Long-range inhibition synchronizes and updates prefrontal task activity.

Changes in patterns of activity within the medial prefrontal cortex enable rodents, non-human primates and humans to update their behaviour to adapt to changes in the environment-for example, during cognitive tasks1-5. Parvalbumin-expressing inhibitory neurons in the medial prefrontal cortex are important for learning new strategies during a rule-shift task6-8, but the circuit interactions that switch prefrontal network dynamics from maintaining to updating task-related patterns of activity remain unknown. Here we describe a mechanism that links parvalbumin-expressing neurons, a new callosal inhibitory connection, and changes in task representations. Whereas nonspecifically inhibiting all callosal projections does not prevent mice from learning rule shifts or disrupt the evolution of activity patterns, selectively inhibiting only callosal projections of parvalbumin-expressing neurons impairs rule-shift learning, desynchronizes the gamma-frequency activity that is necessary for learning8 and suppresses the reorganization of prefrontal activity patterns that normally accompanies rule-shift learning. This dissociation reveals how callosal parvalbumin-expressing projections switch the operating mode of prefrontal circuits from maintenance to updating by transmitting gamma synchrony and gating the ability of other callosal inputs to maintain previously established neural representations. Thus, callosal projections originating from parvalbumin-expressing neurons represent a key circuit locus for understanding and correcting the deficits in behavioural flexibility and gamma synchrony that have been implicated in schizophrenia and related conditions9,10.

Study protocol: a multicentre, open-label, parallel-group, phase 2, randomised controlled trial of autologous macrophage therapy for liver cirrhosis (MATCH).

INTRODUCTION: Liver cirrhosis is a growing global healthcare challenge. Cirrhosis is characterised by severe liver fibrosis, organ dysfunction and complications related to portal hypertension. There are no licensed antifibrotic or proregenerative medicines and liver transplantation is a scarce resource. Hepatic macrophages can promote both liver fibrogenesis and fibrosis regression. The safety and feasibility of peripheral infusion of ex vivo matured autologous monocyte-derived macrophages in patients with compensated cirrhosis has been demonstrated. METHODS AND ANALYSIS: The efficacy of autologous macrophage therapy, compared with standard medical care, will be investigated in a cohort of adult patients with compensated cirrhosis in a multicentre, open-label, parallel-group, phase 2, randomised controlled trial. The primary outcome is the change in Model for End-Stage Liver Disease score at 90 days. The trial will provide the first high-quality examination of the efficacy of autologous macrophage therapy in improving liver function, non-invasive fibrosis markers and other clinical outcomes in patients with compensated cirrhosis. ETHICS AND DISSEMINATION: The trial will be conducted according to the ethical principles of the Declaration of Helsinki 2013 and has been approved by Scotland A Research Ethics Committee (reference 15/SS/0121), National Health Service Lothian Research and Development department and the Medicine and Health Care Regulatory Agency-UK. Final results will be presented in peer-reviewed journals and at relevant conferences. TRIAL REGISTRATION NUMBERS: ISRCTN10368050 and EudraCT; reference 2015-000963-15.

Cytometric analysis of T cell phenotype using cytokine profiling for improved manufacturing of an EBV-specific T cell therapy.

