Concomitant appearance of antibodies to two viruses in cerebrospinal fluid of an infant with acute encephalitis.

Acute encephalitis developed in a 5 1/2-month-old infant with a previous history of uncomplicated measles at 4 months of age. The patient survived his acute illness with resultant severe neurological sequelae. The serum complement fixing antibody titer for herpes simplex virus in the early phase of the illness was less than 1:4, and increased significantly to 1:64 in the convalescent phase. Antibody was also demonstrated in the cerebrospinal fluid. Antimeasles antibody was found in the cerebrospinal fluid in the early convalescent stage and remained at a detectable level for at least 1 month. Moreover, at least 71% of the total protein in the cerebrospinal fluid was IgG. Although brain biopsy for viral isolation was not performed, the most probable diagnosis was herpes simplex virus encephalitis, and the concomitant appearance of measles antibody in the cerebrospinal fluid may have been due to leakage of measles antibody from the blood into the cerebrospinal fluid due to disturbance of the blood-brain barrier.