The Pig as the Donor of Pancreatic Islets for Men

The promising results obtained using the "Edmonton protocol" for human islet transplantation has resulted in increased interest and growth of various clinical and basic science programs worldwide. Despite these encouraging results two major drawbacks remain: first, the immunosuppressive regimen necessary to prevent the rejection of this allotransplant dramatically affects the lifestyle of the treated patients precluding its implementation in younger diabetic individuals. Second, there continues to be an inadequate amount of islet tissue available to fulfill the needs of an increasing population of diabetic patients possibly interested in receiving this type of treatment. Besides the limited number of cadaveric organ donors, the current procedure used to isolate islets from their pancreata activates metabolic processes that promote the loss of beta cells in the islets. Thus, it becomes necessary to use more than one donor for a single recipient. To fulfill the continuously growing need for more transplantable islets, an immediately available, unlimited source of islets may be found in animals, which are able to produce a type of insulin that is very similar to the human one, and carry islets in quantities that may satisfy the metabolic requirements of diabetic patients: the pigs.

Suitability of human juvenile pancreatic islets for clinical use

AIMS/HYPOTHESIS

The limited availability of deceased donor pancreases suitable for pancreas and islet transplantation calls for a broader utilisation of donor tissue for transplantation purposes. Young donors, representing, fortunately, a minor but significant pool of individuals, have been largely under-employed, mainly because of anatomical and functional incompatibilities with potential recipients. For islet transplantation, the isolation of pancreatic islets from young donors rarely occurs, because of technical problems. As a result of the peculiar characteristics of young donor pancreases, the standard isolation procedure does not allow efficient separation of the islets from the surrounding exocrine tissue, and favours the generation of mantled islets. Nonetheless, young donor islets offer high qualitative and clinically appealing characteristics.

SUBJECTS AND METHODS

We standardised a modified methodology to obtain purified and mantle-free human islets from young donors. This method principally involves efficient delivery of isolation enzyme with reduced mechanical disruption of the pancreas combined with additional filtration steps.

RESULTS

We were able to obtain purified and mantle-free human islets from donors as young as 6 months of age with good morphological and functional properties. The good qualitative characteristics of the islets, evidenced in vitro, were proven in vivo, as they were qualitatively superior to islets of older donors in transplantation studies.

CONCLUSIONS/INTERPRETATION

This study justifies the utilisation of islets derived from young donors for islet transplantation.

Pig-to-nonhuman primate islet xenotransplantation: a review of current problems

Islet allotransplantation has been shown to have potential as a treatment for type 1 diabetic patients. Xenotransplantation, using the pig as a donor, offers the possibility of an unlimited number of islets. This comprehensive review focuses on experience obtained in pig-to-nonhuman primate models, particularly with regard to the different types of islets (fetal, neonatal, adult) and isolation procedures used, and the methods to determine islet viability. The advantages and disadvantages of the methods to induce diabetes (pancreatectomy, streptozotocin) are discussed. Experience in pig-to-nonhuman primate islet transplantation studies is reviewed, including discussion of the possible mechanisms of rejection and the immunosuppressive regimens used. The research carried out to date has led to workable animal models to study islet xenotransplantation, but several questions regarding methodology remain unanswered, and details of these practicalities require to be adequately addressed. The encouraging porcine islet survival reported recently provides an indicator for future immunosuppressive regimens.

Efficient gene delivery to human and rodent islets with double-stranded (ds) AAV-based vectors

