Partitioning of human and sheep forms of the pathogenic prion protein during the purification of therapeutic proteins from human plasma.
BACKGROUND
Therapeutic proteins derived from human plasma and other biologic sources have demonstrated an excellent safety record relative to the potential threat of transmissible spongiform encephalopathy (TSE) transmission. Previously, hamster-adapted scrapie was used as a model agent to assess TSE clearance in purification steps leading to the isolation of biopharmaceutical proteins. The current study investigated the validity of hamster scrapie as a model for human TSE clearance studies. The partitioning of the pathogenic forms of the prion protein associated with human variant CJD (PrP(vCJD)), human sporadic CJD (PrP(sCJD)) and Gerstmann-Sträussler-Scheinker (PrP(GSS)) syndrome was compared to the partitioning of hamster scrapie (PrP(Sc)) in three plasma protein purification steps. Sheep scrapie (PrP(Sc)) was similarly evaluated.


METHODS
The starting materials for three plasma protein purification steps, cryoseparation, 3 percent PEG separation, and 11.5 percent PEG separation, were spiked with brain homogenates containing human PrP(vCJD), human PrP(sCJD), human PrP(GSS), sheep PrP(Sc), and hamster 263K PrP(Sc). The partitioning of the pathogenic form of the PrP was analyzed.


RESULTS
Clearance of the pathogenic form of the PrP was measured relative to the effluent fraction. Regardless of the source of the pathogenic prion, clearance was similar to hamster PrP(Sc). A nominal amount of clearance (approx., 1 log), an intermediate amount of clearance (approx., 2 log), and a substantial amount of clearance (> or = 3 log) were observed for the cryoseparation, 3 percent PEG separation, and 11.5 percent PEG separation steps, respectively. In the latter step, no PrP was detected in the effluents.


CONCLUSIONS
These data demonstrate that human prions, including vCJD prions, can be removed during the purification of human therapeutic proteins and indicate that partitioning of human prions is similar to that observed in the hamster scrapie model.
Stenland
Christopher J
CJ
Department of Pathogen Safety Research, Bayer Biological Products, Research Triangle Park, North Carolina 27709, USA. chris.stenland.b@bayer.com
Lee
Douglas C
DC
Brown
Paul
P
Petteway
Stephen R
SR
Rubenstein
Richard
R
D000818:Animals; D001923:Brain Chemistry; D007562:Creutzfeldt-Jakob Syndrome / Q000097:blood*; D006224:Cricetinae; D004195:Disease Models, Animal; D016098:Gerstmann-Straussler-Scheinker Disease / Q000097:blood*; D006801:Humans; D008647:Mesocricetus; D018620:PrPSc Proteins / Q000097:blood / Q000302:isolation & purification*; D012608:Scrapie / Q000097:blood*; D012756:Sheep; D013045:Species Specificity
D018620:PrPSc Proteins