Submitted to: Avian Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/24/2006
Publication Date: 3/1/2007
Citation: Bublot, M., Pritchard, N., Cruz, J.S., Mickle, T.R., Selleck, P., Swayne, D.E. 2007. Efficacy of a fowlpox-vectored avian influenza H5 vaccine against Asian H5N1 highly pathogenic avian influenza virus challenge. Avian Diseases. 51(Supplement):498-500. Interpretive Summary: Several avian influenza (AI) vaccines are available for use in poultry to protect against disease. This study examined how well recombinant fowlpox vaccine with influenza H5 gene insert performed in protecting chickens against two H5N1 highly pathogenic AI (HPAI) virus (S. Korea/2003 and Vietnam/2004). The vaccine protected chickens against disease and death after high challenge exposure to the S. Korea/2003 HPAI virus. Similarly, the vaccine protected against the Vietnam/2004 HPAI virus. These vaccines are useful in an AI control program.
Technical Abstract: A recombinant fowlpox-avian influenza (AI) H5 vaccine (rFP-AIV-H5) expressing the hemagglutinin of the A/turkey/Ireland/1378/83 H5N8 AI isolate has been used in Central America since 1998 to control H5N2 low pathogenicity (LP) AI. Previously, this vaccine was shown to induce full protection against a panel of H5 highly pathogenic (HP) AI isolates including HPAI H5N1. Here, we evaluate the efficacy of rFP-AIV-H5 against escalating doses of HPAI H5N1 A/chicken/SouthKorea/ES/03 isolate and against the HPAI H5N1 A/chicken/Vietnam/0008/2004 isolate. In both studies, one-day old SPF chickens were vaccinated by subcutaneous route with rFP-AIV-H5 and challenged 3 weeks later by the oro-nasal route. In the first study, full protection was observed up to a challenge dose of 6.5 log10 EID50 and the 50% chicken infectious dose was estimated to be 3.1 and 8.5 log10 EID50 in the control and the rFP-AIV-H5-vaccinated group, respectively. A 2-4 log10 and >4 log10 reduction of oral and cloacal shedding were observed in rFP-AIV-H5 vaccinated birds, respectively. The rFP-AIV-H5 vaccine induced HI antibodies (5.2 log2) detectable with the homologous H5N8 antigen. In the second study, rFP-AIV-H5-vaccinated chicks were fully protected against morbidity and mortality after challenge with the 2004 Vietnam isolate, whereas unvaccinated chickens died within 2 days after challenge. Shedding in cloacal swabs was detected in all unvaccinated controls and in none of the rFP-AIV-H5-vaccinated chickens. Altogether, these results confirm the excellent level of protection induced by rFP-AIV-H5 against recent Asian HPAI H5N1 isolates.