Studies on the removal of abnormal prion protein by processes used in the manufacture of human plasma products.

OBJECTIVE

To identify if any process steps used in plasma fractionation may have a capability of removing agents of human transmissible spongiform encephalopathy (TSE).

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.