Transplantation of allogeneic pancreatic islets is an effective approach to treat type 1 diabetes. To bypass the need for systemic administration of immunosuppression drugs following transplantation, approaches to genetically modify allogeneic islets to express anti-inflammatory, immunosuppressive, or antiapoptotic proteins prior to transplantation are being developed. Adeno-associated viral (AAV) based vectors have been used for gene transfer to islets, but the efficiency of functional transduction is low. Recently, double-stranded (ds) or double-copy (dc) based AAV vectors have been developed that allow for more rapid and efficient AAV-mediated transgene expression following transduction. Here we demonstrate that intact human and murine islets can be transduced with dsAAV2-eGFP efficiently compared to single-stranded AAV2-eGFP. Furthermore, our results demonstrate that murine islets transduced with dsAAV2-eGFP have normal islet glucose responsiveness, viability, and islet insulin content. Transplantation of the dsAAV2-eGFP transduced islet restored normal glycemia in diabetic mice without eliciting an immune response. Significant dsAAV2-mediated eGFP expression was observed in the islet grafts for at least 6 months post-transplant. Finally, we demonstrated that dsAAV serotypes 2, 6, and 8 infect human islets efficiently. Taken together, these results suggest that dsAAV based vectors are highly appropriate for gene transfer to islets to facilitate transplantation.

DNA vaccination with an insulin construct and a chimeric protein binding to both CTLA4 and CD40 ameliorates type 1 diabetes in NOD mice

Type 1 diabetes (T1D), a T-cell-mediated autoimmune disease, could be attributed to many defects in nonobese diabetic (NOD) mice, including deficient expressions of costimulatory molecules that impair antigen presentation. Thus, this deficient antigen presentation may result in a reduced ability to induce a tolerogenic response through negative selection/regulation of autoreactive T cells. Improperly activated T cells seem to be able to induce autoimmune responses causing diabetes. To re-establish tolerance to autoantigens by modulating costimulation, we constructed and tested a new type of DNA vaccine encoding a membrane-bound preproinsulin (mbPPI) and a chimeric gene vector encoding mutant B7.1/CD40L (mB7.1/CD40L) fusion protein. This mutant B7.1 binds CTLA4 but not CD28. We report that young NOD mice immunized with mbPPI along with mB7.1/CD40L DNA vectors significantly reduced diabetes incidence while treatment with CTLA4/IgG1 exacerbated diabetes. In conclusion, the combination of mbPPI and mB7.1/CD40L was able to protect against autoimmunity and diabetes in NOD mice possibly by promoting a more efficient presentation of autoantigen PPI and inducing specific tolerance to PPI by negatively regulating autoreactive T cells.

Prolongation of islet allograft survival following ex vivo transduction with adenovirus encoding a soluble type 1 TNF receptor–Ig fusion decoy

Islet transplantation is a viable long-term therapeutic alternative to daily insulin replacement for type I diabetes. The allogeneic nature of the transplants poses immunological challenges for routine clinical utility. Gene transfer of immunoregulatory molecules and those that improve insulin release kinetics provides rational approaches to facilitate allogeneic islet transplantation as a potential therapy. We have examined the efficacy of a soluble type 1 tumor necrosis factor receptor (TNFR) immunoglobulin-Fc fusion transgene (TNFR-Ig) to protect human islets from cytokine-induced apoptosis in culture, as well as in facilitating allogeneic islet transplants in diabetic mice. Cultured human islets were transduced with an adenoviral vector encoding human TNFR-Ig (Ad-TNFR-Ig). TNFR-Ig protein was secreted by cultured islets, as well as by transduced mouse islet transplants recovered from mouse recipients. Glucose-induced insulin release kinetics were comparable among untransduced, Ad-TNFR-Ig-infected human islets and vector-transduced islets exposed to cytokines. In parallel, Ad-TNFR-Ig-infected islets were protected from cytokine-induced apoptosis activation. Finally, diabetic mice transplanted with allogeneic islets expressing TNFR-Ig returned to and maintained normoglycemia significantly longer than untransduced islet recipients. These data support the potential utility of TNFR-Ig gene transfer to islets as a means of facilitating allogeneic islet transplantation.

Gene- and cell-based therapeutics for type I diabetes mellitus

Type 1 diabetes mellitus, an autoimmune disorder is an attractive candidate for gene and cell-based therapy. From the use of gene-engineered immune cells to induce hyporesponsiveness to autoantigens to islet and beta cell surrogate transplants expressing immunoregulatory genes to provide a local pocket of immune privilege, these strategies have demonstrated proof of concept to the point where translational studies can be initiated. Nonetheless, along with the proof of concept, a number of important issues have been raised by the choice of vector and expression system as well as the point of intervention; prophylactic or therapeutic. An assessment of the current state of the science and potential leads to the conclusion that some strategies are ready for safety trials while others require varying degrees of technical and conceptual refinement.

