title: In vitro characterization of the antiviral activity of fucoidan from Cladosiphon okamuranus against Newcastle Disease Virus.
abstract: BACKGROUND
  Newcastle Disease Virus (NDV) causes a serious infectious disease in birds that results in severe losses in the worldwide poultry industry. Despite vaccination, NDV outbreaks have increased the necessity of alternative prevention and control measures. Several recent studies focused on antiviral compounds obtained from natural resources. Many extracts from marine organisms have been isolated and tested for pharmacological purposes, and their antiviral activity has been demonstrated in vitro and in vivo. Fucoidan is a sulfated polysaccharide present in the cell wall matrix of brown algae that has been demonstrated to inhibit certain enveloped viruses with low toxicity. This study evaluated the potential antiviral activity and the mechanism of action of fucoidan from Cladosiphon okamuranus against NDV in the Vero cell line.
  
  
  METHODS
  The cytotoxicity of fucoidan was determined by the MTT assay. To study its antiviral activity, fusion and plaque-forming unit (PFU) inhibition assays were conducted. The mechanism of action was determined by time of addition, fusion inhibition, and penetration assays. The NDV vaccine strain (La Sota) was used in the fusion inhibition assays. PFU and Western blot experiments were performed using a wild-type lentogenic NDV strain.
  
  
  RESULTS
  Fucoidan exhibited antiviral activity against NDV La Sota, with an obtained IS50 >2000. In time of addition studies, we observed viral inhibition in the early stages of infection (0-60 min post-infection). The inhibition of viral penetration experiments with a wild-type NDV strain supported this result, as these experiments demonstrated a 48% decrease in viral infection as well as reduced HN protein expression. Ribavirin, which was used as an antiviral control, exhibited lower antiviral activity than fucoidan and high toxicity at active doses. In the fusion assays, the number of syncytia was significantly reduced (70% inhibition) when fucoidan was added before cleavage of the fusion protein, perhaps indicating a specific interaction between fucoidan and the F0 protein.
  
  
  CONCLUSIONS
  The results of this study suggest that fucoidan from C. okamuranus represents a potential low-toxicity antiviral compound for the poultry industry, and our findings provide a better understanding of the mode of action of sulfated polysaccharides.
authors.affiliation: Laboratorio de Inmunología y Virología, Facultad de Ciencias Biológicas, Universidad Autónoma de Nuevo León, Ciudad Universitaria, C,P, 66450, San Nicolás de los Garza, Nuevo León, México.
authors.forename: Regina
authors.initials: R
authors.lastname: Elizondo-Gonzalez
authors.forename: L Elizabeth
authors.initials: LE
authors.lastname: Cruz-Suarez
authors.forename: Denis
authors.initials: D
authors.lastname: Ricque-Marie
authors.forename: Edgar
authors.initials: E
authors.lastname: Mendoza-Gamboa
authors.forename: Cristina
authors.initials: C
authors.lastname: Rodriguez-Padilla
authors.forename: Laura M
authors.initials: LM
authors.lastname: Trejo-Avila
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology* / Q000633:toxicity; D002522:Chlorocebus aethiops; D015726:Giant Cells / Q000187:drug effects; D009522:Newcastle disease virus / Q000187:drug effects* / Q000254:growth & development; D000459:Phaeophyceae / Q000737:chemistry*; D011134:Polysaccharides / Q000494:pharmacology* / Q000633:toxicity; D014176:Protein Biosynthesis / Q000187:drug effects; D012254:Ribavirin / Q000494:pharmacology / Q000633:toxicity; D014709:Vero Cells; D010948:Viral Plaque Assay; D053586:Virus Internalization / Q000187:drug effects
chemical_list: D000998:Antiviral Agents; D011134:Polysaccharides; D012254:Ribavirin; C007789:fucoidan