Retrovirally transduced human dendritic cells can generate T cells recognizing multiple MHC class I and class II epitopes from the melanoma antigen glycoprotein 100

Involvement of tumor-Ag specific CD4(+) and CD8(+) T cells could be critica l in the generation of an effective immunotherapy for cancer. In an attempt to optimize the T cell response against defined tumor Ags, we previously d eveloped a method allowing transgene expression in human dendritic cells (D Cs) using retroviral vectors. One advantage of using gene-modified DCs is t he potential ability to generate CD8(+) T cells against multiple class I-re stricted epitopes within the Ag, thereby eliciting a broad antitumor immune response. To test this, we generated tumor-reactive CD8(+) T cells with DC s transduced with the melanoma Ag gp100, for which a number of HLA-A2-restr icted epitopes have been described. Using gp100-transduced DCs, we were ind eed able to raise T cells recognizing three distinct HLA-A2 epitopes within the Ag, gp100(154-162), gp100(209-217), and gp100(280-288). We next tested the ability of transduced DCs to raise class II-restricted CD4(+) T cells. Interestingly, stimulation with gp100-transduced DCs resulted in the gener ation of CD4(+) T cells specific for a novel HLA-DR beta1*0701-restricted e pitope of gp100. The minimal determinant of this epitope was defined as gp1 00(174-190) (TGRAMLGTHTMEVTVYH). These observations suggest that retroviral ly transduced DCs have the capacity to present multiple MHC class I- and cl ass II-restricted peptides derived from a tumor Ag, thereby eliciting a rob ust immune response against that Ag.