FIG 5.

Recombinant IBDV/1FLAG maintains the parental antigenicity. (A) Transmission electron microscopy analysis of the morphology of IBDV/1FLAG (i) and IBDV/WT (ii); scale bars = 100 nm. (B) Schedule for comparison of the viral antigenicity between IBDV/1FLAG and IBDV/WT. (C and D) The neutralizing antibody levels in the serum of chickens (5 in each group) inoculated with DMEM (0.2 ml each), IBDV/WT (10⁴ PFU each), or IBDV/1FLAG (10⁴ PFU each) were tested at 0, 7, 14, and 21 days postinoculation, and the curve was plotted based on the ELISA results (C). Then, all the chickens were challenged by intranasal dropping of IBDV BC6/85 (2 × 10⁴ EID₅₀ each) at 21 days postinoculation of DMEM, IBDV/WT, or IBDV/1FLAG, and the survival curves were generated by daily observing the mortality for 10 days according to the method of Kaplan-Meier (D).