RESUMO
OBJECTIVE: To evaluate the clinically relevant anti-CD40 antibody iscalimab for baseline immunosuppression in a preclinical pig-to-rhesus renal xenograft model. SUMMARY BACKGROUND DATA: CD40/CD40L co-stimulation blockade-based immunosuppression has been more successful than calcineurin-based protocols in prolonging xenograft survival in preclinical models. METHODS: GGTA1 knockout/CD55 transgenic pig kidneys were transplanted into rhesus monkeys (n = 6) receiving an iscalimab-based immunosuppressive regimen. RESULTS: Two grafts were lost early (22 and 26 days) because of ectatic donor ureters with otherwise normal histology. The other recipients survived 171, 315, 422, and 439 days with good renal function throughout the posttransplant course. None of the recipients experienced serious infectious morbidity. CONCLUSIONS: It may be reasonable to evaluate an iscalimab-based immunosuppressive regimen in clinical renal xenotransplantation.
Assuntos
Sobrevivência de Enxerto , Xenoenxertos , Imunossupressores , Transplante de Rim , Macaca mulatta , Transplante Heterólogo , Animais , Transplante Heterólogo/métodos , Suínos , Sobrevivência de Enxerto/imunologia , Sobrevivência de Enxerto/efeitos dos fármacos , Transplante de Rim/métodos , Imunossupressores/farmacologia , Xenoenxertos/imunologia , Rejeição de Enxerto/imunologia , Rejeição de Enxerto/prevenção & controle , Anticorpos Monoclonais Humanizados/uso terapêutico , Anticorpos Monoclonais Humanizados/farmacologia , Animais Geneticamente Modificados , Anticorpos Monoclonais/farmacologia , Humanos , Galactosiltransferases/genéticaRESUMO
BACKGROUND: Desensitization is one of the strategies to reduce antibodies and facilitate heart transplantation in highly sensitized patients. We describe our center's desensitization experience with combination of plasma cell (PC) depletion therapy (with proteasome inhibitor or daratumumab) and costimulation blockade (with belatacept). METHODS: We reviewed five highly sensitized patients who underwent desensitization therapy with plasma cell depletion and costimulation blockade. We evaluated the response to therapy by measuring the changes in cPRA, average MFI, and number of positive beads > 5000MFI. RESULTS: Five patients, mean age of 56 (37-66) years with average cPRA of 98% at 5000 MFI underwent desensitization therapy. After desensitization, mean cPRA decreased from 98% to 70% (p = .09), average number of beads > 5000 MFI decreased from 59 to 37 (p = .15), and average MFI of beads > 5000 MFI decreased from 16713 to 13074 (p = .26). CONCLUSION: Combined PC depletion and CoB could be a reasonable strategy for sustained reduction in antibodies in highly sensitized patients being listed for heart transplantation.
Assuntos
Transplante de Coração , Plasmócitos , Humanos , Pessoa de Meia-Idade , Abatacepte/uso terapêutico , Abatacepte/farmacologia , Dessensibilização Imunológica , Rejeição de Enxerto/etiologia , Rejeição de Enxerto/prevenção & controle , Antígenos HLA , Isoanticorpos , Inibidores de Proteassoma , Adulto , IdosoRESUMO
The blockade of the CD154-CD40 pathway with anti-CD154 monoclonal antibody has been a promising immunomodulatory approach to prevent allograft rejection. However, clinical trials of immunoglobulin G1 antibodies targeting this pathway revealed thrombogenic properties, which were subsequently shown to be mediated by crystallizable fragment (Fc)-gamma receptor IIa-dependent platelet activation. To prevent thromboembolic complications, an immunoglobulin G4 anti-CD154 monoclonal antibody, TNX-1500, which retains the fragment antigen binding region of ruplizumab (humanized 5c8, BG9588), was modified by protein engineering to decrease Fc binding to Fc-gamma receptor IIa while retaining certain other effector functions and pharmacokinetics comparable with natural antibodies. Here, we report that TNX-1500 treatment is not associated with platelet activation in vitro and consistently inhibits kidney allograft rejection in vivo without clinical or histologic evidence of prothrombotic phenomena. We conclude that TNX-1500 retains efficacy similar to that of 5c8 to prevent kidney allograft rejection while avoiding previously identified pathway-associated thromboembolic complications.
