title: Hepatitis B e Antigen Expression by Hepatitis B Virus Subgenotype A1 Relative to Subgenotypes A2 and D3 in Cultured Hepatocellular Carcinoma (Huh7) Cells.
abstract: BACKGROUND
  Hepatitis B virus (HBV) is hyperendemic in southern Africa, with subgenotype A1 prevailing. The precore/core (preC/C) region of A1, encoding for hepatitis B e antigen (HBeAg), has unique sequence characteristics, differentiating it from subgenotypes A2 and D3. Our aim was to follow the expression of HBeAg in vitro by the three subgenotypes.
  
  
  METHODS
  Huh7 cells were transfected with plasmids belonging to subgenotypes A1, A2, and D3. Using indirect immunofluorescence, the expression of HBeAg was followed, as was the activation of the unfolded protein response (UPR) and subsequent activation of apoptosis.
  
  
  CONCLUSIONS
  Following transfection with D3, HBeAg passed through the secretory pathway earlier than cells transfected with genotype A. Cells transfected with A1 showed a lower expression of the preC/C precursor in the secretory pathway and a higher co-localization in the nucleus. Cells transfected with A1 showed greater endoplasmic reticulum (ER) stress and an earlier, prolonged activation of the UPR seen by the higher activity of three ER-localized transmembrane transducers (double-stranded RNA-dependent protein kinase-like ER kinase, activating transcription factor 6, and inositol-requiring enzyme 1), on day 3 compared to day 5. Moreover, our study also found that cells transfected with A1 had increased apoptosis.
authors.affiliation: Hepatitis Virus Diversity Research Unit, Department of Internal Medicine, School of Clinical Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Nimisha Harshadrai
authors.initials: NH
authors.lastname: Bhoola
authors.forename: Anna
authors.initials: A
authors.lastname: Kramvis
mesh_terms: D051702:Activating Transcription Factor 6 / Q000235:genetics; D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000821:virology; D045744:Cell Line, Tumor; D059865:Endoplasmic Reticulum Stress; D005838:Genotype; D006513:Hepatitis B e Antigens / Q000235:genetics* / Q000378:metabolism; D006515:Hepatitis B virus / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008113:Liver Neoplasms / Q000821:virology; D055571:Secretory Pathway; D014162:Transfection; D056811:Unfolded Protein Response / Q000235:genetics*
chemical_list: D051702:Activating Transcription Factor 6; D006513:Hepatitis B e Antigens