AN69 Hollow Fiber Membrane will Reduce but Not Abolish the Risk of Transmission of Porcine Endogenous Retroviruses

As the risk of porcine endogenous retrovirus (PERV) infection is a major obstacle to the xenotransplantation of porcine tissue, we investigated whether an AN69 hollow fibre membrane, used for islets of Langerhans transplantation, could prevent the transfer of PERVs and thus reduce the risk of PERV infection. PK15 cells were used as a PERV source. A specific and highly sensitive RCR was used for detection of a PERV provirus DNA (gag region) and a porcine mtDNA. Human U293 cells were incubated in vitro with encapsulated PK15 cells, concentrated encapsulated PK15 supernatant, or concentrated PK15 supernatant as a control. CD1 mice were implanted in vivo with encapsulated PK15 cells or injected with PK15 supernatant. We found no infection in human cells incubated with either encapsulated PK15 supernatant or in 10 out of 11 samples after coincubation with encapsulated PK15 cells. Infection of human cells was, however, detected in 1 out of 11 samples after coincubation with encapsulated PK15 cells. The presence of PERV provirus DNA and porcine mtDNA was detected in all the investigated tissues of the mice injected with PK15 supernatant and in various tissues of the mice implanted with encapsulated PK15 cells. Four weeks after the last injection of PK15 supernatant or a fiber explantation, no mouse showed any presence of PERV provirus DNA or porcine mtDNA. Our results demonstrate that AN69 hollow fiber membrane will reduce but not abolish the risk of PERV infection. Because the real risk of PERV infection still remains unknown, it is necessary to investigate further the real protection that could be provided by hollow fibers to ensure the safety of clinical xenotransplantation.

Pdx-1 or Pdx-1-VP16 protein transduction induces beta-cell gene expression in liver-stem WB cells

Background

Pancreatic duodenal homeobox-1 (Pdx-1) or Pdx-1-VP16 gene transfer has been shown to induce in vitro rat liver-stem WB cell conversion into pancreatic endocrine precursor cells. High glucose conditions were necessary for further differentiation into functional insulin-producing cells. Pdx-1 has the ability to permeate different cell types due to an inherent protein transduction domain (PTD). In this study, we evaluated liver-to-pancreas conversion of WB cells following Pdx-1 or Pdx-1-VP16 protein transduction.

Findings

WB cells were grown in high glucose medium containing Pdx-1 or Pdx-1-VP16 recombinant proteins for two weeks. β-like cell commitment was analysed by RT-PCR of pancreatic endocrine genes. We found that WB cells in high glucose culture spontaneously express pancreatic endocrine genes (Pdx-1, Ngn3, Nkx2.2, Kir6.2). Their further differentiation into β-like cells expressing genes related to endocrine pancreas development (Ngn3, NeuroD, Pax4, Nkx2.2, Nkx6.1, Pdx-1) and β-cell function (Glut-2, Kir6.2, insulin) was achieved only in the presence of Pdx-1(-VP16) protein.

Conclusion

These results demonstrate that Pdx-1(-VP16) protein transduction is instrumental for in vitro liver-to-pancreas conversion and is an alternative to gene therapy for β-cell engineering for diabetes cell therapy.

Some ethical issues regarding xenotransfusion

BACKGROUND

The use of porcine red blood cells has recently been proposed as a possible solution to the shortage of blood for human transfusion.

OBJECTIVES

The purpose of this paper is to compare some ethical issues regarding xenotransfusion (XTF) with those relating to xenotransplantation (XT) of organs, tissues and cells.

MATERIALS AND METHODS

Various ethical concerns and viewpoints relating to XTF are discussed.

RESULTS

The main ethical obstacles to XT do not apply to XTF. It is much more ethically acceptable to raise pigs for regular blood collection as it doesn't damage the health of the animal. Porcine endogenous retrovirus infection, the major concern associated with XT, does not apply to XTF, since red blood cells have no DNA and have a very short lifespan. Clinical trials will be possible in humans once XTF has been demonstrated to be effective and harmless in non-human primates. Transgenesis is acceptable for pig blood donors because only a limited number of genes are involved, and these animals will never enter into the livestock gene pool or the food chain.

CONCLUSION

Because the need for blood is less pressing than that for organs, tissues or cells, the use of animal blood for human transfusion is not an absolute necessity. However, it represents a real opportunity. The ability to gain access to an unlimited quantity of blood is a reasonable justification for XTF. Because its technical and ethical hurdles are less stringent, XTF could be the first large-scale clinical application of XT.

Xenotransfusions, past and present

The first blood transfusions in humans were xenotransfusions, carried out by Jean-Baptiste Denis beginning in 1667. Richard Lower, Matthäus Purmann and Georges Mercklin also experimented with the use of animal blood for transfusion until this practice was forbidden in 1670, after the death of one of Denis's patients. In the middle of the 19th century, xenotransfusion was rescued from oblivion by the work of Pierre Cyprien Oré. Franz Gesellius and Oscar Hasse fervently defended xenotransfusion, but Emil Ponfick and Leonard Landois stressed the potentially harmful effects of inter-species transfusion from 1874 onward. Xenotransfusion was abandoned completely following the discovery of blood groups by Karl Landsteiner in 1900. From 2000, because of progress in xenotransplantation and the need of blood supply, xenotransfusion is again being considered. Pigs are the best potential donors. The development of alpha-1,3-galactosyltransferase gene-knockout pigs has overcome the first hurdle to xenotransfusion. The main obstacle to porcine red blood cell transfusion is now the cellular response involving macrophages or natural killer cells.

Cytokine mobilization of bone marrow cells and pancreatic lesion do not improve streptozotocin-induced diabetes in mice by transdifferentiation of bone marrow cells into insulin-producing cells

OBJECTIVE

Transdifferentiation of bone marrow cells (BMC) into insulin-producing cells might provide a new cellular therapy for type I diabetes, but its existence is controversial. Our aim was to determine if those cells could transdifferentiate, even at low frequency, into insulin-producing cells, in testing optimized experimental conditions.

METHODS

We grafted mice with total BMC, genetically labeled either ubiquitarily, or with a marker conditionally expressed under the control of the insulin beta-cell specific promoter. We treated some of the recipients with an agent toxic to beta-cells (streptozotocin) and with cytokines stem cell factor (SCF) and granulocyte-colony stimulating factor (G-CSF).

RESULTS

The contribution of grafted cells could be detected neither for natural turnover (n=6), nor for beta-cell regeneration after pancreatic lesion (n=7), 90 days post-transplantation. Cytokine mobilization of BMC in the blood stream, reported to favor their transdifferentiation into cardiac and neural cells, had never been tested before for beta-cell generation. Here, we showed that injection of SCF and G-CSF did not lead to a detectable level of transdifferentiation (n=7).

CONCLUSIONS

We conclude that BMC cannot spontaneously transdifferentiate into insulin-producing cells in vivo, even after beta-cell lesion and mobilization induced by cytokines. Interestingly, however, treatment by cytokines may have beneficial indirect effects on STZ-induced hyperglycaemia.

Lymphocytic insulitis in a juvenile dog with diabetes mellitus

Autoimmune diabetes has never been described in a juvenile dog, whereas serological evidence has established its development in adult dogs. Diabetes mellitus was diagnosed in a 3-mo-old Donge de Bordeaux dog suffering from persistent hyperglycemia and concurrent insulinopenia. Histological analysis of the pancreas revealed inflammatory lesions in 40% of the islets of Langerhans, with infiltration predominantly by T lymphocytes (more than 90%), either at the edge (peri-insulitis: 10%) or in the islets (insulitis: 30%). The remaining 60% of the islets showed a marked atrophy due to massive beta cell loss with no loss of alpha cells. This pattern is quite similar to that observed in humans in which a characteristic insulitis containing high numbers of T lymphocytes is found in 20% of the islets at diabetes diagnosis. By contrast, in rodent models, nearly 70% of the islets of Langerhans show inflammation at diagnosis and macrophages and dendritic cells predominate in the inflammatory lesions. This is the first report of lymphocytic insulitis in a juvenile dog exhibiting diabetes mellitus. Our observations suggest an autoimmune origin for the disease in this dog that is similar to human type 1 diabetes mellitus, for which there is no accurate spontaneous large animal model.

History of xenotransplantation

The present historical review reports the clinical experiences of transplantations from animal to human. The first transplantation attempts were made without any knowledge of the species barrier. The pioneers of xenotransplantation realized xenotransfusions as early as the 16th century, then cell and tissue xenotransplantations in the 19th century. At the beginning of the 20th century, xenotransplantation of testicles became the latest craze. At the same time, and later in the 1960s, organ xenotransplantations were attempted, with disappointing results. Mathieu Jaboulay, Serge Voronoff, Keith Reemtsma, James Hardy, Denton Cooley, Thomas Starzl, Christiaan Barnard and Leonard Bailey were among the pionneers of xenotransplantation. Recent trials concerned above all tissue and cell xenotransplantations. Nowadays, with encapsulation, transgenesis, and cloning, great advances have been made for controlling xenograft rejection, but ethical questions linked to the risk of infections have become a major pre-occupation within the scientific community and the general population.

Reluctance of French patients with type 1 diabetes to undergo pig pancreatic islet xenotransplantation

INTRODUCTION

Type 1 diabetes could possibly be treated by transplantation of pig pancreatic islets. In addition to medical difficulties and ethical problems, social hurdles may need to be overcome. We have evaluated the attitude of patients with type 1 diabetes to the xenotransplantation of pig pancreatic islets and to the potential risks associated with such treatment.

METHODS

A survey of 214 patients with type 1 diabetes was carried out in France based on a multiple-choice questionnaire.

RESULTS

At first, 52.0% of these patients indicated that they would agree to receive pig islet xenografts. The main sources of reluctance were the ''risk of disease transmission'' (55.5%) and ''risks not yet identified'' (48.7%). After they were told of the risk of cancer or infection associated with immunosuppression, 74.9% of the respondents chose to refuse the transplant, compared with 48.0% before they heard of such risks. A 68.1% would refuse the xenotransplant if it would not exempt them completely from being treated by insulin injections. Discontinuing insulin injections was the most important priority for diabetic patients (73.5%), rather than limitation of diabetes-related complications (52.5%) or increase in life expectancy (44.0%). After they were informed of all of the risks associated with the procedure, 70.5% of the respondents decided they would rather not take any risks, and said they would refuse pig islet transplantation.

CONCLUSION

When diabetic patients learned about potential infectious risks and other risks associated with immunosuppression, reluctance to undergo xenotransplantation gained in significance or even led to refusal of the procedure.

