A mechanism of entry for the Arkansas serotype of infectious bronchitis virus.

摘要

Infectious bronchitis (IB) is one of the most contagious respiratory diseases in poultry with many serotypes. Arkansas 99 (Ark 99) serotype strain is highly virulent and has recently become the most isolated from outbreaks in the Southeastern USA compared to other serotypes. Most observations done in the past to determine the parameters required for entry of the virus into susceptible cells have been done in the Massachusetts Beaudette serotype strain. We have chosen to investigate the mechanism of entry of the Ark 99 into susceptible cells. Entry appears to occur by fusion of the virus to the cell membrane. At one-minute post infection the virus is fused to the cell membrane. Attachment of the virus to the cell membrane occurs at 4°C as well as at 37°C and at five minutes post infection there is an accumulation of viral particles within vesicles. These vesicles do not show the characteristics of an endosome. Chelation of metal ions does not appear to have any effect on the viral entry and inhibitors of endocytosis failed to block viral entry. Entry into susceptible cells of the Ark 99-serotype strain seems to be more efficient at a slightly basic pH.; Our second objective was to identify a receptor molecule for Ark 99. We obtained a plasmid that contained a cDNA clone encoding for feline aminopeptidase N (fAPN) under eukaryotic expression and transfected non-permissive baby hamster kidney cells to IBV with this construct. Infected cells transfected with fAPN plasmid became permissive to Ark/IBV. We found that Ark/IBV could fuse with the cell membrane as soon as one minute post infection and that at ten and 30 minutes viral particles could be seen in vesicles within the cytoplasm of the cells. Inhibition of endocytosis did not have an effect in viral entry. Chelation of metal ions (iron and zinc) as well as use of lysomotropic agents did not prevent viral entry.; Feline cell line CCL94 proved to be permissive to the Ark/lBV. When a nonpermissive cell line was transfected with fAPN the cells then became susceptible, indicating that the feline APN molecule has a role in Ark/IBV entry.