Lack of antibody production against Hanganutziu-Deicher (H-D) antigens with N-glycolylneuraminic acid in patients with porcine exposure history

The significance of non-alphagalactosyl antigens remains unclear in pig-to-primate xenotransplantation. Hanganutziu-Deicher (H-D) antigens with terminal N-glycolylneuraminic acid (NeuGc) are widely expressed on endothelial cells of mammalian species, with the exception of humans. As baboons and monkeys also express H-D antigens, a pig-to-non-human primate experimental model cannot resolve the question of whether H-D antigens can elicit a potent humoral response in human recipients. The purpose of this study was to elucidate the clinical significance of H-D antigens by examining the sera from patients who have been previously exposed to porcine tissue. After the digestion of porcine aortic endothelial cells (PAEC) by neuraminidase, NeuGc and N-acetylneuraminic acid (NeuAc) were quantitated by HPLC. IgG and IgM antibody levels against H-D antigens were measured by NeuGc-GM3-coated ELISA plates in the sera of patients who had undergone ex vivo kidney perfusion 1 to 3 weeks and 2 years previously (n=2) or had been injected with fetal porcine islets 2 months previously (n= 10). HPLC determined that 9.7x 10(7) NeuAc and 6.3x 10(7) NeuGc residues per cell were released from PAEC by neuraminidase, while 25.7x 10(7) NeuAc and an undetectable level of NeuGc were released from human aortic endothelial cells (HAEC). No significant elevation of IgG or IgM antibody levels against NeuGc-GM3 was observed in sera from patients with a history of porcine exposure. Considering the active production of antibody against the foreign galactosyl antigens after pig-to-human xenotransplantation, some production of antibodies against the equally foreign H-D antigens would be expected, because large amounts of NeuGc terminated saccharides are present in the pig endothelial cell surface. However, no production of antibodies directed to H-D antigens could be found in patients exposed to porcine tissue. Further studies are warranted to explain why H-D antigens do not elicit a significant antibody production.

Historic landmarks in clinical transplantation: conclusions from the consensus conference at the University of California, Los Angeles

The transplantation of organs, cells, and tissues has burgeoned during the last quarter century, with the development of multiple new specialty fields. However, the basic principles that made this possible were established over a three-decade period, beginning during World War II and ending in 1974. At the historical consensus conference held at UCLA in March 1999, 11 early workers in the basic science or clinical practice of transplantation (or both) reached agreement on the most significant contributions of this era that ultimately made transplantation the robust clinical discipline it is today. These discoveries and achievements are summarized here in six tables and annotated with references.

Damage to porcine islets of Langerhans after exposure to human blood in vitro, or after intraportal transplantation to cynomologus monkeys: protective effects of sCR1 and heparin

BACKGROUND

Porcine islets offer an attractive alternative to human islets in clinical islet transplantation. The preferred method of islet transplantation is intra-portal injection into the liver. We have recently shown, both in vitro with human islets and in vivo with porcine islets, that islets exposed to allogeneic blood trigger an injurious inflammatory reaction characterized by activation of both coagulation and the complement systems. We have now tested whether a similar reaction is triggered when xenogeneic porcine islets are exposed to human blood in vitro and after intraportal transplantation into primates. Furthermore, we investigated the effect of inhibiting the complement and coagulation systems.

METHOD

Islets isolated from adult and fetal porcine pancreas were perfused with fresh human blood in surface heparinized PVC tubings for 5-60 min. Blood cell counts and parameters related to coagulation and the complement system were analyzed, and islets were retrieved after the perifusion was examined by immunohistochemical method. Heparin and soluble complement receptor 1 (sCR1; TP10, 100 microg/ml) were added to the system in some experiments. Furthermore, adult porcine islets were transplanted intraportally into untreated and sCR1- (40 mg/kg BW i.v.) treated cynomolgus monkeys, and plasma insulin concentration was monitored during 60 min after transplantation.

RESULTS

Porcine islets perifused with human blood triggered an immediate inflammatory reaction, characterized by a rapid consumption and activation of platelets, consumption of neutrophils and monocytes, activation of the coagulation and complement systems, and release of large amounts of insulin. Islet morphologic analysis revealed damaged islets embedded in clots and infiltrated with CD11+ leukocytes. C3a and C5b-9 was deposited on the islet surface, but human immunoglobulin was not. Complement inhibition with sCR1 reduced insulin release significantly. Intraportal islet transplantation into untreated cynomolgus monkeys resulted in a marked and rapid increase in plasma insulin concentration indicative of islet damage. Pretreatment of the monkeys with sCR1 resulted in significantly less insulin release than in untreated control monkeys.