Assuntos
Transplante de Rim , Animais , Transplante de Rim/efeitos adversos , Ligante de CD40 , Rim , Anticorpos Monoclonais/uso terapêutico , Antígenos CD40 , Imunoglobulina G , Primatas , Aloenxertos , Sobrevivência de Enxerto , Rejeição de Enxerto/etiologia , Rejeição de Enxerto/prevenção & controleRESUMO
Regulatory T cells (Tregs) can inhibit cellular immunity in diverse experimental models and have entered early phase clinical trials in autoimmunity and transplantation to assess safety and efficacy. As part of the ONE Study consortium, we conducted a phase I-II clinical trial in which purified donor antigen reactive (dar)-Tregs (CD4+CD25+CD127lo) were administered to 3 patients, 7 to 11 days after live donor renal transplant. Recipients received a modified immunosuppression regimen, without induction therapy, consisting of maintenance tacrolimus, mycophenolate mofetil, and steroids. Steroids were weaned off over 14 weeks. No rejection was seen on any protocol biopsy. Therefore, all patients discontinued mycophenolate mofetil 11 to 13 months posttransplant, per protocol. An early for-cause biopsy in 1 patient, 5 days after dar-Treg infusion, revealed absence of rejection and accumulation of Tregs in the kidney allograft. All patients had Treg-containing lymphoid aggregates evident on protocol biopsies performed 8 months posttransplant. The patients are now all >6 years posttransplant on tacrolimus monotherapy with excellent graft function. None experienced rejection episodes. No serious adverse events were attributable to Treg administration. These results support a favorable safety profile of dar-Tregs administered early after renal transplant, suggest early biopsy might be an instructive research endpoint and provide preliminary evidence of potential immunomodulatory activity.
Assuntos
Imunossupressores , Tacrolimo , Humanos , Imunossupressores/farmacologia , Tacrolimo/uso terapêutico , Ácido Micofenólico/uso terapêutico , Doadores Vivos , Linfócitos T Reguladores , Projetos Piloto , Rim , Esteroides , Rejeição de Enxerto/etiologia , Rejeição de Enxerto/prevenção & controle , Rejeição de Enxerto/tratamento farmacológicoRESUMO
Belatacept-based immunosuppression in kidney transplantation confers fewer off-target toxicities than calcineurin inhibitors but comes at a cost of increased incidence and severity of acute rejection, potentially due to its deleterious effect on both the number and function of Foxp3+ regulatory T cells (Tregs). TIGIT is a CD28 family coinhibitory receptor expressed on several subsets of immune cells including Tregs. We hypothesized that coinhibition through TIGIT signaling could function to ameliorate costimulation blockade-resistant rejection. The results demonstrate that treatment with an agonistic anti-TIGIT antibody, when combined with costimulation blockade by CTLA-4Ig, can prolong allograft survival in a murine skin graft model compared with CTLA-4Ig alone. Further, this prolongation of graft survival is accompanied by an increase in the frequency and number of graft-infiltrating Tregs and a concomitant reduction in the number of CD8+ T cells in the graft. Through the use of Treg-specific TIGIT conditional knockout animals, we demonstrated that the TIGIT-mediated reduction in the graft-infiltrating CD8+ T cell response is dependent on signaling of TIGIT on Foxp3+ Tregs. Our results highlight both the key functional role of TIGIT on Foxp3+ Tregs under conditions in which CTLA-4 is blocked and the therapeutic potential of TIGIT agonism to optimize costimulation blockade-based immunosuppression.
