Elevated Levels of Anti‐CD9 Antibodies in the Cerebrospinal Fluid of Patients with Subacute Sclerosing Panencephalitis

Subacute sclerosing panencephalitis (SSPE) is a slowly progressive and highly lethal disease of the central nervous system. Although the primary cause of SSPE is believed to be persistent infection of neuron and glial cells by a measles virus, the precise mechanism of the progression of this disease has not yet been elucidated. CD9, a member of the tetraspanin family, is expressed in myelin and other nervous tissues. This study detected significant amounts of anti-CD9 antibodies in the cerebrospinal fluid (CSF) of all patients with SSPE included in the study. Anti-CD9 antibodies were also detected in the CSF of some patients with other neurologic disorders, but those patients had lower levels of anti-CD9 antibodies than did the patients with SSPE. The level of anti-CD9 antibodies was elevated and reached a peak that coincided with the appearance of brain atrophy. These findings shed light on a new aspect of the causes and progression of SSPE.