Characterization of the surface proteins of SV40-transformed mouse and human cells: absence of SV40-specific proteins

Quantitative cytofluorimetric determination of cell membrane-associated large tumor antigen on SV40-transformed cells

The aim of this study was to quantitate the number of cell membrane-located SV40 large tumor antigen (large T) molecules of SV40-transformed cell lines by cytofluorimetric analysis. Five different SV40-transformed cell lines were labelled by either a biotin- or a fluorescein-conjugated monoclonal antibody, PAb1605, which is specific for the large T carboxyterminus. The conjugated-antibody fluorescence signals of the stained large T molecules of transformed cells were measured via cytofluorimetry. Comparison of the fluorescence signals of calibrated beads bearing a known number of fluorescein molecules to the signals of conjugated PAb1605 antibodies bound on microbeads to a defined number of IgG binding sites made it possible to determine the number of antibody-accessible large T molecules per SV40-transformed cell. The numbers (x10(-4)) found per cell were 1.0 (ELONA, hamster), 3.0 (VLM, mouse), 3.5 (mKSA, mouse), 11 (C57SV, mouse), and 5.5 (SV80, human), respectively. Thus, the technique described allows a precise quantitation of surface-exposed, antibody-accessible viral antigen expression.

Demonstration of T antigens on the surface of cells transformed with primate polyoma viruses

Primate polyoma virus-transformed hamster, mouse, and rat cell lines were examined by indirect immunofluorescence staining for cell surface-associated T antigens, by using a rabbit antiserum prepared against sodium dodecyl sulfate-denatured large T antigen of simian virus 40 (anti-SV40-SDS-T serum). Positive surface staining was shown not only on SV40-transformed cells, but also on BK and JC virus-transformed cells. In contrast, normal cells and cells transformed with mouse polyoma-, human adeno-, and murine sarcoma viruses were negative. The data on SV40-transformed cells confirmed the reports of others demonstrating the cell surface location of SV40 large T antigen, and the data on BK and JC virus-transformed cells proved that these cells have cell-surface T antigens that cross-react with anti-SV40-SDS-T serum.

In vivo induction of tumor-specific immunity by glycolipid extracts of SV40-transformed cells

Glycolipid extracts were prepared from various Syrian golden hamster cell lines, either SV40-transformed or spontaneously transformed. To detect possible SV40-TSTA activity of the glycolipid preparations, normal hamsters were inoculated with different glycolipid extracts and were subsequently challenged with an SV40 tumor-cell line. Significant immunoprotection against SV40 tumor challenge was induced with glycolipids obtained from SV40-transformed cell lines. This was expressed as complete tumor rejection or as a decrease in tumor growth rate, when compared to controls. No protective effects were induced with glycolipid extracts from spontaneously transformed cells. Results suggest that tumor-specific glycolipids synthesized in cells transformed by SV40 virus could act as tumor transplantation antigens responsible for specific tumor rejection in syngeneic hosts.

Isolation of tumor disturbing factor on the proliferation of tumor cells in human serum

The classified sediment with ethanol from sera of nude mice and humans showed a disturbing effect on L1210 cells in vitro and a lifesaving effect on L1210 cell-bearing mice in vivo. This factor was purified more than 2300-fold to a specific activity of approximately 1 X 10(5) U/mg by ethanol classified precipitation, Sephadex G-200 gel filtration, DEAE cellulose ion exchange chromatography with Nacl and pH gradient aqueous solution, and preparative polyacrylamide gel electrophoresis.