Monitoring of CD4+ and CD8+ T-cell responses after dendritic cell-based immunotherapy using CFSE dye dilution analysis

Methods to Assess Proliferation of Stimulated Human Lymphocytes In Vitro: A Narrative Review

The ability to monitor lymphocyte responses is critical for developing our understanding of the immune response in humans. In the current clinical setting, relying on the metabolic incorporation of [³H] thymidine into cellular DNA via a lymphocyte proliferation test (LPT) is the only method that is routinely performed to determine cell proliferation. However, techniques that measure DNA synthesis with a radioactive material such as [³H] thymidine are intrinsically more sensitive to the different stages of the cell cycle, which could lead to over-analyses and the subsequent inaccurate interpretation of the information provided. With cell proliferation assays, the output should preferably provide a direct and accurate measurement of the number of actively dividing cells, regardless of the stimuli properties or length of exposure. In fact, an ideal technique should have the capacity to measure lymphocyte responses on both a quantitative level, i.e., cumulative magnitude of lymphoproliferative response, and a qualitative level, i.e., phenotypical and functional characterization of stimulated immune cells. There are many LPT alternatives currently available to measure various aspects of cell proliferation. Of the nine techniques discussed, we noted that the majority of these LPT alternatives measure lymphocyte proliferation using flow cytometry. Across some of these alternatives, the covalent labelling of cells with a high fluorescence intensity and low variance with minimal cell toxicity while maximizing the number of detectable cell divisions or magnitude of proliferation was achieved. Herein, we review the performance of these different LPT alternatives and address their compatibility with the [³H] thymidine LPT so as to identify the "best" alternative to the [³H] thymidine LPT.

Dendritic cell based tumor vaccination in prostate and renal cell cancer: a systematic review and meta-analysis

BACKGROUND

More than 200 clinical trials have been performed using dendritic cells (DC) as cellular adjuvants in cancer. Yet the key question whether there is a link between immune and clinical response remains unanswered. Prostate and renal cell cancer (RCC) have been extensively studied for DC-based immunotherapeutic interventions and were therefore chosen to address the above question by means of a systematic review and meta-analysis.

METHODOLOGY/PRINCIPAL FINDINGS

Data was obtained after a systematic literature search from clinical trials that enrolled at least 6 patients. Individual patient data meta-analysis was performed by means of conditional logistic regression grouped by study. Twenty nine trials involving a total of 906 patients were identified in prostate cancer (17) and RCC (12). Objective response rates were 7.7% in prostate cancer and 12.7% in RCC. The combined percentages of objective responses and stable diseases (SD) amounted to a clinical benefit rate (CBR) of 54% in prostate cancer and 48% in RCC. Meta-analysis of individual patient data (n = 403) revealed the cellular immune response to have a significant influence on CBR, both in prostate cancer (OR 10.6, 95% CI 2.5-44.1) and in RCC (OR 8.4, 95% CI 1.3-53.0). Furthermore, DC dose was found to have a significant influence on CBR in both entities. Finally, for the larger cohort of prostate cancer patients, an influence of DC maturity and DC subtype (density enriched versus monocyte derived DC) as well as access to draining lymph nodes on clinical outcome could be demonstrated.

CONCLUSIONS/SIGNIFICANCE

As a 'proof of principle' a statistically significant effect of DC-mediated cellular immune response and of DC dose on CBR could be demonstrated. Further findings concerning vaccine composition, quality control, and the effect of DC maturation status are relevant for the immunological development of DC-based vaccines.

