DISIALOGANGLIOSIDE G(D2) ANTIIDIOTYPIC MONOCLONAL-ANTIBODIES

Disialoganglioside G(D2) is widely expressed among neuroblastomas, mel anomas, small-cell lung carcinoma, sarcomas and brain tumors. Immunity directed against this antigen may have anti-tumor utility. Since G(D2 ) is poorly immunogenic, anti-idiotypic antibodies may serve as altern ative tumor vaccines. Monoclonal antibody 3F8, a murine IgG3 specific for G(D2), has shown excellent tumor-targeting ability in vitro and in vivo. LOU/CN rats were immunized with 3F8 and their spleens were used in somatic-cell hybridization, using SP2/0, P3 and Y3 as fusion partn ers. Six anti-idiotypic (anti-id) MAbs (C2D8, Idio-2, AlG4, C2H7, C4E4 , A2A6) were selected based on their reactivity with 3F8 and non-react ivity with murine IgG3 myelomas. Specificity of each anti-id was demon strated by using various ELISA: (i) lack of direct binding to solid ph ase myelomas and serum proteins; (ii) inability of other myelomas to i nhibit anti-id binding to 3F8; (iii) absence of cross-reactivity of ot her myelomas to solid-phase anti-id; (iv) lack of inhibition by anti-i d of binding of other ganglioside antibodies to their antigens. Antige n specificity was further examined by inhibition of binding of 3F8 to G(D2) on immuno-thin-layer chromatography, and by inhibition of 3F8 im munostaining of neuroblastoma cell lines. These 6 antibodies were demo nstrated to be distinct, in view of their cross-reactivity, fusion par tners and relative strength of binding to 3F8. Anti-G(D2) antibodies w ere induced after immunization with these anti-id antibodies in C57B1/ 6 mice. These rat anti-3F8-idiotypic antibodies with exquisite specifi city for anti-G(D2) antibodies may be useful in vaccine construction.