Immunological properties of a single-chain fragment of the anti-idiotypic antibody ACA125.
Vaccination with anti-idiotypic antibodies has been described as a promising concept for treatment of several malignant diseases. The murine monoclonal anti-idiotypic antibody ACA125 imitates a specific epitope of the tumor-associated antigen CA125 expressed by 80% of ovarian carcinomas. In the first clinical trial it could be shown that mAb ACA125 is able to elicit anti-anti-idiotypic antibodies (Ab3) with anti-CA125 specificity in patients with advanced ovarian cancer. In order to improve the capabilities of anti-idiotype vaccines we generated a genetically engineered single-chain fragment (scFv) ACA125 composed of heavy- and light-chain variable regions connected by a flexible linker. The antigenicity of scFv ACA125 was demonstrated by immunizing rats i.p. with scFv or complete mAb in complete/incomplete Freund's adjuvants (CFA/IFA) or precipitated by aluminium hydroxide. Negative control groups included applications of irrelevant mouse IgG or adjuvants alone. Anti-anti-idiotypic antibodies (Ab3) directed against the mAb ACA125 as well as specific anti-CA125 antibodies (Ab1') could be detected in all animals treated with scFv in CFA/IFA. Nevertheless, antibody titers were lower than when the complete mAb ACA 125 was used. Suprisingly, an increase of specificity could not be observed in scFv-immunized animals, which had been expected because of the lack of heavy- and light-chain constant regions that could raise rather unspecific anti-isotypic and anti-allotypic rat anti-(mouse Ig) antibodies (RAMA). In contrast, the RAMA responses detected in these rats were even stronger than those following immunization with complete mAb ACA125. In conclusion, the anti-idiotypic scFv ACA125 alone cannot improve the immunogenic features of the corresponding mAb, but provides a useful tool for the further development of genetic vaccines.
Reinartz
S
S
Center of Obstetrics and Gynecology, University of Tuebingen, Germany.
Wagner
U
U
Giffels
P
P
Gruenn
U
U
Schlebusch
H
H
Wallwiener
D
D
D000536:Aluminum Hydroxide / Q000494:pharmacology; D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology*; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000917:Antibody Formation / Q000276:immunology; D000918:Antibody Specificity; D004306:Dose-Response Relationship, Immunologic; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D005260:Female; D005620:Freund's Adjuvant / Q000494:pharmacology; D007074:Immunoglobulin G / Q000276:immunology; D051379:Mice; D010051:Ovarian Neoplasms / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D000536:Aluminum Hydroxide; D005620:Freund's Adjuvant