Investigation of DNA Sequence in the Basal Core Promoter, Precore, and Core Regions of Hepatitis B Virus from Tunisia Shows a Shift in Genotype Prevalence

Abstract

BackgroundIn this study, we evaluated the prevalence of the most common mutations occurring in Enhancer II (EnhII), Basal Core Promoter (BCP), Precore (PC), and Core (C) regions of hepatitis B virus (HBV) genome.ObjectivesWe also investigated the correlation between HBV variants, their genotypes, and patients’ HBe antigen (HBeAg: soluble shape of the capsid antigen) status.Patients and MethodsWe retrieved viral DNA from 40 serum samples of Tunisian patients positive for hepatitis B surface antigen (HBsAg) and HBV DNA, amplified the above mentioned regions using specific primers, and sequenced the corresponding PCR (polymerase chain reaction) products. For further analysis purpose, the patients were divided into two groups: Group1 including 34 HBeAg-negative patients and Group2 with 6 HBeAg-positive patients.ResultsTwenty-one patients (52.5%) showed PC G1896A mutation and 11 (27.5%) carried A1762T/G1764A double mutations. These mutations were more frequent in HBeAg-negative patients than that in HBeAg-positive ones. Indeed, 58.8% of patients bearing G1896A mutation were HBeAg-negative while 16.7% were positive. In patients bearing T1762/A1764 double mutation, 29.4% were positive and 16.7% were negative. In addition, the A1896 mutation was restricted to HBV isolates that had wild-type T1858, while C1858 was rather linked to the occurrence of T1762/A1764 mutation. Interestingly, this study revealed a high frequency of genotype E. This frequency was important as compared to that of genotype D known to be predominant in the country as delineated in previous studies.ConclusionsPrevious results supported and showed that HBV strains present in Tunisia belonging to genotype D and, to a lesser extent, to genotype E, were prone to mutations in BCP/ PC regions. This observation was more obvious in HBV isolates from asymptomatic chronic carriers (AsC). The high mutational rates observed in our study might result from a mechanism of viral escape that plays an important role in the loss of HBeAg.

Analysis of HBV basal core promoter/precore gene variability in patients with HBV drug resistance and HIV co-infection in Northwest Ethiopia

“…Similarly, all sorts of PC mutant variants so far described and functionally known as the start codon mutations (A1814C/C1816; 15.4%) that abolish HBeAg expression [ 33 ] and G1862T (44.8%) mutation that interferes with post-translational modification of the HBeAg-precursor [ 34 , 35 ] were most common. Interestingly, the premature stop codon (G1896A) that is known to abolish the synthesis of HBeAg [ 36 , 37 ] in particular with C1858T was found to be 21.7% and commonly found in subjects with genotype D. In addition, finding a case with no multiple mutations from BCP and PC genes were difficult in the current study. However, the observation of the inverse relationship between the BCP double mutations and PC stop codon mutation was in line to a study that reported the co-existence of PC stop codon mutation might influence the BCP mutations [ 38 ].…”

“…These could also be an indication of a wild-type mixed HBV viral population infection, but with BCP/PC mutant variants [ 39 ]. In addition, the development of such mutant variants in both HBeAg positive and negative case could be the result of the synergistic effect of different mutation profiles or genotype differences [ 37 , 40 ]. In the current study, such mutant profiles were particularly seen in association with genotype D except for the double BCP mutations.…”

Hepatitis B virus depicts a high degree of conservation during the immune‐tolerant phase in familiarly transmitted chronic hepatitis B infection: deep‐sequencing and phylogenetic analysis

“…However, despite this viral genomic stability, it was necessary to explain the variation in HBV genomic sequences after intrafamilial transmission occurred. In this sense, it is necessary to consider that HBV isolates from genotype D1 appear to be prone to mutations in BCP‐PC regions . For that reason, two genomic regions were targeted for amplification, sequencing and phylogenetic inferences.…”

Molecular identification of hepatitis B virus genotypes/subgenotypes: Revised classification hurdles and updated resolutions

“…In Bolivia, the exchange of native HBV subgenotype F4 and exotic ones (subgenotypes B2 and C2) between Bolivian and Japanese immigrants was clearly demonstrated by phylogenetic analysis [151] . Interestingly, the exotic strains have different mutational patterns in different ORFs of HBV [123] , which would have a different impact on the course of infection, therapeutic, diagnostic and prophylactic measures [152,153] .…”

“…Although the genotype D of HBV is distributed globally, its subgenotypes are locally confined to certain geographical regions. For example, subgenotype D1 is restricted to Iran and its neighboring countries [116,[122][123][124][125][126] . Subgenotype D2 is derived from East Europe and Russia, D3 was detected in Serbia, South Africa and Alaska, D4 was found in Oceania and Somalia, and D5-D9 were reported from India, Indonesia Tunisia and Nigeria [67] .…”