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

✍ Scribed by Yaming Liang; Hongmin Qiu; Yelena Glinka; Alan H. Lazarus; Heyu Ni; Gerald J. Prud'homme; Qinghua Wang

• Publisher: John Wiley and Sons
• Year: 2011
• Tongue: English
• Weight: 338 KB
• Volume: 13
• Category: Article
• ISSN: 1099-498X
• DOI: 10.1002/jgm.1598

✦ Synopsis

Abstract

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 FcγRIIb 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 FcγRIIb knockout mice. Antibody production was detected in serum by an enzyme‐linked immunosorbent assay.

Results

Recombinant Ex4/Fc bound only to B cells expressing FcγRIIb. 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 FcγRIIb‐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 FcγRIIb 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.