Collection efficiency of mononuclear cells in offline extracorporeal photopheresis: can processing time be shortened?

BACKGROUND

Extracorporeal photopheresis (ECP) is a well-established but lengthy and burdensome cell-based therapy for various diseases such as cutaneous T-cell lymphoma, graft-versus-host disease and organ rejection after transplantation. The number of mononuclear cells (MNCs) that needs to be collected to obtain a clinical response to ECP is still under debate. The purpose of this retrospective study was to determine the number of lymphocytes, monocytes and neutrophils in mononuclear cell products (MCP) by flow cytometry and the collection efficiency in the offline ECP setting.

MATERIALS AND METHODS

We collected data from 10 different patients undergoing 162 ECP procedures using the Spectra Optia device for MNC collection. White blood cell (WBC) count of MCP was determined using a hematology analyzer. MNCs were analyzed for CD45 and CD14 expression by flow cytometry to exactly determine the collected lymphocyte and monocyte fractions.

RESULTS

Collected MCP showed high cell yields with 55.3×106/kg MNCs and 41.1×106/kg lymphocytes. MCP were characterized by high MNC (81.3%) and low neutrophils (18.7%) percentage. Mean collection efficiency for WBCs and for MNCs was 23.9% and 62.0%, respectively. The MNC fraction showed a moderate to high correlation between peripheral blood cell count of patients and MCP count.

DISCUSSION

This study is one of a few reports showing the monocyte-to-lymphocyte relation in MCP for ECP determined by flow cytometry. In comparison to historical data from inline ECP, the offline ECP processing one total blood volume results in considerably higher cell yields. For this reason, and to reduce the burden on patients, we propose that the offline ECP processing time can be substantially reduced.

Epstein-Barr virus reactivation is not causative for post-COVID-19-syndrome in individuals with asymptomatic or mild SARS-CoV-2 disease course

PURPOSE

Post-COVID-19-Syndrome (PCS) frequently occurs after an infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). However, the understanding of causative mechanisms is still limited. Aim of this study was to determine the PCS rate among SARS-CoV-2 seropositive blood donors as representatives of supposedly healthy adults, who had experienced an asymptomatic or mild COVID-19 disease course, and to examine whether Epstein-Barr virus (EBV) is reactivated in individuals reporting PCS.

METHODS

The PCS rate was determined using questionnaires that included questions about infection and persistent symptoms. Pre-pandemic blood samples and samples collected at regular, pre-defined times after a SARS-CoV-2 infection were analysed for neopterin, a marker for antiviral immune responses, by an enzyme-linked immunosorbent assay (ELISA). Additionally, we determined the rate of SARS-CoV-2 anti-N total antibodies using an electrochemiluminescence immunoassay (ECLIA). Furthermore, quantitative real-time polymerase chain reaction (qPCR) to detect EBV DNA and ECLIA screening for EBV viral capsid-antigen (VCA) IgM, IgG and EBV nuclear antigen 1 (EBNA) IgG were performed.

RESULTS

Our data reveal that 18% of all infections result in PCS, with symptoms lasting for up to one year. In individuals reporting PCS, no elevated levels of neopterin were detected, indicating no persisting pro-inflammatory, antiviral immune response. SARS-CoV-2 antibody levels were declining in all participants in comparable manner over time, pointing to a successful virus clearance. In individuals with PCS, no EBV DNA could be detected. Furthermore, no differences in EBV specific antibody levels could be shown in PCS groups compared to non-PCS groups.

CONCLUSION

Our data suggest that PCS in per se healthy, immunocompetent adults cannot be ascribed to a reactivation of EBV.

Sample Buffer Containing Guanidine-Hydrochloride Combines Biological Safety and RNA Preservation for SARS-CoV-2 Molecular Diagnostics

The COVID-19 pandemic has elicited the need to analyse and store large amounts of infectious samples for laboratory diagnostics. Therefore, there has been a demand for sample storage buffers that effectively inactivate infectious viral particles while simultaneously preserving the viral RNA. Here, we present a storage buffer containing guanidine-hydrochloride that fulfils both requirements. Its ability to preserve RNA stability was confirmed by RT-qPCR, and virus-inactivating properties were tested by tissue culture infectious dose assay. Our data revealed that RNA from samples diluted in this storage buffer was efficiently preserved. Spiking samples with RNase A resulted in RNAse concentrations up to 100 ng/mL being efficiently inhibited, whereas spiking samples with infectious SARS-CoV-2 particles demonstrated rapid virus inactivation. In addition, our buffer demonstrated good compatibility with several commercially available RNA extraction platforms. The presented guanidine-hydrochloride-based storage buffer efficiently inactivates infectious SARS-CoV-2 particles and supports viral RNA stability, leading to a reduced infection risk during sample analysis and an increased period for follow-up analysis, such as sequencing for virus variants. Because the presented buffer is uncomplicated to manufacture and compatible with a variety of commercially available test systems, its application can support and improve SARS-CoV-2 laboratory diagnostics worldwide.

