Masaaki Zaitsu

A pilot study of operational tolerance with a regulatory T‐cell‐based cell therapy in living donor liver transplantation

Potent immunosuppressive drugs have significantly improved early patient survival after liver transplantation (LT). However, long‐term results remain unsatisfactory because of adverse events that are largely associated with lifelong immunosuppression. To solve this problem, different strategies have been undertaken to induce operational tolerance, for example, maintenance of normal graft function and histology without immunosuppressive therapy, but have achieved limited success. In this pilot study, we aimed to induce tolerance using a novel regulatory T‐cell‐based cell therapy in living donor LT. Adoptive transfer of an ex vivo‐generated regulatory T‐cell‐enriched cell product was conducted in 10 consecutive adult patients early post‐LT. Cells were generated using a 2‐week coculture of recipient lymphocytes with irradiated donor cells in the presence of anti‐CD80/86 monoclonal antibodies. Immunosuppressive agents were tapered from 6 months, reduced every 3 months, and completely discontinued by 18 months. After the culture, the generated cells displayed cell‐number‐dependent donor‐specific inhibition in the mixed lymphocyte reaction. Infusion of these cells caused no significant adverse events. Currently, all patients are well with normal graft function and histology. Seven patients have completed successful weaning and cessation of immunosuppressive agents. At present, they have been drug free for 16‐33 months; 4 patients have been drug free for more than 24 months. The other 3 recipients with autoimmune liver diseases developed mild rejection during weaning and then resumed conventional low‐dose immunotherapy. Conclusions: A cell therapy using an ex vivo‐generated regulatory T‐cell‐enriched cell product is safe and effective for drug minimization and operational tolerance induction in living donor liver recipients with nonimmunological liver diseases. (Hepatology 2016;64:632‐643)

Delayed anti-CD3 therapy results in depletion of alloreactive T cells and the dominance of Foxp3+ CD4+ graft infiltrating cells.

The engineered Fc‐nonbinding (crystallizable fragment‐nonbinding) CD3 antibody has lower mitogenicity and a precise therapeutic window for disease remission in patients with type 1 diabetes. Before anti‐CD3 can be considered for use in transplantation, the most effective timing of treatment relative to transplantation needs to be elucidated. In this study anti‐CD3F(ab′)2 fragments or saline were administered intravenously for 5 consecutive days (early: d1–3 or delayed: d3–7) to mice transplanted with a cardiac allograft (H2b‐to‐H2k; d0). Survival of allografts was prolonged in mice treated with the early protocol (MST = 48 days), but most were rejected by d100. In contrast, in mice treated with the delayed protocol allografts continued to survive long term. The delayed protocol significantly inhibited donor alloreactivity at d30 as compared to the early protocol. A marked increase in Foxp3+ T cells (50.3 ± 1.6%) infiltrating the allografts in mice treated with the delayed protocol was observed (p < 0.0001 vs. early (24.9 ± 2.1%)) at d10; a finding that was maintained in the accepted cardiac allografts at d100. We conclude that the timing of treatment with anti‐CD3 therapy is critical for inducing long‐term graft survival. Delaying administration effectively inhibits the alloreactivity and promotes the dominance of intragraft Foxp3+ T cells allowing long‐term graft acceptance.

Immunosuppressive effects of DTCM-G, a novel inhibitor of the mTOR downstream signaling pathway.