In vitro induction of inhibitory macrophage differentiation by granulocyte-macrophage colony-stimulating factor, stem cell factor and interferon-gamma from lineage phenotypes-negative c-kit-positive murine hematopoietic progenitor cells

CD11b+Gr-1+ inhibitory macrophages (iMacs) were implicated in profound depression of T cell functions sometimes observed during cyclophosphamide treatments and overwhelming infections, through a secretion of nitric oxide (NO). Myeloid origin and maturation stages of iMacs are still unknown. As tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) contributed crucially to the activation of inducible NO synthase (iNOS) gene transcription and to the differentiation of macrophages, we tested their roles in the induction of iMacs differentiation from bone marrow hematopoietic progenitor cells (HPC) of uncompromised mice. Lineage phenotypes-negative (lin)) c-kit+ cells of Balb/c mice were cultured 6 days with granulocyte-macrophage colony-stimulating factor (GM-CSF), stem cell factor (SCF, c-kit ligand) in presence or not of TNF-alpha or IFN-gamma. CD11b+Gr-1+ cells only derived in presence of [GM-CSF + SCF + TNF-alpha] or [GM-CSF + SCF + IFN-gamma] could express iNOS upon in vitro stimulation with [IFN-gamma + TNF-alpha] or [IFN-gamma + LPS] known to boost iNOS expression in murine macrophages. However, whereas [GM-CSF + SCF + TNF-alpha] induced only weakly iMacs generation and contributed also to the differentiation of CD11b+Gr-1-CD11c+ myeloid dendritic cells, [GM-CSF + SCF + IFN-gamma] induced exclusively and importantly iMacs differentiation. Moreover [GM-CSF + SCF + IFN-gamma]-generated iMacs were more mature than [GM-CSF + SCF + TNF-alpha]-derived iMacs since IFN-gamma increased more strongly CD11b+Gr-1+ cells expressing Ly-6C and generated lesser cells expressing MHC class II and CD86 molecules. Finally [GM-CSF + SCF + IFN-gamma]-generated CD11b+ cells showing a powerful suppressive activity on T cell proliferations, correlated with NO secretion. In conclusion, our study showed, for the first time, that IFN-gamma induced very efficiently the differentiation of functional iMacs from lin- c-kit+ murine HPC in vitro, and indicated clearly that iMacs progenitors may be present in bone marrow of naïve mice.

Microchimerism and transmission of porcine endogenous retrovirus from a pig cell line or specific pathogen-free pig islets to mouse tissues and human cells during xenografts in nude mice

AIMS/HYPOTHESIS

Pig islets could transmit porcine endogenous retroviruses (PERV) to diabetic patients. Our previous work showed that pig islets expressed low levels of PERV mRNA and were not likely to transmit PERV to human cells in vitro. The real risk of infection during pig tissue xenografts can only be evaluated by in vivo experiments.

METHODS

Nude mice bearing tumours containing human 293 cells were grafted with specific pathogen-free pig islets or PERV-producing pig PK15 cells to determine whether pig cells could transmit PERV to mouse and human cells in vivo. Infection was monitored by PCR, long PCR, RT-PCR and long RT-PCR. As detection of PERV sequences could be due to the presence of residual pig cells, we looked for pig mitochondrial (mt) DNA. Quantitative PCR for PERV and pig mt DNA was done to compare the PERV-to-pig mt (P-to-M) ratio of each sample with the reference ratio for grafted pig cells.

RESULTS

Among 78 mouse tissues from PK15-grafted mice, 54 and 72 were positive for gag and pig mt DNA, respectively. Human tumours developed in these mice were positive for PERV (78%) and pig mt (89%). The P-to-M ratios for mouse tissues and PERV-positive human tumours from PK15-grafted mice were higher than the ratio in PK15 cells. Among 41 tissues from pig islet cell-grafted mice, 7 were positive for PERV (3 lymph nodes, 1 kidney, 2 salivary glands, 1 ovary), and 14 were positive for pig mt DNA. Three of these samples (1 lymph node, 1 kidney and 1 salivary gland) were positive for gag DNA, but negative for pig mt DNA. One human tumour in these mice was positive for PERV DNA. P-to-M reference ratio in grafted islet cells was 0.05+/-0.03. The three PERV-positive lymph nodes contained 78 gag/3 mt copies (P-to-M: 26), 101 gag/3 mt copies (P-to-M: 34), and 4 gag/0 mt copies. The two PERV-positive salivary glands contained 14 gag/1 mt copies, and 28 gag/0 mt copies. The ovary and the kidney contained 46 gag/3 mt and 69 gag/0 mt copies, respectively. The PERV-positive human tumour contained 47 gag/3 mt copies.

CONCLUSIONS/INTERPRETATION

Microchimerism and PERV transmission were frequently observed in both mouse and human tissues during grafting of pig PK15 cells into nude mice bearing human tumours, and sometimes during pig islet xenograft in this model. This strengthens the notion that there is a risk of transmitting PERV during pig islet xenograft.

Feeding NOD mice with pig splenocytes induces transferable mechanisms that modulate cellular and humoral xenogeneic reactions against pig spleen or islet cells

We have reported previously that oral administration of pig cells to NOD mice modified xenogeneic cellular response against pig islet cells (PICs), and hypothesized that it may have induced active suppression. This preliminary report evaluated only the effect of feeding pig cells by 'primary' proliferation, i.e. when splenocytes from fed mice are confronted with pig cells in vitro. The present study also considered 'secondary' proliferation and cytokine production after feeding and subsequent in vivo graft of pig cells. Additionally, serum IgM and IgG isotypes were quantified by ELISA using pig target cells. Induction of active mechanism by feeding was hypothetical, which led us here to transfer splenocytes from mice fed pig spleen cells (PSC) and evaluate 'primary' (after transfer) and 'secondary' (after transfer and subsequent graft of pig cells) proliferations and cytokine secretions in recipient mice. We also determined whether the effects of feeding pig cells persisted after depression of suppressor mechanisms by cyclophosphamide. Mice fed with PSC displayed increased 'primary' splenocyte proliferation to PSC or PIC (P < 0.0001), while 'secondary' responses were decreased (P < 0.03) in those fed PSC and subsequently grafted with PSC. The increased 'primary' and decreased 'secondary' proliferations were reduced (P < 0.04) by pretreatment with cyclophosphamide. The IL-10/ and IL-4/IFNgamma ratios produced in response to PSC increased (P < 0.04) in mice fed and grafted with PSC compared to those grafted only with PSC. IgM and IgG levels against pig cells were, respectively, increased (P < 0.04) and decreased (P < 0.04) in mice fed and grafted with PSC. IgG2a and IgG2b, but not IgG1, levels were lower (P < 0.01). These effects of feeding PSC on 'secondary' proliferation, cytokine and antibody productions, were not detected when mice were fed PSC only after graft with PSC. Transfer with splenocytes from mice fed PSC increased 'primary' proliferation of splenocytes from recipient mice in response to PSC (P < 0.02) or PIC (P < 0.05). After transfer with splenocytes from PSC-fed mice and graft with PSC, 'secondary' proliferation to pig cells were reduced (P < 0.04), and the IL-10/IFNgamma ratio produced in response to PSC was increased fourfold. Thus, oral administration of PSC induces active transferable mechanisms, characterized by a biphasic pattern with early increased 'primary' xenogeneic cellular reactions to both PSC and PIC, followed by decreased 'secondary' responsiveness and a concomitant shift of the Th1/Th2 balance towards greater Th2 influence. Decreased responsiveness may be due to active suppression, even though induction of anergy or deletion cannot be excluded.

In vitro recognition and impairment of pig islet cells by baboon immune cells: similarity to human cellular reactions

BACKGROUND

Grafting pig islets into patients with type 1 diabetes requires control of the strong cellular xenogeneic rejection. This in vitro study compared the cellular reaction of baboons and humans to pig islet cells (PICs) to confirm the validity of using these animals for further in vivo preclinical trials.

METHODS

Baboon or human peripheral blood mononuclear cells (PBMCs) or subsets were co-incubated with PICs from specific pathogen-free adult pigs for 7 days to determine the mechanisms and intensity of PBMC proliferation. Interleukin (IL) 10 and interferon (IFN) gamma secretion were assessed by enzyme-linked immunosorbent assay. Because proliferation was not indicative of aggression, a test based on perifusion analysis of the alteration of basal and stimulated insulin releases from PIC incubated with different baboon and human cells was developed.

RESULTS

Baboon PBMCs strongly proliferated in response to PICs (stimulation index [SI]=24.8+/-6.9 [n=8] vs. 23.9+/-3.4 [n=34] for human PBMCs), showing considerable variation in intensity among animals (2.3<SI<63) and humans (1.8<SI<97). PBMC proliferation was inhibited in baboons and humans by anti-CD4 (% inhibition of SI: 71+/-10% and 75+/-7%, respectively) and anti-DR (75+/-35% and 80+/-6%) monoclonal antibodies (MoAbs) or by depletion of MHC class II+ cells (99+/-1% and 90+/-6%). Blocking by anti-CD8 or anti-CD16 MoAbs was weaker and variable among both animals and humans. IL-10 production by baboon and human PBMCs in response to PICs increased more than IFN-gamma production after 2 days of coculture, but the IL-10/IFN-gamma ratio was inverted after 5 days of coculture. After 7 days (and even after only 2 days) of coculture with baboon (n=8) or human (n=18) PBMCs, basal and glucose-stimulated insulin secretions from PICs were almost completely abolished (P<0.0001). The drop in insulin release could have mainly resulted from lysis of PICs, because the number of PICs decreased by 78% after 7 days of co-incubation with PBMCs. A decrease of insulin release by PBMCs was reproduced with plastic-adherent cells and was abolished by depletion of MHC class II+ cells or by addition of 100 microg/ml gadolinium (which inhibits macrophages), but not by cyclosporine. In baboons, as in humans, insulin release was also decreased after coculture of PICs with enriched T lymphocytes remixed with antigen-presenting cells (APCs).

CONCLUSIONS

This study provides the first data on in vitro comparison of baboon and human cell-mediated recognition and impairment of PICs. Proliferation of PBMCs against PICs involves mainly CD4 T cells, with indirect recognition mediated by baboon or human MHC class II+ APCs. The Th2/Th1 profile of cytokines secreted in response to PICs was similar in baboon and human PBMCs. The model based on alteration of insulin secretion indicates that PIC impairment by whole mononuclear cells was strong and rapid and that a crucial role was played by MHC class II+ and plastic-adherent cells. Two mechanisms appear to be responsible for the role of these cells: (1) early and strong direct effect, which is potentially involved in vivo in primary nonfunction of islets aggressed by monocytes and macrophages; and (2) presentation of PIC xenoantigens, which leads to impairment by T lymphocytes possibly involved in in vivo-specific cellular rejection. The mechanisms and intensity of baboon cellular reactions to PICs in vitro were similar to those observed in humans, which suggests that the baboon is a suitable model for the study of cellular mechanisms during preclinical trials of pig islet xenografts.

Long-term follow-up failed to detect in vitro transmission of full-length porcine endogenous retroviruses from specific pathogen-free pig islets to human cells

AIMS/HYPOTHESIS

Islets from specific pathogen-free (SPF) pigs could prevent the transmission of conventional zoonosis, but not endogenous retroviruses (PERV), from pigs to diabetic patients. We previously reported that the pancreas showed the lowest expression of PERV mRNA among pig tissues intended for grafting. This study aimed to determine whether PERV from pig islets infect human cells during co-incubation.

