Experimental Subacute Sclerosing Panencephalitis in the Hamster: Correlation of Age with Chronic Inclusion-Cell Encephalitis

Abstract

A hamster-adapted viral agent of subacute sclerosing panencephalitis was inoculated intracerebrally into weanling and adult hamsters. Acute encephalitis was followed by chronic neurologic disease in some weanling animals. Infectious, cell-free virus was obtained from brains of weanling hamsters during the first eight days of infection; however, defective or cell-associated virus was demonstrated by cocultivation techniques for as long as 81 days after inoculation. Immunofluorescent studies showed specific measles antigen in focal areas of brain up to 55 days after inoculation. In brains collected from animals between the 21st and 120th days after inoculation, focal lesions containing perivascular inflammatory cells, plasma cells, increased astrocytes, and cells bearing eosinophilic nuclear inclusions were noted. The HAl-antibody response to measles virus, although variable, was often markedly elevated in the sera of animals with histologic lesions characteristic of chronic infection. Adult hamsters did not develop clinical disease; however, virus was recoverable through the 12th day after inoculation. Acute inflammatory reactions with eosinophilic intranuclear inclusions developed early but disappeared by the 21st day after inoculation. The HAl-antibody response to measles virus in the sera of adult animals was moderate and decreased after the 30th day.