Glycan microarray reveal induced IgGs repertoire shift against a dietary carbohydrate in response to rabbit anti-human thymocyte therapy

// Ron Amon 1 , Shani Leviatan Ben-Arye 1 , Limor Engler 1 , Hai Yu 2 , Noha Lim 3 , Ludmilla Le Berre 4,5 , Kristina M. Harris 3 , Mario R. Ehlers 6 , Stephen E. Gitelman 7 , Xi Chen 2 , Jean-Paul Soulillou 4,5,* and Vered Padler-Karavani 1,* 1 Department of Cell Research and Immunology, Tel Aviv University, Tel Aviv, Israel 2 Department of Chemistry, University of California-Davis, Davis, CA, USA 3 Biomarker Discovery Research, Immune Tolerance Network, Bethesda, MD, USA 4 Centre de Recherche en Transplantation et Immunologie UMR 1064, INSERM, Universite de Nantes, Nantes, France 5 Institut de Transplantation Urologie Nephrologie (ITUN), CHU Nantes, Nantes, France 6 Clinical Trials Group, Immune Tolerance Network, San Francisco, CA, USA 7 Division of Pediatric Endocrinology and Diabetes, University of California San Francisco, San Francisco, CA, USA * Co-senior authors Correspondence to: Vered Padler-Karavani, email: // Keywords : antibodies; anti-thymocyte globulin; human; N-glycolylneuraminic acid; sialic acids; Immunology Received : September 19, 2017 Accepted : November 14, 2017 Published : December 11, 2017 Abstract Humans have circulating antibodies against diverse glycans containing N -glycolylneuraminic acid (Neu5Gc) due to function-loss mutation of the CMAH gene. This xenogenic non-human carbohydrate is abundant in red meat, xenografts and biotherapeutics. Low levels of diet-derived Neu5Gc is also present on normal human endothelial cells, and together with anti-Neu5Gc antibodies could potentially mediate “xenosialitis” chronic-inflammation. Rabbit anti-human thymocyte globulin (ATG) is a drug containing polyclonal IgG glycoproteins commonly used as an immunosuppressant in human transplantation and autoimmune diseases. In type-1 diabetes patients, infusion of Neu5Gc-glycosylated ATG caused increased global anti-Neu5Gc response. Here, for the first time we explore changes in anti-Neu5Gc IgG repertoire following the immunization elicited by ATG, compared with the basal antibodies repertoire that reflect exposure to dietary-Neu5Gc. We used glycan microarrays with multiple Neu5Gc-glycans and controls to elucidate eventual differences in ATG-elicited repertoire, before/after ATG administration and track their kinetics (0, 1, 18 and 24 months). Response of all basal-pre-existing Neu5Gc-specific antibodies rapidly increased. This response peaked at one month post-ATG, with enhanced affinity, then resolved at 18–24 months. Induced-antibodies showed expanded diversity and de-novo recognition of different Neu5Gc-glycans, including endogenous glycolipids, that was further validated by affinity-purified anti-Neu5Gc antibodies from patients’ sera. These findings strongly suggest that ATG-induced anti-Neu5Gc IgGs represent a secondary exposure to this dietary carbohydrate-antigen in humans, with immune memory. Given their modified recognition patterns, ATG-evoked anti-Neu5Gc antibodies could potentially mediate biological effects different from pre-existing antibodies.