Molecular Characterization and Cross-Reactivity of Feline Calicivirus Circulating in Southwestern China

Long Zhou,Nengsheng Fu,Jian Huang,Xue Sha,Xin Song,Qun Zhou,Lu Ding,Bin Zhang,Yan Li

doi:10.3390/v13091812

Abstract

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.

Highlights

Feline calicivirus (FCV), which belongs to the family Caliciviridae, genus Vesivirus, is the causative agent of respiratory disease, stomatitis, arthritis, and hemorrhagic-like fever in cats [1]
In China, most FCV strains belong to genogroup II (GII), and they are closely related to Japanese FCV strains [5,16]
The results suggest that various FCV strains from different clusters are simultaneously circulating and spreading in southwestern China

Summary

Introduction

Feline calicivirus (FCV), which belongs to the family Caliciviridae, genus Vesivirus, is the causative agent of respiratory disease, stomatitis, arthritis, and hemorrhagic-like fever in cats [1]. An FCV infection causes apparent or relatively mild oral cavity and upper respiratory tract symptoms [6,7]. In the past decade, virulent mutants of FCV called VS-FCVs, have been identified as the causal agents of severe and acute virulent systemic disease (VSD), resulting in a high persistent fever and high mortality rate in vaccinated cats [10,11]. In accordance with the genetic diversity of the VP1 gene, the global FCVs are classified into two genogroups: genogroup I (GI) and genogroup II (GII) [14]. It is worthy to note that new FCV strains have been constantly emerging in recent years owing to the large degree of viral genetic variation [17,18,19]

Methods

Results

Discussion

Conclusion