METHODS

Human cells (including highly PERV-sensitive 293 cells) were incubated with SPF pig islet cells under conditions designed to increase contact (a high islet to human cell ratio, extended period of co-culture, and repeated contacts). PK15 and G2 retrovirus-producing pig cells were used in place of islet cells as "positive infection controls". Infection of human cells was monitored on cellular extracts and supernatants by PCR or long PCR, and RT-PCR or long RT-PCR, to detect PERV DNA and mRNA, respectively. Reverse-transcriptase activity was monitored by PERT.

RESULTS

Despite the presence of all PERV sequences in pig islet cells, including full-length inserts, no DNA or RNA for gag, pol, and the 3 env sub-types were detected in any human cell line or blood mononuclear cells incubated with pig islet cells, during an 18-week follow-up period. No PERV sequences or RT activity were detected in supernatants. PERV signals were negative even when the pig islet to human cell ratio was increased to 100:1, the time of co-culture was extended to 5 days and two sequential co-incubations were done. By contrast, all PERV DNA and mRNA were detected in all human cells co-incubated with PK15 or G2 cells. Depending on human cell types, productive or non-productive infections were obtained: full-length PERV RNA and RT activity in supernatants were detected or not; and PERV sequences to previously unexposed human cells by PERV-infected human cells were transmitted or not. Some human cells were not productively infected by PK15 cells but became productively infected after co-incubation with PERV-infected 293 cells.

CONCLUSION/INTERPRETATION

SPF pig islet cells, even with PERV inserts and transcripts, have very little probability of transmitting PERV to human cells during co-incubation. The sensitivity of human cells to stable and productive infection by PERV depends on the cell type. Human adaptation of PERV was observed.

Co-incubation of pig islet cells with spleen cells from non-obese diabetic mice causes decreased insulin release by non-T-cell- and T-cell-mediated mechanisms

In vitro studies were conducted in the non-obese diabetic (NOD) mouse, prone to Type 1 autoimmune diabetes, to investigate the mechanisms involved in cell-mediated rejection of pig islet xenografts. Our previous work concerning the mechanisms of proliferation of xenogeneic lymphocytes to pig islet cells (PIC) was not indicative of PIC impairment. Consequently, a test was developed based on perifusion analysis of the alteration of basal and stimulated insulin release from adult PIC incubated with mouse splenocytes or subsets. Compared with PIC incubation alone or with syngeneic pig splenocytes, co-incubation with mouse whole spleen cells resulted in a decrease of basal and stimulated insulin release (P < 0.001). Two components of this alteration were detected separately: PIC impairment was decreased (P < 0.01) after removal of plastic-adherent cells from spleen cells, but maintained (P < 0.01) when plastic-adherent cells alone were co-incubated with PIC. The increase of murine interleukin-1 beta when mouse plastic-adherent spleen cells were cultured with PIC (P < 0.04) was indicative of macrophage activation. Soluble factors produced during co-incubation of mouse splenocytes or plastic-adherent cells with PIC were involved in the impairment process, since supernatant fluids collected during previous PIC-mouse cell co-incubations directly altered (P < 0.01) insulin release from PIC. Moreover, impairment of PIC by mouse spleen cells was abolished (P < 0.01) by gadolinium chloride (which inhibits macrophages), but not by cyclosporin A. Another mechanism was apparent, since co-incubation of PIC with purified mouse T cells or CD4+ T cells, re-mixed with antigen-presenting cells, led to a decrease (P < 0.01) of insulin release. This model, based on the alteration of dynamic basal and stimulated insulin release, is indicative of in vitro cell-mediated alteration of PIC in the NOD mouse. The effect of whole spleen cells was rapid, and a crucial role was played by plastic-adherent cells. Two mechanisms were responsible for the behaviour of these cells: an early direct effect (at least in part via soluble products); and the indirect presentation of PIC xenoantigens (leading to impairment by CD4+ T lymphocytes).

In vitro co-incubation of pig islet cells with xenogeneic human blood mononuclear cells causes loss of insulin release during perifusion: involvement of non-T-cell- and T-cell-mediated mechanisms

Because the different steps of the human cellular immune rejection of pig islets are still poorly understood, our previous work concerned the intensity and mechanisms of the proliferation of human peripheral blood mononuclear cells (PBMC) to adult pig islet cells (PIC). As lymphocyte proliferation is not indicative of alteration of PIC, the present in vitro study evaluated cell-mediated immune effectors possibly involved in impairment of adult PIC. A test was thus developed, based on perifusion analysis of the alteration of insulin release from PIC incubated with different human cells. Compared to PIC incubation alone or with autologous pig splenocytes, seven-day co-incubation with whole human peripheral blood mononuclear cells (PBMC) (n = 18) led to almost complete abolition of basal and stimulated insulin releases (p < 0.0001). This effect could not be reversed by extensive sequential washes before perifusion of PIC, and the number of PIC was decreased by 78% after seven-day co-incubation with PBMC. PBMC are a complex mixture of cells involved in different xenogeneic mechanisms, and two components of this PIC impairment were then detected separately. First, the effect of PBMC against PIC was decreased (p < 0.0001) after removal of either MHC class II+ or CD14+ cells from PBMC. On the contrary, decreasing effect (p < 0.001) on insulin secretion was observed when only plastic-adherent or CD14+ cells were co-incubated with PIC. Additionally, alteration of insulin release from PIC cultured with PBMC or plastic-adherent cells was abolished dose-dependently (p < 0.0001 and p < 0.04, respectively) by gadolinium chloride (which inhibits macrophages), but not modified by cyclosporin A or mycophenolate mofetil which did not alter insulin release from PIC but blocked the proliferation of PBMC against PIC. A second mechanism was also detected, since co-incubation of PIC with purified human T cells remixed with antigen-presenting cells led to a decrease (p < 0.0001) of insulin release. This model based on the alteration of dynamic basal and stimulated insulin secretion provides detailed account of in vitro human cell-mediated impairment of PIC. It shows that the xenogeneic effect of whole mononuclear cells was strong and rapid. A crucial role was played by MHC class II+, CD14+, and plastic-adherent cells. Two mechanisms appear to be responsible for the role of these cells: 1) early direct effect, potentially involved in vivo in primary nonfunction of islets aggressed by monocytes/macrophages; and 2) the presentation of PIC xenoantigens leading to impairment by T lymphocytes, which may be involved in in vivo specific cellular rejection.

Oral insulin administration and residual beta-cell function in recent-onset type 1 diabetes: a multicentre randomised controlled trial. Diabète Insuline Orale group

BACKGROUND

Oral administration of autoantigens can slow the progression of beta-cell destruction in non-obese diabetic mice. We investigated whether oral administration of recombinant human insulin could protect residual beta-cell function in recent-onset type 1 diabetes.

METHODS

We enrolled 131 autoantibody-positive diabetic patients aged 7-40 years within 2 weeks of diagnosis (no ketoacidosis at diagnosis, weight loss <10%, polyuria for <6 weeks). They were randomly assigned 2.5 mg or 7.5 mg oral insulin daily or placebo for 1 year, in addition to subcutaneous insulin therapy. Serum C-peptide concentrations were measured in the fasting state and after stimulation, to assess beta-cell function. Autoantibodies to beta-cell antigens were assayed. Analyses were by intention to treat.

FINDINGS

Baseline C-peptide and haemoglobin A1c concentrations were similar in the three groups. During follow-up, there were no differences between the groups assigned 2.5 mg or 7.5 mg oral insulin or placebo in subcutaneous insulin requirements, haemoglobin A1c concentrations, or measurements of fasting (mean at 12 months 0.18 [SD 0.17], 0.17 [0.17], and 0.17 [0.12] nmol/L) or stimulated C-peptide concentrations (glucagon-stimulated 0.39 [0.38], 0.37 [0.39], and 0.33 [0.24] nmol/L; meal-stimulated 0.72 [0.60], 0.49 [0.49], and 0.57 [0.51 nmol/L]. Neither age nor C-peptide concentration at entry influenced treatment effects. No differences were seen in the time-course or titres of antibodies to insulin, glutamic acid decarboxylase, or islet antigen 2.

INTERPRETATION

At the doses used in this trial, oral administration of insulin initiated at clinical onset of type 1 diabetes did not prevent the deterioration of beta-cell function.

[Acceptability of xenograft in type 1 diabetic patients and by the general French population]

OBJECTIVE

The possibility of using pig xenografts raises the questions of their acceptability and the reasons for reluctance by patients and society, which have not been clearly investigated in Europe.

RESEARCH DESIGN AND METHODS

A survey using a multiple-choice questionnaire was conducted to quantify the acceptability of pig xenografts in type 1 diabetic patients potentially concerned by xenografts (n = 377) as compared to a sample of the French population (n = 697).

RESULTS

Willingness to accept a xenograft was significantly greater among diabetic patients than the general population (64% vs 54%, P < 0.001). The notion of using pig xenografts appears to be rather well accepted by the general population, and more information might improve acceptability. The acceptance of xenografts in general and pig tissues in particular was higher in diabetic patients.

CONCLUSIONS

Because the general population and type 1 diabetic patients are not aware of the sanitary risks specifically related to a xenograft, the decision to use xenografts cannot be based simply on the expectations of possible recipients. The sanitary risks need to be assessed before further xenografts are performed, particularly in diabetic patients whose risk/benefit ratio is not particularly favourable.

Porcine endogenous retroviral mRNAs in pancreas and a panel of tissues from specific pathogen-free pigs

Pigs are potential providers of donor tissues for xenotransplantation (e.g. of pancreatic islets) in Type 1 diabetes. In this context, our group has studied the use of islets from specific pathogen-free (SPF) pigs as a means of reducing the risks of "conventional zoonosis". Although this approach does not prevent the transmission of pig endogenous retrovirus (PERV) to humans, we attempted to determine the presence of C-type PERV mRNAs for gag, pol, and env subtypes as a first descriptive step in the retroviral characterisation of SPF pig tissues (especially pancreas). Using semiquantitative reverse-transcriptase polymer chain reaction with 18S rRNA and beta-actin as internal controls, PERV mRNA levels were compared in a large panel of tissues from SPF and conventional pigs. PERV mRNAs for gag, pol, env-A and env-B were present in all tissues studied from the nine SPF pigs tested. Signals for env-C mRNAs were of much lower intensity than those for env-A and B, and most often undetectable in pancreas. The mRNA levels for gag, pol, env-A, env-B and env-C mRNAs were lower in pancreas (p < 0.01) than in all other tissues. Among other porcine tissues likely to be grafted in man, the highest retroviral mRNA levels were detected in kidney (p < 0.01), followed by liver, lung and heart. Amplified PERV mRNA signals were about 17 times less frequent in pig pancreas than in the retroviral-producing porcine cell line G2, while kidney contained about 6 times more PERV mRNAs than pancreas. The levels of gag, pol, env-A, env-B, and env-C mRNAs also varied between tissues of conventional pigs: PERV mRNA levels were lowest in pancreas, and env-C mRNAs were most often undetectable. For all SPF tissues tested, pol, gag, env-A, env-B, and env-C mRNA levels were in the same range or slightly higher than in corresponding tissues of conventional pigs. In summary, this study of C-type PERV mRNAs in a large panel of tissues from SPF pigs, in the context of our strategy of quality assurance and sanitary control, indicated that PERV mRNA levels were in the same range in SPF and corresponding conventional pig tissues, confirming that the use of SPF pigs would not prevent the risk of PERV transmission to human recipients of xenografts. PERV-A and PERV-B may be mainly represented, and PERV-C much less, in these pig tissues (particularly pancreas). The fact that pancreas expressed the lowest PERV mRNA levels and kidney the highest, among porcine tissues likely to be grafted, could be of interest from a clinical point of view. Pig tissues may differ in their loads of PERV sequences, which could be a factor in the risk of PERV transmission during xenotransplantation.

