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Biomedical subjects

Suyu Shu

Publications and source records attributed to Suyu Shu.

9 recordsLinked to original sources
PubMed2003

Hybrids of dendritic cells and tumor cells generated by electrofusion simultaneously present immunodominant epitopes from multiple human tumor-associated antigens in the context of MHC class I and class II molecules.

Hybrid cells generated by fusing dendritic cells with tumor cells (DC-TC) are currently being evaluated as cancer vaccines in preclinical models and human immunization trials. In this study, we evaluated the production of human DC-TC hybrids using an electrofusion protocol previously defined for murine cells. Human DCs were electrically fused with allogeneic melanoma cells (888mel) and were subsequently analyzed for coexpression of unique DC and TC markers using FACS and fluorescence microscopy. Dually fluorescent cells were clearly observed using both techniques after staining with Abs against distinct surface molecules suggesting that true cell fusion had occurred. We also evaluated the ability of human DC-TC hybrids to present tumor-associated epitopes in the context of both MHC class I and class II molecules. Allogeneic DCs expressing HLA-A*0201, HLA-DR beta 1*0401, and HLA-DR beta 1*0701 were fused with 888mel cells that do not express any of these MHC molecules, but do express multiple melanoma-associated Ags. DC-888mel hybrids efficiently presented HLA-A*0201-restricted epitopes from the melanoma Ags MART-1, gp100, tyrosinase, and tyrosinase-related protein 2 as evaluated by specific cytokine secretion from six distinct CTL lines. In contrast, DCs could not cross-present MHC class I-restricted epitopes after exogenously loading with gp100 protein. DC-888mel hybrids also presented HLA-DR beta 1*0401- and HLA-DR beta 1*0701-restricted peptides from gp100 to CD4(+) T cell populations. Therefore, fusions of DCs and tumor cells express both MHC class I- and class II-restricted tumor-associated epitopes and may be useful for the induction of tumor-reactive CD8(+) and CD4(+) T cells in vitro and in human vaccination trials.

Antigen Presentation↗
PubMed2003

Therapeutic efficacy of adoptive immunotherapy is predicated on in vivo antigen-specific proliferation of donor T cells.

Activated T cells with down-regulated L-selectin expression (L-sel(-)) from tumor-draining lymph nodes represent a potent source of specific immune effectors in adoptive immunotherapy. Using congenic pairs of mice and carboxyfluorescein diacetate succinimidyl ester-labeled L-sel(-) T cells, the current study analyzed in vivo proliferation of transferred cells. In the lung of MCA205 tumor-bearing mice, 6% or 0.3 x 10(6) of the 5 x 10(6) donor cells were identified 24 h after transfer. Vigorous proliferation of donor cells was evident on day 2, reaching a maximum on day 6. The proliferation was tumor-specific and CD4 T cells divided with greater magnitude than CD8 cells. Successful adoptive immunotherapy also required sublethal whole-body irradiation (WBI) of the recipient. WBI exerted its effects on facilitating specific T cell proliferation at the tumor site. Taken together, our results demonstrate that adoptively transferred T cells undergo extensive proliferation in response to the tumor and this response is associated with therapeutic efficacy.

Animals↗
PubMed2003

Considerations on clinical use of T cell immunotherapy for cancer.

The recognition by effector T lymphocytes of novel antigenic targets on tumor cells is the premise of specific, targeted immunotherapy of cancer. With the molecular characterization of peptide epitopes from melanoma antigens and, more recently, broadly expressed tumor antigens, there has been considerable enthusiasm for clinical evaluation of peptide tumor vaccines. Immunologic monitoring of vaccinated patients has demonstrated an expansion of CD8+ T cells that react with the relevant peptide and, more importantly, with native tumor. In most instances, however, vaccine-induced CD8+ T cell responses alone have not been sufficiently robust or sustained to translate into a high percentage of durable clinical responses. Vaccine strategies have also utilized dendritic cells (DCs) that have been modified to present tumor antigens. The superior antigen-processing capacity and co-stimulatory function of DCs convey a powerful stimulatory signal to both CD4+ and CD8+ T cells. Several strategies are attempting to broaden the immune response beyond single antigens by introducing the entire complement of tumor antigens into DCs. Adoptive immunotherapy is a promising strategy to recover tumor-reactive precursor T cells from patients, stimulate them to induce numerical expansion, and then re-infuse them. Ex vivo manipulation of the tumor-reactive T cells also permits cytotoxic therapy to be administered to the patient without damaging the effector cells. Recently, host lymphodepletion prior to adoptive transfer of effector T cells has resulted in an extremely high and sustained frequency of effectors that has achieved therapeutic efficacy against bulky metastatic disease in a substantial fraction of treated patients.

Antigens, Neoplasm↗
PubMed2002

Tumor-induced L-selectinhigh suppressor T cells mediate potent effector T cell blockade and cause failure of otherwise curative adoptive immunotherapy.

