Impaired dendritic cell maturation in patients with chronic, but not resolved, hepatitis C virus infection.

Dendritic cells (DCs) are important for the initiation of immune responses to foreign antigens. Their antigen uptake and presentation capacities enable them to prime and activate T cells. Immature DCs capture antigens; however, they must be activated to mature before serving as efficient antigen-presenting cells. The antigen-presenting capacity of DCs can be diminished during viral infection and as a consequence of tumor formation. Chronic infection with hepatitis C virus (HCV) has been shown to affect the allostimulatory function of DCs. In this study, it is demonstrated that monocyte-derived DCs from patients with chronic HCV infection do not respond to maturation stimuli. Instead, they maintain their immature phenotype, reflected by the pattern of cell surface markers and by their continued capacity to uptake antigen. Moreover, their allostimulatory abilities are impaired compared with those of mature DCs derived from healthy donors. To investigate a possible correlation between viral clearance and this DC maturation defect, patients with resolved HCV infection after a course of antiviral therapy were studied. Results demonstrate that DCs from patients who cleared HCV behaved like DCs from healthy donors: in response to maturation stimuli, they decrease antigen uptake, up-regulate expression of appropriate surface markers, and are potent stimulators of allogeneic T cells. (Blood. 2001;97:3171-3176)

Detection of CD4 T-cell responses to a tumor vaccine by cytokine flow cytometry.

Cytokine flow cytometry (CFC) is a simple and powerful method for measuring antigen-specific T-cell responses by detection of intracellular cytokine staining. We applied this method to the detection of CD4 T-cell responses to tumor vaccines. Patients with multiple myeloma were immunized against their autologous tumor immunoglobulin idiotype, using antigen-pulsed dendritic cell vaccination. Blood samples were drawn before and after vaccination, and CFC and proliferation assays were performed. For CFC, whole blood was incubated overnight with antigen in the presence of costimulatory antibodies to CD28 and CD49d. The blood was then treated with EDTA, erythrocytes were lysed, and leukocytes were fixed, permeabilized, and stained for intracellular cytokines [tumor necrosis factor-alpha (TNF-alpha) or IFN-gamma], CD4, and CD69. Cells were analyzed by flow cytometry and cytokine-producing CD69+ cells enumerated as a percentage of CD4 cells. Of nine patients analyzed, three demonstrated detectable CFC responses to tumor immunoglobulin and/or keyhole limpet hemocyanin (KLH) after vaccination. One of these patients responded only to KLH, whereas the other two responded to both tumor immunoglobulin and KLH. Most responses were detected with both TNF-alpha and IFN-gamma, but one patient's KLH response was detected only with TNF-alpha. There was a positive, but not strong, correlation of cytokine responses with proliferative responses to KLH. Although further follow-up and correlation with clinical outcome is needed, CFC may represent a simple yet detailed assessment of T-cell frequencies and subsets responding to cancer vaccines.

Idiotype vaccination using dendritic cells after autologous peripheral blood progenitor cell transplantation for multiple myeloma.

The idiotype (Id) determinants on the multiple myeloma immunoglobulin can serve as tumor-specific antigens. An anti-Id immune response may stem the growth of the malignant clone. We report on 26 patients treated at our institution with high-dose chemotherapy and peripheral blood progenitor cell transplantation (PBPCT) and vaccinated with the Id protein. The patients received chemotherapy and PBPCT to establish a minimal residual disease state. After high-dose therapy, the patients received a series of monthly immunizations consisting of 2 intravenous infusions of dendritic cells (DCs) pulsed with either Id protein or Id coupled with keyhole limpet hemocyanin (KLH) as an immunogenic carrier protein, followed by subcutaneous boosts of Id-KLH conjugates. DCs were obtained in all patients from a leukapheresis product 3 to 9 months after PBPCT. Patients were observed for toxicity, immune responses, and tumor status. The DC infusions and the administration of Id-KLH boosts were well tolerated, with patients experiencing only minor and transient side effects. Of the patients, 24 of 26 generated a KLH-specific cellular proliferative immune response. Only 4 patients developed an Id-specific proliferative immune response. Three of these immune responders were in complete remission at the time of vaccination. A total of 17 patients are alive at a median follow-up of 30 months after transplantation. Id vaccination with autologous DCs is feasible for myeloma patients after transplantation. Id-specific cellular responses can be induced in patients who are in complete remission. Further studies are needed to increase the rate of anti-Id immune responses in patients who do not achieve complete remission.