Type 1 diabetes risk assessment: improvement by follow-up measurements in young islet autoantibody-positive relatives

AIMS/HYPOTHESIS

Combinations of autoantibody characteristics, including antibody number, titre, subclass and epitope have been shown to stratify type 1 diabetes risk in islet autoantibody-positive relatives. The aim of this study was to determine whether autoantibody characteristics change over time, the nature of such changes, and their implications for the development of diabetes.

METHODS

Five-hundred and thirteen follow-up samples from 141 islet autoantibody-positive first-degree relatives were tested for islet autoantibody titre, IgG subclass, and GAD and IA-2 antibody epitope. All samples were categorised according to four risk stratification models. Relatives had a median follow-up of 6.8 years and 48 developed diabetes during follow-up. Survival analysis was used to determine the probability of change in risk category and of progression to diabetes.

RESULTS

For each stratification model, the majority of relatives (71-81%) remained in the same risk category throughout follow-up. In the remainder, changes occurred both from lower to higher and from higher to lower risk categories. For all four models, relatives aged < 15 years were more likely to change risk category than those aged >15 years (0.001 < p < 0.03). Relatives whose autoantibody status changed from low- to high-risk categories had a higher risk of diabetes than relatives who remained in low-risk categories, and inclusion of autoantibody status during follow-up improved diabetes risk stratification in Cox proportional hazards models (p < 0.001).

CONCLUSIONS/INTERPRETATION

Changes in islet autoantibodies are relevant to pathogenesis, and are likely to signal alterations in the disease process. Detection of changes through follow-up measurement will improve diabetes risk stratification, particularly in young individuals.

Association of interferon-gamma and interleukin 10 genotypes and serum levels with partial clinical remission in type 1 diabetes

We studied whether serum interferon (IFN)-gamma or interleukin (IL)-10 levels and their corresponding functional polymorphic genotypes are associated with partial remission of type 1 diabetes (T1D). A multi-centre study was undertaken in patients with newly diagnosed T1D and matched controls. T1D patients were followed for 3 months and characterized for remission status. Partial clinical remission was defined as a daily insulin dose <or= 0.38 units/kg/24 h with an HbA1c <or= 7.5%. Thirty-three patients and 32 controls were phenotyped for serum concentrations of IFN-gamma and IL-10 and genotyped for functional polymorphisms of the IFN-gamma and IL-10 genes. Sixteen of 25 informative patients (63%) remitted. Serum IFN-gamma concentrations were significantly decreased in remitters but increased in non-remitters compared to controls, and did not change over time in any group. IFN-gamma genotypes corresponded with serum levels in controls and non-remitters, but not in remitters who displayed the lowest serum IFN-gamma levels despite more often carrying high-producing IFN-gamma genotypes. Neither the frequency of IL-10 genotypes nor serum IL-10 concentration differed between patients and controls. The combination of high-producing IFN-gamma genotype together with low serum IFN-gamma concentration at the time of diagnosis provided a strong positive predictive value for remission. Serum IFN-gamma concentrations predicted by genotype and observed serum levels were discordant in remitters, suggestive of regulation overruling genetic predisposition. Although high-producing genotypes were less frequent in remitters, they were predictive of remission in combination with low serum IFN-gamma levels. These data imply that remission is partially immune-mediated and involves regulation of IFN-gamma transcription.

Rapamycin induces a caspase-independent cell death in human monocytes

The immunosuppressive activity of rapamycin (RAPA) and its efficacy as an anti-rejection agent in organ transplantation have been ascribed principally to its anti-proliferative effects on T cells, while the activity on monocytes is partially unknown. In vitro, RAPA reduced monocyte survival by inducing a caspase-independent cell death. RAPA-induced monocyte cell death (RAPA-CD) was impeded by activation of granulocyte macrophage-colony stimulating factor family receptors or toll-like receptor 4, and by exposure to inflammatory cytokines. In vivo, in patients who received RAPA monotherapy as part of pre-conditioning for islet transplantation, RAPA affected survival of myeloid lineage cells. In the peripheral blood, CD33(+) and CD14(+) cells decreased, whereas lymphocytes appeared unaffected. In the bone marrow, myeloid precursors such as CD15(+) and CD15(+)/CD16(+) were selectively and significantly decreased, but no major cytotoxic effects were observed. The RAPA-CD suggests a dependence of monocytes on mammalian target of RAPA pathways for nutrient usage, and this feature implies that RAPA could be selectively useful as a treatment to reduce monocytes or myeloid cells in conditions where these cells negatively affect patient, suggesting a potential anti-inflammatory action of this drug.

