Molecular and evolutionary characterization of feline panleukopenia virus using bioinformatics tools

Feline panleukopenia virus (FPV) is a highly contagious parvovirus that continues to cause significant disease in domestic and wild felids worldwide. Although historically considered genetically stable and effectively controlled by vaccination, recent molecular studies have expanded the available genomic data, prompting renewed interest in its evolutionary dynamics. Here, we conducted a global bioinformatic analysis of FPV genetic diversity, evolution and antigenic constraints using 446 complete VP2 sequences collected between 1967 and 2023. Phylogenetic analysis identified nine major clades (A–I) with distinct geographic and temporal patterns, while vaccine strains consistently clustered within a single clade. Overall VP2 variability was low, with most amino acid substitutions occurring sporadically and only two sites exceeding 5% frequency. Selective pressure analysis detected a single codon under weak positive selection, consistent with strong purifying selection acting on the capsid. Molecular clock and Bayesian skyline analyses indicated a slow evolutionary rate and a relatively stable effective population size over time. Structural and epitope analyses showed that residues with higher predicted antigenicity were significantly more conserved, and all predicted high-affinity cytotoxic T-lymphocyte epitopes remained unchanged across sequences. These results indicate that FPV evolution is highly constrained and that no evidence of emerging antigenic variants of concern is currently detectable, supporting the continued effectiveness of existing vaccines and the importance of ongoing molecular surveillance.