DINITROPHENYL-MODIFIED AUTOLOGOUS MELANOMA VACCINE INDUCES A T-CELL RESPONSE TO HAPTEN-MODIFIED, MELANOMA PEPTIDES

Active specific immunotherapy with dinitrophenyl (DNP)-modified autolo gous melanoma vaccine elicits inflammatory responses in metastatic tum or sites. Postsurgical adjuvant immunotherapy with this vaccine prolon gs survival in stage III melanoma patients. We have reported that, aft er administration of DNP-modified melanoma vaccine, T cell responses t o DNP-modified autologous tumor cells are demonstrable in vivo and in vitro. These responses are hapten specific and MHC restricted. To eluc idate this phenomenon, we investigated the immune response to DNP-modi fied peptides eluted from autologous cells. Short peptides were extrac ted from DNP-modified and unmodified autologous melanoma cells by an a cid elution technique and HPLC fractionation. Peptides were also extra cted from DNP-modified and unmodified, EB virus-transformed, autologou s B lymphoblasts. These various peptide fractions were loaded onto aut ologous B lymphoblasts and tested for ability to elicit a response by a DNP-specific T cell line as measured by IFN-gamma production. Unexpe ctedly, stimulatory activity of peptides from DNP-modified melanoma ce lls was confined to a single HPLC fraction. Spectrometric analysis of this fraction confirmed modification of peptides with DNP. A weaker T cell response was observed to a single HPLC fraction of DNP-modified p eptides from the patient's B lymphoblasts. No T cell response was elic ited by corresponding fractions of peptides eluted from unmodified mel anoma cells or B lymphoblasts. These findings demonstrate the human T cell response to DNP-modified autologous melanoma cells is mediated by hapten-modified, MHC-associated peptides. Further investigation of th ese peptides could lead to a new strategy for peptide-based cancer imm unotherapy. (C) 1997 Academic Press.