NZ 596823 Disclosed is a reassortant or recombinant influenza virus comprising a polynucleotide encoding a hemagglutinin polypeptide comprising the amino acid sequence of SEQ ID NO:6 (as disclosed in the specification). Also disclosed is the use of this virus in the manufacture of a medicament for the prophylactic or therapeutic treatment of a viral infection (especially viral influenza infection) in a subject. Further disclosed is method for producing reassortant influenza viruses in cell culture, the method comprising: a) introducing a plurality of vectors comprising an influenza virus genome into a population of host cells, which plurality of vectors comprises 6 internal genome segments of a first influenza strain； a first genome segment encoding a hemagglutinin polypeptide comprising the amino acid sequence of SEQ ID NO: 6 and a second genome segment encoding a neuramidinase polypeptide, and which population of host cells is capable of supporting replication of influenza viruses； b) culturing the population of host cells； and, c) recovering a plurality of reassortant influenza viruses.
