Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/1998
Publication Date: N/A
Citation: Interpretive Summary: Marek's disease virus (MDV) is a virus that causes Marek's disease, a serious economically important disease in chickens. The virus grows in cell culture in a cell-associated form by direct cell-to-cell contact. No cell-free infectious virus particles are produced in cell culture. In contrast, cell-free infectious virus is produced in skin cells associated with the feathers of chickens. The resulting virus is shed from the skin, infecting nearby birds and quickly spreading throughout a flock. It was not known why cell-free virus is only produced in cells associated with the chicken's feathers. Using reagents developed in another laboratory, we found a protein, produced by MDV, that is not made in cell culture but is made in the same infected cells in the chicken that produce the cell-free viruses. This protein is similar to a known protein produced by a herpesvirus that infects humans. The human herpesvirus protein is also known to be required for the generation of cell-free infectious virus. Thus, our findings suggest that certain unknown factors in chicken skin cells induce the MDV protein to be produced and that this protein is used to complete the process of making cell-free viruses. Our finding is the first report that may explain why the virus spreads so efficiently in chickens. Ultimately, this information may help us control the spread of MDV in infected flocks.
Technical Abstract: Glycoprotein D (gD) and its homologues are essential for many alphaherpesvirus life cycles. A gene encoding a homologue of gD was recently found in the Marek's disease virus (MDV) genome. Interestingly, gD negative MDV mutants apparently replicate unimpaired in both cell culture and in chickens. In this study, we show the expression of the gD homologue of MDV in feather follicle epithelium in infected birds. The gD homologue was detected in a few feather follicles even when most of the follicles were expressing either pp38 or gB, other MDV specific proteins. These observations indicate that the MDV gD homologue is expressed in a very limited set of cells and may be differently regulated. Since feather follicle epithelium of infected birds are the only place where the infectious cell-free MDV virions can be recovered, analysis of the transcriptional regulation of gD may lead to the understanding of the cell- -associated nature of MDV.