Protection against diverse highly pathogenic H5 avian influenza viruses inchickens immunized with a recombinant fowlpox vaccine containing an H5 avian influenza hemagglutinin gene insert

A recombinant fowlpox vaccine with an H5 hemagglutinin gene insert protecte d chickens against clinical signs and death following challenge by nine dif ferent highly pathogenic Hi avian influenza viruses. The challenge viruses had 87.3 to 100% deduced hemagglutinin amino acid sequence similarity with the recombinant vaccine, and represented diversely geographic and spatial b ackgrounds; i.e. isolated from four different continents over a 38 year per iod. The recombinant vaccine reduced detectable infection rates and sheddin g liters by some challenge viruses. There was a significant positive correl ation in hemagglutinin sequence similarity between challenge viruses and va ccine, and the ability to reduce titers of challenge virus isolated from th e oropharynx (r(s) = 0.783, P = 0.009), but there was no similar correlatio n for reducing cloacal virus titers (r(s) = -0.100, P = 0.78). This recombi nant fowlpox-H5 avian influenza hemagglutinin vaccine can provide protectio n against a variety of different highly pathogenic H5 avian influenza virus es and frequent optimizing of the hemagglutinin insert to overcome genetic drift in the vaccine may not be necessary to provide adequate field protect ion. published by Elsevier Science Ltd.