In Vitro Replication of Recombinant Marek’S Disease Viruses Constructed from Field Strains Lacking Meq and Vtr Oncogenes

The study describes construction of five recombinant very virulent (vv) and very virulent plus (vv+) strains lacking meq and viral telomerase (vTR). Deletion of both copies of meq and vTR was achieved by Red E/T recombination in GS1783 E. coli cells. The constructed bacterial artificial chromosome (BAC) clones reconstituted in chicken embryo fibroblasts were examined by immunofluorescence assay to compare the features of recombinant strains with wild-type viruses. The results demonstrated that recombinant BAC strains caused slightly reduced cytophatic effect and decreased level of the fluorescence obtained from the monoclonal antibody in comparison to the parental viruses. Generation of recombinant BAC clones may provide more detailed information on the function of Marek's disease virus oncogenes and the potential use of recombinants for the preparation of the new vaccine against Marek’s disease.