Phylogenetic Variation And Pathogenicity In Avian Influenza Virus Subtype H1N1 Isolated From Wild Mallard

An avian influenza A virus (AIV), designated A/Mallard/ SanJiang/390/2007, was isolated from the cloaca sample of a wild mallards collected in the Heilongjiang Sanjiang Nature Reserve region of China. The isolate was a H1N1 subtype virus as determined by sequence analysis. Subsequently, the eight full-length genes (PB2,PB1,PA,HA,NP,NA,M,NS) of the virus were amplified by RT-PCR technology and Sequencing by Beckman CEQTM8000 DNA Analysis System.Sequenced and the amino acid sequences near the cleavage site within viral hemagglutinin was PSIQSR↓GLFGAI, which is consistent with the consensus sequences of the low pathogenic influenza viruses(LPAIV).Phylogenetic analysis showed that the PA gene of the virus clustered within those from the viruses in North American clades, while the remaining genes belong to the eurasia clades; In addition, the virus does not close related to either swine influenza virus, seasonal human influenza virus or novel influenza virus A/H1N1 in 2009 as demonstrated by the phylogenetic analysis. HA subtype classification indicated that HA gene of the virus was in h1.1.2. The nucleotide homology of NP gene with A/duck/Hokkaido/Vac-3/2007(H5N1) AIV was 99.4%, the M gene was 99.6% with A/duck/Hokkaido/W90/2007(H10N7) AIV, while, PB1 and NP gene was 99.2% and 99.1% with A/swine/Korea/C 12/2008 (H5N2), respectively, which suggests that the MD/SJ/390/07(H1N1) may be a product of natural reassortment between different sublineages influenza viruses from domestic ducks and pigs.Infect SPF chickens, ducks artificial and observe for 28 days. The virus was found in the cloaca and organs of ducks, detected antibodies 2 weeks after, and also infected the control group in the way of horizontal transmission,but we could not isolate the virus in the throat, cloaca, organs of chicken completely, indicating that the A/MD/SJ/390/2007 (H1N1) avian influenza virus can infect the ducks but chickens.