Risk of transmission of Creutzfeldt-Jakob disease by transfusion of blood, plasma, and plasma derivatives

Update on Transfusion Medicine

Clinical pharmacists often participate on critical care teams that manage patients with bleeding emergencies. Although blood products are usually dispensed from the blood bank and not the pharmacy, pharmacists should be conversant in the language and trends of transfusion medicine, much like they are with other therapeutic agents. Toward that goal, this review provides a concise transfusion medicine tutorial, covering all commonly used blood products, including red blood cells, platelets, fresh frozen plasma, and plasma derivatives such as cryoprecipitate, prothrombin complex concentrates, and albumin. Usage patterns, the rationale for administering the various blood products, and studies that have attempted to determine appropriate criteria for ordering transfusions (transfusion triggers) are discussed. The benefits, risks, and several ongoing controversies that relate to the appropriateness and safety of blood product use are also summarized.

Spiroplasma as a candidate agent for the transmissible spongiform encephalopathies

The recovery of a novel Spiroplasma sp. from brain tissues from sheep with scrapie, cervids with chronic wasting disease, and from patients with Creutzfeldt-Jakob disease through passage through embryonated eggs has raised the issue of the role of Spiroplasma in the transmissible spongiform encephalopathies (TSE). In this review, we have inserted into an epidemiologic infection model evidence accumulated over the past 30 years showing involvement of Spiroplasma infection in TSE. These data support our hypothesis that a Spiroplasma sp. is the causal agent of TSE, although Koch's postulates must be fulfilled to definitively answer that question.

Inactivation of TSE agents: safety of blood and blood-derived products

Evidence relating to whether the blood of individuals with sporadic Creutzfeldt-Jakob disease is infectious is discussed. The conclusion is that this is unproven. Similar consideration is given to the blood of individuals with variant Creutzfeldt-Jakob disease; it is concluded that there is no convincing evidence that the blood is infectious but reasons for caution are presented. There is discussion regarding factors that add to the safety of plasma-derived therapeutic products, including the capacity of the manufacturing processes to inactivate or remove infectivity by the chemical and physical processes involved. There is extended discussion regarding the inactivation of these types of agents and the few reliable options available in worst-case scenarios such as the processing of instruments used neurosurgically on known or suspected cases. The most effective method is exposure to 1 M sodium hydroxide during autoclaving at 121 degrees C. The inappropriateness of applying any of the most effective methods to blood and blood-products because they are harsh and denaturing is discussed. Nevertheless, such procedures have potential application to the plant used in the manufacture of plasma-products. Evidence is presented which suggests that even more modest treatments (the use of lower concentrations of sodium hydroxide at lower temperatures) are effective when applied to surfaces that are free from any tissue contamination, as is the case with plant used to manufacture plasma-derived products. This evidence has come from studies carried out by the gelatin manufacturers of Europe regarding the capability of their manufacturing systems to inactivate the causal agent of bovine spongiform encephalopathy.

Preventing accidental transmission of human transmissible spongifom encephalopathies

The mechanism by which humans became infected with the BSE agent is discussed, and the matter of potential person-to person transmission of TSEs through contagion or medical procedures is considered. There is some discussion regarding the current evidence relating to whether or not the blood of humans infected with TSEs is infectious. Considerable emphasis is placed on the fact that TSE agents are known to be relatively resistant to decontamination by procedures that are effective with conventional micro-organisms, including (under worst-case conditions) the autoclaving procedures used to sterilise surgical instruments. Methods for providing additional re-assurance with regard to the safety of instruments are described. Safety in the pathology laboratory is discussed extensively because TSE agents are not inactivated by the usual processes used to fix tissues, and such laboratories will receive fixed tissues that are still highly infectious as far as TSE agents are concerned.

Studies on the removal of a bovine spongiform encephalopathy-derived agent by processes used in the manufacture of human immunoglobulin

BACKGROUND AND OBJECTIVES

There is still uncertainty over how the agent of variant Creutzfeld-Jakob disease (vCJD) would partition during the manufacture of plasma derivatives. In this study, a BSE-derived agent was used as a vCJD model to determine the extent to which infectivity could be removed by selected steps used in the manufacture of intravenous immunoglobulin (IVIG).

MATERIALS AND METHODS

Murine-passaged BSE (strain 301V), in the form of a microsomal fraction prepared from infected brain, was used to "spike" the starting material in three experiments. The partitioning of BSE infectivity was measured over Fraction I+III precipitation, borosilicate microfibre depth filtration and Seitz depth filtration, with these steps being examined individually and in series.

RESULTS

Most 301V infectivity partitioned into Fraction I+III (log reduction 2.1). Infectivity remaining in Supernatant I+III was reduced by AP20 glass-fibre depth filtration (log reduction 0.6) and subsequently removed to below the limit of detection by Seitz KS80 depth filtration, giving an overall log reduction of > or = 2.9 for the three steps in series. By contrast, glass-fibre depth filtration gave a log reduction of 2.4 when challenged directly with "spiked" feedstock. Seitz KS80 depth filtration gave a log reduction of > or = 3.1 when challenged directly with 'spiked' feedstock and also removed residual infectivity to below the limit of detection when applied as the final step in series.

CONCLUSIONS

Results using a BSE-derived agent suggest that vCJD infectivity should be substantially removed from immunoglobulin G (IgG) solutions by Fraction I+III precipitation and Seitz KS80 depth filtration. The three different process steps examined acted in a complementary manner to one another when operated in series. However, the data demonstrated that it would be inappropriate to add together the reduction factors that had been derived for each step in isolation.

Advances in pretransfusion infectious disease testing: ensuring the safety of transfusion therapy

The public expects a zero-tolerance policy for the transmission of infectious agents by blood transfusion. Although unrealistic, the efforts to reach this goal have produced an extremely safe albeit costly blood supply [82]. Blood collecting agencies, the FDA, physicians, and scientists have over the past 20 years created a complex system of layers of protection to interdict transfusion-transmitted infections (Fig. 2). As new, exotic, potentially blood transmittable infectious agents evolve [83], new barriers will be erected to [figure: see text] interdict these agents. In the interim, the US blood supply is the safest in the world.