Development of a closed-system process for clinical-scale generation of DCs: evaluation of two monocyte-enrichment methods and two culture containers

Closing the system: production of viral antigen-presenting dendritic cells eliciting specific CD8+ T cell activation in fluorinated ethylene propylene cell culture bags

Background

A major obstacle to anti-viral and -tumor cell vaccination and T cell immunotherapy is the ability to produce dendritic cells (DCs) in a suitable clinical setting. It is imperative to develop closed cell culture systems to accelerate the translation of promising DC-based cell therapy products to the clinic. The objective of this study was to investigate whether viral antigen-loaded monocyte-derived DCs (Mo-DCs) capable of eliciting specific T cell activation can be manufactured in fluorinated ethylene propylene (FEP) bags.

Methods

Mo-DCs were generated through a protocol applying cytokine cocktails combined with lipopolysaccharide or with a CMV viral peptide antigen in conventional tissue culture polystyrene (TCPS) or FEP culture vessels. Research-scale (< 10 mL) FEP bags were implemented to increase R&D throughput. DC surface marker profiles, cytokine production, and ability to activate antigen-specific cytotoxic T cells were characterized.

Results

Monocyte differentiation into Mo-DCs led to the loss of CD14 expression with concomitant upregulation of CD80, CD83 and CD86. Significantly increased levels of IL-10 and IL-12 were observed after maturation on day 9. Antigen-pulsed Mo-DCs activated antigen-responsive CD8⁺ cytotoxic T cells. No significant differences in surface marker expression or tetramer-specific T cell activating potency of Mo-DCs were observed between TCPS and FEP culture vessels.

Conclusions

Our findings demonstrate that viral antigen-loaded Mo-DCs produced in downscaled FEP bags can elicit specific T cell responses. In view of the dire clinical need for closed system DC manufacturing, FEP bags represent an attractive option to accelerate the translation of promising emerging DC-based immunotherapies.

Bags versus flasks: a comparison of cell culture systems for the production of dendritic cell-based immunotherapies

In recent years, cell-based therapies targeting the immune system have emerged as promising strategies for cancer treatment. This review summarizes manufacturing challenges related to production of antigen presenting cells as a patient-tailored cancer therapy. Understanding cell-material interactions is essential because in vitro cell culture manipulations to obtain mature antigen-producing cells can significantly alter their in vivo performance. Traditional antigen-producing cell culture protocols often rely on cell adhesion to surface-treated hydrophilic polystyrene flasks. More recent commercial and investigational cancer immunotherapy products were manufactured using suspension cell culture in closed hydrophobic fluoropolymer bags. The shift to closed cell culture systems can decrease risks of contamination by individual operators, as well as facilitate scale-up and automation. Selecting closed cell culture bags over traditional open culture systems entails different handling procedures and processing controls, which can affect product quality. Changes in culture vessels also entail changes in vessel materials and geometry, which may alter the cell microenvironment and resulting cell fate decisions. Strategically designed culture systems will pave the way for the generation of more sophisticated and highly potent cell-based cancer vaccines. As an increasing number of cell-based therapies enter the clinic, the selection of appropriate cell culture vessels and materials becomes a critical consideration that can impact the therapeutic efficacy of the product, and hence clinical outcomes and patient quality of life.

Dendritic cells transfected with adenoviral vectors as vaccines

Dendritic cells (DCs) are critical to the initiation of a T-cell response. They constitute the most potent antigen-presenting cell (APC) endowed with the unique capacity to stimulate an antigen-specific T-cell responses by naïve T cells. Adenoviruses (Ad) have high transduction efficiency for many cell types including cells of hematopoietic origin independent of their mitotic status, and replication-defective Ad have demonstrated a safety profile clinically. Further, Ad vectors provide a high level of transgene expression, and Ad-transduced DCs can effectively present antigenic proteins. In this chapter, we outline a functionally closed, good manufacturing protocol for the differentiation of monocytes into DCs and transduction by Ad vectors. Basic functional and phenotypic release assays are provided, as well as contrasting research approaches for Ad-transduced DC-based vaccines.

Stimulating surface molecules, Th1-polarizing cytokines, proven trafficking--a new protocol for the generation of clinical-grade dendritic cells

BACKGROUND AIMS

Dendritic cells (DC) have been vigorously investigated as an immunological basis for therapeutic vaccination against cancer and infections, even among patients after allogeneic stem cell transplantation.

METHODS

Effective induction of cell-mediated immunity strongly depends on the ability of DC to (i) migrate to the draining lymphoid organs mediated by chemokine receptors, (ii) prime T cells through high expression of costimulatory molecules and major histocompatibility complexes and (iii) secret Th1-polarizing cytokines such as Interleukin-12 (IL-12). However, there is no protocol to generate fully matured and functional DC according to methodical requirements of current good manufacturing practice (CGMP) guidelines.

