Protective effect of CTLA4Ig secreted by transgenic fetal pancreas allografts

BACKGROUND: Pancreas allotransplantation offers a cure for insulin-dependent diabetes mellitus. Systemic immunosuppression used to prevent immune destruction of the graft has side-effects, including increased susceptibility to infection and neoplasia. These unwanted effects may be limited by engineering the graft to secrete immunomodulatory molecules, to achieve local immunosuppression. Several studies have shown that transient local CTLA4Ig results in partial protection of allogeneic grafts. Our intent has been to determine whether sustained secretion of transgenic CTLA4Ig from pancreatic islets is able to protect against allograft rejection. METHODS AND RESULTS: Mouse CTLA4 (test=CTLA4Ig) or CD5 leader sequence (control=CD5LIg) was fused to the Fc of mouse IgG2c, and expressed transgenically under the control of the rat insulin promoter in C57BL/6 mice carrying the bml mutation of H-2K(b) (B6.C-H-2(bm1)). This resulted in expression in pancreatic islets. We used ELISA quantification of transgene products secreted into the supernatants of cultured fetal pancreata to select high (CTLA4Ig(hi)) and low (CTLA4Ig(lo)) expresser transgenic mice. Cultured fetal pancreata were transplanted under the kidney capsule of wholly allogeneic CBA recipient mice. CTLA4Ig(hi) but not CTLA4Ig(lo) expresser grafts showed enhanced survival compared with control CD5LIg grafts at 6 weeks posttransplant, provided the recipient mice were transiently depleted of CD4 T cells (by a single low-dose injection of GK1.5) before transplantation. CONCLUSIONS: Sustained local secretion of CTLA4Ig from transgenic grafts in combination with transient systemic CD4 T-cell depletion can enhance allograft acceptance.     

Prolongation of islet allograft survival by coexpression of CTLA4Ig and CD40LIg in mice

BACKGROUND: B7/CD28 and CD40/CD40L have been well established as important costimulatory pathways. Cytotoxic T lymphocyte-associated antigen-4 (CTLA4) delivers negative signals to antigen-presenting cells to down-regulate proinflammatory responses and competitively inhibits the binding of B7 and CD28. Signals from the CD40/CD40L costimulatory pathway also play an important role in acute rejection of organ grafts. METHODS: Recombinant adenoviruses Ad-sCD40LIg-IRES2-CTLA4Ig, Ad-CTLA4Ig, and Ad-sCD40LIg were constructed to express sCD40LIg and CTLA4Ig simultaneously or separately as described previously. Streptozocin-induced diabetic BALB/c mice were injected with recombinant adenovirus, receiving approximately 500 donor islets isolated from C57BL/6 mice under the left kidney capsule. Five groups were assigned according to the treatment: nontreated group, Ad-Shuttle-CMV-treated group, Ad-CTLA4Ig-treated group, Ad-sCD40LIg-treated group, and Ad-sCD40LIg-IRES2-CTLA4Ig-treated group. The islet graft mean survival time (MST) was evaluated in the present study. RESULTS: Compared to the islet graft MST of the nontreated group (7.3+/-0.82 days) or Ad-Shuttle-CMV-treated group (7.2+/-1.47 days), the Ad-CTLA4Ig-treated and Ad-CD40LIg-treated islet graft survivals in recipients were 56.3+/-13.71 days (P<.01) and 47.3+/-15.64 days (P<.05), respectively. The islet graft MST was dramatically prolonged to 116.3+/-20.32 days in the Ad-sCD40LIg-IRES2-CTLA4Ig-treated group (P<.01). CONCLUSION: Simultaneous blockade of the CD40/CD40L and B7/CD28 costimulatory pathways via coexpression of sCD40LIg and CTLA4Ig mediated by replication-defective adenovirus may be an acceptable method to induce immune tolerance.     

