Immunologic Studies of Japanese Encephalitis Virus in Japan

Abstract

Summary The antibody response patterns of 99 patients with proved or presumed JE have been studied. Neutralizing and HI antibodies were found to appear early in the course of disease. Although maximal amounts of neutralizing antibody were generally attained by the first week after onset of symptoms, HI antibody tended to increase through the third post onset week. CF antibody, on the other hand, was not commonly detected in the first two weeks of disease, and was not uniformly demonstrable in all patients. When present, significant increases in CF antibody were commonly demonstrated after the third week of disease. The significance of the dissociation in time of appearance of these antibody types, with particular reference to the practical problems of laboratory diagnosis of JE, is discussed. For routine diagnosis both CF and HI tests should be performed. The former is of greatest value when the initial serum is obtained relatively late after onset of disease. When this initial specimen is obtained within the first week of disease, the HI test provides the most rapid diagnosis. The neutralization test is of little diagnostic value because significant increases in titer are rarely demonstrable, and the test is time-consuming and expensive. The residual neutralizing antibody 5 years after overt infection with JE was found to be the same titer as that observed at the time of infection. CF antibody, although not detectable after 5 years in the majority of individuals, still was present in approximately 25% of persons studied. HI antibody for the most part remained detectable, though the range of titers was lower than that seen immediately after infection.