RESULTS

We established a protocol conforming to CGMP standards that permits the generation of fully matured and functional DC on the basis of cell culture in adherence bags with the use of serum-free media with a maturation cocktail, containing tumor necrosis factor-alpha/Interferon-alpha/polyinosinic:polycytidylic acid. Our DC superiorly display three critical features for an effective induction of cell-mediated immunity without evidence of exhaustion, along with its ability to prime infectious or tumor-specific T cells in a short-term cell culture.

CONCLUSIONS

Our newly developed protocol offers an attractive method to produce fully matured Th1-polarizing DC with proven migratory and stimulatory capacity for any clinical application according to CGMP standards.

Optimizing parameters for clinical-scale production of high IL-12 secreting dendritic cells pulsed with oxidized whole tumor cell lysate

BACKGROUND

Dendritic cells (DCs) are the most potent antigen-presenting cell population for activating tumor-specific T cells. Due to the wide range of methods for generating DCs, there is no common protocol or defined set of criteria to validate the immunogenicity and function of DC vaccines.

METHODS

Monocyte-derived DCs were generated during 4 days of culture with recombinant granulocyte-macrophage colony stimulating factor and interleukin-4, and pulsed with tumor lysate produced by hypochlorous acid oxidation of tumor cells. Different culture parameters for clinical-scale DC preparation were investigated, including: 1) culture media; 2) culture surface; 3) duration of activating DCs with lipopolysaccharide (LPS) and interferon (IFN)-gamma; 4) method of DC harvest; and 5) cryomedia and final DC product formulation.

RESULTS

DCs cultured in CellGenix DC media containing 2% human AB serum expressed higher levels of maturation markers following lysate-loading and maturation compared to culturing with serum-free CellGenix DC media or AIM-V media, or 2% AB serum supplemented AIM-V media. Nunclon™Δ surface, but not Corning(®) tissue-culture treated surface and Corning(®) ultra-low attachment surface, were suitable for generating an optimal DC phenotype. Recombinant trypsin resulted in reduced major histocompatibility complex (MHC) Class I and II expression on mature lysate-loaded DCs, however presentation of MHC Class I peptides by DCs was not impaired and cell viability was higher compared to cell scraping. Preservation of DCs with an infusible cryomedia containing Plasma-Lyte A, dextrose, sodium chloride injection, human serum albumin, and DMSO yielded higher cell viability compared to using human AB serum containing 10% DMSO. Finally, activating DCs for 16 hours with LPS and IFN-γ stimulated robust mixed leukocyte reactions (MLRs), and high IL-12p70 production in vitro that continued for 24 hours after the cryopreserved DCs were thawed and replated in fresh media.

CONCLUSIONS

This study examined criteria including DC phenotype, viability, IL-12p70 production and the ability to stimulate MLR as metrics of whole oxidized tumor lysate-pulsed DC immunogenicity and functionality. Development and optimization of this unique method is now being tested in a clinical trial of autologous oxidized tumor lysate-pulsed DC in clinical-scale in recurrent ovarian, primary peritoneal or fallopian tube cancer (NCT01132014).

Human dendritic cells and transplant outcome

Early interest in dendritic cells (DC) in transplantation centered on the role of graft interstitial DC in the instigation of rejection. Much information has subsequently accumulated concerning the phenotypic and functional diversity of these rare, migratory, bone marrow-derived antigen-presenting cells, and their role in the induction and regulation of immunity. Detailed insights have emerged from studies of freshly isolated or in vitro-propagated DC, and from analyses of their function in experimental animal models. The functional plasticity of these uniquely well-equipped antigen-presenting cells is reflected in their ability not only to induce alloimmune responses, but also to serve as potential targets and therapeutic agents for the long-term improvement of transplant outcome. Notably, however, a great deal remains to be understood about the immunobiology of DC populations in relation to human transplant outcome. Herein, we briefly review aspects of human DC biology in organ and bone marrow transplantation, the potential of these cells for monitoring outcome, and the role of DC in development of vaccines to protect against infectious disease or to promote allograft tolerance.

Automated CD14+ monocyte collection with the autoMNC program of the COM.TEC cell separator

BACKGROUND

The standard mononuclear cell (MNC) program of the COM.TEC device (Fresenius HemoCare GmbH) showed excellent collection efficiency of CD14+ monocytes. A major disadvantage was high content of residual cells in MNC harvests, which could influence dendritic cell (DC) culture.

STUDY DESIGN AND METHODS

The autoMNC program (COM.TEC) was compared with the standard MNC program (n = 12). Additionally, two cycle volumes (300 mL vs. 450 mL, n = 19) were compared (standard MNC program). Samples were assayed for white blood cells (WBCs), red blood cells (RBCs), granulocytes (PMNs), hematocrit, and platelets (PLTs) on an automated blood cell counter (Sysmex K 4500, TAO Medical). CD14+ cells were analyzed by flow cytometry (FACSCalibur, BD).

RESULTS

The autoMNC program produced 1.33 x 10(9) +/- 0.36 x 10(9) CD14+ cells, 5.60 x 10(11) +/- 0.97 x 10(11) PLTs, and 1.43 x 10(11) +/- 0.37 x 10(11) RBCs. Compared to the standard MNC program, significantly higher PLT yields but lower RBC yields and product volume were harvested. Increasing the CV from 300 to 450 mL dropped the product volume, residual PLTs, and RBCs significantly, whereas WBC and monocyte yields did not change. The WBC predonation counts of donors correlated significantly with monocyte yields.

