Monika Sachet

Dendritic cell vaccination in medullary thyroid carcinoma.

Purpose: Prognosis and treatment effectiveness for medullary thyroid carcinoma (MTC) are strictly related to tumor stage. Palliative treatment options show no significant benefit. A promising treatment approach for human cancer is based on the vaccination of autologous dendritic cells (DCs). Experimental Design: The objective of this study was to evaluate the effectiveness of DC vaccines in MTC patients. Therefore, we generated autologous tumor lysate-pulsed DCs from 10 patients suffering from advanced MTC for repeated vaccination. Mature DCs were derived from peripheral blood monocytes by using CD14 magnetic bead selection and subsequent culture in the presence of granulocyte macrophage colony-stimulating factor, interleukin 4, and tumor necrosis factor α with or without addition of IFN-γ. DCs were loaded with tumor lysate and further injected into a groin lymph node. Toxicity, tumor marker profile, immune response, and clinical response were determined. Results: Vaccination was well tolerated and induced a positive immunological response in all of the tested patients as evaluated by in vivo delayed-type hypersensitivity reactivity or in vitro intracytoplasmic IFN-γ detection assay. Three patients had a partial response, 1 patient presented a minor response, and 2 patients showed stable disease. The remaining 4 patients had progressive disease. Conclusions: These data provide strong evidence that vaccination with tumor-lysate pulsed DCs results in the induction of a specific immune response in patients suffering from MTC. Objective clinical responses could be observed even for far-advanced disease. Therefore, we suggest that MTC is particularly suited for DC-based immunotherapy.

Preclinical Evaluation of a Replication-Deficient Intranasal ΔNS1 H5N1 Influenza Vaccine

Background We developed a novel intranasal influenza vaccine approach that is based on the construction of replication-deficient vaccine viruses that lack the entire NS1 gene (ΔNS1 virus). We previously showed that these viruses undergo abortive replication in the respiratory tract of animals. The local release of type I interferons and other cytokines and chemokines in the upper respiratory tract may have a “self-adjuvant effect”, in turn increasing vaccine immunogenicity. As a result, ΔNS1 viruses elicit strong B- and T- cell mediated immune responses. Methodology/Principal Findings We applied this technology to the development of a pandemic H5N1 vaccine candidate. The vaccine virus was constructed by reverse genetics in Vero cells, as a 5∶3 reassortant, encoding four proteins HA, NA, M1, and M2 of the A/Vietnam/1203/04 virus while the remaining genes were derived from IVR-116. The HA cleavage site was modified in a trypsin dependent manner, serving as the second attenuation factor in addition to the deleted NS1 gene. The vaccine candidate was able to grow in the Vero cells that were cultivated in a serum free medium to titers exceeding 8 log10 TCID50/ml. The vaccine virus was replication deficient in interferon competent cells and did not lead to viral shedding in the vaccinated animals. The studies performed in three animal models confirmed the safety and immunogenicity of the vaccine. Intranasal immunization protected ferrets and mice from being infected with influenza H5 viruses of different clades. In a primate model (Macaca mulatta), one dose of vaccine delivered intranasally was sufficient for the induction of antibodies against homologous A/Vietnam/1203/04 and heterologous A/Indonesia/5/05 H5N1 strains. Conclusion/Significance Our findings show that intranasal immunization with the replication deficient H5N1 ΔNS1 vaccine candidate is sufficient to induce a protective immune response against H5N1 viruses. This approach might be attractive as an alternative to conventional influenza vaccines. Clinical evaluation of ΔNS1 pandemic and seasonal influenza vaccine candidates are currently in progress.

Interferon resistance promotes oncolysis by influenza virus NS1-deletion mutants.

NS1 protein of influenza virus is a virulence factor that counteracts Type I interferon (IFN)‐mediated antiviral response by the host. A recombinant influenza A virus that lacks the NS1 protein only replicates efficiently in systems that contain defective IFN pathways. We demonstrate that the conditional replication properties of NS1‐modified influenza A virus mutants can be exploited for the virus‐mediated oncolysis of IFN‐resistant tumor cells. IFN resistance in analyzed tumor cell lines correlated with a reduced expression of STAT1. Addition of exogenous IFNα or supernatant of virus‐infected endothelial cells inhibited viral oncolysis in IFN‐sensitive but not in IFN‐resistant cell lines. The oncolytic potential of NS1‐modified influenza A virus mutants could be exploited in vivo in a SCID mouse model of a subcutaneously‐implanted human IFN‐resistant melanoma. The data indicate that IFN‐resistant tumors are a suitable target for oncolysis induced by NS1‐modified influenza virus mutants. STAT1 might serve as a marker to identify these IFN‐resistant tumors.

