Nonhomologous recombination between the hemagglutinin gene and the nucleoprotein gene of an influenza virus.

Mutants of the influenza virus A/seal/Mass/1/80 (H7N7) are described which contain an insertion of 60 nucleotides in the hemagglutinin (HA) gene, derived most probably by recombination between the HA gene and the nucleoprotein gene of the same virus. The nonhomologous RNA recombination resulted in an enhanced hemagglutinin cleavability associated with broadening of the host cell spectrum, increased hemolytic activity, and increased pathogenicity for chickens.