Soluble Antigen of Measles Virus

Summary Three complement-fixing (CF) antigens of measles virus, separated on the basis of buoyant density, were further analyzed with respect to sedimentation characteristics and antibody response. The heavy (H) noninfectious CF fraction (density 1.30 g/ml) could be distinguished from the less dense infectious CF antigens (M peak to meniscus, 1.24 to U1.18 g/ml). The H-CF fraction was shown to remain in the supernatant fluid after centrifugation at 20,000 to 30,000 rpm. This fraction is therefore of small particle size and has a density compatible with the nucleoprotein internal component. Antibody response to H-CF fraction occurred following measles viral replication and not after immunization with inactivated vaccine. The H-CF fraction has characteristics resembling those of the soluble antigens of other myxoviruses.