Markus Kapp

Dendritic Cell Vaccination in Allogeneic Stem Cell Recipients: Induction of Human Cytomegalovirus (HCMV)—Specific Cytotoxic T Lymphocyte Responses Even in Patients Receiving a Transplant from an HCMV-Seronegative Donor

Vaccination with peptide-loaded dendritic cells (DCs) has been shown to be potent immunostimulatory therapy for the management of serious infections. After allogeneic stem cell transplant (SCT), a prolonged and severe immune deficiency often leads to infectious complications. Human cytomegalovirus (HCMV) infection is one such life-threatening complication after allogeneic SCT. A phase 1/2 study including 24 allogeneic SCT recipients at high risk for HCMV disease was performed to analyze the feasibility and efficacy of vaccination with HCMV peptide-loaded DCs. No acute adverse effects were observed, and a significant clinical benefit could be demonstrated in comparison to our historical control group. An induction or expansion of HCMV-specific cytotoxic T lymphocytes was observed in 5 patients after DC vaccination.

EBV-induced post transplant lymphoproliferative disorders: a persisting challenge in allogeneic hematopoetic SCT

EBV-induced post transplantation lymphoproliferative disorder (EBV-PTLD) is a life-threatening complication after allogeneic hematopoietic cell transplantation. Profound T-cell depletion of the allograft represents a major risk factor for EBV-PTLD. With regard to the increasing use of alternative stem cell sources such as cord blood or purified haploidentical stem cell grafts both associated with impaired immune reconstitution, the frequent occurrence of EBV-PTLD demands particular vigilance on laboratory changes and early symptoms. Here we have summarized today’s knowledge about EBV-PTLD in a comprehensive review explaining the underlying mechanisms of EBV-based transformation, EBV-PTLD development, clinical presentation, incidence, diagnosis, screening, therapy and prognosis. In this context, we emphasize on the necessity of regularly applied screening tools and pre-emptive treatment strategies including anti-CD20 Abs particularly in high-risk patients to avoid disease progression to malignant lymphoma. Although EBV-PTLD has always been associated with a high mortality rate, novel immunotherapeutic approaches such as the transfer of EBV-specific T cells nowadays offer improved chances of disease control even at late stages.

CD8 + T-cell responses to tumor-associated antigens correlate with superior relapse-free survival after allo-SCT

The GVL effect following allo-SCT is one of the most prominent examples showing the ability of the immune system to eliminate malignant hematological diseases. Tumor-associated Ags (TAA), for instance WT1 and proteinase-3, have been proposed as targets for T cells to establish a GVL effect. Here, we examined an additional TAA (MUC1) as a possible T-cell target of GVL-related immune responses. We have defined new peptide epitopes from the MUC1 Ag to broaden patients’ screening and to expand the repertoire of immunologic monitoring as well as for therapeutic approaches in the future. Twenty-eight patients after allo-SCT have been screened for T-cell responses toward TAA (proteinase-3, WT1, MUC1). We could detect a significant relationship between relapse and the absence of a TAA-specific T-cell response, whereby only 2/13 (15%) patients with TAA-specific CTL relapsed, in contrast to 9/15 (60%) patients without TAA-specific CTL responses (P<0.05). In conclusion, CD8+ T-cell responses directed to TAA might contribute to the GVL effect. These observations highlight both the importance and the potential of immunotherapeutic approaches after allo-SCT.

SMAC mimetic BV6 induces cell death in monocytes and maturation of monocyte-derived dendritic cells.

