Submitted to: Avian Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/9/2007
Publication Date: 9/30/2007
Citation: Heidari, M., Fitzgerald, S.D., Zhang, H.M., Silva, R.F., Lee, L.F., Dunn, J.R. 2007. MDV-induced skin leukosis in scaleless chickens: tumor development in the absence of feather follicles. Avian Diseases. 51(3):713-718. Interpretive Summary: Marek's disease causes enormous economical losses to the poultry industry. Marek's disease associated skin lesions have been encountered commonly at the broiler processing plants and have been a major cause of condemnations. Marek's disease virus (MDV) is produced in the epithelial cells of the skin that surround the feather roots and is spread into the environment by dander and feather dust. Featherless chickens that produce only a few scattered feathers over their body were used to study MDV-associated skin lesions and feather follicles involvement in tumor development. Data from this study show that both epithelial cells surrounding the feather follicles and the skin epithelial cells not associated with feather follicles are capable of supporting the production of MDV. It was also shown that the MDV-induced skin lesions are tumorous in nature and not inflammatory reaction to viral infection. Finally, our data indicate that Marek's disease associated tumors develop in the absence of feathers and feather follicles. The information obtained from this research is of great interest to scientists in industry and academia, as it will help to better understand the mechanism of Marek's disease virus related skin tumors, virus production, spread, and eventually control of Marek's disease in poultry.
Technical Abstract: Marek's disease virus (MDV) is an oncogenic cell-associated herpesvirus that causes T-cell lymphoma in chickens. Lymphoproliferative neoplasms in Marek's disease (MD) occur in various organs and tissues including the viscera, peripheral nerves, skin, gonads, and musculatures. MDV is restrictively produced in the feather follicle epithelial (FFE) cells and it gains access to the external environment via infected cells or as infectious enveloped cell-free virus particles. The goals of the present study were: 1) to determine whether the MDV-induced skin lesions are neoplastic in nature or inflammatory reactions to viral infection; 2) to determine whether physical presence of feather follicles (FF) is necessary for skin tumor development; and 3) to study the role of skin epithelial cells not associated with feathers or feather follicles in the replication and dissemination of infectious virus particles. Scaleless chickens that produce only a few scattered feathers and no sculate scales along the anterior metatarsi were used as a unique model to study the pathogenesis of dermal lesions. Histological and immunohistochemical analysis revealed that the cutaneous lesions were tumorous as was manifested by massive accumulation of lymphoblasts and extensive activation of meq oncoprotein, the hallmark of MDV oncogenesis, within the skin lesions. Neoplastic cutaneous lesions in the scaleless chickens indicate that feather follicles are not necessary for skin tumor development. Finally, our preliminary data indicate that inoculation with supernatant fluid from homogenized and sonicated skin samples of MDV-infected scaleless chickens induces Marek's disease in susceptible birds, suggesting that skin epithelial cells not associated with FF also harbor infectious viral particles.