Parenteral viral hepatitis among students in Da Nang, Vietnam, and insights into new hepatitis B virus genotype B classification

Abstract

This cross-sectional study estimated the prevalence of hepatitis B, C, D viruses among adults aged 18-22 years and assessed the impact of viral populations on the epidemiological trends in hepatitis virus transmission. A total of 568 students of Da Nang University were enrolled in the study in 2018. The prevalence of HBsAg, anti-HBs and anti-HBc was 4.2% (24/568), 30.4% (173/568), and 17.6% (100/568), respectively. Anti-HCV was found in 0.2% (1/568) of samples, and no participants tested positive for anti-HDV. HBV DNA was detected in all HBsAg-positive samples: 19 HBV isolates belonged to genotype B, and 5-to genotype C. Eight isolates carried immune escape mutations within the S protein, and one harbored three mutations (1762A > T / 1764G > A, 1858 T > C) in the precore/core region. Most of HBV isolates belonged to subgenotype B4, which is part of the Ba global recombinant group comprising subgenotypes B2, B4 and "quasi-B3", characterized by common recombination sites between positions 1731-1846 and 2200-2252. These findings highlight the high prevalence of HBV and insufficient herd immunity against HBV within this cohort, underscoring the urgent need to expand national HBV vaccination strategies. Widespread distribution of the Ba global recombinant group emphasizes the necessity to revise the current HBV taxonomy.

Keywords: Adult aged 18–22 years; HBV / genetic diversity / classification; HCV; HDV; Prevalence; Vietnam.

Fig. 1

Phylogenetic tree of HBV isolates, based on the whole Large S gene and constructed using the Maximum-Likelihood method. Fourteen HBV isolates of this study are indicated by the red circles. Other HBV isolates are defined by GenBank accession numbers.

Fig. 2

Evolutionary relationship of studied HBV isolates belonging to genotype B. (A) Genotype B branch of Neighbor-Joining phylogenetic tree, based on the whole HBV genome sequence and generated with 1000 bootstrap replicates. HBV isolates of this study are indicated by the green circles. Other HBV isolates are defined by GenBank accession number. The reference sequences of HBV subgenotypes according to McNaughton A.L. et al. (2020) are indicated by the red rhombus. The asterisk (*) indicates the name of “quasi” clade as proposed by Shi W. et al. (2012). RG – recombinant group, NRG – nonrecombinant group. (B) Similarity plot generated for HBV isolate DN010, using genotypes B1, B6 and C2 as reference sequences, and genotype H as an outgroup. (C) Bootstrap analyses generated for HBV isolate DN010, using genotypes B1 and C2 as reference sequences, and genotype H as an outgroup. (D) Bootstrap analyses generated for HBV isolate DN010, using genotypes B3 and C2 as reference sequences, and genotype H as an outgroup.

Fig. 3

Nucleotide substitutions within the precore/core region (1698—2693 bp) of HBV isolates belonging to genotypes B (Bj_nonrecombinant (blue color) and Ba_recombinant (rose color) groups) and C (subgenotypes C1-12, C17) (yellow color). The nucleotide positions correspond to reference sequence D00329 (B1). The asterisks (**) indicate the genomic positions flanking the regions (1730 – 1846 bp and 2200 – 2253 bp) with recombination breakpoints.