Construction of recombinant Marek's disease virus co-expressing σB and σC of avian reoviruses

Avian reoviruses (ARVs) cause viral arthritis or tenosynovitis, resulting in poor weight gain and increased feed conversion ratios in chickens. In this study, we generated three Marek's disease virus (MDV) recombinants, namely, rMDV-ARV-sigma B, rMDV-ARV-sigma C, and rMDV-ARV-sigma B + C, expressing ARV sigma B, sigma C, and both sigma B and sigma C, respectively. In rMDV-ARV-sigma B and rMDV-ARV-sigma C, the sigma B or sigma C gene was inserted into the US2 gene of MDV vaccine strain 814 using a fosmid-based rescue system. In rMDV-ARV-sigma B + C, the sigma B and sigma C genes were cloned into different expression cassettes, which were co-inserted into the US2 gene of the MDV 814 strain. In infected chicken embryo fibroblasts (CEFs), the recombinant virus rMDV-ARV-sigma B expressed sigma B, rMDV-ARV-sigma C expressed sigma C, and the rMDV-ARV-sigma B + C virus simultaneously expressed sigma B and sigma C. These recombinant viruses exhibited growth kinetics in CEFs similar to those of the parent MDV, and the inserted genes were stably maintained and expressed in the recombinant MDVs after 20 passages in cell cultures. These recombinant MDVs expressing sigma B and sigma C will provide potential vaccines against ARV infection in chickens.