Submitted to: Western Poultry Disease Conference
Publication Type: Abstract Only
Publication Acceptance Date: 1/1/2004
Publication Date: 3/1/2004
Citation: Cruz-Coy, J.S., Karaca, K., Bublot, M., Pritchard, N., Beck, J.R., Swayne, D.E. 2004. Immunogenicity of A Fowl Pox Vectored AI Vaccine: Effect Of Adjuvant And Multiple Immunization In Seroconversion And In Protection VS Challenge With HP Avian Influenza In Birds With Pre-existing Fowl Pox Immunity. Western Poultry Disease Conference Proceedings, CD-Rom, 2004.
Technical Abstract: Avian influenza-Fowl pox vaccine, live fowl pox vector, H5 subtype (vFP89, licensed product Merial Select, Inc., Gainesville, GA), has been shown to be efficacious against the highly pathogenic (HP) Avian influenza (AI) virus A/chicken/Queretaro/15588-19/95 (H5N2), and eight other different HP H5 AI viruses (1, 2). However, the use of this vaccine in birds with pre-existing immunity to fowl pox has not provided protection against this HP AI challenge (3). The initial objective of this study (experiment 1) was to evaluate the primary and booster humoral immune responses to Avian influenza-Fowl pox, H5 vaccine (vFP89), administered to SPF chickens previously vaccinated with fowl pox (FP) using different doses and formulation (adjuvant administration). The second objective (experiment 2) was to confirm that the formulation of the vaccine in combination with the adjuvant induced immunity in SPF birds previously vaccinated with FP in a vaccination-challenge trial. Results from the first experiment showed that birds vaccinated at one-day of age with FP, and booster vaccinated with the vFP89-adjuvant formulation at 21 and 42-days of age, had seroconversion as measured by the Hemagglutination Inhibition (HI) test using the homologous vaccine antigen A/Turkey/Ireland /1378/83 (H5N8). Out of 15 vaccinated birds, 11 showed seroconversion (HI GMT 15) 21 days after the vFP89-adjuvant booster vaccination at 21-days of age, and 14 showed seroconversion (HI GMT 45) 21 days after the vFP89-adjuvant booster vaccination at 42-days of age. A similar vaccination schedule without the adjuvant formulation only induced seroconversion (HI GMT 11) in nine out of 14 birds, 21 days after the booster vaccination at 42-days of age with the vFP89 vaccine. When the dose of the vFP89 vaccine was increased ten fold (10X) at the booster vaccinations, 21 and 42-days of age, seroconversion occurred in 13 out 15 vaccinated birds (HI GMT 26) 21 days after the vFP89 booster vaccination at 42-days of age. In contrast, birds that were initially vaccinated with vFP89 at one or 21-days of age, and booster vaccinated with vFP89 at 21 or 42-days of age, had 100% seroconversion. The HI GMT's of these birds had a range of 34 to 160 at 21 to 63 days post-vaccination. The HI test was also run using the AI A/Turkey/Wisconsin/68 (H5N9) antigen, however, the HI GMT's obtained with the heterologous antigen were <8. Results from the second experiment, the vaccination-challenge trial, showed that 82% of the birds, vaccinated at one-day of age with FP, and booster vaccinated with the vFP89-adjuvant formulation at 21 and 42-days of age, were protected against the challenge with the HP AI virus A/chicken/Queretaro/15588-19/95 (H5N2) as shown by morbidity and mortality. Birds that were vaccinated with the same vaccination schedule without the adjuvant formulation showed no adequate protection against morbidity (64%) and mortality (45%). Single booster vaccination with the vFP89 vaccine, with or without the adjuvant formulation, at either 21 or 42-days of age did not protect birds from morbidity (64-91%) or mortality (64-82%). In birds without pre-existing immunity to FP, a single application of the vFP89 vaccine at 21-days-of age, alone or in combination with the adjuvant formulation, induced protection to morbidity and mortality. The protection conferred by the vFP89 vaccine without the adjuvant was 100% and 80% for the vaccine-adjuvant formulation. HI serology tests were conducted as described in the first experiment. Results were pending at the time the Abstract was submitted.