| Partâ… H9N2 avian influenza is recognized as a continuing threat to both the animal and human public health. In Mainland China, H9N2 AIV was firstly isolated from chickens in Guangdong province in 1994, and then H9N2 AIV circulated widely in the domenstic poultry and had caused great economic losses in China.Previous study systemically ananlyzed representative H9N2 AIV isolated from poultry in Mainland China during 1996-2002, and revealed that all of the viruses originated from CK/BJ/1/94-like virus and formed multiple genotypes through complicated reassortment. In order to consecutively observe the change of the H9N2 AIV in Mainland China, 13 representative H9N2 subtype viruses isolated from poultry in Mainland China during 2003-2004 have been genetically analyzed in this study. Our results showed that 11 of 13 viruses bear the CK/BJ/1/94-like HA genes and CK/BJ/1/94 or G9-like NA genes, indicating that CK/BJ/1/94-like virus were still predominant in H9N2 subtype influenza epidemic in Mainland China. However, the other two viruses isolated from Guangdong province have G1-like HA and NA genes. Analysis of the entire genomes showed that Gl-like virus QA/GD/125/03 is a reassortant between Gl-like and other group viruses and formed a new genotype of Asian H9N2 viruses. It implied that the viruses containing some genes of Gl-like viruses were still circulating in the domestic poultry and started to infect chickens as well as quails. The detection of Gl-like virus, which had different antigenic properties and human influenza virus like amino acids at the receptor binding sites of HA gene, suggested that high attention need to be paid to the control of H9N2 viruses in both poultry and humans.Amino acids in the receptor-binding sites of the HA were associated with the receptor binding specificity. The Q226L mutation at receptor binding site primarily determined the change in receptor recognition during interspecies transfer. In this study, nine of the 13 H9N2 viruses had L at position 226 of HA, made it prefer to binding to SAa2, 6Gal moieties in human cell. Especially the combination of H183, E190 and L226 at receptor binding sits in CK/GD/123/03 and QA /GD/125/03, same as those in Gl and A/Hong Kong/1073/99, presenting typical human virus-like receptor binding specificity. Two additional potential glycosylation sites near the receptor binding sites of the head of HA may be associated with antigenicity and receptor binding characteristics and thus host range.We also found that some viruses isolated in same region of different species shared high homology of HA and NA genes, indicating that the H9N2 viruses had not been controled in time when the viruses invaded into certain region. Subsequently, poultry of different species will be infected simultaneously and make it hard to eliminated the viruses. Partâ…¡H5N1 highly pathogenic avian influenza is responsible for one of the most devastating diseases in domestic poultries and also has a substantial significance on public health. Vaccination is a useful method for the avian influenza control. Plasmid-based reverse genetics has been proved to be a powerful tool to generate ideal reassortant influenza vaccine candidates.H5N1-inactivated vaccine developed by reverse genetics based on A/Goose/Guangdong/1/96 has been widely used in our country. However, antigenic mutant has been found in some regions of Mainland China since 2006 and resent vaccine seems to be ineffective. New vaccine should be developed to prevent infection of those viruses.In this study, vaccine candidate strain H5N1(SX)/PR8 was generated based on representative antigenic mutant A/Chicken/Shanxi/2/2006. HA and NA genes were derived from A/Chicken/Shanxi/2/2006 and 6 internal genes were derived from a high growth virus A/Puerto Rico/8/34. Multiple basic amino acids in the cleavage site of HA were deleted.H5N1(SX)/PR8 inactivated vaccine is proved to bear the same antigenicity as antigenic mutant, high growth property and low pathogenicity. The application of the new vaccine will be beneficial to control the H5N1 high pathogenic avian influenza in our country.
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