Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/20/2014
Publication Date: 7/20/2014
Citation: Mays, J.K., Dunn, J.R., Fadly, A.M. 2014. Protective efficacy of a recombinant BAC clone of Marek's disease virus containing REV-LTR [abstract]. In: Proceeding of 10th International Symposium on Marek's Disease and Avian Herpesviruses, July 20-23, 2014, East Lansing, Michigan. p. 84.
Technical Abstract: Insertion of reticuloendotheliosis virus (REV) long-terminal repeat (LTR) into a bacterial artificial chromosome (BAC) clone of a very virulent strain of Marek’s disease (MD) virus (MDV), Md5 (Kim et al, 2011) rendered the resultant recombinant virus termed rMd5 REV-LTR BAC fully attenuated at passage 40 (Mays et al., 2012). In the current study, we evaluated the protective efficacy of rMd5 REV-LTR BAC as a MD vaccine. First, based on results obtained from testing the pathogenicity of Various passages of the virus in maternal antibody (Mab)-negative chickens, we determined that the optimal passage level of rMd5 REV-LTR BAC to be used in protective efficacy studies is passage 70. Three protective efficacy trials were conducted using rMd5 REV-LTR BAC at passage 70 along with both Meq-deleted BAC and Meq- deleted cosmid clones of strain rMd5 from our laboratory, and commercially available MD vaccines. Groups of Mab-positive and Mab-negative 15I X 7 chickens were inoculated intra-abdominally at day of hatch with 2000 pfu of various vaccine viruses, and challenged at 5 days post-vaccination with 500 pfu of a vv+ MDV, strain 686 at passage 10. Chickens were monitored for 8 weeks of age; all chickens that died during the experiment and those that were euthanized at termination were necropsied and evaluated for MD lesions. Results indicate that passage 70 of rMd5 REV-LTR BAC virus provided protection comparable to that provided by the most effective currently available commercial vaccine, namely Rispens following challenge with a vv+ MDV, suggesting that this virus is a good candidate vaccine that can be used in flocks where a vv+ MDV challenge is expected.