Demonstration of immunoglobulin in brains of ferrets inoculated with an SSPE strain of measles virus: use of protein A conjugated to horseradish peroxidase.

Measles virus-specific immunoglobulin G (IgG) has been found in the brains of patients with subacute sclerosing panencephalitis (SSPE), a slowly progressing central nervous system (CNS) disease affecting children. IgG/albumin ratios indicate that the antibodies are probably synthesized in the CNS. In a ferret model system, protein A conjugated to horseradish peroxidase (PrAPx) was used to localize Ig's in brains of animals inoculated with a cell associated strain of SSPE. Ig's were found in plasma cells in various stages of antibody production both in perivascular inflammatory lesions and scattered throughout the cerebral cortex. These findings offer corroborative evidence that the Ig found in SSPE ferret brain and CSF is actively synthesized within the CNS. Antibody was also demonstrated in glial and neuronal cell bodies and processes and in postsynaptic profiles. These are the same sites where measles virus antigens are most frequently found and suggests the possibility of immune complex formation.