DNA immunization elicits high HI antibody and protects chicken from AIV challenge

Background: A highly pathogenic avian influenza virus of goose origin A/Goose/Guangdong/1/ 96 (H5N1) (GD/96) shared nucleotide homology of 98% in the HA with A/HK/156/97(H5N1). The nucleotide sequences at the cleavage site, all potential glycosylation sites and the receptor binding sites in the HA were conserved. The purpose of this study was to evaluate the immunogenicity and efficacy of a DNA vaccine to against this virus. Methods: The HA cDNA from GD/96 was cloned under a CMV promoter to generate vaccine plasmid pCIHA, which was administered to 3-week-old SPF chickens in two doses of 100 mug (n=9) or 50 mug (n=14) by the intramuscular route, 2 weeks apart. Chickens were challenged with 10 LD50 GD/96 at 2 weeks post-boost. Results: Hemagglutinin inhibition (HI) antibody titers were 2(5.8+/-2.0) and 2(4.7+/-2.5), 2 weeks after priming, 2(8.4+/-2.7) and 2(7.6+/-3.9) and 2 weeks after boost, and 2(9.6+/-2.2) and 2(9.0+/-2.4), 1 week after challenge in chicken immunized with 100- or 50-mug pCIHA, respectively. All immunized chickens were fully protected from the lethal challenge, with no clinical signs of disease, no virus shedding and 100% survival at 10 days postchallenge. Conclusion: The plasinid pCIHA is highly immunogenic and protects SPF chickens from lethal challenge with the homologous avian influenza virus GD/96. (C) 2001 Elsevier Science B.V. All rights reserved.