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Biomedical subjects

Herman Waldmann

Publications and source records attributed to Herman Waldmann.

At least 19 recordsLinked to original sources
PubMed2003

Stable lines of genetically modified dendritic cells from mouse embryonic stem cells.

BACKGROUND: The capacity to activate naïve T cells sets dendritic cells (DCs) apart from other antigen-presenting cells, making them attractive targets for immune intervention during deleterious immune responses. The inherent resistance of terminally differentiated DCs to conventional strategies for genetic modification has, however, greatly limited our understanding of the molecular mechanisms underlying their function. METHODS AND RESULTS: We report the derivation of long-term cultures of untransformed DCs, uniformly expressing a defined mutant phenotype by the directed differentiation of cloned embryonic stem cells, stably transfected with a reporter gene. Introduction of the gene encoding enhanced green fluorescent protein into pluripotent stem cells demonstrated no observable impact on the phenotype, immunogenicity, or capacity for maturation of DCs differentiated from them. CONCLUSIONS: The production of unlimited numbers of mutant DCs from genetically modified embryonic stem cells paves the way for the systematic elucidation of gene function in this cell type and the rational design of DCs for use in immunotherapy.

Animals↗
PubMed2003

Reconstitution of the Epstein-Barr virus-specific cytotoxic T-lymphocyte response following T-cell-depleted myeloablative and nonmyeloablative allogeneic stem cell transplantation.

The recovery of circulating antigen-specific T-cell immunity to Epstein-Barr virus (EBV) was determined in ELIspot assays following allogeneic myeloablative or nonmyeloablative stem cell transplantation (MST/NST). In 8 of 12 MST patients receiving an alemtuzumab-treated graft, the frequency of the EBV-specific reactivities was similar to or greater than that seen in the healthy controls. A response was detectable in 3 of 6 and 6 of 9 patients by 3 and 6 months, respectively, and in all patients by one year following MST. In contrast, only 1 of 9 (95% confidence interval [CI], 0-2.8) patients made a detectable EBV-specific response by 6 months following NST conditioned with fludarabine, melphalan, and alemtuzumab. Responses were detected in 7 of 10 patients by 1 year after NST. Parallel surveillance demonstrated that other virus infections occurred more frequently and earlier after transplantation in NST patients. The use of alemtuzumab in vivo in the nonmyeloablative conditioning might have resulted in the delay in EBV-specific T-cell recovery and increased virus infections.

Alemtuzumab↗
PubMed2003

Regulatory T cells in the induction and maintenance of peripheral transplantation tolerance.

It is now possible to induce donor-specific transplantation tolerance in adult rodents using non-depleting monoclonal antibodies against T cell co-receptor and co-stimulation molecules or by immunisation with tolerogenic antigen-presenting cells. It is a common finding of all these models of peripheral tolerance, as well as of various mouse models of autoimmune disease, that regulatory CD4(+) T cells are the principal mediators. There are currently no specific markers for regulatory T cells, but in some autoimmune models their activity has been associated with the expression of activation markers such as CD25 and CTLA4, or anti-inflammatory cytokines such as IL-10 and TGF-beta. CD4(+)CD25(+) T cells from both naïve and tolerised donors are able to transfer tolerance to grafts in lymphopenic recipients, and this may be directly applicable to bone-marrow transplantation. The challenge is now to understand the biological principles that allow such immune re-programming so that they can be safely applied to clinical organ grafting.

Animals↗
PubMed2003

The new immunosuppression.

New knowledge on how lymphocytes become tolerant to antigens is now enabling novel tolerance-harnessing strategies to enter the clinical arena. In the field of transplantation, monoclonal antibodies used either to deplete lymphocytes or to block T-cell function can induce tolerance in mice and non-human primates. Understanding the mechanisms underlying tolerance should enable application to the clinic. Harnessing of tolerance mechanisms may enable more judicious use of conventional immunosuppressive agents even to the point of maintenance monotherapy, so limiting drug side effects and ensuring compliance.

Animals↗
PubMed2003

T-cell depletion with Campath-1H "in the bag" for matched related allogeneic peripheral blood stem cell transplantation is associated with reduced graft-versus-host disease, rapid immune constitution and improved survival.