No evidence of diabetes-specific CD38 (ADP ribosil cyclase/cyclic ADP-ribose hydrolase) autoantibodies by liquid-phase immunoprecipitation

AIMS/HYPOTHESIS

Autoantibodies to the ADP ribosyl cyclase/cyclic ADP-ribose hydrolase CD38 have been suggested to be markers of autoimmunity in Type 1 and Type 2 diabetes. The aim of this study was to develop a fluid phase assay for population screening.

METHODS

Human recombinant CD38 was cloned and expressed by in vitro transcription and translation for fluid phase radio-binding assay, as a fusion protein in COS7 cells for fluid phase immunoprecipitation, and as a fusion protein for western blot assays. Antibody binding to each recombinant protein was measured in sera from patients with Type 1 diabetes, Type 2 diabetes and control subjects.

RESULTS

Immunoprecipitation of radio-labelled in vitro transcribed and translated CD38 was low in all sera, including monoclonal anti-CD38 antibodies, with no difference between patients and control subjects. Monoclonal antibodies to CD38, but not patient or control sera immunoprecipitated recombinant CD38 fusion protein expressed in COS7 cells. Antibody binding to recombinant CD38 in solid-phase western blot assay was detected in sera from 2% of patients with Type 1 diabetes, 6% of patients with Type 2 diabetes, and 8% of control subjects.

CONCLUSIONS

This study failed to detect diabetes relevant binding of antibodies to recombinant CD38 using liquid-phase methods. Formal comparison of anti-CD38 antibody detection between laboratories is suggested.

In insulin-autoantibody-positive children from the general population, antibody affinity identifies those at high and low risk

AIMS/HYPOTHESIS

Insulin autoantibodies (IAA) precede and predict the onset of type 1 diabetes, but not all children with IAA develop the disease. In affected families, IAA affinity can identify IAA-positive children who are more likely to progress to diabetes. The purpose of this study was to determine whether affinity is a useful marker to stratify type 1 diabetes risk in IAA-positive children from the general population.

METHODS

IAA affinity was determined by competitive binding to 125I-insulin with increasing concentrations of cold insulin and with cold proinsulin in sera from 46 IAA-positive children identified in the Karlsburg Type 1 Diabetes Risk Study of a Normal Schoolchild Population in north-eastern Germany.

RESULTS

IAA affinity ranged between 5 x 10(6) and 1.2 x 10(11) l/mol. IAA affinity was higher in 24 children who developed multiple islet autoantibodies or diabetes (median 3.5 x 10(9) l/mol; interquartile range [IQR] 2.1x10(9) to 2.1 x 10(10) l/mol) than in 22 children who did not develop multiple islet autoantibodies or diabetes (median 1.3 x 10(8) l/mol; IQR 3.8 x 10(7) to 7.2 x 10(8) l/mol; p<0.0001). Using a threshold of > or = 10(9) l/mol, 22 of the 24 children who developed multiple islet autoantibodies or diabetes were correctly identified by high-affinity IAA and 18 of 22 who did not develop multiple islet autoantibodies or diabetes were correctly identified by low-affinity IAA. IAA affinity was significantly higher in samples with proinsulin reactive IAA (p<0.0001).

CONCLUSIONS/INTERPRETATION

IAA affinity measurement provides robust identification of IAA associated with high diabetes risk.

Islet isolation for allotransplantation: variables associated with successful islet yield and graft function

AIMS/HYPOTHESIS

Efficient islet isolation is an important prerequisite for successful clinical islet transplantation. Although progressively improved, islet yield and quality are, however, unpredictable and variable and require standardisation.

METHODS

Since 1989 we have processed 437 pancreases using the automated method. The donor characteristics, pancreas procurement, and digestion and purification procedures including a wide enzyme characterisation of these pancreases were analysed and correlated with islet yield and transplant outcome.

