Generation of recombinant avian metapneumovirus subgroup C (aMPV-C) viruses containing different length of the G gene.

Authors: Yu, Qingzhong; Estevez, Carlos; Kapczynski, Darrell; Zsak, Laszlo

Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/1/2009
Publication Date: 10/1/2009
Citation: Yu, Q., Estevez, C., Kapczynski, D.R., Zsak, L. 2009. Generation of recombinant avian metapneumovirus subgroup C (aMPV-C) viruses containing different length of the G gene. In: Proceedings of the 6th International Symposium on Avian Corona and Pneumoviruses and Complicating Pathogens, June 14-17, 2009, Rauischholzhausen, Germany. p. 315-325.

Interpretive Summary: Avian metapneumovirus, known as turkey rhinotracheitis virus, causes upper respiratory tract disease in turkeys and is also associated with swollen head syndrome of chickens, resulting in significant economic losses for the poultry industry worldwide. The glycoprotein G of the virus is believed to play a role in virus growth, virulence and immunity. To study the effects of the G gene length variation on these viral biological properties, we engineered two avian metapneumovirus C viruses with either the full-length G or a truncated short G gene. The biological properties of these two viruses were assessed in cell cultures and in turkeys, the natural host. The results showed that the large deleted portion (about 60%) of the G protein at the C-terminal is not essential for virus growth in cell cultures and in turkeys. The avian metapneumovirus C with the short G became less virulent in turkeys than the parental virus, but still induced immunoresponse that provided a significant protection from the disease. This study provides important information for future improved vaccine development.

Technical Abstract: Genetic variation in length of the G gene among different avian metapneumovirus subgroup C isolates has been reported. However, its biological significance in virus replication, pathogenicity and immunity is unknown. In this study, we developed a reverse genetics system for avian metapneumovirus C and generated two Colorado strain-based recombinant viruses containing either the full-length G gene derived from a Canadian goose isolate or a C-terminally truncated G gene of the Colorado strain. The truncated short G gene encodes 252 amino acids, which is 333 amino acids smaller than the full-length G (585 amino acids). The biological properties of these two recombinant G variants were assessed in Vero cells and in specific-pathogen-free turkeys. The results demonstrated that the large portion (333 amino acids) of the extracellular domain of the viral attachment protein is not essential for virus viability both in vitro and in vivo, but may play a role in enhancing virus attachment specificity and immunity in a natural host.