Intensity and mechanisms of in vitro xenorecognition of adult pig pancreatic islet cells by CD4+ and CD8+ lymphocytes from type I diabetic or healthy subjects

The intensity and mechanisms of cell-mediated rejection of pig islet cells were studied in 49 Type I diabetic and 34 healthy subjects. Human peripheral mononuclear cells proliferated strongly in response to pig islet cells (p<0.001), though with notable interindividual variations (stimulation index 2 to 215). The variance of stimulation index was higher in diabetic than healthy subjects (p<0.0001). The response to islet cells was stronger (p<0.01) than that to pig splenocytes. Proliferation in response to islet cells was strongly decreased (p<0.01) when CD4+ T cells were blocked with monoclonal antibodies, whereas the blocking of CD8+ cells or NK cells gave less pronounced effects. The response to islet cells was decreased (p<0.01), but not abolished, after antigen-presenting cells were removed. Purified CD4+ cells alone did not proliferate in response to islet cells but recovered their proliferative ability when mixed with antigen-presenting cells, whereas CD8+ cells alone proliferated in the presence of interleukin-2 in response to islet cells. Proliferation was blocked (p<0.01) by anti-DR monoclonal antibodies. During proliferation in response to islet cells, interleukin-10 increased 43-fold (p<0.01) but interferon-gamma increased only slightly. No statistical differences were detected between diabetic and control subjects with respect to lymphocyte subsets and the recognition mechanisms or to interferon-gamma/interleukin-10 production in response to islet cells. These results provide the first detailed information on human cell-mediated xenoreaction to pig islet cells. This situation involves a dominant CD4 class II-restricted Th2 response, with an indirect recognition pathway, as well as a CD8 T-cell response resulting from direct recognition. This strong reaction constitutes a serious obstacle which may vary in degree among subjects.

Long-term culture of free or encapsulated islets isolated from specific pathogen-free (SPF) pigs

As the risk of recipient contamination is a limiting factor for xenotransplantation, the use of specific pathogen-free (SPF) pigs is mandatory. This study investigated the long-term culture of SPF pig islets and evaluated their insulin production when encapsulated in AN69 hollow fibres. Insulin secretion was studied after 3 weeks (n = 10), 2 months (n = 8) and 3 months (n = 3) by 45-min incubation in the presence of 2.8, 5.5, 11 and 16.5mM glucose. Although a decrease in the amount of secreted insulin occurred (1385 +/- 421 and 4323 +/- 1068 microns U/ml at 3 weeks for 2.8 and 16.5 mM glucose respectively; 702 +/- 261 and 2397 +/- 1047 microU/ml at 2 months; 59 +/- 23 and 154 +/- 34 microU/ml at 3 months), glucose-dependent insulin secretion was observed in all cases, i.e. stimulation indices of 8.1 +/- 3.1 (p < 0.05 vs the presence of 5.5 mM glucose) at 3 weeks, 3.3 +/- 1.1 at 2 months and 3.0 +/- 0.7 at 3 months. The insulin secretion of encapsulated SPF pig islets, cultured for 1 or 3 weeks, was evaluated under perifusion conditions using a stimulus of 10mM glucose plus 5.5 mM theophylline. Glucose stimulation resulted in a significant two-fold increase in insulin secretion (p < 0.05), which was maintained over culture time. These results indicate that SPF-isolated islets remained functional when cultured for several weeks either as free or encapsulated islets, although the magnitude of insulin secretion decreased dramatically after three months of culture.

Detection of porcine endogenous retrovirus: possible involvement in pig islet xenotransplantation

One requirement prior to xenotransplantation of porcine islets during Type 1 diabetes is to eliminate the risk of transmitting infectious agents, particularly retroviruses, even when specific pathogen-free (SPF) pigs are used. We developed two sensitive complementary PCR-derived detection tests to assess this risk. This first is intended to detect a novel endogenous retrovirus pol sequence related to a recently described human endogenous retrovirus (HERV-L) and to foamy retroviruses. Primers for species-specific detection of this porcine endogenous sequence were designed and tested. The second test is a product-enhanced reverse transcriptase (PERT) assay optimised for the detection of porcine reverse transcriptase activity. These tests, which were used to detect HERV-L-related sequences and reverse transcriptase activity in certain SPF pig cells and porcine cell lines, may be useful in studying the risk of transmitting retroviruses by pig islet xenotransplantation in the immunogenetic context of Type 1 diabetes.

In vitro xenorecognition of adult pig pancreatic islet cells by splenocytes from nonobese diabetic or non-diabetes-prone mice

BACKGROUND

In vitro studies of the nonobese diabetic (NOD) mouse prone to type 1 autoimmune diabetes were conducted in order to investigate the mechanisms possibly involved in cell-mediated rejection of adult pig islet xenografts. Mouse cellular proliferation in discordant situations was previously investigated only with stimulator lymphocytes and found to be low in intensity and due to an indirect recognition mechanism involving murine antigen-presenting cells (APC). It was also important to characterize murine anti-pig islet response.

METHODS AND RESULTS

In the present study, mouse splenocytes responded to pig islet cells since primary proliferations were detected in non-diabetes-prone Balb/c (P<0.04) or NOD (P<0.001) mice. Moreover, NOD mice displayed a higher (P<0.003) splenocyte response to pig islet cells (stimulation index: 5.8+/-0.7) than did Balb/c mice (stimulation index: 2.3+/-0.3), whereas responses to pig stimulator splenocytes were similar in both strains. The proliferation of NOD splenocytes to pig islet cells was lower (P<0.0001) than the allogeneic response to Balb/c islet cells but similar to syngeneic proliferation to NOD islet cells. In both NOD and Balb/c mice, splenocyte proliferation to pig islet cells was abolished (P<0.01) when CD4+ cells were blocked with antibodies, whereas the blocking of CD8+ cells had a nonsignificant effect. The main T-splenocyte subsets involved were restricted to mouse MHC class II molecules as they did not proliferate in the presence of monoclonal antibodies directed at I-A molecules. NOD and Balb/c splenocyte proliferation to pig islet cells was abolished after removal of plastic-adherent APC, which indicates that the major activation pathway was indirect. Purified CD4+ or CD8- cells alone did not proliferate in response to pig islet cells but recovered a proliferative ability when mixed with APC. CD4- cells, alone or in the presence of APC, were not capable of responding to pig islet cells. Both Th1 and Th2 splenocytes were involved in response to pig islet cells since interferon-gamma (IFN-gamma) and interleukin (IL-)-4 production increased significantly (300-fold and 11-fold, respectively, P<0.02 for both), whereas the increase in IL-10 production was much lower (only 1.5-fold). The IFN-gamma/IL-4 and IFN-gamma/IL-10 ratios stimulated by pig islet cells were not different with NOD and Balb/c splenocytes.

CONCLUSION

In conclusion, mouse cell-mediated reaction against xenogeneic adult pig islet cells mainly involves class II-restricted CD4+ T lymphocytes of Th1 and Th2 subtypes, with an indirect pathway for the recognition. Although of low intensity, this cell-mediated reaction constitutes an obstacle to pig islet engraftment in the mouse, although one not necessarily more insurmountable than alloreactivity. The peculiarity of NOD mouse splenocytes, in terms of proliferation against pig islets, suggests that the study of islet xenograft rejection should take the immunogenetic context of diabetes into account, in which case the use of non-diabetes-prone mice has its limitations.

Spleen cells of non-obese diabetic mice fed with pig splenocytes display modified proliferation and reduced aggressiveness in vitro against pig islet cells

A new means of modifying xenogeneic reaction to pig islet cells, which involves pre-feeding with pig spleen cells, was investigated for the first time in the non-obese diabetic (NOD) mouse. Compared with controls, mice fed with pig spleen cells displayed much higher splenocyte proliferation in response to pig spleen and islet cells (p < 0.0001). This enhanced proliferation was specific for the species providing the fed cells. Positive relationships (p < 0.01) were found between increased splenocyte proliferation in response to pig spleen or islet cells and the number of cells per feeding or the number of daily feedings. Concomitantly, while co-incubation with splenocytes from control mice led to inhibition of both basal and stimulated insulin releases from pig islet cells (p < 0.001), this aggressiveness was abolished (p < 0.001) after co-culture with splenocytes from mice fed with pig spleen cells. The proliferative responses of splenocytes from fed or control mice to pig islet or spleen cells were abolished after removal of plastic-adherent cells, indicating that the major indirect pathway of T-cell activation was unchanged by pig spleen cell feeding. The main T-splenocyte subsets involved were restricted to MHC class II as they did not proliferate in the presence of monoclonal antibodies (mAbs) directed at I-A molecules. In mice fed with pig spleen cells, as well as in control mice, the blocking of CD4 + T cells with mAbs led to abolition of proliferation (p < 0.002), while the blocking of CD8 + led to a less marked effect. However, an increase in the blocking effect of anti-CD8 mAbs was noted in mice fed with pig spleen cells (p < 0.02). In control mice, the main splenocyte subset involved during proliferation in response to pig islet cells was Thl, since interferon gamma (IFNgamma) production increased significantly (p < 0.01) while that of interleukin-10 (IL-10) increased only slightly. The main change observed in mice fed with pig spleen cells was a marked increase in basal IL-10 production (p < 0.01) and the basal IL-10/IFNgamma ratio (p < 0.001). It seems likely that feeding with pig spleen cells shifted the Th1/Th2 balance towards a dominance of Th2-type class II-restricted CD4 + T cells, which may have been conducive to activating CD8 + suppressor T cells. In any event, oral administration of pig cells modified xenogeneic cellular response, which may have implications for xenografts of pig islets. In a more general sense, physiological feeding of cells from xenogeneic species would appear to have certain effects on the immune system.