Adoptive immunotherapy using Epstein-Barr Virus (EBV)-specific T cells is a potentially curative treatment for patients with EBV-related malignancies where other clinical options have proved ineffective. We describe improved good manufacturing practice (GMP)-compliant culture and analysis processes for conventional lymphoblastoid cell line (LCL)-driven EBV-specific T cell manufacture, and describe an improved phenotyping approach for analysing T cell products. We optimized the current LCL-mediated clinical manufacture of EBV-specific T cells to establish an improved process using xenoprotein-free GMP-compliant reagents throughout, and compared resulting products with our previous banked T cell clinical therapy. We assessed effects of changes to LCL:T cell ratio in T cell expansion, and developed a robust flow cytometric marker panel covering T cell memory, activation, differentiation and intracellular cytokine release to characterize T cells more effectively. These data were analysed using a t-stochastic neighbour embedding (t-SNE) algorithm. The optimized GMP-compliant process resulted in reduced cell processing time and improved retention and expansion of central memory T cells. Multi-parameter flow cytometry determined the optimal protocol for LCL stimulation and expansion of T cells and demonstrated that cytokine profiling using interleukin (IL)-2, tumour necrosis factor (TNF)-α and interferon (IFN)-γ was able to determine the differentiation status of T cells throughout culture and in the final product. We show that fully GMP-compliant closed-process culture of LCL-mediated EBV-specific T cells is feasible, and profiling of T cells through cytokine expression gives improved characterization of start material, in-process culture conditions and final product. Visualization of the complex multi-parameter flow cytometric data can be simplified using t-SNE analysis.

Estimation of manufacturing development costs of cell-based therapies: a feasibility study.

BACKGROUND AIMS: Cell-based therapies (CBTs) provide opportunities to treat rare and high-burden diseases. Manufacturing development of these innovative products is said to be complex and costly. However, little research is available providing insight into resource use and cost drivers. Therefore, this study aimed to assess the feasibility of estimating the cost of manufacturing development of two cell-based therapy case studies using a CBT cost framework specifically designed for small-scale cell-based therapies. METHODS: A retrospective costing study was conducted in which the cost of developing an adoptive immunotherapy of Epstein-Barr virus-specific cytotoxic T lymphocytes (CTLs) and a pluripotent stem cell (PSC) master cell bank was estimated. Manufacturing development was defined as products advancing from technology readiness level 3 to 6. The study was conducted in a Scottish facility. Development steps were recreated via developer focus groups. Data were collected from facility administrative and financial records and developer interviews. RESULTS: Application of the manufacturing cost framework to retrospectively estimate the manufacturing design cost of two case studies in one Scottish facility appeared feasible. Manufacturing development cost was estimated at £1,201,016 for CTLs and £494,456 for PSCs. Most costs were accrued in the facility domain (56% and 51%), followed by personnel (20% and 32%), materials (19% and 15%) and equipment (4% and 2%). CONCLUSIONS: Based on this study, it seems feasible to retrospectively estimate resources consumed in manufacturing development of cell-based therapies. This fosters inclusion of cost in the formulation and dissemination of best practices to facilitate early and sustainable patient access and inform future cost-conscious manufacturing design decisions.

Haplobanking induced pluripotent stem cells for clinical use.

The development of induced pluripotent stem cells (iPSCs) by Shinya Yamanaka and colleagues in 2006 has led to a potential new paradigm in cellular therapeutics, including the possibility of producing patient-specific, disease-specific and immune matched allogeneic cell therapies. One can envisage two routes to immunologically compatible iPSC therapies: using genetic modification to generate a 'universal donor' with reduced expression of Human Leukocyte Antigens (HLA) and other immunological targets or developing a haplobank containing iPSC lines specifically selected to provide HLA matched products to large portions of the population. HLA matched lines can be stored in a designated physical or virtual global bank termed a 'haplobank'. The process of 'iPSC haplobanking' refers to the banking of iPSC cell lines, selected to be homozygous for different HLA haplotypes, from which therapeutic products can be derived and matched immunologically to patient populations. By matching iPSC and derived products to a patient's HLA class I and II molecules, one would hope to significantly reduce the risk of immune rejection and the use of immunosuppressive medication. Immunosuppressive drugs are used in several conditions (including autoimmune disease and in transplantation procedures) to reduce rejection of infused cells, or transplanted tissue and organs, due to major and minor histocompatibility differences between donor and recipient. Such regimens can lead to immune compromise and pathological consequences such as opportunistic infections or malignancies due to decreased cancer immune surveillance. In this article, we will discuss what is practically involved if one is developing and executing an iPSC haplobanking strategy.

