Purification of α1-antichymotrypsin from human plasma with recombinant M. catarrhalis ubiquitous surface protein A1

Alpha 1-antichymotrypsin (ACT) inhibits chymotrypsin-like enzymes, particularly neutrophil cathepsin G. Moreover, ACT in its native form suppresses chemotaxis of neutrophils and decreases neutrophil production of superoxide radicals. We recently showed that Moraxella catarrhalis ubiquitous surface protein (Usp) A1 is able to specifically bind ACT in the context of a novel virulence mechanism. In this study, we report that recombinant UspA1557–704 coupled to CNBr-Sepharose can be used in a simple one-step purification of ACT from human plasma. UspA1557–704-purified ACT remains intact and active as shown by binding to M. catarrhalis and a chymotrypsin inhibition assay. The novel method for ACT isolation from plasma has important advantages in simplicity and time as compared to conventional methods.