RESULTS

By univariate analysis, islet yield was significantly associated with donor age (r=0.16; p=0.0009), BMI (r=0.19; p=0.0004), good pancreas condition (p=0.0031) and weight (r=0.15; p=0.0056), total collagenase activity (r=0.22; p=0.0001), adjusted collagenase activity/mg (r=0.18; p=0.0002), collagenase activity/solution volume (r=0.18; p=0.0002) and neutral protease activity/solution volume (r=0.14; p=0.0029). A statistically significant contribution to the variability of islet yield in a multivariate analysis performed on donor variables was found for donor BMI (p=0.0008). In a multivariate analysis performed on pancreas variables a contribution was found for pancreas weight (p=0.0064), and for a multivariate analysis performed on digestion variables we found a contribution for digestion time (p=0.0048) and total collagenase activity (p=0.0001). Twenty-four patients with type 1 diabetes received single islet preparations from single donors. In these patients, multivariate analyses showed that the reduction in insulin requirement was significantly associated with morphological aspects of islets (p=0.0010) and that 1-month C-peptide values were associated with islet purity (p=0.0071).

CONCLUSIONS/INTERPRETATION

These data provide baseline donor, digestion and purification selection criteria for islet isolation using the automated method and indicate that the morphological aspect may be a clinically relevant measure of islets on which the decision for transplant can be based.

IA-2 antibody prevalence and risk assessment of early insulin requirement in subjects presenting with type 2 diabetes (UKPDS 71)

AIMS/HYPOTHESIS

Established autoimmune markers of type 1 diabetes, including islet cell autoantibodies (ICA) and autoantibodies to glutamic acid decarboxylase (GADA) have been used to screen people presenting with type 2 diabetes for latent autoimmune diabetes in adults. We have examined the prevalence of autoantibodies to protein tyrosine phosphatase isoforms IA-2 (IA-2A) and IA-2beta/phogrin (IA-2betaA) in a cohort of adult UKPDS patients thought to have type 2 diabetes, and investigated the possible role of these autoantibodies in predicting requirement for insulin therapy.

METHODS

IA-2A and IA-2betaA were measured by a validated radioimmunoassay with human recombinant autoantigens in 4,169 white Caucasian patients aged 25-65 years and newly diagnosed with type 2 diabetes. The clinical requirement for insulin therapy within 6 years was examined in 2,556 patients not randomised to insulin.

RESULTS

IA-2A and IA-2betaA were present in 2.2 and 1.4%, respectively, of these patients. IA-2A were more prevalent in younger patients (p for trend <0.00001), more often associated with the HLA-DR4 allele (26.3 vs 8.0%, p<0.0001), and their presence increased the likelihood of insulin therapy requirement within 6 years from diagnosis [relative risk (95%CI) 12.2 (9.8-15.3)]. The presence of IA-2A together with GADA increased the relative risk of requiring insulin therapy from 5.4 (4.1-7.1) for GADA alone to 8.3 (3.7-18.8) and the corresponding positive predictive value from 33 to 50%.

CONCLUSIONS/INTERPRETATION

In type 2 diabetes, the presence of IA-2A is infrequent, associated with the HLA-DR4 haplotype, and highly predictive of future need for insulin therapy. The measurement of IA-2betaA does not provide additional information.

Maternal immunity to insulin does not affect diabetes risk in progeny of non obese diabetic mice

It has been suggested that maternal environment, in particular maternal autoantibodies, modify the risk of developing autoimmune diabetes in offspring. The aim of this study was to determine whether modification of maternal environment and maternal diabetes risk through immunization affects autoimmune diabetes risk in the progeny. The risk of developing insulin antibodies and of developing diabetes was determined in 113 female progeny of non obese diabetic (NOD) dams that were immunized with insulin, control antigen or vehicle before or during pregnancy. Although NOD dams immunized with insulin were rendered diabetes resistant (40% diabetes by age 36 weeks versus 100% in control dams), diabetes development in their female offspring (72%, 26/36) was similar to that in female offspring of dams immunized with glucagon (82%, 22/27) or vehicle (76%, 19/25). Furthermore, no significant differences in diabetes development or insulin autoantibody titres were observed between female progeny of insulin autoantibody positive NOD dams (82% diabetes by age 36 weeks, 18/22), insulin autoantibody negative NOD dams (75%, 41/55), and NOD dams that had antibodies against exogneous insulin (71%, 22/31). The findings suggest that modification of the maternal risk for autoimmune diabetes via antigen-specific immunization is not transferred to progeny and that fetal exposure to insulin autoantibodies does not increase the risk for diabetes development.