CONCLUSION

Exposure of isolated xenogeneic islets of Langerhans to blood, both in vitro and in vivo, resulted in acute islet damage. Complement and platelets seem to have a central role in the reactions described. Strategies to efficiently inhibit these reactions will be crucial for clinical intraportal islet xenotransplantation to be successful.

Isolated human islets trigger an instant blood mediated inflammatory reaction: implications for intraportal islet transplantation as a treatment for patients with type 1 diabetes

Islet transplantation offers a logical means to treat insulin-dependent diabetes. However, for reasons poorly understood, the clinical results with islet transplantation have been vastly inferior to those obtained with whole organ pancreas transplantation. The conventional technique for transplanting isolated islets is by intraportal injection, with the islets being trapped in the liver. Human islets exposed to human blood trigged an "instant blood mediated inflammatory reaction", IBMIR, characterised by platelet consumption, and activation of the coagulation and complement systems. The islets became surrounded by clots and infiltrated with leukocytes, and there was evidence of islet damage as reflected in insulin dumping. When heparin and a complement inhibitor (SCRI), was added to the system, IBMIR was suppressed and islet damage reduced. After intraportal pig-to-pig islet intraportal allotransplantation similar morphological changes was found, corroborating the in vitro findings. Thus, IBMIR inflicts a significant damage to human islets exposed to human blood and IBMIR will also, most likely, enhance the subsequent specific, cell mediated, rejection. Platelet and complement activation seem to be the most important factors in the pathogenesis of IBMIR. The results presented strongly suggest that IBMIR observed both in vitro and in vivo when isolated islets come in contact with blood could provide an explanation for the unsatisfactory results seen in clinical islet allotransplantation.

Incompatibility between human blood and isolated islets of Langerhans: a finding with implications for clinical intraportal islet transplantation?

The remarkable difference in success rates between clinical pancreas transplantation and islet transplantation is poorly understood. Despite the same histocompatibility barrier and similar immunosuppressive treatments in both transplantation procedures, human intraportal islet transplantation has a much inferior success rate than does vascularized pancreas transplantation. Thus far, little attention has been directed to the possibility that islets transplanted into the blood stream may elicit an injurious incompatibility reaction. We have tested this hypothesis in vitro with human islets and in vivo with porcine islets. Human islets were exposed to nonanticoagulated human ABO-compatible blood in surface-heparinized polyvinyl chloride tubing loops. Heparin and/or the soluble complement receptor 1 (sCR1) TP10 were tested as additives. Adult porcine islets were transplanted intraportally into pigs, and the liver was recovered after 60 min for immunohistochemical staining. Human islets induced a rapid consumption and activation of platelets. Neutrophils and monocytes were also consumed, and the coagulation and complement systems were activated. Upon histological examination, islets were found to be embedded in clots and infiltrated with CD11+ leukocytes. Furthermore, the cellular morphology was disrupted. When heparin and sCR1 were added to the blood, these events were avoided. Porcine islets retrieved in liver biopsies after intraportal islet allotransplantation showed a morphology similar to that of human islets perifused in vitro. Thus, exposure of isolated islets of Langerhans to allogenic blood resulted in significant damage to the islets, a finding that could explain the unsatisfactory clinical results obtained with intraportal islet transplantation. Because administration of heparin in combination with a soluble complement receptor abrogated these events, such treatment would presumably improve the outcome of clinical islet transplantation by reducing both initial islet loss and subsequent specific immune responses.

Tacrolimus whole blood concentrations correlate closely to side-effects in renal transplant recipients

AIMS

To evaluate the relationship between tacrolimus whole blood concentrations and side-effects and rejections in 14 renal transplant recipients.

METHODS

Tacrolimus was measured by MEIA in whole blood in samples collected repeatedly during the first year after transplantation. Retrospectively, tacrolimus trough concentrations on the days with adverse events (n=172) or rejection (n=28) were related to the total distribution of the concentration values (n=656).

RESULTS

Side-effects (one or more) were noted in connection with 76% of tacrolimus concentrations above 30 ng ml-1, with 41% of concentrations within the interval of 20-30 ng ml-1, with 26% of the concentrations within the interval of 10-20 ng ml-1 and with only 5.3% on the concentrations lower than 10 ng ml-1. No relation to the tacrolimus concentration was seen for rejection episodes.

CONCLUSIONS

We conclude that therapeutic drug monitoring may be helpful in the management of tacrolimus therapy and that tacrolimus whole blood trough concentrations (MEIA) should preferably be kept below 20 ng ml-1 to avoid side-effects, such as nephro-and neurotoxicity and infections. The lower limit of the therapeutic range has yet to be defined.

