Preparation Of Feline Panleukopenia Subunit Vaccine And Screening Of VP2 Monoclonal Antibody

Feline panleukopenia is a highly contagious and lethal disease,which has been gained widespread attention for disease control and public health China.However,FP vaccines and diagnostics in China mainly rely on imports currently.Moreover,due to the impact of COVID-19 and Shortages of imported,it is in urgent need of independently developed FP vaccines and diagnostics.VP2 protein is the main capsid protein of FPV and the DNA sequences between different strains are highly conserved.The VLP have immunogenicity,which could induce strong humoral and cellular immunity.Based on this,the VP2 was used as the prototype of FP vaccine in this study,and the single-chain antibody against VP2 was prepared for further study of FP diagnostic tests.In this study,the complete VP2 sequence of the standard FPV strain CU-4 was constructed into the prokaryotic expression plasmid p ET-28 a for expression.It was found that the VP2 protein could self-assemble into VLP.Thereafter,the self-assembled VP2 virus like particle was used as vaccine to immunize animals.After three times of immunization of cats,antibody titer reached 8.0×104.Neutralization assay was carried out using the FPV-myzx strain isolated from positive clinical samples and the serum of immunized animals.It was found that the serum of immunized animals could inhibit the infection of the virus.Afterwards,FPV-myzx was used to challenge the animals.It was found that the 3 immunized animals in the challenge group were survived,which resulted in a protection ratio of 100%.All 3 animals in the challenge group were infected with FPV and died quickly.It is suggested that the FP vaccine based on VP2 virus like particle has good protection efficacy,which lays a foundation for the development of FP vaccine in the future.As the DNA sequences between different strains of FP are highly conserved,VP2 protein can also be used as a good target for pathogen detection in immunological diagnosis.Therefore,the VP2 protein was used as the target antigen and specific antibody was successfully discovered by phage display.The recombinant antibody(VP2Ab)was successfully expressed using HEK293 F cells.The EC50 was 13.97 ng/m L,indicating that the recombinant antibody was active and had good affinity.These results paved way for the development of FP immunological diagnostics.