Effects of a pathogenic canine herpesvirus on established thyroid adenocarcinoma cell cultures

The effects of a pathogenic canine herpesvirus were studied sequentially in established canine thyroid adenocarcinoma tissue culture cells. The lesions were defined as early, middle, and late manifestations of viral effects based on the time a lesion first appeared. The early phase (3 to 10 hours) consisted of nucleolar swelling followed by disruption. The nucleolar changes were characterized by loss of RNA as determined with acridine orange and segregation of the nucleolar components as demonstrated by electron microscopy. The middle phase (10 to 34 hours) was characterized by the appearance of three types of eosinophilic intranuclear inclusions. One type of inclusion appeared to transform progressively into another. The appearance of viral antigen in the nucleus as demonstrated by immunofluorescence, correlated with ultrastructural evidence of viral replication. The late phase (34 to 72 hours) was manifested by cellular degeneration and viral release into the cytoplasm.