title: 5' Triphosphorylated small interfering RNAs control replication of hepatitis B virus and induce an interferon response in human liver cells and mice.
abstract: OBJECTIVE
  Approved therapies for chronic hepatitis B include systemic administration of interferon (IFN)-alfa and inhibitors of hepatitis B virus (HBV) reverse-transcription. Systemic application of IFN-alfa is limited by side effects. Reverse-transcriptase inhibitors effectively control HBV replication, but rarely eliminate the virus and can select drug-resistant variants. We aimed to develop an alternative therapeutic approach that combines gene silencing with induction of IFN in the liver.
  
  
  METHODS
  To stimulate an immune response while inhibiting HBV activity, we designed 3 small interfering (si)RNAs that target highly conserved sequences and multiple HBV transcripts of all genotypes. A 5'-triphosphate (3p) was added to the siRNAs, turning them into a ligand for the cytosolic helicase retinoic acid-inducible protein I, which becomes activated and induces expression of type-I IFNs. Antiviral activity was investigated in cell lines that replicate HBV, in HBV-infected primary human hepatocytes, and in HBV transgenic mice.
  
  
  RESULTS
  3p-double-stranded RNA (3p-RNA) activated retinoic acid-inducible protein I, induced a strong type I IFN response (expression of IFN-β) in liver cells and showed transient but strong antiviral activity. Bifunctional, HBV-specific, 3p-siRNAs controlled replication of HBV more efficiently and for longer periods of time than 3p-RNAs without silencing capacity or siRNAs that targeted identical sequences but did not contain 3p.
  
  
  CONCLUSIONS
  HBV-specific 3p-siRNAs are bifunctional antiviral molecules that induce production of type I IFNs in the liver and target HBV RNAs to inhibit viral replication.
authors.affiliation: Institute of Virology, Technische Universität München/Helmholtz Zentrum München, Munich, Germany.
authors.forename: Gregor
authors.initials: G
authors.lastname: Ebert
authors.forename: Hendrik
authors.initials: H
authors.lastname: Poeck
authors.forename: Julie
authors.initials: J
authors.lastname: Lucifora
authors.forename: Nikola
authors.initials: N
authors.lastname: Baschuk
authors.forename: Knud
authors.initials: K
authors.lastname: Esser
authors.forename: Irene
authors.initials: I
authors.lastname: Esposito
authors.forename: Gunther
authors.initials: G
authors.lastname: Hartmann
authors.forename: Ulrike
authors.initials: U
authors.lastname: Protzer
mesh_terms: D015088:2',5'-Oligoadenylate Synthetase / Q000378:metabolism; D000818:Animals; D056945:Hep G2 Cells; D006509:Hepatitis B / Q000378:metabolism / Q000473:pathology / Q000821:virology*; D006515:Hepatitis B virus / Q000187:drug effects* / Q000235:genetics* / Q000502:physiology; D006801:Humans; D007370:Interferon Type I / Q000378:metabolism; D016898:Interferon-alpha / Q000378:metabolism; D016899:Interferon-beta / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D010766:Phosphorylation / Q000235:genetics; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000737:chemistry / Q000235:genetics* / Q000494:pharmacology*; D011994:Recombinant Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D019562:Viral Load / Q000187:drug effects; D014779:Virus Replication / Q000187:drug effects* / Q000235:genetics / Q000502:physiology
chemical_list: D007370:Interferon Type I; D016898:Interferon-alpha; C431552:RAI1 protein, human; D034741:RNA, Small Interfering; C502844:Rai1 protein, mouse; D011994:Recombinant Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D016899:Interferon-beta; D015088:2',5'-Oligoadenylate Synthetase