The Global Alliance for iPSC Therapies (GAiT).

The Global Alliance for iPSC Therapies (GAiT) is a new initiative to support the implementation and clinical application of therapies derived from pluripotent stem cells to the benefit of patients globally. GAiT's mission is to serve as a central, international resource for those organisations developing therapies from clinical-grade induced pluripotent stem cells, and to support the expansion of this nascent field. With the support of its international partners, GAiT already has an early position on manufacturing, regulatory and quality standards. This article details GAiT's development, its mission and structure, as well as how, and by whom, it is funded. The article ends with brief overview of current and upcoming activities.

Pancreas-derived mesenchymal stromal cells share immune response-modulating and angiogenic potential with bone marrow mesenchymal stromal cells and can be grown to therapeutic scale under Good Manufacturing Practice conditions.

BACKGROUND AIMS: Mesenchymal stromal cells (MSCs) isolated from various tissues are under investigation as cellular therapeutics in a wide range of diseases. It is appreciated that the basic biological functions of MSCs vary depending on tissue source. However, in-depth comparative analyses between MSCs isolated from different tissue sources under Good Manufacturing Practice (GMP) conditions are lacking. Human clinical-grade low-purity islet (LPI) fractions are generated as a byproduct of islet isolation for transplantation. MSC isolates were derived from LPI fractions with the aim of performing a systematic, standardized comparative analysis of these cells with clinically relevant bone marrow-derived MSCs (BM MSCs). METHODS: MSC isolates were derived from LPI fractions and expanded in platelet lysate-supplemented medium or in commercially available xenogeneic-free medium. Doubling rate, phenotype, differentiation potential, gene expression, protein production and immunomodulatory capacity of LPIs were compared with those of BM MSCs. RESULTS: MSCs can be readily derived in vitro from non-transplanted fractions resulting from islet cell processing (i.e., LPI MSCs). LPI MSCs grow stably in serum-free or platelet lysate-supplemented media and demonstrate in vitro self-renewal, as measured by colony-forming unit assay. LPI MSCs express patterns of chemokines and pro-regenerative factors similar to those of BM MSCs and, importantly, are equally able to attract immune cells in vitro and in vivo and suppress T-cell proliferation in vitro. Additionally, LPI MSCs can be expanded to therapeutically relevant doses at low passage under GMP conditions. CONCLUSIONS: LPI MSCs represent an alternative source of GMP MSCs with functions comparable to BM MSCs.

What does cell therapy manufacturing cost? A framework and methodology to facilitate academic and other small-scale cell therapy manufacturing costings.

BACKGROUND AIMS: Recent technical and clinical advances with cell-based therapies (CBTs) hold great promise in the treatment of patients with rare diseases and those with high unmet medical need. Currently the majority of CBTs are developed and manufactured in specialized academic facilities. Due to small scale, unique characteristics and specific supply chain, CBT manufacturing is considered costly compared to more conventional medicinal products. As a result, biomedical researchers and clinicians are increasingly faced with cost considerations in CBT development. The objective of this research was to develop a costing framework and methodology for academic and other small-scale facilities that manufacture cell-based therapies. METHODS: We conducted an international multi-center costing study in four facilities in Europe using eight CBTs as case studies. This study includes costs from cell or tissue procurement to release of final product for clinical use. First, via interviews with research scientists, clinicians, biomedical scientists, pharmacists and technicians, we designed a high-level costing framework. Next, we developed a more detailed uniform methodology to allocate cost items. Costs were divided into steps (tissue procurement, manufacturing and fill-finish). The steps were each subdivided into cost categories (materials, equipment, personnel and facility), and each category was broken down into facility running (fixed) costs and operational (variable) costs. The methodology was tested via the case studies and validated in developer interviews. Costs are expressed in 2018 euros (€). RESULTS: The framework and methodology were applicable across facilities and proved sensitive to differences in product and facility characteristics. Case study cost estimates ranged between €23 033 and €190 799 Euros per batch, with batch yield varying between 1 and 88 doses. The cost estimations revealed hidden costs to developers and provided insights into cost drivers to help design manufacturing best practices. CONCLUSIONS: This framework and methodology provide step-by-step guidance to estimate manufacturing costs specifically for cell-based therapies manufactured in academic and other small-scale enterprises. The framework and methodology can be used to inform and plan cost-conscious strategies for CBTs.

