Studies on the Removal of Abnormal Prion Protein by Processes Used in the Manufacture of Human Plasma Products

Abstract

Background and Objectives: To identify if any process steps used in plasma fractionation may have a capability of removing agents of human transmissible spongiform encephalopathy (TSE). Materials and Methods: Sixteen fractionation steps were investigated separately by adding a preparation of hamster adapted scrapie 263K to the starting material at each process step and determining the distribution into resultant fractions of protease–K–resistant (abnormal) prion protein by Western blot analysis. Results: A number of process operations were found to remove abnormal prion protein to the limit of detection of the assay. These were cold ethanol precipitation of fraction IV (log reduction, LR, ≥3.0) and a depth filtration (LR ≥4.9) in the albumin process; cold ethanol fraction I+III precipitation (LR ≥3.7) and a depth filtration (LR ≥2.8) in the immunoglobulin processes and adsorption with DEAE–Toyopearl 650M ion exchanger (LR ≥3.5) in the fibrinogen process. In addition, a substantial degree of removal of abnormal prion protein was observed across DEAE–Toyopearl 650M ion exchange (LR = 3.1) used in the preparation of factor–VIII concentrate; DEAE–cellulose ion exchange (LR = 3.0) and DEAE–sepharose ion exchange (LR = 3.0) used in the preparation of factor–IX concentrates and S–sepharose ion exchange (LR = 2.9) used in the preparation of thrombin. Conclusions: Plasma fractionation processes used in the manufacture of albumin, immunoglobulins, factor–VIII concentrate, factor–IX concentrates, fibrinogen and thrombin all contain steps which may be capable of removing causative agents of human TSEs.

Long-term efficacy and safety of a pasteurized, plasma-derived factor VIII concentrate (Beriate® P) in patients with haemophilia A

“…To minimize the risk of viral transmission, human plasma-derived clotting products undergo several production steps that effectively reduce prion load [14][15][16] by N10 log 10 [17]. This increased safety also keeps the theoretical risk of transmitting prions and their associated diseases such as vCJD as small as possible.…”

Passive Immunization against Congenital Cytomegalovirus Infection: Current State of Knowledge

“…In addition, highly elaborate manufacturing processes have been established for plasma-derived pharmaceutical products, which practically exclude contamination with viruses or prions. Today, these processes include virus inactivation and removal steps such as cold-ethanol fractioning, solvent-detergent treatment, incubation at low pH, pasteurization, and nanofiltration, all of which, taken separately, are demonstrably capable of reducing model viruses and prions by several orders of magnitude from baseline [76,77,78]. …”

Factor VIII and transmissible spongiform encephalopathy: the case for safety

“…A 4 log 10 ID 50 reduction of TSE infectivity during the manufacturing of the FVIII concentrate, Liberate Ò was shown. In a subsequent large experimental study Foster et al [108] showed a 6.8 log 10 cumulative reduction of abnormal PrP by four main steps (cryoprecipitation, precipitation and adsorption of cryoprecipitate extract, ion exchange chromatography and membrane filtration) used in the production of FVIII. Some of these same issues have been addressed in an extensive study conducted recently by Aventis Behring [109].…”