# Genetic and Biological Properties of an Epidemic Feline Panleukopenia Virus Strain (Ala91Ser) in China

## TL;DR

A new strain of feline panleukopenia virus in China shows increased virulence and differs from current vaccines, suggesting it could be used to develop a more effective local vaccine.

## Contribution

Identification of a novel FPLV variant with Ala91Ser and Ile101Thr mutations in the VP2 protein and increased virulence in cats.

## Key findings

- FPLV-CC19-02 differs from commercial vaccine strains and the Cu-4 prototype at VP2 positions 91 and 101.
- The virus causes severe clinical symptoms and high mortality in cats, indicating increased virulence.
- The strain demonstrated good immunogenicity in vaccinated cats.

## Abstract

A Chinese epidemic feline panleukopenia virus variant, named FPLV-CC19-02, was isolated from a PCR-positive faecal swab sample in this study. It shows a long distance to from all current commercial vaccine strains (Pfizer®, New York, NY, USA; MSD®, Kenil-worth, NJ, USA; Virbac®, Nice, Alpes-Maritimes, France; Merial®, Paris, France; Nobivac®, Boxmeer, Feldhoven, The Netherlands) in the phylogenetic tree, and differs from the FPLV prototype strain Cu-4 (M38246.1) at the 91st (Ala91Ser) and 101st (Ile101Thr) site within the VP2 protein. Additionally, it exhibits more virulence for host cells and cats. Meanwhile, the vaccination of cats against FPLV infection demonstrated good immunogenicity result in cats. These findings suggest that this variant is a better candidate for the development of a locally produced FPLV vaccine in China.

To genetically characterise an epidemic isolate of feline panleukopenia virus (FPLV) harbouring the Ala91Ser mutation in China, a clinical strain (accession number: OR921195.1), named FPLV-CC19-02, was isolated from a PCR-positive faecal swab sample. Phylogenetic analysis revealed that it is far removed from all current commercial vaccine strains and differs from the FPLV prototype strain Cu-4 (M38246.1), specifically the vaccine strain of Fel-O-Vax® PCT, at positions 91 (Ala91Ser) and 101 (Ile101Thr) within the VP2 protein. This virus can induce the typical cytopathic effect seen in parvovirus infection in feline kidney cells, resulting in severe clinical symptoms in cats, including haematochezia and hyperthermia. Furthermore, infected cats died of virus infection within 5–10 days post-infection (dpi) (100% morbidity and 83% mortality), indicating that FPLV-CC19-02 is a strain with increased virulence. Additionally, it demonstrated good immunogenicity in cats. Overall, these findings may help us to better understand the molecular prevalence of feline panleukopenia virus in cats and provide valuable basic data for the development of effective, locally adapted feline panleukopenia virus vaccines in China.