Similar low frequency of anti-MOG IgG and IgM in MS patients and healthy subjects

The authors used a liquid-phase radiobinding assay to measure serum anti-myelin oligodendrocyte protein (MOG) immunoglobulin (Ig) G in 87 patients with multiple sclerosis (MS), in 12 patients with encephalomyelitis, and in 47 healthy subjects. Anti-MOG IgM was determined in samples obtained at onset from 40 of 87 patients with MS and in control subjects. The frequency of positive samples with low titers of anti-MOG IgG (< or =5.7%) and IgM (< or =8.3%) was similar in all the groups and subgroups. Binding competition experiments showed that these antibodies had low affinity. Anti-MOG antibodies are not disease specific.

Immune responses to glutamic acid decarboxylase and insulin in patients with gestational diabetes

Pregnancy is a natural state of immunoprotection and tolerance. We studied subjects with gestational diabetes (GDM) to evaluate the influence of pregnancy on the humoral immune response to the autoantigen GAD and to injected insulin. Antibodies against glutamic acid decarboxylase (GADA) subclasses and epitope reactivity were determined in 34 GADA-positive pregnant patients with GDM, in 20 GADA-positive relatives of people with TID and in 25 GADA-positive patients with newly diagnosed TID. Partum levels of insulin antibodies (IA), IgG1- and IgG4-IA were measured in 131 women with GDM treated with human insulin from the time of diabetes diagnosis (including 22 with GADA) and were compared to 19 patients with TID after 3 months of insulin treatment. GADA titre and subclasses were similar among all groups. GADA in GDM patients bound fewer epitopes than GADA in relatives of patients with TID (all epitopes being present in 23%versus 65%, P < 0.01). In particular, antibodies to the minor GADA epitopes GAD6596-249, GAD651-100 and GAD67 were less frequent in patients with GDM compared to relatives (P < 0.01). Antibodies to insulin (IA) were found in 17% of patients with GDM. They were more frequent in GDM patients with GADA compared to GADA-negative patients (41%versus 12%, P < 0.005). IgG1 was the dominant insulin antibody subclass response in both patients with GDM and TID but levels of IgG1-IA and IgG4-IA were significantly lower in patients with GDM compared to patients with TID (P < 0.004). Antibody responses in women with gestational diabetes appear to be dampened and restricted, but without change in subclass usage.

IDDM2/insulin VNTR modifies risk conferred by IDDM1/HLA for development of Type 1 diabetes and associated autoimmunity

AIM/HYPOTHESIS

Type 1 diabetes (T1D) is an autoimmune disease with multiple susceptibility genes. The aim of this study was to determine whether combining IDDM1/HLA and IDDM2/ insulin( INS) 5' variable number of tandem repeat locus (VNTR) genotypes improves T1D risk assessment.

METHODS

Patients with T1D (n=488), control subjects (n=846), and offspring of parents with T1D (n=1122) were IDDM1 and IDDM2 genotyped. Offspring were followed for islet autoantibodies and T1D from birth until the age of 2 to 12 years.

RESULTS

Compared to the I/I INS VNTR genotype, the I/III and III/III genotypes reduced T1D risk conferred by IDDM1/HLA in all HLA genotype categories of the case-control cohort by 1.6-fold to three-fold. The highest T1D risk was associated with INS VNTR class I/I plus HLA DR3/DR4-DQ8 (20.4% in patients, 0.6% in control subjects) or HLA DR4-DQ8/DR4-DQ8 (6.3% in patients, 0.2% in control subjects). In the offspring, HLA DR3/DR4-DQ8 and DR4-DQ8/DR4-DQ8 conferred increased risk for early development of islet autoantibodies (14.6% and 12.9% by age 2 years). Offspring with these high risk IDDM1 genotypes plus the INS VNTR class I/I genotype (n=71; 6.3%) had the highest risk of developing islet autoantibodies (21.8% by age 2 years vs 8.9% in offspring with high risk IDDM1 plus INS VNTR class I/III or III/III genotypes, p<0.05) and T1D (8.5% by age 6 years vs 4.3%). Offspring who developed autoantibodies to multiple antigens had increased frequencies of both high risk IDDM1 and IDDM2 genotypes (p<0.0001), whereas offspring who developed autoantibodies to GAD only had increased frequencies of high risk IDDM1 and protective IDDM2 genotypes, suggesting that IDDM2 influences the autoimmune target specificity.