Glutamic acid decarboxylase and ICA512/IA-2 autoantibodies as disease markers and relationship to residual beta-cell function and glycemic control in young type 1 diabetic patients

Circulating autoantibodies (Ab) to islet autoantigens, glutamic acid decarboxylase (GAD(65)), and tyrosine phosphatase ICA512/IA-2 have been proposed as predictive markers of type 1 diabetes mellitus. To ascertain residual beta-cell function and the clinical relevance for monitoring autoimmunity after clinical manifestation of disease, we studied 63 children at diagnosis of type 1 diabetes (mean SD age 7.5 +/- 4 years) and 91 adolescent patients with type 1 diabetes (age 14.7 +/- 1.6 years) with a mean duration of disease of 7 +/- 3.5) years. Forty-two normal adolescent subjects (age 14.6 +/- 1.8 years) without a family history of diabetes were the control group. Anti-GAD(65) and ICA512/IA-2 Ab were assessed by a quantitative radioimmunoprecipitation assay. The relationship between humoral autoimmunity and clinical parameters was explored. GAD(65) and ICA512/IA-2 Ab were detected in 56% and 63% of newly diagnosed children and the prevalence was not different in relationship to clinical characteristics. Levels of GAD(65) Ab positively correlated with diagnosis age (P <.05). Both Ab were associated with islet cell antibodies (ICA) (P <.05), but one fifth of patients had at least 1 of the 2 Ab and absent ICA. At onset, only age showed a significant relationship to residual C-peptide secretion. Among the cohort of patients with diabetes of short-mid duration, GAD(65) and ICA512/IA-2 Ab were present in 44% and 45% of cases (P >.05 and P <.05 v newly diagnosed children, respectively) and more patients were identified by these Ab (68%) than by ICA alone (34%) (P <.05). In this cohort, levels of ICA512/IA-2 Ab negatively correlated with levels of glycosylated hemoglobin (HbA(1c)) (P <.005) and with daily insulin requirement (P <.05). Moreover, the presence of some residual C-peptide secretion was significantly associated with the presence of ICA512/IA-2 Ab (P <.05). Our findings confirm that positivity for either GAD(65) or ICA512/IA-2 Ab is a highly sensitive marker of type 1 diabetes in the pediatric age group, identifying a group of patients with absent ICA immunofluorescence. The persistence of Ab to islet tyrosine phosphatase possibly represents a marker of better glycemic control and less insulin requirement, indicating residual beta-cell function, thus conferring clinical and prognostic relevance to these Ab, as well as potential usefulness in intervention strategies.

Maintaining updated DNA-based HLA assignments in the National Marrow Donor Program Bone Marrow Registry

The National Marrow Donor Program (NMDP) has instituted an approach to address the impact of new alleles on the DNA-based HLA assignments obtained during volunteer donor typing. This approach was applied to the DRB typing results from 371,187 donors received from 14 laboratories in 1999. Samples were tested with a standardized set of sequence specific oligonucleotide reagents and the positive and negative hybridization results transmitted electronically to the NMDP. A software program interpreted the primary data into HLA assignments and rejected assignments which did not produce a result at the specified level of resolution. Comparison of the HLA assignments derived by the NMDP software to the assignments made by the laboratories using several local software prograins showed 90.5% of the assignments to be identical. Differences in assignments were explained by varying levels of typing resolution, variation in the inclusion of the second expressed DRB loci, disparity arising when alternative assignments were summarized, and failure to submit correct information. When the primary data collected in 1999 were interpreted into HLA assignments using the set of alleles defined in July 2000, 74% of the HLA-DRB assignments were altered by the description of new alleles, justifying the development of this software.

