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H Waldmann

Publications and source records attributed to H Waldmann.

At least 109 records · Page 6Linked to original sources
PubMed1999

Anti-adhesion molecule therapy as an interventional strategy for autoimmune inflammation.

Functional inactivation of leukocyte adhesion molecules has been used to intervene in the development of tissue injury in experimental models of postperfusion infarction as well as autoimmune inflammation. We investigated the use of humanized monoclonal antibodies (mAb) against CD18 in the treatment of five patients with vasculitic tissue injury sufficient to threaten infarction or gangrene. The treatment was monitored in three ways: (i) whole-body gamma camera scintiscanning of autologous indium-labeled PMN, (ii) an index of the therapeutic inhibition of adhesion derived from comparison pre, during, and post mAb treatment of the ability of patients' PMN to be aggregated after activation by fMLP, and (iii) flow cytometric analysis of PMN CD18 expression. Four of five patients given anti-CD18 at 20 mg/day for up to 3 weeks showed prompt clinical improvement, with healing of the ulceration and restoration of limb function within 4 weeks, which was sustained. The fifth patient, who was not doing well clinically, decided to withdraw from all active treatment: at autopsy there was no evidence of the underlying vasculitis evident pretreatment. Our findings suggest that anti-adhesion molecule treatment might be an effective immediate treatment in severe vasculitis especially when tissue viability is threatened by progressive infarction and/or development of gangrene.

Aged↗
PubMed1999

Dominant regulation: a common mechanism of monoclonal antibody induced tolerance?

Transplantation tolerance can be induced by a range of agents that block T cell/antigen-presenting cell (APC) interactions known to be important for initiation of the adaptive immune response. Tolerance so induced has been shown to have a regulatory phenotype dependent on CD4+ cells. This was first observed with nonlytic anti-CD4 antibodies, and was recently demonstrated following other therapeutic approaches. Dominant tolerance also plays a role in natural regulation of the immune response, functioning to prevent autoaggressive cells mediating self-destruction. The mechanism by which dominant tolerance is established and maintained remains unclear, and the reported characteristics of regulatory cells in different experimental models vary widely. Here we review the evidence for potential mechanisms involved and propose that there is a common pathway by which dominant tolerance is mediated.

Antibodies, Monoclonal↗
PubMed1999

Engraftment of marrow allografts treated with Campath-1 monoclonal antibodies.

We have analyzed the factors associated with engraftment in 216 recipients of T-cell depleted allogeneic HLA identical sibling marrow transplants using Campath 1 monoclonal antihuman lymphocyte (CD52) antibodies. The patient population consisted of 168 patients with hematologic malignancies, 26 with severe aplastic anemia (SAA), and 22 with hemoglobinopathies, half of whom received marrow treated in vitro with Campath-1M (IgM) and half received marrow with Campath-1G (IgG2b isotype). Patients with durable engraftment had fast hematopoietic recovery: SAA patients reached ANC > 0.5 x 10(6)/L on Day 14; those with leukemia attained ANC > 0.5 x 10(6)/L on Days 18, 17, and 15 for ANLL, ALL and CML respectively, while patients with thalasemia reached ANC > 0.5 x 10(6)/L on Day 21. Overall, 24 patients (17 with leukemia, 4 with SAA, and 3 with thalassemia) suffered graft failure: 10 patients (all grafted with Campath-1M) rejected their grafts, while 14 others (9 grafted with Campath-1M, and 5 with 1G isotype) never engrafted (p = 0.009). Multivariate analysis revealed that neither pretransplant protocol, nor stage of disease or type of antibody used, donor sex and ABO match had any impact on engraftment. The variables favorably associated with engraftment were older age (p = 0.030, RR = 1.016) and CFU-GM number (p = 0.013, RR = 1.001). Patients with ANLL or SAA had a better chance to engraft (p = 0.027, RR = 1.400; and p = 0.003, RR = 2.677, respectively) compared to patients with thalassemia (p = 0.001, RR = 0.551). A higher concentration of Campath-1 antibody in vitro and in vivo adversely affected engraftment. Our data show that satisfactory engraftment can be achieved in patients transplanted with Campath-1 treated marrow allografts. However, despite the measures undertaken to prevent rejection, graft failure still poses a problem. Further pretransplant immunosuppression and perhaps more selective T-cell depletion may reduce the increased graft failure in these patients.

