Genetic and structural factors contributing to the dominance and persistence of goose astrovirus type 2

Goose astrovirus (GoAstV) has emerged as a significant pathogen affecting the goose industry in China, with GoAstV-2 becoming the dominant genotype since 2017. This study explored the genetic and structural factors underlying the prevalence of GoAstV-2, focusing on codon usage bias, spike protein variability, and structural stability. Phylogenetic and effective population size analyses revealed that GoAstV-2 underwent rapid expansion between 2017 and 2018, followed by population stabilization. Codon usage analysis indicated that GoAstV-2 exhibited a weaker codon usage bias compared to GoAstV-1, suggesting greater flexibility in synonymous codon usage and potentially enhanced adaptability across host environments. Additionally, the lower codon adaptation index values of GoAstV-2 point to a divergence from the host’s optimal codon usage, which may reduce competition with host tRNA pools and facilitate viral replication. The spike protein of GoAstV-2 demonstrated significantly lower variability than GoAstV-1, as shown by Shannon entropy analysis, indicating greater structural stability. This stability may reduce the need for frequent mutations, allowing GoAstV-2 to persist in host populations without undergoing constant evolution. The lower antigenic variability likely decreases immune-driven selective pressure, contributing to the sustained viral transmission and long-term persistence. These findings provide new insights into the evolutionary advantages of GoAstV-2 and its epidemiological success, which could inform future control strategies aimed at mitigating its impact on poultry populations. Goose astrovirus type 2 (GoAstV-2) became the dominant strain in China post-2017.GoAstV-2 exhibits weaker codon usage bias, enhancing adaptability across hosts.The stability of GoAstV-2 spike protein reduces mutation needs and selective pressure.GoAstV-2 low spike protein variability supports long-term persistence in host populations. Goose astrovirus type 2 (GoAstV-2) became the dominant strain in China post-2017. GoAstV-2 exhibits weaker codon usage bias, enhancing adaptability across hosts. The stability of GoAstV-2 spike protein reduces mutation needs and selective pressure. GoAstV-2 low spike protein variability supports long-term persistence in host populations.

鹅星状病毒（Goose astrovirus, GoAstV）已成为影响中国养鹅产业的重要致病性病原，自2017年以来，鹅星状病毒2型（GoAstV-2）已成为优势基因型。本研究针对GoAstV-2流行的遗传学与结构基础展开探究，重点关注密码子使用偏好性（codon usage bias）、刺突蛋白（spike protein）变异度与结构稳定性。系统发育与有效种群规模分析显示，GoAstV-2在2017至2018年间经历了快速扩张，随后种群趋于稳定。密码子使用分析表明，相较于GoAstV-1，GoAstV-2的密码子使用偏好性更弱，提示其同义密码子使用灵活性更高，跨宿主环境的适应能力或有所增强。此外，GoAstV-2较低的密码子适应指数（codon adaptation index, CAI）值表明其与宿主最优密码子使用模式存在分化，这或可减少与宿主tRNA库的竞争，进而促进病毒复制。经香农熵（Shannon entropy）分析显示，GoAstV-2的刺突蛋白变异度显著低于GoAstV-1，表明其结构稳定性更强。此种稳定性或可降低频繁突变的需求，使得GoAstV-2无需持续进化即可在宿主种群中持续存留。较低的抗原变异度或可降低免疫介导的选择压力，助力病毒实现持续传播与长期存留。本研究结果为GoAstV-2的进化优势及其流行病学层面的成功流行提供了新见解，可为未来制定旨在减轻其对禽群危害的防控策略提供参考。2017年后，鹅星状病毒2型（GoAstV-2）已成为中国境内的优势毒株。GoAstV-2的密码子使用偏好性较弱，提升了其跨宿主适应能力。GoAstV-2刺突蛋白的稳定性降低了其突变需求与选择压力。GoAstV-2刺突蛋白较低的变异度助力其在宿主种群中长期存留。2017年后，鹅星状病毒2型（GoAstV-2）已成为中国境内的优势毒株。GoAstV-2的密码子使用偏好性较弱，提升了其跨宿主适应能力。GoAstV-2刺突蛋白的稳定性降低了其突变需求与选择压力。GoAstV-2刺突蛋白较低的变异度助力其在宿主种群中长期存留。