Trastuzumab mediates antibody-dependent cell-mediated cytotoxicity and phagocytosis to the same extent in both adjuvant and metastatic HER2/neu breast cancer patients

BackgroundMonoclonal antibodies (mAb), such as trastuzumab are a valuable addition to breast cancer therapy. Data obtained from neoadjuvant settings revealed that antibody-dependent cell-mediated cytotoxicity (ADCC) is a major mechanism of action for the mAb trastuzumab. Conflicting results still call into question whether disease progression, prolonged treatment or concomitant chemotherapy influences ADCC and related immunological phenomena.MethodsWe analyzed the activity of ADCC and antibody-dependent cell-mediated phagocytosis (ADCP) of peripheral blood mononuclear cells (PBMCs) from human epidermal growth factor receptor 2 (HER2/neu) positive breast cancer patients receiving trastuzumab therapy either in an adjuvant (n = 13) or metastatic (n = 15) setting as well as from trastuzumab treatment-naive (t-naive) HER2/neu negative patients (n = 15). PBMCs from healthy volunteers (n = 24) were used as controls. ADCC and ADCP activity was correlated with the expression of antibody binding Fc-gamma receptor (FcγR)I (CD64), FcγRII (CD32) and FcγRIII (CD16) on CD14+ (monocytes) and CD56+ (NK) cells, as well as the expression of CD107a+ (LAMP-1) on CD56+ cells and the total amount of CD4+CD25+FOXP3+ (Treg) cells. In metastatic patients, markers were correlated with progression-free survival (PFS).ResultsADCC activity was significantly down regulated in metastatic, adjuvant and t-naive patient cohorts as compared to healthy controls. Reduced ADCC activity was inversely correlated with the expression of CD107a on CD56+ cells in adjuvant patients. ADCC and ADCP activity of the patient cohorts were similar, regardless of treatment duration or additional chemotherapy. PFS in metastatic patients inversely correlated with the number of peripheral Treg cells.ConclusionThe reduction of ADCC in patients as compared to healthy controls calls for adjuvant strategies, such as immune-enhancing agents, to improve the activity of trastuzumab. However, efficacy of trastuzumab-specific ADCC and ADCP appears not to be affected by treatment duration, disease progression or concomitant chemotherapy. This finding supports the application of trastuzumab at any stage of the disease.

Cl097, a TLR7/8 ligand, inhibits TLR-4-dependent activation of IRAK-M and BCL-3 expression

Prolonged or repeated stimulation of Toll-like receptor (TLR) 4 leads to hyporesponsiveness of monocyte-derived macrophages, which seems to be a hallmark of immunosuppression related to sepsis and cancer. Two negative regulators of TLR-4 signaling are IL-1 receptor-associated kinase M and B-cell leukemia 3. Here, we demonstrate that the expression of both proteins is inhibited when the TLR-7/TLR-8 agonist CL097 is added to monocyte cultures despite costimulation with the TLR-4 agonist LPS or hyaluronic acid. Reduction of IL-1 receptor-associated kinase M and B-cell leukemia 3 was paralleled by a significant increased cytokine induction of TNF-&agr;, IL-10, and IL-12 observed after intracellular and extracellular TLR stimulation. In ex vivo stimulated whole blood of patients who have prolonged sepsis or metastatic cancer, TLR-7/TLR-8 agonists retained their ability of increased stimulation of TNF-&agr;. These data might add to the understanding of sepsis and cancer-associated immune suppression in men.

IL-24 sensitizes tumor cells to TLR3-mediated apoptosis.

Interleukin-24 (IL-24), a member of the IL-10 cytokine family whose physiological function remains largely unknown, has been shown to induce apoptosis when expressed in an adenoviral background. It is yet little understood, why IL-24 alone induced apoptosis only in a limited number of tumor cell lines. Analyzing an influenza A virus vector expressing IL-24 for its oncolytic potential revealed enhanced pro-apoptotic activity of the chimeric virus compared with virus or IL-24 alone. Interestingly, IL-24-mediated enhancement of influenza-A-induced apoptosis did not require viral replication but critically depended on toll-like receptor 3 (TLR3) and caspase-8. Immunoprecipitation of TLR3 showed that infection by influenza A virus induced formation of a TLR3-associated signaling complex containing TRIF, RIP1, FADD, cFLIP and pro-caspase-8. Co-administration of IL-24 decreased the presence of cFLIP in the TLR3-associated complex, converting it into an atypical, TLR3-associated death-inducing signaling complex (TLR3 DISC) that induced apoptosis by enabling caspase-8 activation at this complex. The sensitizing effect of IL-24 on TLR3-induced apoptosis, mediated by influenza A virus or the TLR3-specific agonist poly(I:C), was also evident on tumor spheroids. In conclusion, rather than acting as an apoptosis inducer itself, IL-24 sensitizes cancer cells to TLR-mediated apoptosis by enabling the formation of an atypical DISC which, in the case of influenza A virus or poly(I:C), is associated with TLR3.

The immune response to secondary necrotic cells

When apoptotic cells are not cleared in an efficient and timely manner, they progress to secondary necrosis and lose their membrane integrity. This results in a leakage of immunostimulatory, danger associated molecular patterns (DAMPs), similar to accidental (or primary) necrosis. However, primary necrosis is a sudden event with an inadvertent release of almost unmodified DAMPs. Secondary necrotic cells, in contrast, have gone through various modifications during the process of apoptosis. Recent research revealed that the molecules released from the cytoplasm or exposed on the cell surface differ between primary necrosis, secondary necrosis, and regulated necrosis such as necroptosis. This review gives an overview of these differences and focusses their effects on the immune response. The implications to human physiology and diseases are manifold and will be discussed in the context of cancer, neurodegenerative disorders and autoimmunity.