CONCLUSIONS

The autoMNC program reduced the buffy coat (BC) volume and RBC yields in products compared to the standard MNC program. Increasing the CV (standard MNC program) reduced residual PLTs, RBCs, and the BC volume of MNC harvests. The donor WBC predonation count was a good predictor for the monocyte yield of products.

Current approaches in dendritic cell generation and future implications for cancer immunotherapy

The discovery of tumor-associated antigens, which are either selectively or preferentially expressed by tumors, together with an improved insight in dendritic cell biology illustrating their key function in the immune system, have provided a rationale to initiate dendritic cell-based cancer immunotherapy trials. Nevertheless, dendritic cell vaccination is in an early stage, as methods for preparing tumor antigen presenting dendritic cells and improving their immunostimulatory function are continuously being optimized. In addition, recent improvements in immunomonitoring have emphasized the need for careful design of this part of the trials. Still, valuable proofs-of-principle have been obtained, which favor the use of dendritic cells in subsequent, more standardized clinical trials. Here, we review the recent developments in clinical DC generation, antigen loading methods and immunomonitoring approaches for DC-based trials.

Effective clinical-scale production of dendritic cell vaccines by monocyte elutriation directly in medium, subsequent culture in bags and final antigen loading using peptides or RNA transfection

Dendritic cell (DC) vaccination approaches are advancing fast into the clinic. The major obstacle for further improvement is the current lack of a simple functionally "closed" system to generate standardized monocyte-derived (mo) DC vaccines. Here, we significantly optimized the use of the Elutra counterflow elutriation system to enrich monocytic DC precursors by (1) developing an algorithm to avoid red blood cell debulking and associated monocyte loss before elutriation, and (2) by elutriation directly in culture medium rather than phosphate-buffered saline. Upon elutriation the bags containing the collected monocytes are simply transferred into the incubator to generate DC progeny as the final "open" washing step is no longer required. Elutriation resulted in significantly more (> or = 2-fold) and purer DC than the standard gradient centrifugation/adherence-based monocyte enrichment, whereas morphology, maturation markers, viability, migratory capacity, and T cell stimulatory capacity were identical. Subsequently, we compared RNA transfection, as this is an increasingly used approach to load DC with antigen. Elutra-derived and adherence-derived DC could be electroporated with similar, high efficiency (on average >85% green fluorescence protein positive), and appeared also equal in antigen expression kinetics. Both Elutra-derived and adherence-derived DC, when loaded with the MelanA peptide or electroporated with MelanA RNA, showed a high T cell stimulation capacity, that is, priming of MelanA-specific CD8+ T cells. Our optimized Elutra-based procedure is straightforward, clearly superior to the standard gradient centrifugation/plastic adherence protocol, and now allows the generation of large numbers of peptide-loaded or RNA-transfected DC in a functionally closed system.

Regenerative Medicine Bioprocessing: Building a Conceptual Framework Based on Early Studies

This paper reviews early studies of regenerative medicine using human cells and engineered tissues progressing from a laboratory-centered manual procedure toward automated manufacture. It then examines the distinctive bioprocesses by which autologous human material must be produced, the degree of simplification allowed by use of allogeneic cell lines and engineered tissue derived from them, and issues that affect both cell types. The paper concludes by drawing upon this discussion to suggest some factors that will determine how regenerative medicine bioprocessing can progress to provide many units of material economically.

Sterility testing of cell therapy products: parallel comparison of automated methods with a CFR-compliant method

BACKGROUND

Automated blood culture systems are not FDA-approved for sterility testing of human cells, tissues, or cellular- or tissue-based products. It was previously demonstrated that BacT/ALERT (bioMérieux) and Bactec (Becton Dickinson) were superior to the manual CFR method described in the general biologics regulations, in rates of detection and time to detection of organisms seeded into mock mononuclear cell products with a variety of background media and antibiotics. In this study, the two automated systems were compared to the CFR method for sterility testing of actual cell therapy products manufactured in our facility.

STUDY DESIGN AND METHODS

Over a 36-month period, in-process and final product samples from all cell therapy products manufactured in our facility were tested for sterility both by the CFR method and by either BacT/ALERT or Bactec. Products were categorized according to collection and processing variables for analysis of results.

RESULTS

For 1617 samples of a broad range of cell therapy products, rates of true-positive tests were comparable for the automated and CFR methods (2.3% vs. 2.1%), but the CFR method had higher rates of false-positive results (7.3% vs. 0.2%). For automated systems, time to detection of organisms was equivalent to, or faster than, the CFR method.

CONCLUSION

Compared to the CFR method, both BacT/ALERT and Bactec are more sensitive, faster in time to detection, less prone to false-positive results, and less labor-intensive. Both of these automated systems are suitable for sterility testing of cell therapy products after site-specific validation has been performed.