ABO Blood-Group System↗
PubMed1999

Peptide conjugates as tools for the study of biological signal transduction.

Today, many biological phenomena are being investigated and understood in molecular detail, and organic chemistry is increasingly being directed towards biological phenomena. This review is intended to highlight this interplay of organic chemistry and biology, using biological signal transduction as an example. Lipo-, glyco-, phospho- and nucleoproteins play key roles in the processes whereby chemical signals are passed across cell membranes and further to the cell nucleus. For the study of the biological phenomena associated with these protein conjugates, structurally well-defined peptides containing the characteristic linkage region of the peptide backbone with the lipid, the carbohydrate or the phosphoric acid ester can provide valuable tools. The multi-functionality and pronounced acid- and base-lability of such compounds renders their synthesis a formidable challenge to conventional organic synthesis. However, the recent development of enzymatic protecting groups, provides one of the central techniques which, when coupled with classic chemical synthesis, can provide access to these complex and sensitive biologically relevant peptide conjugates under particularly mild conditions and with high selectivity.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1999

Synthesis of the palmitoylated and prenylated C-terminal lipopeptides of the human R- and N-Ras proteins.

For the study of biological phenomena influenced by the R- and N-Ras proteins, characteristic peptides which embody the correct lipid modifications of their parent proteins (palmitoyl thioesters, geranylgeranyl thioethers, and farnesyl thioethers), as well as analogues thereof, may serve as efficient tools. For the construction of such acid- and base labile peptide conjugates the allyl ester was developed as C-terminal protecting group. Allyl esters are cleaved selectively and in high yields from lipidated peptides by Pd(0)-mediated allyl transfer to accepting N- or C-nucleophiles like morpholine and N,N'-dimethylbarbituric acid. This protecting group technique formed the key step in the synthesis of the characteristic S-palmitoylated and S-isoprenylated C-terminus of human R-Ras and human N-Ras proteins, as well as several analogues thereof. Deprotections are so mild that no undesired side reactions of the lipid conjugates are observed.

Humans↗
PubMed1999

Transplantation tolerance-where do we stand?

Our understanding of tolerance mechanisms has progressed to the point that tolerance-induction protocols are being tested in humans for organ transplantation. However, a range of scientific, ethical, logistic and commercial issues have arisen, and must be resolved before tolerance induction for human allograft patients can become a reality.

Adaptation, Physiological↗
PubMed1999

Activated polyamidoamine dendrimers, a non-viral vector for gene transfer to the corneal endothelium.

We investigated the efficiency of activated polyamidoamine dendrimers, a new class of nonviral vectors, to transfect rabbit and human corneas in ex vivo culture. In addition to assessing the expression of a marker gene we have demonstrated that this approach can be used to induce the production of TNF receptor fusion protein (TNFR-Ig), a protein with therapeutic potential. Whole thickness rabbit or human corneas were transfected ex vivo with complexes consisting of dendrimers and plasmids containing lacZ or TNFR-Ig genes. Following optimisation 6-10% of the corneal endothelial cells expressed the marker gene. Expression was restricted to the endothelium and was maximal after transfection with 18:1 (w/w) activated dendrimer:plasmid DNA ratio and culture for 3 days. The supernatant of corneas transfected with TNFR-Ig plasmid contained TNFR-Ig protein which was able to inhibit TNF-mediated cytotoxicity in a bioassay. We have therefore shown that activated dendrimers are an efficient nonviral vector capable of transducing corneal endothelial cells ex vivo. They may have applications in gene-based approaches aimed at prevention of corneal allograft rejection or in treatment of other disorders of corneal endothelium.

Animals↗
PubMed1999

Farnesylation of Ras is important for the interaction with phosphoinositide 3-kinase gamma.

