title: Identification of kallikrein and FXIa as impurities in therapeutic immunoglobulins: implications for the safety and control of intravenous blood products.
abstract: OBJECTIVE
  The occurrence of thromboembolic events (TEEs) with intravenous immunoglobulin lots (IVIGs) raised the question of the causative agent for these adverse events. We investigated the predominant plasma proteases in 19 IVIG lots from five manufacturers including three lots associated with adverse events.
  
  
  METHODS
  The inhibitor profile of the amidolytic activity in IVIG lots was investigated with substrates S-2302 and S-2288. In immunocapture assays, prekallikrein and FXI antigen and respective active proteases were quantified. Non-activated partial thromboplastin time (NAPTT) and a modified FXIa PTT served as global and FXIa-specific clotting assays, respectively.
  
  
  RESULTS
  Kallikrein was identified as one major contaminant activity in IVIGs. A second activity was seen in some IVIGs with substrate S-2288, but not with S-2302. Inhibition studies excluded FXIIa, thrombin or plasmin as contaminant activity. FXI antigen was seen in all 19 IVIG lots, and FXIa activity was found as second major impurity in some IVIGs, including all lots involved in TEEs. FXIa highly correlated with a short clotting time in NAPTT.
  
  
  CONCLUSIONS
  Kallikrein and FXIa are the major contaminants in IVIGs. FXIa was highly procoagulant, with highest level in TEE-associated IVIGs. Since the NAPTT unambiguously identified FXIa procoagulant activity in IVIGs, its implementation as a release test would improve the safety of IVIGs.
authors.affiliation: Department of Haematology/Transfusion Medicine, Paul Ehrlich Institute, Langen, Germany. etsmi@pei.de
authors.forename: M
authors.initials: M
authors.lastname: Etscheid
authors.forename: S
authors.initials: S
authors.lastname: Breitner-Ruddock
authors.forename: S
authors.initials: S
authors.lastname: Gross
authors.forename: A
authors.initials: A
authors.lastname: Hunfeld
authors.forename: R
authors.initials: R
authors.lastname: Seitz
authors.forename: J
authors.initials: J
authors.lastname: Dodt
mesh_terms: D001777:Blood Coagulation; D004305:Dose-Response Relationship, Drug; D004340:Drug Contamination; D064420:Drug-Related Side Effects and Adverse Reactions; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D015956:Factor XIIa / Q000032:analysis; D015945:Factor XIa / Q000032:analysis*; D005341:Fibrinolysin / Q000032:analysis; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry* / Q000627:therapeutic use*; D016756:Immunoglobulins, Intravenous / Q000737:chemistry / Q000627:therapeutic use*; D007610:Kallikreins / Q000032:analysis*; D010314:Partial Thromboplastin Time; D011288:Prekallikrein / Q000032:analysis; D013917:Thrombin / Q000032:analysis; D013923:Thromboembolism / Q000276:immunology
chemical_list: D007136:Immunoglobulins; D016756:Immunoglobulins, Intravenous; D011288:Prekallikrein; D007610:Kallikreins; D015945:Factor XIa; D015956:Factor XIIa; D013917:Thrombin; D005341:Fibrinolysin