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The HÄMOSAFE Process

Inactivation of prions and non-enveloped viruses in plasma derivatives

Abstract

Herwig E. Reichl, HÄMOSAN GesmbH

Whereas established methods of inactivation of lipid-enveloped viruses have been developed and validated over the last decade, mainly driven by the transmission of HIV through blood products, the problem of transmission of non-lipid coated viruses is slowly attracting interest of medical authorities. Another upcoming threat is the group of Transmissible Encephalophathies, with its possible implications on the blood industry. Whether this new type of infectivity called "Prions" contains nucleic acids or not, they are definitely the smallest and toughest infectious agents knownto date, not even fully inactivated by 2 N NaOH. (Taylor et al., 1994)

Prions cause not only diseases in ruminants (BSE, Scrapie) but also in humans (Kuru, Creutzfeldt-Jacob Disease= CJD) and seem to cross species barriers quite easily. Therefore their inactivation should be attempted in the production of therapeuticals from animal and human sources. As rapid tests for Prions are only being developed at present, screening and quarantine are no adequate measures. The importance is highlighted by the recent withdrawal of batches of HSA and IgG after clinical symptoms of CJD have developed in plasmaphoresis donors.

HÄMOSAN have developed a process which not only inactivates non-lipidcoated viruses like FMD, Polio and SV 40 at high titres, but also Prions,shown by the removal of >10 exp. 5.8 of Scrapie infectivity during the processing of Serum Albumin.

This HÄMOSAFE process can be adapted to treat plasma and serum, immunoglobulins and even enzymes and clotting factors.

Its main steps are

  1. Heating in the presence of anionic tensides (and stabilisers)
  2. Incubation with chaotropic reagents, which can be included into existing purification schemes without major changes or investments.

Care must be taken when designing validation experiments to test not only the inactivation achieved by each step, but to conduct an "overall inactivation study" in addition. This latter study will result in lower clearance values than the added results of the individual steps.