Antigenic variation among parainfluenza type 1 (Sendai) viruses: analysis of 6/94 virus.

6/94 virus, isolated originally from a multiple sclerosis (MS) patient, was compared antigenically with related parainfluenza type 1 strains. These included two Sendai strains of mouse and two Sendai strains of reported human origin as well as the HA2 strain. By standard hemagglutination inhibition (HI) or hemadsorption neutralization (HAD-N) tests or by the complement-fixation (CF) cross-block titration test for detecting surface antigens, 6/94 virus and the Sendai virus strains were indistinguishable from each other but distinct from the HA2 strain. By the kinetic HI test, however, 6/94 virus could be readily differentiated from the Sendai viruses isolated from mice and more closely resembled those recovered from man.