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

Counter-flow elutriation of clinical peripheral blood mononuclear cell concentrates for the production of dendritic and T cell therapies

Introduction

Peripheral blood mononuclear cells (PBMC) concentrates collected by apheresis are frequently used as starting material for cellular therapies, but the cell of interest must often be isolated prior to initiating manufacturing.

Study design and methods

The results of enriching 59 clinical PBMC concentrates for monocytes or lymphocytes from patients with solid tumors or multiple myeloma using a commercial closed system semi-automated counter-flow elutriation instrument (Elutra, Terumo BCT) were evaluated for quality and consistency. Elutriated monocytes (n = 35) were used to manufacture autologous dendritic cells and elutriated lymphocytes (n = 24) were used manufacture autologous T cell therapies. Elutriated monocytes with >10% neutrophils were subjected to density gradient sedimentation to reduce neutrophil contamination and elutriated lymphocytes to RBC lysis.

Results

Elutriation separated the PBMC concentrates into 5 fractions. Almost all of the lymphocytes, platelets and red cells were found in fractions 1 and 2; in contrast, most of the monocytes, 88.6 ± 43.0%, and neutrophils, 74.8 ± 64.3%, were in fraction 5. In addition, elutriation of 6 PBMCs resulted in relatively large quantities of monocytes in fractions 1 or 2. These 6 PBMCs contained greater quantities of monocytes than the other 53 PBMCs. Among fraction 5 isolates 38 of 59 contained >10% neutrophils. High neutrophil content of fraction 5 was associated with greater quantities of neutrophils in the PBMC concentrate. Following density gradient separation the neutrophil counts fell to 3.6 ± 3.4% (all products contained <10% neutrophils). Following red cell lysis of the elutriated lymphocyte fraction the lymphocyte recovery was 86.7 ± 24.0% and 34.3 ± 37.4% of red blood cells remained.

Conclusions

Elutriation was consistent and effective for isolating monocytes and lymphocytes from PBMC concentrates for manufacturing clinical cell therapies, but further processing is often required.

Purification of circulating plasmacytoid dendritic cells using counterflow centrifugal elutriation and immunomagnetic beads

BACKGROUND AIMS

Plasmacytoid dendritic cells (pDC) are a dendritic cell (DC) subset specialized in the production of high amounts of interferon (IFN) type I (IFN-α, -β) in response to viruses. They can be purified from peripheral blood mononuclear cells (PBMC), usually using magnetic bead sorting.

METHODS

In this study, we set up a counterflow centrifugal elutriation (CCE) procedure to enrich pDC from PBMC. We first analyzed each CCE fraction for the presence of pDC using CD123 and BDCA-2 as markers. We then purified pDC using CCE and magnetic beads and verified that their functions were not affected by this procedure.

RESULTS

pDC were sorted by CCE into intermediate fractions between those containing lymphocytes and monocytes. The pDC frequency in these intermediate fractions was 3-fold that in PBMC. Using negative-magnetic bead sorting, starting with the same number of cells and beads, we obtained more than twice as many pDC from intermediate fractions as from PBMC. The phenotypes and IFN-α production capacities of sorted pDC from PBMC and from intermediate fractions were similar, both immediately after sorting and after stimulation with CpG-A oligodeoxynucleotides. In addition, we showed that intermediate fractions could be cryopreserved and that magnetic bead sorting could be performed with the same efficiency after thawing.

CONCLUSIONS

Altogether, our results show that CCE can be used to enrich lymphocytes, monocytes and pDC from the same donor, without magnetic beads on their surface. Our method should be useful for the purification of these cells for experimental research and may also be adaptable for clinical use in immunotherapy.

Crosstalk between Toll like receptors and C5a receptor in human monocyte derived DCs suppress inflammatory cytokine production

The complement anaphylatoxin, C5a has been implicated in regulation of adaptive immune responses through modulation of APC function as shown mainly in studies in mice. C5a was shown to enhance cytokine production in immature DCs, but the effect of C5a on DC function during DC activation has not been elucidated in human. In this study we investigated the effect of C5a on human monocyte derived DCs when simultaneously stimulated with TLR ligands. While C5a indeed enhanced cytokine production of immature DCs, the addition of C5a inhibited production of IL-12, IL-23 and TNFα induced by various TLR ligands such as LPS, R848 and Pam(3)CSK(4). The inhibitory effect of C5a on LPS induced IL-6 production was less pronounced and LPS induced IL-10 was not affected at all. This indicates that C5aR signaling has a differential effect on human DC differentiation depending on the crosstalk with other receptors. Furthermore we found that C5a affects the LPS induced cytokines in a small time frame, and requires almost concurrent signaling of C5a receptor and TLR4. These data emphasize the complexity of DC regulation by anaphylatoxins. While complement activation may provide proinflammatory signals to immature DCs in the absence of pathogens, the same products may serve to downmodulate or deviate immune responses upon combat against infections. These context depending effects of anaphylatoxins on immune responses may have important implications for the emerging use of complement inhibitors in clinical practice.

IL-10-generated tolerogenic dendritic cells are optimal for functional regulatory T cell induction--a comparative study of human clinical-applicable DC

Tolerogenic dendritic cells (tDC) are a promising tool for specific cellular therapy to induce immunological tolerance in transplantation and autoimmunity. To date, most described tDC methods have not been converted into clinically applicable protocols and systematic comparison of required functional characteristics, i.e. migration and functional regulatory T cell (Treg) induction, is lacking. We compare clinical-grade tDC generated with vitamin D(3), IL-10, dexamethasone, TGFβ or rapamycin. For good migratory capacity and a stable phenotype, additional maturation of tDC was required. Maturation with a cocktail of TNFα, IL-1β and PGE(2) induced optimal migration. Importantly, all tDC showed a stable phenotype under pro-inflammatory conditions. Especially IL-10 DC showed most powerful tolerogenic characteristics with high IL-10 production and low T cell activation. Moreover, in a functional suppression assay only IL-10 DC induced Treg that strongly suppressed T cell reactivity. Thus, clinical-grade IL-10 DC show functional characteristics that make them best suited for tolerance-inducing therapies.

