Submitted to: International Poultry Forum Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 11/12/2006
Publication Date: 1/22/2007
Citation: Pfeiffer, J., Suarez, D.L. 2007. Molecular and antigenic characterization of recent H5N1 avian influenza isolates from Vietnam [abstract]. International Poultry Forum Proceedings. p. 30.
Technical Abstract: A recent sequence comparison of the hemagglutinin (HA) gene of Asian H5N1 avian influenza viruses isolated over the past 10 years demonstrated separation into three clades with recent isolates separating into two clades. Most reported viruses from Vietnam from 2001-2005 clustered in Clade 1, but 19 viruses isolated from the northern part of Vietnam from December 2005 all were clade 2 viruses. These viruses clustered into two sublineages, with no apparent clustering based on origin of the viruses. Genetic relatedness for the other genes also showed two unique clusters that correlated with the HA gene. Additionally, we evaluated the antigenic relatedness between these Vietnamese viruses by cross hemagglutination inhibition (HI) tests using antisera generated with DNA vaccines in chickens. Hemagglutinin-specific sera collected was to be used against either homologous antigen or antigen from the other Asian viruses against which antibodies to their HA genes were produced. We also wanted to evaluate the effectiveness of various vaccines using two Vietnamese challenge viruses that represented each genetic sublineage. Two-week old white leghorn chickens were vaccinated with one of five oil emulsion vaccines, two of which are currently used in Vietnam. Three weeks later, these birds were challenged with 106 EID50 virus. Clinical protection was seen with four of the vaccines, and real-time RT-PCR was used to evaluate levels of shedding among the groups. By compiling the data from these various analyses of the recently isolated Vietnam highly pathogenic H5N1 viruses, we will gain knowledge which can be applied to selecting vaccine seed strain viruses in the future.