Contribution to the study of the parainfluenza antigens.

From epidemiological data it appeared that an epidemic of parainfluenza type 1 occurred in Lyons in October-November 1967. Thereafter a few sporadic cases were detected. Then in 1970 strains were isolated which showed a change in the hemagglutinin antigen. The persistence of antibodies in the population is shorter than that of the other parainfluenza viruses (i. e. parainfluenza 3); it is not known if reinfections with parainfluenza 1 occur since there are cross-reactions by CF test between parainfluenza 1 and parainfluenza 3 which are known to cause reinfections. The study of antigens of parainfluenza strains was made by HI, Nt, CF and immunodiffusion tests with various antisera prepared in various animal species. This study showed antigenic differences and similarities between parainfluenza 1 and parainfluenza 3.