Carcinoembryonic antigen (CEA), which is expressed in several cancer types, is a potential target for specific immunotherapy. HLA‐A24 is the most frequent allele among Japanese and is also frequently present in Asians and Caucasians. We tested CEA‐encoded HLA‐A24 binding peptides for their capacity to elicit anti‐tumor cytotoxic T lymphocytes (CTL) in vitro. For this purpose, we used CD8+ T lymphocytes from peripheral blood mononuclear cells (PBMC) of a healthy donor and autologous peptide‐pulsed dendritic cells as antigen‐presenting cells. This approach enabled us to identify 2 peptides, QYSWFVNGTF and TYACFVSNL, which were capable of eliciting CTL lines that lysed tumor cells expressing HLA‐A24 and CEA. The cytotoxicity to tumor cells by the CTL lines was antigen‐specific since it was inhibited by peptide‐pulsed cold target cells as well as by anti‐class I major histocompatibility complex (MHC) and anti‐CD3 monoclonal antibodies (MAbs). The antigen specificity of the 2 CTL lines was examined using several tumor cell lines of various origins and for their peptide‐dose responses. The identification of these novel CEA epitopes for CTL offers the opportunity to design and develop epitope‐based immunotherapeutic approaches for treating HLA‐A24+ patients with tumors that express CEA. Int. J. Cancer 80:92–97, 1999. © 1999 Wiley‐Liss, Inc.
In order to study the antigenicity of envelope 46 kDa glycoprotein (gp46) of human T-cell leukemia virus type-I (HTLV-1), we have generated monoclonal anti-gp46 antibodies (MAbs), REY-7, REY-11, REY-16, REY-30, MET-2 and MET-3 from rats and mice. Immunoblot and immunofluorescence assays showed that these MAbs recognize gp46 and its related antigens, and specifically stained HTLV-I-bearing cells. All MAbs reacted with a recombinant gp46 antigen, N147, expressing the 147 amino acids in the C-terminal half of gp46. By using various synthetic peptides corresponding to the gp46 sequence, epitopes recognized by REY-7 and MET-3, REY-11 and REY-16, and REY-30 were mapped to regions corresponding to the amino acids 175-199, 253-282 and 288-312, respectively. MET-2 did not react with any of the peptides used. These results indicate that the present MABs are directed against at least 4 distinct epitopes expressed on the C-terminal half of gp46. The binding of these MAbs to gp46 was specifically inhibited by sera from HTLV-I-infected individuals, but none of these MAbs inhibited the cell fusion activity of HTLV-I.
Carcinoembryonic antigen (CEA), which is expressed in several cancer types, is a potential target for specific immunotherapy. HLA-A24 is the most frequent allele among Japanese and is also frequently present in Asians and Caucasians. We tested CEA-encoded HLA-A24 binding peptides for their capacity to elicit anti-tumor cytotoxic T lymphocytes (CTL) in vitro. For this purpose, we used CD8 ؉ T lymphocytes from peripheral blood mononuclear cells (PBMC) of a healthy donor and autologous peptide-pulsed dendritic cells as antigenpresenting cells. This approach enabled us to identify 2 peptides, QYSWFVNGTF and TYACFVSNL, which were capable of eliciting CTL lines that lysed tumor cells expressing HLA-A24 and CEA. The cytotoxicity to tumor cells by the CTL lines was antigen-specific since it was inhibited by peptide-pulsed cold target cells as well as by anti-class I major histocompatibility complex (MHC) and anti-CD3 monoclonal antibodies (MAbs). The antigen specificity of the 2 CTL lines was examined using several tumor cell lines of various origins and for their peptide-dose responses. The identification of these novel CEA epitopes for CTL offers the opportunity to design and develop epitope-based immunotherapeutic approaches for treating HLA-A24 ؉ patients with tumors that express CEA. Int. J. Cancer 80:92-97, 1999.
To construct a mouse/human chimeric antibody, we cloned the genomic DNAs for Ig from a murine hybridoma that produces PL7-6 monoclonal antibody specific to human P-selectin and expressed them in SP2/0 myelomas using a series of pSV2 vectors. Transfected cells that produce the mouse/human chimeric anti-human P-selectin antibody were geneticin-selected and screened by an immunoassay using immobilized antigen. The chimeric antibody, cPL-2R1, expressed by the resultant clone has the murine Ig variable region and the human Ig constant region. The native antibody PL7-6 and the chimeric antibody cPL-2R1 react equally with purified P-selectin and thrombin-stimulated platelets. Competitive inhibition tests demonstrated that the native antibody PL7-6 and the chimeric antibody cPL-2R1 had identical affinity for purified human P-selectin. Thus, although human IgG1 constant region was substituted for the murine counterpart in this chimeric antibody, its specificity and binding affinity for P-selectin was not altered. This chimeric antibody may prove useful when employed in combination with imaging reagents or therapeutic drugs for targeting activated platelets or endothelium in patients with thrombosis or intravascular inflammation.
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