Elevated parainfluenza virus type 1 antibody in patients with subacute sclerosing panencephalitis.

Parainfluenza virus hemagglutination inhibition (HI) antibodies were determined 3 times in the sera of 9 patients with subacute sclerosiing panencephalitis (SSPE) and 20 healthy controls matched for age and place of residence. Serum antibody against parainfluenza virus type 1 was significantly elevated in SSPE patients as compared with controls, whereas antibodies against type 2 and 3 were found to be in normal ranges. Higher titres of parainfluenza virus type 1 antibody might depend on: (1) dual viral infection, (2) cross-reaction between antigens of SSPE virus and parainfluenza virus type 1, and (3) non-specific activation of latent virus type 1 genome. The latter explanation seems to be particularly interesting since the parainfluenza type 1 antibody titres remained constant despite the clinical progression. This finding is comparable to the elevated titres against Epstein-Barr virus of adenovirus which have been found occasionally in this disease.