Characterization and immunogenic evaluation of feline calicivirus epidemic strains

The feline calicivirus (FCV) is globally prevalent with regional specificity in its distribution, but the significant differences among strains limit the efficacy of vaccines. Therefore, understanding the prevalence and biological characteristics of FCV holds immense significance in facilitating the development of novel vaccines and targeted pharmaceuticals.

This study aimed to understand the epidemiological status of the FCV in the Shandong region and identify candidate strains for vaccine development.

In this study, 41 FCV strains were obtained from Shandong province in China. Phylogenetic analysis was conducted based on the VP1. The FCV023 strain was selected for pathogenicity and immunogenicity analysis.

Forty-one FCV strains were isolated from cats with a suspected FCV infection in Shandong province. The phylogenetic tree showed that the FCV isolates could be divided into three gene Clusters: Clusters I-III. Clusters I and II have a higher prevalence in Shandong province than Cluster III. The challenge experimental results showed that FCV023 could cause typical upper respiratory infections in cats. The in vitro neutralization assay showed that FCV023 positive serum could produce a neutralizing titer against FCV isolates distributed in different branches of phylogenetic trees.

The FCV detection rate in Shandong Province was 70.69%, significantly higher than in other regions. Phylogenetic analysis suggested that FCV strains exhibit characteristic regional prevalence in Shandong Province. As a representative strain, FCV023 infections can cause typical upper respiratory symptoms in cats. The preliminarily screened FCV023 immune serum showed good neutralizing activity and can be considered a candidate strain for vaccine development.