The most commonly used method for generating large numbers of autologous dendritic cells (DCs) for use in tumor immunotherapy is described. The method uses IL-4 and GM-CSF to differentiate DCs from monocytes. The immature DCs are stimulated to mature and then loaded with antigens before they are injected back into the patient.
While clinical studies have established that antigen-loaded DC vaccines are safe and promising therapy for tumors 1, their clinical efficacy remains to be established. The method described below, prepared in accordance with Good Manufacturing Process (GMP) guidelines, is an optimization of the most common ex vivo preparation method for generating large numbers of DCs for clinical studies 2.
Our method utilizes the synthetic TLR 3 agonist Polyinosinic-Polycytidylic Acid-poly-L-lysine Carboxymethylcellulose (Poly-ICLC) to stimulate the DCs. Our previous study established that Poly-ICLC is the most potent individual maturation stimulus for human DCs as assessed by an upregulation of CD83 and CD86, induction of interleukin-12 (IL-12), tumor necrosis factor (TNF), interferon gamma-induced protein 10 (IP-10), interleukmin 1 (IL-1), and type I interferons (IFN), and minimal interleukin 10 (IL-10) production.
DCs are differentiated from frozen peripheral blood mononuclear cells (PBMCs) obtained by leukapheresis. PBMCs are isolated by Ficoll gradient centrifugation and frozen in aliquots. On Day 1, PBMCs are thawed and plated onto tissue culture flasks to select for monocytes which adhere to the plastic surface after 1-2 hr incubation at 37 °C in the tissue culture incubator. After incubation, the lymphocytes are washed off and the adherent monocytes are cultured for 5 days in the presence of interleukin-4 (IL-4) and granulocyte macrophage-colony stimulating factor (GM-CSF) to differentiate to immature DCs. On Day 6, immature DCs are pulsed with the keyhole limpet hemocyanin (KLH) protein which serves as a control for the quality of the vaccine and may boost the immunogenicity of the vaccine 3. The DCs are stimulated to mature, loaded with peptide antigens, and incubated overnight. On Day 7, the cells are washed, and frozen in 1 ml aliquots containing 4 – 20 x 106 cells using a controlled-rate freezer. Lot release testing for the batches of DCs is performed and must meet minimum specifications before they are injected into patients.
1. Isolation and Cryopreservation of PBMCs 4
2. Day 0: Differentiation of Dendritic Cells from Monocytes
3. Day 2: Feeding of Dendritic Cells with IL-4 and GM-CSF
4. Day 5: Harvesting of Immature Dendritic Cells
5. Day 6: Maturation and Antigen Loading of Dendritic Cells
6. Day 7: Cryopreservation of Dendritic Cells
7. Lot Release Testing
Between 10 – 20% of starting PBMCs differentiate into DCs at the end of the culture period. Mature DCs are CD11c+, CD14-, CD83+, CD40+, and CCR7+ (Figure 1). They express high levels of MHC class I and II molecules and the costimulatory molecules CD80 and CD86. Poly-ICLC also induced lower levels of PDL-1 as compared to other TLR agonists 14. Additionally, these Poly-IC-matured DCs secrete large amounts of IL-12 (Figure 2 and 15,16) and induce the proliferation of allogeneic T cells (Figure 3).
Figure 1. Representative phenotype of fully differentiated DCs matured with Poly-IC. All the DCs were gated on the forward- and side-scatter plot. DCs were identified as CD11c+ and CD14-. Maturation of DCs in response to Poly-ICLC (bold line) was evaluated based on the expression of CD83, CD40, and CCR7 and compared to unstimulated DCs (gray shade). Click here to view larger figure.
Figure 2. DCs matured with Poly-IC produce high levels of cytokines. Supernatants from DCs differentiated from 3 healthy donors were collected after overnight maturation of DCs with Poly-IC. Cytokines produced were measured by Cytokine Bead Array (CBA) Human Inflammatory Cytokines Kit (BD Biosciences) which measures IL-12p70, TNF, IL-10, IL-6, IL-1β, and IL-8.
