Virological Aspects of Measles Virus-induced Encephalomyelitis in Lewis and BN Rats

Lewis and Brown Norway (BN) rats which are susceptible or resistant to autoimmune reactions against brain antigen, respectively, were inoculated intracerebrally with a neurotropic measles virus. Suckling rats died from a rapidly fatal acute encephalopathy (AE). With increasing age Lewis rats developed a subacute measles encephalomyelitis (SAME) whereas BN rats showed a clinically silent encephalitis (CSE). Infectious virus could occasionally be recovered from SAME animals using cocultivation techniques but not from BN rats with CSE. With monoclonal antibodies against measles virus, viral proteins were localized in brain tissue. Nucleocapsid and phosphoprotein were detected in infected brain cells of all animals with AE, SAME and CSE, whereas measles virus haemagglutinin, fusion and matrix proteins were either reduced or absent, suggesting a restricted synthesis of measles virus envelope proteins. These data suggest that the different diseases of the two rat strains are related to the immunogenetic background rather than to the replication of measles virus in the central nervous system. This animal model provides the opportunity to investigate further the events occurring during establishment of measles virus persistence in the brain, and the genetic control of associated immunological and immunopathological reactions.