Pathogen reduction of fresh plasma using riboflavin and ultraviolet light: effects on plasma coagulation proteins.

BACKGROUND: Treatment with riboflavin and ultraviolet (UV) light reduces the pathogens present in blood components. This study assessed changes to the coagulation proteins that had occurred during this treatment of fresh plasma units before freezing. STUDY DESIGN AND METHODS: Twenty fresh plasma units (230 +/- 30 mL) were treated by the Mirasol process (CaridianBCT Biotechnologies) and frozen within 8 hours of donation. Plasma units were combined with 35 mL of a 500 micromol/L riboflavin solution in an illumination bag to achieve a final concentration of approximately 60 micromol/L riboflavin. The bag was placed in the Mirasol illuminator and exposed to UV light (6.24 J/mL). Samples were frozen before and after treatment. RESULTS: Recoveries observed were 67.7 +/- 3.9% Factor (F)XI, 68.5 +/- 3.3% FVIII:C, 78.8 +/- 4.5% fibrinogen, 78.9 +/- 4.1% FV, 79.0 +/- 4.2% FVII, 79.0 +/- 8.6% F IX, 79.7 +/- 2.6% FX, and 85.0 +/- 3.7% FII. Von Willebrand factor (VWF) antigen, VWF:ristocetin cofactor, and ADAMTS13 recoveries were 87.0 +/- 7.1, 85.5 +/- 6.6, and 73.3 +/- 15.2%, respectively, while that of protein C was 83.6 +/- 2.6%. A loss of high-molecular-weight VWF multimers was observed in most units. Recoveries for protein S, antithrombin, and plasmin inhibitor were greater than 90%. The mean FVIII:C concentration, after treatment, was 0.76 +/- 0.17 IU/mL. CONCLUSIONS: As with other pathogen reduction technologies, the Mirasol process resulted in some loss of coagulation factor activity. For most Mirasol-treated units and for most of the tested factors this is unlikely to have clinical impact, but trials are required to demonstrate this.

Human platelets as a substrate source for the in vitro amplification of the abnormal prion protein (PrP) associated with variant Creutzfeldt-Jakob disease.

BACKGROUND: Four recent cases of transfusion-related transmission of variant Creutzfeldt-Jakob disease (vCJD) highlight the need to develop a highly sensitive and specific screening test to detect infectivity in the blood of asymptomatic infected individuals. Protein misfolding cyclic amplification (PMCA), a method for the amplification of minute amounts of disease-associated abnormal prion protein (PrP(Sc)) to readily detectable levels, could be incorporated into such a test provided that a suitable substrate source for routine use in human PMCA reactions can be found. STUDY DESIGN AND METHODS: With the use of seed sources from individuals with variant and sporadic CJD, the use of human platelets (PLTs) as a PMCA substrate source was evaluated. The effects of seed/substrate prion protein gene (PRNP) codon 129 genotype compatibility on amplification efficiency and freeze-thaw on a substrate's ability to support amplification and the degree of amplification achieved by serial PMCA (sPMCA) were investigated. RESULTS: Seed/substrate PRNP codon 129 compatibility was found to have a major influence on PrP(Sc) amplification efficiency. Individual substrates, of the same PRNP codon 129 genotype, could be pooled and stored frozen for use in subsequent PMCA reactions. A consistent 10-fold increase in PrP(Sc) detection sensitivity was achieved after each round of sPMCA, resulting in a 10,000-fold increase in detection sensitivity after four rounds, with no evidence of de novo PrP(Sc) production detected in the unseeded PLT substrate. CONCLUSIONS: Providing issues of seed/substrate PRNP codon 129 compatibility are taken into consideration human PLTs are a suitable, readily available, renewable substrate source for use in human PMCA applications.

Freezing of buffy coat-derived, leukoreduced platelet concentrates in 6 percent dimethyl sulfoxide.

BACKGROUND: There has recently been renewed interest in freezing platelets (PLTs) in dimethyl sulfoxide (DMSO) for the treatment of major traumatic injuries, especially in military situations. This study examined PLTs that were frozen in small volumes of 6 percent DMSO at -80 degrees C. STUDY DESIGN AND METHODS: Buffy coat-derived pooled leukoreduced PLT concentrates were frozen in 6 percent DMSO and stored at -80 degrees C. Assays included hypotonic shock response (HSR); aggregation; glycoprotein (GP)Ibalpha and P-selectin binding sites; annexin V binding to phosphatidylserine, glycocalicin, and lactate dehydrogenase (LDH). Cone and plate technology (DiaMed Impact-R, DiaMed) was used to test PLT function under near physiologic conditions. RESULTS: The freeze-thaw loss of PLTs was 23 percent. HSR was 17 +/- 7 percent. Cytometry demonstrated two populations of PLTs: one with normal levels of GPIbalpha binding sites (27 x 10(3) +/- 3 x 10(3)/PLT) and one with reduced levels (5.5 x 10(3) +/- 1.2 x 10(3)/PLT). There were 1.4 x 10(3) +/- 0.2 x 10(3) P-selectin binding sites per PLT. Annexin V binding to phosphatidylserine was 50 +/- 9 percent and LDH was 496 +/- 207 IU per 10(12) PLTs. Surface coverage and aggregate size, as measured by the DiaMed Impact-R, were similar to those observed with PLTs stored for 2 days at 22 degrees C. CONCLUSION: Some degree of activation was demonstrated by the proportion of PLTs with reduced levels of GPIbalpha binding sites, increased P-selectin expression, and increased Annexin V binding. LDH concentrations indicated a degree of lysis. The DiaMed Impact-R results showed that the PLTs were still capable of adhering to surfaces and forming aggregates under shear force.

