Measurement of binding specificity between T cell lymphomas and murine leukemia viruses

We have previously reported the presence of receptors on radiation leukemia virus (RadLV)-induced thymomas and malignant thymocytes from AKR mice which specifically bind retrovirus produced by these T cell clones. These receptors have been shown to have specificity for virus reminiscent of an immune-specific receptor. Previous studies on T cell lymphoma binding to retroviruses have involved measurement of the interaction of labelled virus with cells using fluorescence-activated cell sorter (FACS) analysis (McGrath et al., J. Virol. (1978) 25, 923; McGrath and Weissman, Cell (1979) 17, 65; Weissman and McGrath, Curr. Top. Microbiol. Immunol. (1982) 98, 103). Here we report development of an assay for measuring lymphoma binding to virus, prepared as an immunoabsorbent adhered to a microtiter plate. Using this assay, we have shown that only T and not B cell lymphomas can bind to T cell-tropic viruses, and some cell lines have greatest specificity for homologous virus. The AKR-derived T cell lymphomas, SL3 and KKT-2, show greater specificity for leukemogenic AKR viruses, than for an AKR xenotropic virus or the recombinant AKR virus, MCF247. The RadLV-induced T cell lines, C6VL/1 and BL/VL3, have been found to bind cross-reactively to several different murine leukemia viruses (MuLVs). RadLV-induced T cell lymphomas do have greater specificity for their cognate retroviruses since free, homologous retrovirus can best block the interaction between cells and virus adhered to the wells of a microtiter plate. Cross-reactive interactions are more easily demonstrated by this assay, probably because low avidity interactions are stabilized as a result of the mode of virus presentation. Binding specificity for retroviral envelope determinants has been demonstrated using a rat anti-retroviral antiserum prepared as an F(ab)1 fragment. This antiserum can inhibit the interaction between the C6VL/1 thymoma and its RadLV virus. Specificity of this antibody for a gp70-like protein was confirmed by NaDodSO4-polyacrylamide gel electrophoresis (PAGE) and by loss of this activity after absorption of antibody on virus. Antibodies specific for RadLV/VL3 gp70 determinants can inhibit the interaction of C6VL/1 with RadLV/VL3 suggesting that cross-reactive binding to heterologous virus is also specific for a gp70 viral env determinant.