We studied the outcome of 24 peripheral blood stem cell (PBSC) graft recipients, who were T-cell depleted (TCD) with either 20 mg (n = 14) or 10 mg (n = 10) Campath-1H in vitro, in comparison with a retrospective cohort of 23 unmanipulated (UM) PBSC recipients. While the neutrophil engraftment was similar, the platelet engraftment occurred earlier in the TCD group (d 11 vs 14). The incidence of acute and chronic graft-versus-host-disease (GVHD) was 8.7% and 4.4% in the TCD group, respectively, compared with 47.7% and 56.3% in UM group (P < 0.001). In the TCD group, 5/6 chronic myeloid leukaemia (CML) and 4/18 non-CML patients relapsed (vs 0/6 and 3/17 in UM group, P = 0.06). All four molecular or cytogenetic relapses of CML were disease-free survivors following donor lymphocyte infusion. There was no difference in the incidence of serious infection between the TCD and UM groups and the lymphocyte recovery at 100 d was comparable. In the TCD cohort, the lymphocyte recovery was quicker in the 10 mg Campath-1H group. The non-relapse mortality (19.1%vs 66.3%) and 3 year survival (73.1 vs 19.2) were improved in the TCD group (P = 0.05). Thus elimination of late mortalities related to chronic GVHD and a rapid immune reconstitution, limiting either infection or relapse related deaths, contributed to an improved outcome following T-cell depletion with Campath-1H "in the bag".

Adult↗
PubMed2003

Reduced-intensity transplantation with in vivo T-cell depletion and adjuvant dose-escalating donor lymphocyte infusions for chemotherapy-sensitive myeloma: limited efficacy of graft-versus-tumor activity.

Reduced-intensity conditioning regimens allow application of allogeneic stem cell transplantation to greater numbers of patients with myeloma by reducing transplantation-related mortality. We prospectively evaluated the role of an approach incorporating in vivo T-cell depletion and subsequent adjuvant donor lymphocyte infusions (DLIs) as part of front-line therapy for chemotherapy-sensitive multiple myeloma. Twenty patients with HLA-matched related (n = 12) or unrelated (n = 8) donors entered the study. None had previously undergone autologous transplantation. Acute graft-versus-host disease (GVHD) following transplantation was minimal (3 grade II and no grade III or IV). Nonrelapse mortality rate was relatively low (15%) compared with conventional myeloablative allogeneic transplantation series, although it remained significantly higher than in the autologous setting. Disease responses by 6 months posttransplantation were modest (2 in complete remission, 4 in partial remission, 2 were minimally responsive, 6 had no change, 3 had progressive disease, and 3 were not evaluable). Fourteen patients received escalating-dose DLI for residual/progressive disease. Three developed acute GVHD and 2 developed limited chronic GVHD. Seven demonstrated further disease responses, which appeared to be more common in those developing GVHD (5 of 5 versus 2 of 9; P =.02). All responses were associated with conversion from mixed to full donor T-cell chimerism. Response durations were disappointing (5 <12 months) and progression often occurred despite persisting full donor chimerism. Two-year estimated overall survival and current progression-free survival rates (intention to treat with DLI from 6 months) were 71% and 30%, respectively. The current approach incorporating T-cell depletion appears excessively immunosuppressive despite attempts to restore immune function with DLI. Dose escalation failed to allow convincing dissociation of graft-versus-myeloma from GVHD. Attempts to hasten immune reconstitution and to focus and amplify appropriate components of allogeneic T-cell responses will be required to increase complete remission rates and response durations.

Adult↗
PubMed2002

Immune reconstitution at 6 months following T-cell depleted hematopoietic stem cell transplantation is predictive for treatment outcome.

