Abstract
Avian metapneumovirus (AMPV) infects the respiratory and reproductive tracts of domestic poultry, resulting in substantial economic losses for producers. Live attenuated vaccines appear to be the most effective in countries where the disease is prevalent. However, reversion to virulence has been demonstrated in several studies. Therefore, the development of a stable and safe next generation vaccine against the AMPV disease is needed. In the present study, we generated a recombinant Newcastle disease virus (NDV) vectoring the fusion (F) protein and glycoprotein (G) genes of AMPV subtype-C (AMPV-C) as a bivalent vaccine candidate using reverse genetics technology. The recombinant virus, rLS/AMPV-C F&G, was slightly attenuated in vivo, yet maintained similar characteristics in vitro when compared to the parental LaSota virus. Vaccination of turkeys with rLS/AMPV-C F&G induced both AMPV-C and NDV-specific antibody responses, and provided significant protection against pathogenic AMPV-C challenge and complete protection against velogenic NDV challenge. These results suggest that the rLS/AMPV-C F&G recombinant virus is a safe and effective bivalent vaccine candidate and that the expression of both F and G proteins of AMPV-C induces a protective response against the AMPV-C disease.
Highlights
Avian metapneumovirus (AMPV) causes turkey rhinotracheitis (TRT), an acute upper respiratory tract infection in turkeys, and is associated with swollen head syndrome (SHS) in chickens, resulting in substantial economic losses to the poultry industry[1, 2]
We generated Newcastle disease virus (NDV) LaSota vaccine strain-based recombinant viruses expressing the glycoprotein (G) of AMPV-A, B, and C viruses as bivalent vaccines[13, 25]. These vaccine candidates were stable and safe in embryonated chicken eggs and vaccinated turkeys, they conferred only partial protection against homologous AMPV challenge in turkeys. It suggests that the G protein alone may be a weak antigen and other viral immunogenic components may be needed in combination to improve efficacy against AMPV diseases
A full-length cDNA clone encoding the complete antisense genome of the NDV LaSota vaccine strain and the F and G genes of AMPV subtype-C (AMPV-C) inserted between the F and HN genes of NDV was constructed using molecular biology techniques (Fig. 1)
Summary
Avian metapneumovirus (AMPV) causes turkey rhinotracheitis (TRT), an acute upper respiratory tract infection in turkeys, and is associated with swollen head syndrome (SHS) in chickens, resulting in substantial economic losses to the poultry industry[1, 2]. We generated Newcastle disease virus (NDV) LaSota vaccine strain-based recombinant viruses expressing the glycoprotein (G) of AMPV-A, B, and C viruses as bivalent vaccines[13, 25]. These vaccine candidates were stable and safe in embryonated chicken eggs and vaccinated turkeys, they conferred only partial protection against homologous AMPV challenge in turkeys. It suggests that the G protein alone may be a weak antigen and other viral immunogenic components may be needed in combination to improve efficacy against AMPV diseases. In the present study, we re-engineered the recombinant LaSota/AMPV-C G virus[13, 25] to express the F protein of AMPV-C, in combination, in an effort to improve the vaccine efficacy against AMPV-C disease
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