Enhancing WNT Signaling Restores Cortical Neuronal Spine Maturation and Synaptogenesis in Tbr1 Mutants.

Tbr1 is a high-confidence autism spectrum disorder (ASD) gene encoding a transcription factor with distinct pre- and postnatal functions. Postnatally, Tbr1 conditional knockout (CKO) mutants and constitutive heterozygotes have immature dendritic spines and reduced synaptic density. Tbr1 regulates expression of several genes that underlie synaptic defects, including a kinesin (Kif1a) and a WNT-signaling ligand (Wnt7b). Furthermore, Tbr1 mutant corticothalamic neurons have reduced thalamic axonal arborization. LiCl and a GSK3ß inhibitor, two WNT-signaling agonists, robustly rescue the dendritic spines and the synaptic and axonal defects, suggesting that this could have relevance for therapeutic approaches in some forms of ASD.

Human umbilical cord perivascular cells improve human pancreatic islet transplant function by increasing vascularization.

Islet transplantation is an efficacious therapy for type 1 diabetes; however, islets from multiple donor pancreata are required, and a gradual attrition in transplant function is seen. Here, we manufactured human umbilical cord perivascular mesenchymal stromal cells (HUCPVCs) to Good Manufacturing Practice (GMP) standards. HUCPVCs showed a stable phenotype while undergoing rapid ex vivo expansion at passage 2 (p2) to passage 4 (p4) and produced proregenerative factors, strongly suppressing T cell responses in the resting state and in response to inflammation. Transplanting an islet equivalent (IEQ):HUCPVC ratio of 1:30 under the kidney capsule in diabetic NSG mice demonstrated the fastest return to normoglycemia by 3 days after transplant: Superior glycemic control was seen at both early (2.7 weeks) and later stages (7, 12, and 16 weeks) versus ratios of 1:0, 1:10, and 1:50, respectively. Syngeneic islet transplantation in immunocompetent mice using the clinically relevant hepatic portal route with a marginal islet mass showed that mice transplanted with an IEQ:HUCPVC ratio of 1:150 had superior glycemic control versus ratios of 1:0, 1:90, and 1:210 up to 6 weeks after transplant. Immunodeficient mice transplanted with human islets (IEQ:HUCPVC ratio of 1:150) exhibited better glycemic control for 7 weeks after transplant versus islet transplant alone, and islets transplanted via the hepatic portal vein in an allogeneic mouse model using a curative islet mass demonstrated delayed rejection of islets when cotransplanted with HUCPVCs (IEQ:HUCPVC ratio of 1:150). The immunosuppressive and proregenerative properties of HUCPVCs demonstrated long-term positive effects on graft function in vivo, indicating that they may improve long-term human islet allotransplantation outcomes.

Rapid GMP-Compliant Expansion of SARS-CoV-2-Specific T Cells From Convalescent Donors for Use as an Allogeneic Cell Therapy for COVID-19.

COVID-19 disease caused by the SARS-CoV-2 virus is characterized by dysregulation of effector T cells and accumulation of exhausted T cells. T cell responses to viruses can be corrected by adoptive cellular therapy using donor-derived virus-specific T cells. One approach is the establishment of banks of HLA-typed virus-specific T cells for rapid deployment to patients. Here we show that SARS-CoV-2-exposed blood donations contain CD4 and CD8 memory T cells which recognize SARS-CoV-2 spike, nucleocapsid and membrane antigens. Peptides of these antigens can be used to isolate virus-specific T cells in a GMP-compliant process. The isolated T cells can be rapidly expanded using GMP-compliant reagents for use as an allogeneic therapy. Memory and effector phenotypes are present in the selected virus-specific T cells, but our method rapidly expands the desirable central memory phenotype. A manufacturing yield ranging from 1010 to 1011 T cells can be obtained within 21 days culture. Thus, multiple therapeutic doses of virus-specific T cells can be rapidly generated from convalescent donors for potential treatment of COVID-19 patients.

