Additional file 1: Confirmation of recombinant NDVs inserted BRV VP4 or VP6. (A) Schema of constructed recombinant NDV genomes inserted with the BRV VP6 or VP4 gene. (B) indicates viral titer of the rescued viruses grown in embryonated eggs. (C) MDBK cells infected with either rNDV-WT-VP4 or rNDV-2F2HN-VP4 were stained by anti-NDV antiserum (green), BRV antibody (red), and Hoechst 33342 (blue; nuclei). (D) Electrophoresis of the PCR products for the verification of BRV-VP6 and VP4 antigens within the constructed viruses using each primer set as indicated. Arrows indicate the expected size (VP6: 1354 bp and VP4: 2511 bp).