title: Phylogeny and population dynamics of respiratory syncytial virus (Rsv) A and B.
abstract: Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infections in infants and young children. RSV is characterised by high variability, especially in the G glycoprotein, which may play a significant role in RSV pathogenicity by allowing immune evasion. To reconstruct the origin and phylodynamic history of RSV, we evaluated the genetic diversity and evolutionary dynamics of RSV A and RSV B isolated from children under 3 years old infected in Italy from 2006 to 2012. Phylogenetic analysis revealed that most of the RSV A sequences clustered with the NA1 genotype, and RSV B sequences were included in the Buenos Aires genotype. The mean evolutionary rates for RSV A and RSV B were estimated to be 2.1 × 10(-3) substitutions (subs)/site/year and 3.03 × 10(-3) subs/site/year, respectively. The time of most recent common ancestor for the tree root went back to the 1940s (95% highest posterior density-HPD: 1927-1951) for RSV A and the 1950s (95%HPD: 1951-1960) for RSV B. The RSV A Bayesian skyline plot (BSP) showed a decrease in transmission events ending in about 2005, when a sharp growth restored the original viral population size. RSV B BSP showed a similar trend. Site-specific selection analysis identified 10 codons under positive selection in RSV A sequences and only one site in RSV B sequences. Although RSV remains difficult to control due to its antigenic diversity, it is important to monitor changes in its coding sequences, to permit the identification of future epidemic strains and to implement vaccine and therapy strategies.
authors: Department of Biomedical Sciences for Health, University of Milan, Via C. Pascal 36, 20133, Milan, Italy. Electronic address: marianna.martinelli@unimi.it.
authors: Marianna
authors: M
authors: Martinelli
authors: Department of Biomedical Sciences for Health, University of Milan, Via C. Pascal 36, 20133, Milan, Italy. Electronic address: elena.frati@unimi.it.
authors: Elena Rosanna
authors: ER
authors: Frati
authors: Department of Biomedical Sciences for Health, University of Milan, Via C. Pascal 36, 20133, Milan, Italy. Electronic address: alessandra.zappa@unimi.it.
authors: Alessandra
authors: A
authors: Zappa
authors: "L. Sacco" Department of Biomedical and Clinical Sciences, University of Milan, Via G. B. Grassi 74, 20157 Milano, Italy. Electronic address: erika.ebranati@unimi.it.
authors: Erika
authors: E
authors: Ebranati
authors: Department of Biomedical Sciences for Health, University of Milan, Via C. Pascal 36, 20133, Milan, Italy. Electronic address: silvia.bianchi@unimi.it.
authors: Silvia
authors: S
authors: Bianchi
authors: Department of Biomedical Sciences for Health, University of Milan, Via C. Pascal 36, 20133, Milan, Italy; CIRI-IT, Department of Health Sciences, University of Genoa, Via A. Pastore 1, 16132 Genoa, Italy. Electronic address: elena.pariani@unimi.it.
authors: Elena
authors: E
authors: Pariani
authors: Department of Biomedical Sciences for Health, University of Milan, Via C. Pascal 36, 20133, Milan, Italy; CIRI-IT, Department of Health Sciences, University of Genoa, Via A. Pastore 1, 16132 Genoa, Italy. Electronic address: antonella.amendola@unimi.it.
authors: Antonella
authors: A
authors: Amendola
authors: "L. Sacco" Department of Biomedical and Clinical Sciences, University of Milan, Via G. B. Grassi 74, 20157 Milano, Italy. Electronic address: gianguglielmo.zehender@unimi.it.
authors: Gianguglielmo
authors: G
authors: Zehender
authors: Department of Biomedical Sciences for Health, University of Milan, Via C. Pascal 36, 20133, Milan, Italy; CIRI-IT, Department of Health Sciences, University of Genoa, Via A. Pastore 1, 16132 Genoa, Italy. Electronic address: elisabetta.tanzi@unimi.it.
authors: Elisabetta
authors: E
authors: Tanzi
mesh_terms: D002675:Child, Preschool; D019143:Evolution, Molecular; D005260:Female; D014644:Genetic Variation; D006801:Humans; D007223:Infant; D007558:Italy / Q000453:epidemiology; D008297:Male; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D012367:RNA, Viral / Q000235:genetics*; D018357:Respiratory Syncytial Virus Infections / Q000453:epidemiology / Q000821:virology*; D018113:Respiratory Syncytial Virus, Human / Q000145:classification* / Q000235:genetics* / Q000254:growth & development; D017422:Sequence Analysis, DNA
chemical_list: D012367:RNA, Viral
keywords: Evolutionary rate; G protein; Phylodynamic analysis; Phylogenetic analysis; Respiratory syncytial virus; Selective pressure