Progression and Relapse of Pediatric Soft Tissue Sarcoma: Individualized Approach of Treatment - Experience from a Major Pediatric Cancer Center in Europe.

BACKGROUND: The outcome of children with refractory or relapsed soft tissue sarcoma (STS) is extremely poor. Whereas larger clinical trials evaluated specific treatment modalities, real-life data on individual multimodal therapeutic strategies, given alone or in combination, are scarce. PATIENTS AND METHODS: We retrospectively analyzed the clinical course of 18 pediatric patients with progression of or relapsed STS treated between 2008 and 2018 in our institution. RESULTS: A total of 18 patients (median age 12.4 years) suffered from progression or relapse of alveolar (n=7), embryonal (n=5), undifferentiated (n=2) rhabdomyosarcoma or desmoplastic small round cell tumor (n=4). 14 patents had an initial stage IV disease. All but one patient died. Median survival was 12.5 months. Shortest survival was seen in patients with systemic progression of the disease, longest in patients with local relapse. Patients with an Oberlin score<2 at the time of relapse had a significant longer time of survival than those with a score≥2. No significant advantage of a specific therapeutic modality was observed. DISCUSSION: We critically analyzed the clinical course in the real-life setting, in which various treatment options were applied to an individual patient according to the best of available data. We observed that some patients died within a short period of time despite multiple treatment modalities, which underlines the need for better prognostic parameters. CONCLUSION: In addition to well characterized clinical factors such as local or systemic relapse, the Oberlin score could be helpful in counselling patients and their families for choosing the best strategy of care.

Natural Killer Cell Line NK-92-Mediated Damage of Medically Important Fungi.

Invasive fungal disease (IFD) in hematopoietic stem cell transplantation is associated with high morbidity and mortality. As the antifungal host response determines risk and outcome of IFD, there is growing interest in adoptive immunotherapy using T cells or natural killer (NK) cells. Although the NK-92 cell line has been tested as anticancer therapy in clinical trials, data on the antifungal activity of NK-92 cells are lacking. Here, we show that the NK-92 cell line exhibits considerable fungal damage on all medically important fungi tested, such as different species of Aspergillus, Candida, mucormycetes, and Fusarium. The extent of fungal damage differs across various species of mucormycetes and Fusarium, whereas it is comparable across different species of Aspergillus and Candida. Interferon (IFN)-γ levels in the supernatant were lower when NK-92 cells are co-incubated with Aspergillus fumigatus, Candida albicans, or Rhizopus arrhizus compared to the levels when NK-92 cells are incubated alone. Different to primary human NK cells, no increase of perforin levels in the supernatant was observed when the fungi were added to NK-92 cells. Our in vitro data demonstrated that the NK-92 cell line could be a feasible tool for antifungal immunotherapy, but data of animal models are warranted prior to clinical trials.

Immunosuppressive Compounds Affect the Fungal Growth and Viability of Defined Aspergillus Species.

Immunosuppressive drugs are administered to a number of patients; e.g., to allogeneic hematopoietic stem cell transplant recipients. Immunosuppressive drugs impair the immune system and thus increase the risk of invasive fungal disease, but may exhibit antifungal activity at the same time. We investigated the impact of various concentrations of three commonly used immunosuppressive compounds-cyclosporin A (CsA), methylprednisolone (mPRED), and mycophenolic acid (MPA)-on the growth and viability of five clinically important Aspergillus species. Methods included disc diffusion, optical density of mycelium, and viability assays such as XTT. MPA and CsA had a species-specific and dose-dependent inhibitory effect on the growth of all Aspergillus spp. tested, although growth inhibition by MPA was highest in A. niger, A. flavus and A. brasiliensis. Both agents exhibited species-specific hyphal damage, which was higher when the immunosuppressants were added to growing conidia than to mycelium. In contrast, mPRED increased the growth of A. niger, but had no major impact on the growth and viability of any of the other Aspergillus species tested. Our findings may help to better understand the interaction of drugs with Aspergillus species and ultimately may have an impact on individualizing immunosuppressive therapy.

Distinct Effects of Immunosuppressive Drugs on the Anti-Aspergillus Activity of Human Natural Killer Cells.

