Hydrocephalus produced by the 6/94 virus; A parainfluenza type 1 isolate from multiple sclerosis brain tissue.

The 6/94 virus, parainfluenza type 1 isolate from multiple sclerosis brain tissue, produced hydrocephalus in newborn Syrian hamsters. All animals developed clinical disease and died within a week. Ependymal cells lining the aqueduct of Sylvius became necrotic and fused, resulting in obstructive hydrocephalus. The 6/94 virus antigen was seen in ependyma and meninges. Paramyxovirus nucleocapsids were seen within cytoplasm of ependymal cells. Virus was recovered from hamster brains for only two days. Infectious virus could be recovered from brains grown in vitro as explants for 21 days. No evidence of rising hemagglutination-inhibiting antibody was noted for up to one month after infection. Intraperitoneal or subcutaneous injection of 6/94 virus did not produce hydrocephalus. HA2 virus and the temperature sensitive mutant of HA2 virus failed to produce hydrocephalus, while Sendai virus caused lesions similar to those of 6/94 virus.