Figure 1.

Scheme of rNDV-IBV-T/B construction. (A) The open reading frame (ORF) of the IBV S1 T/B multi-epitope cassette gene was amplified from the plasmid pV-S1B+S1T. The cassette contained the Kozak sequence, three neutralizing epitopes (P1–P3), four BF2-restricted T cell epitopes (P8, P9, P18, P19), and was linked with flexible amino acids. (B) The multi-epitope cassette ORF was inserted into the pBR-LS vector in the noncoding region downstream of the M gene using the In-Fusion PCR cloning kit, resulting in the pNDV-IBV-T/B clone. The T7 promoter is indicated by a bold black box. HDVRz represents the site of the hepatitis delta virus ribozyme sequence. (C) Agarose gel electrophoresis after 20 passages of rNDV-IBV-T/B via RT-PCR; the amplified bands were all identical.