Genomic characterization and pathogenicity of the feline coronavirus (FCoV) type II strain AH2023

Abstract

Feline infectious peritonitis (FIP) is a fatal disease caused by feline coronavirus (FCoV), a member of the Coronaviridae family that comprises two genotypes, FCoV-I and FCoV-II. From the ascitic fluid of a British shorthair cat diagnosed with FIP, we isolated and identified an FCoV strain designated AH2023. Western blotting, RT‒PCR, and transmission electron microscopy were employed for characterization. According to phylogenetic analyses of the full viral genome and the spike, nucleocapsid, and 3C-like protease genes, strain AH2023 consistently fell within the clade of previously reported Chinese FCoV-II strains and exhibited greater evolutionary proximity to transmissible gastroenteritis virus (TGEV) and canine coronavirus (CCoV) than to FCoV-I did. Recombination analysis using SimPlot further revealed strain AH2023 to be a recombinant virus. Strain AH2023 is genetically distinct, carrying four amino acid substitutions in the spike protein. Substitutions at positions 387, 577, and 829 are shared with strains SH2021 and DQ2023, whereas the substitution at position 1375 is shared with strain DF2. Pathogenicity tests in 12‑week‑old cats confirmed the virulence of AH2023. All the cats died between 12 and 18 days post-challenge (dpc) and presented severe intestinal, hepatic, and renal lesions. The virus exhibited broad tissue tropism, with the highest viral load (10⁴ copies/mg) found in the intestine. Fecal shedding began at 7 dpc and reached 10⁴ copies by 10 dpc. These results advance our understanding of FCoV evolution and pathogenesis, especially for type II strains in China, and aid in the development of effective FIP prevention strategies.

Keywords

Feline coronavirus (FCoV) / Isolation and identification / Phylogenetic analysis / Recombinant / Pathogenicity

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Funding

the 111 Project D18007

the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)(PAPD)

RIGHTS & PERMISSIONS

The Author(s)