Safety profile of autologous macrophage therapy for liver cirrhosis.

Therapies to reduce liver fibrosis and stimulate organ regeneration are urgently needed. We conducted a first-in-human, phase 1 dose-escalation trial of autologous macrophage therapy in nine adults with cirrhosis and a Model for End-Stage Liver Disease (MELD) score of 10-16 (ISRCTN 10368050). Groups of three participants received a single peripheral infusion of 107, 108 or up to 109 cells. Leukapheresis and macrophage infusion were well tolerated with no transfusion reactions, dose-limiting toxicities or macrophage activation syndrome. All participants were alive and transplant-free at one year, with only one clinical event recorded, the occurrence of minimal ascites. The primary outcomes of safety and feasibility were met. This study informs and provides a rationale for efficacy studies in cirrhosis and other fibrotic diseases.

Microcircuit Mechanisms through which Mediodorsal Thalamic Input to Anterior Cingulate Cortex Exacerbates Pain-Related Aversion.

Hyperexcitability of the anterior cingulate cortex (ACC) is thought to drive aversion associated with chronic neuropathic pain. Here, we studied the contribution of input from the mediodorsal thalamus (MD) to ACC, using sciatic nerve injury and chemotherapy-induced mouse models of neuropathic pain. Activating MD inputs elicited pain-related aversion in both models. Unexpectedly, excitatory responses of layer V ACC neurons to MD inputs were significantly weaker in pain models compared to controls. This caused the ratio between excitation and feedforward inhibition elicited by MD input to shift toward inhibition, specifically for subcortically projecting (SC) layer V neurons. Furthermore, direct inhibition of SC neurons reproduced the pain-related aversion elicited by activating MD inputs. Finally, both the ability to elicit pain-related aversion and the decrease in excitation were specific to MD inputs; activating basolateral amygdala inputs produced opposite effects. Thus, chronic pain-related aversion may reflect activity changes in specific pathways, rather than generalized ACC hyperactivity.

A Report from a Workshop of the International Stem Cell Banking Initiative, Held in Collaboration of Global Alliance for iPSC Therapies and the Harvard Stem Cell Institute, Boston, 2017.

This report summarizes the recent activity of the International Stem Cell Banking Initiative held at Harvard Stem Cell Institute, Boston, MA, USA, on June 18, 2017. In this meeting, we aimed to find consensus on ongoing issues of quality control (QC), safety, and efficacy of human pluripotent stem cell banks and their derivative cell therapy products for the global harmonization. In particular, assays for the QC testing such as pluripotency assays test and general QC testing criteria were intensively discussed. Moreover, the recent activities of global stem cell banking centers and the regulatory bodies were briefly summarized to provide an overview on global developments and issues. Stem Cells 2019;37:1130-1135.

Allogeneic Ex Vivo Expanded Corneal Epithelial Stem Cell Transplantation: A Randomized Controlled Clinical Trial.