Background A newly developed compound, 3-[(dodecylthiocarbonyl)methyl]-glutarimide (DTCM-G), has been shown to inhibit nuclear translocation of c-Fos/c-Jun in a murine macrophage cell line. Herein, we studied the immunosuppressive properties and potency of DTCM-G. Methods Using purified mouse T cells, the in vitro effects of DTCM-G on activation, cytokine production, proliferation, and cell cycle progression were assessed, and a possible molecular target of DTCM-G was investigated. In a BALB/c (H-2d) to C57BL/6 (H-2b) mouse heart transplantation model, transplant recipients were administered DTCM-G, a calcineurin inhibitor (tacrolimus), and a nuclear factor-&kgr;B inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ). Treatment drugs were administered daily for 14 days after transplantation. Alloimmune responses were assessed in addition to graft survival time. Results After anti-CD3+anti-CD28 monoclonal antibody stimulation, DTCM-G significantly suppressed proliferation, interferon-&ggr; production, and cell cycle progression of activated T cells but not CD25 expression or interleukin-2 production. These effects were accompanied by inhibition of 70-kDa S6 protein kinase phosphorylation, a downstream kinase of the mammalian target of rapamycin. The addition of tacrolimus and DHMEQ to DTCM-G resulted in a robust inhibition of T-cell proliferation. In vivo combination therapy of DTCM-G plus either tacrolimus or DHMEQ significantly suppressed alloreactive interferon-&ggr;–producing precursors and markedly prolonged cardiac allograft survival. Furthermore, combination of all three agents markedly inhibited alloimmune responses and permitted long-term cardiac allograft survival. Conclusions DTCM-G inhibits T cells by suppressing the downstream signal of mammalian target of rapamycin. DTCM-G in combination with tacrolimus and DHMEQ induces a strong immunosuppressive effect in vivo.

Cell mediated rejection

Rejection is the major barrier to successful transplantation and usually results from the integration of multiple mechanisms. Activation of elements of the innate immune system, triggered as a consequence of tissue injury sustained during cell isolation or organ retrieval as well as ischemia-reperfusion, will initiate and amplify the adaptive response. For cell mediated rejection, T cells require multiple signals for activation, the minimum being two signals; antigen recognition and costimulation. The majority of B cells require help from T cells to initiate alloantibody production. Antibodies reactive to donor HLA molecules, minor histocompatibility antigens, endothelial cells, red blood cells, or autoantigens can trigger or contribute to rejection early as well as late after transplantation.

Dendritic cells conditioned with NK026680 prolong cardiac allograft survival in mice.

Background Pharmacologically modulated dendritic cells (DCs) can potentially regulate alloimmune responses. We examined the characteristics of immunoregulatory DCs induced by a novel triazolopyrimidine derivative, NK026680, which has been previously shown to inhibit DC maturation. Methods DCs were generated from bone marrow progenitor cells from C57BL/6 (B6, H-2b haplotype) mice with granulocyte-macrophage colony-stimulating factor and interleukin (IL)-4. DCs were cultured with allogeneic BALB/c (H-2d) splenocyte lysates with or without NK026680. DC functions were examined in vitro after stimulation of tumor necrosis factor &agr; and in vivo by the intravenous injection of C3He/J (C3H, H-2k) DCs cultured with B6 cell lysates and NK026680 into C3H mice. Seven days later, DC-treated mice received B6 heart allografts, and graft survival and alloimmune responses were assessed. Results In NK026680-treated DCs (NK-DCs), significant inhibition of the up-regulation of surface activation markers (CD40, CD80, CD86, and major histocompatibility complex class II) and IL-12 p40 production was observed after stimulation of tumor necrosis factor &agr; compared with that of control DCs. Furthermore, NK-DCs suppressed alloreactive T-cell proliferation. The modulation of NK-DCs was likely associated with the inhibition of phosphorylation of p38 mitogen-activated protein kinase and the up-regulation of indolamine 2,3-dioxygenase expression. Compared with both noninjected and control DC–injected mice, mice that received a single in vivo infusion of NK-DCs showed significant increases in splenocyte IL-10 production and the splenic CD4+ IL-10high T-cell population 7 days after injection, a significantly increased splenic CD4+CD25+FoxP3+ T-cell population 14 days after injection, and markedly prolonged cardiac allograft survival. Conclusions Ex vivo NK026680 conditioning allows DCs to acquire immunoregulatory properties that suppress alloimmune responses and prolong cardiac allograft survival.

