Biomedical subjects

Peter Reinhardt

Publications and source records attributed to Peter Reinhardt.

6 recordsLinked to original sources

PubMed2006

Towards a force field based on density fitting.

Total intermolecular interaction energies are determined with a first version of the Gaussian electrostatic model (GEM-0), a force field based on a density fitting approach using s-type Gaussian functions. The total interaction energy is computed in the spirit of the sum of interacting fragment ab initio (SIBFA) force field by separately evaluating each one of its components: electrostatic (Coulomb), exchange repulsion, polarization, and charge transfer intermolecular interaction energies, in order to reproduce reference constrained space orbital variation (CSOV) energy decomposition calculations at the B3LYP/aug-cc-pVTZ level. The use of an auxiliary basis set restricted to spherical Gaussian functions facilitates the rotation of the fitted densities of rigid fragments and enables a fast and accurate density fitting evaluation of Coulomb and exchange-repulsion energy, the latter using the overlap model introduced by Wheatley and Price [Mol. Phys. 69, 50718 (1990)]. The SIBFA energy scheme for polarization and charge transfer has been implemented using the electric fields and electrostatic potentials generated by the fitted densities. GEM-0 has been tested on ten stationary points of the water dimer potential energy surface and on three water clusters (n = 16,20,64). The results show very good agreement with density functional theory calculations, reproducing the individual CSOV energy contributions for a given interaction as well as the B3LYP total interaction energies with errors below kBT at room temperature. Preliminary results for Coulomb and exchange-repulsion energies of metal cation complexes and coupled cluster singles doubles electron densities are discussed.

Algorithms↗

PubMed2006

Immunotherapy for patients with acute myeloid leukemia using autologous dendritic cells generated from leukemic blasts.

Vaccination with dendritic cells (DCs) as professional antigen presenting cells generated from autologous leukemic blasts might elicit anti-leukemic T cell responses in patients with acute myeloid leukemia (AML). To test this hypothesis, autologous AML-DC were generated under good manufacturing practice (GMP) conditions and injected s.c. into five AML patients up to four times at a biweekly interval. No severe adverse side effects were observed. Three patients remained in a stable condition for 5.5-13 months and two patients died from rapidly progressive AML. Compared to the initial T cell frequency, enzyme linked immunosorbent spot (ELISPOT) assays revealed a significant increase of granzyme B releasing CD8+ T cells specifically recognizing the PRAME derived peptide (ALYVDSLFFL), a leukemia associated antigen expressed by AML blasts. The cytokine levels in the serum of vaccination AML patients as assessed by cytokine bead assay changed over the period of vaccination to an elevated type 1 T helper cell pattern. Interferon gamma production by CD4+ T helper cells increased during vaccination. In summary, we demonstrated that autologous AML-DC vaccination is well tolerated and can result in an enhanced and specific response of cytotoxic T cells in AML patients.

Acute Disease↗

PubMed2005

Trifunctional bispecific antibody-induced tumor cell lysis of squamous cell carcinomas of the upper aerodigestive tract.

BACKGROUND: The trifunctional bispecific antibody Removab (tbAB) bridges and activates CD3 positive T cells to EpCAM on carcinoma cells and simultaneously binds to an accessory immune-cell inducing tumor cell lysis. tbAB-induced tumor cytotoxicity was assessed in an autologous human ex vivo system. METHODS: One hundred forty tumor samples and autologous peripheral blood mononuclear cells from a total of 36 patients with head and neck squamous cell carcinomas (HNSCCs) were incubated on a chicken embryo chorioallantois membrane with Removab. Tumor cells coincubated with cisplatin or cell culture medium served as positive and negative controls. Tumor cell lysis was assessed by acridine orange staining or by fluorescence-activated cell sorting of propidium iodide-marked cells after 24 and 48 hours (T24/T48) coincubation. RESULTS: Coincubation of HNSCC cells with tbAB and autologous peripheral blood mononuclear cells resulted in a 49% +/- 6% decrease of viable cells at T24 (p < .005) and in a decrease of 56% +/- 8% at T48 (p < .005) compared with the control. The tumor cytotoxicity was similar to that of cisplatin (49% +/- 7% decrease at T24 and 49% +/- 8% at T48). CONCLUSION: In an autologous human ex vivo system, the tbAB-induced tumor cell lysis was comparable to that by cisplatin.

Antibodies, Bispecific↗

PubMed2004

Dendritic cells generated from acute myeloid leukemia (AML) blasts maintain the expression of immunogenic leukemia associated antigens.

