Abstract
The present study was carried out to identify the hepatitis B virus (HBV) genotypes in six patients attending the surgical clinic who were positive for hepatitis B surface antigen. DNA was extracted from the serum of patients and subjected to a modified nested PCR to detect a 585 bp region within the S gene of the HBV genome. Positive PCR products were purified and sequenced via a cycle sequencing method. The sequence data were analyzed with reference sequences in the HepSEQ database to identify the particular HBV genotype of the samples. Nested PCR for the S gene of the HBV genome was positive in 2 out of 6 samples. The genotyping and sequence analysis of the PCR products showed HBV genotype A with a homology of 98% to the reference sequences in the HepSeq database.
Highlights
Hepatitis B virus (HBV) is an enveloped DNA virus that infects the hepatocytes of humans
Genotyping and sequence analysis carried out on one positive sample revealed a sequence of 517 bps with a 97.49% homology to reference sequences of HBV genotype A
The other positive sample revealed a sequence of 235 bps with a 97.86% homology to reference sequences of HBV genotype A (Figure 2)
Summary
Hepatitis B virus (HBV) is an enveloped DNA virus that infects the hepatocytes of humans. Sequencing and phylogenetic studies of the genome indicate the existence of eight distinct genotypes (AH) and numerous sub types of HBV. These genotypes and sub types have risen from nucleotide substitution mutations occurring at an estimated rate of 1.4-3.2×10 ̄5 per year due to the low proof reading capability of the viral polymerase during replication. Replication of the HBV genome unlike other DNA viruses occurs via an intermediate RNA synthesis process involving the action of an error prone viral reverse transcriptase giving rise to mutations at a higher rate compared to that of other DNA viruses. A more efficient and accurate method involving the amplification of a target region encompassing genotypic variability, followed by sequence analysis for genotype identification would be a more appropriate method. This study has used such a method by targeting the HBV S gene for genotypic variability
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