Pyrosequence-based typing of alleles of the HLA-DQB1 gene

DNA typing of alleles of the highly polymorphic HLA-DQBI gene was performed by Pyrosequencing using purified DNA from the 11th International Histocompatibility Workshop human cell lines and samples from the Children's Hospital of Pittsburgh registry of diabetics and their first-degree relatives. Pyrosequencing was optimized for genotyping exon 2 of the HLA-DQB1 gene, but the procedure should be applicable to other HLA loci. The 47 HLA-DQB1 alleles were readily identifiable, as were the 1,128 potential allelic heterozygous combinations. The method required PCR conditions that specifically amplified DQB1 but not the pseudogene, DQB2. The new method of pyrosequence-based typing can be performed in 96- or 384-well format. The 61 polymorphic residues of DQB1 exon 2 were identified within four pyrosequencing reactions, obtained by a 70-nucleotide read length in each reaction, in about an hour's time. Allelic combinations of HLA-DQB1 most frequentlyfound in the population of diabetics and their immediate family members were analyzed and successfully compared to typing of the DQB1 alleles by sequence-specific oligonucleotide probe protocols. Pyrosequence-based typing is compatible with genotyping of allelic combinations expected from heterozygous individuals, resulting in nucleotide resolution of the highly polymorphic HLA system. Using pyrosequencing, more than 750 sample wells can be processed in a working day, resulting in the identification of more than 50,000 bases.

Therapeutic strategies for Type 1 and Type 2 diabetes mellitus

Although diabetes mellitus is a manageable disorder, the associated complications that result in significant morbidity and mortality worldwide necessitate novel approaches of pharmacologic, cell, and gene therapy for an eventual cure. A significant number of animal studies have demonstrated the potential of restoring normoglycemia by islet transplantation in the context of immunoregulation achieved by gene transfer of immunoregulatory genes to allo- and xenogeneic islets ex vivo. Examples include viral vector-mediated gene transfer of immunosuppressive cytokines, proteins that block co-stimulation and molecules that prevent apoptotic cell death. Additionally, gene and cell therapy has also been used to induce tolerance to auto- and alloantigens and to generate the tolerant state in autoimmune rodent animal models of Type 1 diabetes mellitus (T1DM) or rodent recipients of allogeneic/xenogeneic islet transplants. Gene transfer of putative autoantigens is one example. The achievements of gene and cell therapy in Type 2 diabetes mellitus (T2DM) are less evident, but seminal studies promise that this modality can be relevant to treat and perhaps prevent the underlying causes of the disease including obesity and insulin resistance. Herein, we present an overview of the current status of drug, gene and cell therapy for T1DM and T2DM and we propose novel therapeutic options that could be clinically useful.

Is type 2 diabetes a chronic inflammatory/autoimmune disease?

The classification of diabetes mellitus into 2 main types, defined as Type 1 and 2 diabetes (T1DM, T2DM) relies mostly on the requirement of insulin therapy and on the presence of detectable immunologic abnormalities. However, this distinction is far from straightforward and there is considerable overlap between these 2 types of diabetes. Islet cell autoimmunity, which is characteristic of T1DM, appears in fact to be present in up to 10-15% of subjects diagnosed clinically with T2DM. In the UK Prospective Diabetes Study (UKPDS), it was reported that in patients diagnosed with in T2DM, the presence of autoantibodies to the enzyme glutamic acid decarboxylase (GAD) and cytoplasmic islet cell antibodies (ICA) were a predictor of insulin requirement as compared with patients not carrying these autoantibodies. These results are strikingly similar to a number of prospective studies carried out in childhood diabetes. If islet cell autoimmunity is truly present in 10-15% of subjects clinically diagnosed with T2DM, up to two million Americans might have an unidentified autoimmune form of T2DM, a prevalence similar to that of recent onset childhood diabetes. In addition, we found that in a subset of T2DM patients, a pronounced activation of the acute phase response that seems to be associated with islet cell autoimmunity. These results may in part explain the defect in insulin secretion as well as insulin resistance seen in T2DM. The identification of a subgroup of individuals at risk of developing T2DM using autoantibody as well as inflammatory markers is of public health interest, not only for the correct classification of diabetes, but also because immunomodulatory therapeutic strategies could potentially be instituted sufficiently early in a large number of patients diagnosed as having T2DM and most likely delay the onset of insulin requirement and the complications related with hyperglycemia.

