Relationship between viral neurotropism and oncolysis.I. Study of vaccinia virus

Several strains of vaccinia virus were examined in a study of the relationship of viral oncolysis to viral neurotropism. Various animal hosts were challenged intracerebrally with the L strain of vaccinia virus but the virus multiplied only in the brain of one-day-old mice. After 238 passages in mouse brain the virus finally acquired the ability to multiply in the Ehrlich ascites tumor of the mouse and to cause oncolysis. The NEL and LEV vaccinia virus strains initially showed a moderate degree of neurotropism but did not become oncolytic until they were fully adapted to nervous tissue. These results support the concept of a distinct correlation between viral neurotropism and oncolysis and suggest an undetermined similarity between neoplastic and nervous tissues. The findings are significant in considering the application of viruses to human cancers.