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Isolation and molecular characterization of equine H3N8 influenza viruses from pigs in China

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During 2004–2006 swine influenza virus surveillance, two strains of H3N8 influenza viruses were isolated from pigs in central China. Sequence and phylogenetic analyses of eight gene segments revealed that the two swine isolates were of equine origin and most closely related to European equine H3N8 influenza viruses from the early 1990s. Comparison of hemagglutinin (HA) amino acid sequences showed several important substitutions. One substitution caused the loss of a potential glycosylation site, and two substitutions, located at the cleavage site and adjacent to the receptor-binding pocket, respectively, had been reported previously in canine H3 HAs. This expansion of host range of equine H3N8 influenza viruses with mutations in the HA protein might raise the possibility of transmission of these viruses to humans.

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This work was supported by China National Basic Research Program (China “973” Program 2005CB523003), National Natural Science Foundation of China (No. 30800832) and China National Scientific and Technical Supporting Programs (No. 2006BAD06A11 and No. 2006BAD06A15). We thank Miss Xiao Xiao for critically reading the manuscript.

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Correspondence to Meilin Jin.

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J. Tu and H. Zhou contributed equally to the work.

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Tu, J., Zhou, H., Jiang, T. et al. Isolation and molecular characterization of equine H3N8 influenza viruses from pigs in China. Arch Virol 154, 887–890 (2009).

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