Tunable modulation of antibody-antigen interaction by protease cleavage of protein M.

While immunoglobulins find ubiquitous use in biotechnology as static binders, recent developments have created pro-antibodies that enable orthogonal switch-like behavior to antibody function. Previously, peptides with low binding affinity have been genetically fused to antibodies, to proteolytically control binding function by blocking the antigen-binding site. However, development of these artificial blockers requires panning for the right peptide sequences that reversibly affect antigen affinity for each antibody. Instead, a generalizable strategy to achieve dynamic control over antibody affinity may be feasible using Protein M (ProtM) from Mycoplasma genitalium, a newly identified polyspecific immunity evasion protein that is capable of blocking antigen binding for a wide range of antibodies. Using C-terminus truncation to identify ProtM variants that are still capable of binding antibody but not antigen blocking, we created a new way to provide universal masking and unmasking of antigen binding by conditional cleavage of the two distinct antibody-binding and antigen-blocking domains on ProtM by thrombin proteolysis. Becuuse of the high affinity of ProtM towards a large variety of IgG subtypes, this strategy may be used as a universal approach to create pro-antibodies that are conditionally activated by disease-specific proteases such as matrix metalloproteinases (MMPs). This article is protected by copyright. All rights reserved.