Ultrastructural study of turkey rhinotracheitis virus infection in turbinates of experimentally infected chickens.

Ultrastructural changes associated with turkey rhinotracheitis virus infection were studied in turbinates of chickens experimentally infected with the isolate CVL 14/86/1. Chickens were sacrificed at 3, 5 and 7 days after inoculation and samples of the middle turbinate were taken, fixed, dehydrated and embedded in an hydrophilic resin. An immunofluorescence technique on semithin sections was carried out and viral antigen was observed in the cytoplasm and associated to cilia of the turbinate epithelial cells, on days 3 and 5 after inoculation. Ultrastructurally, gold stained intracytoplasmic nucleocapsid aggregates of turkey rhinotracheitis virus were observed in ciliated and non-ciliated epithelial cells, as well as budding virus particles, at days 3 and 5 postinoculation. Different ultrastructural abnormalities, including cytoplasmic blebs, clumping and loss of cilia were observed in the apical cell membrane of many infected cells, associated with the presence of intracytoplasmic inclusions. On day 5 after inoculation, substitution of ciliated and non-ciliated epithelial cells was noted and many desquamated epithelial cells were observed within the lumina. Regenerative changes in the ciliated epithelium were observed by day 7 postinoculation. These results indicate that turkey rhinotracheitis virus is able to replicate in ciliated and non-ciliated epithelial cells causing severe alterations to the cell surface and ciliary apparatus of the turbinate epithelium. Viral-induced damage to the turbinate epithelium could enhance the susceptibility of epithelial cells to secondary bacterial infection.