Annika Erbacher

Publications (6)22.92 Total impact

• Article: Analysis of posaconazole as oral antifungal prophylaxis in pediatric patients under 12 years of age following allogeneic stem cell transplantation.

  Michaela Döring, Carsten Müller, Pascal-David Johann, Annika Erbacher, Astrid Kimmig, Carl-Philipp Schwarze, Peter Lang, Rupert Handgretinger, Ingo Müller
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  ABSTRACT: BACKGROUND: Pediatric patients undergoing hematopoietic stem cell transplantation (HSCT) are at high risk of acquiring fungal infections. Antifungal prophylaxis shortly after transplantation is therefore indicated, but data for pediatric patients under 12 years of age are scarce. To address this issue, we retrospectively assessed the safety, feasibility, and initial efficacy of prophylactic posaconazole in children. METHODS: 60 consecutive pediatric patients with a median age of 6.0 years who underwent allogeneic HSCT between August 2007 and July 2010 received antifungal prophylaxis with posaconazole in the outpatient setting. 28 pediatric patients received an oral suspension at 5 mg/kg body weight b.i.d., and 32 pediatric patients received the suspension at 4 mg/kg body weight t.i.d. . The observation period lasted from start of treatment with posaconazole until its termination (maximum of 200 days post-transplant). RESULTS: Pediatric patients who received posaconazole at 4 mg/kg body weight t.i.d. had a median trough level of 383 mug/L. Patients who received posaconazole at 5 mg/kg body weight b.i.d. had a median trough level of 134 mug/L. Both regimens were well tolerated without severe side effects. In addition, no proven or probable invasive mycosis was observed. CONCLUSION: Posaconazole was a well-tolerated, safe, and effective oral antifungal prophylaxis in pediatric patients who underwent high-dose chemotherapy and HSCT. Posaconazole at a dosage of 12 mg/kg body weight divided in three doses produced consistently higher morning trough levels than in patients who received posaconazole 5 mg/kg body weight b.i.d. . Larger prospective trials are needed to obtain reliable guidelines for antifungal prophylaxis in children after HSCT.
  BMC Infectious Diseases 10/2012; 12(1):263. · 3.12 Impact Factor
• Article: Caspofungin as antifungal prophylaxis in pediatric patients undergoing allogeneic hematopoietic stem cell transplantation: a retrospective analysis.

  Michaela Döring, Ulrike Hartmann, Annika Erbacher, Peter Lang, Rupert Handgretinger, Ingo Müller
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  ABSTRACT: Pediatric patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) often receive intravenous liposomal amphotericin B (L-AmB) as antifungal prophylaxis. There are no guidelines for antifungal prophylaxis in children in this situation. Caspofungin (CAS), a broad-spectrum echinocandin, could be an effective alternative with lower nephrotoxicity than L-AmB. We retrospectively analyzed the safety, feasibility, and efficacy of CAS in our center, and compared the results with L-AmB as antifungal monoprophylaxis in pediatric patients undergoing HSCT. 60 pediatric patients received L-AmB (1 or 3 mg/kg bw/day) and another 60 patients received CAS (50 mg/m2/day) as antifungal monoprophylaxis starting on day one after HSCT. The median ages of patients receiving L-AmB and CAS were 7.5 years and 9.5 years, respectively. No proven breakthrough fungal infection occurred in either group during the median treatment period of 23 days in the L-AmB group and 24 days in the CAS group. One patient receiving CAS developed probable invasive aspergillosis. During L-AmB treatment, potassium levels significantly decreased below normal values. Patients treated with L-AmB had more drug-related side effects and an increased need for oral supplementation with potassium, sodium bicarbonate and calcium upon discharge as compared with the CAS group. CAS was well-tolerated and safe in this cohort of immunocompromised pediatric patients, who underwent high-dose chemotherapy and HSCT. Prophylactic CAS and L-AmB showed similar efficacy in this biggest cohort of pediatric patients after allogeneic HSCT reported, so far. A prospective randomized trial in children is warranted to allow for standardized guidelines.
  BMC Infectious Diseases 07/2012; 12:151. · 3.12 Impact Factor
• Article: Siglec-7 tetramers characterize B-cell subpopulations and leukemic blasts.

  Friederike Gieseke, Philippa Mang, Susanne Viebahn, Inga Sonntag, Anne Kruchen, Annika Erbacher, Matthias Pfeiffer, Rupert Handgretinger, Ingo Müller
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  ABSTRACT: Cell surface glycosylation has important regulatory functions in the maturation, activation, and homeostasis of lymphocytes. The family of human sialic acid-binding immunoglobulin-like lectins (siglecs) comprises inhibitory as well as activating receptors intimately involved in the regulation of immune responses. Analyses of the interaction between siglecs and glycans are hampered by the low affinity of this interaction. Therefore, we expressed siglec-7 in eukaryotic cells, allowing for glycosylation, and oligomerized the protein in analogy to MHC tetramers. Using this tool, flow cytometric analysis of lymphocytes became possible. Sialic acid-dependent binding of siglec-7 tetramers was confirmed by glycan array analysis and loss of siglec tetramer binding after neuraminidase treatment of lymphocytes. In contrast to most lymphocyte subpopulations, which showed high siglec-7 ligand expression, B-cell subpopulations could be further subdivided according to different siglec-7 ligand expression levels. We also analyzed blasts from acute lymphoblastic leukemias of the B-cell lineage as well as the T-cell lineage, since malignant transformation is often associated with aberrant cell surface glycosylation. While pediatric T-ALL blasts highly expressed siglec-7 ligands, siglec-7 ligands were barely detectable on cALL blasts. Taken together, oligomerization of recombinant soluble siglec-7 enabled flow cytometric identification of physiologic lymphocyte subpopulations and malignant blasts.
  European Journal of Immunology 05/2012; 42(8):2176-86. · 5.10 Impact Factor
• Article: Long-term human CD34+ stem cell-engrafted nonobese diabetic/SCID/IL-2R gamma(null) mice show impaired CD8+ T cell maintenance and a functional arrest of immature NK cells.

