Extracellular Vesicles Mediate Feline Panleukopenia Virus to Suppress IFN-ω-Induced Antiviral Cytokine Expression

The immune escape and cross-host transmission mechanisms of feline panleukopenia virus (FPV) remain poorly elucidated, and extracellular vesicles (EVs) play critical regulatory roles in viral infection progression. To explore the molecular mechanism by which EVs mediate FPV infection, proliferation, and immune escape, EVs were isolated from FPV-infected F81 cells and peripheral blood of FPV-affected cats in this study. CD63 antibody-based magnetic bead immunoaffinity chromatography was applied for EV purification. Multiple approaches, including transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), Western blotting (WB), and quantitative real-time PCR (qPCR), were used for vesicle characterization. Cell infection assays, neutralizing antibody blockade assays, and interferon (IFN) intervention assays were performed to clarify the biological functions of FPV-derived EVs. The results showed that FPV-positive EVs with typical morphology, particle size, and biomarker characteristics were successfully isolated and purified, and the purification strategy markedly reduced free virus contamination. Functional experiments verified that FPV-infected cell-derived EVs could be rapidly internalized by host cells, significantly accelerate early FPV proliferation and cytopathic effects, and inhibition of EV secretion efficiently blocked FPV propagation. Moreover, FPV-EVs overcame the host entry restriction of FPV, mediated FPV entry into non-permissive HEK293T cells, and escaped the blockade of neutralizing antibodies. Mechanistically, FPV-EVs potently antagonized IFN-ω-mediated cellular antiviral responses and inhibited the expression of interferon-stimulated genes (ISGs) including ISG15, ISG56, and MX1. This immunosuppressive effect was independent of EV carriers and exhibited broad-spectrum activity in different cell types. Furthermore, EVs derived from the peripheral blood of FPV-infected cats also efficiently mediated FPV infection, assisted viral escape from humoral immunity, and antagonized host IFN-mediated antiviral responses. Collectively, this study indicates that EVs act as a key medium for FPV to achieve efficient proliferation, cross-cell infection, and immune escape, revealing a novel transmission mechanism of FPV, although productive replication and progeny release in the non-permissive human cells were not demonstrated and the potential for host-range expansion remains hypothetical. These findings provide important experimental evidence and theoretical support for improving the pathogenic mechanism of FPV and developing novel prevention and control strategies.