Limbal stem cell deficiency (LSCD) is a disease resulting from the loss or dysfunction of epithelial stem cells, which seriously impairs sight. Autologous limbal stem cell transplantation is effective in unilateral or partial bilateral disease but not applicable in total bilateral disease. An allogeneic source of transplantable cells for use in total bilateral disease can be obtained from culture of donated cadaveric corneal tissue. We performed a controlled multicenter study to examine the feasibility, safety, and efficacy of allogeneic corneal epithelial stem cells in the treatment of bilateral LSCD. Patients were randomized to receive corneal epithelial stem cells cultured on amniotic membrane (AM): investigational medicinal product (IMP) or control AM only. Patients received systemic immunosuppression. Primary endpoints were safety and visual acuity, secondary endpoint was change in composite ocular surface score (OSS). Sixteen patients were treated and 13 patients completed all assessments. Safety was demonstrated and 9/13 patients had improved visual acuity scores at the end of the trial, with no significant differences between IMP and control groups. Patients in the IMP arm demonstrated significant, sustained improvement in OSS, whereas those in the control arm did not. Serum cytokine levels were measured during and after the period of immune suppression and we identified strongly elevated levels of CXCL8 in the serum of patients with aniridia, which persisted throughout the trial. This first randomized control trial of allogeneic corneal epithelial stem cells in severe bilateral LSCD demonstrates the feasibility and safety of this approach. Stem Cells Translational Medicine 2019;8:323-331.

Quality control guidelines for clinical-grade human induced pluripotent stem cell lines.

Use of clinical-grade human induced pluripotent stem cell (iPSC) lines as a starting material for the generation of cellular therapeutics requires demonstration of comparability of lines derived from different individuals and in different facilities. This requires agreement on the critical quality attributes of such lines and the assays that should be used. Working from established recommendations and guidance from the International Stem Cell Banking Initiative for human embryonic stem cell banking, and concentrating on those issues more relevant to iPSCs, a series of consensus workshops has made initial recommendations on the minimum dataset required to consider an iPSC line of clinical grade, which are outlined in this report. Continued evolution of this field will likely lead to revision of these guidelines on a regular basis.

Repurposing the Cord Blood Bank for Haplobanking of HLA-Homozygous iPSCs and Their Usefulness to Multiple Populations.

Although autologous induced pluripotent stem cells (iPSCs) can potentially be useful for treating patients without immune rejection, in reality it will be extremely expensive and labor-intensive to make iPSCs to realize personalized medicine. An alternative approach is to make use of human leukocyte antigen (HLA) haplotype homozygous donors to provide HLA matched iPSC products to significant numbers of patients. To establish a haplobank of iPSCs, we repurposed the cord blood bank by screening ∼4,200 high resolution HLA typed cord blood samples, and selected those homozygous for the 10 most frequent HLA-A,-B,-DRB1 haplotypes in the Korean population. Following the generation of 10 iPSC lines, we conducted a comprehensive characterization, including morphology, expression of pluripotent markers and cell surface antigens, three-germ layer formation, vector clearance, mycoplasma/microbiological/viral contamination, endotoxin, and short tandem repeat (STR) assays. Various genomic analyses using microarray and comparative genomic hybridization (aCGH)-based single nucleotide polymorphism (SNP) and copy number variation (CNV) were also conducted. These 10 HLA-homozygous iPSC lines match 41.07% of the Korean population. Comparative analysis of HLA population data shows that they are also of use in other Asian populations, such as Japan, with some limited utility in ethnically diverse populations, such as the UK. Taken together, the generation of the 10 most frequent Korean HLA-homozygous iPSC lines serves as a useful pointer for the development of optimal methods for iPSC generation and quality control and indicates the benefits and limitations of collaborative HLA driven selection of donors for future stocking of worldwide iPSC haplobanks. Stem Cells 2018;36:1552-1566.

Safety of blood, blood derivatives, and plasma-derived products.

