Subgroup C avian metapneumovirus (MPV) and the recently isolated human MPV exhibit a common organization but have extensive sequence divergence in their putative SH and G genes

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Abstract
The genes encoding the putative small hydrophobic (SH), attachment (G) and polymerase (L) proteins of the Colorado isolate of subgroup C avian pneumovirus (APV) were entirely or partially sequenced. They all included metapneumovirus (MPV)-like gene start and gene end sequences. The deduced Colorado SH protein shared 26·9 and 21·7 % aa identity with its counterpart in human MPV (hMPV) and APV subgroup A, respectively, but its only significant aa similarities were to hMPV. Conserved features included a common hydrophobicity profile with an unique transmembrane domain and the conservation of most extracellular cysteine residues. The Colorado putative G gene encoded several ORFs, the longer of which encoded a 252 aa long type II glycoprotein with aa similarities to hMPV G only (20·6 % overall aa identity with seven conserved N-terminal residues). The putative Colorado G protein shared, at best, 21·0 % aa identity with its counterparts in the other APV subgroups and did not contain the extracellular cysteine residues and short aa stretch highly conserved in other APVs. The N-terminal end of the Colorado L protein exhibited 73·6 and 54·9 % aa identity with hMPV and APV subgroup A, respectively, with four aa blocks highly conserved among Pneumovirinae. Phylogenetic analysis performed on the nt sequences confirmed that the L sequences from MPVs were genetically related, whereas analysis of the G sequences revealed that among MPVs, only APV subgroups A, B and D clustered together, independently of both the Colorado isolate and hMPV, which shared weak genetic relatedness at the G gene level.