Complete Genome Sequence of an H10N8 Avian Influenza Virus Isolated from a Live Bird Market in Southern China

GENOME ANNOUNCEMENT

Influenza A virus belongs to the family Orthomyxoviridae (3). Based on the antigenic properties of the hemagglutinin (HA) and neuraminidase (NA) glycoproteins, influenza A viruses are classified into 17HA and 10NA subtypes (8, 9). Most subtypes of influenza A virus have been found in aquatic birds, which are the natural reservoir of influenza A virus (9). For a long time, southern China has been considered a hypothetical epicenter for facilitating the emergence of pandemic influenza viruses in the world (6). In recent years, several subtypes of avian influenza viruses (AIVs) have been circulating and evolving in southern China, including H3, H5, H6, and H9 (1, 2, 4, 5, 7). In such an environment, live bird markets (LBM) in southern China are an important source of AIV dissemination, where diverse subtypes of AIVs have been isolated (5). Thus, continuous epidemiological surveillance in LBM is very important to investigate the evolution of known and unknown AIVs.

In this study, an H10N8 strain, named A/Duck/Guangdong/E1/2012 (H10N8), was isolated from LBM in Guangdong Province in southern China in January 2012. We analyzed the complete genome sequence of the strain to investigate molecular characteristics and do further research. The PCR products were cloned into the pMD18-T vector (TaKaRa) and sequenced with an Applied Biosystems (ABI) 3730 genome analyzer. To our knowledge, this is the first report that H10N8 AIV was isolated in Guangdong.

The complete genome of the strain consists of eight segments of negative-sense single-stranded RNA molecules, including PB2, PB1, PA, HA, NP, NA, M, and NS. The lengths of the segments are 2,341, 2,341, 2,233, 1,728, 1,565, 1,460, 1,027, and 890 nucleotides, respectively. The eight genes encode proteins with the following amino acid lengths: PB2, 759; PB1, 757; PA, 716; HA, 561; NP, 498; NA, 470; M1, 252; M2, 97; NS1, 230; and NS2, 121. The amino acid sequence at the cleavage site in the HA molecule is PEIVQER↓GLF, with the characteristics of low-pathogenicity AIV. No deletions were found in any of the HA, NA, or NS genes. Analysis of potential N-glycosylation sites of surface proteins indicated that the strain possesses six potential N-glycosylation sites at positions 29, 45, 252, 306, 422, and 494 in HA and seven at positions 28, 46, 54, 84, 144, 293, and 398 in NA. The strain has Q226 and G228 (H3 numbering) at the receptor binding site in HA protein, which suggests that it is an avian-origin influenza virus. Phylogenetic analysis demonstrated that the HA gene belongs to the Eurasian lineage, while the NA gene belongs to the North American lineage.

In conclusion, the genome sequence of the strain is the first genome information on H10N8 AIV in Guangdong. These data are helpful for analyses of epidemiology and evolutionary characteristics of AIV in southern China.