title: Inhibition of severe acute respiratory syndrome coronavirus replication in a lethal SARS-CoV BALB/c mouse model by stinging nettle lectin, Urtica dioica agglutinin.
abstract: Urtica dioica agglutinin (UDA) is a small plant monomeric lectin, 8.7 kDa in size, with an N-acetylglucosamine specificity that inhibits viruses from Nidovirales in vitro. In the current study, we first examined the efficacy of UDA on the replication of different SARS-CoV strains in Vero 76 cells. UDA inhibited virus replication in a dose-dependent manner and reduced virus yields of the Urbani strain by 90% at 1.1 ± 0.4 μg/ml in Vero 76 cells. Then, UDA was tested for efficacy in a lethal SARS-CoV-infected BALB/c mouse model. BALB/c mice were infected with two LD50 (575 PFU) of virus for 4 h before the mice were treated intraperitoneally with UDA at 20, 10, 5 or 0 mg/kg/day for 4 days. Treatment with UDA at 5 mg/kg significantly protected the mice against a lethal infection with mouse-adapted SARS-CoV (p < 0.001), but did not significantly reduce virus lung titers. All virus-infected mice receiving UDA treatments were also significantly protected against weight loss (p < 0.001). UDA also effectively reduced lung pathology scores. At day 6 after virus exposure, all groups of mice receiving UDA had much lower lung weights than did the placebo-treated mice. Thus, our data suggest that UDA treatment of SARS infection in mice leads to a substantial therapeutic effect that protects mice against death and weight loss. Furthermore, the mode of action of UDA in vitro was further investigated using live SARS-CoV Urbani strain virus and retroviral particles pseudotyped with SARS-CoV spike (S). UDA specifically inhibited the replication of live SARS-CoV or SARS-CoV pseudotyped virus when added just before, but not after, adsorption. These data suggested that UDA likely inhibits SARS-CoV infection by targeting early stages of the replication cycle, namely, adsorption or penetration. In addition, we demonstrated that UDA neutralizes the virus infectivity, presumably by binding to the SARS-CoV spike (S) glycoprotein. Finally, the target molecule for the inhibition of virus replication was partially characterized. When UDA was exposed to N-acetylglucosamine and then UDA was added to cells just prior to adsorption, UDA did not inhibit the virus infection. These data support the conclusion that UDA might bind to N-acetylglucosamine-like residues present on the glycosylated envelope glycoproteins, thereby preventing virus attachment to cells.
authors.affiliation: Institute for Antiviral Research, Department of Animal, Dairy and Veterinary Science, 5600 Old Main Hill, Utah State University, Logan, UT 84322, USA.
authors.forename: Yohichi
authors.initials: Y
authors.lastname: Kumaki
authors.forename: Miles K
authors.initials: MK
authors.lastname: Wandersee
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Smith
authors.forename: Yanchen
authors.initials: Y
authors.lastname: Zhou
authors.forename: Graham
authors.initials: G
authors.lastname: Simmons
authors.forename: Nathan M
authors.initials: NM
authors.lastname: Nelson
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Bailey
authors.forename: Zachary G
authors.initials: ZG
authors.lastname: Vest
authors.forename: Joseph K-K
authors.initials: JK
authors.lastname: Li
authors.forename: Paul Kay-Sheung
authors.initials: PK
authors.lastname: Chan
authors.forename: Donald F
authors.initials: DF
authors.lastname: Smee
authors.forename: Dale L
authors.initials: DL
authors.lastname: Barnard
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000008:administration & dosage*; D001835:Body Weight; D002522:Chlorocebus aethiops; D004195:Disease Models, Animal; D005260:Female; D007273:Injections, Intramuscular; D051379:Mice; D008807:Mice, Inbred BALB C; D037121:Plant Lectins / Q000008:administration & dosage*; D012376:Rodent Diseases / Q000188:drug therapy / Q000401:mortality / Q000473:pathology / Q000821:virology; D045473:Severe acute respiratory syndrome-related coronavirus / Q000187:drug effects*; D045169:Severe Acute Respiratory Syndrome / Q000188:drug therapy* / Q000401:mortality / Q000473:pathology / Q000821:virology; D016019:Survival Analysis; D014709:Vero Cells; D014779:Virus Replication / Q000187:drug effects
chemical_list: D000998:Antiviral Agents; D037121:Plant Lectins; C048862:stinging nettle lectin