title: Evidence for the adaptive evolution of ORF5 gene of Porcine reproductive and respiratory syndrome virus isolated in China.
abstract: Porcine reproductive and respiratory syndrome virus (PRRSV) ORF5 gene encoding an envelope glycoprotein involved in humoral immunity is the most variable protein-coding gene of PRRSV. The present study aimed to identify potential selective pressures acting on the ORF5 gene of PRRSV isolates of North American type prevalent in China. The non-synonymous to synonymous rate ratio ω (dN/dS) was employed as a measure of selective pressure at the codon level. An overall ω of 0.45 indicated negative (purifying) selection as the major driving force operating on the ORF5 gene during adaptation of the virus to swine. Determination of ω values for individual amino acids sites revealed 8 positively selected sites, most of them situated in the N-terminal ectodomain, indicating their potential role in the binding of virus to the cellular receptors. Further, 75 negatively selected sites were identified in the rest of molecule, probably as a result of functional or immunological constraints. Determination of potential N-glycosylation sites revealed 7 sites, four of which coincided with the positively selected ones. These results indicated that a specific adaptive evolution has operated on the ORF5 gene of Chinese PRRSV isolates. It is hoped that the disclosed adaptive sites might help identify a candidate antigenic epitope for the use in vaccine against this serious swine disease.
authors.affiliation: Huazhong Agricultural University, Wuhan, People's Republic of China.
authors.forename: Z
authors.initials: Z
authors.lastname: Xu
authors.forename: X
authors.initials: X
authors.lastname: Chang
authors.forename: S
authors.initials: S
authors.lastname: Xiao
authors.forename: H
authors.initials: H
authors.lastname: Chen
authors.forename: R
authors.initials: R
authors.lastname: Zhou
mesh_terms: D000222:Adaptation, Physiological; D020816:Amino Acid Motifs; D000818:Animals; D002681:China; D019143:Evolution, Molecular; D019318:Porcine Reproductive and Respiratory Syndrome / Q000821:virology*; D019316:Porcine respiratory and reproductive syndrome virus / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology; D012641:Selection, Genetic; D013552:Swine; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D014759:Viral Envelope Proteins; C114789:glycoprotein 5, PRRSV