Normal pregnancy is associated with peripheral leukocyte activation

PROBLEM

Normal pregnancy has been described as both a pro-inflammatory condition and a T helper (Th)2-dominated state. Deviations in the percentage of different subpopulations of circulating leukocytes have been detected, although with conflicting results. This study was designed to analyse further the phenotype of subpopulations of peripheral blood leukocytes in normal pregnant women.

METHOD OF STUDY

Whole-blood flow cytometry was used to differentiate subsets of leukocytes using directly labeled monoclonal antibodies to specific cell surface antigens and to a panel of activation-associated markers in 33 normal pregnant women in their third trimester and in 26 non-pregnant controls.

RESULTS

We found a significant increase in the proportion of granulocytes and of CD8+ T lymphocytes during pregnancy. Up-regulation of the expression of adhesion molecules was observed on granulocytes, monocytes and T lymphocytes.

CONCLUSIONS

Pregnancy alters the representation of leukocyte subpopulations in the maternal circulation and is associated with systemic activation of leukocytes.

Progression to insulin-requiring diabetes in seronegative prediabetic subjects: the role of two HLA-DQ high-risk haplotypes

AIMS/HYPOTHESIS

Most Caucasians with Type I (insulin-dependent) diabetes mellitus develop an autoimmune form of diabetes known as Type IA diabetes, based on the presence of humoral responses to islet autoantigens. Alleles at the HLA locus account for the strongest susceptibility to this form of diabetes, which requires insulin therapy. Because a number of patients who develop insulin-requiring diabetes are islet autoantibody negative, the HLA class II haplotypes, DQA1*0501-DQB1*0201 and DQA1*0301-DQB1*0302, were evaluated to assess whether they are an independent risk factor for progression to insulin requirement in first-degree relatives of Type I diabetic patients.

METHODS

Both HLA-DQ genotyping and islet cell autoantibody assessment (insulin, GAD65, IA-2 autoantibodies and cytoplasmic islet cell antibodies) were evaluated prospectively in 74 relatives of Type I diabetic patients who developed diabetes treated with insulin (prediabetics) and in 426 control subjects who did not develop insulin-requiring diabetes. Based on the presence of DQA1*0501-DQB1*0201 and/or DQA1*0301-DQB1*0302, the number of HLA-DQ high-risk haplotypes was assigned as 0, 1 or 2.

RESULTS

A higher prevalence of 2 HLA-DQ high-risk haplotypes was present in seronegative prediabetic subjects as compared to non-diabetic autoantibody negative first-degree relatives (33.3 % vs 10.1 % respectively; p < 0.05). Moreover, in seronegative relatives who developed insulin-requiring diabetes, the presence of 2 HLA-DQ high-risk haplotypes conferred an increased cumulative risk of developing insulin requirement of 27 % at 12.5 years of follow-up, compared to a risk of 6 % for non-diabetic relatives who were antibody-negative and had 0 or 1 HLA-DQ high-risk haplotypes (Log rank p = 0.01).

CONCLUSION/INTERPRETATION

These data provide evidence for a phenotype, which is associated with the absence of conventional islet autoantibodies at initial screening, while usually remaining seronegative, and the presence of 2 HLA-DQ high-risk haplotypes with progression to clinical Type I diabetes after a prolonged follow-up. Given the fact that in humans the highest risk-conferring locus associated and linked to the disease is the HLA cluster, and that HLA-DQ molecules play a key role in the development of autoimmune diabetes, our observations imply that as yet unidentified immunologic abnormalities could well exist in seronegative relatives at risk of developing clinical diabetes and carrying 2 HLA-DQ high-risk haplotypes.