Sirolimus (rapamycin)-based therapy in human renal transplantation: similar efficacy and different toxicity compared with cyclosporine. Sirolimus European Renal Transplant Study Group

BACKGROUND

Sirolimus (rapamycin) is a potent immunosuppressant with a mechanism of action different from cyclosporine (CsA) or tacrolimus.

METHODS

In 11 European centers, first cadaveric renal allograft recipients were randomized to CsA (n=42) or sirolimus (n=41). Dosing of these agents was concentration-controlled and open-labeled. All patients received corticosteroids and azathioprine.

RESULTS

At 12 months, graft survival (98% sirolimus vs. 90% CsA), patient survival (100% vs. 98%), and incidence of biopsy-confirmed acute rejection (41% vs. 38%) were similar. Serum creatinine was lower with sirolimus, significantly (P< or =0.05) so at 3 and 4 months, and serum uric acid and magnesium were normal. Laboratory abnormalities reported significantly more often with sirolimus included hypertriglyceridemia (51% vs. 12%), hypercholesterolemia (44% vs. 14%), thrombocytopenia (37% vs. 0%), leukopenia (39% vs. 14%), and, of lesser importance, increased liver enzymes and hypokalemia. These abnormalities improved 2 months after transplantation when the sirolimus target trough level was lowered from 30 to 15 ng/ml. Occurrence of cytomegalovirus was comparable (14% vs. 12%); incidences of herpes simplex (24% vs. 10%, P=0.08) and pneumonia (17% vs. 2%, P=0.03) were higher with sirolimus. No gingival hyperplasia was seen with sirolimus, tremor was rare, and hypertension was less frequent (17% vs. 33%). Two malignancies were observed with CsA and none with sirolimus.

CONCLUSIONS

Results at 12 months suggest that sirolimus can be used as base therapy in the prophylaxis of acute renal transplant rejection, and has a safety profile that differs from CsA.

Fetal porcine islet-like cell clusters transplanted to cynomolgus monkeys: an immunohistochemical study

BACKGROUND

The mechanism(s) involved in acute cellular xenograft rejection have hitherto been generated in vitro or in different experimental models, with pig tissue being transplanted to rodents. There is an urgent need to validate these results in a clinically more relevant combination of species.

METHODS

Fetal porcine islet-like cell clusters (ICC) were transplanted under the kidney capsule in cynomolgus monkeys, either untreated or given immunosuppression with cyclosporine (CsA; 10 mg/kg body weight, intramuscularly) and 15-deoxyspergualin (DSG; 5 mg/kg body weight, intramuscularly). ICC xenografts were examined at 1, 3, 6, or 10-12 days after transplantation, using immunohistochemical techniques. Serum levels of xenoreactive antibodies were measured with ELISA.

RESULTS

No deposits of IgM, IgG, Clq, or C3 were detected within the ICC xenograft in any of the monkeys. Likewise, no significant increase in the levels of xenoreactive antibodies were found after transplantation. In untreated animals, a few N-Elastase-positive cells (neutrophil granulocytes) were seen in the xenograft at day 1. A few mononuclear cells were present in the adjacent renal parenchyma, but they did not infiltrate the xenograft. At this time (day 1), early signs of necrosis were observed in the central parts of the graft. On day 3, the graft had a large, central necrotic area that contained polymorphonuclear cells; the remaining parts of the xenograft showed severe infiltration with CD8+ T cells. Occasional CD68+ cells (macrophages) were seen on days 1 and 3. On day 6, large numbers of macrophages were found infiltrating the entire graft. A few CD20+ B cells, accumulated as small clusters, were also found. Only a few natural killer cells (CD56+) were detected. The CsA/DSG-treated monkeys showed markedly fewer CD2+/CD8+ T cells on day 6 than the untreated monkeys, and the ICC graft was clearly better preserved. However, the number of CD8+ and CD68+ cells had increased considerably at 12 days after transplantation and diffusely infiltrated the whole ICC xenograft.

CONCLUSION

Porcine ICC transplanted under the kidney capsule in cynomolgus monkeys were rejected by an acute cell-mediated rejection progressing during the first 6 days after transplantation. The process was not dependent on host Ig or C3 binding to the graft. Although the rejection of porcine ICC was significantly delayed in CsA/DSG-treated monkeys, the ICC xenografts were almost completely destroyed 12 days after transplantation.

