Enhanced potency of a fucose-free monoclonal antibody being developed as an Ebola virus immunoprotectant

• Published in: Proceedings of the National Academy of Sciences - PNAS 2011-12, Vol.108 (51), p.20690-20694
• Main Authors: Zeitlin, Larry, Pettitt, James, Scully, Corinne, Bohorova, Natasha, Kim, Do, Pauly, Michael, Hiatt, Andrew, Ngo, Long, Steinkellner, Herta, Whaley, Kevin J., Olinger, Gene G.
• Format: Article
• Language: English
• Subjects: Animals; Antibodies; Antibodies, Monoclonal - chemistry; Antiviral Agents - chemistry; Biological Sciences; CHO cells; Complement C1q - chemistry; Ebola virus; Ebolavirus - immunology; Ebolavirus - metabolism; Female; Filovirus; Fucose - chemistry; Fucose - immunology; Glycoproteins; Glycosylation; Hemorrhagic Fever, Ebola - immunology; Hemorrhagic Fever, Ebola - prevention & control; Humans; Immune System; Immunization, Passive; Medical treatment; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Molecular Sequence Data; Monoclonal antibodies; Mutation; Natural killer cells; Nicotiana; Polysaccharides; Receptors; Rodents; Surface Plasmon Resonance; Viruses
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1108360108

No countermeasures currently exist for the prevention or treatment of the severe sequelae of Filovirus (such as Ebola virus; EBOV) infection. To overcome this limitation in our biodefense preparedness, we have designed monoclonal antibodies (mAbs) which could be used in humans as immunoprotectants for EBOV, starting with a murine mAb (13F6) that recognizes the heavily glycosylated mucin-like domain of the virion-attached glycoprotein (GP). Point mutations were introduced into the variable region of the murine mAb to remove predicted human T-cell epitopes, and the variable regions joined to human constant regions to generate a mAb (h-13F6) appropriate for development for human use. We have evaluated the efficacy of three variants of h-13F6 carrying different glycosylation patterns in a lethal mouse EBOV challenge model. The pattern of glycosylation of the various mAbs was found to correlate to level of protection, with aglycosylated h-13F6 providing the least potent efficacy (ED50 = 33 μg). A version with typical heterogenous mammalian glycoforms (ED50 = 11 μg) had similar potency to the original murine mAb. However, h-13F6 carrying complex N-glycosylation lacking core fucose exhibited superior potency (ED50 = 3 μg). Binding studies using Fcγ receptors revealed enhanced binding of nonfucosylated h-13F6 to mouse and human FcγRIII. Together the results indicate the presence of Fc N-glycans enhances the protective efficacy of h-13F6, and that mAbs manufactured with uniform glycosylation and a higher potency glycoform offer promise as biodefense therapeutics.