Development and evaluation of a cell-based vaccine expressing VP2 for feline panleukopenia control

Feline panleukopenia virus (FPV) is a highly contagious pathogen that can cause severe disease, particularly in young kittens. We developed a proof-of-concept antigen-delivery strategy using adipose-derived mesenchymal stem cells (ADSCs) engineered to express and secrete FPV VP2 protein. Lentiviral transduction achieved stable VP2 expression without measurably impairing ADSCs proliferation or migration under the conditions tested. In vivo imaging in mice showed that engineered ADSCs remained detectable at the injection site for approximately 21 days. In mice, ADSC-VP2 administration induced FPV-specific IgG, neutralizing antibody responses, lymphocyte proliferation, and cytokine changes. In five volunteer cats vaccinated on days 0, 21, and 42, FPV-specific antibody titers and PRNT 50 activity remained detectable through 180 days. PBMC assays showed stimulation-index and cytokine responses after in vitro restimulation with VP2 or inactivated FPV, and immune sera qualitatively inhibited FPV-associated cytopathic changes in CRFK cells. Longitudinal complete blood counts and serum biochemical measurements showed no overt clinically relevant abnormalities during the 180-day observation period. These findings support ADSC-VP2 as a proof-of-concept cell-based antigen-delivery platform, protective efficacy remains to be established in controlled FPV challenge studies.