As the prognosis of invasive aspergillosis remains unacceptably poor in patients undergoing hematopoietic stem cell transplantation (HSCT), there is a growing interest in the adoptive transfer of antifungal effector cells, such as Natural Killer (NK) cells. Because immunosuppressive agents are required in most HSCT recipients, knowledge of the impact of these compounds on the antifungal activity of NK cells is a prerequisite for clinical trials. We, therefore, assessed the effect of methylprednisolone (mPRED), cyclosporin A (CsA) and mycophenolic acid (MPA) at different concentrations on proliferation, apoptosis/necrosis, and the direct and indirect anti-Aspergillus activity of human NK cells. Methylprednisolone decreased proliferation and increased apoptosis of NK cells in a significant manner. After seven days, a reduction of viable NK cells was seen for all three immunosuppressants, which was significant for MPA only. Cyclosporin A significantly inhibited the direct hyphal damage by NK cells in a dose-dependent manner. None of the immunosuppressive compounds had a major impact on the measured levels of interferon-γ, granulocyte-macrophage colony-stimulating factor and RANTES (regulated on activation, normal T cell expressed and secreted; CCL5). Our data demonstrate that commonly used immunosuppressive compounds have distinct effects on proliferation, viability and antifungal activity of human NK cells, which should be considered in designing studies on the use of NK cells for adoptive antifungal immunotherapy.

Why are natural killer cells important for defense against Aspergillus?

There is growing evidence that natural killer (NK) cells play an important role in the host response to Aspergillus spp. In vitro data clearly demonstrate that both murine and human NK cells are able to damage Aspergillus. NK cells exert direct antifungal activity via cytotoxic molecules such as perforin, and NK cell-derived cytokines and interferons modulate proliferation and activation of a variety of immune cells in order to fight the fungus. However, in turn, Aspergillus is able to exhibit immunosuppressive effects on NK cells. Antibody-mediated depletion of NK cells in neutropenic mice infected with A. fumigatus further impairs clearance of the pathogen from the lungs and results in a higher mortality as compared to animals with NK cells. Clinical data on the impact of NK cells in the antifungal host response are less clear, as different arms of the human immune system are involved, which interact and overlap in a complex network. Future studies must better characterize the interaction of NK cells and Aspergillus and to clarify the benefit and potential risks of using NK cells as adoptive immunotherapy in patients suffering from invasive aspergillosis, which may be a significant step toward decreasing morbidity and mortality of these patients.

Impact of Antifungal Compounds on Viability and Anti-Aspergillus Activity of Human Natural Killer Cells.

Despite the availability of new antifungal compounds, invasive aspergillosis carries high morbidity and mortality in hematopoietic stem cell transplant recipients. In vitro studies and animal models suggest that the adoptive transfer of natural killer (NK) cells might be a promising immunotherapeutic option in this setting. As it is unclear whether the viability and function of human NK cells are affected by common antifungal agents, we analyzed the interaction of various concentrations of amphotericin B deoxycholate (AmB-D), liposomal amphotericin B, caspofungin, fluconazole, voriconazole, and posaconazole with human NK cells. When adding NK cells to therapeutic concentrations of antifungal agents, a significant increase in the antifungal effect was seen for caspofungin and voriconazole, whereas NK cells significantly decreased the hyphal damage of escalated doses of AmB-D. In contrast, therapeutic concentrations of all antifungal compounds tested did not have a negative effect on proliferation, viability, and the release of soluble immunomodulatory molecules of NK cells. These data indicate that therapeutic concentrations of the antifungal agents tested do not negatively affect the functional properties of human NK cells, which is a prerequisite for further studies evaluating NK cells as antifungal immunotherapy in immunocompromised patients suffering from invasive aspergillosis.

Natural killer cells as a therapeutic tool for infectious diseases - current status and future perspectives.

