Research Of HA、NA Gene Analysis And Antigenic Variation Of Pandemic A/H1N1Influenza Virus

Influenza A viruses are responsible for sporadic pandemics that usually cause highermortality rates than seasonal influenza epidemics. The most severe pandemic occurred in1918, resulted in approximately40million edaths worldwide and subsequently, there werepandemics in1957and1968. During March and April of2009, several areas in Mexicobegan reporting large numbers of patients presenting with influenza-like illness. As of lateJuly2010, cases of pandemic2009S-OIV were confirmed in214countries and resulted inmore than18000deaths. Genetic analysis suggests that the pandemic strain is atriple-reassortant virus of swine origin containing genes from avian, swine and humaninfluenza viruses. HA is a surface glycoprotein as well as the most important antigen thatinduce protective immmunity in the host. Accumulation of point mutations in the HAproteins leads to antigenic drift. Drift variants emerge can escape from existing host’santibodies.The objectives of this study are to study genetic evolution analysis and antigenicmutation mechanism of pandemic A/H1N1influenza virus. We choose11strains of2009-2010ChangChun NanGuan human influenza viruses for genetic evolution analysis.Phylogenetic analysis of HA and NA amino acid sequence indicate that the viruses consistof multiple reassorted virus genes from different origins. In the present study, weidentified three mutations in the HA protein, S183P N156D and D222G, that partially andmost likely controlled the antigenic changes of pandemic H1N1viruses. In order toelucidate antigenic variation mechanism, we develop an eight-plasmid DNA transfectionsystem for the rescue of infectious influenza A virus from cloned cDNA as well as genemutation. The rescue of infectious influenza A virus is compared with the parental strain.HI assays against parental strain demonstrate that S183P N156D D222G mutationscaused minor antigenic changes. Mutations with triple mutations (S183P N156D D222G)and with double mutations (N156D S183P) had the highest impact by altering theantigenic changes to the parental strain. Our results could provide a technique for furtherstudy of A/Changchun/01/2009(H1N1), especially the biological character, structure andfunction. We also provide technical reference for other pathogens. At the same time, themost significant is improving public health security in new vaccine development aspect.Reverse genetics has now become a fundamental part of influenza virus research andthe generation of influenza vaccines. This efficient system, which does not require helper virus infection, should be useful in viral mutagenesis studies and in the production ofvaccine.