This study investigated a suspected Feline calicivirus (FCV) outbreak at a veterinary facility in Zhengzhou, Henan Province, China. RT-PCR analysis confirmed the FCV presence, with subsequent CRFK cell culture propagation leading to the isolation and characterization of strain ZZ202306. Immunofluorescence and Western blot analyses validated the specificity of monoclonal antibodies targeting the FCV VP1 capsid protein. Transmission electron microscopy revealed non-enveloped virions of ~40 nm in diameter, exhibiting typical caliciviral architecture. Viral replication kinetics demonstrated exponential growth between 6 and 18 h post-inoculation, reaching a peak titer of 10^7.96 TCID₅₀/0.1 mL. Genomic sequencing coupled with phylogenetic reconstruction of the VP1 gene revealed a close genetic relation to domestic Chinese strains and international variants, while maintaining distinct evolutionary divergence from other calicivirus genera.

The outbreak of pseudorabies in China, caused by more virulent pseudorabies virus (PRV) than the classical strains, has led to considerable economic losses. In this study, PRV strain HNXY was isolated from the Henan province of China in 2015 from the pig farm with severe reproductive failure in sows and a high mortality in piglets. The 50% tissue culture infectious doses (TCID₅₀) of HNXY in Vero cells were examined to be 10^6.5/mL, and the neutralisation titer against Bartha-K61 was significantly higher than against HNXY when tested with the serum from Bartha-K61 vaccinated pigs. The 50% lethal doses (LD₅₀) of HNXY to six-week-old BALB/c mice and two-month-old PRV-free pigs were both 10^2.3 TCID₅₀. HNXY was classified as genotype II, and numerous amino acid variations were found in gB, gE, gC, gD, TK, and RR1 proteins, compared with PRV from other countries or those prevalent in China before 2012. The attenuated rHNXY-∆TK/∆gE was further constructed, which presented significantly smaller plaques than HNXY, as well as the similar growth kinetics. rHNXY-∆TK/∆gE was confirmed to be non-pathogenic to six-week-old BALB/c mice and zero-day-old piglets. This study isolated updated PRV promising to develop into a new vaccine candidate.

Feline panleukopenia (FP) is a highly fatal disease in cats caused by feline panleukopenia virus (FPV). The viral capsid protein VP2 determines immunogenicity and host range. We isolated an FPV strain, ZZ202501, and generated four monoclonal antibodies (mAbs) against VP2 by immunizing mice with purified virus and screening the resulting hybridomas on recombinant VP2 expressed in Escherichia coli, a strategy that biases selection toward linear denaturation-resistant epitopes. One mAb, 4D10, bound a linear denaturation-resistant epitope and gave the highest signal-to-noise ratio among the 16 capture and detection combinations tested, which allowed it to serve as both capture and detection antibody in a double-antibody sandwich ELISA (DAS-ELISA). The assay detected 10^1.67 TCID₅₀/0.1 mL of virus and did not cross-react with feline calicivirus or feline herpesvirus. Across 136 clinical samples, it showed complete agreement with a conventional PCR assay. Using mAb 4D10, we also followed the intracellular distribution of the total VP2 pool during infection. VP2 underwent a time-dependent cytoplasmic-to-nuclear redistribution that was blocked by nocodazole, an inhibitor of microtubule polymerization, and microtubule disruption reduced progeny virus titer by more than 100-fold without detectable cytotoxicity. These data indicate that microtubule-dependent trafficking contributes to efficient FPV replication. The study provides an analytically characterized DAS-ELISA for FPV antigen detection, together with evidence linking cytoskeletal transport to viral propagation, and illustrates why the choice between linear and conformational epitopes matters in assay design.