Dendritic cell-based immunotherapy

Dendritic cells (DCs) play a crucial role in the induction of antigen-specific T-cell responses, and therefore their use for the active immunotherapy of malignancies has been studied with considerable interest. More than a decade has passed since the publication of the first clinical data of DC-based vaccines, and through this and subsequent studies, a number of important developmental insights have been gleaned. These include the ideal source and type of DCs, the discovery of novel antigens and methods of loading DCs, the role of DC maturation, and the most efficient route of immunization. The generation of immune responses against tumor antigens after DC immunization has been demonstrated, and favorable clinical responses have been reported in some patients; however, it is difficult to pool the results as a whole, and thus the body of data remains inconclusive, in part because of varying DC preparation and vaccination protocols, the use of different forms of antigens, and, most importantly, a lack of rigorous criteria for defining clinical responses. As such, the standardization of clinical and immunologic criteria utilized, as well as DC preparations employed, will allow for the comparison of results across multiple clinical studies and is required in order for future trials to measure the true value and role of this treatment modality. In addition, issues regarding the optimal dose and clinical setting for the application of DC vaccines remain to be resolved, and recent clinical studies have been designed to begin to address these questions.

Production of myeloid dendritic cells (DC) pulsed with tumor-specific idiotype protein for vaccination of patients with multiple myeloma

BACKGROUND

Immunotherapy of cancer with DC vaccines has produced encouraging results in clinical trials. Antigen (Ag)-pulsed DC have elicited CD4+ and CD8+ T-cell immunity and tumor regression in humans. However, there is no standard method of DC production. The DC phenotype, number and Ag-loading process used in these studies have varied, making comparisons between trials difficult.

METHODS

In the present report a reproducible method was developed for the production of a DC-based vaccine. Monocytes were enriched by adhesion from healthy donor apheresis products and cultured with growth factors for maturation into DC. The cells were loaded with the tumor Ag idiotype proteins from patients with multiple myeloma. DC culture and Ag loading were performed in an automated and closed system. The DC product was characterized for phenotype by flow cytometry and for function in Ag uptake and Ag presentation.

RESULTS

These monocyte-derived DC expressed high levels of costimulatory molecules (CD80/86). Ag-pulsed DC functioned to induce allogeneic proliferative lymphocyte responses and Ag-specific cytotoxic T lymphocyte (CTL) responses. The DC viability, phenotype and function were well preserved following prolonged frozen storage. Aliquots from the product of a single DC preparation could be used for sequential vaccinations without batch to batch variability.

DISCUSSION

Ag-pulsed DC can be reproducibly generated for clinical use. These standardized methods are now being employed for a clinical trial to evaluate idiotype-pulsed DC vaccine therapy following non-myeloablative transplant for the treatment of multiple myeloma.

A functional comparison of mature human dendritic cells prepared in fluorinated ethylene-propylene bags or polystyrene flasks

BACKGROUND

Fluorinated ethylene-propylene (FEP) bags have been used instead of polystyrene (PS) flasks for ex vivo clinical-scale production of human dendritic cells (DCs) to facilitate closed-system recovery of these highly adherent cells. To assess the impact of DC culture on this nonadherent surface, the function of DCs generated in FEP and PS was compared.

STUDY DESIGN AND METHODS

Cell yield, phenotype, cytokine production, migration, and antigen-presenting activity were measured in DCs prepared from peripheral blood monocytes in FEP bags or PS flasks with medium supplemented with serum, interleukin (IL)-4, and granulocyte-macrophage-colony-stimulating factor for 5 days to induce DC differentiation and CD40L or poly(I:C) plus interferon-gamma to promote maturation.

RESULTS

DCs cultured in FEP or PS had comparable cell yield, viability, and CD83 and CCR7 expression. DCs generated in FEP, however, produced significantly less IL-12 and IL-10 during maturation, and differences persisted on rechallenge after harvest. FEP-cultured DCs migrated spontaneously or in response to CCR7 ligand more actively than PS-cultured DCs, but this difference was not significant. Mature DCs prepared in FEP and PS were equipotent in stimulating peptide-specific CD8 T-cell expansion in vitro.

CONCLUSION

FEP- and PS-cultured DCs are similar in phenotype and in some functional measures, but FEP markedly reduces DC production of IL-12 and IL-10. This phenomenon presumably reflects intracellular changes linked to the absence of a surface for firm cell adherence. Given the importance of these cytokines in the immune response, these changes could have a significant impact on DC function in vivo.

