Cryopreservation of adenovirus-transfected dendritic cells (DCs) for clinical use

Freezing of dendritic cells with trehalose as an additive in the conventional freezing medium results in improved recovery after cryopreservation

BACKGROUND

Dendritic cell (DC) vaccination involves administration of multiple doses. Cryopreservation of tumor antigen-pulsed DCs can provide a ready to use vaccine source and eliminate the need of frequent withdrawal of the patient's blood for vaccine preparation. The aim of this study was to assess the effect of addition of trehalose in the freezing medium on the recovery of DCs after cryopreservation.

STUDY DESIGN AND METHODS

DCs were generated from mononuclear cells from apheresis samples of healthy donors. For long-term storage of 6 months, cells were frozen with a rate-controlled programmable freezer and stored in liquid nitrogen. For short-term storage of 1 month, cells were frozen and stored at -80°C. DCs frozen with Iscove's Modified Dulbecco's Medium + 10% dimethyl sulfoxide + 20% fetal bovine serum served as the control group, while the test group was additionally supplemented with 50 μg/mL of trehalose. After revival of control and test DCs, they were assessed for viability, morphology, phenotype, and functions.

RESULTS

The addition of trehalose to the conventional freezing medium helped to preserve the viability and functionality of DCs better than dimethyl sulfoxide alone in both long- and short-term cryopreservation. Trehalose also protected the mitochondrial membrane potential and cytoskeleton integrity of DCs, which are necessary for their functionality. Mediators of the intrinsic apoptotic pathway like Caspase-9 and Bim-1 were found to be low in the test.

CONCLUSION

Supplementation of conventional freezing medium with trehalose results in better quality of DCs revived after cryopreservation. This finding could help improve DC vaccine preparation for cancer immunotherapy.

Cryopreservation of Human Adipose-Derived Stem Cells for Use in Ex Vivo Regional Gene Therapy for Bone Repair

The development of an ex vivo regional gene therapy clinical pathway using adipose-derived stem cells (ASCs) may require cryopreservation for cell culture, storage, and transport prior to clinical use. ASCs isolated from five donors were transduced with a lentiviral vector containing BMP-2. Three groups were assessed: transduction without cell freezing (group 1), freezing of cells for 3 weeks followed by transduction (group 2), and cell transduction prior to freezing (group 3). Nontransduced cells were used as a control. The cluster of differentiation (CD) marker profiles, cell number, BMP-2 production, and osteogenic potential were measured. The CD marker profile (CD44, CD73, CD90, and CD105) was unchanged after cryopreservation. Cell number was equivalent among cryopreservation protocols in transduced and nontransduced cells. There was a trend toward decreased BMP-2 production in group 3 compared to groups 1 and 2. Osteogenic potential based on Alizarin red concentration was higher in group 2 compared to group 3, with no difference compared to group 1. Freezing ASCs prior to transduction with a lentiviral vector containing BMP-2 has no detrimental effect on cell number, BMP-2 production, osteogenic potential, or immunophenotype. Transduction prior to freezing, however, may limit the BMP-2 production and potential osteogenic differentiation of the ASCs.

Immunomodulatory Effects of 1,25-Dihydroxyvitamin D3 on Dendritic Cells Promote Induction of T Cell Hyporesponsiveness to Myelin-Derived Antigens

While emerging evidence indicates that dendritic cells (DC) play a central role in the pathogenesis of multiple sclerosis (MS), their modulation with immunoregulatory agents provides prospect as disease-modifying therapy. Our observations reveal that 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) treatment of monocyte-derived DC results in a semimature phenotype and anti-inflammatory cytokine profile as compared to conventional DC, in both healthy controls and MS patients. Importantly, 1,25(OH)₂D₃-treated DC induce T cell hyporesponsiveness, as demonstrated in an allogeneic mixed leukocyte reaction. Next, following a freeze-thaw cycle, 1,25(OH)₂D₃-treated immature DC could be recovered with a 78% yield and 75% viability. Cryopreservation did not affect the expression of membrane markers by 1,25(OH)₂D₃-treated DC nor their capacity to induce T cell hyporesponsiveness. In addition, the T cell hyporesponsiveness induced by 1,25(OH)₂D₃-treated DC is antigen-specific and robust since T cells retain their capacity to respond to an unrelated antigen and do not reactivate upon rechallenge with fully mature conventional DC, respectively. These observations underline the clinical potential of tolerogenic DC (tolDC) to correct the immunological imbalance in MS. Furthermore, the feasibility to cryopreserve highly potent tolDC will, ultimately, contribute to the large-scale production and the widely applicable use of tolDC.

The double-edge role of B cells in mediating antitumor T-cell immunity: Pharmacological strategies for cancer immunotherapy

Emerging evidence reveals the controversial role of B cells in antitumor immunity, but the underlying mechanisms have to be explored. Three latest articles published in the issue 521 of Nature in 2015 reconfirmed the puzzling topic and put forward some explanations of how B cells regulate antitumor T-cell responses both positively and negatively. This paper attempts to demonstrate that different B-cell subpopulations have distinct immunological properties and that they are involved in either antitumor responses or immunosuppression. Recent studies supporting the positive and negative roles of B cells in tumor development were summarized comprehensively. Several specific B-cell subpopulations, such as IgG(+), IgA(+), IL-10(+), and regulatory B cells, were described in detail. The mechanisms underlying the controversial B-cell effects were mainly attributed to different B-cell subpopulations, different B-cell-derived cytokines, direct B cell-T cell interaction, different cancer categories, and different malignant stages, and the immunological interaction between B cells and T cells is mediated by dendritic cells. Promising B-cell-based antitumor strategies were proposed and novel B-cell regulators were summarized to present interesting therapeutic targets. Future investigations are needed to make sure that B-cell-based pharmacological strategies benefit cancer immunotherapy substantially.

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.

Adenovirus expressing β2-microglobulin recovers HLA class I expression and antitumor immunity by increasing T-cell recognition

Optimal tumor cell surface expression of human leukocyte antigen (HLA) class I molecules is essential for the presentation of tumor-associated peptides to T-lymphocytes. However, a hallmark of many types of tumor is the loss or downregulation of HLA class I expression associated with ineffective tumor antigen presentation to T cells. Frequently, HLA loss can be caused by structural alterations in genes coding for HLA class I complex, including the light chain of the complex, β2-microglobulin (β2m). Its best-characterized function is to interact with HLA heavy chain and stabilize the complex leading to a formation of antigen-binding cleft recognized by T-cell receptor on CD8+ T cells. Our previous study demonstrated that alterations in the β2m gene are frequently associated with cancer immune escape leading to metastatic progression and resistance to immunotherapy. These types of defects require genetic transfer strategies to recover normal expression of HLA genes. Here we characterize a replication-deficient adenoviral vector carrying human β2m gene, which is efficient in recovering proper tumor cell surface HLA class I expression in β2m-negative tumor cells without compromising the antigen presentation machinery. Tumor cells transduced with β2m induced strong activation of T cells in a peptide-specific HLA-restricted manner. Gene therapy using recombinant adenoviral vectors encoding HLA genes increases tumor antigen presentation and represents a powerful tool for modulation of tumor cell immunogenicity by restoration of missing or altered HLA genes. It should be considered as part of cancer treatment in combination with immunotherapy.