Experimental panencephalitis induced in suckling mice, by parainfluenza type 1 (6/94) virus, II. Virologic studies.

6/94 virus, a parainfluenza type 1 isolate from multiple sclerosis brain tissue, produced a chronic panencephalitis when inoculated intracerebrally into suckling ICR mice. Immunofluorescent staining revealed 6/94 viral antigen in ependyma, meninges, choroid plexus, and perivascular parenchymal sites from day 3 to 128 days after infection. Hemadsorption-neutralizing antibody was first detected between 20-25 days after infection and remained at high titers for 7 months. Using embryonated chicken eggs, virus was recovered from mouse brains for only 8 days, but could be recovered from brains grown in vitro as explants for 37 days after infection. In cell lines established from explanted brain tissue, immunofluorescence was the most sensitive indicator of virus presence, although infectious virus was not produced. Fusion of these mouse brain cells with human (W138) indicator cells was the most effective means of rescuing 6/94 virus.