Potential sources for the large scale production of human protein C

Abstract

The vitamin K-dependent family of proteins (VKDs) include prothrombin, factors VII, IX, and X, and protein C (hPC) is synthesized in the liver and act to maintains normal hemostasis. such as properly regulated clotting. An imbalance of any of these pro- or anti-clotting proteins result in hemophilia or disseminated intravascular clotting diseases. Therefore, these proteins have a significant therapeutic value. Many of these proteins are not available in sufficient quantity due to the trace amounts found in plasma and limitations encountered with downstream recovery. Protein C, a major regulatory protein of thrombosis and hemostasis, has a potent anticoagulant activity and can be used as an anti-thrombotic agent. The technology for isolating hPC from human plasma is challenged by; (1) its low concentration in plasma, (2) the limited availability of plasma, (3) similar physicochemical characteristics among VKD plasma proteases, and (4) the risk of transmitting viruses such as the human immunodeficiency virus (HIV). This work focuses on the isolation of protein C from alternative sources for the large-scale production and downstream recovery of highly purified and biologically active hPC. The partial characterization of the protein with respect to post-translational modifications which are essential for functionally active, was also evaluated. Several studies were undertaken:

Cohn Fraction IV-I, an off-line discard stream during traditional plasma fractionation process is introduced as an affordable starting material for the large-scale production of hPC. More than 90 percent of the total protein C antigen detected in the various Cohn fractions was found to reside in fraction IV-I. The protein C isolated from Cohn IV-I paste using a metal-dependent monoclonal antibody to hPC was found to be biologically active.

Recombinant production of hPC in the milk of transgenic pigs, achieved by targeting the synthesis of the protein to the mammary gland, is presented as a model bioreactor system for the synthesis and downstream recovery of complex human proteins. Two major populations of biologically active recombinant hPC (rhPC) were detected and immunopurified by employing conformation specific metal-dependent monoclonal antibodies in the immunopurification process. A high performance thin layer chromatography method was also developed for the detection of total carbohydrate compositions in protein C.