The RNA of the hemagglutinin (HA) gene of A/Chicken/Guangdong/SS/1994 (H9N2) was reverse transcription–polymerase chain reaction amplified, and the cDNA was cloned into a plasmid vector. The complete coding sequence of the HA gene was sequenced and included 1683 nucleotides, which encoded for a protein of 560 amino acids. The potential glycosylation sites related to HA protein function were highly conserved. The amino acid sequence of the HA proteolytic cleavage was G-S-S-R/G. This cleavage site sequence is compatible with a low-pathogenic avian influenza virus. Sequence comparison of this HA gene with other H9 influenza virus sequences in the GenBank database showed a 82%–97% nucleotide and amino acid sequence similarity.

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