Subacute sclerosing panencephalitis (SSPE) agent in hamsters.

A hamster-adapted SSPE agent was shown to cause a productive infection in weanling hamster brain, which changed to a cell-associated or defective infection coincident with the appearance of measles antibodies in serum. Antibodies to measles hemagglutinin, hemolysin and neucleocapsid antigens developed in serum, which also contained neutralizing activity for regular measles virus. The agent recovered from the brains prior to the appearance of serum antibodies was infectious in cell-free media, capable of rapidly destroying Vero-cell cultures and able to progressively destroy primary hamster brain cultures. In contrast the agent recovered from the brain after serum antibodies were present, was infectious only within cells destroyed Vero-cells ineffectively and spread slowly through primary brain tissue cultures releasing minute amounts of extracellular virus intermittently. Nevertheless, infected giant cells in the primary brain cultures contained both the HA & HL measles antigens in their cytoplasmic membranes. This in vivo conversion of a productive to a cell-associated cerebral infection appeared to be caused by the host antibody response and may mirror the initial events of human SSPE and possibly other slow or latent measles infections of the CNS.