Comparison of different sites in recombinant Marek's disease virus for the expression of green fluorescent protein.

Marek's disease virus (MDV) is a preferred vector for recombinant vaccine construction, and insertion site is the main factor influencing foreign gene expression and vaccine efficacy. In this study, recombinant MDVs inserted with the enhanced green fluorescent protein (eGFP) gene at different sites in its genome were generated from overlapping fosmid DNAs and the eGFP expression was compared. The results showed that the eGFP expression levels from the sites in the unique long (UL) region (within UL41, between UL45 and UL46, and between UL55 and LORF10) were comparable, which were significantly higher than those from the sites in the unique short (US) region (US2 and US10), and the eGFP expression level from US2 was significantly higher than that from US10. The identification and comparison of the insertion sites in MDV genome could help elevate the protection efficacy of the recombinant MDVs expressing desired antigens.