College of Animal & Veterinary Sciences, Southwest Minzu University, Chengdu 610041, China.
Key Laboratory of Ministry of Education and Sichuan Province for Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Utilization, Southwest Minzu University, Chengdu 610041, China.
Viruses. 2021 Sep 12;13(9):1812. doi: 10.3390/v13091812.
Feline calicivirus (FCV) is an important pathogen of cats that has two genogroups (GI and GII). To investigate the prevalence and molecular characteristics of FCVs in southwestern China, 162 nasal swab samples were collected from cats in animal shelters and pet hospitals. In total, 38 of the clinical samples (23.46%) were identified as FCV positive using nested RT-PCR. Phylogenetic analyses using 10 capsid protein VP1 sequences revealed that 8 GI and 2 GII strains formed two independent clusters. Additionally, three separated FCVs that were not clustered phylogenetically (two GI and one GII strains) were successfully isolated from clinical samples and their full-length genomes were obtained. Phylogenetic and recombinant analyses of a GI FCV revealed genomic breakpoints in ORF1 and ORF2 regions with evidence for recombinant events between GI sub-genogroups, which is reported in China for the first time. Furthermore, sera obtained from mice immunized independently with the three FCV isolates and a commercial vaccine were used to evaluate the cross-reactivity of neutralizing antibodies. The three separate FCVs were neutralized by each other at a 1:19 to 1:775 titer range, whereas the triple-inactivated vaccine was at a titer of 1:16, which suggested that different genogroup/sub-genogroup FCV strains exhibit significantly different titers of neutralizing antibodies, including the commercial FCV vaccine. Thus, our study revealed the genetic diversity and complex cross-reactivity levels of FCVs in southwestern China, which provides new insights for application in vaccination strategies.
猫杯状病毒（FCV）是一种重要的猫科病原体，具有两个基因组群（GI 和 GII）。为了调查中国西南部 FCV 的流行情况和分子特征，从动物收容所和宠物医院的猫中采集了 162 份鼻腔拭子样本。使用巢式 RT-PCR 共鉴定出 38 份临床样本（23.46%）为 FCV 阳性。使用 10 个衣壳蛋白 VP1 序列进行系统进化分析表明，8 个 GI 和 2 个 GII 株形成了两个独立的聚类。此外，从临床样本中成功分离出 3 株未聚类的 FCV（2 株 GI 和 1 株 GII 株），并获得了它们的全长基因组。GI FCV 的系统进化和重组分析显示，ORF1 和 ORF2 区域存在基因组断点，证据表明 GI 亚基因组之间存在重组事件，这在中国尚属首次报道。此外，用从三个 FCV 分离株和一种商业疫苗单独免疫的小鼠的血清来评估中和抗体的交叉反应性。三个独立的 FCV 在 1:19 到 1:775 的滴度范围内相互中和，而三重灭活疫苗的滴度为 1:16，这表明不同的基因组群/亚基因组 FCV 株表现出明显不同的中和抗体滴度，包括商业 FCV 疫苗。因此，我们的研究揭示了中国西南部 FCV 的遗传多样性和复杂的交叉反应水平，为疫苗接种策略的应用提供了新的见解。
