Growth of Rio Bravo Virus in Cell Cultures

The growth of Rio Bravo virus (RBV) in eight cell culture systems was studied. Highest yields of virus were produced in BHK-21 (C13), L, and Vero cell lines, but L cells were resistant to low doses of virus. LLC-MK2, HeLa, and human embryo skin cells produced moderate amounts of virus, but FL amnion and primary chick embryo fibroblasts supported little virus growth. Virus was rapidly inactivated by exposure to pH values below 7.0. Single-cycle growth in BHK-21, L, and LLC-MK2 cell monolayers was characterized by a latent period of about 12 hours followed by rapid virus production that peaked at 36 to 48 hours. Vero cell cultures can remain chronically infected with RBV for more than 100 days. They show evidence of cell destruction and their supernatant fluids contain virus at 10 to the 4th power to 10 to the 5th power log 10 per ml.