title: Clearance of the original hepatitis B virus YMDD-motif mutants with emergence of distinct lamivudine-resistant mutants during prolonged lamivudine therapy.
abstract: Tyrosine-methionine-aspartate-aspartate (YMDD)-motif mutants may emerge and elicit immune clearance during prolonged lamivudine treatment. The aim of this study was to investigate the virological events following development of the original mutants. Twenty-three patients who developed YMDD-motif mutants during the Asian lamivudine trial were included. Serial serum samples from these patients were subjected to sequence analysis to identify new mutants. Site-directed mutagenesis experiments were performed to investigate whether the new mutations were responsible for lamivudine resistance. Of the 23 patients included, 13 harbored either one or a mixture of the two common YMDD-motif mutants (methionine 552-to-isoleucine [M552I] and leucine 528-to-methionine/methionine 552-to-valine [L528M/M552V]) throughout the course, whereas in the remaining 10 patients, distinct mutants became dominant over the original mutants to cause continuing chronic hepatitis. Of them, 3 developed an alanine 529-to-threonine (A529T) mutant, 6 developed a leucine 528-to-methionine/methionine 552-to-isoleucine (L528M/M552I) mutant, and 1 developed these two mutants sequentially. Site-directed mutagenesis experiments confirmed that the aforementioned mutations were responsible for the resistance to lamivudine in vitro. The nucleotide substitution in the A529T mutant concomitantly generated a stop codon at the surface gene, leading to impaired secretion of HBsAg. Strikingly, the replication of this mutant was lamivudine dependent. These results suggested that distinct lamivudine-resistant mutants could emerge and replace the original YMDD-motif mutants as the cause of continuing chronic hepatitis during prolonged lamivudine therapy.
authors.affiliation: Liver Research Unit, Chang Gung Memorial Hospital and Chang Gung University School of Medicine, Taipei, Taiwan. catyeh@ms14.hinet.net
authors.forename: C T
authors.initials: CT
authors.lastname: Yeh
authors.forename: R N
authors.initials: RN
authors.lastname: Chien
authors.forename: C M
authors.initials: CM
authors.lastname: Chu
authors.forename: Y F
authors.initials: YF
authors.lastname: Liaw
mesh_terms: D000328:Adult; D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence / Q000235:genetics; D002986:Clinical Trials as Topic; D004352:Drug Resistance, Microbial / Q000235:genetics; D005260:Female; D005500:Follow-Up Studies; D006515:Hepatitis B virus / Q000187:drug effects* / Q000235:genetics*; D019694:Hepatitis B, Chronic / Q000188:drug therapy / Q000821:virology; D006801:Humans; D019259:Lamivudine / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D015337:Multicenter Studies as Topic; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D018894:Reverse Transcriptase Inhibitors / Q000627:therapeutic use*; D013997:Time Factors
chemical_list: D018894:Reverse Transcriptase Inhibitors; D019259:Lamivudine