The impact of Creutzfeldt-Jakob disease and variant Creutzfeldt-Jakob disease on plasma safety

Prospects for the development of pre-mortem laboratory diagnostic tests for Creutzfeldt-Jakob disease

At present the diagnosis of Creutzfeldt-Jakob disease (CJD) and related transmissible spongiform encephalopathies in humans is based on clinical criteria and (at post-mortem) the histopathological and immunological examination of brain tissue. The misfolded prion protein, PrPSc, is the single most significant marker, but its recognition by standard serological methods is complicated by its antigenic similarity to the normal prion protein, PrPC. Although there are commercial diagnostic assays available for bovine spongiform encephalopathy using brain specimens taken at slaughter, there are no suitable pre-mortem assays for cattle and none either for pre-mortem human disease. Especially in view of the recent report of variant CJD transmission by blood transfusion, it is important that tests for pre-symptomatic infections are developed. This will safeguard the blood supply and, for example, prevent the transmission of CJD in neurosurgery. This paper reviews the current and prospective approaches to the pre-mortem diagnosis of CJD, in particular its variant form.

Transcript level of erythroid differentiation-related factor, a candidate surrogate marker for transmissible spongiform encephalopathy diseases in blood, shows a broad range of variation in healthy individuals

BACKGROUND

In 2001, it was demonstrated that the expression of the erythroid differentiation-related factor (EDRF) is reduced in lymphatic tissues of rodents and cattle as well as in whole blood of sheep that suffer from transmissible spongiform encephalopathy.

STUDY DESIGN AND METHODS

To determine whether the normal range of EDRF expression varies in healthy individuals, mRNA levels were measured in whole blood samples from 106 healthy blood donors by quantitative real-time RT-PCR. Furthermore, the correlations of transcript levels with individual physical characteristics were analyzed. In addition, EDRF expression was examined in total RNA samples from a lymph node and the intestine.

RESULTS

The data show that EDRF mRNA levels in healthy persons vary within a total range of 2 log units as well as they display a weak correlation with body height. Furthermore, it was found that EDRF is also expressed in lymph nodes and the intestine.

CONCLUSION

Owing to its broad range of variation, measuring the EDRF expression does not seem to be a good surrogate marker, unless an altered expression is distinctively different from the varying level in healthy humans.

Does the neuropathology of human patients with variant Creutzfeldt-Jakob disease reflect haematogenous spread of the disease?

To test the hypothesis that the distribution of the pathology in variant Creutzfeldt-Jakob disease (vCJD) represents haematogenous spread of the disease, we studied the spatial correlation between the vacuolation, prion protein (PrP) deposits, and the blood vessel profiles in the cerebral cortex, hippocampus, dentate gyrus, and cerebellum of 11 cases of the disease. In the majority of areas, there were no significant spatial correlations between either the vacuolation or the diffuse type of PrP deposit and the blood vessels. By contrast, a consistent pattern of spatial correlation was observed between the florid PrP deposits and blood vessels mainly in the cerebral cortex. The frequency of positive spatial correlations was similar in different anatomical areas of the cerebral cortex and in the upper compared with the lower laminae. Hence, with the exception of the florid deposits, the data do not demonstrate a spatial relationship between the pathological features of vCJD and blood vessels. The spatial correlation of the florid deposits and blood vessels may be attributable to factors associated with the blood vessels that promote the aggregation of PrP to form a condensed core rather than reflecting the haematogenous spread of the disease.

Removal of prion challenge from an immune globulin preparation by use of a size-exclusion filter

BACKGROUND

A size-exclusion filter (Viresolve 180, Millipore Corp.) was tested for its ability to remove transmissible spongiform encephalopathies prion protein from an immune globulin preparation during ultrafiltration.

STUDY DESIGN AND METHODS

Hamster-adapted 263K scrapie brain homogenate (SBH) was spiked into Rh0(D) immune globulin (human) at 1 in 300 and 1 in 1000 dilutions. Before spiking, the SBH was treated with detergent, sonicated, and filtered through serial 0.45-, 0.22-, and 0.1-microm filters to present a rigorous filter challenge. Process variables were monitored throughout the ultrafiltration to ensure that the spiked material did not compromise the membrane flux. Removal of scrapie prion protein (PrP(Sc)) material was determined by use of a sensitive Western blot assay.

RESULTS

The turbid SBH became completely translucent after sonication and passage through the 0.45-, 0.22-, and 0.1-microm filters. The filtration of the immune globulin containing PrP(Sc) material was more difficult to perform than was filtration of immune globulin spiked with the normal cellular isoform. Even during tangential flow filtration, the fibril material prevented the PrP(Sc)-spiked immune globulin from passing as readily through the filter. Western blot results indicated a removal of greater than or equal to 2.5 log PrP(Sc), while remaining within the normal filtration limits.

CONCLUSIONS

The composition, physical condition, and the amount of SBH introduced have significant effects on the filtration of the immune globulin and the log removal values obtained. By use of a detergent-treated, sonicated, and filtered preparation of SBH, it was demonstrated that the Viresolve 180 effectively removes PrP(Sc) from the immune globulin.

Comparative analysis of normal prion protein expression on human, rodent, and ruminant blood cells by using a panel of prion antibodies

BACKGROUND

It is not known whether variant CJD can be transmitted within the human population by blood transfusion. The expression of normal cellular prion protein (PrPC) by different blood cell types may permit selective uptake and dissemination of infectivity.

STUDY DESIGN AND METHODS

The normal distribution of PrPC on the major blood cell types of species known to be susceptible to natural or experimental transmissible spongiform encephalopathies was studied. Blood from healthy humans, mice, hamsters, cattle, and sheep was examined by flow cytometry by using a large panel of antibodies with different prion protein (PrP) epitope specificities to maximize the detection of PrP variants across species and cell type.

RESULTS

PrP was detected on all major human blood cells types except eosinophils, but was not detected as ubiquitously or uniformly on major blood cell types of different animal species.

CONCLUSION

Different animal species have unique patterns of expression of PrPC on blood cell types, with none equivalent to the human pattern. This needs to be considered when extrapolating from animal models of blood-borne transmissible spongiform encephalopathy infectivity, particularly in regard to the risk assessment of potential variant CJD spread within the human population. The relationship between PrP distribution and infectivity distribution in blood needs further investigation.

Phenothiazines: potential management of Creutzfeldt-Jacob disease and its variants

Creutzfeldt-Jakob disease acquired from bovines (nvCJD) has been responsible for nearly 100 deaths in the UK and thousands more may die in the years to come. New variant CJD (nvCJD) is incurable and although clinical diagnosis is becoming more precise, the diagnosis is only certain at autopsy. Phenothiazine derivatives inhibit production of prions, the disease causing agent, in cultured neuroblastoma cells, and an advanced case of nvCJD was recently brought to remission by the use of these agents in combination with an antimalarial. In this review we present direct and circumstantial evidence in support of a model describing the manner by which the intracellular antimicrobial activity of phenothiazines might cause the destruction of intracellular prions.