title: Generation and characterization of a recombinant Newcastle disease virus expressing the red fluorescent protein for use in co-infection studies.
abstract: BACKGROUND
  Many viruses have evolved multiple strategies to prevent super infection of host cells by more than one virion. This phenomenon, known as super infection exclusion, may play an important role on virus evolution because it can affect the frequency of reassortment and/or recombination. Newcastle disease virus (NDV), a negative sense single-stranded RNA virus, is characterized by its continuous evolutionary dynamics and by a low frequency of recombination events. However, the mechanisms that contribute to the low recombination rates on NDV are still not completely understood.
  
  
  METHODS
  In this study we assessed the ability of two NDV strains (LaSota and B1) to super infect host cells in vitro. We generated a recombinant NDV strain LaSota expressing the red fluorescent protein (RFP) and used it in co-infection assays with a related NDV strain B1 expressing the green fluorescent protein (GFP). DF-1 cells were inoculated with both viruses at the same time or at different intervals between primary infection and super infection.
  
  
  RESULTS
  When both viruses were inoculated at the same time point, a 27% co-infection rate was observed, whereas when they were inoculated at different time points the super infection rates decreased to levels as low as 1.4%.
  
  
  CONCLUSIONS
  These results indicate that although different NDV strains can co-infect host cells in vitro, the super infection rates are low, specially as the time between the primary infection and super infection increases. These results confirm the occurrence of super infection exclusion between different strains of NDV.
authors.affiliation: USDA-ARS, Southeast Poultry Research Laboratory, 934 College Station Road, Athens, GA 30605, USA.
authors.forename: Jinnan
authors.initials: J
authors.lastname: Li
authors.forename: Haixia
authors.initials: H
authors.lastname: Hu
authors.forename: Qingzhong
authors.initials: Q
authors.lastname: Yu
authors.forename: Diego G
authors.initials: DG
authors.lastname: Diel
authors.forename: De-shan
authors.initials: DS
authors.lastname: Li
authors.forename: Patti J
authors.initials: PJ
authors.lastname: Miller
mesh_terms: D000818:Animals; D002460:Cell Line; D060085:Coinfection; D003588:Cytopathogenic Effect, Viral; D015870:Gene Expression; D006801:Humans; D007700:Kinetics; D008164:Luminescent Proteins / Q000235:genetics*; D009522:Newcastle disease virus / Q000235:genetics* / Q000502:physiology; D015163:Superinfection; D014779:Virus Replication; D000097573:Red Fluorescent Protein
chemical_list: D008164:Luminescent Proteins; D000097573:Red Fluorescent Protein