Genomic analysis of a pneumovirus isolated from dogs with acute respiratory disease

A previously unrecognized virus belonging to the subfamily Pneumovirinae and most closely related to murine pneumovirus (MPV) was identified in domestic dogs in 2 related animal shelters. Additional diagnostic testing yielded 3 new viral isolates and identified 6 additional PCR positive dogs from other USA locations indicating that its distribution is not geographically limited. Nucleotide sequences encompassing 9 of the 10 genes were compared to the only 2 available MPV strains, 15 and J3666. Several features distinguished the canine pneumovirus (CnPnV) from the murine strains. Two regions of diversity were identified in the amino-proximal region of P and the overlapping P2 ORF was only 54 amino acids (aa) compared to 137 aa in MPV. The G protein had an amino-terminal cytoplasmic tail 18 aa longer than in the MPV strains. The CnPnV SH protein showed the highest divergence with only 90.2% aa identity when compared to MPV strain 15. Like strain 15, the CnPnV SH ORF coded for a protein of 92 aa while J3666 has a 114 aa variant. Comparison of CnPnV isolates at culture passages 4 and 17 revealed 7 nt differences within the 8598 nt sequenced. Of note was a substitution at nt 364 in G resulting in a termination codon that would produce a truncated G protein of 122 aa. Analysis of early passage and ex vivo samples showed the termination codon in G to be predominant after 6 days in culture indicating rapid selection of the mutation in A72 cells.