Purification of a Soluble Gel Precipitating Antigen of Rubella Virus and Antibody Responses to the Purified Antigen

Abstract

A gel‐precipitating (GP) antigen was purified from rubella‐infected BHK‐21 cells. The purification procedure included DEAE‐cellulose chromatography and ultracentrifugations. The purified antigen also had CF antigen activity which represented about 10 per cent of the original amount of CF antigen in infected BHK‐cells. This GP antigen sedimented at about 3.5 S in sucrose gradient centrifugations and equilibrated at about 1.30 g/ml in CsCl gradient centrifugations. Immunization of guinea pigs with this antigen resulted in the production of rubella GP antibodies as well as HI and CF antibodies to purified rubella virus. The gel precipitating antibody response was measured with this purified antigen. After natural rubella infection a slow increase in GP titres was found until the end of the observation period which covered 3 to 4 months. A tendency to slow development of rubella GP antibodies was observed in rubella vaccinees. Animal immunizations confirmed the slow increase of GP antibodies. Rabbits responded better than guinea pigs when measured by GP, although the latter produced high rubella HI antibody titres.