BACKGROUND: Compared with allogeneic bone marrow, in cytokine mobilized blood stem cell grafts, the number of hematopoietic progenitors and lymphoid cells is higher. Consequently, we compared the immune reconstitution following these two transplant modalities in patients receiving T-cell depleted grafts for hematological malignancies and studied the impact of lymphocyte subset recovery on clinical outcome. METHODS: Conditioning for transplantation was radiation-based, while graft versus host disease prophylaxis was by ex vivo T-cell depletion with Campath-1 antibodies. Clinical parameters of patients receiving bone marrow or cytokine-mobilized progenitor cell transplants were reviewed with emphasis placed on defining infectious events and on the causes of treatment failure (relapse, graft failure, or any cause of death). The blood lymphoid subsets, as well as markers for memory and naive T cells, were sequentially studied by standard flow cytometry. Serum immunoglobulins (Ig) concentrations were also determined. RESULTS: The patient population included 15 females and 27 males with a median age of 32.5 (range 15-54) years. Source of human leukocyte antigen-identical sibling allogeneic grafts was bone marrow in 14 and peripheral blood (PBPC) in 28. The median follow-up was of 1,278 (range 47-2,466) days. Following hematopoietic recovery, within the first year, 28 patients were readmitted for pyrexial episodes, and four died of sepsis. In both groups, while the CD8+ subset recuperated rapidly, CD19 and CD4+ T cells remained significantly decreased even after 12 months, leading to persistently abnormal CD4:CD8 ratios. The median values of CD16+ and CD56+ (natural killer) cells remained normal throughout the study period. Despite the patients who were receiving PBPC grafts having significantly higher numbers of allogeneic mononuclear cells (x 10(8)/kg; median: 6.97; range 4.03-10.10 vs. 0.71; range 0.45-0.99; P<0.001) and colony-forming unit granulocyte-macrophages (CFU-GMs) (x 10(4)/kg; median: 27.75; range 0-196, 2 vs. 13.05; range 2.43-57; P<0.05), the recovery rate of B cells or T-cell subpopulations was similar to those receiving bone marrow transplantation (BMT). Double fluorescence studies showed that CD2/CD45RO and RA as well as CD4/CD45RO and RA remained subnormal even after 12 months follow-up. During the observation period, except for IgA, normal levels of immunoglobulins were detected. In all, 18 out of 42 patients failed therapy, and 14 patients died. Treatment failure occurred at a median of 270 (range 47-1,638) days and was significantly associated with low total lymphocyte count (P = 0.01), CD2 (P = 0.09), CD8 (P = 0.01), CD19 (P = 0.02), CD45RA (P = 0.05), and CD4/CD45RA (P = 0.01), when tested at 6 months from transplantation. CONCLUSIONS: After T-cell depleted allogeneic PBPC or BMT, no differences in the rate of immune recovery were detected. However, patients with specific subset abnormalities at 6 months from grafting had a significantly higher risk of treatment failure.

Adolescent↗
PubMed2002

Dominant transplantation tolerance impairs CD8+ T cell function but not expansion.

Alloreactive CD8+ T cells may persist in animals made tolerant of transplanted tissues; their function is controlled through continuous censorship by regulatory CD4+ T cells. We sought to establish the stage at which such censorship operates. We found that monospecific CD8+ T cells introduced into tolerant animals responded to the tolerated tissue antigen as if they had received CD4+ T cell "help": they proliferated and accumulated normally. However, they did show compromised graft rejection, interferon-gamma production and cell-mediated cytotoxicity. These findings suggest that tolerance mediated by regulatory T cells acts by censoring immune effector functions rather than by limiting the induction of T cell responses.

Animals↗
PubMed2002

Phase II trial of subcutaneous anti-CD52 monoclonal antibody alemtuzumab (Campath-1H) as first-line treatment for patients with B-cell chronic lymphocytic leukemia (B-CLL).

This phase II study determined the efficacy and safety of alemtuzumab, a humanized anti-CD52 monoclonal antibody, delivered subcutaneously as first-line therapy, over a prolonged treatment period of 18 weeks in 41 patients with symptomatic B-cell chronic lymphocytic leukemia (B-CLL). Injections were administered subcutaneously 3 times per week, from week 2 to 3 onward. An overall response rate (OR) of 87% (95% CI, 76%-98%; complete remission [CR], 19%; partial remission [PR], 68%) was achieved in 38 evaluable patients (81% of intent-to-treat population). CLL cells were cleared from blood in 95% patients in a median time of 21 days. CR or nodular PR in the bone marrow was achieved in 66% of the patients and most patients achieved this after 18 weeks of treatment. An 87% OR (29% CR) was achieved in the lymph nodes. The median time to treatment failure has not yet been reached (18+ months; range, 8-44+ months). Transient injection site skin reactions were seen in 90% of patients. Rigor, rash, nausea, dyspnea, and hypotension were rare or absent. Transient grade IV neutropenia developed in 21% of the patients. Infections were rare, but 10% patients developed cytomegalovirus (CMV) reactivation. These patients rapidly responded to intravenous ganciclovir. One patient, allergic to cotrimoxazole prophylaxis, developed Pneumocystis carinii pneumonia. Alemtuzumab is highly effective as first-line treatment in patients with B-CLL. Prolonged treatment is important for maximal bone marrow response. Subcutaneous administration induced very few "first-dose" flulike symptoms and may reduce health care costs in comparison with the intravenous infusions.

Adult↗
PubMed2002

Identification of regulatory T cells in tolerated allografts.

