A technique to obviate the risk of inadvertent infection of cell cultures with bovine viral diarrhoea virus.

When bovine embryonic kidneys collected at the Gorgie Abattoir, Edinburgh were examined for evidence of infection with bovine viral diarrhoea virus (BVDV), 11 out of 26 kidneys were found to be positive. A technique that detected the presence of inadvertent BVDV in cell cultures consisted of processing and digesting the kidneys to produce cell suspensions, adding dimethyl sulphoxide and dispersing the suspensions in small aliquots that were stored frozen at - 114 degrees C. One aliquot was cultured and screened for BVDV by indirect immuno-fluorescence and interference tests. Bovine embryonic kidney cells so processed retained their viability and virus susceptibility for 15 to 18 months. Selected stocks of "clean" cells only are then used for vaccine production or diagnostic purposes. The cytopathic NADL strain of BVDV multiplied in naturally infected cell cultures but the titres attained were significantly lower than in "clean" cell cultures.