Molecular evolution of the major capsid gene in human Norovirus GII.17

Yibo Zhang, Xiuying Deng, Qiang Chen, Hongxiong Guo


Background: Norovirus genogroup II genotype 17 has been one of the major genotypes causing acute gastroenteritis (AGE) in some countries. The aim of this study is to analyze the characteristics of the major capsid gene of human Norovirus (HuNov) GII.17 isolated globally.
Methods: MCMC phylogenetic tree is constructed using a Bayesian Markov Chain Monte Carlo approach with BEAST v1.8.4 software. The ration of nonsynonymous (dN) to synonymous (dS) substitutions at every codon were calculated online using Datamonkey Adaptive Evolution Server. Similarity of the major capsid gene is analyzed using Simplot software, and its gene distance is calculated using MEGA7.0 software.
Results: All Norovirus GII.17 was classified into two clades, and the most recent common ancestor of GII.17 was around 1984.6 (1926.9–1995.0). The mean evolutionary rate of it was estimated to be 2.31×10−3 substitutions/site/year [95% highest posterior densities (HPDs) 9.40×10−4–3.84×10−3 substitutions/site/year]. Compared with other genotypes of GII, the distance of the major capsid gene is lower while the similarity of it is higher. Three positive selection sites are found.
Conclusions: The common ancestor of GII.17 diverged from the other genotype of GII around (1926.9–1995.0) at a high evolutionary rate, although evolutionary rate of GII.17 is lower than the other genotype of GII. The positive selective sites in the protruding domain of GII.17 capsid gene with a higher divergence may increase the adaptivity of GII.17 living in Human body.