Assuntos
Transplante de Rim , Linfócitos T Reguladores , Animais , Camundongos , Abatacepte/farmacologia , Linfócitos T CD8-Positivos , Fatores de Transcrição Forkhead , Rejeição de Enxerto/tratamento farmacológico , Rejeição de Enxerto/etiologia , Rejeição de Enxerto/prevenção & controle , Sobrevivência de Enxerto , Transplante de Rim/efeitos adversos , Transplante HomólogoRESUMO
Combined antigen-specific T cell receptor stimulation and costimulation are needed for complete T cell activation. Belatacept and abatacept are nondepleting fusion proteins blocking CD28/B7 costimulation, whereas siplizumab is a depleting antiCD2 immunoglobulin G1 monoclonal antibody targeting CD2/CD58 costimulation. Herein, the effect of siplizumab combination therapy with abatacept or belatacept on T cell alloreactivity in mixed lymphocyte reactions was investigated. In contrast to monotherapy, the combination of siplizumab with belatacept or abatacept induced near-complete suppression of T cell proliferation and increased the potency of siplizumab-mediated T cell inhibition. Furthermore, dual targeting of CD2 and CD28 costimulation enhanced the selective depletion of memory T cells compared with monotherapy. Although siplizumab monotherapy leads to significant regulatory T cell enrichment, high doses of cytotoxic T-lymphocyte-associated antigen 4 and a human IgG1 Fc fragment in the combination therapy reduced this effect. These results support the clinical evaluation of dual costimulation blockade, combining siplizumab with abatacept or belatacept, for the prophylaxis of organ transplant rejection and improvement of long-term outcomes following transplantation. Ongoing investigative research will elucidate when other forms of siplizumab-based dual costimulatory blockade may be able to induce similarly strong inhibition of T cell activation although still allowing for enrichment of regulatory T cells.
Assuntos
Antígenos CD28 , Transplante de Rim , Humanos , Abatacepte/farmacologia , Abatacepte/uso terapêutico , Transplante de Rim/métodos , Anticorpos Monoclonais Humanizados/farmacologia , Imunossupressores/farmacologia , Imunossupressores/uso terapêutico , Rejeição de Enxerto/tratamento farmacológico , Rejeição de Enxerto/prevenção & controleRESUMO
One of the biggest barriers to achieving allograft tolerance is the presence of immunological memory within the recipient, which confers a faster, more robust immune response that is in most cases more resistant to pharmacologic immunosuppression. This review will identify the mechanisms by which alloreactive T cells arise within hosts prior to transplantation, and explore the properties of immunological memory that contribute to allograft rejection. In doing so we will also illuminate how targeting pathways that induce memory T cell exhaustion can promote allograft tolerance. Recent studies demonstrating the impact of the allograft microenvironment on memory cell survival and activation, as well as new therapeutic strategies that are being explored to mitigate memory driven allograft rejection, will also be reviewed.
Assuntos
Rejeição de Enxerto/imunologia , Memória Imunológica/imunologia , Linfócitos T/imunologia , Tolerância ao Transplante/imunologia , Transplante/métodos , Aloenxertos , Animais , Sobrevivência de Enxerto/imunologia , Humanos , Transdução de Sinais/imunologiaRESUMO
Belatacept was developed to replace calcineurin inhibitors in kidney transplantation. Its use is associated with better kidney transplant function, a lower incidence of anti-donor antibodies and higher graft survival. However, it is also associated with a higher risk of cellular rejection. We studied the activation and proliferation mechanisms of belatacept-resistant T lymphocytes (TLs), to identify new pathways for control. We performed a transcriptomic analysis on CD4+ CD57+ PD1- memory TLs, which are responsible for a higher incidence of graft rejection, after allogeneic stimulation with activated dendritic cells (aDCs) in the presence or absence of belatacept. After six hours of contact with aDCs, the (CD4+ CD57+ PD1- ) (CD4+ CD57+ PD1+ ) and (CD4+ CD57- ) lymphocytes had different transcriptional profiles with or without belatacept. In the CD4+ CD57+ PD1- population, the IFNα-dependent activation pathway was positively overrepresented, and IRF7 transcript levels were high. IRF7 was associated with IFNα/ß and IL-6 regulation. The inhibition of both these cytokines in a context of belatacept treatment inhibited the proliferation of CD4+ CD57+ PD1- T cells. Our results show that IRF7 is rapidly upregulated in belatacept-resistant CD4+ CD57+ PD1- TLs. The inhibition of type I IFN or IL-6 in association with belatacept treatment reduces the proliferation of belatacept-resistant TLs, paving the way for new treatments for use in organ transplantation.
