title: Depletion of CD25+ cells from human T-cell enriched fraction eliminates immunodominance during priming with dendritic cells genetically modified to express a secreted protein.
abstract: The ability of dendritic cells (DCs), genetically modified with one of two types of plasmid DNA vaccines to stimulate lymphocytes from normal human donors and to generate antigen-specific responses, is compared. The first type, also called "secreted" vaccine (sVac), encodes for the full length of the human prostate-specific antigen (PSA) with a signal peptide sequence so that the expressed product is glycosylated and directed to the secretory pathway. The second type, truncated vaccines (tVacs), encodes for either hPSA or human prostate acidic phosphatase (hPAP), both of which lack signal peptide sequences and are retained in the cytosol and degraded by the proteasomes following expression. Monocyte-derived dendritic cells are transiently transfected with either sVac or one of two tVacs. The DCs are then used to activate CD25+-depleted or nondepleted autologous lymphocytes in an in vitro model of DNA vaccination. Lymphocytes are boosted following priming with transfected DCs, peptide-pulsed DCs or monocytes. Their reactivity is tested against tumor cells or peptide-pulsed T2 target cells. Both tVacDCs and sVacDCs generate antigen-specific cytotoxic T-cell responses. The immune response is restricted towards one of the three antigen-derived epitopes when priming and boosting is performed with sVacDCs. In contrast, tVac-transfected DCs prime T cells towards all antigen-derived epitopes. Subsequent repeated boosting with transfected DCs, however, restricts the immune response to a single epitope due to immunodominance. While CD25+ cell depletion prior to priming with sVacDCs alleviates immunodominance, cotransfection of dendritic cells with GITR-L does so in some but not all cases.
authors.affiliation: Tumor Immunology Laboratory, Department of Medicine, The George Washington University Medical Center, Washington, DC 20037, USA. mcamsm@gwumc.edu
authors.forename: Milcho
authors.initials: M
authors.lastname: Mincheff
authors.forename: Serguei
authors.initials: S
authors.lastname: Zoubak
authors.forename: Iskra
authors.initials: I
authors.lastname: Altankova
authors.forename: Stoyan
authors.initials: S
authors.lastname: Tchakarov
authors.forename: Petro
authors.initials: P
authors.lastname: Pogribnyy
authors.forename: Yevgen
authors.initials: Y
authors.lastname: Makogonenko
authors.forename: Chavdar
authors.initials: C
authors.lastname: Botev
authors.forename: Harold T
authors.initials: HT
authors.lastname: Meryman
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D019556:COS Cells; D002522:Chlorocebus aethiops; D003713:Dendritic Cells / Q000276:immunology*; D000939:Epitopes / Q000276:immunology; D053450:Glucocorticoid-Induced TNFR-Related Protein; D006031:Glycosylation; D006801:Humans; D008213:Lymphocyte Activation; D008212:Lymphocyte Depletion; D008297:Male; D009000:Monocytes / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D010446:Peptide Fragments / Q000276:immunology; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D017430:Prostate-Specific Antigen / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000235:genetics / Q000276:immunology / Q000628:therapy*; D015375:Receptors, Interleukin-2 / Q000378:metabolism*; D017475:Receptors, Nerve Growth Factor / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014162:Transfection; D014611:Vaccination; D019444:Vaccines, DNA
chemical_list: D000939:Epitopes; D053450:Glucocorticoid-Induced TNFR-Related Protein; D010446:Peptide Fragments; D015375:Receptors, Interleukin-2; D017475:Receptors, Nerve Growth Factor; D018124:Receptors, Tumor Necrosis Factor; C491405:TNFRSF18 protein, human; D019444:Vaccines, DNA; D010749:Phosphoprotein Phosphatases; D017430:Prostate-Specific Antigen