Reactivities of an anti-CEA peptide monoclonal antibody

New type of natural antibodies reactive to cytotoxic T lymphocyte-directed cancer vaccine peptides

We recently reported the existence of antibodies (Abs) reactive to cytotoxic T lymphocyte-directed cancer vaccine peptides derived from non-mutated and proliferation-related self-proteins in the sera of healthy donors. The IgG class of these Abs was either lacking or unbalanced in atopic dermatitis patients, although the induction of a specific IgG by peptide vaccination was correlated with long survival in cancer patients, suggesting its positive role in the host defense. To understand the biological features of these Abs, we employed murine models due to the sequence homology of these peptides in human and mouse. Both IgM and IgG classes of these peptide-specific Abs were detected in all of the euthymic mice tested; however, only IgM was found in athymic nu/nu mice, and not in SCID mice. Maintenance of euthymic mice under germ-free conditions resulted in a lack of the IgG class of the Abs in these mice. Ab levels were found to increase with age-maturation, but they decreased under tumor bearing conditions or in cases of graft-versus-host disease. The Abs showed catalytic activity upon hydrogen peroxide (H2O2) production. These results suggest the existence of a novel type of natural Ab that is reactive to cancer vaccine peptides.

Definition of the expression of the human carcinoembryonic antigen and non-specific cross-reacting antigen in human breast and lung carcinomas

Mouse cell lines transfected with carcinoembryonic antigen (CEA) and with 2 other members of the human CEA gene family, non-specific cross-reacting antigen (NCA) and biliary glycoprotein (BGP), were used to analyze the specificity of several monoclonal antibodies (MAbs). MAbs COL-1 and COL-6 were shown to react with the transfected CEA gene product but not with NCA, confirming previous results. Cells expressing the transfected BGP gene product also failed to react with COL-1 and COL-6. The MAb B6.2 reacted with cells expressing the NCA gene product but not with those expressing CEA or BGP. The MAb B1.1 reacted strongly with the transfected CEA and BGP gene products but only weakly with the NCA gene product. These antibodies were then utilized in the histochemical analysis of a number of primary and secondary breast and lung tumors. The results indicate that a majority of breast and lung tumors express CEA, and nearly all breast and lung tumors express NCA. Fairly homogeneous expression of CEA and NCA was seen in the majority of both breast and lung tumors. Our results indicate that CEA may be an important target for immunotherapy in a large number of patients with breast and lung tumors.