Fusion protein predicted amino acid sequence of the first US avian pneumovirus isolate and lack of heterogeneity among other US isolates

Avian pneumovirus (APV) was first isolated from turkeys in the west-central US following emergence of turkey rhinotracheitis (TRT) during 1996. Subseq uently, several APV isolates were obtained from the north-central US. Matri x (M) and fusion (F) protein genes of these isolates were examined for sequ ence heterogeneity and compared with European APV subtypes A and B. Among U S isolates the M gene shared greater than 98% nucleotide sequence identity with only one nonsynonymous change occurring in a single US isolate. Althou gh the F gene among US APV isolates shared 98% nucleotide sequence identity , nine conserved substitutions were detected in the predicted amino acid se quence. The predicted amino acid sequence of the US APV isolate's F protein had 72% sequence identity to the F protein of APV subtype A and 71% sequen ce identity to the F protein of APV subtype B. This compares with 83% seque nce identity between the APV subtype A and B predicted amino acid sequences of the F protein. The US isolates were phylogenetically distinguishable fr om their European counterparts based on F gene nucleotide or predicted amin o acid sequences. Lack of sequence heterogeneity among US APV subtypes indi cates these viruses have maintained a relatively stable population since th e first outbreak of TRT. Phylogenetic analysis of the F protein among APV i solates supports classification of US isolates as a new APV subtype C. (C) 2000 Elsevier Science B.V. All rights reserved.