Molecular Evolution of Classic Human Astrovirus, as Revealed by the Analysis of the Capsid Protein Gene.

Zhou Zhou,Wang Wang

doi:10.3390/v11080707

Abstract

Classic human astroviruses (HAstV) are major global viral agents for gastroenteritis, but the molecular characteristics of classic HAstVs are not well understood. Here, we presented the molecular evolution of all classic HAstV serotypes by the analysis of the capsid protein sequences. Our results show that classic HAstVs can be divided into four groups with the most recent common ancestor (TMRCA) of 749. The overall evolutionary rate of classic HAstVs on the capsid gene was 4.509 × 10−4 substitutions/site/year, and most of the serotypes present a clock-like evolution with an amino acid accumulation of mutations over time. The mean effective population size of classic HAstVs is in a downward trend, and some positive and more than 500 negative selection sites were determined. Taken together, these results reveal that classic HAstVs evolve at the intra-serotype level with high genetic heterogeneity and are driven by strong purifying selection. Long-term surveillance of classic HAstVs are needed to enrich the genomic data for further analysis.

Highlights

Astroviruses are non-enveloped, positive sense, single-stranded RNA viruses [1]
After excluding the possible recombination sequences determined by Recombination Detection Program (RDP) 4.5.6, a total of 116 complete capsid sequences of classic human astroviruses (HAstV) were retrieved from the GenBank database and analyzed for molecular evolution in this study
The molecular evolution of classic HAstVs has not been discussed in detail

Summary

Introduction

Astroviruses are non-enveloped, positive sense, single-stranded RNA viruses [1]. Their genome is 6.8–7.9 kb in length and consists of three open reading frames (ORFs), designated ORF1a, ORF1b, and ORF2. ORF1a and ORF1b, at the 50 end of the genome, encode nonstructural proteins, including the RNA-dependent RNA polymerase (RdRp), while ORF2, at the 30 end, encodes the capsid protein precursor [2]. Astroviruses are classified into the genera Mamastrovirus and Avastrovirus [3] and can infect various hosts from birds to mammals, including humans [4]. Human astroviruses (HAstVs) were first recognized in children stool samples with diarrhea in 1975 [5]. HAstVs have been the well-established viral agents of gastroenteritis globally, and the number of astrovirus-related publications increase steadily [6]

Methods

Results

Conclusion