CTLA4Ig基因和CD40Ig基因转染供肾对异种大鼠移植肾存活的影响

目的 探讨细胞毒性T淋巴细胞相关抗原4融合蛋白(CTLA4Ig)基因和CD40Ig基因转染供肾对异种大鼠移植肾存活的影响.方法 以PcDNA3.1质粒为载体,通过脂质体2000将CTLA4Ig基因和CD40Ig基因转染豚鼠肾脏,再移植(异位肾移植)给SD大鼠.实验分4组进行:第1组供肾以PcDNA3.1空载体脂质体复合物转染(空载体组);第2组供肾转染CD40Ig基因(CD40Ig转染组);第3组供肾转染CTLA4Ig基因(CTLA4Ig转染组);第4组供肾同时转染CTLA4Ig基因和CD40Ig基因(双基因转染组).术后观察各组血清肌酐、移植肾组织病理改变以及移植肾存活时间.结果 空载体组、CD40Ig转染组、CTLA4Ig转染组和双基因转染组受者的存活时间分别为(6.8±1.9)d、(40.7±10.9)d、(49.3±9.5)d和(75.7±8.0)d,3个转染组明显长于空载体组(P＜0.01),其中双基因转染组移植肾存活时间最长,与其他3组比较,差异均有统计学意义(P＜0.01).各组术后血清肌酐水平呈上升趋势,但升高幅度以双基因转染组为最低(P＜0.01).术后第30天,CD40Ig转染组和CTLA4Ig转染组存活大鼠的移植肾组织中可见大量淋巴细胞浸润,而双基因转染组的移植肾组织中仅见少量淋巴细胞浸润.结论 供肾局部同时转染CTLA4Ig基因和CD40Ig基因可明显延长其异种移植后的存活时间.     

Bicistronic adenovirus-mediated gene transfer of CTLA4Ig gene and CD40Ig gene result in indefinite survival of islet xenograft

Blockade of CD40-CD154 costimulatory pathway in mice and primates with anti-CD154 monoclonal antibodies results in prolonged survival of vascularized organs and islet grafts. CD40Ig, a recombinant fusion protein comprised of the extracellular domain of human CD40 molecule in frame fused with the site-mutated human IgG1 Fc region, abrogated the cognate interaction of CD40-CD154 pathway by binding the CD154 molecule. In this study, replication-defective adenovirus containing the CD40Ig gene was prepared by homologous recombination and used to infect freshly isolated islets from LEW rats (RT-1(1)) in vitro using a titered dose. The islet transfectants (500 per recipient) were transplanted under the left kidney capsule of streptozocin-rendered diabetic C57BL/6 mouse recipient (H-2(b)). The mean survival time of AdCD40Ig-transfected islet grafts was significantly prolonged, while mock-infected grafts and AdEGFP-transfected grafts were rejected in normal fashion. Additionally, dose-dependent prolongation of islet graft survival was observed in mice receiving AdCD40Ig-transfected grafts. In conclusion, local production of Cd40Ig via adenoviral-mediated gene transfer induced dose-dependent prolongation of LEW --> Balb-c islet xenografts.     

Co-stimulatory molecules in islet xenotransplantation: CTLA4Ig treatment in CD40 ligand-deficient mice

Previous work has demonstrated that short-term systemic administration of cytotoxic T lymphocyte antigen-4 (CTLA-4) Ig blocks human pancreatic islet xenograft rejection in mice and induces long-term, donor-specific tolerance, whereas studies on pig pancreatic islet rejection in mice have failed to demonstrate a role for CTLA4Ig in preventing rejection. Treatment with anti-CD40 ligand (L) monoclonal antibodies alone is somewhat effective in prolonging the survival of islet xenografts, but ineffective when applied to skin xenografts. However, simultaneous blockade of the CD28 and CD40 co-stimulatory pathways prolongs the survival of pig skin on recipient mice. To evaluate the role of CD28 and CD40 co-stimulatory pathways in pig islet-like cell cluster (ICC) xenograft rejection in mice, CD40L-deficient mice transplanted with fetal porcine ICCs were given posttransplant treatment with human (h) CTLA4Ig or a human IgG1 chimeric mAb (hL6). Xenografts were evaluated 6 or 12 days after transplantation. Fetal porcine ICC xenografts were protected from rejection in hCTLA4Ig-treated CD40L-deficient mice, whereas xenograft rejection persisted in untreated CD40L-deficient mice. Simultaneous blockade of the CD28 and CD40 co-stimulatory pathways is mandatory to inhibit ICC xenograft rejection in the pig-to-mouse model, because the CD28 and CD40 co-stimulatory pathways seem capable of efficiently substituting for one another.     