  Maya C André, Annika Erbacher, Christian Gille, Vanessa Schmauke, Barbara Goecke, Alexander Hohberger, Philippa Mang, Ayline Wilhelm, Ingo Mueller, Wolfgang Herr, Peter Lang, Rupert Handgretinger, Udo F Hartwig
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  ABSTRACT: Allogeneic hematopoietic stem cell transplantation represents the most effective form of immunotherapy for chemorefractory diseases. However, animal models have been missing that allow evaluation of donor-patient-specific graft-versus-leukemia effects. Thus, we sought to establish a patient-tailored humanized mouse model that would result in long-term engraftment of various lymphocytic lineages and would serve as a donor-specific surrogate. Following transfer of donor-derived peripheral blood stem cells into NOD/SCID/IL-2Rgamma(null) (NSG) mice with supplementation of human IL-7, we could demonstrate robust engraftment and multilineage differentiation comparable to earlier studies using cord blood stem cells. Phenotypical and functional analyses of lymphoid lineages revealed that >20 wk posthematopoietic stem cell transplantation, the majority of T lymphocytes consisted of memory-type CD4(+) T cells capable of inducing specific immune functions, whereas CD8(+) T cells were only present in low numbers. Analysis of NSG-derived NK cells revealed the expression of constitutively activated CD56(bright)CD16(-) killer Ig-like receptor(negative) NK cells that exhibited functional impairments. Thus, the data presented in this study demonstrate that humanized NSG mice can be successfully used to develop a xenotransplantation model that might allow patient-tailored treatment strategies in the future, but also highlight the need to improve this model, for example, by coadministration of differentiation-promoting cytokines and induction of human MHC molecules to complement existing deficiencies in NK and CD8(+) T cell development.
  The Journal of Immunology 09/2010; 185(5):2710-20. · 5.79 Impact Factor
• Article: Helminth infection with Litomosoides sigmodontis induces regulatory T cells and inhibits allergic sensitization, airway inflammation, and hyperreactivity in a murine asthma model.

  Anna M Dittrich, Annika Erbacher, Sabine Specht, Felix Diesner, Martin Krokowski, Angela Avagyan, Philippe Stock, Birgit Ahrens, Wolfgang H Hoffmann, Achim Hoerauf, Eckard Hamelmann
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  ABSTRACT: Numerous epidemiological studies have shown an inverse correlation between helminth infections and the manifestation of atopic diseases, yet the immunological mechanisms governing this phenomenon are indistinct. We therefore investigated the effects of infection with the filarial parasite Litomosoides sigmodontis on allergen-induced immune reactions and airway disease in a murine model of asthma. Infection with L. sigmodontis suppressed all aspects of the asthmatic phenotype: Ag-specific Ig production, airway reactivity to inhaled methacholine, and pulmonary eosinophilia. Similarly, Ag-specific recall proliferation and overall Th2 cytokine (IL-4, IL-5, and IL-3) production were significantly reduced after L. sigmodontis infection. Analysis of splenic mononuclear cells and mediastinal lymph nodes revealed a significant increase in the numbers of T cells with a regulatory phenotype in infected and sensitized mice compared with sensitized controls. Additionally, surface and intracellular staining for TGF-beta on splenic CD4(+) T cells as well as Ag-specific TGF-beta secretion by splenic mononuclear cells was increased in infected and sensitized animals. Administration of Abs blocking TGF-beta or depleting regulatory T cells in infected animals before allergen sensitization and challenges reversed the suppressive effect with regard to airway hyperreactivity, but did not affect airway inflammation. Despite the dissociate results of the blocking experiments, these data point toward an induction of regulatory T cells and enhanced secretion of the immunomodulatory cytokine TGF-beta as one principle mechanism. In conclusion, our data support the epidemiological evidence and enhance the immunological understanding concerning the impact of helminth infections on atopic diseases thus providing new insights for the development of future studies.
  The Journal of Immunology 03/2008; 180(3):1792-9. · 5.79 Impact Factor
• Article: Dendritic cells: Functional aspects of glycosylation and lectins

  Annika Erbacher, Friederike Gieseke, Rupert Handgretinger, Ingo Müller
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  ABSTRACT: Dendritic cells (DC) direct immune responses either toward tolerance to a presented antigen or toward inflammatory reactions of effector cells. Many crucial cytokines and cell surface proteins have been identified in this process using gene expression profiling. However, it is becoming evident that important steps involve carbohydrate–protein interactions, which cannot be anticipated by gene expression profiling in most cases. These contacts are crucial for the uptake of certain antigens, migration, and homing, but also for infection by viruses. On one hand, DC use numerous C-type lectins, such as DC-SIGN, dectin-1, langerin, and DEC-205, for antigen uptake. Other lectins, such as CD83, siglecs, and galectins, may be involved in regulation of the immune response to a given antigen. On the other hand, cell surface glycosylation of DC themselves changes significantly depending on the environment and the functional state, generating different signals by altered glycans. Because DC occur at the interface between innate and acquired immunity, it may not be surprising that glycans and lectins play an important role in many biological functions of DC. In this review, we focus on glycobiological aspects of antigen uptake and processing, immune modulation, and viral infections in the context of DC biology.
  Human Immunology.