Tumor-specific effector T cells (T(E)) are naturally sensitized within the L-selectin(low) (CD62L(low)) fraction of tumor-draining lymph nodes (TDLN). Whether isolated from day 9 (D9) or day 12 (D12) TDLN, 5 million L-selectin(low) T(E) could be culture activated and adoptively transferred to achieve complete rejection of established intradermal, pulmonary, and brain tumors. Surprisingly, although 25 million unfractionated T cells from D9 TDLN were equally effective, even 100 million unfractionated T cells from D12 TDLN seldom prevented lethal intradermal tumor progression, despite a pronounced therapeutic excess of T(E). This highly reproducible treatment failure was due to cotransfer of tumor-induced, L-selectin(high) suppressor T cells (T(S)) which were also present in D12 TDLN. In contrast, D9 TDLN and normal spleens lacked L-selectin(high) T(S). Only those L-selectin(high) D12 TDLN T cells that down-regulated L-selectin during culture activation were suppressive in vivo and in vitro, and, like L-selectin(low) T(E), trafficked promptly into tumors following i.v. administration. This is the first demonstration that adoptive immunotherapy can fail as a direct result of passenger T(S) that share certain phenotypic and trafficking features of T(E), even when otherwise curative doses of T(E) have been administered. Furthermore, in contrast to recently described CD4(+)CD25(+) T(S) and plasmacytoid dendritic cell-activated T(S), tumor-induced L-selectin(high) T(S) prevent tumor rejection via blockade of sensitized, activated T(E) rather than via afferent blockade.

Animals↗
PubMed2002

Immunogenicity and therapeutic efficacy of dendritic-tumor hybrid cells generated by electrofusion.

Dendritic cells (DCs) are potent antigen-presenting cells capable of inducing strong immune responses to weak tumor-associated antigens. Among various DC-based approaches, cancer immunotherapy with DC-tumor fusion hybrids offers advantages of polyclonal stimulation of a diverse array of tumor antigens. However, prevalent fusion methods using chemical fusogens such as polyethylene glycol often result in toxicity and low fusion efficiency. In this article, we describe an electrofusion technique, applicable to processing large numbers of cells with consistent and high fusion efficiency. Generation of fusion hybrids was verified by unequivocal experimental evidence. In animal models, fusion hybrids expressed the mature DC-like phenotype. They stimulated both CD4 and CD8 tumor-specific T cells to secrete interferon-gamma in vitro. In immunotherapy, a single vaccination with DC-tumor fusion cells along with interleukin-12 as an adjuvant eradicated tumors established in the skin nd lung. These results provide an impetus for treating cancer patients with similarly generated cells.

Animals↗
PubMed2002

Therapeutic immune response induced by electrofusion of dendritic and tumor cells.

To elicit a therapeutic antitumor immune response, dendritic cells (DCs) have been employed as a cellular adjuvant. Among various DC-based approaches, fusion of DCs and tumor cells potentially confers not only DC functionality, but also a continuous source of unaltered tumor antigens. We have recently demonstrated successful generation of fusion hybrids by a large-scale electrofusion technique. The immunogenicity and therapeutic potential of fusion hybrids were further analyzed in a model system of a murine melanoma cell line expressing beta-galactosidase (beta-gal) as a surrogate tumor antigen. A single vaccination with fusion hybrids plus IL-12 induced a therapeutic immune response against 3-day established pulmonary metastases. This immunotherapy was beta-gal specific and involved both CD4 and CD8 T cells. In vitro, fusion hybrids stimulated specific IFN-gamma secretion from both CD4 and CD8 immune T cells. They also nonspecifically induced IL-10 secretion from CD4 but not CD8 T cells. Compared to other DC loadings, our results demonstrate the superior immunogenicity of fusion. The current technique of electrofusion is adequately developed for clinical use in cancer immunotherapy.

Adjuvants, Immunologic↗
PubMedDate not supplied

Depletion of CD4+ CD25+ regulatory cells augments the generation of specific immune T cells in tumor-draining lymph nodes.

Recent studies have identified a unique population of CD4+CD25+ regulatory T cells that is crucial for the prevention of spontaneous autoimmune diseases. Further studies demonstrated that depletion of CD4+CD25+ T cells enhances immune responses to nonself antigens. Because immune responses to malignant tumors are weak and ineffective, depletion of regulatory T cells has been reported to result in tumor regression. In the current study, using the weakly immunogenic MCA205 sarcoma and the poorly immunogenic B16/BL6/D5 (D5) melanoma, depletion of CD4+CD25+ T cells by the administration of anti-CD25 monoclonal antibodies (mAb), PC61 induced some tumor growth retardation, but all mice eventually succumbed to tumors. In our laboratory, immunotherapy by the transfer of tumor-immune T cells has demonstrated potent antitumor effects. A reliable source of tumor-reactive T cells has been lymph nodes (LN) draining progressive tumors. Therapeutic effector T cells can be generated by in vitro activation of draining LN cells with anti-CD3 mAb followed by culture in interleukin-2. In this system, PC61 mAb depletion of CD4+CD25+ T cells before or on day 8 of tumor growth resulted in increased sensitization in the draining LN. The therapeutic efficacy of activated tumor-draining LN cells from mAb depleted mice increased approximately three fold while maintaining specificity when tested in adoptive immunotherapy of established pulmonary metastases. Specific interferon-gamma secretion by LN T cells from mice treated with PC61 mAb 1 day before tumor inoculation increased significantly. However, this increase was not demonstrated with LN T cells from mice treated on day 8 despite their enhanced therapeutic reactivities. Our results indicate that although the antitumor immunity enhanced by the depletion of CD4+CD25+ T cells is insufficient to eradicate tumors, it augments the sensitization of immune T cells in the draining LN, thus, facilitating adoptive immunotherapy.

Animals↗