CTLA4Ig introduced by adenovirus vector locally to prolong the survival of xenogeneic skin grafts on rat burn wounds

BACKGROUND: The purpose of this study was to explore an applicable approach for prolonging the survival of heterogenetic skin grafts on burn wounds with CTLA4Ig. METHODS: An adenovirus vector named Ad-CTLA4Ig, which could express human CTLA4Ig fusion protein, was constructed. Infecting and replicating in 293 cells, more Ad-CTLA4Ig and recombinant human CTLA4Ig (rhCTLA4Ig) were prepared, respectively. In a rat flame thermal injury model, the effect of rhCTLA4Ig on survival time of human skin graft on the eschar-excised rat burn wound was observed. Meanwhile, the efficiency of Ad-CTLA4Ig infecting cultured skin fibroblasts, keratinocytes, and partial-thickness skin samples were checked by CTLA4Ig expression essay. Then, the Ad-CTLA4Ig was administered locally on the eschar-excised wound and dermis of the skin graft, and the survival time of the human skin graft on burn wound was measured. The influence of the systemic immune function by rhCTLA4Ig and Ad-CTLA4Ig were also determined. RESULTS: The prepared rhCTLA4Ig from the supernatant of Ad-CTLA4Ig-infected 293 cells was verified by sodium dodecyl sulfate polyacrylamide gel electrophoresis sodium dodecyl sulfate poly-acrylamide gel electrophoresis and Western blot. It was found that CTLA4Ig could significantly prolong the xenogeneic skin graft survival in a dosage-dependent manner. Interestingly, the survival time was longer when CTLA4Ig was used 24 hours posttransplantation than that at hour 0. The expression of CTLA4Ig could be observed in the cultured skin fibroblasts, keratinocytes, and skin pieces soon after Ad-CTLA4Ig transfection, as demonstrated by either immunocellular chemistry or immunohistochemistry assay. When Ad-CTLA4Ig was locally administered during skin transplantation on burn wound, the survival time was increased from 7.9 days of control group to 21.6 days, whereas the systemic immune function was not affected. CONCLUSION: Administration of Ad-CTLA4Ig locally could prolong the survival time of xenogeneic skin graft on burn wound without significantly influencing the systemic immune function.     

Prolongation of renal allograft survival in rats by replication-defective recombinant adenovirus-mediated coexpression of CD40L and CTLA4Ig

BACKGROUND: Blockade of costimulatory signals has been shown to prolong allograft survival. The aim of the present study was to investigate the effect of simultaneous blockade of CD40/CD40L and CD28/B7 costimulatory pathways by replication-defective adenovirus-mediated expression of secretable extracellular domain of human CD40L (shCD40L) and CTLA4Ig to prolong rats renal allograft survival. METHODS: We constructed Adv-shCD40L-IRES2-CTLA4Ig, a replication-defective adenovirus carrying genes encoding human CD40L and CTLA4Ig. Coexpression of shCD40L and CTLA4Ig was evaluated by confocal laser scanning microscopy. The function of these two molecules was examined in human mixed lymphocyte reactions (MLRs) in vitro and in experimental BN-to-LEWIS rat renal transplantation in vivo. RESULTS: Successful construction of Adv-shCD40L-IRES2-CTLA4Ig was confirmed by polymerase chain reaction. Coexpression of shCD40L and CTLA4Ig on human kidney cell line HK-2 cells after transfection was detected by direct immunofluorescence staining. Human MLR was inhibited to 52.2%+/-0.6% and 42.1%+/-0.2% of the vehicle control by Adv-shCD40L and Adv-CTLA4Ig, respectively. Adv-shCD40L-IRES2-CTLA4Ig resulted in further inhibition of MLR to 22.0%+/-0.2% of vehicle control. Transfection with Adv-shCD40L or Adv-CTLA4Ig alone prolonged renal graft survival to 24.8+/-2.5 days and 27.3+/-3.6 days, respectively, as compared to vehicle-treated controls (7.8+/-0.3 days). Cotransfection of both genes extended graft survival to 41.8+/-3.7 days. CONCLUSIONS: Adv-shCD40L-IRES2-CTLA4Ig, a replication-defective adenovirus carrying genes encoding human CD40L and CTLA4Ig, achieved simultaneous blockade of CD40/CD40L and CD28/B7 costimulatory pathways, Adv-shCD40L-IRES2-CTLA4 by Ig synergistically inhibited human T-cell proliferation in MLR, and prolonged rats renal allograft survival.     