Natural Killer (NK) cells are involved in the host immune response against infections due to viral, bacterial and fungal pathogens, all of which are a significant cause of morbidity and mortality in immunocompromised patients. Since the recovery of the immune system has a major impact on the outcome of an infectious complication, there is major interest in strengthening the host response in immunocompromised patients, either by using cytokines or growth factors or by adoptive cellular therapies transfusing immune cells such as granulocytes or pathogen-specific T-cells. To date, relatively little is known about the potential of adoptively transferring NK cells in immunocompromised patients with infectious complications, although the anti-cancer property of NK cells is already being investigated in the clinical setting. This review will focus on the antimicrobial properties of NK cells and the current standing and future perspectives of generating and using NK cells as immunotherapy in patients with infectious complications, an approach which is promising and might have an important clinical impact in the future.

Natural Killer Cells in Antifungal Immunity.

Invasive fungal infections are still an important cause of morbidity and mortality in immunocompromised patients such as patients suffering from hematological malignancies or patients undergoing hematopoietic stem cell transplantion. In addition, other populations such as human immunodeficiency virus-patients are at higher risk for invasive fungal infection. Despite the availability of new antifungal compounds and better supportive care measures, the fatality rate of invasive fungal infection remained unacceptably high. It is therefore of major interest to improve our understanding of the host-pathogen interaction to develop new therapeutic approaches such as adoptive immunotherapy. As experimental methodologies have improved and we now better understand the complex network of the immune system, the insight in the interaction of the host with the fungus has significantly increased. It has become clear that host resistance to fungal infections is not only associated with strong innate immunity but that adaptive immunity (e.g., T cells) also plays an important role. The antifungal activity of natural killer (NK) cells has been underestimated for a long time. In vitro studies demonstrated that NK cells from murine and human origin are able to attack fungi of different genera and species. NK cells exhibit not only a direct antifungal activity via cytotoxic molecules but also an indirect antifungal activity via cytokines. However, it has been show that fungi exert immunosuppressive effects on NK cells. Whereas clinical data are scarce, animal models have clearly demonstrated that NK cells play an important role in the host response against invasive fungal infections. In this review, we summarize clinical data as well as results from in vitro and animal studies on the impact of NK cells on fungal pathogens.

Impact of human mesenchymal stromal cells on antifungal host response against Aspergillus fumigatus.

Mesenchymal stromal cells (MSCs) are increasingly given as immunotherapy to hematopoietic stem cell transplant (HSCT) recipients with refractory graft-versus-host disease (GvHD). Whereas the immunosuppressive properties of MSCs seem to be beneficial in GvHD, there is, at the same time, major concern that MSCs increase the risk for infection. We therefore investigated the interplay of human MSCs with Aspergillus fumigatus and the impact of MSCs on different arms of the anti-Aspergillus host response in vitro. Although A. fumigatus hyphae increase mRNA levels of IL6 in MSCs, the extracellular availability of IL-6 and other pro-inflammatory cytokines remains unaffected. Human MSCs are able to phagocyte Aspergillus conidia, but phagocytosis of conidia is not associated with an alteration of the cytokine production by MSCs. In addition, human MSCs do not affect activation and function of A. fumigatus specific CD4+ T cells, and MSCs do not negatively impact the oxidative burst activity of phagocytes. Our in vitro data indicate that administration of human MSCs is not associated with a negative impact on the host response against A. fumigatus and that the fungus does not stimulate MSCs to increase the release of those cytokines which play a central role in the pathophysiology of GvHD.

NK Cells and Their Role in Invasive Mold Infection.

There is growing evidence that Natural Killer (NK) cells exhibit in vitro activity against both Aspergillus and non-Aspergillus molds. Cytotoxic molecules such as NK cell-derived perforin seem to play an important role in the antifungal activity. In addition, NK cells release a number of cytokines upon stimulation by fungi, which modulate both innate and adaptive host immune responses. Whereas the in vitro data of the antifungal activity of NK cells are supported by animal studies, clinical data are scarce to date.

Role of natural killer cells in antibacterial immunity.

INTRODUCTION: Bacteria are a significant cause of infectious complications, in particular in immunocompromised patients. There is an increasing understanding that Natural Killer (NK) cells not only exhibit direct activity against bacteria, but also exert indirect antibacterial activity through interaction with other immune cells via cytokines and interferons. Areas covered: This review seeks to give a global overview of in vitro and in vivo data how NK cells interact with bacteria. In this regard, the review describes how NK cells directly damage and kill bacteria by soluble factors such as perforin, the impact of NK cells on other arms of the immune system, as well as how bacteria may inhibit NK cell activities. Expert commentary: A better characterization of the antibacterial effects of NK cells is urgently needed. With a better understanding of the interaction of NK cells and bacteria, NK cells may become a promising tool to prevent or to combat bacterial infections, e.g. by adoptively transferring NK cells to immunocompromised patients.

