title: Investigation into drug-resistant mutations of HBV from 845 nucleoside/nucleotide analogue-naive Chinese patients with chronic HBV infection.
abstract: BACKGROUND
  This study aimed to clarify the clinical significance of drug-resistant HBV in nucleoside/nucleotide analogue (NA)-naive Chinese patients with chronic HBV infection in real clinical practice.
  
  
  METHODS
  A total of 845 NA-naive patients who were admitted to Beijing 302 Hospital between July 2007 and March 2012 were included in the study. HBV drug-resistant mutations were examined by direct sequencing of the viral reverse transcriptase gene and verified by clonal sequencing. Phenotypic analysis of viral replication capacity and drug susceptibility were performed by measuring viral replicative intermediate level in 1.1-mer mutant or wild-type HBV amplicon-transfected HepG2 cells in absence or presence of serially diluted drugs.
  
  
  RESULTS
  Drug-resistant mutations were detected in 2.01% (17/845) of the patients by direct sequencing, including 15 with lamivudine-resistant mutations (rtM204V, rtM204I), one with adefovir-resistant mutation (rtA181V), and one with both lamivudine- and adefovir-resistant mutations (rtA181V, rtM204I). Clonal sequencing identified 13 drug-resistant HBV strains: rtL80I+M204I, rtL80I+M204V, rtL180M+M204I, rtL180M+M204V, rtM204I, rtM204V, rtL80I+L180M+M204I, rtL80I+L180M+M204V, rtA181V, rtA181V+M204I, rtA181T+N236T, rtA181V+N236T and rtN236T. Phenotypic analysis showed that two pre-existing lamivudine-resistant strains (rtL80I+M204I, rtL180M+M204V) had >1,000-fold resistance to lamivudine, and one pre-existing adefovir-resistant strain (rtA181V+N236T) had 15.4-fold resistance to adefovir compared with the wild-type strain. A follow-up study showed that the presence of pre-existing rtM204I strain in one patient increased from 20% at baseline to 85% after 13 months of entecavir treatment with corresponding recession of wild-type strain in the viral pool.
  
  
  CONCLUSIONS
  The incidence of drug-resistant HBV mutations was low in NA-naive Chinese HBV-infected patients. Pre-existing mutants had similar resistance characteristics to those from NA refractory patients.
authors.affiliation: Institute of Infectious Diseases and Liver Failure Research Center, Beijing 302 Hospital of PLA, Beijing, China.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Li
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.forename: Pan
authors.initials: P
authors.lastname: Zhao
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.forename: Shaojie
authors.initials: S
authors.lastname: Xin
authors.forename: Xin-Xin
authors.initials: XX
authors.lastname: Zhang
authors.forename: Dongping
authors.initials: D
authors.lastname: Xu
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000627:therapeutic use; D000328:Adult; D000998:Antiviral Agents / Q000627:therapeutic use*; D002681:China; D002999:Clone Cells; D024882:Drug Resistance, Viral / Q000235:genetics*; D005260:Female; D015870:Gene Expression; D005838:Genotype; D006147:Guanine / Q000031:analogs & derivatives / Q000627:therapeutic use; D056945:Hep G2 Cells; D006515:Hepatitis B virus / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D019694:Hepatitis B, Chronic / Q000188:drug therapy* / Q000473:pathology / Q000821:virology; D006801:Humans; D019259:Lamivudine / Q000627:therapeutic use; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009154:Mutation; D063065:Organophosphonates / Q000627:therapeutic use; D010641:Phenotype; D012194:RNA-Directed DNA Polymerase / Q000235:genetics* / Q000378:metabolism; D017422:Sequence Analysis, DNA; D014764:Viral Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism
chemical_list: D000998:Antiviral Agents; D063065:Organophosphonates; D014764:Viral Proteins; D019259:Lamivudine; C413685:entecavir; D006147:Guanine; C053001:adefovir; D012194:RNA-Directed DNA Polymerase; D000225:Adenine