Long-term acceptance of rat cardiac allografts on the basis of adenovirus mediated CD40Ig plus CTLA4Ig gene therapies

BACKGROUND: We have previously demonstrated that blockade of either CD80/86-CD28 or CD40-CD154 costimulatory pathways by using adenovirus vector coding CTLA4Ig (AdCTLA4Ig) or CD40Ig (AdCD40Ig) genes induced donor-specific tolerance in rat liver transplantation. In this study, we asked whether these gene-therapy-based costimulation blockade would induce tolerance in cardiac transplantation. METHODS: Heterotopic heart transplantation was performed in a full major histocompatibility complex (MHC) barrier combination of ACI (RT1avl) to Lewis (LEW, RT1l) rats. Vector (1 x 10(9) plaque forming unit [PFU]), AdLacZ, AdCTLA4Ig, or AdCD40Ig, was administered intravenously to recipient animals immediately after grafting, and graft survival, serum CTLA4Ig/CD40Ig levels, and graft histology were assessed. Tolerance was determined by secondary skin-graft challenging. RESULTS: Allografts of both untreated and AdLacZ controls were promptly rejected within 7 days, whereas a single treatment with AdCTLA4Ig or AdCD40Ig significantly prolonged median graft survival to 55.5 and 28.5 days, respectively. In contrast, the combined AdCTLA4Ig and AdCD40Ig gene therapy maintained high CTLA4Ig and CD40Ig levels through the posttransplant period and allowed long-term cardiac allograft survival for more than 270 days. However, both donor and third-party skin grafts were rejected in the animals who harbored cardiac grafts over 150 days. Also, typical features of chronic rejection were evident in the long-term surviving grafts. CONCLUSION: Simultaneous blockade of CD28 and CD154 pathways by AdCTLA4Ig plus AdCD40Ig induces a strong immunosuppression that allows long-term acceptance of full MHC mismatched cardiac graft in rats. This strategy, however, was not enough to induce tolerance to skin grafts and to avoid chronic rejection, as shown in the liver-transplantation model.     

Prevention of Acute Lung Allograft Rejection in Rat by CTLA4Ig

CTLA4 immunoglobulin (CTLA4Ig), which binds with a high affinity to B7-1 and B7-2, interrupts T-cell activation by inhibiting costimulatory signal. CTLA4Ig has been used in hopes of achieving antigen-specific tolerance induction in several solid organ transplants. In lung allograft rejection, however, its use has been controversial in terms of its effect on prevention of rejection. In the present study, the effect of murine CTLA4Ig on rat-lung allograft rejection was investigated. Rat left-lung transplantation was performed in an RT1 incompatible donor (Brown Norway; BN)-recipient (F344) combination. All allografts (n = 12) without any treatment were rejected within 7 days after transplantation. A single injection of murine form CTLA41g at a dose of 100 microg intraperitoneally (ip) or intravenously (iv) on day 1 post-transplantation achieved long-term graft survival (>90days) in 2/5 (40%) and 3/8 (38%), respectively. Moreover, 6/7 (86%) allografts in rats that received iv injection of 500 microg CTLA4Ig survived more than 90days. Allograft survival in the CTLA4Ig 500 microg iv recipient group was significantly longer than that in the no-treatment control or control immunoglobulin group (p <0.01). Four out of seven recipients bearing functional allografts for more than 90 days with the CTLA4Ig treatment accepted donor-specific skin grafts, whereas all third-party skin grafts (n=3) were rejected. Prevention of rat-lung allograft rejection could be achieved by intravenous administration of CTLA4Ig, resulting in long-term allograft survival with acceptance of donor-specific skin grafts.     

