Analysis of individual specific cytotoxic T lymphocytes for two MAGE-3-derived epitopes presented by HLA-A24.

Background: The human MAGE-3 gene encodes tumor-specific antigens that are recognized by cytotoxic T lymphocytes (CTLs) and expressed in a high percentage of various malignant tumors. Of the five MAGE-3-derived CTL epitopes identified to date, two nonapeptides (TFPDLESEF and IMPKAGLLI, designated MAGE-3.A24a and MAGE-3.A24b, respectively) can be expressed on the tumor surface by binding to the HLA-A24 molecule, which is the most frequent HLA class I molecule in Asian populations. To compare the immunogenecities of the two peptides, individual specific CTL lines were generated for each peptide (MAGE-3.A24a and MAGE-3.A24b).

Methods: Peripheral blood mononuclear cells (PBMCs) from four HLA-A24+ healthy donors were stimulated in vitro with autologous dendritic cells pulsed with MAGE-3.A24a, MAGE-3.A24b or both and were subsequently cultivated with a cytokine combination including interleukin-2.

Results: We succeeded in generating peptide-specific CTL lines in two of the four donors. The two CTL lines showed similar cytolytic levels against three MAGE-3+/HLA-A24+ cancer cell lines and also target cells pulsed with the corresponding peptide. Cytolytic activities were blocked by either anti-CD8 or anti-HLA-A24 monoclonal antibodies.

Conclusions: The results suggest that MAGE-3.A24a and MAGE-3.A24b peptides have equal potential in inducing MAGE-3-specific and HLA-A24-restricted CTLs.