Assuntos
Imunossupressores , Transplante de Rim , Abatacepte/farmacologia , Proliferação de Células , Rejeição de Enxerto/etiologia , Sobrevivência de Enxerto , Imunossupressores/farmacologia , Transplante de Rim/efeitos adversosRESUMO
Hyperlipidemia induces accelerated rejection of cardiac allografts and resistance to tolerance induction using costimulatory molecule blockade in mice due in part to anti-donor Th17 responses and reduced regulatory T cell function. Accelerated rejection in hyperlipidemic mice is also associated with increased serum levels of IL-6. Here, we examined the role of IL-6 in hyperlipidemia-induced accelerated rejection and resistance to tolerance. Genetic ablation of IL-6 prevented hyperlipidemia-induced accelerated cardiac allograft rejection. Using Th17-lineage fate tracking mice, we observed that IL-6 is required to promote the development of anti-donor Th17 lineage cells independently of antigen challenge. In contrast, the frequency of alloreactive T cells producing IL-2 or IFN-γ remained increased in hyperlipidemic IL-6-deficient mice. Ablation of IL-6 overcame hyperlipidemia-induced changes in Tregs, but was not sufficient to overcome resistance to costimulatory molecule blockade induced tolerance. We suggest that accelerated rejection in hyperlipidemic mice results from IL-6 driven anti-donor Th17 responses. While alterations in Tregs were overcome by ablation of IL-6, the reversal of hyperlipidemia-induced changes in Tregs was not sufficient to overcome increased Th1-type anti-donor T cell responses, suggesting that hyperlipidemia induced IL-6-independent effects on recipient immunity prevent tolerance induction.
Assuntos
Transplante de Coração , Hiperlipidemias , Animais , Rejeição de Enxerto/prevenção & controle , Transplante de Coração/efeitos adversos , Hiperlipidemias/etiologia , Interleucina-6 , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BLRESUMO
Eliminating cytoreductive conditioning from chimerism-based tolerance protocols would facilitate clinical translation. Here we investigated the impact of major histocompatibility complex (MHC) and minor histocompatibility antigen (MiHA) barriers on mechanisms of tolerance and rejection in this setting. Transient depletion of natural killer (NK) cells at the time of bone marrow (BM) transplantation (BMT) (20 × 106 BALB/c BM cells â C57BL/6 recipients under costimulation blockade [CB] and rapamycin) prevented BM rejection. Despite persistent levels of mixed chimerism, BMT recipients gradually rejected skin grafts from the same donor strain. Extending NK cell depletion did not improve skin graft survival. However, F1 (C57BL/6×BALB/c) donors, which do not elicit NK cell-mediated rejection, induced durable chimerism and tolerance. In contrast, if F1 donors with BALB/c background only were used (BALB/c×BALB.B), no tolerance was observed. In the absence of MiHA disparities (B10.D2 donors, MHC-mismatch only), temporal NK cell depletion established stable chimerism and tolerance. Conversely, MHC identical BM (BALB.B donors, MiHA mismatch only) readily engrafted without NK cell depletion but no skin graft tolerance ensued. Therefore, we conclude that under CB and rapamycin, MHC disparities provoke NK cell-mediated BM rejection in nonirradiated recipients whereas MiHA disparities do not prevent BM engraftment but impede skin graft tolerance in established mixed chimeras.
