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Abstract: Background: Safety concerns exist for corneal recipients under immunosuppression. We report long‐term safety results of porcine corneal xenotransplantation under immunosuppression in nonhuman primates. Methods: Systemic monitoring data from 49 Chinese rhesus macaques that received pig corneal transplant between 2009 and 2018 were retrospectively reviewed. The recipients were divided into 4 groups depending on the systemic immunosuppressants used: (a) conventional steroid group; costimulation blockade groups ([b] anti‐CD154 antibody, [c] anti‐CD40 antibody); and (d) commercially available immunosuppressants (anti‐CD20 antibody, tacrolimus, basiliximab) group. We compared results of general condition monitoring; hematologic, biochemical, and electrolyte tests; and Rhesus Cytomegalovirus infection monitoring. Results: All recipients recovered from early weight loss. White blood cell counts significantly decreased at 6 months in the steroid and anti‐CD154 groups. Abnormal liver and kidney function and electrolyte imbalance were not observed in all groups. The mean value of Rhesus Cytomegalovirus DNA copies was consistently lower than 200 copies/mL, and antibody titers did not change over time in all groups. Tacrolimus‐associated thrombotic microangiopathy was developed in one case, which resolved after discontinuation of tacrolimus. In 2017, a simian varicella virus outbreak led to clinical signs in 5 that received immunosuppressive therapies, of which 3 died. Conclusion: Costimulatory blockade‐based and anti‐CD20 antibody/tacrolimus‐based immunosuppressive therapies seem to be comparably safe with steroid therapy in nonhuman primates receiving corneal xenotransplantation, as they did not reactivate Rhesus Cytomegalovirus and maintained manageable systemic status. Although reactivation is rare, antiviral prophylaxis for simian varicella virus should be considered in immunocompromised hosts. [ABSTRACT FROM AUTHOR]

Abstract: Background: Pig islet xenotransplantation is a promising alternative to allogeneic transplantation. However, the wide immunologic barrier between pigs and primates limits the long‐term survival of the graft. MD‐3, a novel monoclonal antibody (mAb) that recognizes a particular epitope of human ICAM‐1, can render T cells tolerant to a xenograft by arresting dendritic cell maturation. We report the long‐term survival of adult wild‐type pig islets and successful retransplantation in nonhuman primates using a protocol comprising induction with MD‐3 mAb and maintenance with anti‐CD154 mAb and sirolimus. Methods: Eleven rhesus monkeys were assigned to three groups. Group 1 (n = 4) involved treatment with MD‐3 induction, short‐term (<4 months) administration of anti‐CD154 mAb, and maintenance therapy with sirolimus. Group 2 (n = 4) involved treatment with MD‐3 induction and long‐term maintenance therapy with anti‐CD154 mAb and sirolimus. Group 3 (n = 3) involved only maintenance therapy with anti‐CD154 mAb and sirolimus. Diabetes was induced in monkeys by streptozotocin, and pig islets (61 000‐112 000 IEQ/kg for each transplant; up to 280 000 IEQ/kg per recipient) were infused through the portal vein. The in vivo functional potency of the isolated islets was tested by minimal model transplant in streptozotocin‐induced diabetic NOD/SCID mice, and the mean AUC of blood glucose level divided by the number of follow‐up days was calculated. Results: The islet grafts survived more than 6 months (between 225 and 727 days) in nine of 12 transplants of MD‐3‐treated groups 1 and 2, whereas in the absence of MD‐3 mAb, survival was <40 days. In three transplants of the MD‐3‐treated Group 2, functional graft survival was only for 104, 125, and 154 days. In these cases, a retrospective analysis suggested that the relatively short survival duration was associated with the relatively high AUC value in the NOD/SCID bioassay. Notably, when retransplantation was performed in Group 3, blood glucose control was extended up to 956 days, which was supported by MD‐3 mAb‐based suppression of adaptive immunity. No replication of cytomegalovirus genes was observed. Conclusions: Long‐term survival of pig islet xenografts and successful retransplantation were achieved with MD‐3 mAb‐based immunosuppression regimen in this pig‐to‐monkey transplantation model. It should be emphasized that these encouraging results were achieved following the transplantation of islets from pigs that had not been genetically modified. Considering that it is possible to further substantially reduce the destruction of grafted islet using genetically modified pig islet, the islet requirement could be reduced and much longer graft survival can be achieved. [ABSTRACT FROM AUTHOR]