Upfront immunization with autologous recombinant idiotype Fab fragment without prior cytoreduction in indolent B-cell lymphoma

Idiotype vaccination for follicular lymphoma is primarily being developed as remission consolidation after chemotherapy. We investigated idiotype vaccination as primary intervention for treatment-naive indolent B-cell lymphoma and in a separate cohort as remission consolidation after chemotherapy to assess immunization-induced immune responses in relation to progression-free survival (German Clinical Trials Register, DRKS00000227). Twenty-one patients in each cohort received 6 intradermal injections of adjuvanted recombinant idiotype Fab fragment (FabId); 76% of patients in both groups developed anti-idiotype antibodies and/or cellular immunity as measured by enzyme-linked immunosorbent assay and interferon-γ ELISpot. In treatment-naive patients, only cellular responses correlated with superior progression-free survival (P < .002) and durable objective remissions (P = .04). Immunization-induced T cells recognized hypermutated or complementarity-determining region 3 epitopes. After remission consolidation immunization, induction of anti-idiotype antibodies correlated with progression-free survival. Low B-cell counts after rituximab therapy predicted for failure to develop anti-idiotype antibodies. These results are similar to published trials showing an association of humoral immunity with control of residual lymphoma. In contrast, effective immunity against untreated lymphoma appears to be dependent on idiotype-specific T cells. Sustained remissions in patients with vaccination-induced cellular immunity suggest clinical benefit and warrant a randomized comparison of this vaccine with expectant management for asymptomatic follicular lymphoma.

Harnessing naturally occurring tumor immunity: a clinical vaccine trial in prostate cancer

BACKGROUND

Studies of patients with paraneoplastic neurologic disorders (PND) have revealed that apoptotic tumor serves as a potential potent trigger for the initiation of naturally occurring tumor immunity. The purpose of this study was to assess the feasibility, safety, and immunogenicity of an apoptotic tumor-autologous dendritic cell (DC) vaccine.

METHODS AND FINDINGS

We have modeled PND tumor immunity in a clinical trial in which apoptotic allogeneic prostate tumor cells were used to generate an apoptotic tumor-autologous dendritic cell vaccine. Twenty-four prostate cancer patients were immunized in a Phase I, randomized, single-blind, placebo-controlled study to assess the safety and immunogenicity of this vaccine. Vaccinations were safe and well tolerated. Importantly, we also found that the vaccine was immunogenic, inducing delayed type hypersensitivity (DTH) responses and CD4+ and CD8+ T cell proliferation, with no effect on FoxP3+ regulatory T cells. A statistically significant increase in T cell proliferation responses to prostate tumor cells in vitro (p = 0.002), decrease in prostate specific antigen (PSA) slope (p = 0.016), and a two-fold increase in PSA doubling time (p = 0.003) were identified when we compared data before and after vaccination.

CONCLUSIONS

An apoptotic cancer cell vaccine modeled on naturally occurring tumor immune responses in PND patients provides a safe and immunogenic tumor vaccine.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00289341.

Tracking antigen-driven responses by flow cytometry: monitoring proliferation by dye dilution

Cell-tracking reagents such as the green-fluorescent protein labeling dye CFSE and the red-fluorescent lipophilic membrane dye PKH26 are commonly used to monitor cell proliferation by flow cytometry in heterogeneous cell populations responding to immune stimuli. Both reagents stain cells with a bright homogeneous fluorescence, which is partitioned between daughter cells during each cell division. Because daughter cell fluorescence intensities are approximately halved after each division, the intensity of a cell relative to its intensity at the time of staining provides information about how many divisions it has undergone. Knowing how many rounds of division have occurred and the relative number of cells in each daughter generation, one can back-calculate the number of cells in the original population (i.e., cells present at the time of stimulus) that went on to respond by proliferating. Using this information, the precursor cell frequencies and extent of expansion to a specific antigen or mitogen of interest can be calculated. Concurrently, the phenotype of the cells can be determined, as well as their ability to bind antigen or synthesize cytokines, providing more detailed characterization of all cells responding to the antigen, not just effector cells. In multiparameter flow cytometric experiments to simultaneously analyze antigen-specific tetramer binding, cytokine production and T-cell proliferation, we found that only approximately half of the cells that exhibited specific binding to influenza tetramer also proliferated, as measured by dye dilution, and synthesized IFNgamma in response to antigen. We expect the advent of new cell tracking dyes emitting from the violet to the near infrared combined with the increasing number of lasers and detectors on contemporary flow cytometers to further expand the usefulness of this approach to characterization of complex antigen-driven immunological responses.

