Human high-molecular-weight melanoma-associated antigen mimicry by mouse antiidiotypic monoclonal antibody TK7-371.

Since the human high-molecular-weight melanoma-associated antigen (HMW-MAA) represents a useful target to implement active specific immunotherapy with mouse antiidiotypic monoclonal antibody (mAb), the present study is aimed at developing and characterizing mouse antiidiotypic mAbs which bear the mirror image of the determinant defined by the anti-HMW-MAA mAb TP61.5. To this end, a BALB/c mouse was immunized with the syngeneic mAb TP61.5. Screening of the 703 generated hybridomas showed that 13 of them secrete antiidiotypic mAbs which inhibit the binding of the immunizing mAb TP61.5 to melanoma cells by at least 75%. The dose of antiidiotypic mAb required to inhibit by 50% the binding of mAb TP61.5 to melanoma cells ranged between 4 and 200 ng. The 13 antiidiotypic mAbs recognize conformational idiotypes, since they did not react in Western blotting with the heavy and light chain of mAb TP61.5 isolated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. Furthermore, the 13 antiidiotypic mAbs did not react with 23 mAbs which recognize 13 determinants of the HMW-MAA distinct from that defined by mAb TP61.5. Analysis of the 13 antiidiotypic mAbs for their ability to elicit cellular and humoral anti-HMW-MAA immunity showed that only mAb TK7-371 elicited a delayed-type hypersensitivity reaction to HMW-MAA-bearing cells in syngeneic hosts and anti-HMW-MAA antibodies in BALB/c mice and in rabbits. Since rabbits express the HMW-MAA, the present results indicate that the antiidiotypic mAb TK7-371 can induce humoral immunity to self HMW-MAA. Therefore, the antiidiotypic mAb TK7-371 may be an efficacious immunogen to implement active specific immunotherapy in patients with melanoma.