Comparative Analysis of Antigen Loading Strategies of Dendritic Cells for Tumor Immunotherapy

Abstract

Dendritic cells (DCs) loaded with antigens can effectively stimulate host immune responses to syngeneic tumors, but there is considerable controversy as to which forms of antigen-loading are most immunogenic. Here, the authors compared immunotherapeutic reactivities of DCs loaded with a variety of antigen preparations. Because DC maturation stages affect their capacities of antigen processing and presentation, two DC populations were used for the current analysis: in vivo Flt-3 ligand-induced mature DCs and in vitro bone marrow-derived DCs, which were less mature. To facilitate a direct comparison, the LacZ gene-transduced B16 melanoma model system was used, where beta-galactosidase served as the surrogate tumor-rejection antigen. DC loading strategies included pulsing with the beta-galactosidase protein, H-2K restricted peptide, tumor cell lysate, and irradiated tumor cells and fusion of DCs with tumor cells. Our results demonstrated that electrofusion of DCs and tumor cells generated a therapeutic vaccine far superior to other methods of DC loading. For the treatment of 3-day established pulmonary tumor nodules, a single intranodal vaccination plus IL-12 resulted in a significant reduction of metastatic nodules, while other DC preparations were only marginally effective. Immunotherapy mediated by the fusion cells was tumor antigen-specific. Consistent with their therapeutic activity, fusion hybrids were the most potent stimulators to induce specific IFN-gamma secretion from immune T cells. Furthermore, fusion cells also stimulated a small amount of IL-10 production from immune T cells. However, this IL-10 secretion was also induced by other DC preparations and did not correlate with in vivo therapeutic reactivity.

Paired Toll-like Receptor Agonists Enhance Vaccine Therapy through Induction of Interleukin-12

“…Bone marrow DCs were prepared as previously described (14) by a modification of Inaba and colleagues (15). Briefly, cells harvested from femora and tibiae were depleted of B and T cells by negative selection with mAb-coated magnetic beads (Dynal Biotech).…”

“…The cell suspensions were then resuspended in conditioned medium and incubated overnight in a 37jC, 5% CO 2 incubator. The adherent cell fraction containing fusion hybrids was harvested and Three days later, mice were vaccinated by the intranodal route as previously described (14). Routinely, 3 Â 105 fusion cells in 10 AL HBSS were delivered to each of 2 superficial inguinal lymph nodes.…”

Induction of antigen-specific CD4- and CD8-mediated T-cell responses by fusions of autologous dendritic cells and metastatic colorectal cancer cells

“…It was shown that DCs were capable of stimulating T cells to produce IL-10 nonspecifically, and this pattern of production did not influence therapeutic responses. 43 Moreover, it was also demonstrated that IL-10 production could enhance CTL generation. 44,45 In summary, we have demonstrated, using DC/CRCA fusion cells, that (i) freshly isolated metastatic CRCA cells can be used as a fusion partner, thus expanding the source of fusion cells; (ii) both CD4…”

Antigen-Presenting Cell/Tumour Cell Hybrid Vaccines in Cancer Immunotherapy

“…These results suggest that DC/tumour fusion hybrids are stronger stimulators of protective immunity against solid tumours than other antigen-loading strategies using whole tumour cell materials [35]. Furthermore, DC/tumour cell fusion hybrids have been shown to demonstrate superior efficacy for the treatment of murine tumour models than other DC-based vaccination strategies in other studies [39][40][41][42][43]. Parameters that may require further adjustment to maximize the anti-tumour effect of DC/tumour cell fusion hybrids include the DC maturation state, fusion efficiency between DC and tumour cells, and the use of appropriate adjuvants.…”