title: A new approach for the detection and identification of protein impurities using combinatorial solid phase ligand libraries.
abstract: We propose a novel method for detection of protein impurities present in plasma-derived and recombinant purified injectable biopharmaceuticals by enhancing the concentration of protein impurities, in essence "amplifying" their presence to detectable levels. The method is based on the capture of proteins using a combinatorial solid-phase hexapeptides ligand library previously described for the reduction of protein concentration difference in biological fluids. Three proteins have been investigated: Staphylococcus aureus Protein A, expressed in Escherichia coli and supplied as 99% pure, recombinant human albumin, expressed in Pichia pastoris and certified as 95% pure, and therapeutic albumin supplied as 96-98% pure injectable solution. In all cases, after treatment with the ligand libraries, a number of additional polypeptide chains, not visible in the control, could be detected and obtained in sufficient amounts for MS analysis. In the cases of the two recombinant proteins, it could be demonstrated that a number of these polypeptide chains were host cell proteins still present in the purified product. In addition, a substantial number of these spots were found to be cleavage products of the original recombinant DNA species. Such cleavage products were particularly abundant in the recombinant human albumin preparation. From pure injectable serum albumin, a number of human plasma protein impurities were also identified by LC-MS/MS analysis. Treatment with ligand libraries of purified proteins is thus seen as a very powerful method of capture and concentration of host proteins and cleaved products for further analysis to control better the quality of industrial biotechnology products.
authors.affiliation: Ciphergen Biosystems, Cergy-Pontoise, France, Institute FIRC for Molecular Oncology Foundation (IFOM), Via Adamello 16 and European Institute of Oncology (IEO), Via Ripamonti 435, 20129 Milano, Italy.
authors.forename: Fréderic
authors.initials: F
authors.lastname: Fortis
authors.forename: Luc
authors.initials: L
authors.lastname: Guerrier
authors.forename: Liliana B
authors.initials: LB
authors.lastname: Areces
authors.forename: Paolo
authors.initials: P
authors.lastname: Antonioli
authors.forename: Tim
authors.initials: T
authors.lastname: Hayes
authors.forename: Kevin
authors.initials: K
authors.lastname: Carrick
authors.forename: David
authors.initials: D
authors.lastname: Hammond
authors.forename: Egisto
authors.initials: E
authors.lastname: Boschetti
authors.forename: Pier Giorgio
authors.initials: PG
authors.lastname: Righetti
mesh_terms: D000418:Albumins / Q000032:analysis / Q000302:isolation & purification; D002853:Chromatography, Liquid; D020650:Combinatorial Chemistry Techniques; D004926:Escherichia coli / Q000235:genetics; D008024:Ligands; D013058:Mass Spectrometry; D019151:Peptide Library; D010843:Pichia / Q000235:genetics; D011506:Proteins / Q000032:analysis* / Q000302:isolation & purification*; D011994:Recombinant Proteins / Q000032:analysis / Q000302:isolation & purification; D013205:Staphylococcal Protein A / Q000032:analysis / Q000302:isolation & purification
chemical_list: D000418:Albumins; D008024:Ligands; D019151:Peptide Library; D011506:Proteins; D011994:Recombinant Proteins; D013205:Staphylococcal Protein A