A T cell line recognizing autologous and allogeneic HLA-A3.1
melanomas was obtained from a disease-free
melanoma patient (patient 15392). By transfection of a
tumor cDNA library and in vitro sensitization experiments, the
ALLAVGATK gp100/Mel17-derived
peptide was found to be the
epitope recognized by this
melanoma-specific T cell line. The role of the
ALLAVGATK peptide in the systemic immune response to
melanoma of this patient was evaluated. When pulsed on the autologous peripheral blood mononuclear cells, the
ALLAVGATK peptide generated
tumor-specific HLA-A3-restricted T lymphocytes and a single restimulation in vitro was sufficient to raise gp100-specific T lymphocytes, indicating a high frequency of
epitope-specific T cells. gp100-specific T cells were also induced from T lymphocytes purified from
tumor-invaded lymph nodes (
tumor-associated lymphocytes, TAL). TAL-derived effectors displayed lower
peptide affinity and lower
tumor recognition than effectors elicited from peripheral blood lymphocytes (PBL). To further evaluate its immunogenicity,
ALLAVGATK was used to stimulate PBL derived from six additional HLA-A3.1
melanoma patients and seven healthy donors. After 7 weeks of
peptide stimulation in vitro the generation of anti-gp100 and
tumor-specific T cell lines was achieved in one out of the six patients analyzed. Taken together these data indicate that an in vivo priming leading to a systemic immunity against gp100 in
HLA-A3 melanoma patients may occasionally occur and that the immunogenicity of
ALLAVGATK peptide in
melanoma patients is comparable to that of other HLA-A2-restricted
epitopes derived from gp100/Mel 17
protein.