Virus‐specific antibody‐producing cells in blood and cerebrospinal fluid in acute Japanese encephalitis

During an epidemic of Japanese encephalitis (JE) in northern Thailand, cerebrospinal fluid (CSF) leukocytes and blood leukocytes from 28 patients with suspected JE were tested for spontaneous in vitro synthesis of antibodies to JE virus (JEV). Sixteen patients were subsequently proven to be infected with JEV. Supernatant fluids of three‐day cultures of unstimulated peripheral blood mononuclear leukocytes or unstimulated unfractionated CSF leukocytes were tested for JEV IgM and IgG antibodies with isotype‐specific “antibody capture” radioimmunoassays. Blood‐derived leukocytes from all sixteen JEV‐infected patients and CSF‐derived leukocytes from four JEV‐infected patients synthesized JEV antibodies. Bloodderived and CSF‐derived leukocytes from all 12 patients with central nervous system infections caused by agents other than JEV uniformly failed to synthesize JEV antibodies. Virus‐specific antibody‐producing cells can be detected in the blood and CSF early in the clinical course of acute JE.