{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,1]],"date-time":"2026-05-01T22:28:28Z","timestamp":1777674508960,"version":"3.51.4"},"reference-count":35,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2021,12,22]],"date-time":"2021-12-22T00:00:00Z","timestamp":1640131200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Microorganisms"],"abstract":"<jats:p>Marek\u2019s disease (MD) is a ubiquitous disease of domesticated chickens and its etiologic agent is the Gallid alphaherpesvirus 2 (GaHV-2), also known as Marek\u2019s disease virus (MDV). MD is currently controlled by vaccination using live attenuated strains of MDV (e.g., CVI988\/Rispens), non-pathogenic serotypes of MDV (GaHV-3), or non-pathogenic strains of the related Melagrid alphaherpesvirus 1 (MeHV-1). One attractive strategy for the production of new vaccine strains is a recombinant MDV attenuated by the deletion of the major viral oncogene meq. However, meq-deleted variants of MDV cause atrophy of the bursa and thymus in maternal antibody-negative chickens, and the resulting immunosuppression makes them unsuitable. Herein we detail our attempt to mitigate the lymphoid atrophy caused by meq-deleted MDV by further attenuation of the virus through ablation of the viral thymidine kinase (tk) gene. We demonstrate that ablation of the viral tk from the meq-deleted virus rMd5B40\/\u0394meq resulted in a virus attenuated for replication in vitro and which spared chickens from atrophy of the lymphoid organs in vivo. When the rMd5B40\/\u0394meq\/\u0394tk\/GFP was used as a vaccine it was protective against challenge with the vv+MDV strain 686, but the protection was less than that provided by the CVI988\/Rispens vaccine.<\/jats:p>","DOI":"10.3390\/microorganisms10010007","type":"journal-article","created":{"date-parts":[[2021,12,23]],"date-time":"2021-12-23T02:01:19Z","timestamp":1640224879000},"page":"7","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Deletion of the Viral Thymidine Kinase in a Meq-Deleted Recombinant Marek\u2019s Disease Virus Reduces Lymphoid Atrophy but Is Less Protective"],"prefix":"10.3390","volume":"10","author":[{"given":"Steven J.","family":"Conrad","sequence":"first","affiliation":[{"name":"United States Department of Agriculture, Agricultural Research Service, U.S. National Poultry Research Center, Avian Disease and Oncology Laboratory, East Lansing, MI 48823, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7173-391X","authenticated-orcid":false,"given":"Eniope B.","family":"Oluwayinka","sequence":"additional","affiliation":[{"name":"Department of Veterinary Medicine, Federal University of Agriculture Abeokuta, Abeokuta 111101, Nigeria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mohammad","family":"Heidari","sequence":"additional","affiliation":[{"name":"United States Department of Agriculture, Agricultural Research Service, U.S. National Poultry Research Center, Avian Disease and Oncology Laboratory, East Lansing, MI 48823, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jody K.","family":"Mays","sequence":"additional","affiliation":[{"name":"United States Department of Agriculture, Agricultural Research Service, U.S. National Poultry Research Center, Avian Disease and Oncology Laboratory, East Lansing, MI 48823, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7287-0916","authenticated-orcid":false,"given":"John R.","family":"Dunn","sequence":"additional","affiliation":[{"name":"United States Department of Agriculture, Agricultural Research Service, U.S. National Poultry Research Center, Avian Disease and Oncology Laboratory, East Lansing, MI 48823, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,12,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"283","DOI":"10.1038\/nrmicro1382","article-title":"Marek\u2019s Disease Virus: From Miasma to Model","volume":"4","author":"Osterrieder","year":"2006","journal-title":"Nat. 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