title: Inhibition of enterovirus 71 replication and the viral 3D polymerase by aurintricarboxylic acid.
abstract: OBJECTIVE
  Enterovirus 71 (EV71) causes serious diseases in humans. The aim of this study was to examine the effects of aurintricarboxylic acid (ATA) on EV71 replication and to explore the underlying mechanism.
  
  
  METHODS
  To measure the activity of ATA in inhibiting the cytopathic effect (CPE) of EV71, a cell-based neutralization (inhibition of virus-induced CPE) assay was performed. The effect of ATA was further confirmed using plaque reduction and viral yield reduction assays. A time of addition assay was performed to identify the mechanisms of ATA's anti-EV71 activity. We examined the effects of ATA on the following key steps involved in virus replication: (i) translation of the internal ribosomal entry site (IRES)-mediated viral polyprotein; (ii) the proteolytic activity of viral proteases 2A and/or 3C; and (iii) the viral 3D RNA-dependent RNA polymerase (RdRp) activity.
  
  
  RESULTS
  In this study, ATA was found to be a potent inhibitor of the replication of EV71. In the antiviral neutralization assay, ATA exhibited inhibitory activity against EV71 (TW/4643/98) and EV71 (TW/2231/98). Plaque assay further demonstrated that ATA inhibited EV71 replication with an EC(50) (effective concentration at which 50% of plaques were removed) of 2.9 microM. Studies on the mechanism of action revealed that ATA targets the early stage of the viral life cycle after viral entry. ATA was able to inhibit the RdRp activity of EV71, while neither the IRES-mediated translation of viral polyprotein nor the viral 3C protease activity was affected.
  
  
  CONCLUSIONS
  Overall, the findings in this study suggest that ATA is able to effectively inhibit EV71 replication through interfering with the viral 3D polymerase.
authors.affiliation: Department of Biological Science and Technology, National Chiao Tung University, Hsin-Chu, Taiwan.
authors.forename: Hui-Chen
authors.initials: HC
authors.lastname: Hung
authors.forename: Tzu-Chun
authors.initials: TC
authors.lastname: Chen
authors.forename: Ming-Yu
authors.initials: MY
authors.lastname: Fang
authors.forename: Kuei-Jung
authors.initials: KJ
authors.lastname: Yen
authors.forename: Shin-Ru
authors.initials: SR
authors.lastname: Shih
authors.forename: John T-A
authors.initials: JT
authors.lastname: Hsu
authors.forename: Ching-Ping
authors.initials: CP
authors.lastname: Tseng
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D001312:Aurintricarboxylic Acid / Q000494:pharmacology*; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D003588:Cytopathogenic Effect, Viral; D029821:Enterovirus A, Human / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D012324:RNA-Dependent RNA Polymerase / Q000037:antagonists & inhibitors*; D014709:Vero Cells; D010948:Viral Plaque Assay; D014764:Viral Proteins / Q000037:antagonists & inhibitors*; D014779:Virus Replication / Q000187:drug effects*
chemical_list: D000998:Antiviral Agents; D004791:Enzyme Inhibitors; D014764:Viral Proteins; D001312:Aurintricarboxylic Acid; D012324:RNA-Dependent RNA Polymerase