Immunomodulatory effect of nuclear factor-κB inhibition by dehydroxymethylepoxyquinomicin in combination with donor-specific blood transfusion.

Background. Nuclear factor-&kgr;B (NF-&kgr;B) is a key molecule in alloimmune responses, however, its role in tolerance induction is not clear. We have previously reported that dehydroxymethylepoxyquinomycin (DHMEQ), a novel NF-&kgr;B inhibitor, prolongs cardiac allograft survival. In this study, we evaluated the immunomodulatory effects of DHMEQ when combined with a donor-specific blood transfusion (DST), and assessed whether the treatment induces tolerance in a mouse heart transplantation model. Methods. DST (20×106 splenocytes) was given intravenously at day −7. DHMEQ (30 mg/kg/day) was administered intraperitoneally for 14 days after DST. Graft survival and histology were evaluated. The underlying mechanisms of immunomodulation by DST and DHMEQ treatments were investigated by assessing alloimmune responses after transplantation. Results. In fully mismatched H2d-to-H2b heart transplants, DST alone prolonged allograft median survival time to 15 days, whereas when DST was combined with DHMEQ treatment, the graft median survival time was prolonged to 39.5 days. When the donor-recipient strain combination was reversed, that is, H2b-to-H2d, heart transplants were accepted (>150 days survival) in more than 60% of recipients treated with a DST and DHMEQ, whereas control allografts were all rejected within 8 days. The combined therapy markedly inhibited immune responses by both the direct and indirect allorecognition pathways mainly attributed to promotion of activation-induced cell death and Treg generation. Conclusions. Our results demonstrate the distinctive ability of NF-&kgr;B inhibition in combination with donor alloantigen to promote transplantation tolerance through multiple cellular mechanisms.

Selective blockade of CD28 on human T cells facilitates regulation of alloimmune responses

T cells are central to the detrimental alloresponses that develop in autoimmunity and transplantation, with CD28 costimulatory signals being key to T cell activation and proliferation. CTLA4-Ig molecules that bind CD80/86 and inhibit CD28 costimulation offer an alternative immunosuppressive treatment, free from some of the chronic toxicities associated with calcineurin inhibition. However, CD80/86 blockade by CTLA4-Ig also results in the loss of coinhibitory CTLA4 signals that are critical to the regulation of T cell activation. Here, we show that a nonactivating monovalent anti-CD28 that spares CTLA4 signaling is an effective immunosuppressant in a clinically relevant humanized mouse transplant model. We demonstrate that selective CD28 blockade prolongs human skin allograft survival through a mechanism that includes a reduction in the cellular graft infiltrate. Critically, selective CD28 blockade promotes Treg function in vivo and synergizes with adoptive Treg therapy to promote transplant survival. In contrast to CTLA4-Ig treatment, selective CD28 blockade promotes regulation of alloimmune responses and facilitates Treg-based cellular therapy.

Antagonist Anti-CD28 Therapeutics for the Treatment of Autoimmune Disorders

The effector functions of T lymphocytes are responsible for most autoimmune disorders and act by directly damaging tissues or by indirectly promoting inflammation and antibody responses. Co-stimulatory and co-inhibitory T cell receptor molecules are the primary pharmacological targets that enable interference with immune-mediated diseases. Among these, selective CD28 antagonists have drawn special interest, since they tip the co-stimulation/co-inhibition balance towards efficiently inhibiting effector T cells while promoting suppression by pre-existing regulatory T-cells. After having demonstrated outstanding therapeutic efficacy in multiple models of autoimmunity, inflammation and transplantation, and safety in phase-I studies in humans, selective CD28 antagonists are currently in early clinical development for the treatment of systemic lupus erythematous and rheumatoid arthritis. Here, we review the available proof of concept studies for CD28 antagonists in autoimmunity, with a special focus on the mechanisms of action.