Assuntos
Quimerismo , Tolerância Imunológica , Animais , Transplante de Medula Óssea , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Transplante de Pele , Quimeras de Transplante , Tolerância ao TransplanteRESUMO
Costimulation blockade-based regimens are a promising strategy for management of transplant recipients. However, maintenance immunosuppression via CTLA4-Ig monotherapy is characterized by high frequency of rejection episodes. Recent evidence suggests that inflammatory cytokines contribute to alloreactive T cell activation in a CD28-independent manner, a reasonable contributor to the limited efficacy of CTLA4-Ig. In this study, we investigated the possible synergism of a combined short-term inhibition of cytokine signaling and CD28 engagement on the modulation of rejection. Our results demonstrate that the JAK/STAT inhibitor tofacitinib restored the immunomodulatory effect of CTLA4-Ig on mouse alloreactive T cells in the presence of inflammatory cytokines. Tofacitinib exposure conferred dendritic cells with a tolerogenic phenotype reducing their cytokine secretion and costimulatory molecules expression. JAK inhibition also directly affected T cell activation. In vivo, the combination of CTLA4-Ig and tofacitinib induced long-term survival of heart allografts and, importantly, it was equally effective when using grafts subjected to prolonged ischemia. Transplant survival correlated with a reduction in effector T cells and intragraft accumulation of regulatory T cells. Collectively, our studies demonstrate a powerful synergism between CTLA4-Ig and tofacitinib and suggest their combined use is a promising strategy for improved management of transplanted patients.
Assuntos
Transplante de Coração , Imunoconjugados , Abatacepte/farmacologia , Aloenxertos , Animais , Antígeno CTLA-4 , Citocinas , Rejeição de Enxerto/tratamento farmacológico , Rejeição de Enxerto/prevenção & controle , Sobrevivência de Enxerto , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Piperidinas , PirimidinasRESUMO
The pretransplant presence of endogenous donor-reactive memory T cells is an established risk factor for acute rejection and poorer transplant outcomes. A major source of these memory T cells in unsensitized recipients is heterologously generated memory T cells expressing reactivity to donor allogeneic MHC molecules. Multiple clinical studies have shown that the pretransplant presence of high numbers of circulating endogenous donor-reactive memory T cells correlates with higher incidence of acute rejection and decreased graft function during the first-year post-transplant. These findings have spurred investigation in preclinical models to better understand mechanisms underlying endogenous donor-reactive memory T-cell-mediated allograft injury in unsensitized graft recipients. These studies have led to the identification of unique mechanisms underlying the activation of these memory T cells within allografts at early times after transplant. In particular, optimal activation to mediate acute allograft injury is dependent on the intensity of ischaemia-reperfusion injury. Therapeutic strategies directed at the recruitment and activation of endogenous donor-reactive memory T cells are effective in attenuating acute injury in allografts experiencing increased ischaemia-reperfusion injury in preclinical models and should be translatable to clinical transplantation.
Assuntos
Transplante de Coração , Memória Imunológica , Aloenxertos , Linfócitos T CD4-Positivos , Rejeição de Enxerto , Sobrevivência de Enxerto , Transplante HomólogoRESUMO
The risks of chronic immunosuppression limit the utility of vascularized composite allotransplantation (VCA) as a reconstructive option in complex tissue defects. We evaluated a novel, clinically translatable, radiation-free conditioning protocol that combines anti-lymphocyte serum (ALS), tacrolimus, and cytotoxic T-lymphocyte-associated protein 4 immunoglobulin (CTLA4-Ig) with adipose-derived stromal cells (ASCs) to allow VCA survival without long-term systemic immunosuppression. Full-mismatched rat hind-limb-transplant recipients received tacrolimus (0.5 mg/kg) for 14 days and were assigned to 4 groups: controls (CTRL) received no conditioning; ASC-group received CTLA4-Ig (10 mg/kg body weight i.p. postoperative day [POD] 2, 4, 7) and donor ASCs (1 × 106 iv, POD 2, 4, 7, 15, 28); the ASC-cyclophosphamide (CYP)-group received CTLA4-Ig, ASC plus cyclophosphamide (50 mg/kg ip, POD 3); the ASC-ALS-group received CTLA4-Ig, ASCs plus ALS (500 µL ip, POD 1, 5). Banff grade III or 120 days were endpoints. ASCs suppressed alloresponse in vitro. Median rejection-free VCA survival was 28 days in CTRL (n = 7), 34 in ASC (n = 6), and 27.5 in ASC-CYP (n = 4). In contrast, ASC-ALS achieved significantly longer, rejection-free VCA survival in 6/7 animals (86%), with persistent mixed donor-cell chimerism, and elevated systemic and allograft skin Tregs , with no signs of acute cellular rejection. Taken together, a regimen comprised of short-course tacrolimus, repeated CTLA4-Ig and ASC administration, combined with ALS, promotes long-term VCA survival without chronic immunosuppression.