The correct functioning of Ras proteins requires post-translational modification of the GTP hydrolases (GTPases). These modifications provide hydrophobic moieties that lead to the attachment of Ras to the inner side of the plasma membrane. In this study we investigated the role of Ras processing in the interaction with various putative Ras-effector proteins. We describe a specific, GTP-independent interaction between post-translationally modified Ha- and Ki-Ras4B and the G-protein responsive phosphoinositide 3-kinase p110gamma. Our data demonstrate that post-translational processing increases markedly the binding of Ras to p110gamma in vitro and in Sf9 cells, whereas the interaction with p110alpha is unaffected under the same conditions. Using in vitro farnesylated Ras, we show that farnesylation of Ras is sufficient to produce this effect. The complex of p110gamma and farnesylated RasGTP exhibits a reduced dissociation rate leading to the efficient shielding of the GTPase from GTPase activating protein (GAP) action. Moreover, Ras processing affects the dissociation rate of the RasGTP complex with the Ras binding domain (RBD) of Raf-1, indicating that processing induces alterations in the conformation of RasGTP. The results suggest a direct interaction between a moiety present only on fully processed or farnesylated Ras and the putative target protein p110gamma.

Animals↗
PubMed1998

Improving the outcome of bone marrow transplantation by using CD52 monoclonal antibodies to prevent graft-versus-host disease and graft rejection.

Graft-versus-host disease (GVHD) is a major cause of mortality and morbidity after allogeneic bone marrow transplantation, but can be avoided by removing T lymphocytes from the donor bone marrow. However, T-cell depletion increases the risk of graft rejection. This study examined the use of CD52 monoclonal antibodies to eliminate T cells from both donor marrow and recipient to prevent both GVHD and rejection. Seventy patients receiving HLA-identical sibling transplants for acute myelogenous leukemia (AML) in first remission were studied. An IgM (CAMPATH-1M) was used for in vitro depletion of the graft and an IgG (CAMPATH-1G) for in vivo depletion of the recipient before graft infusion. No posttransplant immunosuppression was given. Results were compared with two control groups: (1) 50 patients who received bone marrow depleted with CAMPATH-1M, but no CAMPATH-1G in vivo; and (2) 459 patients reported to the International Bone Marrow Transplant Registry (IBMTR) who received nondepleted grafts and conventional GVHD prophylaxis with cyclosporin A (CyA) and methotrexate (MTX). The incidence of acute GVHD was 4% in the treatment group compared with 35% in the CyA/MTX group (P <.001). Chronic GVHD was also exceptionally low in the treatment group (3% v 36%; P <.001). The problem of graft rejection, which had been frequent in the historic CAMPATH-1M group (31%), was largely overcome in the treatment group (6%). Thus, transplant-related mortality of the treatment group (15% at 5 years) was lower than for the CyA/MTX group (26%; P =.04). There was little difference in the risk of leukemia relapse between the treatment group (30% at 5 years) and the CyA/MTX group (29%). Survival of the treatment group at 6 months was better than the CyA/MTX group (92% v 78%), although at 5 years the difference was not significant (62% v 58%) and neither was the difference in leukemia-free survival (60% v 52%). We conclude that T-cell depletion is a useful strategy to prevent GVHD, provided that measures are taken to ensure engraftment. Using CAMPATH-1G to deplete residual host lymphocytes is a simple and practical method to do this. At least in AML, the beneficial reduction in GVHD can be achieved without an increased risk of relapse.

Alemtuzumab↗
PubMed1998

Linked suppression of skin graft rejection can operate through indirect recognition.

Adult mice can be rendered immunologically tolerant of allogeneic tissues if transplanted under cover of mAbs to CD4 and CD8. Tolerance generated in this manner is characterized by the presence of regulatory CD4+ T cells that can recruit naive T cells to become tolerant also through "infectious tolerance." Regulatory CD4+ T cells can also suppress rejection of third party transplant Ags provided they are expressed on the same graft as the tolerated Ags. This process of linked suppression can act across whole MHC barriers and represents a powerful mechanism with therapeutic potential. Tolerance can also be induced to reprocessed minor transplantation Ags presented through host APCs (indirect recognition). We here demonstrate that linked suppression can also be induced through the indirect pathway. This finding may be important in the development of transplantation tolerance in the clinic.

