title: Insights into origins of Human T-cell Lymphotropic Virus Type 1 based on new strains from aboriginal people of Canada.
abstract: The causes of the worldwide distribution of Human T-cell Lymphotropic Virus Type 1 (HTLV-1) remain incompletely understood, with competing hypotheses regarding the number and timing of events leading to intercontinental spread on historical and prehistoric timescales. Ongoing discovery of this virus in aboriginal populations of Asia and the Americas has been the main source of evidence for the latter. We conducted molecular phylogenetic and dating analyses for 13 newly reported HTLV-1 strains from Canada. We analyzed two full-length proviral genomes from aboriginal residents of Nunavut (an autonomous territory in Northern Canada including most of the Canadian Arctic), 11 long-terminal-repeat (LTR) sequences from aboriginal residents of British Columbia's Pacific coast, and 2 LTR sequences from non-aboriginal Canadians. Phylogenetic analysis demonstrated a well-supported affinity between the two Nunavut strains and two East Asian strains, suggesting the presence of an Asian-American sublineage within the widespread "transcontinental" subgroup A clade of HTLV-1 Cosmopolitan subtype a. This putative sublineage was estimated to be 5400-11,900 years in age, consistent with a long-term presence of HTLV-1 in aboriginal populations of the Canadian Arctic. Phylogenetic affinities of the other 11 Canadian HTLV-1 aboriginal strains were diverse, strengthening earlier evidence for multiple incursions of this virus into coastal aboriginal populations of British Columbia. Our results are consistent with the hypothesis of ancient presence of HTLV-1 in aboriginal populations of North America.
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, 1015 Arlington Street, Winnipeg, MB, Canada R3E 3R2.
authors.forename: Anton
authors.initials: A
authors.lastname: Andonov
authors.forename: Michael B
authors.initials: MB
authors.lastname: Coulthart
authors.forename: Marcos
authors.initials: M
authors.lastname: Pérez-Losada
authors.forename: Keith A
authors.initials: KA
authors.lastname: Crandall
authors.forename: David
authors.initials: D
authors.lastname: Posada
authors.forename: Ruth
authors.initials: R
authors.lastname: Padmore
authors.forename: Antonio
authors.initials: A
authors.lastname: Giulivi
authors.forename: Joel J
authors.initials: JJ
authors.lastname: Oger
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Peters
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Dekaban
mesh_terms: D000368:Aged; D001106:Archaeology; D001499:Bayes Theorem; D001955:British Columbia; D016000:Cluster Analysis; D019143:Evolution, Molecular; D005260:Female; D016679:Genome, Viral; D023281:Genomics; D015490:HTLV-I Infections / Q000208:ethnology* / Q000821:virology*; D015368:Human T-lymphotropic virus 1 / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D004930:Inuit; D008875:Middle Aged; D020957:Nunavut; D010802:Phylogeny; D016415:Sequence Alignment; D020079:Terminal Repeat Sequences