Isolation, Molecular Characterization, and Pathogenicity Evaluation of a Genotype GI Feline Calicivirus with an Attenuated Phenotype

Feline calicivirus (FCV) is a highly heterogeneous pathogen and a primary cause of feline upper respiratory tract disease, necessitating continuous surveillance to track its evolutionary dynamics. In this study, a novel FCV strain, designated HN/ZZ/2025, was isolated from a cat trading market in Zhengzhou, China, and phylogenetically assigned to genotype GI. Comprehensive biological characterization using CRFK, F81, and Fc3Tg cell lines revealed efficient replication kinetics and typical calicivirus morphology, while genomic analysis identified distinct amino acid substitutions within the hypervariable E region of the VP1 capsid protein. Experimental feline infection induced characteristic clinical symptoms, including pyrexia, weight loss, and oral ulceration, accompanied by persistent viral shedding and systemic dissemination to the kidneys, spleen, and respiratory tract; however, the lack of mortality confirms an attenuated, low-pathogenicity profile compared to virulent systemic FCV variants. These findings offer critical insights into the molecular epidemiology, tissue tropism, and host–virus interactions of circulating FCV strains, providing a robust framework for improving diagnostic surveillance and future vaccine development strategies.猫杯状病毒（Feline calicivirus, FCV）是一种高度异质性病原体，也是引发猫上呼吸道疾病的主要病原，亟需开展持续监测以追踪其进化动态。本研究从中国郑州一处猫咪交易市场分离得到一株新型FCV毒株，命名为HN/ZZ/2025，经系统发育分析将其归类为GI基因型。利用CRFK、F81及Fc3Tg细胞系开展的全面生物学特性鉴定结果显示，该毒株具有高效的复制动力学特性，并呈现典型的杯状病毒形态；基因组分析进一步发现，其VP1衣壳蛋白的高变E区存在独特的氨基酸替换。人工感染猫实验引发了典型临床症状，包括发热、体重减轻及口腔溃疡，同时伴随持续的病毒排毒现象，并可向肾脏、脾脏及呼吸道等组织发生全身性播散；但未出现死亡病例，表明相较于强毒系统性FCV变异株，该毒株为减毒低致病性株。本研究结果为解析当前流行FCV毒株的分子流行病学、组织嗜性及宿主-病毒互作机制提供了重要见解，同时为优化诊断监测方案及未来疫苗开发策略构建了坚实的研究框架。