TaqMan-based detection of Trichomonas vaginalis DNA from female genital specimens

A double-labeled fluorescent probe was designed and evaluated for detecting Trichomonas vaginalis DNA in a 5' nuclease (TaqMan) assay. The T. vaginalis-specific probe contains a 5'-fluorescein (5'-FAM) and a 3'-rhodamine (TAMRA) derivative. Female genital secretions were collected on Amplicor (Roche Molecular, Indianapolis, Ind.) swabs and by a transport system used for Chlamydia trachomatis and/or Neisseria gonorrhoeae DNA detection by PCR. Five hundred fifty-two female genital specimens, of which 248 (45%) were vaginal specimens and 304 (55%) were introital, were tested for both T. vaginalis DNA and viable microorganisms using the 5' nuclease assay and broth culture, respectively. Of these, 304 of 552 (55%) were also evaluated by direct microscopic examination for the characteristic motile organism. After resolving discrepancies, the comparisons produced an analytical sensitivity and specificity for the TaqMan-based PCR assay of 97.8 and 97.4%, respectively. As a result, DeltaRQ values (differences in fluorescence due to probe hybridization and resulting 5'-FAM cleavage from the specific PCR product) of > or =2.0 and < or =1.5 were established for T. vaginalis-positive and -negative cutoffs, respectively. DeltaRQ values between 1.5 and 2.0 were considered indeterminate. Overall findings revealed a high level of agreement between PCR and culture for detecting T. vaginalis. Potential benefits of the 5' nuclease assay include a greater sensitivity compared to direct microscopic examination and the ease of testing large numbers of clinical specimens in a significantly shorter turnaround time compared to culture.

Immune related genetic polymorphisms and schizophrenia among the Chinese

Genetic association studies were conducted among two independent cohorts of Chinese ethnicity. The samples consisted of cases and unrelated controls, ascertained from Guangzhou, China, and Singapore. The studies were prompted by our earlier report of an association between schizophrenia and HLA DQB1 alleles (HLA DQB1*0602 and HLA DQB1*0303) in the Singapore sample. Polymorphisms of HLA DQB1 and flanking markers on chromosome 6p21.3 were investigated in the first part of the study. A significant negative association with HLA DQB1*0402 was detected in the Guangzhou sample (Odds ratio, OR 0.26, 95% confidence intervals, CI 0.1, 0.6; p < 0.02, corrected for multiple comparisons). Additional analysis of the Guangzhou and Singapore samples revealed associations at three other anonymous markers flanking HLA DQB1. In the second part of the study, three polymorphisms at the Interleukin-1 gene cluster (IL-1, chromosome 2q13-q21) were investigated in both cohorts, since associations with schizophrenia have been reported in another sample. Persuasive evidence for an association at IL-1 was not detected in either sample. Our results suggest a susceptibility locus for schizophrenia in the HLA region among the Chinese, but further clarification is necessary.

Flow cytometric characterization of myogenic cell populations obtained via the preplate technique: potential for rapid isolation of muscle-derived stem cells

Myoblast transplantation has been investigated as a therapy for muscle-related diseases and as a gene delivery vehicle for therapeutic recombinant proteins. Clinical successes involving muscle cell transplantation have been limited, in part because of poor donor cell survival, and the heterogeneous nature of myogenic donor cells has largely been ignored. We have previously reported an isolation technique, preplating, that results in purified myogenic cells that are capable of significantly higher rates of donor cell survival leading to enhanced gene transfer to skeletal muscle. Characterization of these purified cells revealed that they display markers common to stem cells and are capable of multilineage differentiation. This study was performed to phenotypically characterize, by flow cytometry, muscle-derived cell populations obtained by the preplate technique for the purpose of eventually developing a method to quickly identify and isolate viable muscle cells best suited for transplantation. Muscle cell cultures were analyzed for expression of the surface proteins Sca-1, c-Kit, and CD34. We found that the preplate technique purifies distinct myogenic cell subpopulations expressing CD34 alone (Sca-1 negative) and Sca-1 alone (CD34 negative), but that this expression is subject to change with time in culture. Isolation and transplantation of phenotypically pure Sca-1-positive myogenic cells, obtained by magnetic cell sorting, demonstrates the ability to quickly select viable myogenic cells capable of regenerating skeletal muscle and restoring dystrophin expression within dystrophic host skeletal muscle. Flow cytometric described phenotypes will aid in the rapid isolation of specific donor cell populations for muscle cell transplants and muscle cell-mediated gene therapies, thereby enhancing their future success.