Combined gene therapy with adenovirus vectors containing CTLA4Ig and CD40Ig prolongs survival of composite tissue allografts in rat model

BACKGROUND: The blockade of costimulatory signal pathway by anti-CD40 ligand antibody or cytotoxic T lymphocyte antigen 4 immunoglobulin (CTLA4Ig) prolongs allograft survival in various vascularized organ transplantations. Because of the short half life of these agents, repeated administration of proteins is required to achieve significant graft survival. Furthermore, there is limited information regarding the effect of cosimulatory blockade on the survival of composite tissue allografts. Therefore, we examined the effect of adenovirus-mediated gene transfer of CTLA4Ig or CD40Ig gene or both in composite tissue allotransplantation. METHODS: The hind limbs removed from male ACI rats (RT1 ) were transplanted into female Lewis rats (RT1 ) heterotopically. The recombinant adenovirus carrying CTLA4Ig (AxCTLA4Ig) or CD40Ig (AxCD40Ig) was intravenously administered after limb transplantation. RESULTS: Limb allograft survival was significantly prolonged by either AxCTLA4Ig or AxCD40Ig treatment at 1 x 10 plaque forming unit (mean survival time [MST] of 39.4+/-6.0 and 13.0+/-2.9, respectively) compared with the adenovirus vector containing beta-galactosidase-treated group (MST of 4.8+/-0.8). Combination of AxCTLA4Ig and AxCD40Ig led to significant prolongation of graft survival (MST of 49.2+/-6.6). Serum levels of CD40Ig were higher in rats treated with combination therapy than those treated with AxCD40Ig alone, whereas the serum levels of CTLA4Ig in rats treated with AxCTLA4Ig alone and AxCTLA4Ig and AxCD40Ig combined were very similar. CONCLUSION: This study indicates that an adenovirus-mediated gene therapy of CTLA4Ig or CD40Ig has a therapeutic potential for preventing rejection in composite tissue transplantation. Furthermore, a combination therapy of AxCTLA4Ig and AxCD40Ig was even more effective in preventing acute rejection and prolonging the survival of allografted limbs without apparent complication.     

Rapamycin and CTLA4Ig Synergize to Induce Stable Mixed Chimerism Without the Need for CD40 Blockade

The mixed chimerism approach achieves donor‐specific tolerance in organ transplantation, but clinical use is inhibited by the toxicities of current bone marrow (BM) transplantation (BMT) protocols. Blocking the CD40:CD154 pathway with anti‐CD154 monoclonal antibodies (mAbs) is exceptionally potent in inducing mixed chimerism, but these mAbs are clinically not available. Defining the roles of donor and recipient CD40 in a murine allogeneic BMT model, we show that CD4 or CD8 activation through an intact direct or CD4 T cell activation through the indirect pathway is sufficient to trigger BM rejection despite CTLA4Ig treatment. In the absence of CD4 T cells, CD8 T cell activation via the direct pathway, in contrast, leads to a state of split tolerance. Interruption of the CD40 signals in both the direct and indirect pathway of allorecognition or lack of recipient CD154 is required for the induction of chimerism and tolerance. We developed a novel BMT protocol that induces mixed chimerism and donor‐specific tolerance to fully mismatched cardiac allografts relying on CD28 costimulation blockade and mTOR inhibition without targeting the CD40 pathway. Notably, MHC‐mismatched/minor antigen‐matched skin grafts survive indefinitely whereas fully mismatched grafts are rejected, suggesting that non‐MHC antigens cause graft rejection and split tolerance.     

