Kinetic and affinity constants of epitope specific anti-carcinoembryonic antigen (CEA) monoclonal antibodies for CEA and engineered CEA domain constructs.
BACKGROUND
Carcinoembryonic antigen (CEA) is a human tumor antigen with the domain structure N-A1-B1-A2-B2-A3-B3, in which each domain is predicted to have an Ig-like fold and is known to bind epitope specific anti-CEA antibodies.


OBJECTIVE
To determine the affinity constants of several domain specific anti-CEA antibodies using purified recombinant or synthetic domains.


CONCLUSIONS
We have determined the kinetic and affinity constants of several anti-CEA antibodies for CEA, CEA domains (A3-B3) expressed in HeLa cells, and a synthetic peptide corresponding to the A3 domain using a BIAcore biosensor. There was no difference in affinity for CEA among a murine (mT84.66), a mouse/human chimeric form (cT84.66) or a disulfide deleted version (delta SScT84.66) of this antibody. There was less than a five-fold drop in affinity of murine T84.66 for the A3-B3 domain expressed in HeLa cells compared to CEA. The synthetic A3 domain had an affinity constant for mT84.66 which was ten-fold less than for CEA. The affinity constants for CEA with several other anti-CEA monoclonal antibodies, including three antibodies which have almost identical CDR sequences (CEA.281, CEA.11 and CEM231) were also determined. CEM231 which had a two-fold higher affinity constant for CEA than either CEA.281 or CEA.11 had a two-fold faster on-rate which accounts for its higher affinity constant. This difference may be due to one or more of the amino acid differences present in H1 (N vs. S or D) and H3 (A vs. V).
Hefta
L J
LJ
Division of Immunology, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA.
Neumaier
M
M
Shively
J E
JE
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000493:pharmacokinetics*; D000915:Antibody Affinity; D000937:Antigen-Antibody Reactions / Q000276:immunology; D002272:Carcinoembryonic Antigen / Q000737:chemistry* / Q000235:genetics / Q000276:immunology*; D000939:Epitopes; D005818:Genetic Engineering; D006801:Humans; D007135:Immunoglobulin Variable Region / Q000737:chemistry; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary
D000911:Antibodies, Monoclonal; D002272:Carcinoembryonic Antigen; D000939:Epitopes; D007135:Immunoglobulin Variable Region