Generation and evaluation of a recombinant Newcastle disease virus expressing the glycoprotein (G) of avian metapneumovirus subgroup C as a bivalent vaccine in turkeys.

Virulent strains of Newcastle disease virus (NDV) and avian metapneumovirus (aMPV) can cause serious respiratory diseases in poultry. Vaccination combined with strict biosecurity practices has been the recommendation for controlling both NDV and aMPV diseases in the field. In the present study, an NDV based, LaSota strain recombinant vaccine virus expressing the glycoprotein (G) of aMPV subgroup C (aMPV-C) was generated as a bivalent vaccine using a reverse genetics approach. The recombinant virus, rLS/aMPV-C G was slightly attenuated in vivo, yet maintained similar growth dynamics, cytopathic effects, and virus titers in vitro when compared to the parental LaSota virus. Expression of the aMPV G protein in rLS/aMPV-C G-infected cells was detected by immunofluorescence assay. Vaccination of turkeys with one dose of rLS/aMPV-C G induced moderate aMPV-C-specific immune responses and comparable NDV-specific serum antibody responses to a LaSota vaccination control. Partial protection against pathogenic aMPV-C challenge and complete protection against velogenic NDV challenge was conferred. These results suggest that the LaSota recombinant virus is a safe and effective vaccine vector and that expression of the aMPV-C G protein alone is not sufficient to provide full protection against an aMPV-C infection. Expression of other immunogenic protein(s) of the aMPV-C virus alone or in conjunction with the G protein may be needed to induce a stronger protective immunity against the aMPV-C disease.