Sequence and phylogenetic analyses of neuraminidase gene of Iranian seasonal influenza H1N1 viruses from 2005-2009 and corresponding vaccine strains.

Prophylaxis of influenza A virus infections is based on the vaccines inducing antibodies to the major viral antigens, hemagglutinin (HA) and neuraminidase (NA). Since these antigens continuously change during virus replication in various hosts, only the currently circulating strains should be used in the vaccines. Besides, monitoring of the naturally occurring changes in HA, NA, and respective genes, especially those associated with resistance to the NA inhibitors is necessary. The NA genes of 30 Iranian isolates of influenza H1N1 virus from the seasons 2005-2009 were sequenced and subjected to the sequence and phylogenetic analyses. The seasonal isolates turned out to be closely related to the corresponding vaccine strains, except for the 2007-2008 isolates, which also displayed a higher nucleotide variation. A resistance to the NA inhibitors was found in the 2008-2009 isolates only. The average nucleotide identities of the isolates with corresponding vaccine strains for the years 2005-2009 were 98.83%, 98.55%, 98.7%, 97.55%, and 98.76%, respectively.