Identification And Mapping Of Epitopes Of Infectious Bursal Disease Virus VP2 And VP3 Proteins

The epitopes of IBDV VP3 were screened by phage display. Four monoclonal antibodies against VP3 of IBDV (VP3-3F, VP3-7B, VP3-7C and VP3-10E) were used to screen for binding peptides from 15-mer phage random peptide library. After three rounds of panning (absorption-elution-amplification), 8 15-mer phage peptides were determined as mimotopes of IBDV. The reaction of mimotopes with McAbs in ELISA can be competitively inhibited by VP3 protein.In order to further study the epitopes structure of IBDV VP3, 17 partially overlapping or consecutive peptides (P1 -P17) spanning VP3 were expressed for epitopes screening by Pepscan. Finally, two linear epitopes of VP3,109-119aa (864-874aa of polyprotein) and 177-190aa (932-945aa of polyprotein), were identified. Compared with many IBDV strains, the epitopes were totally homologous in serotype-1 IBDV (except variant E) and serotype-â…¡IBDV, so they are conservative group-specific epitopes. Both peptides of the two epitopes have good immunogenicity and reactionogenicity. They could induce special antibodies in BALB/c mice while they could react with IBDV chicken positive serum and IBDV VP3 mice positive serum.Also, the epitopes of IBDV VP2 were identified by Pepscan. A new linear epitope of VP2,187-199aa, which was vicinal to the hypervariable region, was identified. Compared with many IBDV strains, the epitope was totally homologous in serotype-I IBDV, so it was conservative serotype-specific epitope..This study is not only important for further understanding the structure of IBDV VP2 and VP3 but also useful for designing the diagnostic reagent and vaccine.