Background Compounds mimicking the inhibitory effect of SMAC / DIABLO on X-linked inhibitor of apoptosis (XIAP) have been developed with the aim to achieve sensitization for apoptosis of tumor cells resistant due to deregulated XIAP expression. It turned out that SMAC mimetics also have complex effects on the NFκB system and TNF signaling. In view of the overwhelming importance of the NFκB transcription factors in the immune system, we analyzed here the effects of the SMAC mimetic BV6 on immune cells. Principal Findings BV6 induced apoptotic and necrotic cell death in monocytes while T-cells, dendritic cells and macrophages were largely protected against BV6-induced cell death. In immature dendritic cells BV6 treatment resulted in moderate activation of the classical NFκB pathway, but it also diminished the stronger NFκB-inducing effect of TNF and CD40L. Despite its inhibitory effect on TNF- and CD40L signaling, BV6 was able to trigger maturation of immature DCs as indicated by upregulation of CD83, CD86 and IL12. Significance The demonstrated effects of SMAC mimetics on immune cells may complicate the development of tumor therapeutic concepts based on these compounds but also arise the possibility to exploit them for the development of immune stimulatory therapies.

Interaction analyses of human monocytes co- cultured with different forms of Aspergillus fumigatus

Monocytes play a major role in the cellular defence against Aspergillus fumigatus in immunocompromised patients. To obtain a better understanding of the mechanisms involved in this interaction, phagocytosis and gene expression profiling of human monocytes was carried out after incubation with A. fumigatus resting, swollen and germinating conidia and hyphae (for 3, 6 and 9 h). The majority of monocytes phagocytosed up to three conidia during the first 3 h of incubation. Microarray analysis showed an increased expression level of immune-relevant genes, which was dependent on the germination state of the fungus and the incubation period. Among these genes, those encoding interleukin-8, macrophage inflammatory protein 3-alpha (CCL20) and monocyte chemotactic protein-1 (CCL2) were found to be potential key regulators involved in the A. fumigatus-induced immune response. In addition, A. fumigatus was found to be an inducer of the genes encoding urokinase type plasminogen activator (uPA), urokinase type plasminogen activator receptor (uPAR),plasminogen activator inhibitor (PAI), pentraxin-3 (PTX3) and intercellular adhesion molecule-1 (ICAM-1), which, in combination, may contribute to thrombosis and local lung tissue injury.

Adoptive immunotherapy with virus-specific T cells

Viral infections are still common causes of morbidity and mortality in immunosuppressed patients after allogeneic hematopoietic stem cell transplantation. Infections caused by virus such as cytomegalovirus, adenovirus and Epstein-Barr virus are well-known. In addition, several other viruses such as polyomavirus and human herpesvirus 6 have been recently reported to be causes of significant complications. As the delay in recovery of virus-specific cellular immune response after transplant is associated with viral reactivation and viral disease, adoptive immunotherapy to restore virus-specific cellular immunity is an attractive option. Recent clinical trials showed the safety and effectiveness of adoptive immunotherapy against viral diseases. In this review, we summarize the current status of adoptive immunotherapy against several viral diseases including cytomegalovirus, adenovirus, Epstein-Barr virus and polyomavirus.

Adoptive immunotherapy of HCMV infection

Human cytomegalovirus (HCMV) infection or reactivation is a frequent cause of morbidity and mortality in immunocompromised individuals such as transplant recipients. Primary HCMV infection or reactivation of HCMV from latency is mostly asymptomatic in immunocompetent individuals and is controlled by the hosts cell-mediated immune response. Healthy HCMV seropositive individuals develop high frequencies of HCMV-specific cytotoxic T lymphocytes (CTL) in the peripheral blood. Furthermore, a direct correlation between the recovery of HCMV-specific CTL responses and an improved outcome of HCMV disease could be demonstrated in immunocompromised patients. Deriving from these observations, the strategy of an adoptive transfer of HCMV-specific T cells has been developed. Protective immunity can be transferred successfully by the infusion of donor-derived HCMV-specific CD8+ cytotoxic T-cell clones or cell lines. In addition, several studies have supported the importance of antiviral effector functions of Th cells in maintaining CTL responses after adoptive transfer and their capacity to produce antiviral cytokines. Until today, a broad variety of clinical protocols for HCMV-specific immunotherapy has been published. These protocols vary regarding the isolation procedure, composition of cellular product, number of transferred cells and thus treatment efficacy. In this review, we aim to provide a comprehensive synopsis of the current standard of knowledge concerning cellular HCMV-specific immunotherapeutic approaches.

