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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Endemic Poultry Viral Diseases Research » Research » Publications at this Location » Publication #388264

Research Project: Genetic and Biological Determinants of Avian Herpesviruses Pathogenicity, Transmission, and Evolution to Inform the Development of Effective Control Strategies

Location: Endemic Poultry Viral Diseases Research

Title: Characterization of Md5-BAC-REV-LTR virus as Marek's disease vaccine in commercial meat type chickens: protection and immunosuppression

item ELLINGTON, C - North Carolina State University
item CORTES, A.L. - North Carolina State University
item FAIZ, N.M. - Universiti Putra Malaysia
item Mays, Jody
item FADLY, ALY - US Department Of Agriculture (USDA)
item SILVA, ROBERT - US Department Of Agriculture (USDA)
item GIMENO, ISABEL - North Carolina State University

Submitted to: Avian Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2021
Publication Date: 10/11/2021
Citation: Ellington, C., Cortes, A., Faiz, N., Mays, J.K., Fadly, A., Silva, R.F., Gimeno, I.M. 2021. Characterization of Md5-BAC-REV-LTR virus as Marek's disease vaccine in commercial meat type chickens: protection and immunosuppression. Avian Pathology.

Interpretive Summary: Although, Marek's disease (MD) has been controlled by vaccination since the late 60's, MD still remains one of the major concerns to the poultry industry since, even with proper methods of control, it is reported to cost the poultry industry over 1 billion USD annually. MD viruses (MDV) have evolved over the last 50 years with newly emergent MDV not only capable of breaking vaccine immunity but also capable of overcoming genetic resistance to the disease. Novel methods of control have been developed in order to protect the poultry industry against newly emergent MDV strains. One recombinant virus, Md5-BAC-REV-LTR, was evaluated for its protective efficacy in meat type chickens. The Md5-BAC-REV-LTR virus did not induce immunosuppresion in inoculated meat type chickens and was capable of protecting meat type chickens against a very virulent plus (vv+) MDV strain. The Md5-BAC-REV-LTR virus shows potential as a MD vaccine against early challenge with vv+ MDV.

Technical Abstract: Md5-BAC-REV-LTR is a recombinant Marek’s Disease virus (MDV) that results from insertion of the long terminal repeat (LTR) of reticuloendotheliosis virus (REV) into the genome of the very virulent MDV strain rMd5. It has been shown that Md5-BAC-REV-LTR does not induce tumors and confers high protection against challenge with MDV in 15X7 chickens. The objective of the present study was to evaluate the protection and safety (oncogenicity and immunosuppression) of Md5-BAC-REV-LTR in commercial meat type chickens bearing maternal antibodies against MDV. Our results show that subcutaneous administration of Md5-BAC-REV-LTR at day of age conferred high protection (protection index PI= 84.2) against an early challenge (1 day) with vv+MDV 648A strain. Comparing with other MD serotype 1 vaccine, levels of protection conferred with Md5-BAC-REV-LTR was much higher than those provided by a commercial CVI988 (PI= 12.4) and similar to those achieved by Md5-BAC'meq (PI = 92.4). Furthermore, Md5-BAC-REV-LTR did not induce either tumors or immunosuppression in this study. Immunosuppression was evaluated by the relative lymphoid organ weights as well as by the ability of the vaccine to induce late-MDV-induced immunosuppression associated with reactivation of the virus. This study shows that Md5-BAC-REV-LTR has the potential to be used as a MD vaccine and is highly protective against early challenge with vv+MDV.