Induction of transplantation tolerance with certain therapeutic nondepleting monoclonal antibodies can lead to a robust state of peripheral "dominant" tolerance. Regulatory CD4+ T cells, which mediate this form of "dominant" tolerance, can be isolated from spleens of tolerant animals. To determine whether there were any extra-lymphoid sites that might harbor regulatory T cells we sought their presence in tolerated skin allografts and in normal skin. When tolerated skin grafts are retransplanted onto T cell-depleted hosts, graft-infiltrating T cells exit the graft and recolonize the new host. These colonizing T cells can be shown to contain members with regulatory function, as they can prevent nontolerant lymphocytes from rejecting fresh skin allografts, without hindrance of rejection of third party skin. Our results suggest that T cell suppression of graft rejection is an active process that operates beyond secondary lymphoid tissue, and involves the persistent presence of regulatory T cells at the site of the tolerated transplant.

Animals↗
PubMed2002

High incidence of cytomegalovirus infection after nonmyeloablative stem cell transplantation: potential role of Campath-1H in delaying immune reconstitution.

Nonmyeloablative conditioning is increasingly used for transplantation in a wide range of diseases, but little is known about its impact on the incidence of infections and immune reconstitution. We examined the pattern and outcome of cytomegalovirus (CMV) infections monitored by polymerase chain reaction-based assays and treated preemptively in 101 patients following nonmyeloablative conditioning containing in vivo Campath-1H. Fifty-one patients (50%) had a CMV infection at a median of 27 days after transplantation with a probability of 84.8% in patients at risk of CMV infection. The probability of recurrence of CMV infection before and after 100 days was 53.6% and 46.6%, respectively, and was more common in unrelated donor transplant recipients. All 3 patients who developed CMV disease died of this complication. The 2 patients with late CMV disease had grade III to IV graft-versus-host-disease (GVHD), which occurred de novo in only 4% of patients and in another 10% following donor lymphocyte infusions. The median time to CD4(+) T-cell count more than 200/microL was 9 months in the 48 patients studied. The probabilities of overall survival and nonrelapse mortality at 18 months were 65% and 27.8%, respectively, with no significant difference in survival between CMV-infected and -uninfected patients. The use of Campath-1H appeared to be associated with a low incidence of GVHD but a high incidence of CMV infections and prolonged immune paresis.

Adolescent↗
PubMed2002

Both CD4(+)CD25(+) and CD4(+)CD25(-) regulatory cells mediate dominant transplantation tolerance.

CD4(+)CD25(+) T cells have been proposed as the principal regulators of both self-tolerance and transplantation tolerance. Although CD4(+)CD25(+) T cells do have a suppressive role in transplantation tolerance, so do CD4(+)CD25(-) T cells, although 10-fold less potent. Abs to CTLA-4, CD25, IL-10, and IL-4 were unable to abrogate suppression mediated by tolerant spleen cells so excluding any of these molecules as critical agents of suppression. CD4(+)CD25(+) T cells from naive mice can also prevent rejection despite the lack of any previous experience of donor alloantigens. However, this requires many more naive than tolerized cells to provide the same degree of suppression. This suggests that a capacity to regulate transplant rejection pre-exists in naive mice, and may be amplified in "tolerized" mice. Serial analysis of gene expression confirmed that cells sorted into CD4(+)CD25(+) and CD4(+)CD25(-) populations were distinct in that they responded to TCR ligation with very different programs of gene expression. Further characterization of the differentially expressed genes may lead to the development of diagnostic tests to monitor the tolerant state.

Abatacept↗
PubMed2002

Limiting transplantation-related mortality following unrelated donor stem cell transplantation by using a nonmyeloablative conditioning regimen.

A nonmyeloablative conditioning regimen was investigated in 47 patients with hematological malignancy receiving allogeneic progenitor cells from matched, unrelated donors. The median patient age was 44 years. The majority of patients had high-risk features, including having failed a prior transplantation (29 individuals). Twenty of the transplants were mismatched for HLA class I and/or class II alleles. Recipient conditioning consisted of 20 mg CAMPATH-1H on days -8 to -4, 30 mg/m(2) fludarabine on days -7 to -3, and 140 mg/m(2) melphalan on day -2. Graft-versus-host disease (GVHD) prophylaxis was with cyclosporine A alone. Primary graft failure occurred in only 2 of 44 evaluable patients (4.5%). Chimerism studies in 34 patients indicated that the majority (85.3%) attained initial full donor chimerism. Only 3 patients developed grade III to IV acute GVHD, and no patients have yet developed chronic extensive GVHD. The estimated probability of nonrelapse mortality at day 100 was 14.9% (95% confidence interval [CI], 4.7%-25.1%). With a median follow-up of 344 days (range, 79-830), overall and progression-free survivals at 1 year were 75.5% (95% CI, 62.8%-88.2%) and 61.5% (95% CI, 46.1%-76.8%), respectively. In summary, a nonmyeloablative regimen incorporating in vivo CAMPATH-1H is effective in promoting durable engraftment in most patients and in reducing the risk of severe GVHD following matched unrelated donor transplantation.