The mystique of hepatic tolerogenicity

The evolution of clinical transplantation has hinged on 2 seminal turning points. The first was the demonstration in 1953 by Billingham, Brent, and Medawar that chimerism-associated tolerance could be induced deliberately in neonatal mice by infusing adult donor hematolymphopoietic cells. This discovery escalated in a straight line over the next 15 years to successful bone marrow transplantation in humans. The second turning point was the demonstration that organ allografts could self-induce tolerance under an umbrella of immunosuppression, or in some species without immunosuppression. Unfortunately, it was incorrectly concluded by most immunologists and surgeons that bone marrow and organ engraftment involved different immune mechanisms. In a derivative error, it became widely believed that the tolerogenicity of the liver differed fundamentally not only from that of bone marrow but also from that of other whole organs. These errors became dogma and were not corrected until low level donor leukocyte chimerism was found in humans and animals bearing long surviving liver, kidney, heart, and other kinds of allografts. With successful bone marrow transplantation, the trace population consisted of recipient rather than donor leukocytes. Thus, the consequences of organ and bone marrow engraftment were mirror images. From these observations, it was proposed that the engraftment of all kinds of organs as well as bone marrow cells (BMC) involved host versus graft (HVG) and graft versus host (GVH) reactions with reciprocal induction of variable degrees of specific non-reactivity (tolerance). The maintenance of the tolerance was an active and ongoing process requiring the persistence of the transplanted fragment of the donor immune system. The immune responsiveness and unresponsiveness to both organ and bone marrow allografts are thought to be governed by the migration and localization of leukocytes. The clarifying principles of tranplantation immunology that have emerged from the chimerism studies are relevant to the adaptive immune response to microbial, tumor, allogeneic, and self antigens. These principles should be used to guide efforts to systematically induce tolerance to human tissues and organs, and perhaps ultimately to xenografts.

Analysis of TCR Vbeta repertoire and cytokine gene expression in patients with idiopathic dilated cardiomyopathy

Although the etiopathogenesis of idiopathic dilated cardiomyopathy (IDC) is still unclear, it is widely accepted that a complex interplay between viral infections and immune mechanisms is the basis of disease genesis. Previously, we showed that heart-infiltrating T cells of patients suffering from acute, fulminant Coxsackie virus B3+-IDC shared a preferential usage of three variable gene segments of the T cell receptor beta chain-(TCR-Vbeta) encoding families Vbeta3, 7 and 13.1. This indicated the possible presence of a superantigen-driven immune response. Here, we further investigated the IDC immunological scenario by analysing different phenotypes of heart-infiltrating cells: TCR repertoires, cytokine expression and presence of enterovirus-specific antigens. IDC patients who underwent heart transplantation at different times after the onset of heart failure were studied. A cardiac infiltrate of CD4+ and CD8+ T cells was present together with activated macrophages. Furthermore, the same Vbeta gene families, previously found to be skewed in hearts from fulminant cases of CVB3+-IDC, together with two additional Vbeta gene families, Vbeta1 and 5B, were increased. IL-1beta, IL-2, IL-6 and IFN-gamma were expressed in the myocardium while others, like IL-4 were not. In conclusion, an orchestrated complex of immune mechanisms seems to be the basis of IDC etiopathogenesis.

