Tracing hepatitis B virus (HBV) genotype B5 (formerly B6) evolutionary history in the circumpolar Arctic through phylogeographic modelling

• Published in: PeerJ
• Main Authors: Remco Bouckaert, Brenna C. Simons, Henrik Krarup, T. Max Friesen, Carla Osiowy
• Format: Article in Journal/Newspaper
• Language: English
• Published: PeerJ Inc. 2017
• Subjects: Hepatitis B virus; Genotype; Evolution; Arctic; Inuit; Host-pathogen balance; Medicine; R; Biology (General); QH301-705.5; Canada; Greenland; eskimo*; inuit; Thule; Thule culture; Alaska
• Online Access: https://doi.org/10.7717/peerj.3757; https://doaj.org/article/ca3065e9987842bd91e0e0f61be39d8c

Background Indigenous populations of the circumpolar Arctic are considered to be endemically infected (>2% prevalence) with hepatitis B virus (HBV), with subgenotype B5 (formerly B6) unique to these populations. The distinctive properties of HBV/B5, including high nucleotide diversity yet no significant liver disease, suggest virus adaptation through long-term host-pathogen association. Methods To investigate the origin and evolutionary spread of HBV/B5 into the circumpolar Arctic, fifty-seven partial and full genome sequences from Alaska, Canada and Greenland, having known location and sampling dates spanning 40 years, were phylogeographically investigated by Bayesian analysis (BEAST 2) using a reversible-jump-based substitution model and a clock rate estimated at 4.1 × 10−5 substitutions/site/year. Results Following an initial divergence from an Asian viral ancestor approximately 1954 years before present (YBP; 95% highest probability density interval [1188, 2901]), HBV/B5 coalescence occurred almost 1000 years later. Surprisingly, the HBV/B5 ancestor appears to locate first to Greenland in a rapid coastal route progression based on the landscape aware geographic model, with subsequent B5 evolution and spread westward. Bayesian skyline plot analysis demonstrated an HBV/B5 population expansion occurring approximately 400 YBP, coinciding with the disruption of the Neo-Eskimo Thule culture into more heterogeneous and regionally distinct Inuit populations throughout the North American Arctic. Discussion HBV/B5 origin and spread appears to occur coincident with the movement of Neo-Eskimo (Inuit) populations within the past 1000 years, further supporting the hypothesis of HBV/host co-expansion, and illustrating the concept of host-pathogen adaptation and balance.