Assuntos
Tolerância ao Transplante , Alotransplante de Tecidos Compostos Vascularizados , Animais , Rejeição de Enxerto/prevenção & controle , Sobrevivência de Enxerto , Imunossupressores/uso terapêutico , Ratos , Células EstromaisRESUMO
BACKGROUND: AbataCepT In rOutiNe clinical practice (ACTION; NCT02109666) was a 2-year international observational study of patients with moderate to severe rheumatoid arthritis. METHODS: Baseline characteristics, abatacept retention rates, and clinical outcomes were compared by treatment line in the Austrian cohort of ACTION. RESULTS: Of 100 patients enrolled in Austria, 98 (98.0%) were evaluable: 33/98 (33.7%) biologic naïve and 65/98 (66.3%) with ≥1 prior biologic failure. At baseline, biologic-naïve patients had shorter disease duration and lower concomitant corticosteroid use than biologic-failure patients. Overall crude abatacept retention rate was 60.5% and retention rate was higher in biologic-naïve (65.1%) versus biologic-failure (58.0%) patients. Good/moderate EULAR (European League Against Rheumatism) response rates were 85.7% in biologic-naïve and 100% in biologic-failure patients. CONCLUSIONS: In the Austrian cohort of ACTION, overall abatacept retention at 2 years was high, with higher retention rates in patients receiving abatacept as an earlier treatment line. Good/moderate EULAR response rate was higher in biologic-failure than in biologic-naïve patients.
Assuntos
Antirreumáticos/uso terapêutico , Artrite Reumatoide/tratamento farmacológico , Abatacepte/uso terapêutico , Áustria , Humanos , Resultado do TratamentoRESUMO
T cells play a pivotal role in orchestrating immune responses directed against a foreign (allogeneic) graft. For T cells to become fully activated, the T-cell receptor (TCR) must interact with the major histocompatibility complex (MHC) plus peptide complex on antigen-presenting cells (APCs), followed by a second "positive" costimulatory signal. In the absence of this second signal, T cells become anergic or undergo deletion. By blocking positive costimulatory signaling, T-cell allo-responses can be aborted, thus preventing graft rejection and promoting long-term allograft survival and possibly tolerance (Alegre ML, Najafian N, Curr Mol Med 6:843-857, 2006; Li XC, Rothstein DM, Sayegh MH, Immunol Rev 229:271-293, 2009). In addition, costimulatory molecules can provide negative "coinhibitory" signals that inhibit T-cell activation and terminate immune responses; strategies to promote these pathways can also lead to graft tolerance (Boenisch O, Sayegh MH, Najafian N, Curr Opin Organ Transplant 13:373-378, 2008). However, T-cell costimulation involves an incredibly complex array of interactions that may act simultaneously or at different times in the immune response and whose relative importance varies depending on the different T-cell subsets and activation status. In transplantation, the presence of foreign alloantigen incites not only destructive T effector cells but also protective regulatory T cells, the balance of which ultimately determines the fate of the allograft (Lechler RI, Garden OA, Turka LA, Nat Rev Immunol 3:147-158, 2003). Since the processes of alloantigen-specific rejection and regulation both require activation of T cells, costimulatory interactions may have opposing or synergistic roles depending on the cell being targeted. Such complexities present both challenges and opportunities in targeting T-cell costimulatory pathways for therapeutic purposes. In this chapter, we summarize our current knowledge of the various costimulatory pathways in transplantation and review the current state and challenges of harnessing these pathways to promote graft tolerance (summarized in Table 10.1).