Generation of dendritic cells for immunotherapy is minimally impaired by granulocytes in the monocyte preparation

The growing number of clinical studies, using monocyte-derived DC therapy, requires protocols where a sufficient number of dendritic cell (DCs) are produced according to current Good Manufacturing Practice guidelines. Therefore, a closed culture system for the generation of DCs is inevitable. One cost-effective way to isolate monocytes directly from leukapheresis material in a closed system is by elutriation with the Elutra cell separation system. In the Elutra, granulocytes co-purify with the monocytes. Therefore, we studied if and to what extent the presence of granulocytes in a monocyte product affects the generation of mature DCs. The presence of up to 16% granulocytes in the monocyte product had no significant effects on the quality of the DCs formed. The presence of higher granulocyte percentages, however, gradually altered DC quality. In this respect, the presence of higher number of granulocytes induced significant lower migratory capacity of the DCs and lower expression levels of CD80, CD40 and CD86. No effects were observed on the DC yield, cytokine production or the stimulatory capacity of the DCs in MLR. In conclusion, the presence of 20-30% granulocytes in a monocyte product has no major influence on the quality of the DCs generated from monocytes. Therefore, the Elutra is a suitable closed system apparatus to separate monocytes from other blood components for the generation of DCs, even from leukapheresis material which contains a high number of granulocytes.

Monocyte enrichment of mononuclear apheresis preparations with a multistep back-flush procedure on a cord blood filter

INTRODUCTION

Monocytes or mononuclear cells have been investigated for the treatment of chronic wounds and spinal cord injuries, as well as serve as a source for dendritic or endothelial cell culture. Because these cells may have clinical benefit yet no rapid and inexpensive closed system for monocyte purification is commercially available, a method was investigated to enrich monocytes from mononuclear apheresis units using a cord blood filter.

METHODS

A 4-step method for monocyte enrichment was developed which involved 1) filtering a mononuclear apheresis unit through a cord blood filter, 2) chasing with medium to remove non-adherent residual cells and plasma, 3) back-flushing under low shear conditions to remove loosely adherent lymphocytes, and 4) back-flushing under high shear conditions to collect a fraction enriched in monocytes. Apheresis units and enriched monocyte preparations were characterized by cell count and differential, filter-isolated preparations were cryopreserved, and thawed preparations were assayed for viability, and phagocytosis. Enriched monocyte preparations were also assayed for inflammatory cytokines secretion and secretion of prostaglandin E2 during short-term culture.

RESULTS

Monocytes were viable, capable of phagocytosis, and enriched using the multistep filter elution technique to represent 42 +/- 13-percent of white cells in the final preparation. Fifty-three-percent of monocytes were recovered in the final preparation, while total cell counts of red cells, platelets, neutrophils and lymphocytes were reduced to 3.0, 3.0, 4.5 and 16-percent, respectively, from levels present in mononuclear apheresis units. Filter enriched monocyte preparations secreted IL-8, IL-6, MCP-1, and MIP-1alpha, during short term culture.

CONCLUSION

The use of a multi-step back flush procedure with a cord blood filter resulted in rapid enrichment of viable and functional monocytes from mononuclear apheresis units with significant reduction of contaminating platelets and red cells.

The large scale generation of dendritic cells for the immunization of patients with non-small cell lung cancer (NSCLC)

In the current study, we generated large numbers of dendritic cells (DCs) from patients with non-small cell lung cancer (NSCLC) for a vaccine trial. The DCs were generated from CD14+ cells obtained by immuno-magnetic bead column separation technique. The CD14+ cells were placed in culture in the presence of granulocyte macrophage colony stimulating factor (GMCSF) and Interleukin 4 (IL-4). At Day 7, apoptotic bodies derived from an allogeneic NSCLC line 1650-TC were added to the cultures at a DC:tumor cell ratio of 1:1. At Day 8, the DCs were harvested, washed and injected intradermally into patients. Using this protocol we have prepared DCs for 16 patients. An average of 9.3 x 10(7) DCs was injected for the priming dose and 8.2 x 10(7) DCs for the boost. Clinical evaluation of the patients and immune assessment are presented in a separate report. The current report provides evidence for the large scale production of functional DCs derived from patients with NSCLC which can be used as vaccines in clinical trials.

Closed system generation of dendritic cells from a single blood volume for clinical application in immunotherapy

Dendritic cells (DC) used for clinical trials should be processed on a large scale conforming to current good manufacturing practice (cGMP) guidelines. The aim of this study was to develop a protocol for clinical grade generation of immature DC in a closed-system. Aphereses were performed with the Cobe Spectra continuous flow cell separator and material was derived from one volume of blood processed. Optimisation of a 3-phase collection autoPBSC technique significantly improved the quality of the initial mononuclear cell (MNC) product. Monocytes were then enriched from MNC by immunomagnetic depletion of CD19+ B cells and CD2+ T cells and partial depletion of NK cells using the Isolex 300I Magnetic cell selector. The quality of the initial mononuclear cell product was found to determine the outcome of monocyte enrichment. Enriched monocytes were cultured in Opticyte gas-permeable containers using CellGro serum-free medium supplemented with GM-CSF and IL-4 to generate immature DC. A seeding concentration of 1 x 10(6) was found optimal in terms of DC phenotype expression, monocyte percentage in culture, and cell viability. The differentiation pattern favours day 7 for harvest of immature DC. DC recovery, viability, as well as phenotype expression after cryopreservation of immature DC was considered in this study. DC were induced to maturation and evaluated in FACS analysis for phenotype expression and proliferation assays. Mature DC were able to generate an allogeneic T-cell response as well as an anti-CMV response as detected by proliferation assays. These data indicate that the described large-scale GMP-compatible system results in the generation of stable DC derived from one volume of blood processed, which are qualitatively and quantitatively sufficient for clinical application in immunotherapeutic protocols.

