Therapeutic efficacy of a chimeric neutralizing antibody targeting feline parvovirus

Feline panleukopenia (FPL), an infectious disease attributed to the feline parvovirus (FPV), poses a substantial threat to feline well-being. Although vaccines against FPV are available, effective treatments such as monoclonal antibodies (mAbs) are still needed. In this study, VP2-specific mAbs were screened from rabbits and subsequently reconstructed as rabbit-feline chimeric mAbs. Among them, f40A specifically bound to VP2 with high affinity (K_D = 1.63 × 10^-9 M) and efficiently neutralized FPV in vitro. Cats treated with 2 mg/kg f40A after FPV-SD2018 challenge survived without clinical illness. Additionally, the leukocyte counts, diarrhoea and body temperature of f40A-treated cats rapidly restored to physiological levels, suggesting f40A effectively protected cats from FPV-SD2018 pathogenesis. More importantly, the viral shedding in f40A-treated group was significantly lower than that in the placebo group, indicating f40A efficiently neutralized FPV-SD2018 in vivo. Lastly, preliminary tolerability assessment of f40A was examined in healthy cats by administering 4 mg/kg mAb. No adverse local reactions were observed. All cats maintained normal body temperature and continuously grew weight for 14 days, indicating f40A was safe in cats. In conclusion, these findings present an efficacious and safe mAb for early therapeutic against FPV infection, which is a promising candidate for FPL in clinics.