Article Text

PDF
PTU-113 Osteopontin is involved in chronic HBV infection and enhances HBV replication and HBSAG secretion
  1. S Phillips,
  2. J Coombes,
  3. S Mistry,
  4. R Williams,
  5. W Syn,
  6. S Chokshi
  1. Foundation for Liver Research, Institute of Hepatology, London, UK

Abstract

Introduction Hepatitis B virus (HBV) requires host cellular machinery such as cyclophilins to support its ongoing propagation (Phillips et al , Gastroenterology 2014) these host proteins represent ideal candidates for therapeutic interventions as they are generally expected to have a lower frequency of drug-resistance and antiviral efficacy across genotypes. We have also recently described a role for the host protein Osteopontin (OPN), a pro-fibrogenic downstream effector of the Hedgehog pathway, in enhancing HCV replication (Choi et al , Clinical Sciences 2014). Whilst increased levels of blood OPN have similarly been reported in chronic Hepatitis B (CHB), its role in viral replication remains unknown. This study aimed to evaluate the role of OPN in HBV replication, HBsAg secretion and HBV-driven liver injury.

Method Stably (HepG2215), transiently (HUH-7) transfected and infected (HepaRG) cell lines, producing full HBV virions and HBsAg particles were cultured over 72 h in the presence/absence of several concentrations of recombinant OPN (recOPN). In addition, secreted OPN was neutralised using OPN-specific aptamers. Cells and supernatants were harvested at baseline, 24, 48 and 72 h. Intracellular OPN mRNA and HBV-DNA levels were quantitated by Real-Time qPCR. HBsAg levels were measured by ELISA. OPN levels were also measured by ELISA in cell culture supernatants and in sera of controls and HBeAg (+) CHB patients who were either treatment naive or treated with potent antiviral agents. In addition, expression of OPN was assessed in explanted livers from healthy and HBV-cirrhotic patients.

Results Serum levels and intrahepatic expression of OPN were significantly increased in CHB patients compared to controls (up to 7 fold; p < 0.05). In vitro, mRNA and protein levels of OPN were highly correlated with intracellular HBV-DNA (r = 0.858; p < 0.001/r = 0.997; p = 0.003), secreted HBV-DNA (r = 0.968; p < 0.001/r = 0.818; p = 0.047) and secreted HBsAg (r = 0.738; p = 0.001/r = 0.89; p = 0.018). The relationship between OPN and HBV replication was further confirmed following treatment with recOPN which showed a significant increase in intracellular and secreted HBV-DNA by an additional 1.3 Log10 copies/mL and amplified HBsAg secretion rates by 2 fold.

Conclusion These data confirm that OPN is upregulated in the blood and livers of CHB patients. We also show that OPN directly augments HBV replication, thus identifying a novel therapeutic target.

Disclosure of interest None Declared.

Statistics from Altmetric.com

Request permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.