Restricted TCR V beta gene expression and enterovirus infection in type I diabetes: a pilot study

AIMS/HYPOTHESIS

High frequencies of T-cell receptor (TCR) V beta 7+ T cells were detected among the lymphocytes isolated from pancreatic islets of children at the onset of Type I (insulin-dependent) diabetes mellitus. We assessed whether a preferential expression of certain TCR V beta gene families could also be detected among the peripheral blood mononuclear cells from diabetic patients.

METHODS

T-cell receptor repertoires were evaluated by using a semi-quantitative RT-PCR-based technique and confirmed by FACS analysis in peripheral blood mononuclear cells from diabetic patients before, at and after onset of the disease. These patients were also tested for exposure to enteroviruses by RT-PCR and by measuring titres of enterovirus-specific antibodies of the IgA, IgG, and IgM classes.

RESULTS

T-cell receptor V beta 7 gene family values were higher in recently-diagnosed diabetic patients (10.5% +/- 3.7) than in age-matched non-diabetic control subjects (5.1% +/- 1.6) (p < 0.001). In a time-course analysis of people who developed diabetes during clinical monitoring (i.e., converters), T-cell receptor V beta 7 gene expression showed values consistently above 10% (p < 0.0005). Long-standing diabetic patients showed lower percentage of V beta 7 expression compared to values measured at disease onset. In the longitudinal study of the converters, multiple acute enterovirus infections were also detected. These infections appeared to be temporally related to increased percentage of V beta 7 gene transcripts.

CONCLUSION/INTERPRETATION

The deviation in the T-cell receptor V beta repertoire among circulating T cells from diabetic patients seems to re-emphasize the importance of enterovirus infections in accelerating the progression of Type I diabetes.

Prevention of beta cell dysfunction and apoptosis activation in human islets by adenoviral gene transfer of the insulin-like growth factor I

Interleukin-1beta is a potent pro-inflammatory cytokine that has been shown to inhibit islet beta cell function as well as to activate Fas-mediated apoptosis in a nitric oxide-dependent manner. Furthermore, this cytokine is effective in recruiting lymphocytes that mediate beta cell destruction in IDDM onset. The insulin-like growth factor I (IGF-I) has been shown to block IL-1beta actions in vitro. We hypothesized that gene transfer of the insulin-like growth factor I to intact human islets could prevent IL-1beta-induced beta cell dysfunction and sensitization to Fas-triggered apoptosis activation. Intact human islets were infected with adenoviral vectors encoding IGF-I as well as beta-galactosidase and enhanced green fluorescent protein as controls. Adenoviral gene transfer of human IGF-I prevented IL-1beta-mediated nitric oxide production from human islets in vitro as well as the suppression of beta cell function as determined by glucose-stimulated insulin production. Moreover, IGF-I gene transfer prevented IL-1beta-induced, Fas-mediated apoptosis. These results suggest that locally produced IGF-I from cultured islets may be beneficial in maintaining beta cell function and promoting islet survival before and following islet transplantation as a potential therapy for type I diabetes.

Protection of human islets from the effects of interleukin-1beta by adenoviral gene transfer of an Ikappa B repressor

Interleukin-1beta (IL-1beta) is a pro-inflammatory cytokine that inhibits beta cell function and promotes Fas-triggered apoptosis. IL-1beta is thought to act early in the initiation of the autoimmune destruction of pancreatic beta cells in type I diabetes. IL-1beta promotes beta cell impairment, in part, by activating NF-kappaB transcription factor-dependent signaling pathways. We have examined whether beta cells could be protected from the effects of IL-1beta by overexpressing an inhibitor of NF-kappaB activity, IkappaB, by adenoviral gene transfer to intact human islets in culture. Infection of islets with an adenoviral vector encoding a non-phosphorylatable, non-degradable variant of IkappaBalpha resulted in normal insulin responses to glucose in the presence of IL-1beta. Furthermore, nitric oxide production was prevented and, more importantly, Fas-triggered apoptosis was inhibited following IkappaBalpha gene transfer. These results suggest that blocking the NF-kappaB pathway might prevent cytokine-induced beta cell impairment as a means of facilitating islet transplantation.