Serologic Comparisons with Lines of Influenza Virus Isolated and Serially Transferred in Different Experimental Hosts

Summary Lines of virus derived from a single throat washing by isolation and transfers in different hosts were compared in cross tests with antisera from several species. Variations in antigenic potency and avidity for antibody were noted especially with viruses after passages in mice or in chorioallantoic membrane tissue culture.</jats:p

Serologic Evidence of American Experience with Newborn Pneumonitis Virus (Type Sendai)

Summary The host range and growth characteristics of the Newborn Pneumonitis Virus (Type Sendai) have been studied. The hemagglutinin and serologic character have been examined and evidence is presented which supports the contention of the Japanese investigators that this is a hitherto undescribed virus. Evidence has also been found that an antigenic stimulus exists in the American population which gives rise to antibodies which react with the Sendai agent. This antigenic entity is widespread geographically and has been present at least since 1936. At the present, antibodies occur with high frequency (40 per cent) and the highest levels are present in the age group under 18 years. Isolation of the agent in our population has not been successful and only in a few instances could a serologic diagnosis be made of infection. The possible relation of the agent to the influenza group of viruses has been considered.</jats:p

Pilot Studies on Recombinant Cold-Adapted Live Type A and B Influenza Virus Vaccines

Recombinant live attenuated type A and B influenza virus vaccines derived from standardized cold-adapted parent strains were given singly and in combination to vol-unteers. The vaccine viruses were well tolerated, functioned as good antigens, and failed to spread to intimate household contacts. Thirty-nine isolates that were re-covered after a single passage in humans appeared genetically stable. The results of histopathologic studies in ferrets encourage development of an animal model for attenuation of the virus. Well-tolerated and highly immunogenic live in-fluenza virus vaccines have been produced with lines of cold-adapted virus derived by gradual or abrupt lowering of incubation temperatures to 25 C [1-7]. Under optimal conditions, use of a recombination technique permitted shortening of the time required for obtaining seed virus suit-able for production of vaccine to six weeks [8]