All clinically-relevant blood components transmit prion disease following a single blood transfusion: a sheep model of vCJD.

Variant CJD (vCJD) is an incurable, infectious human disease, likely arising from the consumption of BSE-contaminated meat products. Whilst the epidemic appears to be waning, there is much concern that vCJD infection may be perpetuated in humans by the transfusion of contaminated blood products. Since 2004, several cases of transfusion-associated vCJD transmission have been reported and linked to blood collected from pre-clinically affected donors. Using an animal model in which the disease manifested resembles that of humans affected with vCJD, we examined which blood components used in human medicine are likely to pose the greatest risk of transmitting vCJD via transfusion. We collected two full units of blood from BSE-infected donor animals during the pre-clinical phase of infection. Using methods employed by transfusion services we prepared red cell concentrates, plasma and platelets units (including leucoreduced equivalents). Following transfusion, we showed that all components contain sufficient levels of infectivity to cause disease following only a single transfusion and also that leucoreduction did not prevent disease transmission. These data suggest that all blood components are vectors for prion disease transmission, and highlight the importance of multiple control measures to minimise the risk of human to human transmission of vCJD by blood transfusion.

Production and characterization of a panel of monoclonal antibodies against native human cellular prion protein.

The human prion diseases, such as variant Creutzfeldt-Jakob disease (vCJD), are characterized by the conversion of the normal cellular prion protein (PrP(C)) into an abnormal disease associated form (PrP(Sc)). Monoclonal antibodies (MAbs) that recognize these different PrP isoforms are valuable reagents both in the diagnosis of these diseases and in prion disease research in general but we know of no attempts to raise MAbs against native human PrP(C). We immunized prion protein gene ablated (PrP(-/-)) mice with native human PrP(C) purified from platelets (pHuPrP) generating a predominantly IgG isotype anti-pHuPrP polyclonal antibody response in all mice. Following fusion of splenocytes from the immunized mice with SP2/0 myeloma cells, we were able to identify single cell clone and cryopreserve 14 stable hybridoma cell lines producing MAbs that reacted with pHuPrP. The properties of these MAbs (such as isotype, binding to native/denatured pHuPrP, and HuPrP epitopes recognized) are described. Furthermore, several of these MAbs showed a selectivity in their ability to immunoprecipitate disease associated PrP(Sc) and its corresponding protease resistant core (PrP(res)).

An antibody to the aggregated synthetic prion protein peptide (PrP106-126) selectively recognizes disease-associated prion protein (PrP) from human brain specimens.

Human prion diseases are characterized by the conversion of the normal host cellular prion protein (PrP(C)) into an abnormal misfolded form [disease-associated prion protein (PrP(Sc))]. Antibodies that are capable of distinguishing between PrP(C) and PrP(Sc) may prove to be useful, not only for the diagnosis of these diseases, but also for a better understanding of the molecular mechanisms involved in disease pathogenesis. In an attempt to produce such antibodies, we immunized mice with an aggregated peptide spanning amino acid residues 106 to 126 of human PrP (PrP106-126). We were able to isolate and single cell clone a hybridoma cell line (P1:1) which secreted an IgM isotype antibody [monoclonal antibody (mAb P1:1)] that recognized the aggregated, but not the monomeric form of the immunogen. When used in immunoprecipitation assays, the antibody did not recognize normal PrP(C) from non-prion disease brain specimens, but did selectively immunoprecipitate full-length PrP(Sc) from cases of variant and sporadic Creutzfeldt-Jakob disease and Gerstmann-Straussler-Scheinker disease. These results suggest that P1:1 recognizes an epitope formed during the structural rearrangement or aggregation of the PrP that is common to the major PrP(Sc) types found in the most common forms of human prion disease.

Purification of normal cellular prion protein from human platelets and the formation of a high molecular weight prion protein complex following platelet activation.

A method for the extraction and purification of PrP(C), in its native monomeric form, from outdated human platelet concentrates is described. Both calcium ionophore platelet activation and lysis in Triton X-100 were evaluated as methods for the extraction of soluble platelet PrP(C) in its monomeric form. Following platelet activation, the majority of released PrP(C) was detected as a disulphide linked high molecular weight complex, which under reducing conditions could be separated into what appear to be stable non-disulphide linked PrP dimers or PrP covalently linked to another as yet unidentified protein. This phenomenon appears to be unique to activation since only monomeric PrP(C) was detected following lysis of resting platelets. Subsequently, PrP(C) was purified from the Triton X-100 lysate by sequential cation ion exchange and Cu2+ affinity chromatography. From 10 L of outdated platelet concentrate, we were able to recover 1.29 mg PrP(C) at a purity of 92%.