Generation and Immunogenicity of Virus-like Particles Based on the Capsid Protein of a Chinese Epidemic Strain of Feline Panleukopenia Virus.

Feline panleukopenia (FPL), caused by the feline panleukopenia virus (FPLV), is a severe and highly contagious viral disease with high morbidity and mortality. Vaccination remains the gold standard for preventing and controlling this debilitating condition. The viral protein VP2 serves as the major immunogen of FPLV and represents the key target antigen in the development of a novel FPLV vaccine. Virus-like particle (VLP)-based vaccines have emerged as next-generation vaccine candidates due to their high immunogenicity and safe profile. In this study, a baculovirus expression vector system (BEVS) was employed to generate FPLV-VLPs through recombinant expression of the VP2 protein of a Chinese epidemic strain (Ala91Ser, Ile101Thr) of FPLV. The resulting FPLV-VLPs demonstrated markedly enhanced antigenicity and hemagglutination activity, achieving a hemagglutination titer of up to 1:2¹⁶. Following vaccination, immunized cats developed high titers of anti-FPLV hemagglutination inhibition (HI) antibodies (1:2¹⁶) and exhibited 100% protection against challenge with a virulent epidemic FPLV variant (Ala91Ser, Ile101Thr). These findings demonstrate that FPLV-VLPs hold strong potential as candidates for a novel subunit vaccine against FPLV infection.