Pietro E. Cippà

Increased Height in HFE Hemochromatosis

This letter reports increased height in patients with HFE hemochromatosis as compared with controls. The authors speculate that the increased height may be due to nonhematologic roles of iron.

Resistance to ABT-737 in activated T lymphocytes: molecular mechanisms and reversibility by inhibition of the calcineurin–NFAT pathway

Dynamic regulation of the intrinsic apoptosis pathway controls central and peripheral lymphocyte deletion, and may interfere with the pro-apoptotic potency of B-cell lymphoma 2 inhibitors such as ABT-737. By following a T-cell receptor (TCR) transgenic population of alloantigen-specific T cells, we found that sensitivity to ABT-737 radically changed during the course of allo-specific immune responses. Particularly, activated T cells were fully resistant to ABT-737 during the first days after antigen recognition. This phenomenon was caused by a TCR–calcineurin–nuclear factor of activated T cells-dependent upregulation of A1, and was therefore prevented by cyclosporine A (CsA). As a result, exposure to ABT-737 after alloantigen recognition induced selection of alloreactive T cells in vivo, whereas in combination with low-dose CsA, ABT-737 efficiently depleted alloreactive T cells in murine host-versus-graft and graft-versus-host models. Thus, ABT-737 resistance is not a prerogative of neoplastic cells, but it physiologically occurs in T cells after antigen recognition. Reversibility of this process by calcineurin inhibitors opens new pharmacological opportunities to modulate this process in the context of cancer, autoimmunity and transplantation.

Targeting apoptosis to induce stable mixed hematopoietic chimerism and long-term allograft survival without myelosuppressive conditioning in mice

Induction of mixed hematopoietic chimerism results in donor-specific immunological tolerance by apoptosis-mediated deletion of donor-reactive lymphocytes. A broad clinical application of this approach is currently hampered by limited predictability and toxicity of the available conditioning protocols. We developed a new therapeutic approach to induce mixed chimerism and tolerance by a direct pharmacological modulation of the intrinsic apoptosis pathway in peripheral T cells. The proapoptotic small-molecule Bcl-2 inhibitor ABT-737 promoted mixed chimerism induction and reversed the antitolerogenic effect of calcineurin inhibitors by boosting the critical role of the proapoptotic Bcl-2 factor Bim. A short conditioning protocol with ABT-737 in combination with costimulation blockade and low-dose cyclosporine A resulted in a complete deletion of peripheral donor-reactive lymphocytes and was sufficient to induce mixed chimerism and robust systemic tolerance across full major histocompatibility complex barriers, without myelosuppression and by using moderate doses of bone marrow cells. Thus, immunological tolerance can be achieved by direct modulation of the intrinsic apoptosis pathway in peripheral lymphocytes-a new approach to translate immunological tolerance into clinically applicable protocols.

The BH3‐mimetic ABT‐737 inhibits allogeneic immune responses

Apoptosis controls the adaptive immune system through regulation of central and peripheral lymphocyte deletion. Therefore, substances that selectively interact with the intrinsic apoptosis pathway in lymphocytes offer unexplored opportunities to pharmacologically modulate the immune response. Here, we present evidence that the BH3‐mimetic ABT‐737 suppresses allogeneic immune responses. In vitro, ABT‐737 prevented allogeneic T‐cell activation, proliferation, and cytotoxicity by apoptosis induction, but without impairing the physiological functions of remaining viable T cells. In vivo, ABT‐737 was highly selective for lymphoid cells and inhibited allogeneic T‐ and B‐cell responses after skin transplantation. The immunosuppressive effect of ABT‐737 was markedly increased in combination with low‐dose cyclosporine A, as shown by the induction of long‐term skin graft survival without significant inflammatory infiltrates in 50% of the recipients in an MHC class I single antigen mismatched model. Thus, pharmacological targeting of Bcl‐2 proteins represents a novel immunosuppressive approach to prevent rejection of solid organ allografts.

Bcl-2 inhibition to overcome memory cell barriers in transplantation.

Memory T cells (Tm) represent a major barrier for immunosuppression and tolerance induction after solid organ transplantation. Taking into consideration the critical role of the intrinsic apoptosis pathway in the generation and maintenance of Tm, we developed a new concept to deplete alloreactive Tm by targeting Bcl‐2 proteins. The small‐molecule Bcl‐2/Bcl‐XL inhibitor ABT‐737 efficiently induced apoptosis in alloreactive Tm in vitro and in vivo and prolonged skin graft survival in sensitized recipients. A short course of ABT‐737 induction therapy prevented Tm‐mediated resistance in a donor‐specific transfusion model and allowed mixed chimerism induction across Tm barriers. Since Bcl‐2 inhibitors yielded encouraging safety results in cancer trials, this novel approach might represent a substantial advance to prevent allograft rejection and induce tolerance in sensitized recipients.

Synergistic Bcl-2 inhibition by ABT-737 and cyclosporine A.

