Foot-and-mouth disease virus strains isolated from persistently infected cell cultures are attenuated for mice and cattle.

It was previously reported that during serial passage of a BHK-derived cell line persistently infected with foot-and-mouth disease virus, (termed C1-BHK-Rc1) the virus became increasingly more virulent for BHK-21 cells (de la Torre et al 1988). Virus strains isolated from different cell passage levels were tested for virulence in mice and cattle. The results showed that in the course of persistence in BHK cells, FMDV became progressively less virulent for mice and cattle.