Establishment of lymphoblastoid cell lines from Marek's disease primary tumors

Serial transfer of a transplantable tumor: implications for Marek's vaccine mechanisms

The mechanism of Marek's disease (MD) vaccination to prevent the lymphoproliferative disease in chickens is not well understood. It is generally recognized that vaccination prevents disease, including the induction of T-cell tumors, but it does not prevent the pathogenic virus from infecting and replicating in the vaccinated host, nor does it prevent bird to bird spread of the oncogenic virus. The stage at which the vaccinated immune system intervenes in the process from infection to the induction of tumors remains obscure. Using a transplantable tumor induced by the Md5 strain of MD virus (MDV), we show that CVI988 vaccination does not prevent the induction of transplantable tumors in the 15I(5) x 7(1) chicken line. A monoclonal tumor with a V beta 1 T-cell receptor spectratype of 207 base pairs was used to follow the transplantable tumor in serial passages in vivo. This transplantable tumor could be passed in vaccinated birds. The length of time between vaccination and challenge (5 to 12 days) had little or no influence on the ability to transfer the tumor. There was variability in the manifestation of the disease produced by the transplanted tumor. Some chickens presented as normal but were still capable of transmitting the transplanted tumor to newly vaccinated recipients via their blood. This indicates that some chickens can control, but not eliminate, the tumor. The variables inducing health or disease in the challenged chickens remain obscure, but environmental or other factors likely depress the immune system allowing the tumor to overwhelm the immune system.

Effect of cyclosporin a on normal, mitogen-stimulated and Marek's disease virus-exposed and transformed chicken lymphoid cells

Studies have been made with the immunosuppressive drug cyclosporin A (CsA) to examine its value in the establishment of lymphoid tumour cell lines from Marek's disease (MD) lymphomas and from lymphoid cell cultures exposed to MD virus in vitro. CsA was shown to depress the proliferative response of normal spleen cells to phytohaemagglutinin, Concanavalin A and pokeweed mitogen, and to a lesser extent to lipopolysaccharide. Short-term proliferative responses of lymphoma cells were either not affected, depressed or stimulated by CsA. The efficiency of establishment of lymphoid cell lines from long-term cultures of lymphoma cells was not increased by CsA, and the drug had a depressive effect on the proliferation of cell lines in the lympho-cytoid stage. The majority of lymphoblastoid cell lines studied were stimulated by CsA. Interleukin 2 partially overcame the suppressive effect of CsA on the cell lines, and enhanced the stimulatory effects. Cultures of lymphoid cells exposed to MD virus in vitro were usually depressed by CsA; a few stimulatory combinations were observed, but these were not considered to be of biological significance. These results indicate that CsA suppresses normal T-cell responses in the chicken, but that some MD-associated lymphoid cells are stimulated by the drug, in some instances at least by a direct effect.

Antibody directed against Marek's disease-associated tumor surface antigen can be eluted from Marek's disease tumor cells

Antibody directed against Marek's disease-associated tumor surface antigen (MATSA) was eluted from tumor cells of lymphomas and peripheral blood lymphocytes that were isolated from Marek's disease virus-infected chickens. Feather follicular Marek's disease virus (MDV) antigen could not be demonstrated with this antibody by indirect immunofluorescent (IF) staining. Monoclonal antibody directed against MATSA could completely block the activity of eluted antibody and vice versa. By indirect IF staining using eluted antibody and fluorescein isothiocyanate (FITC) labelled antichicken globulin conjugate. MATSA-bearing cells were detected in MDV infected and herpes virus of turkey (HVT) vaccinated birds. Blocking of immunoglobulin molecules present on B-cells by anti-chicken globulin is critical in this test.