Lymphocyte blastogenic response to ovalbumin in a model for canine allergy

Lymphocyte stimulation tests (LST) were performed in five dogs sensitised with ovalbumin (OVA) and seven healthy dogs. In addition, all five OVA-sensitised and two control dogs were tested after two in vivo provocations with OVA-containing eye drops. The isolated cells were suspended in culture media containing OVA and were cultured for up to 12 days. Proliferation was measured as reduction in 5,6-carboxylfluorescein diacetate succinimidyl ester (CFSE) intensity by flow cytometry on days 0, 3, 6, 9 and 12. A cell proliferation index (CPI) for each day and the area under the curve (AUC) of the CPI was calculated for each dog. All OVA-sensitised dogs demonstrated increased erythema after conjunctival OVA application. The presence of OVA-specific lymphocytes was demonstrated in 2/5 OVA-sensitised dogs before and 4/5 after in vivo provocation. Using the AUC, the difference between OVA-sensitised and control dogs was significant in all three LST before in vivo provocation (P<0.05) and borderline significant (P=0.053) in 2/3 LST after provocation. The most significant difference in CPI was observed after 9 days of culture (P=0.001). This pilot study indicates that the LST allows detection of rare antigen specific memory T-cells in dogs previously sensitised to, but not concurrently undergoing challenge by a specific antigen.

Interferon-beta therapy reduces CD4+ and CD8+ T-cell reactivity in multiple sclerosis

Therapy with interferon-beta (IFN-beta) has well-established clinical effects in multiple sclerosis (MS), albeit the immunomodulatory mechanisms are not fully understood. We assessed the prevalence and functional capacity of CD4+ and CD8+ T cells in healthy donors, and in untreated and IFN-beta-treated MS patients, in response to myelin oligodendrocyte glycoprotein (MOG). The proportion of CD45RO+ memory T cells was higher in MS patients than in healthy donors, but returned to normal values upon therapy with IFN-beta. While CD45RO+ CD4+ T cells from all three groups responded to MOG in vitro, untreated patients showed augmented proliferative responses compared to healthy individuals and IFN-beta treatment reduced this elevated reactivity back to the values observed in healthy donors. Similarly, the response of CD45RO+ CD8+ T cells to MOG was strongest in untreated patients and decreased to normal values upon immunotherapy. Overall, the frequency of peripheral CD45RO+ memory T cells ex vivo correlated with the strength of the cellular in vitro response to MOG in untreated patients but not in healthy donors or IFN-beta-treated patients. Compared with healthy individuals, responding CD4+ and CD8+ cells were skewed towards a type 1 cytokine phenotype in untreated patients, but towards a type 2 phenotype under IFN-beta therapy. Our data suggest that the beneficial effect of IFN-beta in MS might be the result of the suppression or depletion of autoreactive, pro-inflammatory memory T cells in the periphery. Assessment of T-cell subsets and their reactivity to MOG may represent an important diagnostic tool for monitoring successful immunotherapy in MS.

Lipids in dendritic cell biology: messengers, effectors, and antigens

Dendritic cells (DC) are the most professional APC, which induce and coordinate immune responses. The principal task of DC is T cell activation, although DC also interact with and regulate other cell types. The present review serves to illustrate the increasing evidence that lipids play an important role in DC biology. In addition to being fuel stores and structural components of cellular membranes such as in other cell types, lipids act as second messengers and as effectors throughout all steps of DC differentiation and regulate important DC functions. The recent finding that DC synthesize lipid antigens in response to bacterial stimulation and induce antibacterial, CD1-restricted T cells through antigenic mimicry further emphasizes the important role of lipids and DC at the blurring boundaries of innate and adaptive immunity.

Ex vivo analysis of T-cell function

Our ability to analyze T-cell function in vitro has progressed in recent years to include analysis of early signaling events, such as specific protein phosphorylation, intermediate functions, such as degranulation and cytokine production, and later functions, such as proliferation. Many assays are now available to monitor these events, and comparative studies of some of these assays have been published. Major recent developments in this area include the ability to measure T-cell degranulation via cell surface exposure of CD107 and the use of polychromatic flow cytometry to examine multiple phenotypes and functions of responding T cells.