Antigenic and genetic characterization of H1 influenza viruses isolated from feral ducks and swine in Japan.

The strains of H 1 N 4 influenza A virus isolated from feral ducks in Japan in 1977-78 were compared to swine-origin H 1 N 1 viruses antigenically and genetically. Homologous characteristics were found among the H 1 N 4 isolates from feral ducks in hemagglutination-inhibition (HI) tests, viral RNA patterns on polyacrylamide gel electrophoresis and oligonucleotide mapping. Although the hemagglutinins of duck-origin viruses employed in this study were identified as H 1, the viruses were distinguishable from A/New Jersey/8/76 (H 1 N 1), A/duck/Alberta/35/76 (H 1 N 1) and the virus isolated from swine in Japan in the cross HI test. Also, the viral RNA patterns of the duck- and swine-origin H 1 viruses were found to be quite different, indicating that genetic reassortment of HA genes between them is unlikely. After H 1 N 4 virus of duck-origin was intranasally inoculated into pigs, a brief period of virus recovery with no serological response was observed; whereas swine-origin H 1 N 1 virus produced seroconversion in the pigs inoculated.