Two subtypes of nucleoproteins (NP) of influenza A viruses

Abstract

The nucleoprotein (NP) genes of nine influenza A virus strains isolated from different species have been sequenced and the deduced amino acid sequences have been compared to published NP sequences and sequences in press. Two "subtypes" of NPs can clearly be defined, one "subtype" comprises the NPs found with all tested human and one porcine strain, and another "subtype" comprises the NPs found with all tested avian and equine, and some porcine strains and a mink virus. There are no significant differences between these two groups concerning secondary structure predictions. Pig viruses were the only ones whose NP can belong to the one or the other "subtype." Therefore, pigs can be regarded as "mixing vessels," where the two independently evolving reservoirs of influenza A viruses can meet for the creation of new pandemic strains by reassortment.