The Immune Monitoring for Operationally Tolerant Recipients Following a Regulatory T cell-based Cell Therapy

Background and Aim We have firstly demonstrated that regulatory T cell (Treg)-enriched cell therapy efficiently promotes an operational tolerance in 7 of 10 cases of living donor liver transplantation (LT). To identify the tolerant immune status and immunological characteristics of the patients following a cell therapy, we evaluated the immune profiles for a total of 5 years including 3.5 years of completely off IS. Methods PBMCs were collected at pre- and post-transplant periods (7, 14 days, 1, 3, 6 months and annually) from the patients including 7 patients who successfully weaned off IS (off IS group) and 3 patients who were unable to be completely off IS due to a rejection (on IS group). Immunological assays including lymphocyte subset analysis (FCM) and allo-immune responses (IFNg ELISPOT and MLR) were performed. Results The dynamic immune profile showed that the anti-donor reactivity was occasionally observed without histologic evidence of rejection in a tolerant case. Meanwhile IFNg ELISpot and cell proliferation assays displayed a donor-specific hyporesponsiveness at long-term; 5 (2-6) years post-LDLT in all patients although the slightly higher frequencies of anti-donor CD4+ T cell reactivity were found in on IS group. Also an increase in the percentage of CD4+Foxp3+ Tregs during early periods was observed in off IS group (n=7, d7, d14 and d28 post-LT vs. pre-LT, p<0.05, paired T test). Interestingly such phenomenon was found at long-term post-LT (15.9% in off IS vs. 6.47% in on IS). Furthermore, CD4+ lymphocytes in the peripheral blood obtained from the patients in on IS group (n=3) at pre- and early duration post-LT, were expressed CD45RA and CD62L (so-called naïve subset, *p<0.05 vs. off IS, Fig. A). In contrast, a significant higher percentage of CD4+ memory T cell, namely central memory (CD45RA-CD62L+, Tcm) population was found in off IS patients (n=7, *p<0.05 vs. on IS, Fig. B). Conclusion The dynamic profile of immune status after an infusion of Treg-enriched cell products for a long-term revealed that the lymphocytes subset such as CD4+ Treg and Tcm during peri-transplant periods may be associated with an induction of immune tolerance by a cell based treatment. A grant in aid from the Japanese Ministry of Health, Labour and Welfare (22130701). Figure. No caption available.

3-[(dodecylthiocarbonyl)methyl]-glutarimide attenuates graft arterial disease by suppressing alloimmune responses and vascular smooth muscle cell proliferation.

Background Graft arterial disease (GAD) is a major cause of late graft loss after organ transplantation. Alloimmune responses and vascular remodeling eventually cause the transplant organ to develop GAD. In this study, we aimed to limit the development of GAD by inhibiting alloimmune responses and vascular smooth muscle cell (VSMC) proliferation with a new compound, 3-[(dodecylthiocarbonyl)methyl]-glutarimide ([DTCM]-glutarimide), in a murine cardiac model of GAD. Methods The hearts from B6.CH-2bm12 mice were transplanted into C57BL/6 mouse recipients to examine the extent of GAD. The recipients were treated with either vehicle or DTCM-glutarimide intraperitoneally (40 mg/kg per day) for 4 weeks. Results The administration of DTCM-glutarimide attenuated GAD formation (luminal occlusion: 37.9 ± 5.9% vs 14.8 ± 5.4%, P < 0.05) by inhibiting the number of graft-infiltrating cells and decreasing alloreactive interferon (IFN)-&ggr; production compared with control mice, as measured by the Enzyme-linked ImmunoSpot assay. In vitro, VSMCs proliferated on stimulation with either basic fibroblast growth factor or IFN-&ggr; and splenocytes after transplantation, but the addition of DTCM-glutarimide resulted in the inhibition of VSMC proliferation. Moreover, DTCM-glutarimide suppressed cyclin D1 expression and inhibited cell cycle progression from G1 to S in VSMCs. Conclusions The compound DTCM-glutarimide suppressed GAD development by inhibiting not only alloimmune responses but also VSMC proliferation in the graft.