title: Evolutionary history of HIV-1 subtype B and F infections in Brazil.
abstract: OBJECTIVE
  To reconstruct the onset date of the HIV-1 B and F epidemics in Brazil based on virus diversification over time.
  
  
  METHODS
  We studied HIV-1 env V3 sequences (210 nt) with a known sampling year isolated from HIV-1 positive patients from Brazil between 1989 and 1997: 101 subtype B sequences and 41 subtype F sequences.
  
  
  METHODS
  HIV-1 V3 env sequences were grouped by year of collection and the relationship between the sampling years of HIV-1 sequences and their genetic distance to the reconstructed common ancestor (intra-population divergence) or to other sequences from the same year (intra-population diversity) was examined by using linear regression analysis.
  
  
  RESULTS
  Regression analysis of nucleotide distances, revealed a highly significant positive correlation between sampling years of subtype B and F V3 sequences and their intra-population divergence (P < 0.001) or diversity (P < 0.0001). In both subtype populations, the divergence and diversity increased at a rate of 0.5 and 0.9% per year, respectively. Considering these evolutionary rates, we estimate the onset of the subtype B and F HIV-1 epidemics in Brazil during early 1970s and early 1980s, respectively.
  
  
  CONCLUSIONS
  The consistent correlation between divergence and diversity of the V3 sequences with their sampling years indicates that the molecular clock is operational in the evolution of the HIV-1 in Brazil's epidemic, and show that subtypes B and F are evolving at a similar rate over time. The dating results suggest a discontinuous introduction of these subtypes in the Brazilian population.
authors.affiliation: Laboratory of AIDS and Molecular Immunology, Department of Immunology, Oswaldo Cruz Institute--Fiocruz, Rio de Janeiro, Brazil.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Bello
authors.forename: Monick L
authors.initials: ML
authors.lastname: Guimarães
authors.forename: Mariza G
authors.initials: MG
authors.lastname: Morgado
mesh_terms: D001938:Brazil / Q000453:epidemiology; D019143:Evolution, Molecular; D015752:Genes, env; D014644:Genetic Variation; D015658:HIV Infections / Q000453:epidemiology* / Q000821:virology; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D016014:Linear Models; D017720:Molecular Epidemiology / Q000379:methods; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013997:Time Factors