Precipitating antibodies to non-treated dengue type 2 viral antigens in sera of Thai hemorrhagic fever patients by crossed immunoelectrophoresis.

Crossed immunoelectrophoresis of dengue type 2 virus revealed at least two precipitating antigens which shared some antigenic determinants. Glycoprotein components of both antigens were detected by binding to concanavalin A. Sera from dengue hemorrhagic fever patients showed precipitating antibodies to both antigens which could be quantitated according to the precipitate patterns formed in the intermediate gel of crossed immunoelectrophoresis. All secondary dengue hemorrhagic fever patients demonstrated an increase in precipitin titers in convalescence sera. Most patients with mild illness contained precipitating antibodies in acute phase sera whereas severe cases did not. Convalescent sera from severe cases showed only low titers. These precipitating antibodies may be associated with protection since they were produced early only in those with mild form of illness.