An unusual hepatitis B virus (HBV) variant, assigned provisionally to genotype I, was recently reported, characterized by an anomalous genotyping pattern and putative recombination; however, the natural history of this unusual strain is unknown. This study analyzed longitudinal sera collected over a 9-year period from a patient infected with this variant to investigate the clinical profile and intrahost viral evolution over time. The patient, who had immigrated to Canada in 1998 from Vietnam, was treated with lamivudine in 2000. Approximately 4-5 years following the withdrawal of lamivudine therapy, a genomic "shift" occurred coincident with ALT flares and increasing HBV viral load, resulting in numerous stable nucleotide substitutions within the core coding region, suggesting altered immune control that may provide a selective advantage to the virus. Analysis of quasispecies diversity over time demonstrated further this shift, with two sequence clusters associated with time points either prior to or following relapse observed, including increased diversity among quasispecies prior to relapse. In keeping with the complex nature of genotype I strains, majority population genomes had a mean genetic distance from genotype C of 7.6 +/- 0.1%, although large genomic segments lacked significant homology with any HBV genotype. Further study is needed to understand the evolutionary origin and natural history of infection with this unique HBV variant.
(c) 2010 Wiley-Liss, Inc.