Immunity against a therapeutic xenoprotein/Fc construct delivered by gene transfer is reduced through binding to the inhibitory receptor Fc[gamma]RIIb

• Published in: The journal of gene medicine 2011-09, Vol.13 (9), p.470
• Main Authors: Liang, Yaming, Qiu, Hongmin, Glinka, Yelena, Lazarus, Alan H, Ni, Heyu, Prud'homme, Gerald J, Wang, Qinghua
• Format: Article
• Language: English
• Subjects: Gene therapy
• ISSN: 1099-498X; 1521-2254
• DOI: 10.1002/jgm.1598

Background Therapeutic xenoproteins are immunogenic and can induce neutralizing antibodies. When delivered by intramuscular injection of a plasmid vector, this mimics classical DNA vaccination. To demonstrate this, we chose Exendin-4 (Ex4), which is a glucagon-like peptide-1 mimetic xenoprotein in clinical use for treating type 2 diabetes. We constructed an Ex4 and mouse immunoglobulin (Ig)G1-Fc fusion fragment (Ex4/Fc), and hypothesized that it would have minimal immunogenicity as a result of its capacity to bind the inhibitory Fc receptor Fc[gamma]RIIb expressed by B lymphocytes. Methods Plasmid vectors encoding Ex4/Fc constructs, with wild-type or mutant Fc, were injected intramuscularly into mice, and local electroporation was applied to enhance gene transfer. Gene transfer was performed in both wild-type and Fc[gamma]RIIb knockout mice. Antibody production was detected in serum by an enzyme-linked immunosorbent assay. Results Recombinant Ex4/Fc bound only to B cells expressing Fc[gamma]RIIb. This binding was dependent on a motif in the Fc region, which we mutated to abolish binding (Ex4/Fcmut). Ex4 antibody was detected in mice treated with Ex4, as well as Ex4/Fcmut, but not in those treated with Ex4/Fc. Thus, wild-type Fc was associated with reduced immunogenicity. To confirm this was related to the presence of inhibitory Fc receptors, we also performed experiments in Fc[gamma]RIIb-null mice. Mice lacking this receptor produced antibodies against all Ex4 constructs, including the wild-type Fc (Ex4/Fc). Conclusions The present study shows that inhibitory Fc[gamma]RIIb receptors interacting with the wild-type IgG1-Fc reduce immunity against Ex4/Fc, suggesting an approach for reducing the immunogenicity of therapeutic proteins in the context of gene therapy. Copyright © 2011 John Wiley & Sons, Ltd.