Improved survival in patients with insulin-dependent diabetes mellitus and end-stage diabetic nephropathy 10 years after combined pancreas and kidney transplantation

BACKGROUND

The purpose of pancreatic transplantation in insulin-dependent diabetic patients is to restore normoglycemia and thereby prevent the secondary complications of diabetes. However, uncertainty remains as to whether the mortality rate in diabetic patients can be affected by this procedure.

METHOD

We followed 14 patients with insulin-dependent diabetes mellitus (IDDM) and end-stage diabetic nephropathy for 10 years after successful combined kidney and pancreas transplantation. Fifteen diabetic patients subjected to kidney transplantation alone have served as controls. The glycemic control has been studied annually for 10 years and diabetic polyneuropathy has been assessed in both groups after 2, 4, and 8 years.

RESULTS

In recipients of pancreas-kidney grafts, metabolic control was maintained throughout the observation period, with values of glycated hemoglobin in the normal range. In contrast, glucose metabolism was impaired in the control group, with glycated hemoglobin values around 10%. Nerve conduction and parasympathetic autonomic dysfunction improved in both groups after 2 years; there was no difference between the groups. After 4 years, we found a significant difference between the study group and the control group, and after 8 years it had widened. At the 4-year evaluation, there was no difference in mortality between the groups. At 8 years, however, a significant difference was noted, which was further substantiated at 10 years with a 20% mortality rate in the pancreas-kidney group versus an 80% mortality in the kidney alone group.

CONCLUSIONS

We found a substantial reduction in mortality in IDDM patients 10 years after successful combined pancreas and kidney transplantation. We speculate that the decrease in mortality was due to the beneficial effect of long-term normoglycemia on diabetic late complications and suggest therefore that combined pancreas and kidney transplantation, rather than kidney transplantation alone, should be offered to IDDM patients with end-stage diabetic nephropathy.

Xenoislet transplantation: experimental and clinical aspects

Ten diabetic renal transplant patients had porcine fetal islet-like cell clusters (ICC) injected intraportally or placed under the kidney capsule. In some patients, temporary graft survival was achieved, as evidenced by the urinary excretion of small amounts of porcine C-peptide (4 patients) and the identification of some intact insulin-staining cells in a biopsy specimen (1 patient). Glucose metabolism remained unaffected. To improve the results, better islets and better immunosuppressive protocols are required. We found that, while fetal porcine ICC produced insulin only after several weeks, adult islets gave immediate insulin production. The search for an optimal immunosuppression was conducted in the pig-to-rat islet transplant model. A clear inhibitory effect on the xenograft rejection was observed when using some of the new drugs. The best results were achieved with a triple drug regimen consisting of cyclosporine, mycophenolate mofetil and leflunomide.

No evidence of infection with porcine endogenous retrovirus in recipients of porcine islet-cell xenografts

BACKGROUND

The study of whether porcine xenografts can lead to porcine endogenous retrovirus (PERV) infection of recipients is critical for evaluating the safety of pig-to-man xenotransplantation. PERV is carried in the pig germline, and all recipients of porcine tissues or organs will be exposed to the virus.

METHODS

We studied 10 diabetic patients who had received porcine fetal islets between 1990 and 1993, looking for evidence of PERV infection by using PCR serology, PCR, and reverse transcriptase assays. Prolonged xenograft survival (up to a year) was confirmed in five patients by porcine C-peptide excretion and detection of pig mitochondrial DNA (mtDNA) in serum.

FINDINGS

Despite the evidence for extended exposure to pig cells and despite concomitant immunosuppressive therapy, we were unable to detect markers of PERV infection in any patient. Screening for two PERV sequences in peripheral blood lymphocytes collected 4-7 years after the xenotransplantation was negative. Markers of PERV expression, including viral RNA and reverse transcriptase, were undetectable in sera from both early (day 3 to day 180) and late (4-7 years) time points. Western blot analysis for antibodies was consistently negative.

INTERPRETATION

These results suggested the absence of PERV infection in these patients. Also this study establishes a minimum standard for post-transplant surveillance of patients given porcine xenografts.

Survival of fetal porcine pancreatic islet tissue transplanted to a diabetic patient: findings by ultrastructural immunocytochemistry

Porcine fetal endocrine pancreatic tissue was placed under the kidney capsule in a diabetic renal transplant patient. In a core-needle kidney biopsy specimen obtained 3 weeks after transplantation, clusters of epithelial cells were identified in the subcapsular space. The ultrastructural and immunocytochemical features of these cells were typical of pancreatic islet cells. Some cells stained positively for insulin; others stained positively for glucagon, somatostatin or chromagranin A. There were well-defined cytoplastic storage and transport granulae that indicated hormone synthesis. The ultrastructural findings provide further evidence that porcine cells can survive after transplantation to humans.