title: Dynamics of Genotypic Mutations of the Hepatitis B Virus Associated With Long-Term Entecavir Treatment Determined With Ultradeep Pyrosequencing: A Retrospective Observational Study.
abstract: The aim of the study is to explore the evolution of genotypic mutations within the reverse transcriptase region in partial virological responders (PVRs) receiving long-term entecavir (ETV) treatment. A total of 32 patients were classified as completely virological responders (CVRs) (n = 12) or PVRs (n = 20). Five partial responders were hepatitis B virus (HBV)-DNA positive after long-term therapy, which lasted for >3 years. A total of 71 serum samples from these 32 patients were assayed by ultra-deep pyrosequencing (UDPS): 32 samples were from all patients at baseline, and 39 were from PVRs with sequential inter-treatment. Approximately 84,708 sequences were generated per sample. At baseline, the quasispecies heterogeneity did not significantly differ between the 2 groups. The frequencies of substitutions indicating pre-existence of nucleos(t)ide analog resistant (NAr) mutants ranged from 0.10% to 6.70%, which did not statistically differ between groups either. However, the substitutions associated with the NAr mutants were significantly different from those associated with the non-NAr mutants in 13 patients; 6 of these patients were PVRs and the others were CVRs. Five patients were HBV DNA positive after regular ETV monotherapy for >3 years, and 4 of these patients underwent mild NAr substitution fluctuations (<20%). One patient developed virological breakthrough while bearing single, double, and triple (rtL180 M, rtM204 V, rtS202G) substitutions. In addition to the common substitutions, unknown amino acid substitutions, such as rtL145 M/S, rtF151Y/L, rtR153Q, rtI224 V, rtN248H, rtS223A, rtS256C, need to be further verified. NAr substitutions are observed at frequencies of 0.10% to 6.7% before therapy. Long-term ETV therapy generally results in virological responses, as long as the proportion of resistance mutations remains at a relatively low level. Genotypic resistance to ETV is detected in all PVRs receiving long-term ETV therapy.
authors.affiliation: From the Department of Infectious Disease, Peking University First Hospital, No.8 Xishiku Street, Xicheng District, Beijing, China.
authors.forename: Xia-Xia
authors.initials: XX
authors.lastname: Zhang
authors.forename: Min-Ran
authors.initials: MR
authors.lastname: Li
authors.forename: Ying
authors.initials: Y
authors.lastname: Cao
authors.forename: Ren-Wen
authors.initials: RW
authors.lastname: Zhang
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Fang
authors.initials: F
authors.lastname: Li
authors.forename: Hong-Li
authors.initials: HL
authors.lastname: Xi
authors.forename: Xiao-Yuan
authors.initials: XY
authors.lastname: Xu
mesh_terms: D000328:Adult; D000998:Antiviral Agents / Q000627:therapeutic use*; D004252:DNA Mutational Analysis / Q000379:methods; D004279:DNA, Viral / Q000032:analysis* / Q000097:blood; D024882:Drug Resistance, Viral / Q000235:genetics*; D005260:Female; D005838:Genotype; D006147:Guanine / Q000031:analogs & derivatives* / Q000627:therapeutic use; D006515:Hepatitis B virus / Q000235:genetics*; D019694:Hepatitis B, Chronic / Q000188:drug therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D000998:Antiviral Agents; D004279:DNA, Viral; C413685:entecavir; D006147:Guanine
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