Large-scale purification of factor VIII by affinity chromatography: optimization of process parameters

Affinity chromatography in the industrial purification of plasma proteins for therapeutic use

Affinity chromatography is a powerful technique for the purification of many proteins in human plasma. Applications cover the isolation of proteins for research purposes but also, to a large extent, for the production of therapeutic products. In industrial plasma fractionation, affinity chromatography has been found to be particularly advantageous for fine and rapid capture of plasma proteins from industrial plasma fractions pre-purified by ethanol fractionation or by ion-exchange chromatography. To date, affinity chromatography is being used in the production of various licensed therapeutic plasma products, such as the concentrates of Factor VIII, Factor IX, von Willebrand Factor, Protein C, Antithrombin III, and Factor XI. Most commonly used ligands are heparin, gelatin, murine antibodies, and, to a lesser extent, Cu(2+). Possible development of the use of affinity chromatography in industrial plasma fractionation should be associated to the current development of phage display and combinatorial chemistry. Both approaches may lead to the development of tailor-made synthetic ligands that would allow implementation of protein capture technology, providing improved productivity and yield for plasma products.

Essential role of the concentration of immobilized ligands in affinity chromatography: purification of guanidinobenzoatase on an ionized ligand

Guanidinobenzoatase, a plasma protein with possible application as a 'tumor marker', has been fully purified by one-step affinity chromatography. The affinity matrix was prepared by 'controlled' immobilization of an enzyme inhibitor (agmatine) onto commercial agarose gels containing carboxyl moieties activated as N-hydroxysuccinimide esters. In this way, agmatine becomes immobilized through an amido bond and preserves an ionized guanidino moiety. Different matrices with different concentration of ligands were prepared in order to evaluate their properties as affinity supports. Interestingly, matrices with a very low concentration of immobilized ligands (2 microlmol/ml, corresponding to the modification of only 5% of active groups in the commercial resins) exhibited a low capacity for unspecific adsorption of proteins (as anion-exchange resins) and displayed also a high capacity for specific adsorption of our target protein. On the other hand, when affinity matrices possessed a moderate concentration of agmatine (10 micromol/ml of gel or higher), two undesirable phenomena were observed: (a) the matrix behaves as a very good anionic exchange support able to non-specifically adsorb most of plasma proteins and (b) the specific adsorption of our target protein becomes much lower. The latter phenomenon could be due to steric hindrances promoted by the interaction between each individual immobilized ligand and the corresponding binding pocket in the target protein. These hindrances could also be promoted by the presence of a fairly dense layer of immobilized ligands covering the support surface, thus preventing interactions between immobilized ligands and partially buried protein-binding pockets. In this way, a successful affinity purification (23.5% yield, x220 purification factor, a unique electrophoretic band) could be achieved by combination of three approaches: (i) the use of affinity matrices possessing a very low density of immobilized ligands, (ii) performing affinity adsorption at high ionic strength and (iii) performing specific desorption with substrates or substrate analogues.

Isolation of the factor VIII-von Willebrand factor complex directly from plasma by gel filtration

A high capacity gel filtration system was developed with the purpose of isolating factor VIII (FVIII) and von Willebrand factor (vWF) directly from plasma in significantly higher yields than obtained by cryoprecipitation, the technique most commonly used to recover FVIII-vWF from human plasma. After laboratory-scale gel filtration of plasma, a FVIII-containing fraction was collected containing about 90% of FVIII in the applied plasma and with almost tenfold higher purity than that obtained by cryoprecipitation. The gel filtration step has been scaled up for use as the initial step in the manufacturing process for a FVIII preparation (Nordiate).

Application of bioaffinity technology in therapeutic extracorporeal plasmapheresis and large-scale fractionation of human plasma

This paper describes the increasingly unique and powerful role that affinity chromatography is occupying both as a tool for the treatment of extracorporeal plasma exchange (to discard biological compounds with noxious metabolic or immunologic effects in patients) and as a purification tool in the production of therapeutic plasma protein derivatives. Management of both applications requires careful monitoring of the parameters applied to the plasma material, to avoid immunological stimulation or activation of the coagulation cascade. Examples of direct current applications of affinity ligands in therapeutic removal and industrial production of plasma compounds are presented.

The affinity technology in downstream processing

The quality criteria imposed on several biochemicals are stringent, thus, high-separation purification technology is important to downstream processing. Affinity-based purification technologies are regarded as the finest available, and each one differs in its purifying ability, economy, processing speed and capacity. The most widely used affinity technology is classical affinity chromatography, however, other chromatography-based approaches have also been developed, for example, perfusion affinity chromatography, hyperdiffusion affinity chromatography, high-performance affinity chromatography, centrifugal affinity chromatography, affinity repulsion chromatography, heterobifunctional ligand affinity chromatography and the various chromatographic applications of 'affinity tails'. On the other hand, non-chromatographic affinity technologies aim at high throughput and seek to circumvent problems associated with diffusion limitations experienced with most chromatographic packings. Continuous affinity recycle extraction, aqueous two-phase affinity partitioning, membrane affinity filtration, affinity cross-flow ultrafiltration, reversible soluble affinity polymer separation and affinity precipitation are all non-chromatographic technologies. Several types of affinity ligands are used to different extents; antibodies and their fragments, receptors and their binding substances, avidin/biotin systems, textile and biomimetic dyes, (oligo)peptides, antisense peptides, chelated metal cations, lectins and phenylboronates, protein A and G, calmodulin, DNA, sequence-specific DNA, (oligo)nucleotides and heparin. Likewise, there are several support types developed and used; natural, synthetic, inorganic and composite materials.

Direct capture of plasma factor VIII:C by ion exchange chromatography

An ion exchange medium, DEAE-Fractogel 650M, can be used to capture factor VIII (FVIII) directly from plasma. Previous reports have focussed on the use of this medium to capture FVIII from cryoprecipitate. In this report, citrate phosphate dextrose plasma was batch-stirred with DEAE-Sephadex A50, filtered, diluted, loaded onto a column packed with DEAE-Fractogel TSK 650M, and chromatographed. Most of the unwanted proteins flowed through the gel unadsorbed. Bound FVIII was eluted by increasing the ionic strength of the buffer. A citrate-based buffer gave an overall FVIII:C yield of 670 IU/kg plasma with a specific activity of 0.68 IU FVIII:C/mg protein. This process gave a higher yield of FVIII:C but significantly more prothrombin complex factors than cryoprecipitation. This method is a promising alternative to cryoprecipitation of FVIII.