Uptake of antigens from modified vaccinia Ankara virus-infected leukocytes enhances the immunostimulatory capacity of dendritic cells

BACKGROUND AIMS Modified vaccinia Ankara (MVA) is a promising vaccine vector for infectious diseases and malignancies. It is fundamental to ascertain its tropism in human leukocyte populations and immunostimulatory mechanisms for application in immunotherapy. METHODS Human peripheral blood mononuclear cells (PBMC) and leukocyte subpopulations [monocyte-derived dendritic cells (DC), monocytes and B cells] were infected with MVA in order to evaluate their infection rate, changes in surface markers, cytokine expression and apoptosis. RESULTS Monocytes, DC and B cells were most susceptible to MVA infection, followed by natural killer (NK) cells. Monocytes were activated strongly, with upregulation of co-stimulatory molecules, major histocompatibility complex (MHC) molecules and chemokine (C-C motif) receptor (CCR7), while immature DC showed partial activation and B cells were inhibited. Furthermore, expression of chemokine (C-X-C motif) ligand (CXCL10), tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-12p70 was enhanced but IL-1β and IL-10 were stable or even downregulated. MVA induced a high apoptosis rate of antigen-presenting cells (APC). Nevertheless, incubation of MVA-infected leukocytes with uninfected immature DC (iDC) led to complete maturation of the DC. Subsequently, the matured DC were able to stimulate cytomegalovirus (CMV)-immediate early protein (IE1)-specific T cells. CONCLUSIONS MVA induces a T-helper (Th)-1-polarizing cytokine expression in APC. Furthermore, incubation of MVA-infected leukocytes with uninfected iDC leads to complete maturation of the DC and may be the basis for cross-presentation of MVA-encoded antigens. Thus this approach seems to be an ideal model for further studies with MVA-encoded viral antigens regarding immunotherapy and vaccination strategies.

Pathogen specific T-lymphocytes for the reconstitution of the immunocompromised host

Cellular immune functions are impaired in hemopoietic stem cell and solid organ transplantation or in cancer and autoimmune diseases treated with intensified immunosuppression. Thus, control of opportunistic pathogens is lost and severe infections break out. Defective cellular immunity can be restored upon endogenous immunoreconstitution or, if delayed, exogenous immunoreconstitution with pathogen specific T-lymphocytes selected or expanded from appropriate donors can be applied. Here we describe how recent developments in basic immunology knowledge and techniques have accelerated progresses of clinical trials in this attractive field. In particular, methods for the identification of appropriate antigens, for selection and expansion of specific T-cells and for safer manipulation of cellular products have been applied with promising advances. Finally, the development of biobanks of specific T-cells is described as an attractive perspective to reconstruct pathogen specific cellular immunity.

Systematic Nutritional Support in Allogeneic Hematopoietic Stem Cell Transplant Recipients.

Allogeneic hematopoietic stem cell transplantation (HSCT) has become an established treatment modality for various hematological diseases. However, in allogeneic HSCT, patients often suffer from severe gastrointestinal complications caused by the conditioning regimen and acute/chronic graft-versus-host disease, which requires support by multidisciplinary nutritional support teams (NST). In addition, pretransplantation nutritional status can affect the clinical outcome after allogeneic HSCT. Therefore, it is important to refer the patient to a NST when becoming aware of nutritional problems before allogeneic HSCT. It is also important to follow nutritional status over the long term, as patients often suffer from various nutritional problems, such as malnutrition and metabolic syndrome, even late after allogeneic HSCT. In summary, NST can contribute to the improvement of nutritional status and possibly prognosis at every stage before and after allogeneic HSCT. Here, we aim to give a comprehensive overview of current understanding about nutritional support in allogeneic HSCT and try to provoke a constructive discussion to stimulate further investigation.