title: Influence of time on the genetic heterogeneity of Spanish porcine reproductive and respiratory syndrome virus isolates.
abstract: The aim of the present study was to establish the degree of diversity of porcine reproductive and respiratory virus (PRRSV) isolates that circulate in the same geographical area in different years. Nucleotide sequences of open reading frame (ORF) 5 were determined for 28 Spanish field PRRSV isolates from different years and three European-type modified live virus vaccines. Sequences were aligned using Clustal W software and a phylogenetic tree constructed using the neighbour joining method. The results of pairwise homology comparisons of nucleotide and deduced amino acid sequences of these PRRSV isolates indicate a tendency for heterogeneity to increase with time. The study of the phylogenetic tree revealed that Spanish PRRSV isolates constitute two well-defined clades and a group of unrelated sequences. The observed heterogeneity does not appear to be due to temporal evolution exclusively. Early and recent isolates group themselves into different clusters independently of the time of isolation, indicating the co-circulation of different variants and the maintenance of variants of the original isolates in the field.
authors.affiliation: Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad Complutense de Madrid, Avda, Puerta de Hierro s/n, 28040 Madrid, Spain.
authors.forename: Cinta
authors.initials: C
authors.lastname: Prieto
authors.forename: Ana
authors.initials: A
authors.lastname: Vázquez
authors.forename: José I
authors.initials: JI
authors.lastname: Núñez
authors.forename: Esther
authors.initials: E
authors.lastname: Alvarez
authors.forename: Isabel
authors.initials: I
authors.lastname: Simarro
authors.forename: José M
authors.initials: JM
authors.lastname: Castro
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015967:Gene Expression Regulation, Viral; D014644:Genetic Variation; D008969:Molecular Sequence Data; D010802:Phylogeny; D019318:Porcine Reproductive and Respiratory Syndrome / Q000453:epidemiology / Q000821:virology*; D019316:Porcine respiratory and reproductive syndrome virus / Q000235:genetics*; D013030:Spain / Q000453:epidemiology; D013552:Swine; D013997:Time Factors; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D014764:Viral Proteins