STUDIES OF IN-VIVO DISTRIBUTION OF BOVINE HERPESVIRUS TYPE-4 IN THE NATURAL HOST

The in vivo distribution of bovine herpesvirus type 4 (BHV-4) was exam ined by testing nasal and conjunctival exudates, peripheral blood leuk ocytes, and various organs of experimentally infected calves. For viru s detection, a nested PCR assay, virus isolation, and immunohistochemi stry were applied. The nervous system and the muscles were free of vir al DNA. Liver and intestinal lymph nodes contained low amounts of viru s (less than two copies per 1 mu g of cellular DNA). Intestinal, tonsi l, thymus, and kidney tissues contained more viral DNA copies (5 to 50 copies per 1 mu g of cellular DNA). The highest amounts of BHV-4 DNA (50 to 500 copies per 1 mu g of cellular DNA) were found in the spleen , lungs, trachea, and nasal epithelium. Amplification of DNA from bloo d lymphocytes through postinoculation (p.i.) day 48 proved that the vi rus 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 thereaft er. Virus-infected cells were found only in the spleen on p.i. day 48 by immunohistochemistry. Western blotting (immunoblotting) detected si gns of an immune response against 9 of the 29 BHV-4 proteins.