ARS | Publication request: Glycoprotein gene truncation in avian metapneumovirus subtype C isolates from the United States

Submitted to: Virus Genes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 29, 2008
Publication Date: July 29, 2008
Citation: Velayudhan, B. T., Yu, Q., Nagaraja, K. V., Estevez, C. N., Halvorson, D. A. 2008. Glycoprotein gene truncation in avian metapneumovirus subtype C isolates from the United States. Virus Genes. 37(2):266-72.

Interpretive Summary: Avian metapneumovirus (aMPV) is an economically important pathogen of turkeys with a worldwide distribution. In the US, aMPV infection was first reported in Colorado in 1996, subsequently in Minnesota, resulting in a significant economic loss. Now there is serological evidence for the spread of aMPV to neighboring states of North Dakota, South Dakota, Iowa, and Wisconsin. To study the epidemiology of the US isolates, we examined twenty-one turkey isolates of aMPV-C obtained from 1996-2003. The early isolates of aMPV-C had a glycoprotein (G) gene of1,978 nucleotides (nt). This large G gene got truncated upon serial passages in cell cultures by deletion of 1,015 nt near the end of the G gene. The recent isolates of aMPV-C lacked the large G gene but instead had a small G gene of 782 nt, irrespective of cell culture passage levels. In some cultures, both large and small genes were detected, indicating the existence of a mixed population of the virus. Apparently, serial passage of aMPV-C in cell cultures and natural passage in turkeys led to truncation of the G gene, which may be a mechanism of virus evolution for survival in a new host or environment.

Technical Abstract: The published glycoprotein (G) gene sequences of Avian metapneumovirus subtype-C (aMPV-C) isolated from domestic turkeys and wild bids in the United States (1996-2003) remain controversial in length. To explore the relationship between G gene size variation and the year of isolation and cell culture passage levels, we examined twenty-one turkey isolates of aMPV-C at different passages. The early isolates of aMPV-C had a G gene of 1,978 nucleotides (nt) that coded for a predicted protein of 585 amino acids (aa) and showed >97% nt similarity with that of aMPV-C isolated from Canada geese. This large G gene got truncated upon serial passages in cell cultures by deletion of 1,015 nt near the end of the open reading frame. The recent isolates of aMPV-C lacked the large G gene but instead had a small G gene of 782 nt, irrespective of cell culture passage levels. In some cultures, both large and small genes were detected, indicating the existence of a mixed population of the virus. Apparently, serial passage of aMPV-C in cell cultures and natural passage in turkeys led to truncation of the G gene, which may be a mechanism of virus evolution for survival in a new host or environment.