title: Viral quasi-species evolution during hepatitis Be antigen seroconversion.
abstract: OBJECTIVE
  Although viral quasi-species evolution may be related to pathogenesis of disease, little is known about this in hepatitis B virus (HBV); consequently, we aimed to evaluate the evolution of HBV quasi-species in patients with well-characterized clinical phenotypes of chronic hepatitis B.
  
  
  METHODS
  Four cohorts of well-defined clinical phenotypes of chronic hepatitis B, hepatitis Be antigen (HBeAg) seroconverters (spontaneous seroconverters and interferon-induced seroconverters) and nonseroconverters (controls and interferon nonresponders) were followed during 60 months on average. Serum from 4 to 5 time points was used for nested polymerase chain reaction, cloning, and sequencing of the precore/core gene (20 clones/sample). Only patients with genotype B were used. Sequences were aligned using Clustal X, then serial-sample unweighted pair grouping method with arithmetic means phylogenetic trees were constructed using Pebble 1.0 after which maximum likelihood estimates of pairwise distances under a GTR + I + G model was assessed. Viral diversity and substitution rates were then estimated.
  
  
  RESULTS
  Analysis of 3386 sequences showed that HBeAg seroconverters had 2.4-fold higher preseroconversion viral sequence diversity (P = .0183), and 10-fold higher substitution rate (P < .0001) than did nonseroconverters, who had persistently low viral diversity (3.6 x 10(-3) substitutions/site) and substitution rate (2.2 x 10(-5) substitutions x site(-1) x month(-1)). After seroconversion, there was a striking increase in viral diversity. Most seroconverters had viral variants that showed evidence of positive selection, which was seen mainly after seroconversion.
  
  
  CONCLUSIONS
  The high viral diversity before a reduction in HBV DNA and before HBeAg seroconversion could either be related to occurrence of stochastic mutations that lead to a break in immune tolerance or to increased immune reactivity that drives escape mutations.
authors.affiliation: Department of Gastroenterology and Hepatology, National University Hospital, Singapore. mdclimsg@nus.edu.sg
authors.forename: Seng Gee
authors.initials: SG
authors.lastname: Lim
authors.forename: Yan
authors.initials: Y
authors.lastname: Cheng
authors.forename: Stephane
authors.initials: S
authors.lastname: Guindon
authors.forename: Bee Leng
authors.initials: BL
authors.lastname: Seet
authors.forename: Lay Yong
authors.initials: LY
authors.lastname: Lee
authors.forename: Peizhen
authors.initials: P
authors.lastname: Hu
authors.forename: Shanthi
authors.initials: S
authors.lastname: Wasser
authors.forename: Frank Josef
authors.initials: FJ
authors.lastname: Peter
authors.forename: Theresa
authors.initials: T
authors.lastname: Tan
authors.forename: Matthew
authors.initials: M
authors.lastname: Goode
authors.forename: Allen Gerard
authors.initials: AG
authors.lastname: Rodrigo
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D000998:Antiviral Agents / Q000627:therapeutic use; D001483:Base Sequence; D015331:Cohort Studies; D004279:DNA, Viral / Q000235:genetics; D019143:Evolution, Molecular; D005260:Female; D006510:Hepatitis B Antibodies / Q000276:immunology* / Q000378:metabolism; D006513:Hepatitis B e Antigens / Q000276:immunology* / Q000378:metabolism; D006515:Hepatitis B virus / Q000145:classification* / Q000235:genetics / Q000276:immunology*; D019694:Hepatitis B, Chronic / Q000188:drug therapy / Q000276:immunology / Q000821:virology*; D006801:Humans; D007372:Interferons / Q000627:therapeutic use; D008297:Male; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D010802:Phylogeny; D014758:Viral Core Proteins / Q000378:metabolism
chemical_list: D000998:Antiviral Agents; D004279:DNA, Viral; D006510:Hepatitis B Antibodies; D006513:Hepatitis B e Antigens; D014758:Viral Core Proteins; D007372:Interferons