Naturally occurring core internal deletion mutations of hepatitis B virus gene in chronic genotype B-infected adult

This study aimed to investigate the prevalence of the core internal deletion (CID) mutations in the genome of hepatitis B virus (HBV) from chronically HBV-infected adults in Nanchang city and to elucidate the location of the CID in the HBV genome. PCR was applied to amplify the DNA region containing the enhancer II and the core promoter and the pre-C/C gene from the sera of 205 patients with chronic hepatitis B. Eight patients (3.90%, 8/205) had two products including a smaller band and a band of the expected 840 bp. Only two patients (0.98%, 2/205) had a smaller band. The presence of the CID mutation was determined in all smaller products amplified from 10 patients (4.88%, 10/205) based on the sequence analysis. Seven patients had a single in-frame deletion whose size is various, covering codon 78-136 in the core gene. Three patients had two or three separated deletions in the core gene. The separated deletions, respectively, covering codons 95-98/94-110 and codons 106-126/122-132 in the core gene were identified from two patients of the three. Another patient of the three had separated deletions of nt2180-2203 and nt2255-2332 in the core gene. The deletion of nt2255-2332 was frameshift, resulting in the loss of codons 119-144, which overlaps the first eight codons (P, L, S, Y, Q, H, F, R) in the 5-terminus of the P gene. Immunoepitope mapping showed that all CID sequences encompassed T-cell and B-cell epitopes in the core protein, which suggests that the CID may facilitate immune escape and contribute to chronic infection. Copyright (C) 2016 Wolters Kluwer Health, Inc. All rights reserved.