[Cultivation of cells in a medium with blood hydrolysate].

Use was made of fresh blood of swine, diluted with an equal amount of distilled water to produce a protein hydrolysate. Enzyme hydrolysis was effected through extracellular alkaline protease produced by stain DI of Bacillus subtilis. The cell lines BHK-21, PK-15 and spzv were cultured in a nutrient medium containing 0.

[Cultivation and demonstration of the classic swine fever virus].

Experiments were carried out for the cultivation and indication of the swine pestivirus in several continuous and in primary cell lines, using lapinized and field strains of the virus. It was demonstrated that in the various cell cultures the strains used showed varying rates of growth. In PK-15 and pig embryonic kidney cell lines, the field strains and the virulent Vratsa strain replicated with no preliminary adaptation, forming numerous large fluorescent plaques at the 16th to 18th hour.

[Experiments to produce an attenuated strain of the transmissible gastroenteritis virus and its use as a live vaccine].

Serial passages have been performed of a field virus of the transmissive gastroenteritis to obtain an attenuated strain adapted to a permanent cell line of pig kidney, "SPEV". The strain is innocuous for test animals, for pigs of all ages, and for swine during the entire period of pregnancy. It has proved genetically stable.