Monoclonal C5-1 antibody produced in transgenic alfalfa plants exhibits a N-glycosylation that is homogenous and suitable for glyco-engineering into human-compatible structures

Structural analysis of the N-glycosylation of alfalfa proteins was investigated in order to evaluate the capacity of this plant to perform this biologically important post-translational modification. We show that, in alfalfa, N-linked glycans are processed into a large variety of mature oligosaccharides having core-xylose and core alpha(1,3)-fucose, as well as terminal Lewis(a) epitopes. In contrast, expression of the C5-1 monoclonal antibody in alfalfa plants results in the production of plant-derived IgG(1) which is N-glycosylated by a predominant glycan having a alpha(1,3)-fucose and a beta(1,2)-xylose attached to a GlcNAc(2)Man(3)GlcNAc(2) core. Since this core is common to plant and mammal N-linked glycans, it therefore appears that alfalfa plants have the ability to produce recombinant IgG(1) having a N-glycosylation that is suitable for in vitro or in vivo glycan remodelling into a human-compatible plantibody. For instance, as proof of concept, in vitro galactosylation of the alfalfa-derived C5-1 mAb resulted in a homogenous plantibody harbouring terminal beta(1, 4)-galactose residues as observed in the mammalian IgG.