Development of lamprey-derived antibodies against human blood group antigens

A major challenge in the glycosciences is the scarcity of sensitive and specific glycan-binding reagents, such as monoclonal antibodies, for detecting and isolating glycans. Here we report the development and characterization of new monoclonal antibodies (mAbs) that bind carbohydrate-based red blood cell (RBC) antigens including the ABO(H) antigens. This approach exploits the immune system of the sea lamprey (Petromyzon marinus), which strongly responds to human glycans to enable the generation of high affinity antibodies. To develop these mAbs, we immunized the lamprey with RBCs and designed a targeted antibody enrichment and screening process using intact RBCs and a custom microarray displaying blood group antigens. Through multiple rounds of enrichment and testing we identified two mAbs; A_25 and A_39. Glycan binding analysis of the mAbs using glycan microarrays, the Luminex platform and western blot analysis revealed their binding to H antigens and terminal N-acetyllactosamine Galβ1-4GlcNAc (LacNAc, a type 2 sequence). Mechanistic insights into antigen specificity were gained through glycan inhibition assays, sequence homology analysis, and nanomolar-range affinity measurements. mAb binding to RBCs was determined using flow cytometry. Both mAbs bound RBCs of all ABO blood groups, whereas strongest binding was observed for blood group O RBCs. Our findings highlight the efficacy of the lamprey system to develop glycan-specific mAbs. These reagents allow investigation of expression of the H antigen and LacNAc-containing glycans in human tissues. In the future, they could also be modified using molecular engineering techniques to generate mAbs specific to other understudied blood group antigens.