Persistence of Naturally Acquired and Functional SARS-CoV-2 Antibodies in Blood Donors One Year after Infection

The developmental course of antibodies produced after a SARS-CoV-2 infection has been insufficiently investigated so far. Therefore, the aim of this study was to investigate the dynamics of SARS-CoV-2 antibody levels against the viral nucleocapsid- and spike-protein among Austrian blood donors as a representative group of a supposedly healthy population within the first year after a SARS-CoV-2 infection. The impact of age, sex, vaccination status, AB0-blood group and awareness about the infection was evaluated. Our study shows that the level of anti-N antibodies is declining, while anti-S antibody levels remain stable. Antibodies detected were functional in vitro. Age, sex and blood group do not influence antibody dynamics. However, blood group AB shows significantly lower antibody levels and in vitro functionality compared to other blood groups. Our data reveal that one out of five individuals was not aware of a previous SARS-CoV-2 infection and that the disease course neither affects the level of antibody production nor the in vitro functionality. We also found that 14% of participants show persisting COVID-19-related symptoms for up to nine months. Our results provide valuable insights into the dynamics of the immune response after a SARS-CoV-2 infection in a representative cohort of adult blood donors in Central Europe.

First-in-human intracochlear application of human stromal cell-derived extracellular vesicles

Extracellular vesicles (EVs) derived from the secretome of human mesenchymal stromal cells (MSC) contain numerous factors that are known to exert anti‐inflammatory effects. MSC‐EVs may serve as promising cell‐based therapeutics for the inner ear to attenuate inflammation‐based side effects from cochlear implantation which represents an unmet clinical need. In an individual treatment performed on a ‘named patient basis’, we intraoperatively applied allogeneic umbilical cord‐derived MSC‐EVs (UC‐MSC‐EVs) produced according to good manufacturing practice. A 55‐year‐old patient suffering from Menière's disease was treated with intracochlear delivery of EVs prior to the insertion of a cochlear implant. This first‐in‐human use of UC‐MSC‐EVs demonstrates the feasibility of this novel adjuvant therapeutic approach. The safety and efficacy of intracochlear EV‐application to attenuate side effects of cochlea implants have to be determined in controlled clinical trials.

Human Platelet Lysate for Good Manufacturing Practice-Compliant Cell Production

Numerous cell-based therapeutics are currently being tested in clinical trials. Human platelet lysate (HPL) is a valuable alternative to fetal bovine serum as a cell culture medium supplement for a variety of different cell types. HPL as a raw material permits animal serum-free cell propagation with highly efficient stimulation of cell proliferation, enabling humanized manufacturing of cell therapeutics within a reasonable timeframe. Providers of HPL have to consider dedicated quality issues regarding identity, purity, potency, traceability and safety. Release criteria have to be defined, characterizing the suitability of HPL batches for the support of a specific cell culture. Fresh or expired platelet concentrates from healthy blood donors are the starting material for HPL preparation, according to regulatory requirements. Pooling of individual platelet lysate units into one HPL batch can balance donor variation with regard to essential platelet-derived growth factors and cytokines. The increasingly applied pathogen reduction technologies will further increase HPL safety. In this review article, aspects and regulatory requirements of whole blood donation and details of human platelet lysate manufacturing are presented. International guidelines for raw materials are discussed, and defined quality controls, as well as release criteria for safe and GMP-compliant HPL production, are summarized.

Upregulation of mitotic bookmarking factors during enhanced proliferation of human stromal cells in human platelet lysate

BACKGROUND

Innovative human stromal cell therapeutics require xeno-free culture conditions. Various formulations of human platelet lysate (HPL) are efficient alternatives for fetal bovine serum (FBS). However, a consistent lack of standardized manufacturing protocols and quality criteria hampers comparability of HPL-products. Aim of this study was to compare the biochemical composition of three differential HPL-preparations with FBS and to investigate their impact on stromal cell biology.

