title: Inhibition of hepatitis B virus replication in cultured cells and in vivo using 2'-O-guanidinopropyl modified siRNAs.
abstract: Silencing hepatitis B virus (HBV) gene expression with exogenous activators of the RNA interference (RNAi) pathway has shown promise as a new mode of treating infection with the virus. However, optimizing efficacy, specificity, pharmacokinetics and stability of RNAi activators remains a priority before clinical application of this promising therapeutic approach is realised. Chemical modification of synthetic short interfering RNAs (siRNAs) provides the means to address these goals. This study aimed to assess the benefits of incorporating nucleotides with 2'-O-guanidinopropyl (GP) modifications into siRNAs that target HBV. Single GP residues were incorporated at nucleotide positions from 2 to 21 of the antisense strand of a previously characterised effective antiHBV siRNA. When tested in cultured cells, siRNAs with GP moieties at selected positions improved silencing efficacy. Stability of chemically modified siRNAs in 80% serum was moderately improved and better silencing effects were observed without evidence for toxicity or induction of an interferon response. Moreover, partially complementary target sequences were less susceptible to silencing by siRNAs with GP residues located in the seed region. Hydrodynamic co-injection of siRNAs with a replication-competent HBV plasmid resulted in highly effective knock down of markers of viral replication in mice. Evidence for improved efficacy, reduced off target effects and good silencing in vivo indicate that GP-modifications of siRNAs may be used to enhance their therapeutic utility.
authors.affiliation: Antiviral Gene Therapy Research Unit and African Network for Drugs and Diagnostics Innovation (ANDI) Centre of Excellence, School of Pathology, Health Sciences Faculty, University of the Witwatersrand, Private Bag 3, Wits, 2050 Johannesburg, South Africa.
authors.forename: Musa D
authors.initials: MD
authors.lastname: Marimani
authors.forename: Abdullah
authors.initials: A
authors.lastname: Ely
authors.forename: Maximilian C R
authors.initials: MC
authors.lastname: Buff
authors.forename: Stefan
authors.initials: S
authors.lastname: Bernhardt
authors.forename: Joachim W
authors.initials: JW
authors.lastname: Engels
authors.forename: Patrick
authors.initials: P
authors.lastname: Arbuthnot
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D006146:Guanidines / Q000737:chemistry / Q000494:pharmacology*; D006515:Hepatitis B virus / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D006801:Humans; D051379:Mice; D009943:Organophosphorus Compounds / Q000737:chemistry / Q000494:pharmacology; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology*; D014162:Transfection; D014779:Virus Replication / Q000187:drug effects* / Q000235:genetics
chemical_list: D006146:Guanidines; D009943:Organophosphorus Compounds; D034741:RNA, Small Interfering; C434331:phosphoramidite
keywords: 2′-O-Guanidinopropyl; HBV; RNAi; siRNAs