V,
P41H and L42I were found in cell permeability domain of PreS2 protein. However, MHC class I and II
epitopes were conserved in all sequences. Phylogenetic analysis was carried out by comparing the
nucleotide sequence with 22 reference sequences of HBV sub-genotype D retrieved from the GeneBank.
Phylogenetic analysis showed that two of our isolates, ASAB1 (2266) and ASAB3 (PIMS 7) shared
cluster 1 with China D1, Pakistan D1, Iran D1 and Turkey D1. Meanwhile, ASAB2 (HF2) was grouped in
cluster 2 with Lebanese D2 and Brazil D2.