Cloning and analysis of full-length genes of a H9N2 subtype avian influenza virus isolated from Guangdong / 病毒学报

Eight full-length genes of an avian influenza virus Chinese isolate of H9N2 subtype, A/Chicken/Guangdong/HL/2006 (H9N2) (abbreviated as Ck/GD/HL/06), were amplified by RT-PCR, including the 5' and 3' non-coding region. All the genes were cloned and sequenced. The phylogenetic analysis results showed the HA gene of Ck/GD/HL/06 was located in the same phylogenetic clade as Dk/HK/Y280/97 (H9N2), while the Dk/HK/Y280/97-like viruses had been predominately isolated from chickens in mainland China. After the analysis of glycosylation sites and receptor-binding sites in the HA, it was shown that the HA of Ck/GD/HL/06 exhibited the common feature of H9 subtype avian influenza virus isolated from China, but the leucine (Leu) residue at the amino acid position 226 indicated the potential of binding with SA alpha,2-6 receptor. The three internal genes of Ck/GD/HL/06 (PB1, PA and NP) had the highest nucleotide identity with A/Viet Nam/1203/2004 (abbreviated A/VN/1203/04) isolate, which was shown to be transmitted from chickens to human and caused lethal infection in human. No analogous H9N2 strains was reported in previous studies. Based on the high similarity of Ck/GD/HL/06 three genes to A/VN/1203/04, it was suggested that the possibility of generating new highly pathogenic H5N1 AIVs by recombination was worthy of our attention. Further studies should be needed for molecular epidemiologic surveillance of H9N2 AIV in the south China for a long time.

Molecular analysis of an avian influenza virus isolate of H5N2 subtype from parrot / 病毒学报

In 2005, an avian influenza virus stain was isolated from Parrot in Guangdong, which was then genotyped as H5N2 subtype and designated as A/Parrot/Guangdong/268/2005. According to the current OIE definition on the low-pathogenicity of avian influenza virus, the strain was recognized as a low pathogenic avian influenza virus due to the presence of one basic amino acid residue at the HA cleavage site. Some molecular characteristics of the virus, such as potential glycosylation sites in HA and NA, receptor binding sites of HA, and drug resistance site of NA, showed no variations. To analyze molecular evolution of this strain, we selected the sequences of H5N2 subtype AIVs from GenBank and established the phylogenetic trees. Our results indicated that this strain shared the highest homologies with the H5N2 LPAI isolate A/Pheasant/NJ/1355/1998-like. Phylogenic analysis revealed the isolate, together with A/Chicken/Pennsylvania/1/1983 (H5N2), belonged to America lineages and clustered with A/Pheasant/NJ/1355/1998-like.