Development of an inflammatory tissue‐selective chimeric TNF receptor
Background: Inhibiting TNF‐&agr; is an effective therapy for inflammatory diseases such as rheumatoid arthritis. However, systemic, nondiscriminatory neutralization of TNF‐&agr; is associated with considerable adverse effects. Methods: Here, we developed a trimeric chimeric TNF receptor by linking an N‐terminal mouse Acrp30 trimerization domain and an MMP‐2/9 substrate sequence to the mouse extracellular domain of TNF receptor 2 followed by a C‐terminal mouse tetranectin coiled‐coil domain (mouse Acrp‐MMP‐TNFR‐Tn). Results: Here, we show that the Acrp30 trimerization domain inhibited the binding activity of TNFR, possibly by closing the binding site of the trimeric receptor. Cleavage of the substrate sequence by MMP‐9, an enzyme highly expressed in inflammatory sites, restored the binding activity of the mouse TNF receptor. We also constructed a recombinant human chimeric TNF receptor (human Acrp‐MMP‐TNFR‐Tn) in which an MMP‐13 substrate sequence was used to link the human Acrp and the human TNF receptor 2. Human Acrp‐MMP‐TNFR‐Tn showed reduced binding activity, and MMP‐13 digestion recovered its binding activity with TNF‐&agr;. Conclusion: Acrp‐masked chimeric TNF receptors may be able to be used for inflammatory tissue‐selective neutralization of TNF‐&agr; to reduce the adverse effects associated with systemic neutralization of TNF‐&agr;.