title: Genetic variability among complete human respiratory syncytial virus subgroup A genomes: bridging molecular evolutionary dynamics and epidemiology.
abstract: Human respiratory syncytial virus (RSV) is an important cause of severe lower respiratory tract infections in infants and the elderly. In the vast majority of cases, however, RSV infections run mild and symptoms resemble those of a common cold. The immunological, clinical, and epidemiological profile of severe RSV infections suggests a disease caused by a virus with typical seasonal transmission behavior, lacking clear-cut virulence factors, but instead causing disease by modifying the host's immune response in a way that stimulates pathogenesis. Yet, the interplay between RSV-evoked immune responses and epidemic behavior, and how this affects the genomic evolutionary dynamics of the virus, remains poorly understood. Here, we present a comprehensive collection of 33 novel RSV subgroup A genomes from strains sampled over the last decade, and provide the first measurement of RSV-A genomic diversity through time in a phylodynamic framework. In addition, we map amino acid substitutions per protein to determine mutational hotspots in specific domains. Using Bayesian genealogical inference, we estimated the genomic evolutionary rate to be 6.47 × 10(-4) (credible interval: 5.56 × 10(-4), 7.38 × 10(-4)) substitutions/site/year, considerably slower than previous estimates based on G gene sequences only. The G gene is however marked by elevated substitution rates compared to other RSV genes, which can be attributed to relaxed selective constraints. In line with this, site-specific selection analyses identify the G gene as the major target of diversifying selection. Importantly, statistical analysis demonstrates that the immune driven positive selection does not leave a measurable imprint on the genome phylogeny, implying that RSV lineage replacement mainly follows nonselective epidemiological processes. The roughly 50 years of RSV-A genomic evolution are characterized by a constant population size through time and general co-circulation of lineages over many epidemic seasons - a conclusion that might be taken into account when developing future therapeutic and preventive strategies.
authors.affiliation: Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Lydia
authors.initials: L
authors.lastname: Tan
authors.forename: Philippe
authors.initials: P
authors.lastname: Lemey
authors.forename: Lieselot
authors.initials: L
authors.lastname: Houspie
authors.forename: Marco C
authors.initials: MC
authors.lastname: Viveen
authors.forename: Nicolaas J G
authors.initials: NJ
authors.lastname: Jansen
authors.forename: Anton M
authors.initials: AM
authors.lastname: van Loon
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Wiertz
authors.forename: Grada M
authors.initials: GM
authors.lastname: van Bleek
authors.forename: Darren P
authors.initials: DP
authors.lastname: Martin
authors.forename: Frank E
authors.initials: FE
authors.lastname: Coenjaerts
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D001483:Base Sequence; D001499:Bayes Theorem; D001530:Belgium / Q000453:epidemiology; D002675:Child, Preschool; D017931:DNA Primers / Q000235:genetics; D019143:Evolution, Molecular; D014644:Genetic Variation / Q000235:genetics*; D016679:Genome, Viral / Q000235:genetics*; D023281:Genomics / Q000379:methods; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008957:Models, Genetic; D008969:Molecular Sequence Data; D059645:Mutation Rate; D009426:Netherlands / Q000453:epidemiology; D060888:Real-Time Polymerase Chain Reaction; D018357:Respiratory Syncytial Virus Infections / Q000453:epidemiology* / Q000821:virology; D018113:Respiratory Syncytial Virus, Human / Q000235:genetics*; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D014759:Viral Envelope Proteins / Q000235:genetics
chemical_list: D017931:DNA Primers; D014759:Viral Envelope Proteins