RESUMO
Human metapneumovirus (HMPV) is an important cause of acute respiratory illnesses in children. HMPV encodes two major surface glycoproteins, fusion (F) and glycoprotein (G). The function of G has not been fully established, though it is dispensable for in vitro and in vivo replication. We analyzed 87 full-length HMPV G sequences from isolates collected over 20 years. The G sequences fell into four subgroups with a mean 63 % amino acid identity (minimum 29 %). The length of G varied from 217 to 241 residues. Structural features such as proline content and N- and O-glycosylation sites were present in all strains but quite variable between subgroups. There was minimal drift within the subgroups over 20 years. The estimated time to the most recent common ancestor was 215 years. HMPV G was conserved within lineages over 20 years, suggesting functional constraints on diversity. However, G was poorly conserved between subgroups, pointing to potentially distinct roles for G among different viral lineages.
Assuntos
Sequência Conservada/genética , Glicoproteínas/genética , Metapneumovirus/genética , Proteínas Virais/genética , Sequência de Aminoácidos , Sequência de Bases , Pré-Escolar , Sequência Conservada/fisiologia , Variação Genética/genética , Glicoproteínas/fisiologia , Humanos , Metapneumovirus/fisiologia , Infecções por Paramyxoviridae/virologia , Filogenia , Reação em Cadeia da Polimerase em Tempo Real , Alinhamento de Sequência , Proteínas Virais/fisiologiaRESUMO
BACKGROUND: Human metapneumovirus (HMPV) is an important cause of acute respiratory illness in children. We examined the diversity and molecular evolution of HMPV using 85 full-length F (fusion) gene sequences collected over a 20-year period. RESULTS: The F gene sequences fell into two major groups, each with two subgroups, which exhibited a mean of 96% identity by predicted amino acid sequences. Amino acid identity within and between subgroups was higher than nucleotide identity, suggesting structural or functional constraints on F protein diversity. There was minimal progressive drift over time, and the genetic lineages were stable over the 20-year period. Several canonical amino acid differences discriminated between major subgroups, and polymorphic variations tended to cluster in discrete regions. The estimated rate of mutation was 7.12 x 10(-4) substitutions/site/year and the estimated time to most recent common HMPV ancestor was 97 years (95% likelihood range 66-194 years). Analysis suggested that HMPV diverged from avian metapneumovirus type C (AMPV-C) 269 years ago (95% likelihood range 106-382 years). CONCLUSION: HMPV F protein remains conserved over decades. HMPV appears to have diverged from AMPV-C fairly recently.