Immunization with mimotopes prevents growth of carcinoembryonic antigen positive tumors in BALB/c mice.
OBJECTIVE
The carcinoembryonic antigen (CEA) is a glycoprotein that is overexpressed in nearly 50% of all human and veterinarian tumors. At present, anti-CEA antibodies are being tested in clinical studies as passive immunotherapeutics. This study aims to establish an active immunotherapy for the poorly immunogenic CEA glycoprotein by generating antigen surrogates.


METHODS
We used the monoclonal anti-CEA antibody Col-1 and the biopanning method to generate peptide mimics (mimotopes) of the Col-1 epitope. The peptide showing the highest specificity and mimicry was synthesized as an octameric multiple antigenic mimotope (MAM). Subsequently, immunogenicity of the selected mimotope was examined in BALB/c mice. We assessed antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity mediated by the induced antibodies on CEA-expressing HT29 tumor cells. Furthermore, after immunization, the BALB/c mice were transplanted s.c. with Meth-A/CEA tumor cells.


RESULTS
When BALB/c mice were immunized with this MAM, they generated a specific humoral immune response against CEA. The mimotope-induced polyclonal and poly-isotypic antibodies induced antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity in vitro. Furthermore, when MAM-immunized mice were transplanted s.c. with Meth-A/CEA cells expressing human CEA, a suppressed tumor growth was observed.


CONCLUSIONS
From our results, we can conclude that the Col-1 epitope of the glycoprotein CEA can be translated into an immunogenic peptide mimic. The mimotope-induced antibodies recognize CEA and do effectively inhibit growth of CEA-positive tumors. Based on these finding, we suggest that the generated mimotopes are candidates for active immunotherapy of CEA-expressing tumors.
Brämswig
Kira H
KH
Department of Pathophysiology, Medical University Vienna, Vienna, Austria.
Knittelfelder
Regina
R
Gruber
Silke
S
Untersmayr
Eva
E
Riemer
Angelika B
AB
Szalai
Krisztina
K
Horvat
Reinhard
R
Kammerer
Robert
R
Zimmermann
Wolfgang
W
Zielinski
Christoph C
CC
Scheiner
Otto
O
Jensen-Jarolim
Erika
E
D000818:Animals; D000951:Antigens, Neoplasm / Q000737:chemistry; D002272:Carcinoembryonic Antigen / Q000737:chemistry*; D015195:Drug Design; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000737:chemistry; D015972:Gene Expression Regulation, Neoplastic; D006023:Glycoproteins / Q000737:chemistry; D007107:Immune System; D007167:Immunotherapy / Q000379:methods*; D051379:Mice; D008807:Mice, Inbred BALB C; D008856:Microscopy, Fluorescence; D009368:Neoplasm Transplantation; D019151:Peptide Library; D010455:Peptides / Q000737:chemistry; D010802:Phylogeny
D000951:Antigens, Neoplasm; D002272:Carcinoembryonic Antigen; D000939:Epitopes; D006023:Glycoproteins; D019151:Peptide Library; D010455:Peptides