Figure 3. DCs matured with Poly-ICLC induce the proliferation of allogeneic T cells. Poly-ICLC-matured DCs from healthy donors were incubated 1:10 with Carboxyfluorescein Diacetate Succinimidyl Ester (CFSE)-labeled allogeneic T cells. After 6 days, proliferation (A) was evaluated by flow cytometry by gating on the CD3+ T cell population. X-axis shows the dilution of CFSE, as a measurement of proliferation, in the various co-culture conditions: T cells alone, unstimulated DC, Poly-ICLC stimulated DC, and phytohaemagglutinin (PHA)-stimulated T cells. Cytokine secretion (B) during the proliferation was evaluated from the supernatants in the cultures using the BD CBA Human Th1/Th2 Cytokine Kit II (BD Biosciences) which measures IFNγ, TNF, IL-10, IL-6, IL-4, and IL-2. Only IFNγ is shown as the other cytokines were not detected to measureable levels in the assay. Click here to view larger figure.
Test | Method | 基準 |
Viability | Guava Personal Cell Analysis with ViaCount Reagent | >70% |
Identity | Flow Cytometry – % CD11c+ cells | > 50% |
Flow Cytometry – % CD11c+CD14+ cells | < 30% | |
Flow Cytometry – % CD11c+CD14-CD83+ cells | > 50% | |
Sterility | Bacterial and Fungal Cultures | Negative |
Mycoplasma: Direct Cell Culture | Negative | |
Endotoxin | Kinetic Chromogenic LAL Assay | < 50 EU/ml |
Function | Mixed Lymphocyte Reaction | Report Results |
Table 1. Lot Release Criteria.
Phase I and II clinical trials of monocyte-derived DCs have shown that they induce immune responses in patients however clinical success has been limited 1. This may be partly due to the lack of consensus on how to generate the optimal DCs for tumor immunotherapeutic use. Although there are numerous ways to generate clinical-grade DCs, these methods vary in terms of the use of cytokines used to differentiate the monocytes, stimuli used to induce maturation, and methods of antigen loading. The formula for generating the optimal DCs still remains to be defined 2.
Recent in vitro studies have shown that the DCs matured with a cocktail of proinflammatory cytokines 10 which has been used in the majority of clinical trials, in particular the presence of PGE2, may induce the differentiation of regulatory T cells and Th2 responses 17, express IDO 18, and are deficient in IL-12p70 production 19. These effects significantly undermine the vaccine’s ability to induce immune responses and therefore support the need to evaluate alternative methods of maturing DCs in order to optimize their effects in vivo.
The use of TLR agonists, in particular the TLR 3 agonist Poly-IC, to mature the DCs may improve the clinical efficacy of DCs. In vitro studies have shown that Poly-IC-matured DCs retained stable high expression of MHC molecules and CD83 and costimulatory molecules CD40, CD80, and CD86 14,15,20. Additionally, Poly-IC-matured DCs produced high levels of IL-12 14,16,20, an important cytokine for the generation of anti-tumor response 21, as well as other proinflammatory cytokines such as TNF-α, IL-6, IL-1β, IP-10, and type I IFNs 14. More importantly, as has been shown in murine tumor models, DCs pulsed with Human Papilloma Virus (HPV) antigens and matured with Poly-IC-primed cytotoxic T cell responses were capable of eradicating established HPV16-expressing tumors 22. As the maturation status of DCs and the presence of IL-12 appear to correlate with efficacy in clinical trials 23,24, the use of Poly-IC to mature DCs may be an important step towards attaining the goal of clinical success.
The authors have nothing to disclose.
The authors would like to thank Andres Salazar (Oncovir, Inc.) for the gift of the Poly-ICLC.
Reagent/Supplies/Equipment | Manufacturer | Catalog No. | |
RPMI-1640 medium with L-glutamine | BioWhittaker | 12-702F | |
1M HEPES buffered saline | BioWhittaker | 17-737E | |
Phosphate buffered saline (PBS) | BioWhittaker | 17-516F | |
Human albumin, 25% solution USP | Aventis Behring | ||
Ficoll-Hypaque PREMIUM | GE Healthcare | 17-5442-03 | |
Human AB serum | Valley Biomedical | HP1022 | |
Sterile saline USP | Hospira | ||
CryoMACS DMSO | Miltenyi Biotec | 170-076-303 | |
Leukine GM-CSF, 0.5 mg/ml | Berlex | A02266 | |
MACS GMP IL-4 | Miltenyi Biotec | 170-076-101 | |
Hiltonol, Poly-ICLC, 2 mg/ml | Oncovir | NA | |
VACMUNE KLH | Biosyn | ||
225 sq cm EasyFlasks | Nalgene Nunc | 159934 | |
Falcon 6-well tissue culture plates | Becton Dickinson | 353046 | |
1.8 ml CryoTube vials | Nalgene Nunc | 377267 | |
Controlled Rate Freezer | Thermo | CryoMed |