Mareks disease virus (MDV), the etiologic agent of Mareks disease, is a potent oncogenic herpesvirus. MDV is highly contagious and elicits a rapid onset of malignant T-cell lymphomas in chickens within weeks after infection. MDV codes for an oncoprotein, Meq, that shares resemblance with the Jun/Fos family of b-ZIP transcription factors. Earlier studies showed that Meq is responsible for development for T-cell lymphomas in chicken. In order to identify specific regions within the Meq gene, a series of recombinant MDV were generated in which a mutated gene was introduced in place of parental Meq gene. Various mutations were introduced at the phosphorylation sites, basic region, leucine zipper region and transactivation regions of the Meq gene. Several of these mutations have been shown to have an attenuated phenotype in chickens. In one embodiment, the present invention contemplates exploiting these mutations to develop MDV vaccines that are able to protect against challenge with highly virulent MDV strains.
