Persistent in vitro interaction of virulent and attenuated canine distemper virus with bovine cells.

Bovine macrophage and non-macrophage cultures were infected with either virulent or attenuated canine distemper virus (CDV). Macrophages were resistant to virulent CDV; however, they supported growth of the attenuated virus. Non-macrophage cultures supported growth of both virus variants in a persistent, non-lytic manner. Major differences between these two systems of in vitro viral persistence were seen in the host cell spectrum of progeny virus and the outcome of cocultivation experiments with Vero cells. Results obtained indicate that in vivo virulence of CDV is not linked to maturation in a macrophage, but rather, propagation in a given cell culture system results in selective growth of virulent or attenuated viral mutants. It is further concluded that in vivo virulence and in vitro growth potential of CDV are disparate properties of the virion.