Survival of lymphocytes and melanocyte stem cells critically depends on B cell lymphoma 2 (Bcl-2). In T lymphocytes, a basal calcineurin activity maintains Bcl-2 expression in naïve cells, and the activation of the calcineurin pathway orchestrates the regulation of the intrinsic apoptosis pathway after antigen recognition. Therefore, calcineurin inhibitors might potentiate the pro-apoptotic effect of pharmacological Bcl-2 inhibitors on lymphatic cells. In vitro, a reduced Bcl-2 expression in lymphocytes exposed to calcineurin inhibitors increased their sensitivity to the small molecule Bcl-2 inhibitor ABT-737. This correlated with an augmented pro-apoptotic activity of ABT-737 on lymphocytes in combination with cyclosporine A in naïve mice in vivo. Interestingly, similar processes were observed in melanocytes. ABT-737 induced a fur depigmentation at the site of injection, and this effect was expanded to a generalized depigmentation in combination with cyclosporine A. Thus, inhibiting calcineurin increases the pro-apoptotic potency of ABT-737 in cells depending on Bcl-2 for survival. The increased efficacy of Bcl-2 inhibitors in combination with cyclosporine A might be relevant to exploit their anti-neoplastic and immuno-modulatory properties.

Distinctive Expression of Bcl-2 Factors in Regulatory T Cells Determines a Pharmacological Target to Induce Immunological Tolerance.

Distinctive molecular characteristics of functionally diverse lymphocyte populations may represent novel pharmacological targets for immunotherapy. The intrinsic apoptosis pathway is differently regulated among conventional and regulatory T cells (Tregs). Targeted pharmacological modulation of this pathway with a small molecule Bcl-2/Bcl-xL inhibitor (ABT-737) caused a selective depletion of effector T cells and a relative enrichment of Tregs in vivo. Treatment with ABT-737 resulted in a tolerogenic milieu, which was exploited to alleviate graft-versus-host disease, to prevent allograft rejection in a stringent fully MHC-mismatched skin transplantation model and to induce immunological tolerance in combination with bone marrow transplantation. This concept has the potential to find various applications for immunotherapy, since it allows pharmacologic exploitation of the immunomodulatory properties of Tregs without the need for cell manipulation ex vivo.

Cytomegalovirus post kidney transplantation: prophylaxis versus pre-emptive therapy?

Cytomegalovirus is the most important pathogen causing opportunistic infections in kidney allograft recipients. The occurrence of CMV disease is associated with higher morbidity, higher incidence of other opportunistic infections, allograft loss and death. Therefore, an efficient strategy to prevent CMV disease after kidney transplantation is required. Two options are currently available: pre‐emptive therapy based on regular CMV PCR monitoring and generalized antiviral prophylaxis during a defined period. In this review, we describe those two approaches, highlight the distinct advantages and risks of each strategy and summarize the four randomized controlled trials performed in this field so far. Taken this evidence together, pre‐emptive therapy and anti‐CMV prophylaxis are both equally potent in preventing CMV‐associated complications; however, the pre‐emptive approach may have distinct advantages in allowing for development of long‐term anti‐CMV immunity. We propose a risk‐adapted use of these approaches based on serostatus, immunosuppressive therapy and availability of resources at a particular transplant centre.

Diagnostic performance of reproducible chest wall tenderness to rule out acute coronary syndrome in acute chest pain: a prospective diagnostic study

Objectives Acute chest pain (ACP) is a leading cause of hospital emergency unit consultation. As there are various underlying conditions, ranging from musculoskeletal disorders to acute coronary syndrome (ACS), thorough clinical diagnostics are warranted. The aim of this prospective study was to assess whether reproducible chest wall tenderness (CWT) on palpation in patients with ACP can help to rule out ACS. Methods In this prospective, double-blinded diagnostic study, all consecutive patients assessed in the emergency unit at the University Hospital Zurich because of ACP between July 2012 and December 2013 were included when a member of the study team was present. Reproducible CWT on palpation was the initial step and was recorded before further examinations were initiated. The final diagnosis was adjudicated by a study-independent physician. Results 121 patients (60.3% male, median age 47 years, IQR 34–66.5 years) were included. The prevalence of ACS was 11.6%. Non-reproducible CWT had a high sensitivity of 92.9% (95% CI 66.1% to 98.8%) for ACS and the presence of reproducible CWT ruled out ACS (p=0.003) with a high negative predictive value (98.1%, 95% CI 89.9% to 99.7%). Conversely non-reproducible CWT ruled in ACS with low specificity (48.6%, 95% CI 38.8% to 58.5%) and low positive predictive value (19.1%, 95% CI 10.6% to 30.5%). Conclusions This prospective diagnostic study supports the concept that reproducible CWT helps to rule out ACS in patients with ACP in an early stage of the evaluation process. However, ACS and other diagnoses should be considered in patients with a negative CWT test. Trial registration number ClinicalTrial.gov: NCT01724996.

Late antibody-mediated rejection by de novo donor HLA-DP-specific antibody after renal transplantation: a case report

The role of donor HLA-DP-specific antibodies after renal transplantation is controversial, and only preformed HLA-DP-specific antibodies have been shown to mediate rejection. Here we present a case of late humoral rejection mediated by de novo donor HLA-DP-specific antibodies in a non-sensitized recipient. This unique case demonstrates the pathogenic role of de novo anti-DP antibodies and suggests that HLA-DP matching might be relevant for renal transplantation.