Molecular Evolution of the Capsid Gene in Norovirus Genogroup I

• DOI: 10.1038/srep13806
• Publication Date: 2015-09-04T09:03:32Z
• Authors: Miho Kobayashi; Shima Yoshizumi; Sayaka Kogawa; Tomoko Takahashi; Yo Ueki; Michiyo Shinohara; Fuminori Mizukoshi; Hiroyuki Tsukagoshi; Yoshiko Sasaki; Rieko Suzuki; Hideaki Shimizu; Akira Iwakiri; Nobuhiko Okabe; Komei Shirabe; Hiroto Shinomiya; Kunihisa Kozawa; Hideki Kusunoki; Akihide Ryo; Makoto Kuroda; Kazuhiko Katayama; Hirokazu Kimura
• Keywords: 0301 basic medicine; Base Sequence; Genes, Viral; Molecular Sequence Data; Norovirus; Genetic Variation; Article; 3. Good health; Evolution, Molecular; 03 medical and health sciences; Capsid Proteins; Amino Acid Sequence; Selection, Genetic

AbstractWe studied the molecular evolution of the capsid gene in all genotypes (genotypes 1–9) of human norovirus (NoV) genogroup I. The evolutionary time scale and rate were estimated by the Bayesian Markov chain Monte Carlo (MCMC) method. We also performed selective pressure analysis and B-cell linear epitope prediction in the deduced NoV GI capsid protein. Furthermore, we analysed the effective population size of the virus using Bayesian skyline plot (BSP) analysis. A phylogenetic tree by MCMC showed that NoV GI diverged from the common ancestor of NoV GII, GIII and GIV approximately 2,800 years ago with rapid evolution (about 10−3 substitutions/site/year). Some positive selection sites and over 400 negative selection sites were estimated in the deduced capsid protein. Many epitopes were estimated in the deduced virus capsid proteins. An epitope of GI.1 may be associated with histo-blood group antigen binding sites (Ser377, Pro378 and Ser380). Moreover, BSP suggested that the adaptation of NoV GI strains to humans was affected by natural selection. The results suggested that NoV GI strains evolved rapidly and date back to many years ago. Additionally, the virus may have undergone locally affected natural selection in the host resulting in its adaptation to humans.