Development of a cell line system susceptible to infection with vaccine strains of MDV

Despite reliance on the need to continually prepare fresh cultures of chick embryo fibroblasts (CEFs) to make Marek's disease (MD) vaccines, MD vaccin es an the most widely used vaccines in the poultry industry Preparation of CEF's accounts for approximately 40% of the costs associated with producing MD vaccines. A significant reduction in MD vaccine production costs could be realized ifa continuous cell lines were available for MD vaccine product ion. Recently, we reported development and characterization of a cell line system (OCLTM) that supports growth and replication of oncogenic serotype 1 Marek's disease virus (MDV). Here we report development of three cell line systems for production of MD vaccine. These cell lines support the growth and replication of attenuated serotype 1 MDV (CV1-OCTM), serotype 2 MDV (SB 1OCLTM) and serotype 3 MDV (HVT-OCLTM). MDV is maintained in a stable state in the OCLTM cells and the infected cells can be continuously grown. The v accines made from these cell lines are safe and protect White Leghorn chick ens against challenge with very virulent serotype 1 MDV, similar to traditi onal vaccines made from CEF cells. These cell line systems can significantl y reduce the costs associated with MD vaccine production. Furthermore, the increased stability of MDV and the potential for positive selection of reco mbinant MDV suggest that OCLTM will be ideal for production of more effecti ve MDV vaccines using recombinant DNA technology.