The long range goal of our studies is to develop an active specific immunotherapy strategy which counteracts the multiple mechanisms utilized by human melanoma cells to escape from immune destruction. To this end, both humoral and cellular immunity will be targeted to the human high molecular weight-melanoma associated antigen HMW-MAA) and to GD3 ganglioside each of which is independently expressed in at least 60 percent of melanoma lesions. This proposal stems from the apparent beneficial effects on the clinical course of malignant melanoma of humoral anti-HMW-MAA immunity elicited with anti-idiotypic (anti-id) mAb. These findings corroborate the validity of active specific immunotherapy with mimics of MAA. However, immunotherapy with anti-id mAb which bear the internal image of HMW-MAA and GD3 ganglioside suffers from i) inability to generate HLA Class I restricted, HMW-MAA specific CTL, ii) inability to induce a T cell dependent anti-GD3 ganglioside immune response and iii) low reactivity of anti-anti-id antibodies with the original antigen. Therefore, this proposal, which takes advantage of peptide mimics of MAA identified by panning phage display peptide libraries with mAb, aims at testing whether i) sequential immunization with peptide mimics of HMW-MAA and with the original antigen can induce high titer, high affinity anti-HMW-MAA antibodies; ii) peptide mimics of HMW-MAA or HMW-MAA derived peptides can induce HLA Class I restricted, HMW-MAA specific CTL, and iii) peptide mimics of GD3 ganglioside can induce a T cell dependent anti-GD3 ganglioside immune response which can be enhanced by booster with the original antigen. The proposed studies benefit from the availability of i) a unique panel of HMW-MAA binding anti-anti-id mAb which differ in the extent of reactivity with HMW-MAA among themselves and from the anti-HMW-MAA mAb 763.74, ii) an animal model system, i.e. rabbits, with a constitutive expression in tissues and with an antigenic profile of HMW-MAA and GD3 ganglioside similar to those in and iii) peptide mimics of HMW-MAA and GD3 ganglioside already identified in our laboratory. Characterization of the immunogenicity of peptide mimics of HMW-MAA and of GD3 ganglioside as well as of the enhancement of the immune response to self-MAA by boosting hosts with the original antigen will contribute to assess the potential of the novel strategies we have developed for active specific immunotherapy in patients with melanoma.
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