Perifusion analysis of insulin secretion from specific pathogen-free large-white pig islets shows satisfactory functional characteristics for xenografts in humans

Though the pig appears to be the islet donor of choice for grafts in diabetic patients, there may be a risk of transmission of infectious agents. In this context, we adopted a strategy of islet isolation from pigs raised and killed in specific pathogen-free (SPF) conditions as a minimum with regard to the concept of quality assurance. Accordingly, the present study investigated the function of SPF pig islets to determine whether they react qualitatively and quantitatively to nutriments, hormones and neuromediators with which they would be confronted in man and could therefore provide effective regulation during physiologic or physiopathologic situations. beta cells from 18 Large-White SPF pigs were functionally intact after 7 days in culture. Insulin stimulation indexes (SI) of 3.1 +/- 0.2, 2.2 +/- 0.1, and 4.4 +/- 0.3 were found respectively for 30 mmol/l K+, 100 mumol/l tolbutamide and 10 mmol/l theophylline. Basal insulin secretion (72.2 +/- 7.6 muU/min) had already increased significantly (p < 0.001) with 5.5 mmol/l glucose (184.2 +/- 25.5 muU/min, SI: 2.5 +/- 0.6), indicating that the threshold stimulatory concentration was comparable to that of human islets. Insulin secretion increased in a glucose dose-dependent manner (p < 0.001): SI: 3.1 +/- 0.3 and 3.6 +/- 0.2 with 11.0 mmol/l and 22.0 mmol/l glucose, which showed a satisfactory magnitude with reference to human islets. Even the subtle phenomenon of "glucose memory" was apparent in these pig islets. Arginine stimulated (p < 0.001) insulin secretion dose-dependently (SI: 2.2 +/- 0.3 with 5 mmol/l and 2.9 +/- 0.2 with 10 mmol/l). The ketone body beta-hydroxybutyrate (10 mmol/l) also induced insulin secretion (SI: 4.3 +/- 0.3). Insulin release was stimulated by 4 mumol/l gastric inhibitory peptide, revealing sensitivity to the hormonal enteroinsular axis, and by 2 mumol/l glucagon. Parasympathetic cholinergic influence was studied using 500 mumol/l carbamylcholine, which increased insulin secretion. The influence of orthosympathetic control and of stress situations was also studied. As in human islet response, epinephrine and the alpha 2-agonist clonidine (50 mumol/l) inhibited insulin secretion. Finally pre-culture of islets may be beneficial for graft outcome, provided that no deterioration in islet function occurs. A prolonged 21-day culture of SPF pig islets showed no decrease in insulin response to glucose, arginine and potassium, even with an unaltered threshold stimulatory glucose concentration. Thus, Large-White SPF pigs and the application of our isolation procedure provided islets with functional characteristics reproducibly compatible with potential utilisation for effective regulation of glycaemia under physiologic and physiopathologic situations in humans.

Multiple antibody status in type 1 diabetic patients and subjects at various risk with islet-cell antibodies

The frequency of 37/40 kD antibodies and their association with other pancreatic humoral markers were studied in 109 recently diagnosed Type 1 diabetic patients and 116 subjects with islet-cell antibodies (ICA) at various risk for this disease (64 relatives of Type 1 diabetic patients, 23 schoolchildren with no family history of diabetes, and 29 patients with Graves' disease). At the time of diagnosis, 37/40 kD antibodies were detected in 45% of Type 1a and 77% of Type 1b diabetic patients (p = 0.03). Antibodies to glutamic acid decarboxylase (GAD) and/or 37/40 kD were present with the same frequency as ICA (86%). The frequency of 37/40 kD antibodies was not significantly different between the 3 groups at risk, in contrast with GAD antibodies which were found at a lower frequency in schoolchildren (p < 0.02). Frequencies of other pancreatic markers (ICA cross-reactive with mouse pancreas and insulin autoantibodies) and the combination of ICA with at least two other markers were significantly higher in relatives than in the other groups at risk (p < 0.02). Out of 116 ICA-positive non-diabetic subjects, 10 developed diabetes. All 10 displayed 37/40kD and/or GAD antibodies during the prediabetic phase. In 8 of these 10 patients, ICA was combined with at least two other markers, whereas this association was detected in only 17 of the remaining 106 subjects who did not progress to diabetes (p < 10(-4). Thus, 37/40 kD antibodies were found in about half of Type 1 diabetic patients, and with a higher-frequency in Type 1b than 1a. In ICA-positive non-diabetic subjects, our date confirm that a combination of multiple antibodies, including GAD antibodies and 37/40 kD antibodies, can enhance the predictive value for diabetes. Comparison of ICA-positive relatives of diabetic patients, schoolchildren and patients with Graves' disease revealed distinct frequencies and combinations of markers of diabetes. This might reflect different patterns of progression among these 3 groups.

[Spontaneous animal models for insulin-dependent diabetes (type 1 diabetes)]

Insulin dependent (type 1) diabetes in humans is a polygenic, auto-immune disease that is characterized, among other things, by the infiltration of the islets of Langerhans by immune cells (insulite) as well as many serum auto-antibodies (including islet cell antibodies: ICA). The medical goal is to diagnose the condition at a sub-clinical stage and then to prevent the disease from developing. Spontaneous diabetic rodent models, in particular the NOD mouse and BB rat are invaluable to the continuing progress of the work aimed at better understanding the human disease. In addition to these models, the study of type 1 diabetes in larger animals, having a longer life-span would also be helpful. In dogs and cats, certain minor kinds of diabetes appear to be of type 1. The classification of diabetes types in carnivores remains poorly defined, however, epidemiological, genetic and metabolic studies are required before these diabetes can be used as operational models for the human pathology. Even if the classification of these diseases is clarified, the ethical and social considerations involved with the use of companion animals, will limit the use of these animals as models for spontaneous diabetes. The selection of a specific line of diabetic dogs should perhaps be considered.

Proteins spontaneously released by rat insulinoma (RIN) cells are anchored on cell membrane by a glycosyl-phosphatidyl-inositol link and inhibit increased RIN cell adhesion of lymphocytes from type 1 diabetic patients and non-obese diabetic mice in vitro

Our group previously reported an assay for the study of lymphocyte adhesion to insulin-producing cells in which xenogeneic rat insulinoma (RIN) cells were used as targets. The present study found an increased number of RIN-cytoadherent lymphocytes in 63 patients with Type 1 diabetes compared with 150 control subjects and in 211 NOD mice compared with 104 BALB/c mice (p < 0.001). Proteins concentrated from spontaneous RIN cell culture supernatants inhibited increased RIN-adhesion of NOD splenocytes or lymphocytes from diabetic patients (p < 0.001). In addition, increased RIN binding was dose-dependently abolished by RIN membrane extracts. The fact that RIN binding was inhibited by proteins from both membrane and the culture supernatant from RIN cells suggests that soluble inhibitory proteins were spontaneously released into the supernatant from a hydrophobic membrane-bound form. This tended to be confirmed since inhibition obtained with both preparations involved a 55-75 kDa HPLC protein fraction. The possibility that the membrane form of the inhibitory protein was anchored by a glycosylphosphatidylinositol (GPI) tail was evaluated. When RIN cells were treated with PI-PLC, their ability to bind lymphocytes from diabetic patients or NOD splenocytes decreased (p < 0.001) to control levels. Co-incubation with the 55-75 kDa fraction of proteins cleaved from RIN cells by PI-PLC also lowered the number of RIN-adherent NOD splenocytes to control levels. SDS-PAGE and IEF analyses of the 55-75 kDa inhibitory fraction from RIN cell supernatant revealed a major band with Mr 66 kDa and PI5.4, which may correspond to a protein with similar characteristics noted on 2-D electrophoresis of proteins cleaved from RIN cells by PI-PLC. Specific labelling of GPI moieties with 3H-ethanolamine, 3H-glucosamine, or 14C-glucosamine, as well as conversion of the hydrophobic Triton-X114 solubilised form into a hydrophilic form after PI-PLC treatment, confirmed the presence of a GPI anchor in this approximately 66 kDa RIN protein, which could thus be the molecule inhibiting adhesion in the system. Our data suggest that GPI-proteins from insulin-producing cells may influence the immune system both in their membrane-anchored and soluble forms. When considering the binding model, in which beta cells were tumoral and xenogeneic to diabetic lymphocytes, this potential influence of GPI-proteins suggests possible implications in situations of lymphocyte-beta cell interaction, i.e. anti-beta cell autoimmunity, immune reaction against insulinomas, and reaction against islet xenografts.

Prophylactic oral administration of metabolically active insulin entrapped in isobutylcyanoacrylate nanocapsules reduces the incidence of diabetes in nonobese diabetic mice

Nonobese diabetic (NOD) mice develop an autoimmune disease with a long prodromal period and constitute a model for investigating the prevention of human type 1 diabetes. Since prophylactic insulin injections reduced the incidence of diabetes in NOD mice, we tested a new prophylactic strategy to prevent diabetes in NOD mice consisting of oral administration of insulin, protected in polyalkylcyanoacrylate nanocapsules from degradation in the gastrointestinal tract. In humans, this form of prophylactic insulin administration would be less constraining than insulin injections. Ninety female NOD mice were randomized at weaning and fed once a week (from 60 to 300 days of age) with insulin nanocapsules (100 U/kg) or empty nanocapsules. Within the group fed with insulin nanocapsules, the incidence of diabetes was reduced (38% vs 75%; P < 0.02), the onset of disease was delayed (P < 0.02), and the severity of lymphocytic inflammation of endogenous islets was reduced (P < 0.03). Although the oral treatment was stopped at 300 days of age, the incidence of diabetes at 360 days remained lower in mice previously fed insulin nanocapsules (P < 0.02). Previous feedings with insulin nanocapsules did not protect against cyclophosphamide-induced diabetes, since final incidence of diabetes (sum of the incidence during the initial 360 days and the further CY-induced incidence) reached the final incidence obtained in mice previously fed empty nanocapsules and treated with cyclophosphamide. Intestinal absorption of insulin nanocapsules was evidenced by HPLC separation of human insulin in NOD sera. During cotransfer, T splenocytes from mice fed insulin nanocapsules were able to reduce the capacity of T cells from diabetic donors to adoptively transfer the disease (P < 0.01). Antigens for islet-cell autoantibodies (ICA) in pancreata from both NOD groups were compared by immunofluorescence with the same ICA-positive human sera to ensure that differences were due to quantitative changes in antigen. These antigens, which could serve as an index of a possibly more extended antigen beta-cell rest, were decreased (P < 0.02) and pancreatic insulin content was reduced (P < 0.05) in mice fed with insulin nanocapsules, suggesting a mechanism of 'beta cell rest'. To summarize, early feeding with insulin nanocapsules reduces diabetes and insulitis in the NOD mouse model that mimics human type 1 diabetes. This may be due both to generation of cellular mechanisms that actively suppress disease and a decrease in antigens which makes beta cells less vulnerable to autoimmune aggression.

