Studies on the development of avian adenoviruses in cell cultures

Thirteen fowl adenovirus (FAV) and two turkey, adenovirus (TAV) strains were divided into two subgroups based on the early changes produced in cell cultures. These groups were similar to those described for human adeno-viruses (HAV). Group 1 comprised FAV-1, FAV-2, FAV-4, FAV-5 (strains 340 and Tipton), and FAV-8 (strains H-6, 58, and TR-59). This group was characterised in early stages by the production of refractile "pearl-like" inclusions. Eventually, a central basophilic inclusion, produced by condensation of background nucleoplasm around these structures, was formed. This was surrounded by a clear halo. Immunofluorescent staining revealed peripheral accumulation of antigen in the nucleus in the area corresponding to the halo. Group 2, similar to HAV-7, comprised FAV-3, FAV-5 (TR-22), FAV-6, FAV-7, FAV-8 (764), TAV-1 and TAV-2. With this group, the first sign of infection was the development of non-refractile, irregular eosinophilic inclusions which increased in number and size to fill the nucleus. The immuno-fluorescence technique demonstrated large circular fluorescent bodies, probably corresponding to the eosinophilic inclusions. Different strains of serotypes 5 and 8 fell into different subgroups. These serotypes have broad antigenicity, not all strains being identical in neutralisation tests. Where this is the case, and classification on a serological basis alone is not clear cut, these studies may help to resolve the problem.