Recently, the focus is on new specific immunotherapies for AML such as cellular therapies employing dendritic cells (DCs) generated from AML blasts. AML-DCs express constitutionally leukemia-associated antigens (LAAs) present in AML blasts they are generated from. Here we investigated whether the generation of AML-DCs would alter the expression level of LAAs. Moreover, we evaluated the presence of HLA and costimulatory molecules on AML blasts versus AML-DCs. Quantitative real-time polymerase chain reaction (PCR) was performed for the following LAAs: preferentially expressed antigen in melanoma (PRAME), the receptor for hyaluronic acid mediated motility (RHAMM/CD168), Wilms' tumor gene 1 (WT-1) and proteinase 3. The expression of HLA-ABC, HLA-DR, CD40, CD80, CD83 and CD86 was evaluated by flow cytometry. RHAMM protein expression was evaluated by immunocytochemistry, recognition of AML-DCs by PRAME epitope-specific T cells was evaluated in a chromium-release assay. Quantitative real-time PCR for AML-DCs versus AML blasts showed an alteration in mRNA expression of LAAs. An elevated PCR signal for PRAME was detected in 7/12 AML-DC preparations. 6/12 AML-DC preparations showed a significant upregulation of the PCR signal for RHAMM. A stronger WT-1 and proteinase-3 signal was observed in PCR for only 2/12 and 1/12 AML-DCs , respectively. All preparations showed a strong expression of at least one of the LAAs examined. As demonstrated by flow cytometry, AML-DCs strongly upregulated costimulatory molecules like CD40 and CD80 in comparison with AML blasts. AML-DCs tested positive for RHAMM protein. PRAME positive AML-DCs were recognized by specific T cells. AML-DCs might constitute a powerful tool in immunotherapy for AML. Real-time PCR allows a quick and quantitative assessment of immunologically relevant LAA expression with only 10(5) DCs and might be helpful for the decision whether the AML-DC vaccination strategy is favourable or not.

Acute Disease↗

PubMed2003

Reconstitution of CD40 and CD80 in dendritic cells generated from blasts of patients with acute myeloid leukemia.

Acute myeloid leukemia (AML) is a clonal disease of hematopoiesis with poor clinical outcome despite recent improvements in chemotherapy and stem cell transplantation regimens. Immunotherapy with dendritic cells (DCs) eliciting specific T cell responses to leukemia-associated antigens (LAAs) might be a therapeutic option. DCs must express HLA class I/II molecules and the costimulatory molecules CD40, CD80 and CD86 to effectively activate T cells for the subsequent lysis of leukemic blasts. The expression of these antigens on DCs generated from 15 AML patients (AML-DCs) and on DCs generated from 15 healthy volunteers (HV-DCs) was analyzed by FACS. All DCs displayed the typical morphology and tested negative for B, T and NK cell markers. The sustained mRNA expression of LAAs such as PRAME, RHAMM or WT-1 proved that the AML-DCs originated from AML blasts. Compared with AML blasts, the expression of CD40, CD80, CD86 and HLA-DR was upregulated during DC culture to a median of 80-98% on AML-DCs. HLA-ABC was preserved on AML-DCs (median 95%). Expression of CD40, CD80 and CD83 remained lower on AML-DCs than on HV-DCs. AML-DCs express at least one LAA and strongly express HLA and costimulatory molecules, the prerequisites for eliciting T cell responses. AML-DCs may play a role in vaccine-based immunotherapies for AML patients.

Acute Disease↗

PubMed2003

Expression of human leucocyte antigens and co-stimulatory molecules on blasts of patients with acute myeloid leukaemia.

Recently, leukaemia-associated antigens (LAA) recognized by T lymphocytes, such as Wilm's tumour-1 (WT-1) or pathogenesis-related protein-1 (PR-1), have been identified. For immunotherapies that employ antigen peptides, either alone or pulsed on dendritic cells (DC), the expression of human leucocyte antigen (HLA) molecules on the targeted leukaemic blasts (LB) is crucial. The co-stimulatory molecules CD80 and CD86 give the secondary signal to T lymphocytes that is necessary for the lysis of leukaemia cells, and CD40 enhances the efficacy of antigen presentation. Here, the expression of HLA-ABC, HLA-A2, HLA-DR, CD40, CD80 and CD86 was flow cytometrically examined in blood samples from 24 healthy volunteers (HV), 24 patients with newly diagnosed acute myeloid leukaemia (AML) and five patients with relapsed AML. The expression of HLA-ABC, CD40, CD80 and CD86 was significantly reduced on LB in comparison with monocytes of HV. HLA-A2 and HLA-DR expression was similar on LB and on monocytes of HV. In AML patients, the expression of HLA and CD86 molecules was significantly higher on LB than on CD33/CD34-negative monocytes. CD40 and CD80 molecules were deficient on AML blasts. The preservation of HLA molecules and CD86 on LB of the majority of AML patients at the time of diagnosis and even at relapse of the disease are prerequisites for LAA-targeted immunotherapies in these patients.

Acute Disease↗