METHODS

Stromal cells were isolated from bone marrow (BM), white adipose tissue (WAT) and umbilical cord (UC) and cultured in medium supplemented with pooled HPL (pHPL), fibrinogen-depleted serum-converted pHPL (pHPLS), mechanically fibrinogen-depleted pHPL (mcpHPL) and FBS. Biochemical parameters were analyzed in comparison to standard values in whole blood. Distinct growth factors and cytokines were measured by bead-based multiplex technology. Flow cytometry of stromal cell immunophenotype, in vitro differentiation, and mRNA expression analysis of transcription factors SOX2, KLF4, cMYC, OCT4 and NANOG were performed.

RESULTS

Biochemical parameters were comparable in all pHPL preparations, but to some extent different to FBS. Total protein, glucose, cholesterol and Na⁺ were elevated in pHPL preparations, K⁺ and Fe³⁺ levels were higher in FBS. Compared to FBS, pHPL-based media significantly enhanced stromal cell propagation. Characteristic immunophenotype and in vitro differentiation potential were maintained in all four culture conditions. The analysis of growth factors and cytokines revealed distinct levels depending on the pre-existence in pHPL, consumption or secretion by the stromal cells. Interestingly, mRNA expression of the transcription and mitotic bookmarking factors cMYC and KLF4 was significantly enhanced in a source dependent manner in stromal cells cultured in pHPL- compared to FBS-supplemented media. SOX2 mRNA expression of all stromal cell types was increased in all pHPL culture conditions.

CONCLUSION

All pHPL-supplemented media equally supported proliferation of WAT- and UC-derived stromal cells significantly better than FBS. Mitotic bookmarking factors, known to enable a quick re-entry to the cell cycle, were significantly enhanced in pHPL-expanded cells. Our results support a better characterization and standardization of humanized culture media for stromal cell-based medicinal products.

Heparin Differentially Impacts Gene Expression of Stromal Cells from Various Tissues

Pooled human platelet lysate (pHPL) is increasingly used as replacement of animal serum for manufacturing of stromal cell therapeutics. Porcine heparin is commonly applied to avoid clotting of pHPL-supplemented medium but the influence of heparin on cell behavior is still unclear. Aim of this study was to investigate cellular uptake of heparin by fluoresceinamine-labeling and its impact on expression of genes, proteins and function of human stromal cells derived from bone marrow (BM), umbilical cord (UC) and white adipose tissue (WAT). Cells were isolated and propagated using various pHPL-supplemented media with or without heparin. Flow cytometry and immunocytochemistry showed differential cellular internalization and lysosomal accumulation of heparin. Transcriptome profiling revealed regulation of distinct gene sets by heparin including signaling cascades involved in proliferation, cell adhesion, apoptosis, inflammation and angiogenesis, depending on stromal cell origin. The influence of heparin on the WNT, PDGF, NOTCH and TGFbeta signaling pathways was further analyzed by a bead-based western blot revealing most alterations in BM-derived stromal cells. Despite these observations heparin had no substantial effect on long-term proliferation and in vitro tri-lineage differentiation of stromal cells, indicating compatibility for clinically applied cell products.

Identification of new molecular targets for PET imaging of the microglial anti-inflammatory activation state

Microglia are potential targets for therapeutic intervention in neurological and neurodegenerative diseases affecting the central nervous system. In order to assess the efficacy of therapies aimed to reduce the tissue damaging activities of microglia and/or to promote the protective potential of these cells, suitable pre-clinical and clinical tools for the in vivo analysis of microglia activities and dynamics are required. The aim of this work was to identify new translational markers of the anti-inflammatory / protective state of microglia for the development of novel PET tracers.

Methods: New translational markers of the anti-inflammatory/protective activation state of microglia were selected by bioinformatic approaches and were in vitro and ex vivo validated by qPCR and immunohistochemistry in rodent and human samples. Once a viable marker was identified, a novel PET tracer was developed. This tracer was subsequently confirmed by autoradiography experiments in murine and human brain tissues.

Results: Here we provide evidence that P2RY12 expression increases in murine and human microglia following exposure to anti-inflammatory stimuli, and that its expression is modulated in the reparative phase of experimental and clinical stroke. We then synthesized a novel carbon-11 labeled tracer targeting P2RY12, showing increased binding in brain sections of mice treated with IL4, and low binding to brain sections of a murine stroke model and of a stroke patient.

