Subacute Sclerosing Panencephalitis: In-Vitro Characterization of Viroses Isolated from Brain Cells in Culture

Abstract

Two measleslike viruses, LEC and JAC, isolated from brain cells of two patients with subacute sclerosing panencephalitis (SSPE) were compared with a wild and attenuated strain of measles virus. Tissue cultures exposed to SSPE viruses yielded infectious virus 24 hr later than those exposed to the two measles viruses; moreover, the titers of the SSPE viruses were consistently lower than those of the other two viruses. Viral antigen was detected by immunofluorescence in the cytoplasm of the cells 24 hr after infection with the four viruses. Intranuclear viral antigen appeared earlier in the SSPE-infected cells than in the cells infected with wild measles virus; nuclei of cells infected with the attenuated measles virus did not fluoresce. Nuclear fluorescence was correlated with the presence of intranuclear nucleocapsids. Both strains of measles virus readily infected the brain cells, but the SSPE viruses at an early passage level consistently failed to do so. The block to infection appeared to be related to the failure of the virus to enter the cells. Thus, the SSPE viruses differed from the two strains of measles virus in a number of important respects.