Kinetics of virus production in cells doubly infected with the virus of bovine diarrhea and a bovine enterovirus

Abstract

One-step growth curves of a bovine enterovirus and the virus of bovine diarrhea (BVD) in singly and doubly infected bovine embryonic kidney (BEK) and bovine embryonic spleen (BES) cells were determined. In BEK cells, bovine enterovirus infectivity increased exponentially in both tissue culture fluid and cells 4 to 10 hours after inoculation and then levelled off. In BES cells, the exponential increase lasted 14 to 17 hours. In the growth curve of the BVD virus in BEK cells, the extracellular and cell-associated viruses increased exponentially until hour 12, increasing gradually thereafter. In BES cells, BVD virus infectivity increased exponentially 24 hours after infection and then levelled off. The peak infectivity in BES cells was reached 24 hours before that in BEK cells. Growth of bovine enterovirus was studied in cells of BEK and BES monolayers preinfected with the BVD virus for 20 hours. The infectivity titer in preinfected BEK cells was approximately 2 logs less than in preinfected BES cells. A decreased yield in infectivity was observed compared to the bovine enterovirus one-step growth curve.