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Title: A MEQ Deleted Marek's Disease Virus Cloned as a Bacterial Artificial Chromosome is a Highly Efficacious Vaccine

item Silva, Robert
item Dunn, John
item Cheng, Hans
item NIIKURA, MASAHIRO - Simon Fraser University

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2010
Publication Date: 6/1/2010
Citation: Silva, R.F., Dunn, J.R., Cheng, H.H., Niikura, M. 2010. A MEQ-Deleted Marek's Disease Virus Cloned as a Bacterial Artificial Chromosome Is a Highly Efficacious Vaccine. Avian Diseases. 54(2):862-869.

Interpretive Summary: Marek's disease (MD) is a serious disease of poultry, caused by Marek's disease virus (MDV). MD is usually controlled by vaccination. However, MDV is continuing to evolve and new strains are emerging, making effective vaccination more problematic. We used techniques from molecular biology to modify an MDV to be a non-disease causing virus that can also be used as a vaccine to protect chickens from MD. Our vaccine is superior to the best commercially available MD vaccine. Our vaccine was also designed to be able to accommodate the insertion of any other genes. Thus, the vaccine can easily be modified so that it will be a vaccine not only for MD but a vaccine for any of a number of other poultry diseases.

Technical Abstract: The Marek’s disease virus (MDV) MEQ gene is essential for the T-cell lymphocytic infiltration of nerves and other organs seen in chickens with Marek’s disease (MD). In an earlier study, researchers used an overlapping cosmid clone library of MDV and demonstrated that deleting MEQ resulted in an excellent MD vaccine. We deleted both copies of MEQ from a bacterial artificial chromosome clone (BAC) of MDV. The virus, BACdelMEQ, was completely attenuated and did not appear to have any adverse effect on chicken body weight, as measured at eight weeks of age. In two protection studies, BACdelMEQ efficiently protected susceptible chickens from a challenge by MDV strain 686, one of the most virulent MDV strains. In both protection studies, the BACdelMEQ protected chickens significantly better than the best commercial MD vaccine, CVI988/Rispens. Only the protein coding sequences of MEQ were deleted and all upstream and downstream regulatory sequences were left intact. Thus, BACdelMEQ has the potential to be a superior MD vaccine as well as a vector to deliver various foreign genes to poultry.