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Title
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Biochemical identification of a mutated human melanoma antigen recognized by CD4(+) T cells.
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Authors
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R.Pieper,
R.E.Christian,
M.I.Gonzales,
M.I.Nishimura,
G.Gupta,
R.E.Settlage,
J.Shabanowitz,
S.A.Rosenberg,
D.F.Hunt,
S.L.Topalian.
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Ref.
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J Exp Med, 1999,
189,
757-766.
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PubMed id
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Abstract
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CD4(+) T cells play a critical role in generating and maintaining immune
responses against pathogens and alloantigens, and evidence suggests an important
role for them in antitumor immunity as well. Although major histocompatibility
complex class II-restricted human CD4(+) T cells with specific antitumor
reactivities have been described, no standard method exists for cloning the
recognized tumor-associated antigen (Ag). In this study, biochemical protein
purification methods were used in conjunction with novel mass spectrometry
sequencing techniques and molecular cloning to isolate a unique melanoma Ag
recognized by a CD4(+) tumor-infiltrating lymphocyte (TIL) line. The
HLA-DRbeta1*0101-restricted Ag was determined to be a mutated glycolytic enzyme,
triosephosphate isomerase (TPI). A C to T mutation identified by cDNA sequencing
caused a Thr to Ile conversion in TPI, which could be detected in a tryptic
digest of tumor-derived TPI by mass spectrometry. The Thr to Ile conversion
created a neoepitope whose T cell stimulatory activity was enhanced at least 5
logs compared with the wild-type peptide. Analysis of T cell recognition of
serially truncated peptides suggested that the mutated amino acid residue was a
T cell receptor contact. Defining human tumor Ag recognized by T helper cells
may provide important clues to designing more effective immunotherapies for
cancer.
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