Analysis Of Antigen Variation And Receptor Binding Characteristics Of HA Protein Of H9N2 Subtype Avian Influenza Virus

Since the 1990 s,H9N2 avian influenza virus has been circulated widely in the world.Although the H9N2 avian influenza is a low pathogenic influenza virus,it has caused great losses to the poultry industry.At the same time,H9N2 influenza virus can provide other genes to other viruses and infect human.It is caused great hidden dangers to the public health security and the human health.However,there are few studies about the transmission of the virus with different receptor binding ability.Therefore,we characterized the genetic variation,receptor-binding specificity,replication capability and transmissibility in chicken of 107 H9N2 influenza viruses which isolated from Shandong,Hunan,Hubei,Anhui,Shanghai,Guangdong,et al.The results are as follows:1 In this study,25 strains of H9N2 subtype avian influenza virus in 2015 were sequenced.Then,we constructed 8 phylogenetic trees of the 107 virus which were isolated from 2013-2015.The results showed that the H9N2 subtype influenza virus HA gene was mainly located in subgroup which belonged to CK/BJ/1/94,and the ?PB1,PA,NP and NA genes belonged to CK/SH/F/98 subfamily.While PB2,M and NS belonged to CK/Zhejiang/B2013/12 this new branch.2 According to the genotype analyze,the main genotype prevailing in 2013 to 2015 is B69 which is same to the virus from 2009 to 2012.3 The antigenicity of 21 H9N2 subtype avian influenza virus isolated from Shandong,Hunan,Hubei,Anhui,Shanghai,Guangdong and other regions was analyzed by Hemagglutination assay.The results showed that the antigenicity of H9N2 subtype AIV was changed during the period of 2013-2015,which was different from that of CK/Shanghai/F/98,and formation a new antigen group.Addition,we found the strain CK/Zhejiang/F242/2015 had little difference in antigenic coefficient,both with the early strain and the recent prevalent virus.It is possible to be the next vaccine candidate.3 To compared the difference of replication and transmission between the viruses which isolated in 1998-2006 and 2009-2012.According to the ability of shedding virus.The virus which isolated after 2009 were higher than early virus.All the virus isolated after 2009 can shed virus in cloaca and oropharynx.At the same times,the titers of virus which isolated after 2009 is higher than the virus isolated before 2006.The virus which isolated before 2006 only can be found in oropharynx.And no virus existed in cloaca.The virus replication level in vivo shows that the titers of 2009 virus in trachea and lung were much higher than the virus which isolated before 2006.From the level of replication in vivo,the virus titer of H9N2 subtype avian influenza virus in the trachea and lung were much higher than that in the past;Addition,from the result of transmission assay,we found the prevent virus can transmission from chicken to chicken,but the virus which isolated before 2006 could not transmission.The differences transmission ability between the viruses may be associated with different receptor binding specificity.4 The solid phase binding assay showed that the early H9N2 AIV were preference binding to ?-2,6-linked sialic acids.However,the prevent H9N2 AIV had changed of receptor-binding preference from a-2,3-linked sialic acids(avian-type receptors)to a-2,6-linked sialic acids(human-type receptors).This results revealed that the change of receptor binding specificity from a-2,3-linked sialic acids to a-2,6-linked Sias may enhance the ability of transmission.The genetic evolution,antigenicity and transmissibility were analyzed in our research.The results laid a theoretical foundation for the effective monitoring and prevention of the disease.At the same time,the harm of H9N2 subtype avian influenza should not be ignored.There is no vaccine suitable for the market,and our research group had synthesized a polysaccharide adjuvant and constructed a veterinary vaccine mucosal immune delivery system.The results of this study may provide a model antigen for the development of H9N2 subtype avian influenza vaccine,and can also be used as a candidate for the development and improvement of H9N2 subtype avian influenza vaccine,inactivated vaccine and other vaccines,Therefore,this study have great significance and potential application prospects for the rational development of new vaccines and the improvement of the existing vaccines.