Conservation of amino acid positions in NP that are responsible for MxA resistance.

Full-length NP protein sequences of the indicated subtype and host were downloaded at 19th of October 2012 from [24]. Sequences depicted as H1N1 seasonal exclude H1N1 viruses of the pH1N1 lineage. Human pH1N1 refer to sequences of isolates found in humans. In avian sequences all available subtypes (H1-16, N1-9) were included. Sequences depicted as swine classical comprise sequences of the North American classical swine influenza viruses and exclude viruses of the pH1N1 lineage. The frequency of conserved residues is indicated in %. n = number of strains analyzed.