Innovation meets quality: moving cellular therapies at the National Institutes for Health from bench to bedside

The National Institutes of Health (NIH) Department of Transfusion Medicine has supported clinical investigation in cellular therapies over the past 20 years. This experience, which encompasses product development research, quality system design and product manufacturing for a wide range of early phase clinical trials, provides a firm basis for future work with novel stem cell therapies.

Generation of dendritic cells using cell culture bags--description of a method and review of literature

Anticancer immunotherapy using dendritic cell-based vaccines is a strategy aimed at the induction and maintenance of immune responses against cancer cells. Clinical applications of dendritic cells (DCs) require stringent adherence to Good Manufacturing Practice (GMP) methods and rigorous standardization of DC-based vaccine preparation. Recently, closed systems for DC culture have been developed with a goal to minimize the risk of contamination. Here, we compare the yield, immunophenotype, and functional properties of DCs generated in Lifecell X-Fold culture bags and in plastic wells, both from adherence-selected monocytes, and review the current literature on closed systems for DC generation. We found that both the overall yield and the yield of CD83+ cells in cell culture bags was lower than in the standard culture method. No statistically significant differences were observed in the expression of DC immunophenotypic markers. The capability of DCs cultured in bags and in wells to induce the proliferation of allogeneic mononuclear cells were equivalent. The performance of DCs in mixed lymphocyte reaction correlated significantly (p = 0.005) with the CD83 expression but not with the CD80, CD86, HLA-DR, CD1a, and CD1c expression. We conclude that the immunophenotype and stimulatory properties of DCs cultured in closed cell culture bags are similar to those generated by conventional method using cell culture wells.

OM-197-MP-AC adjuvant properties: the in vitro maturation of normal and leukemic dendritic cells in a serum-free culture model

Dendritic cells (DC) play a pivotal role in linking innate and adaptive immunity. Only mature DC are able to initiate adaptive immune responses by sensitising naive antigen-specific T cells. For clinical immunotherapeutic applications, safe and efficient clinical grade maturation factors of DC are required. Here, we investigated the impact of OM-197-MP-AC (OM-197), a synthetic lipid A analogue pseudo-dipeptide derived from amino acids linked to three fatty acid chains, on the maturation of human monocyte-derived-DC (Mo-DC) and leukemia-derived DC generated in serum-free conditions. After culture with clinical grade GM-CSF and IL-13, OM-197 at 20 microg/ml efficiently induced CD83+ Mo-DC. In comparison to immature Mo-DC that were derived by culture with GM-CSF and IL-13 only, CD40, CD80, CD86, HLA-ABC and HLA-DR molecules were up-regulated upon OM-197 or LPS treatment similarly. In MLR, OM-197-matured Mo-DC were found to be as potent stimulators as LPS-matured Mo-DC for CD4+ T cell proliferation. No significant difference in IFN-gamma quantification was shown between naive CD4+ T cells stimulated by LPS- or OM-197-Mo-DC suggesting that OM-197-Mo-DC can drive naive T cells towards a Th1 response profile that was mainly independent of IL-12 secretion. Similarly, CD8+ T cells could be efficiently polarized into IFN-gamma-secreting-cells by OM-197-Mo-DC, and activated polyclonal pp65-cytomegalovirus-specific CD8+ T lymphocytes. Finally, myeloid leukemic blasts were able to differentiate in vitro into mature functional DC-like cells upon OM-197 treatment in our culture model. Overall, the in vitro effects of clinical grade adjuvant OM-197, showed that it represents a potent inducer of both normal and leukemic-DC maturation, and is likely a good candidate for adjuvant immunotherapy in DC-based vaccines.

Large-scale immunomagnetic selection of CD14+ monocytes to generate dendritic cells for cancer immunotherapy: a phase I study

Dendritic cells (DC) are professional antigen-presenting cells that are widely used in the experimental immunotherapy of cancer. For clinical use GMP-like protocols for the preparation of functionally active dendritic cells (DC) in large numbers and at high purity are needed. However, the currently available protocols have certain disadvantages. In this study we tested the generation and clinical applicability of DC from monocyte preparations produced by immunomagnetic CD14(+) selection using a semiautomated clinical scale immunomagnetic column. Peripheral blood mononuclear cells (PBMC) of 10 patients with metastatic solid tumors were used. With the immunomagnetic separation, we obtained a cell suspension of high CD14(+) purity (median 97.4%, range 94.9-99.0) with a high monocyte yield (median 82.3%, range 63.9-100.0). Differentiation of CD14(+) cells into mature monocyte-derived DC was induced by incubation with IL-4, GM-CSF, TNF-alpha, PGE(2), IL-1 beta, and IL-6. Mature DC showed a high expression of CD83, HLA-DR, and the co-stimulatory molecules CD80 and CD86. Overall CD83(+) yield was 12.1% (range 4.0-29.4). Allogeneic T stimulatory capacity could be demonstrated for all DC preparations in proliferation assays. No significant differences in marker expression or T cell stimulation was detected between fresh DC and those derived from cryopreserved immature DC. Clinical administration of autologous DC by three different parenteral routes was tolerated by all 10 patients without systemic signs of toxicity. Our results indicate that immunomagnetic isolation of CD14(+) monocytes using the CliniMACS device is a suitable method for clinical-scale generation of functional DC under GMP-grade conditions. The selection can be performed in a closed system. Therefore, immunomagnetic CD14(+) selection can be seen as an alternative way to generate DC for clinical tumor vaccination protocols.