Adolescent↗
PubMed2002

Regulatory T cells overexpress a subset of Th2 gene transcripts.

There is now compelling evidence for subpopulations of CD4+ T cells whose role is to prevent immune pathology in both autoimmunity and transplantation. We have cloned CD4+ T cells against a male transplantation Ag that, unlike Th1 or Th2 clones, suppresses the rejection of male skin grafts and are therefore considered examples of regulatory T cells. We have identified, using serial analysis of gene expression, transcripts that are overexpressed in regulatory T cells compared with Th1 and Th2 clones. Some of these transcripts are increased in tolerated rather than rejecting skin grafts and in addition are expressed by the natural regulatory CD4+CD25+ subpopulation of naive mice. These genes include prepro-enkephalin, GM2 ganglioside activator protein, glucocorticoid-induced TNFR superfamily member 18, and integrin alpha(E)beta(7). They seem to represent a subset of transcripts shared with Th2 cells, suggesting that transplantation tolerance and normal immunoregulation may represent a unique form of Th2-like differentiation.

Adoptive Transfer↗
PubMed2002

Reprogramming the immune system.

The immune system is organized so as to react to pathogens without risking damage to self. Harnessing those processes that prevent self-reactivity will have enormous potential in clinical medicine. This review outlines the efforts of this laboratory over the last 25 years to exploit tolerance so as to reprogram the immune system for therapeutic purposes.

Allergy and Immunology↗
PubMed2002

The vaccinia virus C12L protein inhibits mouse IL-18 and promotes virus virulence in the murine intranasal model.

A bioassay that measured the interleukin (IL)-12-induced production of interferon (IFN)-gamma from mouse splenocytes was used to identify a soluble factor in the supernatants of vaccinia virus (VV)-infected cells that inhibited the production of IFN-gamma. This soluble factor was expressed by 14 out of 16 VV strains including the Western Reserve (WR) strain, but strains Copenhagen and Tashkent and a mutant of strain WR called 6/2 lacked this activity. The gene encoding this activity was identified as C12L by transferring DNA present in VV WR but missing in VV WR 6/2 into VV Copenhagen and testing for expression of the soluble factor. The C12L protein shows amino acid similarity to IL-18 binding proteins that are encoded by poxviruses, mice and humans, and C12L protein produced from VV or baculovirus inhibited the biological activity of mouse IL-18 in vitro. Thus the inhibition of IL-12-induced IFN-gamma production was due to indirect effects of C12L on IL-18, illustrating the synergistic action of these pro-inflammatory cytokines. To study the role of the C12L protein in the virus life-cycle, we constructed a deletion mutant lacking the C12L gene and a revertant virus in which the gene was reinserted into the deletion mutant. In vitro the replication and plaque size of these viruses were indistinguishable. However, infection of BALB/c mice by the intranasal route showed that the deletion mutant was attenuated and induced lower weight loss and signs of illness compared to controls.

Administration, Intranasal↗
PubMed2002

A personal history of the CAMPATH-1H antibody.

The recent licensing of CAMPATH-1H (alemtuzumab) for the treatment of patients with refractory chronic lymphocytic leukemia has been the culmination of a long journey. This success is in large part due to the persistence, dedication, and commitment of a large number of academic collaborators. The first breakthrough was the identification of CAMPATH-1M, an isotype directed against CD52, and extremely efficient at lysing target cells in the presence of human complement, but limited in vivo by the rate of complement biosynthesis. The search for a monoclonal antibody that was more efficient in vivo found the rare class-switching variant CAMPATH-1G, which is able to kill target cells by antibody-dependent cell-mediated cytotoxicity. Construction of the humanized form of the antibody, CAMPATH-1H, and the development of resources to manufacture clinical-grade material, further expedited many studies across the world in leukemia and lymphoma as well as in marrow transplantation, autoimmune disorders, and kidney transplantation. Such studies have taught us a lot about the diseases themselves, as well as offering the prospect of harnessing immunological tolerance processes to facilitate a whole new approach to immunosuppression.

Alemtuzumab↗