Submitted to: International Symposium on Avian Influenza
Publication Type: Abstract Only
Publication Acceptance Date: 1/20/2009
Publication Date: 4/5/2009
Citation: Guo, X., Bublot, M., Pritchard, N., Dickey, L., Thomas, C., Swayne, D.E. 2009. Lemna (duckweed) expressed hemagglutinin from avian influenza H5N1 protects chickens against H5N1 high pathogenicity avian influenza virus challenge [abstract]. Abstracts of the 7th International Symposium on Avian Influenza, April 5-8, 2009, Athens, Georgia. p. 62. Interpretive Summary:
Technical Abstract: In the last two decades, transgenic plants have been explored as safe and cost effective alternative expression platforms for producing recombinant proteins. In this study, a synthetic hemagglutinin (HA) gene from the high pathogenicity avian influenza (HPAI) virus A/chicken/Indonesia/7/2003 (H5N1) isolate was expressed using Biolex's LEX System, a proprietary protein expression system based on the aquatic plant Lemna (duckweed). The HA was highly expressed in the plant apoplast with the expected size by Western blot analysis, and had significant levels of hemagglutination activity. Crude plant extract was prepared from a transgenic Lemna line for evaluation of immunogenicity and efficacy in specific pathogen free (SPF) chickens. Significant serum hemagglutination inhibition titer using both homologous and heterologous antigens indicated that Lemna derived HA was highly immunogenic. Three-week-old SPF chickens were vaccinated subcutaneously with a single dose of Lemna derived HA formulated in a water-in-oil emulsion and were challenged with either the A/ck/Indonesia/7/2003 or the antigenic variant A/ck/WestJava/PWT-WU/2006 HPAI H5N1 isolates. Full and 80-90% protection were induced against A/ck/Indonesia/07/2003 and A/ck/WestJava/PWT-WU/2006, respectively. Full clinical protection was obtained in HA-vaccinated birds primed at one day of age with a fowlpox avian influenza vector vaccine and boosted at 3 weeks of age with Lemna derived HA vaccine (prime-boost scheme). Dramatic reduction in oropharyngeal shedding of challenge virus was observed for all vaccinates, and NP-based ELISA performed on sera samples clearly differentiated infected from non-infected chickens in the vaccinated groups. However, oral feeding of Lemna expressing HA to chickens did not induce protection from virulent challenge. In conclusion, Lemna expressed HA elicited a strong immune response and conferred excellent levels of protection in chickens against homologous and variant H5N1 challenge. Transgenic Lemna derived HA could be a safer and more cost-effective alternative for an injectible vaccine, with DIVA potential.