Feline Panleukopenia Virus ZZ202303 Strain: Molecular Characterization and Structural Implications of the VP2 Gene Phylogenetic Divergence

Feline panleukopenia virus (FPV), the etiological agent of a highly contagious multispecies disease, demonstrates concerning phylogenetic divergence that compromises vaccine cross-protection. This study aimed to characterize a novel FPV strain through integrated virological and molecular analyses to assess epidemiological implications. From seven clinical specimens obtained from feline hosts with panleukopenia in Henan Province, China, we isolated FPV ZZ202303 using an F81 cell culture coupled with PCR verification, demonstrating potent cytopathic effects (TCID₅₀: 10^-5.72/0.1 mL) and rapid replication kinetics (viral peak at 12-24 h post-infection). Comparative virulence assessments revealed a 1.8- to 2.3-fold greater pathogenicity versus contemporary field strains (2021-2023). Phylogenetic reconstruction based on complete <i>VP2</i> gene sequences positioned FPV ZZ202303 within an emerging clade sharing 97.5-98.2% identity with canine parvovirus strains versus 98.8-99.7% with FPV references, forming a distinct cluster (bootstrap = 94%) diverging from vaccine lineages. Critical structural analysis identified a prevalent I101T mutation (89.13% prevalence) in the <i>VP2</i> capsid protein's antigenic determinant region, with molecular modeling predicting altered surface charge distribution potentially affecting host receptor binding. Our findings substantiate FPV ZZ202303 as an evolutionarily divergent strain exhibiting enhanced virulence and unique genetic signatures that may underlie vaccine evasion mechanisms, providing critical data for updating prophylactic strategies against this economically impactful pathogen.