Neoplastic cells were isolated from 2 sibling Great Dane/Labrador Retriever mixed-breed dogs in which telangiectatic type osteosarcomas arose concurrently. Cells from various sites in the same osteosarcoma appeared similar in culture, but there were differences between the 2 osteosarcomas in growth characteristics and appearance of cells. Cells from 1 osteosarcoma had a small, but significant (P less than 0.05), cyclic adenosine monophosphate response to parathyroid hormone stimulation, indicating a low order of osteoblastic differentiation. Cells from the other osteosarcoma had no response to parathyroid hormone stimulation. Cells from both osteosarcomas and a concentrated cell-free filtrate from the osteosarcoma with osteoblastic differentiation were injected into nude mice, but osteosarcomas were not induced. Results of ultrastructural examination of osteosarcoma samples for viral particles were negative and supernatant fluids from cultured cells were considered negative for viral reverse transcriptase activity.

Seven hybridomas that secreted monoclonal antibodies (MAB) against the peplomer protein and one that secreted MAB against the nucleocapsid protein of Berne virus (proposed family Toroviridae) were isolated. All MAB directed against the peplomer protein neutralized virus infectivity and, with the exception of MAB 6A7, inhibited each other's binding in competition assays. Neutralization of Berne virus infectivity was potentiated when some MAB were used in pairs. The antibodies have been used to localize toroviral proteins in infected cells; use of antipeplomer MAB 6B10 yielded a diffuse intracytoplasmic immunofluorescence, whereas the antinucleocapsid MAB 1F1 detected antigen in the intra- and perinuclear compartments. By use of radioimmune precipitation, protein A of Staphylococcus aureus was found to bind directly to the nucleocapsid polypeptide, without the requirement for specific antibody. Using fluorescein isothiocyanate-conjugated protein A, the intranuclear accumulation of the nucleoprotein of Berne virus was confirmed by results of immunofluorescence.