Prevention of diabetes in the nonobese diabetic mouse by oral immunological treatments. Comparative efficiency of human insulin and two bacterial antigens, lipopolysacharide from Escherichia coli and glycoprotein extract from Klebsiella pneumoniae

As oral administration of insulin reduces the incidence of diabetes in NOD mice, and to achieve a better approximation of oral insulin trials being developed for human studies which will use human insulin, we attempted to determine the preventive efficacy of oral administration of human insulin rather than resorting to the animal insulins used in previous studies. As the strength of prevention obtained by oral insulin has not been adequately demonstrated, we determined whether the protection persisted after the oral treatment was discontinued and whether it was resistant to a diabetogenic injection of cyclophosphamide (CY). We also determined whether the effect of insulin could be increased by oral administration of lipopolysaccharide from Escherichia coli (LPS) or another immunostimulant (glycoprotein extracts from Klebsiella pneumoniae, GEKP) which may be more feasible for human application. Female NOD mice were fed once a week (from 35 to 300 days of age) with insulin, LPS, GEKP, insulin plus LPS, insulin plus GEKP, or PBS. A decreased incidence of diabetes were observed in animals fed human insulin (p < 0.01 incidence of diabetes at 300 days of age: 31% in mice fed with insulin and 65% in those fed PBS). Prevention by insulin was not enhanced by oral LPS or GEKP. Yet unexpectedly, mice fed with LPS alone or GEKP alone displayed decreases in diabetes incidence (p < 0.01). The severity of insulitis was reduced in animals fed insulin, LPS, GEKP or combinations of insulin and either immunostimulant (p < 0.02). Although the oral treatments were stopped at 300 days of age, the incidence of diabetes at 360 days remained lower in mice previously fed insulin, LPS, GEKP or combinations of insulin and either immunostimulant (p < 0.01). In mice previously fed PBS, CY injection (60 days after withdrawal of the oral treatment) led to a final incidence of diabetes of 90% (sum of the incidence during the initial 360 days and the further CY-induced incidence). Previous feedings with insulin, LPS, GEKP or combinations of insulin and either immunostimulant did not protect against CY-induced diabetes since incidences reached the final control incidence. T splenocytes from animals fed insulin, LPS, or GEKP, similarly reduced the capacity of T cells from diabetic mice to transfer the disease (p < 0.01). It is concluded that oral treatment with human insulin to be used in human trials reduces the incidence of diabetes in NOD mice. Equivalent preventive efficacy was obtained through feedings with LPS or GEKP (even though no cumulative efficiency was observed with insulin). The latter results suggest that it would be advisable to evaluate the efficiency of oral bacterial antigens for the prevention of human Type 1 diabetes. The protection afforded by oral treatments with insulin or bacterial antigens may be attributed to cellular suppression, persists for some time after treatments are stopped, but is not resistant to major immune stimulation such as injection of CY.

Immunization of non-obese diabetic (NOD) mice with glutamic acid decarboxylase-derived peptide 524-543 reduces cyclophosphamide-accelerated diabetes

NOD mice constitute a model for studying the prevention of human autoimmune type 1 diabetes. Glutamic acid decarboxylase (GAD) could be a key antigen involved in this disease, and GAD65 peptide 524-543 has been implicated in early T cell response in young NOD mice. We performed two i.p. injections of GAD peptide 524-543 (100 micrograms at each injection), together with Freund's incomplete adjuvant (FIA), into female NOD mice at 30 and 45 days old. Diabetes was accelerated 2 weeks later by a single injection of cyclophosphamide (CY), which acts against suppressive mechanisms. Treatment with GAD 524-543 peptide delayed the onset of diabetes and reduced its incidence (28% versus 60%; P < 0.001) compared with control mice injected with FIA alone, or GAD peptide 534-553, or an irrelevant peptide. In the same group, the severity of lymphocytic inflammation of pancreatic islets was reduced (P < 0.03). Up to 3 months after peptide injections, a strong splenocytic proliferative response occurred in immunized NOD mice against the immunizing peptide alone (but not against a panel of seven other GAD65-derived peptides). After peptide challenge of splenocytes in vitro, protection against CY-accelerated diabetes was associated with higher peptide-specific production of T helper type 2 (Th2)-associated interleukins 4 and 10, whereas Th1-associated interferon-gamma and IL-2 were proportionally less represented. During contransfer, T splenocytes from GAD 524-543-immunized mice were able to reduce the capacity of T cells from diabetic donors to transfer the disease adoptively (P < 0.01), demonstrating the generation of cellular mechanisms that actively suppress the disease. It is concluded that immunization of NOD mice with GAD65 peptide 524-543 can counteract CY-accelerated diabetes, possibly through active cellular suppression linked to a shift of Th1/Th2 balance toward the production of Th2 cytokines such as IL-4 and IL-10. This study provides additional support for the notion that GAD, and more precisely its epitope 524-543, could be one of the key targets for the pathogenesis of type 1 diabetes in NOD mice, as well as for the efficacy of disease-specific peptide therapy in type 1 diabetes.

Xenografts of porcine islets immunoprotected in hollow fibres reduce the incidence of diabetes in non-obese diabetic mice

Non-obese diabetic (NOD) mice develop an autoimmune disease with a long prodromal period and constitute a model for investigating the prevention of human insulin-dependent diabetes mellitus. Since insulin injected prophylactically has been shown to reduce incidence of diabetes in NOD mice, we tested a new strategy consisting of prophylactic xenografts of porcine pancreatic islets immunoprotected in semipermeable hollow fibres. Female NOD mice were transplanted twice (at 60 and 180 days of age) with islet-containing or empty fibres. Within the group grafted with protected islets, the incidence of diabetes was reduced (37 vs 75%; p < 0.01), the onset of disease was delayed (p < 0.02), and the severity of lymphocytic inflammation of endogenous islets was reduced (p < 0.02). When already diabetic mice were not taken into account for analysis, blood glucose level was slightly lower in those grafted with islet-containing fibres (p < 0.04). Graft function was also evidenced by HPLC separation of porcine insulin in NOD sera. Histological and perifusion studies of fibres retrieved from recipients confirmed immunoprotection. During co-transfer, T splenocytes from mice grafted with islet-containing fibres were able to reduce the capacity of T cells from diabetic donors to adoptively transfer the disease (p < 0.01). Antigens for islet-cell autoantibodies (ICA) in pancreata from both groups were compared by immunofluorescence with the same ICA-positive human sera to ensure that differences were due to antigen quantitative changes. These antigens, which could serve as an index of a possibly more extensive antigen beta-cell rest, were decreased (p < 0.01) in mice grafted with protected islets. Reduction of diabetes and insulitis following early islet transplantation may thus be due to generation of cellular mechanisms that actively suppress disease, and possibly in part to a decrease in antigens which make beta cells less vulnerable to autoimmune aggression. These effects can be obtained with xenogeneic islets protected in hollow fibres, thereby eliminating the need for immunosuppression. Based on the concept of prophylactic insulin therapy, this form of insulin administration offers a controlled means of delivering insulin to meet the physiological needs of recipients.

Differential beta-cell response to glucose, glucagon, and arginine during progression to type I (insulin-dependent) diabetes mellitus

Acute insulin responses to glucose (AIRG), glucagon (AIRGln), and arginine (AIRArg) were evaluated prospectively in nine subjects positive for islet-cell antibodies (ICAs) who later progressed to type I diabetes or impaired glucose tolerance (IGT) (progressors), 64 ICA-positive subjects at risk who did not develop type I diabetes, 365 ICA-negative relatives of diabetic patients who also remained free of the disease, and 89 control subjects. Seven progressors already had a low AIRG at entry into the study, and the other two became low responders 3 to 9 months before diabetes or IGT, with a progressive decline of AIRG over serial intravenous (IV) glucose tolerance tests. At entry into the study, the group of progressors displayed lower AIRG, AIRGln, and AIRArg than the other three groups (P<.001). However, AIRArg was less altered than AIRG. During the course of the prediabetic phase, there was a progressive decline in AIRG and AIRGln analyzed as a function either of time (P<.006) or of basal glycemia (P<.05), ie, two different ways of estimating worsening of the disease process. Conversely, there was no significant decrease in AIRArg with time or with increasing basal glycemia, so that AIRArg was not totally blunted in these prediabetic subjects even a few months before the onset of diabetes. The persistence of a substantial response to arginine, ie, higher than the fifth control percentile, even at a late stage, was confirmed in five of nine diabetic patients tested either at onset of the disease or during non-insulin-receiving remission. Whereas AIRG deteriorates during prediabetes, AIRArg appears to be less altered with time and increased basal glycemia, remaining substantial even at the onset of the disease. This reinforces the supposition that the prediabetic state may be associated with a glucose-specific beta-cell functional abnormality in addition to a decreasing beta-cell mass.

Cyclosporin depresses pancreatic islet expression of antigens for islet cell autoantibodies in non obese diabetic mice

An unexpected observation led us to investigate whether a short course (7 days) of oral cyclosporin (CsA) at different doses (5, 10, 20 or 40 mg/kg/day) in nonobese diabetic (NOD) mice could modify the expression of islet antigens related to the autoimmune process. Analysis was performed on the last day of CsA administration, and then up to 60 days after CsA withdrawal. Antigen modulation was analysed by indirect immunofluorescence using islet-cell antibody (ICA)-positive human sera for ICA antigens, and by immunoperoxidase for glutamic acid decarboxylase 67 Kd (GAD67). Concomitantly, beta-cell function was evaluated by in vivo glucose tolerance and insulin response from isolated islets. The severity of insulitis and histological damage to islets was quantified. We measured splenocyte and thymocyte subsets by cytofluorometry (CD4+ CD8-, CD4- CD8+, and double-positive thymocytes; Thy1-2+, CD3+, CD4+, and CD8+ spleen cells) and determined splenocyte mitogenesis in response to concanavalin A. Even when the lowest dose (5 mg/kg) was used, CsA concentrated in the islets. A graded reduction of ICA antigens was detected, showing no effect for 5 mg/kg/day but a significant dose-dependent reduction (P < 0.01) with 10, 20 and 40 mg/kg/day. GAD67 expression was also reduced (P < 0.03) in a CsA dose-dependent manner. On the other hand, only treatment with the highest CsA dose (40 mg/kg/day) induced glucose intolerance in vivo (P < 0.02), decreased insulin sensitivity to glucose from isolated islets (P < 0.03), reduced insulitis (P < 0.03), and altered thymocyte and splenocyte phenotypes and mitogenesis (P < 0.02). Moreover, the reversibility of the different effects was different: islet antigens were not completely recovered 2 months after CsA withdrawal, whereas other immunologic and metabolic effects obtained with the highest CsA dose were reversed within 15 days. Thus, a short course of low CsA doses in NOD mice produced a pancreatic concentration of the drug which reduced the expression of certain islet antigens for several weeks, whereas major effects on immunological parameters and islet insulin release occurred only with higher CsA doses and improved more rapidly.

