Characteristics of a swine recombinant influenza virus isolated in 1980: recombination between swine and the earliest Hong Kong (H3N2) viruses.

A recombinant (H1N2, formerly Hsw1N2), A/swine/Ehime/1/80 was found to possess antigenic biological and genomic characteristics different from those of a previous A/swine/Kanagawa/2/78 (H1N2) strain. Five monoclonal antibodies to A/NJ/8/76 differentiated the haemagglutinin molecules of the former virus from the latter, showing that these viruses differed at two-antigenic determinants at least. Immuno-double diffusion tests with antisera to the isolated neuraminidase and neuraminidase-inhibition tests with monoclonal antibodies to different H2N2 and H3N2 viruses revealed that A/swine/Ehime/1/80 strain contained a neuraminidase subunit very similar to that of late human Asian (H2N2) and the earliest Hong Kong (H3N2) viruses. RNA analysis by oligonucleotide mapping suggested that A/swine/Ehime/1/80 may be a recombinant between A/swine/Shizuoka/1/78-like and A/Aichi/2/68 (H3N2)-like viruses. To determine further the gene constellation of this recombinant virus, DNA-RNA hybridizations were performed using DNA segments complementary for swine (H1N1) virus RNA and the entire RNA of three viruses. The molecular hybridization could define the genomic composition of the recombinant, indicating that only the neuraminidase gene of this virus is derived from the earliest Hong Kong (H3N2)-like virus and remaining seven genes are derived from swine (H1N1) virus.