Homotypic and heterotypic immunity of influenza A viruses induced by recombinants of the cold-adapted master strain A/Ann Arbor/6/60-ca

Abstract

The cold-adapted (ca) influenza A virus A/Ann Arbor/6/60-ca when administered intranasally to mice in two doses 3 weeks apart induces solid immunity to challenge 3 weeks later with heterotypic influenza A wild-type viruses (17). In the present study heterotypic immunity against viruses from different sub-types was shown to be relatively short-lived, having declined significantly 9 weeks after vaccination and being completely absent by 21 weeks. On the other hand, immunity against challenge viruses with surface antigens similar to the ca vaccinating virus or to other H3N2 viruses remained high, even in the absence of detectable serum haem-agglutination-inhibiting antibody. Both short- and long-term immunity induced by ca viruses was unaffected by earlier priming experiences with other wild-type or ca viruses. These results suggest that at least two mechanisms are involved in respiratory immunity to influenza viruses. © 1987 Springer-Verlag.