Pancreatic expression of antigens for islet cell antibodies in non-obese diabetic mice

Diabetes-prone NOD mice of both sexes and at different ages were compared to control mice with regard to the level of pancreatic expression of certain autoantigens: antigens for islet cell antibodies (ICA antigens) and glutamic acid decarboxylase (GAD) 67 kDa. ICA antigens were compared by immunofluorescence using serial dilutions of ICA positive human sera so that differences of fluorescence intensity were due only to differences in amounts of antigen. Pancreatic GAD67 mRNAs were compared by polymerase chain reaction followed by Southern hybridization with 32P-probes and densitometry of autoradiographic bands. GAD67 product and gamma-aminobutyric acid (GABA) were compared by immunoperoxidase staining. As compared to BALB/c, C57BL6, Swiss, or F1 mice, NOD mice displayed higher ICA antigen levels (P < 0.01) both before and after insulitis onset (at 7 days, 15 days, 1 month, 2 months). ICA antigens were scarcely detectable by the first day of life, and increased with age from 7 days to 2 months (P < 0.01; n = 10 for each strain and at each age). Both before and after insulitis onset (4 days, 7 days, 15 days, 1 month, 2 months), amounts of GAD67 mRNAs were higher (P < 0.01) in NOD mice than in BALB/c mice (n = 8 for each age in each strain). This was already noted in foetuses on Day 18 of gestation (n = 8). After birth, amounts of GAD67 mRNAs increased up to 1 month (P < 0.04) and then decreased in older mice. The staining intensity of pancreatic sections with antisera against either GAD67 or GABA was higher (P < 0.04) in islets from NOD mice than in those from control mice. Whatever the age, no significant difference was noted between female and male NOD mice with regard to ICA antigens or GAD67. The expression of ICA antigens and GAD67 was intermediate in NOD x BALB/c F1 mice when compared to parental strains. We conclude that whatever the age, NOD mice strongly express ICA antigens and GAD67. This peculiarity was detectable very early, in embryos for GAD67 but after birth for ICA antigens. The timing of antigen expression may underlie the development of diabetes. The antigen overexpression might affect early completion of self-tolerance and, during later life, might also contribute to amplification of the anti-beta cell autoimmune response due to the existence of more targets for effector mechanisms.

Diabetes enhancement and increased islet antigen expression following neonatal injections of glucose and arginine in non-obese diabetic mice

Modulation of beta-cell antigens at birth may affect the course of type I diabetes. Since the functional state of beta cells modulates antigen expression, we investigated whether neonatal injections of glucose and arginine (G-A) influence diabetes in non-obese diabetic (NOD) mice. Two groups of 90 mice (45 female, 45 male) were injected for the first 6 days of life with G-A or saline. To determine whether these injections influenced beta cell functional maturation, isolated islets were characterized according to insulin response to glucose or arginine. Modulation of antigens for islet-cell autoantibodies (ICA antigens) was analyzed by indirect immunofluorescence using ICA-positive human sera. Variations of pancreatic glutamic acid decarboxylase 67-kD (GAD 67) mRNA were evaluated by polymerase chain reaction (PCR), hybridization with a 32P-labeled probe, and densitometry of the autoradiographic bands. Female NOD mice treated with G-A displayed diabetes earlier and with a higher incidence (P < .01) than control mice, whereas the diabetes incidence was not statistically modified in G-A-treated male NOD mice. Insulitis was more severe (P < .03) in 2-month-old G-A-treated female NOD mice than in control mice, but was not statistically modified in male NOD mice. In both sexes, ICA antigens and GAD 67 mRNA were higher in G-A-treated mice than in control mice (P < .01). Islets isolated after neonatal G-A injections exhibited improved insulin sensitivity to both stimuli (P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Combined analysis of islet cell antibodies that cross-react with mouse pancreas, antibodies to the M(r) 64,000 islet protein, and antibodies to glutamate decarboxylase in type I diabetic patients

OBJECTIVE

A combined analysis of whether islet cell autoantibodies (ICAs) are cross-reactive with mouse pancreas, with glutamate decarboxylase (GAD) antibodies, and with 64K antibodies was performed in a large sample of recently diagnosed type I diabetic patients. The disappearance rates of these different autoantibodies were compared in some patients after onset of the disease. The aims were to determine patterns in GAD/64K antibodies with regard to cross-species reaction of ICA and to assess whether GAD could contribute to ICA positivity in mouse and human pancreases and whether the simultaneous search for all the antibody specificities enhances the detection of autoimmune stigma.

RESEARCH DESIGN AND METHODS

ICA detected by immunofluorescence in human and mouse pancreases, antibodies immunoprecipitating the 64K rat islet antigen, and antibodies immunotrapping brain GAD activity were quantified at diagnosis of diabetes in 95 patients and in sequential samples during 1 year after diagnosis in 13 patients. The contribution of GAD to ICA positivity in mouse and human pancreases was evaluated by the analysis of correlations between tests and by the ability of brain homogenate to block ICA reactivity in pancreases from both species.

RESULTS

ICAs were detected in human pancreases in sera from 63 (66%) patients, among which 61% bound also to a mouse pancreas. GAD and 64K antibodies were strongly correlated (P < 0.0001) and were detected in 69 and 73% of the patients, respectively. All but two patients with ICA in human pancreas also displayed either ICA in mouse pancreas or GAD/64K antibodies. Among 32 patients without ICA in human pancreas, 54% displayed either GAD/64K antibodies or ICA in mouse pancreas. Only 16% of the patients displayed neither ICA nor GAD/64K antibodies. A correlation (P < 0.005) was found between ICA in human and mouse pancreases. GAD or 64K antibodies were strongly correlated with ICA in human pancreas (P < 0.0001), but not with ICA in mouse pancreas. After preincubation of six sera with GAD-containing brain homogenate, ICA titers were unaffected in mouse pancreas but reduced in human pancreas. ICA titers in mouse pancreas were decreased after 3 months (P < 0.01) in diabetic patients, contrasting with the stability of ICA in human pancreas and GAD antibodies by 1 year after diagnosis.

CONCLUSIONS

According to cross-species reaction, we confirm the heterogeneity of ICA in a large series of type I diabetic patients, ICAs that cross-reacted with mouse pancreas being more frequent than ICAs without cross-species reactivity. GAD and 64K antibodies were also present in a majority of patients. The simultaneous search for all the antibody specificities enhances the detection of autoimmune stigma so that only a few patients did not display any autoantibody at diagnosis. GAD is not the target of ICAs in mouse pancreas, whereas GAD accounts for ICA positivity in human pancreas. The conclusion that ICAs in mouse pancreas are not GAD-reactive is reinforced by the fact that they are more transient after onset of diabetes than are GAD antibodies or the complex mixture of ICAs in human pancreas.

Neonatal injections of cyclosporin enhance autoimmune diabetes in non-obese diabetic mice

Since the modulation of the immune system at birth may influence the course of insulin-dependent (type 1) diabetes, we investigated whether neonatal injections of cyclosporin (CsA) to newborn non-obese diabetic (NOD) mice influence diabetes during later life. Two groups of 90 mice (45 female, 45 male) were injected intraperitoneally for the first 6 days of life with CsA (10 mg/kg per day) or with vehicle. In female NOD mice, the onset of diabetes was earlier and cumulative incidence was higher after neonatal treatment with CsA (P < 0.01). The incidence of diabetes was also dramatically enhanced in male NOD mice (P < 0.01), which normally display a very low disease incidence. Concomitantly, the severity of lymphocytic infiltration of the pancreatic islets was higher in female NOD mice neonatally treated by CsA (P < 0.02), and to a lesser extent in males, than in control mice. After administration of CsA to newborn NOD mice, there was a reduction (P < 0.01) of both CD4+CD8- and CD4-CD8+ thymocytes, whereas the number of double positive CD4+CD8+ thymocytes was increased. Concomitantly, Thy1-2+ cells in spleen were decreased (P < 0.01), and spleen cells expressing either CD3 molecule or alpha beta TCR complex were diminished (P < 0.01). Both CD4+ and CD8+ spleen T cells were depleted. By contrast, the low percentage of gamma delta TCR-expressing splenocytes was not modified. Numbers of MHC class 1+ or MHC class 2+ spleen cells were also depressed (P < 0.01). After neonatal injections of CsA, spleen cells showed a reduced response to concanavalin A (Con A) (P < 0.01). On the contrary, stimulation indices of splenocytes incubated with xenogeneic insulin-producing cell extracts were enhanced (P < 0.03). Proliferation indices of splenocytes to self class 2 antigens, generating suppressor cell activity, during syngeneic mixed lymphocyte reaction (SMLR) were significantly reduced (P < 0.01). Irradiated NOD mice were used as recipients for spleen cells from CsA-neonatally treated NOD mice. They displayed enhanced insulitis 2 weeks after transfer, and diabetes was successfully produced by 1 month after transfer in 50% of the recipients. By contrast, NOD mice which received control syngeneic spleen cells remained normoglycaemic, with only moderate islet infiltration which would be expected of NOD mice of this age. Thus, neonatal injections of CsA markedly enhance diabetes in both female and male NOD mice.(ABSTRACT TRUNCATED AT 400 WORDS)

T-splenocytes from non-obese diabetic mice binding to xenogeneic pancreatic beta-cells in vitro. Implication of the alpha/beta T-cell receptor and of major histocompatibility complex class II molecules from target cells

As compared to several strains of control mice, NOD mice displayed an increased number (P < 10(-4)) of splenocytes binding in vitro to xenogeneic rat RIN cells or hamster HIT cells, but not to nine non-beta cell lines. The increased binding to RIN cells was abolished by competition with RIN membrane extracts. It was prevented by depletion of Thy 1-2+ splenocytes, and by blocking the T-cell receptor (TCR) complex with anti-CD3 MoAbs, anti-alpha/beta TCR MoAbs, or their F(ab)'2 fragments (P < 10(-3)), but not with anti-gamma/delta TCR MoAbs. Neither anti-V beta 8 nor anti-V beta 6 MoAbs modified the signal. MoAbs against rat MHC class II molecules, but not MoAbs against rat class I molecules, inhibited the increased RIN-adhesion of NOD splenocytes (P < 10(-3)). After 3 h or 8 h of co-incubation, the number of RIN-binding splenocytes was not different between NOD and control mice, and class II molecules were undetectable on RIN cells. Class II+ RIN cells appeared after 20 h of coculture when the increased binding was also observed. When 10,000 rad-irradiated RIN cells were used for the co-incubations, neither class II+ RIN cells nor the increased binding of NOD splenocytes were found. As revealed by immunofluorescence, MoAbs against rat class II molecules cross-reacted with 30% of NOD (but not of control) splenocytes. Conversely, anti-NOD class II MoAbs (but not MoAbs against non-NOD class II molecules) cross-reacted with 20% of RIN cells coincubated with splenocytes. Thus, despite the species barrier, T-splenocytes from NOD mice display an increased adhesion to xenogeneic beta-cells. This binding involves T splenocytes bearing alpha/beta TCRs and RIN cells induced to express MHC class II molecules. MHC restriction may be completely absent in this phenomenon. Alternatively, the rat class II products may be directly recognized by NOD T cells in a xenograft context, and this model may therefore be useful toward the comprehension of some mechanisms leading to the rejection of islet xenotransplants. Finally, because of a cross-reaction with I-Anod, these rat Class II molecules may also either be directly recognized by I-A autoreactive NOD T cells or present RIN peptides to NOD alpha/beta TCRs, and thus would be relevant to the debated ability of beta cells to function as antigen-presenting cells.

