| The two avian influenza A viruses (AIV), named A/Lesser White-fronted Goose/HuNan/412/2010(H7N7)(L-412) and A/Baer’s Pochard/HuNan/414/2010(H7N1)(29Y), were isolated from Lesser White-fronted Goose and Baer’s Pochard in HuNan, respectively. And the third was isolated from Common Pochard in XiangHai Natural Reserve Region of Jilin Province,, which was named A/Common Pochard/XiangHai/420/2010(H7N1)(865). The three H7 isolates were cloned through RT-PCR and sequenced. Characteristics of phylogenetic diversity, infectivity and receptor binding were analyzed, The results are as follows:1.Isolation, identification and phylogenetic of the three H7 AIVs from wild bird. Eight genes of the three isolates all grouped in Eurasian lineage. Six genes of L-412 were derived from Korean strains, L-412 NS shares high nucleotide homology of 98.2% and 97.7% with certain Northern American strains and human H7N7 of Netherlands in 2003. L-412 may be a product of reassortment between different Asian strains. Cross-species and gentic exchange within Eurasian and Northern American lineages also existed in L-412 NS. Eight genes of 29Y and 865 were all derived from Eurasian strains and shared high homology. The two PB1 genes shared more than 97% homology with human influenza virus of Italy(2013), Netherland(2003) and swine influenza virus of Korea(2008), NP genes belonged to the same lineage with certain human influenza viruses, swine influenza viruses and North American isolates. NS genes shared high homologies of 98.2% and 97.7% with some North American isolates and H7N7 human influenza virus of Netherland in 2003 respectively. Multiple amino acid sequence alignment analysis revealed that the 42th amino acid of the three NS genes mutated into S, indicating that our three isolates probably had high pathogenicity in mice.2.Analysis of the amino acid sequences near the cleavage site of the HA protein. The amino acid sequences were PEIPKGR↓GLFGAI, PELPKGR↓GLFGAI and PELPKGR↓GLFGAI, which were match to the characteristics of LPAIVs.3.Infectious analysis of L-412 in different animal. Infecting SPF chicken and duck artificial by nasal drops and eye droppings with 106EID50 and observing for 21 days. The virus was found mainly in the cloaca and multiple organs of chicken and ducks; the antibodies were detected in chicken and ducks at 14 days. This revealed that L-412 could replicate in chicken and duck,, while horizontal transmission occurred just in chicken.4. Infectious analysis of 29Y in different animal. Infecting SPF chicken, duck and mice with 106EID50 and observing for 21 days. The virus was found in several organs of chicken and ducks, but can not be found in throat and cloaca; the antibodies were detected in chicken and ducks at 14 days; the viruses also were found in the lung of mice. This revealed that 29Y could slightly infect chicken,duck and mice, and horizontal transmission occurred in ducks.5. Infectious analysis of 865 in different animal. Infecting SPF chicken, duck and mice through above method. The virus was found in throat, cloaca, multiple organs of chicken and ducks; the antibodies were detected in chicken and ducks at 14 days; the viruses also were found in the nasal bones, lung of mice. And indicating that the 865 isolate could infect the chicken, ducks and mice, and horizontal transmission occurred in both chicken and ducks.6.Characteristic of the receptor binding of the three H7 isolates. The erythrocyte of chicken were treated by a-2,3-sialidase and VCNA. According to HA experiment, we found the three H7 isolates could binding to both SAa-2,3Gal receptor and SAa-2,6Gal receptor. This revealed that the three H7 isolates could infect both avian and mammals. |
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