|Hu, Haixia -|
|Zhao, Wei -|
Submitted to: China Poultry
Publication Type: Review Article
Publication Acceptance Date: June 11, 2012
Publication Date: June 30, 2012
Citation: Hu, H., Zhao, W., Yu, Q. 2012. Avian metapneumovirus molecular biology and development of genetically engineered vaccines. China Poultry. 34(12):1-5. Interpretive Summary: Avian metapneumovirus (aMPV) causes upper respiratory tract disease in turkeys and is also associated with “swollen head syndrome” of chickens, resulting in significant economic losses to the poultry industry worldwide. Vaccination combined with strict biosecurity is considered an effective measure in control of aMPV disease. Live attenuated vaccines have been used in the field and appeared to be effective. However, recent aMPV outbreaks in vaccinated poultry farms suggest the risk of vaccine virulence reversion. To overcome the problem of vaccine instability, an effort to develop a rationally designed, genetically stabled effective vaccine has been made. Here we review the molecular biology of aMPV to understand the molecular basis of virus pathogenicity and immunogenicity, and describe the recent development of genetically engineered vaccines by using reverse genetics technology.
Technical Abstract: Avian metapneumovirus (aMPV) is an economically important pathogen of turkeys with a worldwide distribution. aMPV is a member of the genus Metapneumovirus within the subfamily Pneumovirinae of the family Paramyxoviridae. The genome of aMPV is a non-segmented, single-stranded, negative-sense RNA of 13kb that contains eight genes, in the order 3’-nucleocapsid (N)-phosphoprotein (P)-matrix (M)-fusion (F)-second matrix (M2)-small hydrophobic (SH)-glycoprotein (G)-large polymerase (L)-5’, flanked by an untranslated 3’ leader and 5’ trailer. The membrane-associated F and G proteins are believed to play an important role in virus pathogenicity and immunogenicity. Expression of the F protein by a live fowlpox virus vector or a DNA vaccine induced immunoresponses in turkeys and provided a partial protection against challenge. However, the administration of these vaccines is not practical to large commercial poultry operations. Live attenuated vaccines appeared to be effective, but the risk of virulence reversion exists. To overcome these problems, the reverse genetics technology was used to genetically modify the vaccines. Different levels of success have been achieved for these designer’s vaccines, but further development is required before clinical trials. Recently, the Newcastle disease virus (NDV) LaSota vaccine strain was used to generate a recombinant vaccine expressing the G protein of aMPV-C. The recombinant NDV/aMPV-C G virus induced immunoresponses in turkeys to both NDV and aMPV-C and provided complete protection against NDV and partial protection against aMPV-C challenge. The results suggest other antigenic proteins of aMPV may be required for improving the protective immunity against aMPV infection.