Generation of functionally mature dendritic cells from elutriated monocytes using polyinosinic : polycytidylic acid and soluble CD40 ligand for clinical application

Despite the increasing use of dendritic cell (DC) vaccination in clinical trials, optimal conditions for the generation of functionally mature DCs remain to be established. The current standard DC maturation protocol for clinical trials has been used as an inflammatory cytokine cocktail [tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6 and prostaglandin E(2)], but this cocktail induced insufficient maturation of DCs derived from elutriated monocytes when cultured in X-VIVO 15. The aim of this study was to define effective combinations of stimulators for generating functionally mature DCs from elutriated monocytes under current good manufacturing practice conditions. We compared the functional capacity of DCs in response to all possible pairwise combinations of four different classes of stimuli: TNF-alpha, peptidoglycan, polyinosinic : polycytidylic acid [poly(I:C)] and soluble CD40 ligand (CD40L). Maturation status of DCs stimulated with combination of four stimuli was similar to that of the cytokine cocktail as assessed by the cell surface phenotype. However, only the combination of poly(I:C) + CD40L induced complete functional activation of the whole DC population, assessing IL-12p70 production, allostimulatory activity, migratory response to CCL19 and T helper 1-polarizing capacity. Thus, the protocol based on the combination of poly(I:C) and CD40L is more effective for the induction of clinical-grade DCs from elutriated monocytes than the standard cytokine cocktail.

Isolation of monocytes from leukapheretic products for large-scale GMP-grade generation of cytomegalovirus-specific T-cell lines by means of an automated elutriation device

BACKGROUND

Dendritic cells (DC) act as antigen-presenting cells in immune response-mediated mechanisms against malignant cells and/or viral or fungal pathogens. CD14+ monocytes have been so far isolated by techniques of plastic adherence or by using immunomagnetic methods. Here the effectiveness of a commercially available cell separation system (Elutra, Gambro BCT) in the separation of monocytes and the large-scale production of cytomegalovirus (CMV)-specific T-cell lines were investigated.

STUDY DESIGN AND METHODS

Six mononuclear cell (MNC) collections were processed with the Elutra system. Monocyte-enriched fraction was differentiated into DCs by addition of granulocyte-macrophage-colony-stimulating factor and interleukin (IL)-4. After 6 days of culture, DCs were matured in the presence of interferon (IFN)-gamma, IFN-alpha, IL-1beta, tumor necrosis factor-alpha, and poly(I:C) and pulsed with a pool of 48 MHC Class I and II-binding CMV peptides. Lymphocytes were then stimulated with mature autologous CMV peptide-pulsed DCs.

RESULTS

After elutriation, the mean monocyte yield was 0.89 x 10(9) +/- 0.65 x 10(9), with a 51.0 +/- 31.6 percent recovery and a 51.1 +/- 35.4 percent purity. A significant correlation was observed when basal monocyte content was related to the postelutriation recovery (p < 0.0116). More than 60 percent of plated monocytes were differentiated into DCs, which after pulsing with CMV peptides, were able to stimulate a robust enrichment in CMV antigen-specific T cells in all tested samples (mean percentage of pentamer-positive CD8+ cells, 35% compared to the initial 2%).

CONCLUSION

Our findings might be helpful for an appropriate MNC collection, to maximize the efficiency of the elutriation system and subsequently obtain an optimal monocyte-enriched yield for further DC generation and T-cell stimulation.

Comparative evaluation of techniques for the manufacturing of dendritic cell-based cancer vaccines

Manufacturing procedures for cellular therapies are continuously improved with particular emphasis on product safety. We previously developed a dendritic cell (DC) cancer vaccine technology platform that uses clinical grade lipopolysaccharide (LPS) and interferon (IFN)-y for the maturation of monocyte derived DCs. DCs are frozen after 6 hrs exposure at a semi-mature stage (smDCs) retaining the capacity to secret interleukin (IL)-12 and thus support cytolytic T-cell responses, which is lost at full maturation. We compared closed systems for monocyte enrichment from leucocyte apheresis products from healthy individuals using plastic adherence, CD14 selection, or CD2/19 depletion with magnetic beads, or counter flow centrifugation (elutriation) using a clinical grade in comparison to a research grade culture medium for the following DC generation. We found that elutriation was superior compared to the other methods showing 36 ± 4% recovery, which was approximately 5-fold higher as the most frequently used adherence protocol (8 ± 1%), and a very good purity (92 ± 5%) of smDCs. Immune phenotype and IL-12 secretion (adherence: 1.4 ± 0.4; selection: 20 ± 0.6; depletion: 1 ±0.5; elutriation: 3.6 ± 1.5 ng/ml) as well as the potency of all DCs to stimulate T cells in an allogeneic mixed leucocyte reaction did not show statistically significant differences. Research grade and clinical grade DC culture media were equally potent and freezing did not impair the functions of smDCs. Finally, we assessed the functional capacity of DC cancer vaccines manufactured for three patients using this optimized procedure thereby demonstrating the feasibility of manufacturing DC cancer vaccines that secret IL-12 (9.4 ± 6.4 ng/ml). We conclude that significant steps were taken here towards clinical grade DC cancer vaccine manufacturing.

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.