Melanoma-reactive CD8(+) T cells recognize a novel tumor antigen expressedin a wide variety of tumor types

An autologous melanoma cell line selected for loss of expression of the imm unodominant MART-1 and gp100 antigens was initially used to carry out a mix ed lymphocyte tumor culture (MLTC) in a patient who expressed the human leu kocyte antigen (HLA)-A1 and HLA-A2 class I major histocompatibility complex alleles. Ten clones identified from this MLTC seemed to recognize melanoma in an HLA-A1-restricted manner but failed to recognize a panel of previous ly described melanoma antigens. The screening of an autologous melanoma cDN A library with one HLA-A1-restricted melanoma-reactive T-cell clone resulte d in the isolation of a cDNA clone called AIM-2 (antigen isolated from immu noselected melanoma-2). The AIM-2 transcript seemed to have retained an int ronic sequence based on its alignment with genomic sequences as well as exp ressed sequence tags. This transcript was not readily detected after Northe rn blot analysis of melanoma mRNA, indicating that only low levels of this product may be expressed in tumor cells. Quantitative reverse transcriptase -polymerase chain reaction analysis, however, demonstrated a correlation be tween T-cell recognition and expression in HLA-A1-expressing tumor cell lin es. A peptide that was encoded within a short open reading frame of 23 amin o acids and conformed to the HLA-A1 binding motif RSDSGQQARY was found to r epresent the T-cell epitope. The AIM-2-reactive T-cell clone recognized a n umber of neuroectodermal tumors as well as breast, ovarian, and colon carci nomas that expressed HLA-A1, indicating that this represents a widely expre ssed tumor antigen. Thus, AIM-2 may represent a potential target for the de velopment of vaccines in patients bearing tumors of a variety of histologie s.