Avian Influenza Virus H9N2: Characterization and Control Strategies

Control of Avian Influenza (AI) infection is a highly topical subject of major economicimportance for the worldwide poultry industry at the national level and for international trade.H9N2 viruses are endemic in poultry throughout Asia and the Middle East, causing major losses inproduction. Moreover, these viruses pose wider threats since they have been isolated from bothswine and humans. At the same time, study of the AI viruses affords an opportunity to explore anumber of problems of intriguing scientific interest. The overall goal of this project was to developa sound control strategy for avian influenza subtype H9N2 viruses (AI H9N2) in commercialpoultry in Israel. The one-year feasibility study focused on two main goals, namely: to study themolecular characteristics of AI H9N2 circulating during the last seven years in Israel and todevelop tools enabling differentiation between the immune response to vaccination and infectionwith H9N2.Genetic and phylogenetic characterization of 29 selected AI H9N2 isolates (2000-2006)was performed by complete sequencing of hemagglutinin (HA), neuraminidase (NA), and all sixinternal genes [nucleoprotein (NP), polymerase basic 1 (PB1), polymerase basic 2 (PB2),polymerase acid (PA), matrix (M), and nonstructural (NS) genes]; comparative phylogenetic andgenetic analyses of these sequences; and comparative genetic analyses of deduced amino acidsequences of the HA, NA, NS1, and NS2 proteins. The major conclusions of the molecularanalyses were: (1) Israeli isolates, together with other H9N2 viruses isolated in Middle Eastcountries, comprise a single regional sublineage related to the G1-lineage. In addition, Israeliisolates subdivided into three different subgroups. Genetic analysis of these viruses suggests thatthey underwent divergent evolution paths.