Monitoring the Emergence of Hepatitis B Virus Polymerase Gene Variants during Lamivudine Therapy in Human Immunodeficiency Virus Coinfected Patients: Performance of Clip™ Sequencing and Line Probe Assay

Sera from 12 patients infected with human immunodeficiency virus and hepatitis B virus (HBV), on lamivudine as part of an antiretroviral therapy, were retrospectively analysed for the presence of HBV polymerase mutations by the line probe assay, INNO-LiPA HBV DR, and by the direct sequencing assay, TRUGENE™ HBV genotyping kit. Results at codons 180, 204 and 207 were compared for 44 samples. Full concordance was observed for 81.4% of the 129 analysed codons. Discordance involved only mixed populations: LiPA detected additional species in 19 codons and TRUGENE in five. Viral breakthrough occurred in seven patients, 12-33 months after lamivudine initiation. In five cases with close sampling available, both assays detected mutations before the rise in viral load, although earlier by LiPA for three patients. The time interval between the first mutant detection and viral escape ranged from 2 to 22 months. Mutations were detected in four of the five remaining patients: 1) at therapy initiation in a primary non-responder; 2) after 37 months, but replication became undetectable after tenofovir introduction; 3) transiently at 6 months by LiPA but treatment was ceased thereafter; 4) after 23 months but replication levels remained low during a 5-year follow-up. Interestingly, TRUGENE sequencing identified on late samples from three patients a variant carrying rtV173L plus rtL180M plus M204V mutations, having the in vitro characteristics of ‘vaccine escape’ mutants. Both assays appear to be valuable tools for the early detection of mutated HBV strains. The detection of genotypic resistance could improve therapeutic decision-making, although clinical or other virological factors may determine the rapidity of the viral breakthrough.