Conclusion: This study provides new translational targets for PET tracers for the anti-inflammatory/protective activation state of microglia and shows the potential of a rationale-based approach. It therefore paves the way for the development of novel non-invasive methodologies aimed to monitor the success of therapeutic approaches in various neurological diseases.

Selection of Tissue Factor-Deficient Cell Transplants as a Novel Strategy for Improving Hemocompatibility of Human Bone Marrow Stromal Cells

Intravascular transplantation of tissue factor (TF)-bearing cells elicits an instant blood-mediated inflammatory reaction (IBMIR) resulting in thrombotic complications and reduced engraftment. Here we studied the hemocompatibility of commonly used human white adipose tissue (WAT), umbilical cord (UC) and bone marrow stromal cells (BMSC) and devised a possible strategy for safe and efficient stromal cell transplantation.

Methods: Stromal cell identity, purity, and TF expression was tested by RTQ-PCR, flow cytometry and immunohistochemistry. Pro-coagulant activity and fibrin clot formation/stabilization was measured In Vitro by viscoelastic rotational plasma-thromboelastometry and in vivo by injecting sorted human stromal cells intravenously into rats. The impact of TF was verified in factor VII-deficient plasma and by sort-depleting TF/CD142⁺ BMSC.

Results: We found significantly less TF expression by a subpopulation of BMSC corresponding to reduced pro-coagulant activity. UC and WAT stroma showed broad TF expression and durable clotting. Higher cell numbers significantly increased clot formation partially dependent on coagulation factor VII. Depleting the TF/CD142⁺ subpopulation significantly ameliorated BMSC's hemocompatibility without affecting immunomodulation. TF-deficient BMSC did not produce thromboembolism in vivo, comparing favorably to massive intravascular thrombosis induction by TF-expressing stromal cells.

Conclusion: We demonstrate that plasma-based thromboelastometry provides a reliable tool to detect pro-coagulant activity of therapeutic cells. Selecting TF-deficient BMSC is a novel strategy for improving cell therapy applicability by reducing cell dose-dependent IBMIR risk. The particularly strong pro-coagulant activity of UC and WAT preparations sounds an additional note of caution regarding uncritical systemic application of stromal cells, particularly from non-hematopoietic extravascular sources.

Applying extracellular vesicles based therapeutics in clinical trials - an ISEV position paper

Extracellular vesicles (EVs), such as exosomes and microvesicles, are released by different cell types and participate in physiological and pathophysiological processes. EVs mediate intercellular communication as cell-derived extracellular signalling organelles that transmit specific information from their cell of origin to their target cells. As a result of these properties, EVs of defined cell types may serve as novel tools for various therapeutic approaches, including (a) anti-tumour therapy, (b) pathogen vaccination, (c) immune-modulatory and regenerative therapies and (d) drug delivery. The translation of EVs into clinical therapies requires the categorization of EV-based therapeutics in compliance with existing regulatory frameworks. As the classification defines subsequent requirements for manufacturing, quality control and clinical investigation, it is of major importance to define whether EVs are considered the active drug components or primarily serve as drug delivery vehicles. For an effective and particularly safe translation of EV-based therapies into clinical practice, a high level of cooperation between researchers, clinicians and competent authorities is essential. In this position statement, basic and clinical scientists, as members of the International Society for Extracellular Vesicles (ISEV) and of the European Cooperation in Science and Technology (COST) program of the European Union, namely European Network on Microvesicles and Exosomes in Health and Disease (ME-HaD), summarize recent developments and the current knowledge of EV-based therapies. Aspects of safety and regulatory requirements that must be considered for pharmaceutical manufacturing and clinical application are highlighted. Production and quality control processes are discussed. Strategies to promote the therapeutic application of EVs in future clinical studies are addressed.

Mechanical fibrinogen-depletion supports heparin-free mesenchymal stem cell propagation in human platelet lysate

Background

Pooled human platelet lysate (pHPL) is an efficient alternative to xenogenic supplements for ex vivo expansion of mesenchymal stem cells (MSCs) in clinical studies. Currently, porcine heparin is used in pHPL-supplemented medium to prevent clotting due to plasmatic coagulation factors. We therefore searched for an efficient and reproducible medium preparation method that avoids clot formation while omitting animal-derived heparin.

