Naturally Occurring Genetic Deletions or Insertions in Basal Core Promoter and PreS1 Region Do Not Critically Affect Hepatitis B Virus Replication

Abstract

Objective: Naturally occurring genetic deletions and insertions in basal core promoter (BCP) and PreS1 region of hepatitis B virus (HBV) were frequently detected in sera of chronic hepatitis B patient and these genetic variants are related to the poor response to antiviral treatment as well as the progression of liver cirrhosis and hepatocellular carcinoma. Thus, the aim of the study was to understand the effect of genetic deletions and insertions in BCP and PreS1 region on viral replication competence. Methods: HBV DNA was extracted from the sera of a chronically HBV infected patient and the whole HBV genome was amplified by PCR method. The genome was then cloned into the pCDNA3.1 vector to construct HBV-expressing plasmid, which were used to transfect HepG2 cells. The intracellular HBV DNA was detected by Southern blot method. Results: All cloned HBV genomes carried genetic deletion or insertion in the BCP and PreS1 region. However, these mutations did not seem to affect the competence of viral replication. Conclusion: Although the genetic deletion reported here may not affect the HBV replication, patients with such genetic variation should be carefully monitored during the therapy because deletions in the BCP and PreS1 are associated with progression of liver disease.