Animals↗
PubMed1998

Crystal structures of a rat anti-CD52 (CAMPATH-1) therapeutic antibody Fab fragment and its humanized counterpart.

The CAMPATH-1 family of antibodies are able systematically to lyse human lymphocytes with human complement by targeting the small cell-surface glycoprotein CD52, commonly called the CAMPATH-1 antigen. These antibodies have been used clinically for several years, providing therapy for patients with a variety of immunologically mediated diseases. We report here the first X-ray crystallographic analyses of a Fab fragment from a rat antibody, the original therapeutic monoclonal CAMPATH-1G and its humanized counterpart CAMPATH-1H, into which the six complementarity-determining regions of the rat antibody have been introduced. These structures have been refined at 2.6 A and 3.25 A resolution, respectively. The VL domains of adjacent molecules of CAMPATH-1H form a symmetric dimer within the crystals with an inter-molecular extended beta-sheet as seen in light chain dimers of the kappa class. Crystals of CAMPATH-1G have translational pseudo-symmetry. Within the antibody-combining sites, which are dominated by the protrusion of LysH52b and LysH53 from hypervariable loop H2, the charge distribution and overall integrity are highly conserved, but large changes in the position of loop H1 are observed and an altered conformation of loop H2. The major determinants of this are framework residues H71 and H24, whose identity differs in these two antibodies. These structures provide a detailed structural insight into the transplantation of an intact antibody-combining site between a rodent and a human framework, and provide an increased understanding of the specificity and antigen affinity of this pair of CAMPATH-1 antibodies for CD52. This study forms the structural basis for future modification and design of more effective antibodies to this important antigen.

Alemtuzumab↗
PubMed1998

Therapy with monoclonal antibodies. II. The contribution of Fc gamma receptor binding and the influence of C(H)1 and C(H)3 domains on in vivo effector function.

An in vivo model is used to define Fc motifs engaged by mAbs to deplete target cells. Human IgG1 and human IgG4 were very potent, and mutations within a motif critical for Fc gammaR binding (glutamate 233 to proline, leucine/phenylalanine 234 to valine, and leucine 235 to alanine) completely prevented depletion. Mouse IgG2b was also potent, and mutations to prevent complement activation did not impair depletion with this isotype, as previously shown for human IgG1. In contrast, a mutation that impaired binding to mouse Fc gammaRII (glutamate 318 to alanine) eliminated effector function of mouse IgG2b and also reduced the potency of human IgG4. To reveal potential contributions of domains other than C(H)2, domain switch mutants were created between human IgG1 and rat IgG2a. Two hybrid mAbs were generated with potencies exceeding anything previously seen in this model. While their mechanism of depletion was not defined, their activity appeared dependent upon interdomain interactions in the Fc region.

Amino Acid Sequence↗
PubMed1998

Rejection of H-Y disparate skin grafts by monospecific CD4+ Th1 and Th2 cells: no requirement for CD8+ T cells or B cells.

We wished to determine whether CD4+ T cells could reject a skin graft that was discordant for a single minor transplantation Ag in the absence of CD8+ T cells or Ab. Transgenic A1(M) mice were constructed that express the rearranged V beta 8.2 and V alpha 10 TCR genes from a T cell clone that is specific for the male Ag (H-Y) in the context of H2-Ek. In addition, the RAG-1(-/-) background was bred onto these mice to eliminate any endogenous TCR rearrangements. As expected, clonal deletion was found to be complete in the thymus of male A1(M) x RAG-1(-/-) mice, while only CD4+ T cells were positively selected and found in the periphery of females. Female A1(M) x RAG-1(-/-) mice were able to rapidly reject (in <14 days) male (but not female) skin grafts in a CD4-dependent fashion. After multiple grafts, it was confirmed that no CD8+ T cells or surface Ig+ B cells were present. An immunofluorescent analysis of spleen cells after grafting showed that the majority of T cells expressed activation markers (CD44, CD25, and intracytoplasmic IL-2) and a significant proportion were making IFN-gamma and IL-4. Surprisingly, the transfer of either Th1 or Th2 CD4+ T cell lines from these mice into T cell-depleted recipients was sufficient to cause a specific rejection of male skin.

Animals↗