Abstract: Background: Islet transplantation is an effective therapy for selected patients with type 1 diabetes with labile glycemic control and hypoglycemic unawareness, but donor organs are limited. Islet xenotransplantation using porcine islets will potentially solve this problem. Although successful proof of concept studies using clinically inapplicable anti‐CD154 monoclonal antibody (mAb) in pig‐to‐non‐human primate (NHP) islet xenotransplantation has been demonstrated by several groups worldwide, potentially clinically applicable anti‐CD40 (2C10R4) mAb‐based studies have not been reported. Methods: Nine streptozotocin (STZ)‐induced diabetic rhesus monkeys were transplanted with adult porcine islets isolated from designated pathogen‐free (DPF) miniature pigs. They were treated with anti‐CD40 mAb‐based immunosuppressive regimen and were divided into 3 groups: anti‐CD40 only group (n = 2), belatacept group (anti‐CD40 mAb+belatacept, n = 2), and tacrolimus group (anti‐CD40 mAb+tacrolimus, n = 5). All monkeys received anti‐thymocyte globulin (ATG), cobra venom factor (CVF), adalimumab, and sirolimus. Blood glucose levels (BGL) and serum porcine C‐peptide concentrations were measured. Humoral and cellular immune responses were assessed by ELISA and ELISPOT, respectively. Liver biopsy and subsequent immunohistochemistry were conducted. Results: All animals restored normoglycemia immediately after porcine islet transplantation and finished the follow‐up without any severe adverse effects except for one animal (R092). Most animals maintained their body weight. Median survival, as defined by a serum porcine C‐peptide concentration of >0.15 ng/mL, was 31, 27, and 60 days for anti‐CD40 only, belatacept, and tacrolimus groups, respectively. Anti‐αGal IgG levels in serum and the number of interferon‐γ secreting T cells in peripheral blood mononuclear cells did not increase in most animals. Conclusion: These results showed that anti‐CD40 mAb combined with tacrolimus was effective in prolonging porcine islet graft survival, but anti‐CD40 mAb was not as effective as anti‐CD154 mAb in terms of preventing early islet loss. [ABSTRACT FROM AUTHOR]

Background Corneal xenotransplantation is an effective solution for the shortage of human donor corneas, and the porcine cornea may be a suitable candidate for the donor cornea because of its optical similarity with humans. However, it is necessary to administer additional immunosuppressants to overcome antigenic differences. We aimed to investigate the feasibility of porcine corneas with anti- CD40 antibody-mediated costimulation blockade in a clinically applicable pig-to-non-human primate corneal xenotransplantation model. Methods Five Chinese rhesus macaques underwent deep-lamellar corneal transplantation using clinically acceptable sized (7.5 mm diameter) porcine corneal grafts. The anti- CD40 antibody was intravenously administered on a programmed schedule. Graft survival, central corneal thickness, and intraocular pressure were evaluated. Changes in effector and memory T and B cell subsets and anti-αGal and donor-specific antibodies were investigated in the blood, and the changes in complement levels in the aqueous humor and blood were evaluated. Memory cell profiles in the anti- CD40 antibody-treated group were compared with those from the anti- CD154 antibody-treated group or rejected controls presented in our previous report. The changes in anti-αGal, non-αGal, and donor-specific antibodies after 6 months were compared with baseline values. Results Anti- CD40 antibody-mediated costimulation blockade resulted in the successful survival of xenocorneal grafts (>389, >382, >236, >201, and >61 days), with 80% reaching 6 months of survival. Injection of anti- CD40 antibody considerably reduced the infiltration of inflammatory cells into the grafts and significantly blocked the complement response in the aqueous humor ( P=.0159, Mann-Whitney U test). Systemic expansion of central or effector memory T cells was abrogated in the anti- CD40 antibody-treated primates compared with those in the rejected controls ( P<.05, Mann-Whitney U test) or those in the anti- CD154 antibody-treated primates ( P>.05, Mann-Whitney U test). The levels of anti-αGal, non-αGal, and donor-specific antibodies at 6 months were not significantly increased compared with baseline levels ( P>.05, Wilcoxon signed rank test). Conclusions An anti- CD40 antibody-mediated blockade appears to be effective immunosuppressive approach for porcine corneal deep-lamellar xenotransplantation in primates. [ABSTRACT FROM AUTHOR]

