Project Number: 6612-32000-056-00
Start Date: Dec 19, 2007
End Date: Apr 30, 2011
1: Determine the molecular and biological characteristics of North American avian metapneumovirus (aMPV) isolates and un-characterized vaccine strains to enable epidemiological studies and understand the ecology of aMPV. The approaches to this objective are designed to study the pathogenic properties and virulence level of aMPV-C strains in turkeys and perform comparative sequence analyses of viral genomes isolated directly from infected animals. Selected, most virulent original or in vivo passaged viruses will be used to establish a consistent, well characterized challenge model of aMPV-C subtype strain in turkey. Earlier data indicate the feasibility of the aMPV genome sequencing. Our effort will focus on the development of a sensitive and specific RNA extraction/purification technique which can be used for direct sequencing of full viral genomes or genomic regions from tissue samples obtained from infected animals. 2: Identify and characterize aMPV determinants of pathogenesis to understand mechanisms of disease, immune evasion, and protective immunity that will form the basis for a technology driven vaccine discovery research program. The approaches to achieve this objective include the development of an in vitro reverse genetics system that will be used to generate aMPV recombinants with alterations/deletions within specific genes or genomic regions. Recombinant viruses will be characterized in vitro cell cultures and in vivo animal studies. Viral gene function(s) in pathogenicity and immunogenicity will be determined and genetically engineered recombinant viruses will be selected and characterized in further studies. 3: Develop molecular vaccine platforms that will lead to highly efficacious aMPV vaccines that have been rationally designed for control and eradication, including mass delivery capability and companion diagnostics to differentiate naturally infected from vaccinated birds. Selected, genetically modified aMPV-C recombinants will be evaluated as vaccine candidates in turkeys by vaccination and followed by challenge with the virulent wild type aMPV-C. Vaccine induced protection will be assessed by comparing disease manifestation in groups of vaccinated and challenged animals to those where birds were challenged without previous immunization. These "proof of concept" experiments will provide sufficient data to make a Go/No Go decision for an early development of a genetically modified live-attenuated aMPV-C subtype vaccine platform. To further evaluate protective immunity following vaccination both in laboratory and field conditions we will develop a diagnostic methodology which can be applied to differentiate between vaccinated and wild-type virus infected animals (DIVA). Efficacy studies along with the application of the developed companion diagnostic tests will be conducted to optimize some of the criteria that can influence vaccine performance. BSL2 certification dated 1/29/2008; BSL3 certification dated 5/15/2007.