Novel characteristics and polymorphisms of hemagglutinin subunit 1 of 2009-2011 A/H1N1 viruses in Zhejiang, China

Since the 2009 pandemic A/H1N1 influenza virus emerged in North American, two H1N1 peaks have been reported in Zhejiang, China. The first peak occurred in November 2009 and the second in January 2011. In this study, we collected and analyzed the HA1 sequences of the Zhejiang H1N1 viruses in 2009 and 2010-2011. The phylogenic tree of HA1 suggested that the Zhejiang viruses were all derived from the 2009 pandemic viruses in North American. The consensus informational spectrum (CIS) of HA1 showed that the receptor binding preference of the Zhejiang viruses was also the same as that of the North American viruses. However, a lot of mutations in HA1 happened during local transmission and some of them could significantly increase or decrease the amplitude at the dominant frequency in informational spectrum (IS), implying that they may influence the receptor binding affinity. The structure analysis showed that four critical mutations, K219I, D222G, G225R and A134T, occurred in the receptor binding sites, among which D222G may be essential for the emergence of a lethal strain.   Key words: Influenza, H1N1, Hemagglutinin, information spectrum, Zhejiang.