Background Xenotransplantation represents one of alternative candidates for allotransplantation due to the chronic shortage of suitable human tissues; however, many obstacles remain. Expression and release of endogenous retroviral antigens by porcine cells after transplantation may evoke adverse immune responses in human subjects. Here, we examined whether human herpesvirus 1 ( HHV-1) could induce the production of porcine endogenous retrovirus ( PERV) antigens in porcine peripheral blood mononuclear cells ( PBMCs). Methods Porcine PBMCs were infected with HHV-1 and examined for the production of PERV Gag protein and HHV-1 using antigen-capture ELISA and quantitative real-time polymerase chain reaction ( PCR), respectively. Results HHV-1 infection resulted in a 1.7- to 33.2-fold induction of PERV Gag relative to mock infection controls, compared to a 2.9- to 12.9-fold induction following treatment with PMA. Expression of PERV Gag was detected in porcine PBMCs and PK-15 cells after HHV-1 infection by double immunofluorescence staining of PERV Gag and HHV-1 antigen. The viability of HHV-1-infected porcine PBMCs was significantly lower than that of mock-infected cells. The HHV-1 level in the culture supernatant increased 5.2-fold relative to controls 24-h post-infection, indicative of active replication within these cells; decreased levels of HHV-1 were detected 72-h post-infection. Conclusions These results suggest that HHV-1 may be capable of infecting transplanted porcine cells, resulting in strong direct induction of PERV antigen. [ABSTRACT FROM AUTHOR]

To develop an international consensus regarding the appropriate conditions for undertaking clinical trials in xenocorneal transplantation, here we review specific ethical, logistical, scientific, and regulatory issues regarding xenocorneal transplantation, and propose guidelines for conduct of clinical xenocorneal transplantation trials. These proposed guidelines are modeled on the published consensus statement of the International Xenotransplantation Association regarding recommended guidelines for conduct of clinical islet xenotransplantation. It is expected that this initial consensus statement will be revised over time in response to scientific advances in the field, and changes in the regulatory framework based on accumulating clinical experience. [ABSTRACT FROM AUTHOR]

Jin S-M, Shin JS, Kim KS, Gong C-H, Park SK, Kim J-S, Yeom S-C, Hwang ES, Lee CT, Kim S-J, Park C-G. Islet isolation from adult designated pathogen-free pigs: use of the newer bovine nervous tissue-free enzymes and a revised donor selection strategy would improve the islet graft function. Xenotransplantation 2011; 18: 369-379. © 2011 John Wiley & Sons A/S. Abstract: Background: In clinical trials using adult porcine islet products, islets should be isolated from the designated pathogen-free (DPF) pigs under the current good manufacturing practice (GMP) regulations. Our previous studies suggested that male DPF pigs are better donors than retired breeder pigs and histomorphometrical parameters of donor pancreas predict the porcine islet quality. We aimed to investigate whether the use of the newer bovine nervous tissue-free enzymes and a revised donor selection strategy could improve the islet graft function in the context of islet isolation with DPF pigs. Methods: Using 30 DPF pigs within a closed herd, we compared the islet yield of porcine islets isolated with Liberase PI (n = 11, as a historical control group), Liberase MTF C/T, which is a GMP-grade enzyme (n = 12), and CIzyme collagenase MA/BP protease (n = 7). We analyzed the relationship between the diabetes reversal rate of recipient NOD/SCID mice (n = 75) and histomorphometric parameters of each donor pancreas as well as donor characteristics. Results: Proportion of islets larger than 200 μm from the biopsied donor pancreas (P = 0.006) better predicted islet yield than age (P = 0.760) or body weight (P = 0.371) of donor. The proportion of islets larger than 200 μm from the biopsied donor pancreas was not related to the sex of the donor miniature pig (P = 0.358). The islet yield obtained with the three enzymes did not differ, even after stratification of the donor with the histomorphometric parameters of the biopsied donor pancreas and the sex of donor. The use of the newer bovine nervous tissue-free enzymes (P < 0.001), a higher proportion of large islets in donor pancreas (P = 0.006), and a male sex of the donor (P = 0.025) were independent predictors of earlier diabetes reversal. Conclusions: Use of the newer bovine nervous tissue-free enzymes including a GMP-grade enzyme resulted in better islet quality than that of islet isolated using Liberase PI. To obtain high-quality islet from DPF pigs, the donor should be male pig and histomorphometrical parameters from donor pancreas should be considered. [ABSTRACT FROM AUTHOR]