Development of a technology platform for large-scale clinical grade production of DC

BACKGROUND

Clinical studies require protocols where a sufficient number of well-characterized highly immunogenic DC are produced according to good manufacturing practice (GMP) guidelines.

METHODS

In the present study, using leukapheresis products from 10 cancer patients, we validated an elutriation technology for large-scale clinical grade production of monocyte-derived DC.

RESULTS

The elutriation method gave a very high purity (mean+/-SD) (86+/-5.3%) and recovery (66+/-10.4%) of monocytes. Specifically for the two monocyte-rich fractions (3 and 4,) the recovery was 42+/-13% of viable cells that could be further differentiated into immature DC in hydrophobic culture bags using GM-CSF and IL-4. The immature DC exhibited<1% CD83+ expression and >98% phagocytic activity. Maturation with TNF-alpha or poly I:C resulted in DC with expression of CD80+, CD86+ and HLA-DR+ (>99%) and CD83+ (80+/-11.9%), as well as producing IL-12p70 and lacking phagocytic activity (<5%). This cell product can be cryopreserved with cell viability >85% and cell recovery >80% after thawing.

DISCUSSION

The elutriation procedure, when optimized and if the monocyte content of the starting material exceeds 5%, does not require further selection or depletion using affinity approaches.

A protocol for generation of clinical grade mRNA-transfected monocyte-derived dendritic cells for cancer vaccines

With the aim of producing large quantities of mRNA-transfected monocyte-derived dendritic cells (DCs) to be used as cancer vaccines, a new clinical grade procedure has been developed. Peripheral blood mononuclear cells (PBMCs) obtained by leukapheresis were enriched for monocytes by immunomagnetic depletion of CD19+ B cells and CD2+ T cells employing the ISOLEX 300i device. After 5 days of culture of enriched monocytes in gas permeable Teflon bags, using serum-free medium supplemented with granulocyte/macrophage-colony stimulating factor and interleukin-4 (IL-4), immature DCs were generated. Following transfection with mRNA from three human prostate cancer cell lines (DU145, LNCaP and PC-3), employing a newly developed square wave electroporation procedure, the immature DCs were immediately transferred to Teflon bags and matured for 48 h, using serum-free medium supplemented with IL-1alpha, IL-6, tumour necrosis factor-alpha and PGE2. The electroporation procedure efficiently transferred mRNA into the DCs with minor effect on the viability of the cells. The generated matured transfected DCs show high expression of the antigens CD83, CD80, CD86 and human leucocyte antigen-DR. Freezing and thawing of the transfected matured DCs had minor effect on cell viability and the phenotype. From 4 x 109 PBMCs, about 1 x 108 transfected matured DCs are produced. The thawed transfected DCs were able to elicit primary T-cell responses in vitro against antigens encoded by the prostate cancer mRNA as shown by enzyme-linked immunospot assay using mock-transfected DCs as control. Based on these results, clinical trials in cancer patients have been initiated.

Dendritic Cell Culture: A Simple Closed Culture System Using Ficoll, Monocytes, and a Table-Top Centrifuge

Dendritic cells (DCs) are potent antigen-presenting cells involved in the induction of T cell-mediated immune responses and as such have emerged as important candidates for cellular-based therapies. Critical to safe clinical use is the easy manipulation of DCs and their precursors in a closed system. We have developed a serum-free, closed culture system applying a simple wash-Ficoll centrifugation method to reduce platelet and red blood cell (RBC) contamination. This procedure optimized adherence of monocytes (44 +/- 10.9% recovery, >85% expressed CD14(+)/CD163(+)) for the generation of DCs from mononuclear cell (MNC) apheresis units. Most RBCs and up to 98% of platelets were removed. Following density sedimentation, cell viability remained high (98 +/- 2%) with only minimal loss of monocytes (3 +/- 3%). Importantly, Ficoll-treated monocytes retained their ability to differentiate to mature DCs demonstrated by morphology, phenotype (MHC class II(+), CD1a(+), CD80(+), CD86(+), and CD83(+)), ability to stimulate mixed lymphocyte responses (MLR), present antigen, and produce interleukin-12 (IL-12). Nonadherent CD3(+) (80 +/- 4%) were also isolated for functional assays. Ficoll can be easily incorporated into a simple adherence-based closed system for collection of lymphocytes and adherent monocytes for DC culture. The procedure is relatively fast (effective working time 5-6 h), does not impair monocyte function or induce substantial cell activation, and can be performed economically using equipment found in a typical blood banking environment.

