MOLECULAR CHARACTERIZATION OF THE HEMAGGLUTININ GENE AND ORAL IMMUNIZATION WITH A WATERFOWL-ORIGIN AVIAN INFLUENZA-VIRUS

Vaccination against highly pathogenic (HP) subtypes of avian influenza (AI) virus in poultry has been prohibited in the United States. Recen tly, policy has been changed to potentially allow use of inactivated v accines in emergency programs to control HP H5 and H7 AI. Vaccination with inactivated virus against non-highly pathogenic AI viruses has be en allowed in the U.S. turkey industry since 1979 (1) bur requires exp ensive handling of individual birds for parenteral inoculation. Oral i mmunization would provide a less expensive method to protect commercia l poultry from AI. Prime candidates for oral vaccines are waterfowl-or igin (WFO) isolates, which have a tropism for the alimentary tract. On e WFO isolate, A/mallard/Ohio/556/1987 (H5N9) (MOh87), was characteriz ed by determining the complete nucleotide sequence of its hemagglutini n (HA) gene. The HA protein of this isolate possessed a deduced amino acid sequence nearly identical to the consensus amino acid sequence fo r all published H5 genes, indicating that it has potential as a broadl y effective vaccine. Experimental results demonstrated measurable seru m antibody responses to orally delivered live and inactivated preparat ions of MOh87. Oral vaccination also protected chickens from diverse, lethal H5 AI virus challenge strains and blocked cloacal shedding of c hallenge virus.