Submitted to: Virus Genes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2011
Publication Date: 7/1/2011
Citation: Kim, T., Mays, J.K., Fadly, A.M., Silva, R.F. 2011. Artifically inserting a reticuloendotheliosis virus long terminal repeat into a bacterial artificial chromosome clone of Marek's disease virus (MDV) alters expression of nearby MDV genes. Virus Genes. 42(3):369-376. Interpretive Summary: When reticuloendotheliosis virus (REV), a small virus that causes cancer-like disease in chickens, was grown together with Marek's disease virus (MDV), a large virus that also causes another cancer-like disease in chickens, a small portion of REV genetic material was inserted into MDV. The MDV containing a portion of REV was unlike the parental MDV. The new MDV was not able to cause cancer in chickens. To determine whether the inserted REV genetic material was responsible for the observed change, we used specialized laboratory procedures to insert a small piece of REV genetic material into the same location in one of our highly characterized MDVs. We found that the newly constructed MDV acted very much like the original MDV with the REV insert. This finding confirmed that the naturally occurring insertion of REV genetic material can alter the disease-causing ability of MDV. This information is important and has implications for understanding the future evolution of MDVs that may occur in the field.
Technical Abstract: The long terminal repeat (LTR) sequence of reticuloendotheliosis virus (REV) was inserted into the very virulent Marek’s disease virus (MDV) Md5 bacterial artificial chromosome clone. The insertion site was nearly identical to the REV LTR that was naturally inserted into the JM/102W strain of MDV following cell culture co cultivation of JM/102W and REV. The recombinant rMd5-RM1-LTR virus was continuously passaged in duck embryo fibroblast (DEF) cultures. The inserted LTR sequences and transcripts adjacent to MDV open reading frames (ORF) MDV085, MDV086, SORF2, US1 and US10 were molecularly characterized. During blind passage in vitro, the inserted LTR sequences were duplicated from internal repeat short (IRS), the initial insertion site, to both IRS and terminal repeat short (TRS) region of MDV genome. The rMd5-RM1-LTR virus containing LTR sequences in both IRS and TRS was selected for further characterization. The transcripts of SORF2, directly downstream MDV ORF of LTR insertion are enhanced by an additional 4 kb polycistronic messages in rMd5-RM1-LTR virus. Collectively, the data indicate that the REV LTR insertion increased the transcripts of downstream SORF2