Comparison of two apheresis systems for the collection of CD14+ cells intended to be used in dendritic cell culture

BACKGROUND

Monocytes collected by leukapheresis are increasingly used for dendritic cell (DC) culture in cell factories suitable for DC vaccination in cancer.

STUDY DESIGN AND METHODS

Using modified MNC programs on two apheresis systems (Cobe Spectra and Fresenius AS.TEC204), leukapheresis components collected from 84 patients with metastatic malignant melanoma and from 31 healthy male donors were investigated. MNCs, monocytes, RBCs, and platelets (PLTs) in donors and components were analyzed by cell counters, WBC differential counts, and flow cytometry.

RESULTS

In 5-L collections, Astec showed better results regarding monocyte collection rates (11.0 vs. 7.4 x 10(6)/min, p = 0.04) and efficiencies (collection efficiency, 51.9 vs. 31.9%; p < 0.001). Both devices resulted in monocyte yields at an average of 1 x 10(9) (donors) and 2.5 x 10(9) (patients), whereas Astec components contained high residual RBCs. Compared to components with low residual PLTs, high PLT concentration resulted in higher monocyte loss (48 vs. 20%, p < 0.0001) before DC culture.

CONCLUSION

The Astec is more efficient in 5-L MNC collections compared to the Spectra. Components with high residual PLTs result in high MNC loss by purification procedures. Thus, optimizing MNC programs is essential to obtain components with high MNC yields and low residual cells as prerequisite for high DC yields.

Efficacy of dendritic cell generation for clinical use: recovery and purity of monocytes and mature dendritic cells after immunomagnetic sorting or adherence selection of CD14+ starting populations

Immunotherapy with monocyte-derived dendritic cells (Mo-DCs) is applied to an increasing number of patients requiring large-scale production of clinical-grade dendritic cells with standardized Mo-DC generation protocols. In many countries, e.g., in Germany, Mo-DCs are legally considered medicinal products, which must be produced under Good Manufacturing Practice (GMP) conditions by an institution holding an official production license. Plastic adherence, immunomagnetic selection of CD14(+) monocytes and depletion of CD2(+) and CD19(+) cells are used to enrich monocytes for Mo-DC culture. The latter two have received approval of the European Union (CE). However, enrichment by plastic adherence is well-established and commonly used for clinical and research Mo-DC applications. The various plastic materials, nevertheless, have not been officially approved for monocyte selection for clinical use. In the present study therefore, we compared three methods for enrichment of CD14(+) monocytes with regard to efficiency of enrichment, yield of monocyte-derived functional mature dendritic cells, cost effectiveness, and handling. We demonstrate that CD14 selection and CD2 and CD19 depletion yield similar results regarding purity of mature DEs MoDCs (97-99% vs. 64-97%) and their immunostimulatory capacity. However, cell preparations cultured after CD14 selection possessed 91% to 97% CD14(+) cells, whereas CD2-/and DC19-depleted preparations contained only 8% to 57% CD14(+) cells. Thus, positive selection requires smaller culture volumes to generate equal numbers of Mo-DCs. Both methods gave better results than plastic adherence. In conclusion, of the techniques examined, CD14 selection of monocytes gave the best results regarding reproducibility, yield, and purity of the resulting monocytes and mature Mo-DCs.

Large-scale monocyte enrichment coupled with a closed culture system for the generation of human dendritic cells

Conventional methods for generating monocyte-derived dendritic cells (DC) for clinical trials utilize the property of plastic adherence to select monocytes from leukapheresis samples. This method is labor-intensive and has the potential for contamination at various steps. We evaluated a large-scale monocyte enrichment procedure using a cell selector (Isolex 300i(R)) followed by culture in a sterile bag system (Stericell(R)) for generation of DC. DC generated in tissue culture flasks after monocyte selection by plastic adherence were compared to those generated in Stericell(R) bags after monocyte enrichment by negative selection with the Isolex(R) 300i. DC were matured with lipopolysaccharide and pulsed with a peptide derived from the melanoma antigen gp100. Peptide-pulsed DC cultured by the two techniques were evaluated for phenotype, viability, ability to induce allogeneic and peptide-specific autologous proliferative responses as well as peptide-specific cytotoxic T-cell responses. The mean monocyte yield from leukapheresis collections was 17+/-2.4%, which increased to 52+/-11% after Isolex(R) selection. The DC yield of plated mononuclear cells from flasks or bags was 2.7+/-0.96% and 4.84+/-2.65%, respectively. DC cultured by both methods expressed high levels of CD86, CD80, CD40, CD83, CD44, CD11c and CD58, and was comparable in their ability to induce allogeneic and peptide-specific autologous proliferative responses as well as gp100 peptide-specific cytotoxic T-cell responses. These results indicate that potent monocyte-derived DC can be generated in a closed culture bag system after monocyte enrichment by immunomagnetic negative selection. Due to the closed nature of the enrichment and culture systems, the potential for contamination is minimized. This protocol is well suited for culturing large numbers of DC for clinical immunotherapy trials.