Methods

We established a protocol to deplete fibrinogen by clotting of pHPL in medium, subsequent mechanical hydrogel disruption and removal of the fibrin pellet. After primary culture, bone-marrow and umbilical cord derived MSCs were tested for surface markers by flow cytometry and for trilineage differentiation capacity. Proliferation and clonogenicity were analyzed for three passages.

Results

The proposed clotting procedure reduced fibrinogen more than 1000-fold, while a volume recovery of 99.5 % was obtained. All MSC types were propagated in standard and fibrinogen-depleted medium. Flow cytometric phenotype profiles and adipogenic, osteogenic and chondrogenic differentiation potential in vitro were independent of MSC-source or medium type. Enhanced proliferation of MSCs was observed in the absence of fibrinogen but presence of heparin compared to standard medium. Interestingly, this proliferative response to heparin was not detected after an initial contact with fibrinogen during the isolation procedure.

Conclusions

Here, we present an efficient, reproducible and economical method in compliance to good manufacturing practice for the preparation of MSC media avoiding xenogenic components and suitable for clinical studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0717-4) contains supplementary material, which is available to authorized users.

Hedgehog/GLI signaling activates suppressor of cytokine signaling 1 (SOCS1) in epidermal and neural tumor cells

Sustained hedgehog (Hh) signaling mediated by the GLI transcription factors is implicated in many types of cancer. Identification of Hh/GLI target genes modulating the activity of other pathways involved in tumor development promise to open new ways for better understanding of tumor development and maintenance. Here we show that SOCS1 is a direct target of Hh/GLI signaling in human keratinocytes and medulloblastoma cells. SOCS1 is a potent inhibitor of interferon gamma (IFN-y)/STAT1 signaling. IFN-у/STAT1 signaling can induce cell cycle arrest, apoptosis and anti-tumor immunity. The transcription factors GLI1 and GLI2 activate the SOCS1 promoter, which contains five putative GLI binding sites, and GLI2 binding to the promoter was shown by chromatin immunoprecipitation. Consistent with a role of GLI in SOCS1 regulation, STAT1 phosphorylation is reduced in cells with active Hh/GLI signaling and IFN-у/STAT1 target gene activation is decreased. Furthermore, IFN-у signaling is restored by shRNA mediated knock down of SOCS1. Here, we identify SOCS1 as a novel Hh/GLI target gene, indicating a negative role of Hh/GLI pathway in IFN-y/STAT1 signaling.

Non-consensus GLI binding sites in Hedgehog target gene regulation

Background

The GLI transcription factors, mediators of the hedgehog signal bind with high affinity to the consensus sequence GACCACCCA. The affinity of variant single substitutions in GLI binding sites has been measured systematically, but the affinities of the variant binding sites appears low compared to the frequency of occurrence of variant sites in known GLI target gene promoters.

Results

We quantified transcriptional activation by GLI using PTCH1 promoter based luciferase reporters containing all single substitutions of the GLI consensus binding site. As expected variants with very low affinity did not activate the reporter. Many lower affinity binding sequences are, however, functional in the presence of moderate GLI concentration. Using two natural non-consensus GLI site promoters we showed that substitution of the variant sequences by consensus leads to comparable activity.

Conclusions

Variant GLI binding sites with relatively low affinity can within natural promoters lead to strong transcriptional activation. This may facilitate the identification of additional direct GLI target genes.

Cooperation between GLI and JUN enhances transcription of JUN and selected GLI target genes

Sustained Hedgehog (HH) signaling is implicated in basal cell carcinoma of the skin and other types of cancer. Here we show that GLI1 and GLI2, the main transcriptional activators of the HH pathway, directly regulate expression of the activator protein 1 (AP-1) family member JUN, a transcription factor controlling keratinocyte proliferation and skin homeostasis. Activation of the JUN promoter by GLI is dependent on a GLI-binding site and the AP-1 sites known to be involved in self-activation of JUN. Transcription of JUN is greatly enhanced in the presence of GLI and requires activated JUN protein. GLI2act is a more potent activator than GLI1 in these experiments and physical interaction with phosphorylated JUN was only detected for GLI2act. The synergistic effect of GLI and JUN extends to the activation of further GLI target genes as shown by shRNA-mediated knockdown of JUN in human keratinocytes. Some of these cooperatively activated genes are involved in cell-cycle progression, which is consistent with a significant reduction of the proliferative potential of GLI in the absence of JUN. These results suggest a novel connection between HH/GLI pathway activity and JUN, which may contribute to the oncogenic activity of HH/GLI signaling in skin.