title: Alisporivir inhibition of hepatocyte cyclophilins reduces HBV replication and hepatitis B surface antigen production.
abstract: OBJECTIVE
  Cyclophilins are host factors required for hepatitis C virus replication. Cyclophilin inhibitors such as alisporivir have shown strong anti-hepatitis C virus activity in vitro and in clinical studies. However, little is known about whether hepatocyte cyclophilins are involved in the hepatitis B virus (HBV) life cycle. We investigated the effects of 2 cyclophilin inhibitors (alisporivir and NIM811) on HBV replication and hepatitis B surface antigen (HBsAg) production in cell lines.
  
  
  METHODS
  Liver-derived cell lines producing full-length HBV and HBsAg particles, owing to stable (HepG2215) or transient (HuH-7) transfection, or infected with HBV (HepaRG cells; Invitrogen [Carlsbad, CA]), were incubated with alisporivir or NIM811 alone, or alisporivir in combination with a direct antiviral (telbivudine). The roles of individual cyclophilins in drug response was evaluated by small interfering RNA knockdown of cyclophilin (CYP)A, CYPC, or CYPD in HepG2215 cells, or CYPA knockdown in HuH-7 cells. The kinetics of antiviral activity were assessed based on levels of HBV DNA and HBsAg and Southern blot analysis.
  
  
  RESULTS
  In HepG2215, HuH-7, and HepaRG cells, alisporivir reduced intracellular and secreted HBV DNA, in a dose-dependent manner. Knockdown of CYPA, CYPC, or CYPD (reduced by 80%) significantly reduced levels of HBV DNA and secreted HBsAg. Knockdown of CYPA significantly reduced secretion of HBsAg, leading to accumulation of intracellular HBsAg; the addition of alisporivir greatly reduced levels of HBsAg in these cells. The combination of alisporivir and telbivudine had greater antiviral effects than those of telbivudine or alisporivir alone.
  
  
  CONCLUSIONS
  Alisporivir inhibition of cyclophilins in hepatocyte cell lines reduces replication of HBV DNA and HBsAg production and secretion. These effects are potentiated in combination with direct antiviral agents that target HBV-DNA polymerase.
authors.affiliation: Institute of Hepatology, Foundation for Liver Research, London, United Kingdom.
authors.forename: Sandra
authors.initials: S
authors.lastname: Phillips
authors.affiliation: Institute of Hepatology, Foundation for Liver Research, London, United Kingdom.
authors.forename: Shilpa
authors.initials: S
authors.lastname: Chokshi
authors.affiliation: Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California.
authors.forename: Udayan
authors.initials: U
authors.lastname: Chatterji
authors.affiliation: Institute of Hepatology, Foundation for Liver Research, London, United Kingdom.
authors.forename: Antonio
authors.initials: A
authors.lastname: Riva
authors.affiliation: Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California.
authors.forename: Michael
authors.initials: M
authors.lastname: Bobardt
authors.affiliation: Institute of Hepatology, Foundation for Liver Research, London, United Kingdom.
authors.forename: Roger
authors.initials: R
authors.lastname: Williams
authors.affiliation: Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California.
authors.forename: Philippe
authors.initials: P
authors.lastname: Gallay
authors.affiliation: Novartis Pharma AG, Basel, Switzerland. Electronic address: nikolai.naoumov@novartis.com.
authors.forename: Nikolai V
authors.initials: NV
authors.lastname: Naoumov
mesh_terms: D000998:Antiviral Agents / Q000494:pharmacology*; D021983:Cyclophilins / Q000032:analysis / Q000037:antagonists & inhibitors / Q000502:physiology*; D016572:Cyclosporine / Q000494:pharmacology*; D004279:DNA, Viral / Q000032:analysis; D056945:Hep G2 Cells; D006514:Hepatitis B Surface Antigens / Q000096:biosynthesis*; D006515:Hepatitis B virus / Q000187:drug effects* / Q000502:physiology; D022781:Hepatocytes / Q000502:physiology*; D006801:Humans; D014779:Virus Replication / Q000187:drug effects*
chemical_list: D000998:Antiviral Agents; D004279:DNA, Viral; D006514:Hepatitis B Surface Antigens; D016572:Cyclosporine; D021983:Cyclophilins; C499715:alisporivir
keywords: Cyclophilin Inhibition; Direct-Acting Antiviral Agent; Peptidyl-Prolyl Isomerase; Viral Replication