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The in vivo distribution of bovine herpesvirus type 4 (BHV-4) was examined by testing nasal and conjunctival exudates, peripheral blood leukocytes, and various organs of experimentally infected calves. For virus detection, a nested PCR assay, virus isolation, and immunohistochemistry were applied. The nervous system and the muscles were free of viral DNA. Liver and intestinal lymph nodes contained low amounts of virus (less than two copies per 1 g of cellular DNA). Intestinal, tonsil, thymus, and kidney tissues contained more viral DNA copies (5 to 50 copies per 1 g of cellular DNA). The highest amounts of BHV-4 DNA (50 to 500 copies per 1 g of cellular DNA) were found in the spleen, lungs, trachea, and nasal epithelium. Amplification of DNA from blood lymphocytes through postinoculation (p.i.) day 48 proved that the virus started to replicate in these cells immediately after inoculation of the calves and that intensive virus growth took place during the 7 to 8 weeks of the infection. The number of virus-infected lymphocytes reached the maximum on p.i. days 22 to 26 and slowly declined thereafter. Virus-infected cells were found only in the spleen on p.i. day 48 by immunohistochemistry. Western blotting (immunoblotting) detected signs of an immune response against 9 of the 29 BHV-4 proteins.

The elevation of the genus Adenovirus to a family named Adenoviridae is described. This family at the present stage contains two genera, mammalian adenoviruses – Mastadenovirus – and avian adenoviruses – Aviadenovirus. The two genera are separated primarily on the basis of differences in immunological properties of the virions.

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