A recombinant vaccinia virus encoding a modified peptide of the gp100 melanoma-melanocyte antigen with potential use in cancer immunotherapy. gp100 human antigen is a wild type self-antigen expressed by melanocytes, pigmented retinal cells and most melanomas. gp100p209 is a fragment epitope of gp100 in which the threonine in position 2 is replaced with methionine; this modification may stimulate tumor infiltrating lymphocytes (TIL) more efficiently. (NCI04) [ ]