AUTHOR=Kreft Luisa , Schepers Aloys , Hils Miriam , Swiontek Kyra , Flatley Andrew , Janowski Robert , Mirzaei Mohammadali Khan , Dittmar Michael , Chakrapani Neera , Desai Mahesh S. , Eyerich Stefanie , Deng Li , Niessing Dierk , Fischer Konrad , Feederle Regina , Blank Simon , Schmidt-Weber Carsten B. , Hilger Christiane , Biedermann Tilo , Ohnmacht Caspar TITLE=A novel monoclonal IgG1 antibody specific for Galactose-alpha-1,3-galactose questions alpha-Gal epitope expression by bacteria JOURNAL=Frontiers in Immunology VOLUME=13 YEAR=2022 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2022.958952 DOI=10.3389/fimmu.2022.958952 ISSN=1664-3224 ABSTRACT=

The alpha-Gal epitope (α-Gal) with the determining element galactose-α1,3-galactose can lead to clinically relevant allergic reactions and rejections in xenotransplantation. These immune reactions can develop because humans are devoid of this carbohydrate due to evolutionary loss of the enzyme α1,3-galactosyltransferase (GGTA1). In addition, up to 1% of human IgG antibodies are directed against α-Gal, but the stimulus for the induction of anti-α-Gal antibodies is still unclear. Commensal bacteria have been suggested as a causal factor for this induction as α-Gal binding tools such as lectins were found to stain cultivated bacteria isolated from the intestinal tract. Currently available tools for the detection of the definite α-Gal epitope, however, are cross-reactive, or have limited affinity and, hence, offer restricted possibilities for application. In this study, we describe a novel monoclonal IgG1 antibody (27H8) specific for the α-Gal epitope. The 27H8 antibody was generated by immunization of Ggta1 knockout mice and displays a high affinity towards synthetic and naturally occurring α-Gal in various applications. Using this novel tool, we found that intestinal bacteria reported to be α-Gal positive cannot be stained with 27H8 questioning whether commensal bacteria express the native α-Gal epitope at all.