Aspergillus fumigatus responds to natural killer (NK) cells with upregulation of stress related genes and inhibits the immunoregulatory function of NK cells.

Natural Killer (NK) cells are active against Aspergillus fumigatus, which in turn is able to impair the host defense. Unfortunately, little is known on the mutual interaction of NK cells and A. fumigatus. We coincubated human NK cells with A. fumigatus hyphae and assessed the gene expression and protein concentration of selected molecules. We found that A. fumigatus up-regulates the gene expression of pro-inflammatory molecules in NK cells, but inhibited the release of these molecules resulting in intracellular accumulation and limited extracellular availability. A. fumigatus down-regulatedmRNA levels of perforin in NK cells, but increased its intra- and extracellular protein concentration. The gene expression of stress related molecules of A. fumigatus such as heat shock protein hsp90 was up-regulated by human NK cells. Our data characterize for the first time the immunosuppressive effect of A. fumigatus on NK cells and may help to develop new therapeutic antifungal strategies.

Vif Proteins from Diverse Human Immunodeficiency Virus/Simian Immunodeficiency Virus Lineages Have Distinct Binding Sites in A3C.

Lentiviruses have evolved the Vif protein to counteract APOBEC3 (A3) restriction factors by targeting them for proteasomal degradation. Previous studies have identified important residues in the interface of human immunodeficiency virus type 1 (HIV-1) Vif and human APOBEC3C (hA3C) or human APOBEC3F (hA3F). However, the interaction between primate A3C proteins and HIV-1 Vif or natural HIV-1 Vif variants is still poorly understood. Here, we report that HIV-1 Vif is inactive against A3Cs of rhesus macaques (rhA3C), sooty mangabey monkeys (smmA3C), and African green monkeys (agmA3C), while HIV-2, African green monkey simian immunodeficiency virus (SIVagm), and SIVmac Vif proteins efficiently mediate the depletion of all tested A3Cs. We identified that residues N/H130 and Q133 in rhA3C and smmA3C are determinants for this HIV-1 Vif-triggered counteraction. We also found that the HIV-1 Vif interaction sites in helix 4 of hA3C and hA3F differ. Vif alleles from diverse HIV-1 subtypes were tested for degradation activities related to hA3C. The subtype F-1 Vif was identified to be inactive for degradation of hA3C and hA3F. The residues that determined F-1 Vif inactivity in the degradation of A3C/A3F were located in the C-terminal region (K167 and D182). Structural analysis of F-1 Vif revealed that impairing the internal salt bridge of E171-K167 restored reduction capacities to A3C/A3F. Furthermore, we found that D101 could also form an internal interaction with K167. Replacing D101 with glycine and R167 with lysine in NL4-3 Vif impaired its counteractivity to A3F and A3C. This finding indicates that internal interactions outside the A3 binding region in HIV-1 Vif influence the capacity to induce degradation of A3C/A3F. IMPORTANCE: The APOBEC3 restriction factors can serve as potential barriers to lentiviral cross-species transmissions. Vif proteins from lentiviruses counteract APOBEC3 by proteasomal degradation. In this study, we found that monkey-derived A3C, rhA3C and smmA3C, were resistant to HIV-1 Vif. This was determined by A3C residues N/H130 and Q133. However, HIV-2, SIVagm, and SIVmac Vif proteins were found to be able to mediate the depletion of all tested primate A3C proteins. In addition, we identified a natural HIV-1 Vif (F-1 Vif) that was inactive in the degradation of hA3C/hA3F. Here, we provide for the first time a model that explains how an internal salt bridge of E171-K167-D101 influences Vif-mediated degradation of hA3C/hA3F. This finding provides a novel way to develop HIV-1 inhibitors by targeting the internal interactions of the Vif protein.

