Title: Evaluation of avian bivalent vaccines expressing the glycoprotein (G) of avian metapneumovirus subtype A or B by recombinant Newcastle disease viruses in turkeys Authors
Submitted to: Vaccine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 7, 2013
Publication Date: N/A
Interpretive Summary: Avian metapneumovirus (aMPV) is an economically important avian pathogen that can cause serious respiratory tract disease in poultry worldwide. Isolates of aMPV have been classified into four subtypes, A, B, C, and D, based on the level of genetic variations and antigenic differences. The aMPV subtypes A and B are present in Europe and most countries in the world, excluding the USA. To prevent aMPV subtype A and B viruses spreading to the US poultry farms and to reduce vaccination costs, we generated Newcastle disease virus (NDV), LaSota vaccine strain-based, recombinant viruses expressing the attachment glycoprotein (G) of aMPV subtype A or B virus as bivalent vaccines. Vaccination trials in turkeys showed that the bivalent vaccine candidates provided complete protection against virulent NDV challenge and partial protection against homologous aMPV-A or B infection. These results suggest that expression of other aMPV-A or -B virus immunogenic protein(s) or in conjunction with the G protein may be necessary to induce stronger and more protective immunity against aMPV diseases.
Technical Abstract: Avian metapneumovirus (aMPV) and Newcastle disease virus (NDV) are threatening avian pathogens that cause sporadic but serious respiratory diseases in poultry worldwide. Although, vaccination, combined with strict biosecurity practices, has been the recommendation for controlling these diseases in the field, new outbreaks are inevitable with current vaccines. In the present study, reverse genetics technology was used to construct NDV LaSota vaccine strain-based recombinant viruses that express the glycoprotein (G) of aMPV, subtype A or B, as bivalent, next-generation vaccines. These recombinant viruses, rLS/aMPV-A G and rLS/aMPV-B G, showed slight attenuation in vivo, yet maintained similar growth dynamics, cytopathic effects, and virus titers in vitro when compared to the parental LaSota virus. The expression of the aMPV G protein in recombinant virus-infected cells was detected by immunofluorescence. Vaccination of turkeys with rLS/aMPV-A G or rLS/aMPV-B G conferred complete protection against velogenic NDV, CA02 strain, challenge and partial protection against homologous pathogenic aMPV challenge. These results suggest that the LaSota recombinant virus may be a safe and effective vaccine vector and expression of the G protein alone is not sufficient to provide full protection against aMPV-A or -B infections. Expression of other aMPV-A or -B virus immunogenic protein(s) or in conjunction with the G protein may be necessary to induce stronger and more protective immunity against aMPV diseases.