An antibody produced in tobacco expressing a hybrid β-1,4-galactosyltransferase is essentially devoid of plant carbohydrate epitopes

N-glycosylation of a mAb may have a major impact on its therapeutic merits. Here, we demonstrate that expression of a hybrid enzyme (called xylGaIT), consisting of the N-terminal domain of Arabidopsis thaliana xylosyltra nsf erase and the catalytic domain of human 0-1,4-galactosyltransf erase I (GaIT), in tobacco causes a sharp reduction of N-glycans with potentially immunogenic corebound xylose (Xyl) and fucose (Fuc) residues as shown by Western blot and MALDI-TOF MS analysis. A radioallergosorbent test inhibition assay with proteins purified from leaves of WT and these transgenic tobacco plants using sera from allergic patients suggests a significant reduction of potential immunogenicity of xyl-GaIT proteins. A mAb purified from leaves of plants expressing xylGaIT displayed an N-glycan profile that featured high levels of galactose, undetectable xylose, and a trace of fucose. Hence, a transgenic plant expressing the hybrid GaIT might yield more effective and safer monoclonals for therapeutic purposes than WT plants and even transgenic plants expressing the unchanged GaIT.