| Summary: | 碩士 === 國立臺灣大學 === 獸醫學研究所 === 94 === From 1986 to 2003, the avian influenza viruses (AIV) isolated in Taiwan were all low pathogenic. Some low pathogenic H5N2 AIVs were isolated in Taiwan in 2004, resulting in stamping 380 thousands chickens out from 22 poultry flocks. To test if the virus titers increased during passaging, H5N2 and H6N1 isolates were passaged in specific-pathogen-free embryonated eggs. After 45 passages, the virus titer of H5N2 increased 100 times, and two amino acid residues in HA1 of H5N2 virus were changed. The partial fragments of HA1 relating to neutralizing epitopes of the H5N2 and the H6N1 isolates were cloned in pGEX-5X-1 vector (prokaryotic expression) and pcDNA3.1 vector (eukaryotic expression) for expression. The purified recombinant proteins were intramuscualarly injected in 4-week-old SPF chickens for two times. Two weeks after the second immunization, the serum from H6-immunized chickens showed hemagglutination inhibition (HI) titers of 24 to 26, but no antibody was detected in H5-immunized chickens. To test the increase efficiency of liposome compounds on vaccine, Newcastle disease vaccines coated with liposome and with liposome/chitosan were used to immunize chickens. The results showed that Newcastle disease vaccine coated with liposome/chitosan increased HI titers in vaccinated chickens but not vaccine coated with lipsome alone.
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