Effects of Gene Transfer CTLA4Ig and Anti-CD40L Monoclonal Antibody on Islet Xenograft Rejection in Mice

Blockade of a costimulatory pathway by adenovirus-mediated cytotoxic T lymphocyte associated antigen 4 immunoglobulin (CTLA4-Ig) gene transfer and anti-CD40L mAb(MR1) have been reported to enhance graft survival in several experimental transplantation models. In this study, we investigated the effects of gene transfer of CTLA4Ig and MR1 on islet xenograft rejection in mice. Recombinant adenovirus AdCTLA4Ig was constructed to express CTLA4Ig. Islet grafts from adult male DA rats transferred with AdCTLA4Ig were transplanted to streptozocin-induced diabetic Balb/c mice. The diabetic mice were treated with MR1 after transplantation. We evaluated the islet xenograft mean survival time as well as changes in interleukin-2 (IL-2) and tumor necrosis factor-alpha (TNF-α) levels in transplanted mice. The mean survival of islet xenografts in the MR1 treatment group was 34.9 ± 5.62 days, in the AdCTLA4Ig treatment group it was 56.5 ± 10.64 days, and in the AdCTLA4Ig plus MR1 treatment group it was 112.9 ± 19.26 days, all significantly prolonged compared with an untreated group (8.1 ± 0.83 days). Within 1 week after transplantation the levels of IL-2 and TNF-α showed sharp increases in the untreated group, being significantly higher than those observed prior to transplantation. In conclusion, using both AdCTLA4Ig and MR1 can improve the islet xenograft survival. The beneficial effects of the combined use of the 2 reagents were superior to either 1 alone, possibly related to down-regulated expression of Th1 cell-related cytokines.     

Feasibility of immunosuppression in composite tissue allografts by systemic administration of CTLA4Ig

BACKGROUND: Although recent experimental studies have demonstrated CTLA4Ig to be a potent immunosuppressant in vascularized solid organ allografts, little attention has been given to the effect of this soluble recombinant fusion protein on immunosuppression in composite tissue allografts (CTAs). Using a rat hind limb allograft model, we examined the efficacy of CTLA4Ig against the allograft rejection of composite tissue. METHODS: The hind limbs of ACI rats (RT1a) were heterotopically transplanted to Lewis rats (RT11). Controls received no immunotherapy. Experimental recipients were treated with a single i.p. injection of either human immunoglobulin (Ig)G (0.5 mg/body) or CTLA4Ig (0.5 mg/body) according to different time schedules. Graft survival time and histopathological changes for each experimental group were evaluated and statistically compared. RESULTS: Graft survival times were prolonged significantly in rats treated with CTLA4Ig on day 1 and day 2 after transplantation, compared with survival times of controls. In particular, the most significant prolongation was found in rats treated on day 2. At 7 days after transplantation, moderate-to-severe histological rejection occurred in all tissues in control rats. On the other hand, in rats treated with CTLA4Ig, all tissues showed significantly better preservation. Among these treated rats, the rats treated on day 2 showed excellent histopathological conditions in each tissue. CONCLUSIONS: This study supports the feasibility of using CTLA4Ig for preventing acute rejection in CTA. On the basis of the current results, the administration of CTLA4Ig for CTA is more effective at 24-48 hr after transplantation, after the initial immune response has been allowed to begin.     

Enhancing engraftment of neonatal porcine xenoislet with CTLA4Ig and nordihydroguaiaretic acid

