title: Genetic variability and circulation pattern of human metapneumovirus isolated in Italy over five epidemic seasons.
abstract: Human metapneumovirus (hMPV) is an important aetiological agent of respiratory tract infection (RTI) in infants. Based on genetic differences, hMPVs are separated into two main groups, A and B, and two subgroups 1 and 2. To better understand the genetic diversity of hMPV, we analyzed 435 bp fragments of the F gene from 49 isolates obtained from a paediatric clinical centre in Northern Italy from 2005 to 2009. The phylogenetic analysis showed that our hMPV sequences clustered into five main clades (A1, A2a, A2b, B1, B2) statistically supported. Most of the strains belong to A2 (49%) and to B1 (28.5%) lineages. The intermixing in the phylogenetic tree showed no seasonal distribution between samples collected over a 5 year period. Mean genetic distances showed that clade A2 was more heterogeneous than others. In our F glycoprotein dataset we observed only two positively selected sites with an w value of 1.408 and 1.429, respectively, and 27 negatively selected sites. The two positively selected sites could be considered evolutionary "hot spots" because they were under positive selection and/or relaxed selective constraints. The abundant negatively selected sites reflect a high degree of conservation of F protein, probably necessary for viral infection.
authors.affiliation: Department of Infectious, Parasitic and Immunomediated Diseases, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Lo Presti
authors.forename: Roberta
authors.initials: R
authors.lastname: Cammarota
authors.forename: Paola
authors.initials: P
authors.lastname: Apostoli
authors.forename: Eleonora
authors.initials: E
authors.lastname: Cella
authors.forename: Simona
authors.initials: S
authors.lastname: Fiorentini
authors.forename: Muhammed
authors.initials: M
authors.lastname: Babakir-Mina
authors.forename: Marco
authors.initials: M
authors.lastname: Ciotti
authors.forename: Massimo
authors.initials: M
authors.lastname: Ciccozzi
mesh_terms: D058872:Epidemics / Q000706:statistics & numerical data*; D019143:Evolution, Molecular; D005814:Genes, Viral / Q000235:genetics; D014644:Genetic Variation / Q000235:genetics; D006801:Humans; D007558:Italy / Q000453:epidemiology; D029121:Metapneumovirus / Q000145:classification / Q000235:genetics*; D018184:Paramyxoviridae Infections / Q000453:epidemiology* / Q000821:virology*; D010802:Phylogeny; D012621:Seasons; D014760:Viral Fusion Proteins / Q000235:genetics
chemical_list: D014760:Viral Fusion Proteins