title: Prevalence, viral replication efficiency and antiviral drug susceptibility of rtQ215 polymerase mutations within the hepatitis B virus genome.
abstract: OBJECTIVE
  The rtQ215S mutation in the hepatitis B virus (HBV) polymerase has been described as a secondary mutation associated with resistance to lamivudine (LAM) and adefovir (ADV). We aimed at assessing the prevalence of substitutions at rtQ215 of the HBV polymerase and determining the molecular and functional consequences using phenotypic analyses in vitro.
  
  
  METHODS
  The polymerase region was directly sequenced in HBV isolates from a cohort of 249 HBV genotype D-infected patients from Iran (174 males/75 females, 194 treatment-nai ve/ 55 LAM-treated). Replication-competent HBV constructs containing the naturally occurring rtQ215H, rtQ215P and rtQ215S mutations were generated, and compared to wild-type, LAM- (rtM204I, rtL180M/rtM204V) and ADV-resistant (rtN236T) clones.
  
  
  RESULTS
  In an Iranian cohort of 249 HBV infected patients, 14.5% (36/249) showed mutations in the rtQ215 locus, namely 6.8% rtQ215S, 3.6% rtQ215P and 4.1% rtQ215H. The frequency of rtQ215 substitutions was higher in LAM-treated than treatment-nai ve patients (25% vs. 11%), but not associated with clinical complications. In phenotypic assays, rtQ215S, rtQ215P and rtQ215H constructs showed equivalent levels of viral replication as wild-type HBV, whereas LAM- and ADV-resistant mutants had significantly impaired replicative capacities. Furthermore, rtQ215S, rtQ215P and rtQ215H harbouring constructs remained susceptible towards treatment with LAM or ADV in vitro.
  
  
  CONCLUSIONS
  Our study reveals that rtQ215 substitutions in the HBV polymerase frequently occur in chronic hepatitis B, even without exogenous selection pressures. As these substitutions do neither impair the viral replication efficiency nor susceptibility to LAM or ADV in vitro, rtQ215 substitutions likely represent background polymorphisms rather than resistance mutations with clinical implications.
authors: Department of Medicine III, RWTH-University Hospital Aachen, Pauwelsstrasse 30, 52074 Aachen, Germany.
authors: Samad
authors: S
authors: Amini-Bavil-Olyaee
authors: Ulf
authors: U
authors: Herbers
authors: Seyed Reza
authors: SR
authors: Mohebbi
authors: Farzaneh
authors: F
authors: Sabahi
authors: Mohammad Reza
authors: MR
authors: Zali
authors: Tom
authors: T
authors: Luedde
authors: Christian
authors: C
authors: Trautwein
authors: Frank
authors: F
authors: Tacke
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019943:Amino Acid Substitution; D000998:Antiviral Agents / Q000494:pharmacology*; D001483:Base Sequence; D002648:Child; D015331:Cohort Studies; D017931:DNA Primers / Q000235:genetics; D024882:Drug Resistance, Viral / Q000235:genetics; D005260:Female; D015684:Gene Products, pol / Q000235:genetics*; D016679:Genome, Viral; D005838:Genotype; D006515:Hepatitis B virus / Q000187:drug effects* / Q000235:genetics* / Q000502:physiology; D019694:Hepatitis B, Chronic / Q000188:drug therapy / Q000821:virology; D006801:Humans; D007492:Iran; D019259:Lamivudine / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D063065:Organophosphonates / Q000494:pharmacology; D017354:Point Mutation; D014779:Virus Replication / Q000187:drug effects / Q000235:genetics; D055815:Young Adult
chemical_list: D000998:Antiviral Agents; D017931:DNA Primers; D015684:Gene Products, pol; D063065:Organophosphonates; C066027:P protein, Hepatitis B virus; D019259:Lamivudine; C053001:adefovir; D000225:Adenine