Release of carcinoembryonic antigen from human tumor cells by phosphatidylinositol-specific phospholipase C: highly effective extraction and upregulation from LS-174T colonic adenocarcinoma cells

Carcinoembryonic antigen (CEA), produced by gastrointestinal tumor cells, is anchored to cell membrane by a glycosyl-phosphatidylinositol moiety which can be cleaved with phosphatidylinositol-specific phospholipase C (PI-PLC). We studied the extraction of CEA from living human colon carcinoma (LS-174T, HT-29, COLO-205, and HRT-18) and pancreatic carcinoma (CAPAN) cells by PI-PLC from Bacillus cereus. The total CEA content of LS-174T cells, quantitated by Triton X-114 extraction followed by radioimmunoassay or by immunohistochemistry, was 3.5-fold higher than that of other cells (P < 0.001). The spontaneous release of CEA from LS-174T cells into culture medium was also higher than from other cells (P < 0.001), reaching 620 ng/10(7) cells (approximately 28% of cellular content) after 24 h. Overall, living LS-174T cells were highly susceptible to CEA extraction by PI-PLC, which was dependent on PI-PLC dose and on treatment time, leading in optimal conditions to the solubilization of 4100 ng/10(7) cells after 24 h (approximately 75% of total CEA). After 24 h treatment at the highest PI-PLC dose, cell lines remained viable and growing, and membrane CEA expression was not exhausted but only reduced as compared to untreated cells. At the same time, the amount of CEA solubilized by PI-PLC exceeded the CEA reduction in membranes, suggesting that enzyme treatment increased CEA turnover. This was particularly true for LS-174T cells which maintained 54% of the expression of untreated cells, whereas the amount of CEA extracted by PI-PLC reached 190% of this expression. Growing LS-174T cells thus constitute an effective material for producing high quantities of CEA by PI-PLC cleavage, especially since these cells probably "regenerate" because of enhanced turnover during PI-PLC action, thus allowing continuous CEA production. These experimental conditions also provide an interesting model for studying the modulation of CEA expression and release.

Quantification of human cytoplasmic islet-cell antibodies which cross-react with mouse pancreas: a follow-up study in type 1 (insulin-dependent) diabetic patients and in first-degree relatives

We studied the heterogeneity of cytoplasmic islet-cell antibodies for cross-reaction with mouse pancreas in 31 recent-onset Type 1 (insulin-dependent) diabetic patients and 31 first-degree relatives with islet-cell autoantibodies detected on human pancreas. Only six Type 1 diabetic patients displayed islet-cell antibodies binding to human pancreas but not to mouse pancreas. Among 15 first-degree relatives displaying such antibodies which did not react with mouse pancreas, including one identical twin and one subject with polyglandular autoimmunity, none developed diabetes or even lost acute insulin response to intravenous glucose after 5 years of follow-up. By contrast, 14 of 20 (70%) of the Type 1 diabetic patients with islet-cell antibodies detected on human pancreas, and five first-degree relatives who progressed to a loss of acute insulin response to glucose and then to either Type 1 diabetes or glucose intolerance, also displayed antibodies reactive with mouse islets. Surprisingly, islet-cell antibodies were detectable on mouse pancreas but not on human pancreas in four Type 1 diabetic patients and in one relative who progressed to diabetes. In the five relatives who progressed to metabolic abnormalities, islet-cell antibody titres on mouse pancreas, quantified by the fluorescence intensity per islet at each serum dilution, progressively increased concomitantly with the loss of acute insulin response to glucose, whereas islet-cell antibody titres on human pancreas remained stable. The usefulness of such quantification was also validated by the fact that antibody titres on mouse pancreas were decreased after 3 months (p < 0.01) in recent-onset Type 1 diabetic patients, while titres on human pancreas were not.(ABSTRACT TRUNCATED AT 250 WORDS)

[Detection of subjects at risk of type 1 diabetes. GOFEDI. Groupe Ouest-France pour l'Etude du Diabète Insulino-dépendant]

The so-called type 1 (insulin-dependent) diabetes is an autoimmune disease occurring in genetically predisposed subjects. The clinical onset of the disease is preceded by a subclinical period during which insulin-producing cells are progressively destroyed by immunological effectors. This prediabetic phase can be detected by the presence of autoantibodies directed against islet cells and sometimes associated with anti-insulin antibodies in children, and later on by the disappearance of the early insulin secretion peak in response to intravenous glucose. It is at this prediabetic phase that immunomodulators specific to the antipancreas process and devoid of side-effects will be used, when available, and that an early insulin therapy will be instituted.

Acute insulin response to intravenous glucose, glucagon and arginine in some subjects at risk for type 1 (insulin-dependent) diabetes mellitus

The relationships between first-phase insulin secretion to i.v. glucagon and i.v. arginine were studied in 19 healthy adult volunteers (Group I) and in 21 subjects at risk for Type 1 (insulin-dependent) diabetes mellitus with either a "normal" (n = 11; Group IIa) or a "low" insulin response to i.v. glucose (n = 10; Group IIb). Groups I and IIa displayed similar insulin responses to the three secretagogues. In contrast, Group IIb demonstrated lower insulin responses to both glucagon and arginine than control subjects (p less than 0.007 and p less than 0.04 respectively) or than "normo-responders" to glucose (p less than 0.007 and p less than 0.04 respectively). In Group IIb however, arginine-stimulated insulin release was increased compared to the response to glucose (p less than 0.006), while glucagon and glucose led to non-statistically different responses. Five "low-responders" developed Type 1 diabetes. As a group, they displayed lower responses to glucagon and to arginine than subjects who up to now have not developed the disease (p less than 0.05 and p less than 0.0003 respectively). In the subjects who progressed to diabetes, the responses to glucose and glucagon were similarly blunted. In the "low-responders" who have not developed the disease, no statistical difference could be detected between mean responses to glucagon and glucose, but four out of these five subjects had a glucagon-stimulated response within the control range and higher than their corresponding response to glucose. Arginine led to a higher stimulation than glucose, in subgroups that either progressed to diabetes (p less than 0.006) or did not (p less than 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Heparin attenuates low-dose streptozotocin-induced immune diabetes in mice and inhibits the beta-cell binding of T-splenocytes in vitro

Five low doses (40 mg.kg-1.day-1) of streptozotocin were given to CD-1 mice to induce "immune" diabetes with insulitis. T-splenocytes (L3T4+ and Lyt2+) from streptozotocin-treated mice were previously reported to display in vitro an increased binding for Beta cells, preceding the onset of hyperglycaemia and of insulitis. Since heparin inhibits lymphocyte traffic, displays anti-adhesive properties, and attenuates some cell-mediated immune diseases, we have investigated the effects of heparin and N-desulphated heparin: 1) in vivo on low-dose streptozotocin-induced diabetes and insulitis, and 2) in vitro on the increased binding of T-splenocytes from streptozotocin-treated mice to rat insulinoma (RINm5F) cells. Daily subcutaneous low doses (5 micrograms or 10 micrograms) of heparin induced a delay in onset and a reduction of the severity of hyperglycaemia and insulitis (p less than 0.01), and reduced the incidence of diabetes (p less than 0.01). Similar effects were obtained with 5 micrograms daily doses of N-desulphated heparin devoid of anticoagulant activity. In contrast, lower (1 microgram) or higher (200 micrograms) doses of heparin were ineffective. Heparin (10 micrograms) did not modify the "toxic" diabetes induced by a single high dose (200 mg/kg) of streptozotocin. On the other hand, heparin dose-dependently (0.1 microgram/ml to 500.0 micrograms/ml) inhibited the increased binding of splenocytes from streptozotocin-injected mice to RIN cells as compared to splenocytes from control mice. This in vitro anti-adhesive effect was detected when either splenocytes or RIN cells were pretreated with heparin before their co-incubation, and was also obtained with N-desulphated heparin.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-pancreatic immunity. In vitro studies of cellular and humoral immune reactions directed toward pancreatic islets

It has been suggested that the immune system may be responsible for the destruction of insulin secreting cells in some types of diabetes. In order to test this hypothesis, we studied the consequences of immune-mediated reactions on the function of pancreatic islet cells in vitro. A model was set up in vitro where mouse pancreatic islet cells are exposed to human lymphocytes or sera + complement then stimulated for the release of insulin or glucagon. A selective inhibition of insulin secretion, but not of glucagon secretion, was observed in the presence of lymphocytes from 37 out of 40 insulin-dependent diabetic (IDD) patients and in the presence of sera (+ complement) from 22 out of 40. Lymphocytes were found inhibitory in almost all patients in both groups, with and without associated autoimmune diseases. In contrast, inhibitory sera were observed almost only in patients with associated autoimmune diseases or recent onset diabetes. The selective inhibition of insulin secretion, but not of glucagon secretion, suggests that lymphocytes or sera may be involved in a destructive process of insulin secreting cells in vivo. This cell-mediated effect depends on direct T lymphocyte cytotoxicity, rather than antibody-dependent cell cytotoxicity, as suggested by the lack of any effect of aggregated immunoglobulins on the reaction. In contrast, when C57BL/6 mice were immunized by mastocytoma cells from a DBA2 strain, their lymphocytes and sera blocked both secretions of insulin and glucagon when incubated in vitro with DBA2 islet cells. This non-selective inhibition may be due to anti-H2 immunity, rather than immunity directed against insulin secreting cells.

Pentamidine, a new diabetogenic drug in laboratory rodents

The antiprotozoal drug, pentamidine, has been reported to induce hypoglycaemia associated with inappropriately high plasma insulin concentrations, followed by insulin-dependent diabetes mellitus. It has been suggested that this drug can be toxic to the islet B cell, inducing early cytolytic release of insulin leading to B cell destruction. In order to test this hypothesis, mouse and rat islets were incubated with pentamidine at concentration range of 5 x 10(-11) to 5 x 10(-3) mol/l and exposure times of 3-48 h. The B cell responses to glucose + theophylline and to arginine were suppressed by pentamidine, while insulin release in non-stimulatory conditions was increased. These effects were dose-dependent, time-dependent and irreversible. They were significant for 5 x 10(-7) mol/l pentamidine, which is a concentration relevant to therapeutic uses. These effects developed more slowly than the toxic effects of streptozotocin and alloxan at the same molar concentration in vitro. 51Chromium release and Trypan blue exclusion tests support the hypothesis that pentamidine produces islet cell necrosis.

Anti-pancreatic immunity in genetically diabetic mice

The anti-pancreatic immune reaction of genetically diabetic homozygote C57Bl/KsJ db/db mice was studied with an in vitro test using murine islet of Langerhans cells as target cells. C57Bl/KsJ db/db spleen lymphocytes inhibited insulin secretion by the islet cells. This inhibition was abolished when T cells were eliminated by treatment with anti-Thy 1.2 monoclonal antibody in the presence of complement. Together with this cell-mediated cytotoxicity, complement-dependent antibody (CDA) and antibody-dependent cell cytotoxicity (ADCC) were found in the sera of these mice. A longitudinal study showed that this anti-pancreatic toxicity was detectable as early as the 10th day of life and lasted throughout the entire life span of the animal. None of these anomalies was found in control heterozygote mice.