Influenza a virus induces an immediate cytotoxic activity in all major subsets of peripheral blood mononuclear cells.

Background A replication defective influenza A vaccine virus (delNS1 virus) was developed. Its attenuation is due to potent stimulation of the innate immune system by the virus. Since the innate immune system can also target cancer cells, we reasoned that delNS1 virus induced immune-stimulation should also lead to the induction of innate cytotoxic effects towards cancer cells. Methodology/Principal Findings Peripheral blood mononuclear cells (PBMCs), isolated CD56+, CD3+, CD14+ and CD19+ subsets and different combinations of the above subsets were stimulated by delNS1, wild type (wt) virus or heat inactivated virus and co-cultured with tumor cell lines in the presence or absence of antibodies against the interferon system. Stimulation of PBMCs by the delNS1 virus effectively induced cytotoxicity against different cancer cell lines. Surprisingly, virus induced cytotoxicity was exerted by all major subtypes of PBMCs including CD56+, CD3+, CD14+ and CD19+ cells. Virus induced cytotoxicity in CD3+, CD14+ and CD19+ cells was dependent on virus replication, whereas virus induced cytotoxicity in CD56+ cells was only dependent on the binding of the virus. Virus induced cytotoxicity of isolated cell cultures of CD14+, CD19+ or CD56+ cells could be partially blocked by antibodies against type I and type II (IFN) interferon. In contrast, virus induced cytotoxicity in the complete PBMC preparation could not be inhibited by blocking type I or type II IFN, indicating a redundant system of activation in whole blood. Conclusions/Significance Our data suggest that apart from their well known specialized functions all main subsets of peripheral blood cells also initially exert a cytotoxic effect upon virus stimulation. This closely links the innate immune system to the adaptive immune response and renders delNS1 virus a potential therapeutic tool for viro-immunotherapy of cancer.

Interleukin-24 inhibits influenza A virus replication in vitro through induction of toll-like receptor 3 dependent apoptosis.

New anti-viral agents and strategies are urgently needed to fight rapidly mutating viruses, as vaccine programs cannot react fast enough to prevent pandemics. Recently, we have shown that interleukin-24 (IL-24) sensitizes tumor cells to toll-like receptor 3 (TLR3) mediated apoptosis. As influenza A virus stimulates the TLR3 receptor, we hypothesized that IL-24 might also exert an anti-viral effect. This study demonstrates that IL-24 reduces the titer of different influenza A virus subtypes independently of type I interferon in an apoptosis dependent manner. The anti-viral effect of IL-24 correlated with caspase-3 activation and could be blocked by a pan-caspase inhibitor and by small interfering RNA (siRNA) directed towards TLR3. Surprisingly, caspase-3 activation in influenza A virus/IL-24-stimulated cells correlated with the down-regulation of the B-cell lymphoma 2 (Bcl-2) family member myeloid cell leukemia 1 (Mcl-1). Correspondingly, knockdown of Mcl-1 by siRNA enhanced caspase activation in influenza A virus infected cells and was furthermore linked to a reduction of viral titers. We conclude that IL-24 exerts an anti-viral role selectively purging virally infected cells by leading to a down-regulation of Mcl-1. Our findings might therefore represent the first step towards a new rational concept in the development of anti-viral strategies based on the induction of apoptosis.

Cryopreservation of Monocytes Is Superior to Cryopreservation of Immature or Semi-mature Dendritic Cells for Dendritic Cell-based Immunotherapy

Cryopreservation of immature or mature dendritic cells (DC) has been proposed as a suitable method to gain large numbers of DC for immunotherapeutic trials against cancer. However, clinical studies using cryopreserved DC have demonstrated only limited success so far. The aim of this study was to investigate whether cryopreservation of monocytes elicits more potent DC and whether these DC are comparable to freshly generated DC preparations. Monocytes, either separated immunomagnetically or by means of leukapheresis and elutriation, were differentiated into DC and cryopreserved at various developmental stages. DC preparations were analyzed regarding recovery, viability, phenotype, and functional properties. In contrast to DC frozen at their immature or semi-mature state, generation of DC from cryopreserved monocytes elicited viability values comparable with freshly generated DC. Furthermore, using frozen monocytes for DC differentiation revealed improved expression of DC surface markers and interleukin-12p70 secretion as compared with DC generated from frozen immature or frozen semi-mature DC. Impaired phenotypical appearance of the latter DC variants was further substantiated by functional analysis. T-cells cocultured with these DC showed decreased expression of interferon-γ and granzyme B, and lowered proliferation when compared with T-cells cocultured with DC generated from frozen monocytes or DC generated from freshly isolated monocytes. Induction of regulatory T-cell populations was negligible among all investigated DC preparations. These findings may further improve DC-based immunotherapeutical protocols. Cryopreservation of unchallenged monocytes enables targeted therapy by loading DC with varying antigenic compositions in case of tumor escape during treatment.