Natural killer cell-mediated damage of clinical isolates of mucormycetes.

Haematopoietic stem cell transplant (HSCT) recipients are at high risk for mucormycosis, which has a mortality of up to 90%. The adoptive transfer of Natural killer (NK) cells is a promising therapeutic option in order to improve the reconstitution of host immunity after HSCT and to directly combat the fungal pathogen. As a number of fungal pathogens have developed strategies to evade the innate immune system, we investigated the interaction of human NK cells with various clinical isolates of different species of mucormycetes. Our results show that human IL-2 prestimulated NK cells damaged all mucormycetes tested. The extent of the damage depended, at least in part, on the growth curve characteristics of the individual fungal isolate. All isolates decreased the secretion of interferon-γ by NK cells to a similar extent. Our data suggest that NK cells damage a wide spectrum of mucormycetes, but that the antifungal effect is higher if NK cells are administered at an early time point of infection.

Immunotherapeutic strategies against mucormycosis in haematopoietic stem cell transplantation.

Mucormycoses remain a serious complication in patients undergoing allogeneic haematopoietic stem cell transplantation (HSCT). In these patients, mortality rates of mucormycosis reach up to 90%, which is due, at least in part, to the severe and prolonged immunosuppression after transplantation. Although prolonged neutropaenia is one of the most important risk factors for mucormycosis, other cell populations, such as CD4(+) T cells may also provide critical defence mechanisms against this infection. The management of mucormycosis includes antifungal therapy, surgery and, most importantly, the control of the underlying predisposing conditions, such as the correction of an impaired immune system. Here, we review the current data of granulocytes, antifungal T cells and natural killer cells regarding their activity against mucormycetes and regarding a potential immunotherapeutic approach. It is hoped that further animal studies and clinical trials assessing immunotherapeutic strategies will ultimately improve the poor prognosis of allogeneic HSCT recipients suffering from mucormycosis.

Immunosuppressive compounds exhibit particular effects on functional properties of human anti-Aspergillus Th1 cells.

Allogeneic hematopoietic stem cell transplant (HSCT) recipients are at high risk for invasive aspergillosis. Whereas adoptive immunotherapy transferring donor-derived anti-Aspergillus TH1 cells has been shown to be beneficial for HSCT recipients suffering from invasive aspergillosis, little is known about the impact of commonly used immunosuppressants on the functional properties of anti-Aspergillus TH1 cells. Anti-Aspergillus TH1 cells were coincubated with different concentrations of methylprednisolone, cyclosporine (CsA), mycophenolic acid (MPA), the active component of mycophenolate mofetil, and rapamycin. Immunosuppressants were tested in concentrations reflecting common target levels in serum and in significantly lower and higher concentrations. Apoptosis of anti-Aspergillus TH1 cells, as well as proliferation and production of gamma interferon (IFN-γ) and CD154 upon restimulation, was evaluated in the presence and absence of immunosuppressive compounds. All dosages of CsA, MPA, and methylprednisolone significantly decreased the number of viable anti-Aspergillus TH1 cells in the cell culture, which was due partly to an impaired proliferative capacity of the cells and partly to an increased rate of apoptosis. In addition, CsA significantly decreased the number of IFN-γ-producing cells and had the highest impact of all immunosuppressants on IFN-γ levels in the supernatant. CsA also significantly decreased the expression of CD154 by anti-Aspergillus TH1 cells. Variant dosages of immunosuppressants exhibit particular effects on essential functional properties of anti-Aspergillus TH1 cells. Our findings may have an important impact on the design of clinical trials evaluating the therapeutic benefit of anti-Aspergillus TH1 cells in allogeneic HSCT recipients suffering from invasive aspergillosis.

Clinical-scale generation of multi-specific anti-fungal T cells targeting Candida, Aspergillus and mucormycetes.

