Circulating immune complexes in patients with subacute sclerosing panencephalitis.

Levels of immune complexes (ICs) in serum and cerebrospinal fluid (CSF) specimens from subacute sclerosing panencephalitis (SSPE) patients were measured using a solid-phase C1q radioimmunoassay. Single or serial serum specimens were available from 19 patients, while serial CSF specimens were available from two patients. ICs isolated from one CSF specimen by C1q immobilized to Affi-Gel were analyzed for measles virus antigens by binding of measles virus-specific antisera and by polyacrylamide gel electrophoresis followed by Western blotting. Of 78 serum specimens analyzed, 36 (46%) were positive for ICs. When the 8 patients with 3 or more serum specimens were analyzed, 6 had fluctuating levels of ICs. Two of 5 CSF specimens obtained from a patient during acute disease onset were IC-positive, while a second patient exhibited a rapid increase and decrease of IC levels in 14 CSF specimens obtained during an acute disease exacerbation. Composition analysis of ICs isolated from one of the CSF specimens revealed the presence of antigens corresponding in size to measles virus polymerase, nucleoprotein, and possibly, hemagglutinin polypeptides. These results show that SSPE patients frequently have ICs, that IC levels fluctuate in both serum and CSF, and that the ICs are at least partially composed of measles virus antigens.