Submitted to: Vaccine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 7, 2010
Publication Date: April 18, 2010
Citation: Liljebjelke, K.A., Petkov, D., Kapczynski, D.R. 2010. Mucosal vaccination with a codon-optimized hemagglutinin gene expressed by attenuated Salmonella elicits a protective immune response in chickens against highly pathogenic avian influenza. Vaccine. 28(27):4430-4437. Interpretive Summary: Avian influenza (AI) is an economically important virus of poultry that has significant impact on global trade. Control of AI in poultry can be achieved by the use of vaccines. The AI hemagglutinin (HA) protein has been shown to be important for vaccine-induced protection, and many vaccines based on influenza HA antigens have shown efficacious in chickens against avian influenza challenge. In these studies we demonstrate protection of chickens against avian influenza with bacteria expressing the HA protein.
Technical Abstract: The purpose of this study was to evaluate the protection of two attenuated Salmonella enteria serovar typhimurium strains expressing the hemagglutinin (HA) gene from a highly pathogenic avian influenza (HPAI) H5N1 (A/whooper swan/Mongolia/3/2005), under control of the anaerobically inducible nir15 promoter in chickens against lethal challenge with HPAI. Two-week-old White Leghorn chickens were immunized by use of oral gavage tubes with one milliliter doses of >109 Salmonella colony-forming units once weekly for four weeks prior to challenge. Expression of the recombinant protein was confirmed in Salmonella via western blot, and expression in vivo of inoculated chickens confirmed by serology. Serum and mucosal samples were collected prior to, and following immunization and assessed for antibody activity by hemagglutination-inhibition (HI) assay. Antibodies against the avian influenza HA were confirmed in the serum four weeks post immunization by western blot and HI analysis. To determine protection, chickens were also challenged with homologous or a heterologous HPAI virus strain, A/chicken/Queretaro/147588-19/95 (H5N2). Chickens immunized with either of the two attenuated Salmonella strains containing the plasmid expression vector (pTETnir15HA), demonstrated a statistically significant increase in survival compared to the control groups. These results provide evidence for the effectiveness of the use of attenuated Salmonella strains as vectors for delivery of recombinant avian influenza HA antigens for induction of mucosal and systemic immune responses protective against lethal challenge with HPAI.