Effective phagocytosis of low Her2 tumor cell lines with engineered, aglycosylated igg displaying high FcγRIIa affinity and selectivity

Sang Taek Jung, William Kelton, Tae Hyun Kang, Daphne T.W. Ng, Jan Terje Andersen, Inger Sandlie, Casim A. Sarkar, George Georgiou

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)

Abstract

Glycans anchored to residue N297 of the antibody IgG Fc domain are critical in mediating binding toward FcγRs to direct both adaptive and innate immune responses. However, using a full length bacterial IgG display system, we have isolated aglycosylated Fc domains with mutations that confer up to a 160-fold increase in the affinity toward the low affinity FcγRIIa-R131 allele as well as high selectivity against binding to the remarkably homologous human inhibitory receptor, FcγRIIb. The mutant Fc domain (AglycoT-Fc1004) contained a total of 5 amino acid substitutions that conferred an activating to inhibitory ratio of 25 (A/I ratio; FcyRIIa-R131:FcγRIIb). Incorporation of this engineered Fc into trastuzumab, an anti-Her2 antibody, resulted in a 75% increase in tumor cell phagocytosis by macrophages compared to that of the parental glycosylated trastuzumab with both medium and low Her2-expressing cancer cells. A mathematical model has been developed to help explain how receptor affinity and the A/I ratio relate to improved antibody dependent cell-mediated phagocytosis. Our model provides guidelines for the future engineering of Fc domains with enhanced effector function.

Original languageEnglish
Pages (from-to)368-375
Number of pages8
JournalACS Chemical Biology
Volume8
Issue number2
DOIs
Publication statusPublished - 2013 Feb 15

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Medicine

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