There has been concern for several decades around the possibility that prion diseases may be transmissible by blood components and / or plasma products. Whilst the evidence in respect of transmission of sporadic Creutzfeldt-Jakob disease (CJD) is largely circumstantial, the identification of variant CJD gave rise to increased concern due to the evidence of prion accumulation in peripheral lymphoid tissue at the time of clinical disease. A series of studies of appendix tissues in the United Kingdom revealed prion accumulation in around 1 / 2000 of the individuals tested and raised further concern that there may be a significant proportion of the healthy population with subclinical infection posing an increased risk of transmission by substances of human origin (blood, plasma, tissues, organs) and interventional medical and surgical procedures. The former risk was realized with transmission of variant CJD infection to four individuals becoming evident between 2004 and 2006. These concerns precipitated significant changes to donor selection criteria internationally, to blood processing in the United Kingdom with the introduction of universal leucodepletion, and to the use of UK plasma for fractionation to plasma products. Considerable effort has also been invested in the development of peripheral blood assays for subclinical variant CJD and of prion reduction filters for blood components, though to date these technologies have not achieved routine clinical implementation. Whilst the variant CJD outbreak appears to be receding, continued vigilance is required in respect of the risks posed by all prion diseases to blood safety.

Development, functional characterization and validation of methodology for GMP-compliant manufacture of phagocytic macrophages: A novel cellular therapeutic for liver cirrhosis.

BACKGROUND AIMS: Autologous macrophage therapy represents a potentially significant therapeutic advance for the treatment of severe progressive liver cirrhosis. Administration of macrophages has been shown to reduce inflammation and drive fibrotic scar breakdown and tissue repair in relevant models. This therapeutic approach is being assessed for safety and feasibility in a first-in-human trial (MAcrophages Therapy for liver CirrHosis [MATCH] trial). METHODS: We outline the development and validation phases of GMP production. This includes use of the CliniMACS Prodigy cell sorting system to isolate CD14+ cells; optimizing macrophage culture conditions, assessing cellular identity, product purity, functional capability and determining the stability of the final cell product. RESULTS: The GMP-compliant macrophage products have a high level of purity and viability, and have a consistent phenotypic profile, expressing high levels of mature macrophage markers 25F9 and CD206 and low levels of CCR2. The macrophages demonstrate effective phagocytic capacity, are constitutively oriented to an anti-inflammatory profile and remain responsive to cytokine and TLR stimulation. The process validation shows that the cell product in excipient is remarkably robust, consistently passing the viability and phenotypic release criteria up to 48 hours after harvest. CONCLUSIONS: This is the first report of validation of a large-scale, fully Good Manufacturing Practice-compliant, autologous macrophage cell therapy product for the potential treatment of cirrhosis. Phenotypic and functional assays confirm that these cells remain functionally viable for up to 48 h, allowing significant flexibility in administration to patients.

A prion reduction filter does not completely remove endogenous prion infectivity from sheep blood.

BACKGROUND: Variant Creutzfeldt-Jakob disease (vCJD) is a transmissible spongiform encephalopathy affecting humans, acquired initially through infection with bovine spongiform encephalopathy (BSE). A small number of vCJD cases have been acquired through the transfusion of blood from asymptomatic donors who subsequently developed vCJD. Filter devices that selectively bind the infectious agent associated with prion disease have been developed for removal of infection from blood. This study independently assessed one such filter, the P-CAPT filter, for efficacy in removing infectivity associated with the BSE agent in sheep blood. The sheep BSE model has previously been used to evaluate the distribution of infectivity in clinically relevant blood components. This is the first study to assess the ability of the P-CAPT filter to remove endogenous infectivity associated with blood components prepared from a large animal model. STUDY DESIGN AND METHODS: Paired units of leukoreduced red blood cells (LR-RBCs) were prepared from donors at the clinical stage of infection and confirmed as having BSE. One cohort of recipients was transfused with LR-RBCs alone, whereas a parallel cohort received LR and P-CAPT-filtered RBCs (LR-RBCs-P-CAPT). RESULTS: Of 14 recipients, two have been confirmed as having BSE. These sheep had received LR-RBCs and LR-RBCs-P-CAPT from the same donor. CONCLUSIONS: The results indicate that, after leukoreduction and P-CAPT filtration, there can still be sufficient residual infectivity in sheep RBCs to transmit infection when transfused into a susceptible recipient.