[Immunofluorescent studies with IBR/IPV virus on cell culture]

The anti IBR/IPV virus (FITC labelled) conjugate was prepared from the bull's hyperimmune serum according to the method applied in CVL Weybridge for preparation of anti-Swine-Fever Conjugate (anti genital strain of virus). The conjugate was titrated using Calf Kidney primary monolayers grown on coverslips in Leighton tubes and inoculated with "Oxford" and "Carmarthen" strains of IBR/IPV virus. The conjugate was active for the first strain in dil. 1:16 and for the second in dil. 1:8. The specificity of reagent was checked both with strains of IBR/IPV viruses and other Herpesviruses: Aujesky Disease and Bovine Mammalitis and heterological conjugates (TGE, HCV). The morphological changes of infected cells and development of specific fluorescence were studied against the increase of extracellular viral titres. The time of appearance of specific fluorescence following inoculation of cells with a low, specially selected virus cell multiplicity ratio = 0.22 was 12-16 hours p.i. which corresponded to viral liter of fluid 1.0 [- log TCID50/-0.1 ml]. The visible CPE occurred at 32-36 hours after infection. The possibility of application of the above-mentioned conjugate to immunofluorescent studies with cells infected by IBR/IPV virus was confirmed.