This study examined the combinatory effect on graft survival of neonatal pig pancreatic cell clusters (NPCC) with nordihydroguaiaretic acid (NDGA), a 5-lipoxygenase inhibitor, with systemic CTLA4Ig expression, with local CTLA4Ig and with interleukin-1 (IL-1) receptor antagonist (IL-1ra) expression using a pig to mouse model. About 2000 NPCCs, which were infected with both adenoviruses carrying CTLA4Ig and IL1-1ra genes (each 500 pfu/NPCC), were transplanted beneath the kidney capsule of diabetic BALB/c mice. Two days before transplantation, the recipient mice were either injected with (group C, n = 4; group D, n = 6) or without (group A, n = 7; group B, n = 9) 1 x 10(13) pfu/kg body weight of adenovirus carrying the CTLA4Ig gene. Mice in groups B and D received daily injections of NDGA (20 mg/kg body weight) subcutaneously for 4 weeks. Blood glucose levels less than 200 mg/dL were defined to be normoglycemic and the transplant termed as a functioning graft for the purpose of calculating mean graft function time (MFT). Four weeks posttransplantation, an intraperitoneal glucose tolerance test (IPGTT) was performed to calculate the area under the curve (AUC). Blood glucose levels in groups C and D were significantly lower than groups A and B at 1, 2, and 3 weeks after transplantation. Graft MFT and AUC of IPGTT in group D were significantly different from those in groups A and B. Our data suggested that a high dosage of systemic expression of CTLA4Ig was effective to enhance xenograft survival and that in it was reinforced by a combination with the macrophage inhibitor NDGA.     

Adenovirus-mediated CTLA4Ig or CD40Ig gene transfer delays pancreatic islet rejection in a rat-to-mouse xenotransplantation model after systemic but not local expression

Transient costimulation signal blockade of either CD28/CD80-86 interactions and/or CD40/CD154 interactions can prevent islet rejection in some models of both allo- and xenotransplantation. We have used adenoviruses coding for CTLA4Ig or CD40Ig and compared the efficacy of genetic modification of islets to systemic production through either intramuscular (i.m.) or intravenous (i.v.) injection of these vectors in a rat-to-mouse islet transplantation model. When gene transfer was performed into islets, a high level of primary nonfunction was induced. Furthermore, transduced functional grafts were rejected with the same kinetics as nontransduced islets. In contrast, i.m. AdCTLA4Ig and i.v. AdCD40Ig significantly delayed rejection (mean survival time of 54 +/- 26.9 and 67.6 +/- 44.9 days, respectively, vs. 24.3 +/- 9.7 days for unmodified islets, p < 0.05). Combination of ex vivo AdCTLA4Ig islet transduction and i.v. AdCD40Ig did not improve graft survival further. In conclusion, islet graft transduction with adenoviruses coding for costimulation inhibitors resulted in local expression with low serum concentrations of CTLA4Ig or CD40Ig and was unable to protect islet xenografts from rejection. In contrast, i.m. or i.v. gene transfer resulted in high serum concentrations of these molecules and was highly efficient in prolonging xenograft survival. These results contrast with the efficacy of AdCTLA4Ig we observed in a rat islet allotransplantation model and suggest that islet xenograft rejection might be more difficult to control.     

腺病毒载体介导的CTLA4Ig基因追踪臂丛神经通路的研究

目的 利用腺病毒载体(Ad)介导的CTLA4Ig基因示踪大鼠臂丛神经轴突及其运动和感觉神经元,探讨转基因产物CTLA4Ig蛋白作为神经通路示踪剂的可行性及其特点.方法 经正中神经或尺神经或肌皮神经近断端导入携带CTLA4Ig或增强型绿色荧光蛋白(EGFP)基因的Ad(各2×107pfu).在转染后3周内6个不同时间点取标本,行CTLA41g免疫荧光染色,观察标记的运动及感觉神经元所在脊髓和脊髓后根神经节(DRGs)节段、神经根及轴突被标记范围及时间,并与EGFP基因的示踪结果比较.结果 由正中神经、尺神经和肌皮神经所标记的神经元分别在C6～Th1、c7～Th1及C5～C7节段;其相应的神经根及神经干近段轴突亦被标记.CTLA4Ig标记的神经元在转染3周后消失,所标记神经干轴突在转染5周后消失;而EGFP所标记的神经元和神经干分别2周、3周后消失.结论 CTLA4Ig基因能在Ad介导下经外周逆行性、特异性示踪臂丛神经及其靶运动和感觉神经元.     

