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From the * Surgery Branch, National Cancer Institute, National Institutes of Health, Bethesda,
Maryland 20892; and the Dendritic cells (DCs) are bone marrow-derived leukocytes that function as potent antigen presenting cells capable of initiating T cell-dependent responses from quiescent lymphocytes. DC
pulsed with tumor-associated antigen (TAA) peptide or protein have recently been demonstrated to elicit antigen-specific protective antitumor immunity in a number of murine models.
Transduction of DCs with TAA genes may allow stable, prolonged antigen expression as well as the potential for presentation of multiple, or unidentified, epitopes in association with major
histocompatibility complex class I and/or class II molecules. To evaluate the potential efficacy of retrovirally transduced DCs, bone marrow cells harvested from BALB/c mice were transduced with either a model antigen gene encoding
Howard Hughes Medical Institute-National Institutes of Health Research
Scholars Program, Bethesda, Maryland 20814
-galactosidase (
-gal) or a control gene encoding rat HER-2/neu (Neu) by coculture with irradiated ecotropic retroviral producer lines.
Bone marrow cells were differentiated into DC in vitro using granulocyte/macrophage colony-stimulating factor and interleukin-4. After 7 d in culture, cells were 45-78% double positive for DC phenotypic cell surface markers by FACS® analysis, and DC transduced with
-gal
were 41-72% positive for
-gal expression by X-gal staining. In addition, coculture of
-gal
transduced DC with a
-gal-specific T cell line (CTLx) resulted in the production of large
amounts of interferon-
, demonstrating that transduced DCs could process and present endogenously expressed
-gal. DC transduced with
-gal and control rat HER-2/neu were then
used to treat 3-d lung metastases in mice bearing an experimental murine tumor CT26.CL25,
expressing the model antigen,
-gal. Treatment with
-gal-transduced DC significantly reduced the number of pulmonary metastatic nodules compared with treatment with Hank's balanced salt solution or DCs transduced with rat HER-2/neu. In addition, immunization with
-gal-transduced DCs resulted in the generation of antigen-specific cytotoxic T lymphocytes
(CTLs), which were significantly more reactive against relevant tumor targets than CTLs generated from mice immunized with DCs pulsed with the Ld-restricted
-gal peptide. The results
observed in this rapidly lethal tumor model suggest that DCs transduced with TAA may be a
useful treatment modality in tumor immunotherapy.
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