Tumor necrosis factor (TNF) is a pro-inflammatory cytokine that plays a critical role in many inflammatory diseases. Soluble TNF can be neutralized by monoclonal antibodies (mAbs), and this is a widely-used therapeutic approach. However, some patients do not respond to anti-TNF therapy due to the increased expression of CD64 on monocytes and macrophages. A recent study has shown that CD64 captures anti-TNF mAbs via their Fcγ domain, which induces the transcription of pro-inflammatory genes. Specific blocking of CD64 could therefore be a promising strategy to improve the response to anti-TNF therapy. We used the CD64-specific antibody fragment H22(scFv) and tested its activity against the human CD64(+) cell line HL-60. When stimulated with interferon gamma (IFN-γ), these cells represent a pro-inflammatory phenotype of the monocyte/macrophage lineage. We found that H22(scFv) binds selectively to and blocks CD64, preventing the capture of anti-TNF mAb. Importantly, H22(scFv) itself does not induce CD64 activation. We also found that transmembrane TNF on HL-60 cells stimulated with IFN-γ also contributes to the capture of anti-TNF mAb, although via their Fab domain. In conclusion, the specific blocking of CD64 by H22(scFv) could be used a possible anti-inflammatory mechanism for potentiating the effect of anti-TNF antibodies.
Keywords: AD, atopic dermatitis; ADCC, antibody-dependent cell-mediated cytotoxicity; CD64; CDC, complement-dependent cellular cytotoxicity; Fcγ, fragment crystallizable gamma; H22; IBD, inflammatory bowel disease; IFN-γ, interferon gamma; RA, rheumatoid arthritis; SDS-PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis; TNF; TNF, tumor necrosis factor; aglycoIgG1, aglycosylated IgG1; chronic inflammation; immunotherapy; mAb(s), monoclonal antibodie(s); mTNF, transmembrane tumor necrosis factor; monoclonal antibodies; scFv, single chain fragment variable.