title: Searching for antigen B genes and their adaptive sites in distinct strains and species of the helminth Echinococcus.
abstract: Twenty-seven PCR-derived antigen B (AgB) nucleotide sequences from four Echinococcus species (Echinococcus granulosus, Echinococcus multilocularis, Echinococcus oligarthrus and Echinococcus vogeli) were aligned with 78 already published sequences, to generate a maximum likelihood phylogeny of the AgB multigene family. The phylogenetic analysis confirms that the family is constituted by four groups of genes present in each one of the four species (AgB1, AgB2, AgB3 and AgB4), and suggests that it originated by ancient duplication events preceding speciation within the genus. AgB5 sequences, which had been formerly suggested to correspond to a putatively new AgB subunit, cluster with AgB3. Likelihood tests suggest that AgB gene evolution may have been driven by heterogeneous selection pressures acting on particular AgB1, AgB3 and AgB4 codons. No selection is detected in AgB2. We discuss implications of our findings in terms of AgB biology and its use as a diagnostic tool.
authors.affiliation: Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500 Prédio 43323, Caixa Postal 15053, Porto Alegre, RS, CEP 91501-970, Brazil. karen.haag@ufrgs.br
authors.forename: K L
authors.initials: KL
authors.lastname: Haag
authors.forename: P M A
authors.initials: PM
authors.lastname: Zanotto
authors.forename: L
authors.initials: L
authors.lastname: Alves-Junior
authors.forename: R B
authors.initials: RB
authors.lastname: Gasser
authors.forename: A
authors.initials: A
authors.lastname: Zaha
authors.forename: F J
authors.initials: FJ
authors.lastname: Ayala
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D000947:Antigens, Helminth / Q000235:genetics*; D004446:Echinococcus / Q000145:classification / Q000235:genetics* / Q000276:immunology; D019143:Evolution, Molecular; D017238:Genes, Helminth; D015801:Helminth Proteins / Q000235:genetics*; D008074:Lipoproteins / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family; D012641:Selection, Genetic; D013045:Species Specificity
chemical_list: D000947:Antigens, Helminth; D015801:Helminth Proteins; D008074:Lipoproteins; C089273:antigen B, Echinococcus