Submitted to: Vaccine
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/22/2008
Publication Date: 4/4/2008
Citation: Lee, L.F., Lupiani, B., Silva, R.F., Kung, H., Reddy, S.M. 2008. Recombinant Marek's disease virus (MDV) lacking Meq oncogene confers protection against challenge with a very virulent plus strain of MDV. Vaccine. 26:1887-1892. Interpretive Summary: Marek’s disease (MD), a virus-induced cancer-like disease of chickens, is a major disease problem in commercial poultry. The objective of this research was to develop a vaccine which can protect chickens better than the existing vaccine known as CVI988/Rispens. We have developed a recombinant Marek's disease virus in which a gene known to be associated with tumors (Meq gene)has been removed. This virus is named rMd5delta MEQ and is no longer pathogenic in chickens and confers complete protection against very virulent challenge virus termed vv+648A. The protective efficacy was significantly better than the CVI988/Rispens vaccine. The information obtained from this research is of great interest to the poultry industry as well as scientists and academia. The finding is novel because rMd5delta MEQ virus which lack oncogene Meq not only did not cause tumor but also can be a good vaccine against MD.
Technical Abstract: Marek’s disease virus (MDV) encodes a basic leucine-zipper protein, Meq that shares homology with Jun/Fos family of transcriptional factors. Evidence that Meq is an oncogene of MDV came from the recent studies of a Meq-null virus, rMd5'Meq. This virus replicated well in vitro, but was non-oncogenic in vivo. Further characterization of this virus in vivo indicated that the virus is dispensable for cytolytic infection since it replicated in the lymphoid organs and feather follicular epithelium. Since rMd5'Meq virus was apathogenic for chickens, we set to investigate whether this virus could be a good candidate vaccine. Vaccine efficacy experiments conducted in ADOL 15I5 x 71 chickens vaccinated with rMd5'Meq virus or an ADOL preparation of CVI988/Rispens indicated that the Meq-null virus provided superior protection than CVI988/Rispens when challenged with the very virulent MDV 648A strain.