[Enhanced luminescence intensity in immunofluorescent preparations following trypsin treatment].

Comparative investigations were carried out on the immunofluorescent preparations of cell cultures infected with bovine viruses--rota-, corona-, respiratory-syncytial, parainfluenza-3, adeno-1, and herpes-1--to test various fixatives and the effect of trypsin in raising the sensitivity of the immunofluorescence method. The effect of trypsin was manifested in fixation with formalin, ethanol, methanol, and acetone treated immunofluorescent preparations of cell cultures infected with rota- and adeno-viruses as well as in fixation with acetone of cultures infected with respiratory syncytial virus, parainfluenza-3 virus, and corona virus. Formalin, ethanol, and partly methanol were shown to be unsuitable for the purpose of fixation of cell culture preparations infected with viruses that contained a lipoprotein envelope.

[Attenuated vaccine against rota- and coronavirus enteritis in calves].

Tested was the effect of the Bulgarian attenuated vaccine of rota- and corona-viruses 'PoKo-81', via treatment of dry and freshly calved cows (injected into the udder) and newborn calves (peritoneal injection). It was found that calves fed three times daily on milk obtained from cows that had had intramammary injections did not develop clinical signs of a disease following experimental infection with rota- and corona-viruses. When the cows on infected farms were treated in the same way the disease in calves, offered immune milk, dropped to 36 per cent as against calves of unvaccinated cows, with which morbidity ran as high as 85 per cent.

[Immunofluorescence demonstration of bovine pestivirus].

A high-titer hiperimmune calf serum was obtained via the manifold hyperimmunization with local strains of the bovine pestivirus, cultivated in homologous cell cultures. Its globulin fractions were treated with fluorescein isothiocyanate to produce a specific conjugate. The specificity of the immunofluorescent serum was demonstrated through the comparative study of cell cultures infected with various viruses.