Submitted to: Avian Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/11/2005
Publication Date: 8/1/2005
Citation: Gimeno, I.M., Witter, R.L., Fadly, A.M., Silva, R.F. 2005. Novel criteria for the diagnosis of Marek's disease virus-induced lymphomas. Avian Pathology. 34(4):332-340. Interpretive Summary: Marek's disease (MD), a virus-induced cancer-like disease of chickens, is considered as a major disease problem in commercial poultry. There are several viruses that are able to induce similar kinds of cancer in chickens and a correct diagnosis is very important to establish proper measures of control. The objective of this research was to improve methods of diagnosing MD tumors using new available technologies. In particular we have studied the expression of different genes of the virus and of the tumor cell in the tumors as well as the amount of MD virus within the tissues. Our results show that the amount of MD virus in the tumor and expression of meq, an oncogene of MD virus, are good criteria for the diagnosis of MD tumors. This important information about MD diagnosis will help scientists in academia and industry to improve methods of diagnosis and therefore establish more appropriate control measures.
Technical Abstract: Several novel criteria have been tested to assist in the differential diagnosis of tumors induced by Marek's disease virus (MDV) from those induced by avian leukosis virus (ALV) and reticuloendotheliosis virus (REV). A collection of tumors induced by inoculation of specific strains of MDV, ALV and REV, alone or in combination, were tested for quantification of MDV DNA by real time PCR, expression of the MDV oncogene Meq, expression of several cell markers associated with transformation (AV37, Marek's disease-associated surface antigen or MATSA, and p53), and level of DNA methylation in the tumor cells. In addition, tissues latently infected with MDV and non infected tissues were tested as controls. Tumors induced by MDV had about 100 fold more copies of MDV DNA than either tissues latently infected by MDV or tumors induced by retrovirus in MDV vaccinated chickens. Moreover, the MDV antigen meq was consistently expressed in all MDV tumors but it could not be detected in tissues latently infected with MDV or in tumors induced by retrovirus in MDV vaccinated chickens. Other markers studied were not specific for MDV and therefore had limited value for diagnosis. Nonetheless, some of these markers might have potential value in research as they will help to identify transformed cells.