Assuntos
Ativação Linfocitária , Receptores de Antígenos de Linfócitos T/metabolismo , Linfócitos T/citologia , Tolerância ao Transplante , Rejeição de Enxerto , Humanos , Transplante HomólogoRESUMO
Achieving host immune tolerance of allogeneic transplants represents the ultimate challenge in clinical transplantation. It has become clear that different cells and mechanisms participate in acquisition versus maintenance of allograft tolerance. Indeed, manipulations which prevent tolerance induction often fail to abrogate tolerance once it has been established. Hence, elucidation of the immunological mechanisms underlying maintenance of T cell tolerance to alloantigens is essential for the development of novel interventions that preserve a robust and long lasting state of allograft tolerance that relies on T cell deletion in addition to intra-graft suppression of inflammatory immune responses. In this review, we discuss some essential elements of the mechanisms involved in the maintenance of naturally occurring or experimentally induced allograft tolerance, including the newly described role of antigen cross-dressing mediated by extracellular vesicles.
Assuntos
Sobrevivência de Enxerto/imunologia , Isoantígenos/imunologia , Linfócitos T/imunologia , Tolerância ao Transplante/imunologia , AnimaisRESUMO
Recent clinical studies suggest that operational allograft tolerance can be persistent, but long-term surviving allografts can be rejected in a subset of patients, sometimes after episodes of infection. In this study, we examined the impact of Listeria monocytogenes (Lm) infection on the quality of tolerance in a mouse model of heart allograft transplantation. Lm infection induced full rejection in 40% of tolerant recipients, with the remaining experiencing a rejection crisis or no palpable change in their allografts. In the surviving allografts on day 8 postinfection, graft-infiltrating cell numbers increased and exhibited a loss in the tolerance gene signature. By day 30 postinfection, the tolerance signature was broadly restored, but with a discernible reduction in the expression of a subset of 234 genes that marked tolerance and was down-regulated at day 8 post-Lm infection. We further demonstrated that the tolerant state after Lm infection was functionally eroded, as rejection of the long-term surviving graft was induced with anti-PD-L1 whereas the same treatment had no effect in noninfected tolerant mice. Collectively, these observations demonstrate that tolerance, even if initially robust, exists as a continuum that can be eroded following bystander immune responses that accompany certain infections.
Assuntos
Rejeição de Enxerto/imunologia , Sobrevivência de Enxerto/imunologia , Transplante de Coração/efeitos adversos , Listeria monocytogenes/imunologia , Listeriose/imunologia , Tolerância ao Transplante/imunologia , Animais , Rejeição de Enxerto/epidemiologia , Rejeição de Enxerto/virologia , Listeriose/virologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Transplante HomólogoRESUMO
Several approaches successfully achieve allograft tolerance in preclinical models but are challenging to translate into clinical practice. Many clinically relevant factors can attenuate allograft tolerance induction, including intrinsic genetic resistance, peritransplant infection, inflammation, and preexisting antidonor immunity. The prevailing view for immune memory as a tolerance barrier is that the host harbors memory cells that spontaneously cross-react to donor MHC antigens. Such preexisting "heterologous" memory cells have direct reactivity to donor cells and resist most tolerance regimens. In this study, we developed a model system to determine if an alternative form of immune memory could also block tolerance. We posited that host memory T cells could potentially respond to donor-derived non-MHC antigens, such as latent viral antigens or autoantigens, to which the host is immune. Results show that immunity to a model nonself antigen, ovalbumin (OVA), can dramatically disrupt tolerance despite undetectable initial reactivity to donor MHC antigens. Importantly, this blockade of tolerance was CD8+ T cell-dependent and required linked antigen presentation of alloantigens with the test OVA antigen. As such, this pathway represents an unapparent, or "incognito," form of immunity that is sufficient to prevent tolerance and that can be an unforeseen additional immune barrier to clinical transplant tolerance.
