Production of lentiviral vectors with enhanced efficiency to target dendritic cells by attenuating mannosidase activity of mammalian cells

Inhibition of Dectin-1 on Dendritic Cells Prevents Maturation and Prolongs Murine Islet Allograft Survival

Introduction

The ability of dendritic cells (DCs) to initiate an immune response or induce immune tolerance depends on their maturation status. Dendritic-cell-associated C-type lectin 1 (Dectin-1) plays a key role in the differentiation, activation, and maturation of DCs. Therefore, we hypothesized that inhibition of Dectin-1 could prevent DC maturation and induce immune tolerance of transplanted organs.

Methods

DCs were transduced with a recombinant lentiviral vector to inhibit Dectin-1 and then were injected into a murine recipient before islet transplantation. C57BL/6 mice (H-2b) were treated with lentiviral vector-Dectin-1-RNAi-DC (DC-Dectin-1-RNAi group), lentiviral vector-GFP DCs (DC-GFP group), and PBS (control group). Pancreatic islet transplantation was performed and graft survival was recorded. The proportions of regulatory T cells, Th1 cells, and Th17 cells in the spleen and draining lymph nodes, and serum levels of interleukin (IL)-10, IL-17, and interferon (INF)-γ were measured.

Results

The inhibition of Dectin-1 resulted in low expression of MHC-II and costimulatory molecules in DCs. Murine recipients treated with DC-Dectin-1-RNAi had longer islet allograft survival time, a reduction in the levels of Th1 and Th17 cells and secreted cytokines, and an increase of Treg cells.

Conclusion

The inhibition of Dectin-1 by recombinant lentiviral vector Dectin-1-RNAi inhibits the maturation and activation of DCs, affects the differentiation of T cell subsets, and prolongs allograft survival.

Targeting antigens to dendritic cell receptors for vaccine development

Dendritic cells (DCs) are highly specialized antigen presenting cells of the immune system which play a key role in regulating immune responses. Depending on the method of antigen delivery, DCs stimulate immune responses or induce tolerance. As a consequence of the dual function of DCs, DCs are studied in the context of immunotherapy for both cancer and autoimmune diseases. In vaccine development, a major aim is to induce strong, specific T-cell responses. This is achieved by targeting antigen to cell surface molecules on DCs that efficiently channel the antigen into endocytic compartments for loading onto MHC molecules and stimulation of T-cell responses. The most attractive cell surface receptors, expressed on DCs used as targets for antigen delivery for cancer and other diseases, are discussed.

Theoretical development and critical analysis of burst frequency equations for passive valves on centrifugal microfluidic platforms

This paper presents a theoretical development and critical analysis of the burst frequency equations for capillary valves on a microfluidic compact disc (CD) platform. This analysis includes background on passive capillary valves and the governing models/equations that have been developed to date. The implicit assumptions and limitations of these models are discussed. The fluid meniscus dynamics before bursting is broken up into a multi-stage model and a more accurate version of the burst frequency equation for the capillary valves is proposed. The modified equations are used to evaluate the effects of various CD design parameters such as the hydraulic diameter, the height to width aspect ratio, and the opening wedge angle of the channel on the burst pressure.

Dendritic cell-directed vaccination with a lentivector encoding PSCA for prostate cancer in mice

Many studies have demonstrated that prostate stem cell antigen (PSCA) is an attractive target for immunotherapy based on its overexpression in prostate tumor tissue, especially in some metastatic tissues. In this study, we evaluated dendritic cell (DC)-directed lentiviral vector (DCLV) encoding murine PSCA (DCLV-PSCA) as a novel tumor vaccine for prostate cancer in mouse models. We showed that DCLV-PSCA could preferentially deliver the PSCA antigen gene to DC-SIGN-expressing 293T cells and bone marrow-derived DCs (BMDCs). Direct immunization with the DCLV-PSCA in male C57BL/6 mice elicited robust PSCA-responsive CD8⁺ and CD4⁺ T cells in vivo. In a transgenic adenocarcinoma mouse prostate cell line (TRAMP-C1) synergetic tumor model, we further demonstrated that DCLV-PSCA-vaccinated mice could be protected from lethal tumor challenge in a prophylactic model, whereas slower tumor growth was observed in a therapeutic model. This DCLV-PSCA vaccine also showed efficacy in inhibiting tumor metastases using a PSCA-expressing B16-F10 model. Taken together, these data suggest that DCLV is a potent vaccine carrier for PSCA in delivering anti-prostate cancer immunity.

Construction of stable producer cells to make high-titer lentiviral vectors for dendritic cell-based vaccination

Lentiviral vectors (LVs) enveloped with an engineered Sindbis virus glycoprotein can specifically bind to dendritic cells (DCs) through the surface receptor DC-SIGN and induce antigen expression, thus providing an efficient method for delivering DC-directed vaccines. In this study, we constructed a stable producer line (LV-MGFP) for synthesizing DC-SIGN-targeted HIV-1-based LVs (DC-LVs) encoding green fluorescent protein (GFP) by a concatemeric array transfection technique. We demonstrated that the established stable clones could routinely produce vector supernatants with titers above 10(7) transduction units per milliliter (TU/mL) during a continuous 3-month cell passage. The producer cells were also capable of generating similar titers of DC-LVs in serum-free medium. Moreover, the addition of 1-deoxymannojirimycin (DMJ) enabled the producer cells to manufacture DC-LVs with both improved titers and enhanced potency to evoke antigen-specific CD8(+) T cell responses in mice. The stable lines could accommodate the replacement of the internal murine stem cell virus (MSCV) promoter with the human ubiquitin-C (Ubi) promoter in the lentiviral backbone. The resulting DC-LVs bearing Ubi exhibited the enhanced potency to elicit vaccine-specific immunity. Based on accumulated evidence, our studies support the application of this production method in manufacturing DC-LVs for preclinical and clinical testing of novel DC-based immunization.