北京地区猫杯状病毒的分离鉴定及VP1基因序列分析

Isolation and Identification of Feline Calicivirus BJH13 Strain and Sequence Analysis of VP1 Gene

为了解猫杯状病毒(FCV)新流行毒株的流行情况、变异特点及致病性,通过收集2016-2022年4月北京地区多家宠物医院就诊疑似感染FCV的猫眼、鼻、咽拭子进行RT-PCR检测和分离培养,对分离到的5株FCV进行病毒含量测定、VP1基因序列分析,并对其中1株进行致病性试验。结果显示,2018-2022年4月阳性率分别为36.98%、34.30%、41.33%、40.46%和34.39%,总阳性率为37.93%。5株FCV分离株VP1基因核苷酸和氨基酸同源性分别为74.1%~85.4%和83.6%~91.0%;5株FCV分离株与国内疫苗株255株核苷酸和氨基酸同源性分别为74.8%~84.5%和83.7%~91.6%;与国内疫苗株255株、国外疫苗株F9株在不同的小分支上。致病性试验结果显示,猫感染BJH13株FCV后出现精神沉郁、食欲减退、体温升高、体重下降、眼鼻分泌物增多和舌泛红、溃疡等典型感染FCV临床症状;FCV感染猫的舌和肺脏组织病理切片结果显示,FCV侵染猫舌和肺脏并呈典型感染FCV病理特征。以上结果表明,FCV阳性率高;分离株BJH13株致病力强;FCV VP1基因序列变异大,与目前临床使用的疫苗株255、F9株VP1基因存在明显差异,存在疫苗免疫失败的风险。这对现阶段FCV防控带来了巨大挑战,同时为今后的疫苗研发提供了候选毒株和科学依据。

To investigate the prevalence,variation characteristics and pathogenicity of a new epidemic strain of feline calicivirus(FCV),in this study,RT-PCR detection and virus isolation and culture were performed using nasopharyngeal swab samples collected from cats'eyes with suspected FCV infection from several pet hospitals in Beijing from 2016 to April 2022.5 isolates were confirmed.The virus content of 5 isolated FCV strains was determined,the VP1 gene sequence was analyzed,and the pathogenicity of one strain was tested.The positive rates of FCV from 2018 to April 2022 were 36.98%,34.30%,41.33%,40.46%and 34.39%,respectively,and the total positive rate was 37.93%.The homologies of VP1 gene and its coding product among 5 FCV strains were 74.1%-85.4%and 83.6%-91.0%,respectively.The homologies of nucleotide and amino acid between the FCV isolates and vaccine strain 255 were 74.8%-84.5%and 83.7%-91.6%,respectively.The results of pathogenicity test demonstrated that cats infected with BJH13 strain showed typical clinical symptoms of FCV infection,such as depression,loss of appetite,increased body temperature,weight loss,increased eye and nose secretions,red and ulcer tongue.The histopathological results demonstrated that the tongue and lung tissues of FCV-infected cats showed typical pathological characteristics of FCV infection.The total results showed that the positive rate of FCV was high.BJH13 strain was more virulent.The VP1 gene sequence of FCV BJH13 strain is significantly different from that of the vaccine strain 255 and F9 used clinically,which maybe a risk of vaccine failure and a great challenge to current prevention and control of FCV infection.In summary,the results provide scientific basis and new candidate strains for future vaccine research and development.