Assuntos
Apresentação de Antígeno/imunologia , Linfócitos T CD8-Positivos/imunologia , Rejeição de Enxerto/imunologia , Memória Imunológica/imunologia , Transplante das Ilhotas Pancreáticas/métodos , Tolerância ao Transplante/imunologia , Animais , Feminino , Ativação Linfocitária , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Ovalbumina/administração & dosagem , Transplante HomólogoRESUMO
BACKGROUND: Genetically engineered pigs could provide a source of kidneys for clinical transplantation. The two longest kidney graft survivals reported to date have been 136 and 310 days, but graft survival >30 days has been unusual until recently. METHODS: Donor pigs (n=4) were on an α1,3-galactosyltransferase gene-knockout (GTKO)/human complement regulatory protein (CD46) background (GTKO/CD46). In addition, the pigs were transgenic for at least one human coagulation regulatory protein. Two baboons received a kidney from a six-gene pig (GroupA) and two from a three-gene pig (GroupB). Immunosuppressive therapy was identical in all four cases and consisted of anti-thymoglobulin (ATG)+anti-CD20mAb (induction) and anti-CD40mAb+rapamycin+corticosteroids (maintenance). Anti-TNF-α and anti-IL-6R mAbs were administered to reduce the inflammatory response. Baboons were followed by clinical/laboratory monitoring of immune/coagulation/inflammatory/physiological parameters. At biopsy or euthanasia, the grafts were examined by microscopy. RESULTS: The two GroupA baboons remained healthy with normal renal function >7 and >8 months, respectively, but then developed infectious complications. However, no features of a consumptive coagulopathy, eg, thrombocytopenia and reduction of fibrinogen, or of a protein-losing nephropathy were observed. There was no evidence of an elicited anti-pig antibody response, and histology of biopsies taken at approximately 4, 6, and 7 months and at necropsy showed no significant abnormalities. In contrast, both GroupB baboons developed features of a consumptive coagulopathy and required euthanasia on day 12. CONCLUSIONS: The combination of (i) a graft from a specific six-gene genetically modified pig, (ii) an effective immunosuppressive regimen, and (iii) anti-inflammatory therapy prevented immune injury, a protein-losing nephropathy, and coagulation dysfunction for >7 months. Although the number of experiments is very limited, our impression is that expression of human endothelial protein C receptor (±CD55) in the graft is important if coagulation dysregulation is to be avoided.
Assuntos
Rejeição de Enxerto/imunologia , Sobrevivência de Enxerto/imunologia , Transplante de Rim , Rim/cirurgia , Transplante Heterólogo , Animais , Animais Geneticamente Modificados , Rejeição de Enxerto/genética , Sobrevivência de Enxerto/genética , Humanos , Imunossupressores/administração & dosagem , Rim/imunologia , Transplante de Rim/métodos , Papio , Suínos , Transplante Heterólogo/métodos , Transplantes/efeitos dos fármacos , Transplantes/imunologia , Fator de Necrose Tumoral alfa/imunologiaRESUMO
Solid organ transplantation tolerance can be achieved following select transient immunosuppressive regimens that result in long-lasting restraint of alloimmunity without affecting responses to other antigens. Transplantation tolerance has been observed in animal models following costimulation or coreceptor blockade therapies, and in a subset of patients through induction protocols that include donor bone marrow transplantation, or following withdrawal of immunosuppression. Previous data from our lab and others have shown that proinflammatory interventions that successfully prevent the induction of transplantation tolerance in mice often fail to break tolerance once it has been stably established. This suggests that established tolerance acquires resilience to proinflammatory insults, and prompted us to investigate the mechanisms that maintain a stable state of robust tolerance. Our results demonstrate that only a triple intervention of depleting CD25+ regulatory T cells (Tregs), blocking programmed death ligand-1 (PD-L1) signals, and transferring low numbers of alloreactive T cells was sufficient to break established tolerance. We infer from these observations that Tregs and PD-1/PD-L1 signals cooperate to preserve a low alloreactive T cell frequency to maintain tolerance. Thus, therapeutic protocols designed to induce multiple parallel mechanisms of peripheral tolerance may be necessary to achieve robust transplantation tolerance capable of maintaining one allograft for life in the clinic.