Local expression of IDO, either alone or in combination with CD40Ig, IL10 or CTLA4Ig, inhibits indirect xenorejection responses

Abstract: Background: To overcome cell‐mediated xenorejection by transgenic expression of immunomodulatory molecules by a graft, it is likely that expression of multiple molecules will be required. Previous studies support the use of the immunomodulatory agents indoleamine 2,3‐dioxygenase (IDO), CD40Ig, interleukin 10 (IL10), and CTLA4Ig for suppression of rejection responses. We examined the effects of local expression of these molecules by a porcine cell line (PIEC) on indirect murine xenorejection responses in vitro and in vivo. Methods: The PIEC stable lines expressing IDO, CD40Ig, and IL10 as single molecules were generated. In addition, PIEC lines expressing IDO with either CD40Ig, IL10 or CTLA4Ig were generated to produce cell lines expressing two molecules. BALB/c mice were primed with wild type PIEC, followed by harvesting splenocytes used as responder cells and PIEC expressing immunomodulatory molecules as stimulators, in proliferation and cytokine assays. In vivo effects of modified PIEC were examined by transplantation of PIEC lines expressing the immunomodulatory molecules under the renal capsule of naïve mice. PIEC grafts were harvested for histological evaluation at days 7 and 14. Results: Proliferation of primed BALB/c splenocytes was inhibited most significantly by IDO compared with control cells (49%, P = 0.02). In addition both Th1 (interferon‐gamma) and Th2 (IL4 and IL10) cytokines were markedly inhibited in vitro by IDO expression. IL10 expressing cells did not inhibit proliferation as potently (37%, P = 0.03) whilst CD40Ig lead to an increase in proliferative responses (59%, P = 0.02). Co‐expression of CD40Ig, IL10, and CTLA4Ig with IDO resulted in further modest reductions in proliferation compared with IDO expression alone. When transplanted under the renal capsule of BALB/c mice, those grafts expressing IDO demonstrated significantly lower levels of lymphocyte infiltration at days 7 and 14 than control grafts and those expressing CD40Ig, CTLA4Ig or IL10 alone. Grafts co‐expressing IDO and a second molecule were no better protected than those expressing IDO alone. Graft cell viability (PIECs) was reduced in some IDO expressing grafts suggesting high levels of IDO expression may inhibit PIEC viability, however, grafts co‐expressing IDO‐CTLA4Ig and IDO‐IL10 were not affected in this way. Conclusion: Indoleamine 2,3‐dioxygenase appears to be a potent molecule for protecting xenografts from cell‐mediated rejection responses activated via the indirect pathway. Co‐expression of IDO with both CTLA4Ig and IL10 warrants further investigation. Overall these findings support pursuing further studies, in larger animal models, to determine whether increased IDO activity within the graft itself can attenuate xenorejection responses.     

CD40 blockade combines with CTLA4Ig and sirolimus to produce mixed chimerism in an MHC-defined rhesus macaque transplant model

In murine models, T-cell costimulation blockade of the CD28:B7 and CD154:CD40 pathways synergistically promotes immune tolerance after transplantation. While CD28 blockade has been successfully translated to the clinic, translation of blockade of the CD154:CD40 pathway has been less successful, in large part due to thromboembolic complications associated with anti-CD154 antibodies. Translation of CD40 blockade has also been slow, in part due to the fact that synergy between CD40 blockade and CD28 blockade had not yet been demonstrated in either primate models or humans. Here we show that a novel, nondepleting CD40 monoclonal antibody, 3A8, can combine with combined CTLA4Ig and sirolimus in a well-established primate bone marrow chimerism-induction model. Prolonged engraftment required the presence of all three agents during maintenance therapy, and resulted in graft acceptance for the duration of immunosuppressive treatment, with rejection resulting upon immunosuppression withdrawal. Flow cytometric analysis revealed that upregulation of CD95 expression on both CD4+ and CD8+ T cells correlated with rejection, suggesting that CD95 may be a robust biomarker of graft loss. These results are the first to demonstrate prolonged chimerism in primates treated with CD28/mTOR blockade and nondepletional CD40 blockade, and support further investigation of combined costimulation blockade targeting the CD28 and CD40 pathways.