BACKGROUND AIMS: Invasive fungal infections, in particular, infections caused by Candida, Aspergillus and mucormycetes, are a major cause of morbidity and mortality in patients undergoing allogeneic hematopoietic stem cell transplantation. Adoptive transfer of donor-derived anti-fungal T cells shows promise to restore immunity and to offer a cure. Because T cells recognize only specific epitopes, the low rate of patients in which the causal fungal pathogen can be identified and the considerable number of patients with co-infection with several genera or species of fungi significantly limit the application of adoptive immunotherapy. METHODS: Using the interferon-γ secretion assay, we isolated multi-specific human anti-fungal T cells after simultaneous stimulation with cellular extracts of Aspergillus fumigatus, Candida albicans and Rhizopus oryzae. Cells were phenotypically and functionally characterized by flow cytometry. RESULTS: Of a total of 1.1 × 10(9) peripheral blood mononuclear cells, a median number of 5.2 × 10(7) CD3+ CD4+ T cells was generated within 12 days. This cell population consisted of activated memory TH1 cells and reproducibly responded to a multitude of Aspergillus spp., Candida spp. and mucormycetes with interferon-γ production. On re-stimulation, the generated T cells proliferated and enhanced anti-fungal activity of phagocytes and showed reduced alloreactivity compared with the original cell fraction. CONCLUSIONS: Our rapid and simple method of simultaneously generating functionally active multi-specific T cells that recognize a wide variety of medically relevant fungi may form the basis for future clinical trials investigating adoptive immunotherapy in allogeneic hematopoietic stem cell transplantation recipients with invasive fungal infection.

Immunotherapy of invasive fungal infection in hematopoietic stem cell transplant recipients.

Despite the availability of new antifungal compounds, invasive fungal infection remains a significant cause of morbidity and mortality in children and adults undergoing allogeneic hematopoietic stem cell transplantation (HSCT). Allogeneic HSCT recipients suffer from a long lasting defect of different arms of the immune system, which increases the risk for and deteriorates the prognosis of invasive fungal infections. In turn, advances in understanding these immune deficits have resulted in promising strategies to enhance or restore critical immune functions in allogeneic HSCT recipients. Potential approaches include the administration of granulocytes, since neutropenia is the single most important risk factor for invasive fungal infection, and preliminary clinical results suggest a benefit of adoptively transferred donor-derived antifungal T cells. In vitro data and animal studies demonstrate an antifungal effect of natural killer cells, but clinical data are lacking to date. This review summarizes and critically discusses the available data of immunotherapeutic strategies in allogeneic HSCT recipients suffering from invasive fungal infection.

Natural killer cells and antifungal host response.

As a result of improved experimental methodologies and a better understanding of the immune system, there is increasing insight into the antifungal activity of natural killer (NK) cells. Murine and human NK cells are able to damage fungi of different genera and species in vitro, and they exert both direct and indirect antifungal activity through cytotoxic molecules such as perforin and through cytokines and interferons, respectively. On the other hand, recent data suggest that fungi exhibit immunosuppressive effects on NK cells. Whereas clear in vivo data are lacking in humans, the importance of NK cells in the host response against fungi has been demonstrated in animal models. Further knowledge of the interaction of NK cells with fungi might help to better understand the pathogenesis of invasive fungal infections and to improve treatment strategies.

Immunotherapy in invasive fungal infection--focus on invasive aspergillosis.

Despite the availability of new antifungal compounds, morbidity and mortality of invasive aspergillosis are still unacceptably high, in particular in immunocompromised patients such as patients with hematological malignancies or allogeneic hematopoietic stem cell or solid organ transplant recipients. Over the last decades, our knowledge of the immunopathogenesis of invasive aspergillosis has greatly advanced. This, in turn, provided critical information to augment host immunity against fungal pathogens. Potential approaches for enhancing the host immune system in the combat against Aspergillus include the administration of effector and regulatory cells (e.g., granulocytes, antigen-specific T cells, natural killer cells, dendritic cells) as well as the administration of recombinant cytokines, interferons and growth factors (e.g., interferon-γ,granulocyte- and granulocyte-macrophage colony stimulating factor) and various vaccination strategies. Although promising results are reported on in vitro data and animal studies, current data are too limited to allow solid conclusions on the risk and the benefit of these strategies in the clinical setting. Therefore, the real challenge in the future is to perform appropriately designed and powered clinical trials. These require international, multi-center collaboration, but may ultimately improve the outcome in immunocompromised patients suffering from invasive aspergillosis.