Abstract
The distribution and prevalence of H3 subtype influenza viruses in avian and mammalian hosts constitutes a potential threat to both human and avian health. We report a complete genome sequence of a novel reassortant H3N2 avian influenza virus. Phylogenetic analysis showed that HA and NA showed the highest sequence homologies with those of A/white-backed munia/Hong Kong/4519/2009 (H3N2). However, the internal genes had the highest sequence homologies with those of H6 and H7 subtypes. The data provide further evidence of the existence of a natural reassortant H3N2 strain in southern China.
GENOME ANNOUNCEMENT
Influenza A viruses belong to the family Orthomyxoviridae, containing a single-stranded negative-sense RNA genome in eight segments (5). They are divided into subtypes based on the two major surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA). So far, 16 HA and 9 NA subtypes have been identified (10). Generally, individual viruses are host specific (2, 9). However, one of the most frequently isolated subtypes is the H3 subtype influenza virus (4, 6) with its wide host range, including humans, pigs, canines, and horses (1). Previous studies demonstrated that some novel H3N2 subtype viruses were reassortant between H5N1 and H9N2 in southeastern China, South Korea, and Japan (7, 8, 11). Moreover, the reassortant events may have alerted the pathogenicity and host ranges of H3N2 subtype viruses.
A novel H3N2 avian influenza virus [A/Duck/Guang dong/W12/2011(H3N2)] was isolated from a live poultry market during 2011 in southern China. All 8 viral genes were amplified using segment-specific primers (3) with the OneStep RT-PCR premix kit (Qiagen). These PCR products were purified and sequenced on an ABI 3730 capillary DNA-sequencing instrument. Genome sequences were aligned using ClustalW in the MEGA5.0 software.
The isolate was further identified as an H3N2 subtype virus. The sequence homologies of the novel isolate were determined by comparison with those available in GenBank. Sequence analysis showed that HA and NA shared the highest sequence homologies, 94.6% and 96.5%, respectively, with those of A/white-backed munia/Hong Kong/4519/2009 (H3N2) (GenBank accession numbers AB557631 and AB557632, respectively). However, the four segments (PB2, PB1, M, and NS) had a close relationship with those of the H6 subtype, and the others (PA and NS) had the highest homologies with those of the H7 subtype. PB2 and PB1 showed the highest sequence homologies (92.5% and 96.1%, respectively) with H6N2 strains (GenBank accession numbers CY109424 and CY109239, respectively). M showed the highest sequence homology (98.9%) with an H6N6 strain (GenBank accession number CY110425). NS possessed the highest homology (97.2%) with an H6N8 strain (GenBank accession number CY098536). PA and NP had the highest sequence homologies, 97.9% and 98.8%, respectively, with H7N3 strains (GenBank accession numbers JN244177 and JQ906577, respectively). It was noteworthy that the reassortment had existed among H3N2 and H6 and H7 subtypes in southern China.
In this work, we found evidence of reassortment among H3N2 and H6 and H7 subtype avian influenza virus. This also emphasizes the importance of intensive monitoring for influenza virus in southern China.
Nucleotide sequence accession numbers.
The nucleotide sequences of A/Duck/Guang dong/W12/2011(H3N2) were deposited in the GenBank database under accession numbers from JX175250 to JX175257 for PB2, PB1, PA, HA, NP, NA, M, and NS, respectively.
ACKNOWLEDGMENTS
This work was supported by grants from the Natural Science Foundation of Guangdong Province (grant no. 10251064201000004), the Earmarked Fund for Modern Agro-Industry Technology Research System (nycytx-42-G3-03), and High-level Talents in University Project of Guangdong Province (2010).
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