The role of herpesvirus in the induction of tumors in quail by methylcholanthrene

Previous reports have identified Mareks Disease virus (MDV) sequences in the QT35 cell line using the polymerase chain reaction (PCR). The QT35 cell line was induced by injection of methylcholanthrene (MCA) into the breast muscle of young quail. The purpose of this study is to ascertain the relationship of MDV and MCA in the pathogenesis of these induced breast muscle tumors. Two trials were conducted with quail divided into two treatment groups at hatch: uninoculated and those inoculated with the JM strain of MDV. At three weeks of age, quail were injected in the left breast muscle with 4 mg MCA carried in corn oil. In trial 1, all quail were inoculated with MCA whereas in trial 2, 20 quail in each group were injected with corn oil only. Quail were observed 3 times weekly for tumor development and growth, and were terminated and examined grossly at 8-9 weeks post MCA inoculation. Spleens were removed from all quail for PCR analysis using the MDV gene gB as a primer. Tumor samples were harvested for histopathology, in vitro culturing, and PCR. There was no difference in tumor development in the two groups, with the MCA only group having tumors in 32/81 birds and the MCA/JM group having 31/85 birds with tumors However, JM inoculation influenced tumor histologic type with undifferentiated fibrosarcomas, lymphosarcomas and combinations of these tumor types with or without metastasis observed only in the MCA/JM group. Fibrosarcomas without metastasis were the only tumors observed in the MCA only group. PCR examination of the spleens showed 1/93 positive in the MCA group and 66/91 positive for gB in the MCA/JM group. Tumor samples had 0/28 MDV positive in the MCA only group and 18/26 positive by PCR in the JM/MCA group. Therefore, herpesvirus did not affect tumor development but did influence tumor aggressiveness and histologic type.