The Thomsen-Friedenreich antigen (TF; CD176, Galβ1-3GalNAcα-) is a tumor-specific carbohydrate antigen and a promising therapeutic target. Antibodies that react with this antigen are frequently found in the sera of healthy adults and are assumed to play a role in cancer immunosurveillance. In this study, we examined the occurrence of α-anomeric TF (TFα) on a large variety of gastrointestinal bacteria using a novel panel of well-characterized monoclonal antibodies. Reactivity with at least one anti-TF antibody was found in 13% (16 of 122) of strains analyzed. A more in-depth analysis, using monoclonal antibodies specific for α- and β-anomeric TF in combination with periodate oxidation, revealed that only two novel Bacteroides ovatus strains (D-6 and F-1), isolated from the faeces of healthy persons by TF-immunoaffinity enrichment, possessed structures that are immunochemically identical to the true TFα antigen. The TF-positive capsular polysaccharide structure of strain D-6 was characterized by mass spectrometry, monosaccharide composition analysis, glycosidase treatments and immunoblot staining with TFα- and TFβ-specific antibodies. The active antigen was identified as Galβ1-3GalNAc-, which was α-anomerically linked as a branching structure within a heptasaccharide repeating unit. We conclude that structures immunochemically identical to TFα are extremely rare on the surface of human intestinal bacteria and may only be identifiable by binding of both antibodies, NM-TF1 and NM-TF2, which recognize a complete immunomolecular imprint of the TFα structure. The two novel B. ovatus strains isolated in this study may provide a basis for the development of TF-based anti-tumor vaccines.
cancer, Bacteroides ovatus, CD176, gastrointestinal bacteria, Thomsen-Friedenreich antigen
NCBI PubMed ID: 21551457Publication DOI: 10.1093/glycob/cwr058Journal NLM ID: 9104124Publisher: IRL Press at Oxford University Press
Correspondence: steffen.goletz@glycotope.com
Institutions: Department of Gastrointestinal Microbiology, German Institute of Human Nutrition, Potsdam-Rehbrücke (DIfE), Arthur-Scheunert-Allee 114-116, D-14558 Nuthetal, Germany, Glycotope GmbH, Robert-Rössle-Str. 10, D-13125 Berlin, Germany, Institute for Biochemistry and Molecular Biology, Charité - University Medicine Berlin, Arnimallee 22, D-14195 Berlin, Germany
Methods: periodate oxidation, SDS-PAGE, sugar analysis, ELISA, MALDI-TOF MS, serological methods, genetic methods, immunoblotting, ESI-IT-MS
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