Cross-reactive and type-specific complement-fixing structures of Oriboca virions

Characteristics of two components of Oriboca virus were studied after they were separated and semipurified by velocity centrifugation. A component of low infectivity and broad cross-reactivity in the complement-fixation (CF) test had a sedimentation coefficient of 6--7S. Infectious Oriboca virions with hemagglutinating (HA) activity had a sedimentation coeffecient of 457S. These virions cross-reacted broadly with Murutucu viral antibody. The cross-reactive, virion-associated component and a type-specific CF fragment were released from virions by disruption with Nonidet P-40. These CF fragments separated by sucrose gradient equilibrium centrifugation had densities of 1.245gm/ml and 1.181 gm/ml, respectively, and were both interpreted to be envelope structures. The type-specific CF antigen appeared to be related to the viral hemagglutinin in that it blocked hemagglutination-inhibiting (HI) antibody, whereas the cross-reactive CF fragment did not.