ABSTRACT
Antitumor antibodies with the same specificity as cytotoxic T lymphocytes that recognize antigenic peptides encoded by tumor-associated genes and presented by MHC class I molecules would be valuable tools to analyze the antigenicity or target tumor cells in vivo. To obtain a human antibody directed against a peptide encoded by gene melanoma-associated antigen (MAGE)-A1 and presented by HLA-A1 molecules, we selected a large phage Fab antibody repertoire on a recombinant version of the complex HLA-A1-MAGE-A1 produced by in vitro refolding. One of the selected phage antibodies shows binding to HLA-A1 complexed with the MAGE-A1 peptide, but does not show binding to HLA-A1 complexed with a peptide encoded by gene MAGE-A3 and differing from the MAGE-A1 peptide by only three residues. Phages carrying this recombinant antibody bind to HLA-A1(+) cells only after in vitro loading with MAGE-A1 peptide. These results indicate that nonimmunized phage Fab libraries are a source of antibodies with a T cell antigen receptor-like specificity. The human anti-HLA-A1-MAGE-A1 antibody described here may prove very useful for monitoring the cell surface expression of these complexes, and eventually, as a targeting reagent for the specific immunotherapy of HLA-A1 patients bearing a MAGE-A1-positive tumor.
Subject(s)
Antibodies, Neoplasm/genetics , HLA-A1 Antigen/immunology , Immunoglobulin Fab Fragments/genetics , Melanoma/immunology , Neoplasm Proteins/immunology , T-Lymphocytes/immunology , Antigen Presentation , Antigens, Differentiation , Antigens, Neoplasm , Biosensing Techniques , Cloning, Molecular , Epitopes , Flow Cytometry , HLA-A1 Antigen/isolation & purification , Humans , Melanoma-Specific Antigens , Neoplasm Proteins/isolation & purification , Peptide Library , Protein Folding , Selection, GeneticABSTRACT
Two human alloantisera, previously described as possibly detecting new beta 2-microglobulin associated proteins, selectively expressed on HLA-A2 and HLA-A1 phytohaemagglutinin (PHA)-activated lymphocytes, immunoprecipitated only molecules with the same isoelectric point as HLA-A1 and A2 products. This result suggests that the selected alloantisera do not react with the products of an HLA class I locus different from ABC but probably recognize a new epitope arising on HLA-A molecules upon conformational changes consequent to cell activation.
