|Njenga, M Kariuki|
Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2003
Publication Date: 4/1/2003
Citation: ALVAREZ, R., LWAMBA, H.M., KAPCZYNSKI, D.R., NJENGA, M., SEAL, B.S. NUCLEOTIDE AND PREDICTED AMINO ACID SEQUENCE ANALYSIS OF THE AVIAN METAPNEUMOVIRUS TYPE C CELL ATTACHMENT GLYCOPROTEIN (G) GENE. PHYLOGENETIC ANALYSIS AMONG THE PNEUMOVIRINAE AND MOLECULAR EPIDEMIOLOGY OF U.S. VIRUSES. JOURNAL OF CLINICAL MICROBIOLOGY. 2003. 1730-1735.
Interpretive Summary: Avian metapneumoviruses (aMPV) are the causative agents of turkey rhinotracheitis (TRT). Prior to 1996 this disease was not present in the North America and was considered an exotic animal pathogen in the United States. The disease first occurred among commercial turkeys in Colorado and subsequently spread to the north-central United States. Investigators at the Southeast Poultry Research Laboratory (SEPRL) in the Agricultural Research Service were the first to report that aMPV isolates in the United Sates were genetically different from European viruses and should be considered a new subtype. Now SEPRL scientists have extended these observations by reporting the genetic sequence of the aMPV protein that the virus uses to attach to cells during an infection. This attachment G protein exhibits the most variation among all the aMPV proteins encoded by the viral genome. Isolates from the north-central United States obtained following the initial outbreak have evolved so that their G proteins are very different from the original virus isolated during the initial TRT outbreak. This may affect construction of new vaccines and diagnostics to control the disease because antibodies made to the G protein are considered protective against the virus. Furthermore, the aMPV proteins form the United States virus are more closely related to a recently identified human metapneumovirus (hMPV) than to the other European metapneumoviruses isolated from birds.
Technical Abstract: A serologically distinct avian metapneumovirus (aMPV) was isolated in the U.S. following an outbreak of turkey rhinotracheitis (TRT) during February of 1997. The newly recognized U.S. virus was subsequently demonstrated to be genetically distinct from European subtypes and was designated aMPV/C. We have determined gene nucleotide and predicted amino acid sequence of the cell attachment (G) glycoprotein of aMPV type C (aMPV/C; Colorado and three Minnesota isolates) by sequencing cloned cDNAs synthesized from intracellular RNA of aMPV/C infected cells. The nucleotide sequence comprised 1321 nucleotides with only one predicted open reading frame encoding a protein of 435 amino acids, with a predicted Mr 48,840. Structurally, the predicted G protein of aMPV/C maintained similar characteristics to the human respiratory syncytial virus (hRSV) attachment G protein, including two mucin-like regions (heparin-binding domains) flanking both sides of a CX3C chemokine motif present in a conserved hydrophobic pocket. Comparison of the deduced G protein sequence of aMPV/C with that of aMPV types A, B, and D, as well as hRSV revealed overall predicted amino acid sequence identities ranging from 4 to 16.5%, suggesting a distant relationship. However, G protein sequence identities ranged from 72% to 97% when aMPV/C was compared to other members within the aMPV/C subtype or 21% for the recently identified human metapneumovirus (hMPV) G protein. Ratios of non-synonymous to synonymous nucleotide changes were greater than one in the G gene when comparing the more recent Minnesota isolates to the original Colorado isolate. Epidemiologically this suggests some form of positive selection among U.S. isolates since the first outbreak of TRT in the U.S.