CONCLUSION/INTERPRETATION

Combining IDDM1 and IDDM2 genotyping identifies a minority of children with an increased T1D risk.

Reduced IL-4 associated antibody responses to vaccine in early pre-diabetes

AIMS/HYPOTHESIS

The aim of this study was to determine whether beta-cell autoimmunity is associated with immune response bias to exogenous antigens.

METHODS

IgG subclass responses against tetanus toxoid and rubella were measured after vaccination in children with (n=36) and without (n=73) islet autoantibodies participating in the BABYDIAB prospective study of offspring of parents with Type I (insulin-dependent) diabetes mellitus. All children had been vaccinated against tetanus toxoid antigen before 6 months of age and at 18 months of age, and against live attenuated rubella virus at 18 months of age and again before 5 years of age. Tetanus toxoid specific IgG subclasses and cytokine responses were compared in a second cohort of subjects.

RESULTS

Responses to tetanus toxoid in islet-autoantibody-negative children were characterized by early IgG1 antibodies at 9 months of age followed by the appearance of IgG4 and lesser IgG2 antibodies at 2 years of age. Children who had developed islet autoimmunity before one year of age (n=15) did not have the shift to IgG4 and IgG2 anti-TT after booster vaccination (p<0.01), and had undetectable or IgG1 restricted responses. This defect was independent of HLA class II genotype, was restricted to children who had islet autoimmunity before 1 year of age, and was most evident in children who already had multiple islet autoantibodies by 9 months of age. IgG4 and IgG2 anti-TT correlated with IL-4 (p<0.005), but not IFNgamma responses. Antibody responses to the IFNgamma-inducing rubella vaccination were strongly IgG1 dominated and no differences were observed between islet autoantibody positive and negative children.

CONCLUSIONS/INTERPRETATION

These data are consistent with a reduced capacity to make IL-4 promoted antibody responses to exogenous antigen in early pre-diabetes.

Successful [correction of Succesful] transplantation of human islets in recipients bearing a kidney graft

AIMS/HYPOTHESIS

Islet transplantation is a minimally invasive approach to curing Type I (insulin-dependent) diabetes mellitus. Success has recently been reported in patients receiving solitary islet transplants but the outcome in patients receiving islets together with, or after, kidney transplants has been limited and unpredictable.

METHODS

Here we report successful islet transplantation in a cohort of 15 patients with Type I diabetes who were followed for at least 1 year after islet transplantation, after having already received kidney allografts because of end-stage nephropathy.

RESULTS

C-peptide after transplantation was higher than 0.17 nmol/l in all 15 recipients, reflecting the absence of primary non-function. Insulin requirement was reduced by over 50 % in all but one patient, and insulin independence was achieved in 10 (66 %) recipients, five of whom now have stable, prolonged insulin independence, well controlled fasting glycaemia, a substantial first-phase and normal second-phase response to glucose, normal insulin sensitivity (HOMA analyses) and HbA1 c of under 6.2 % (33, 26, 18, 13 and 12 months after transplantation respectively). Of importance for patient management, an assessment of fasting blood glucose and proinsulin values following overnight withdrawal of insulin administration one month after transplantation was a potent predictor of insulin independence, and could be used to decide patients who should have further islet preparations.

CONCLUSION/INTERPRETATION

These findings support the use of islet transplantation as a cure for Type I diabetes in patients with severe complications.

Autoantibody response to islet transplantation in type 1 diabetes

Islet allotransplantation into patients with autoimmune type 1 diabetes represents a reexposure to autoantigen. Here, measurement of antibodies to GAD and IA-2 autoantigens before and after islet transplantation in 36 patients (33 receiving islet plus kidney grafts with cyclosporin and steroid-based immunosuppression, and 3 receiving solitary islet transplants with mycophenolate but cyclosporin-free immunosuppression) demonstrated marked rises in GAD antibodies within 7 days posttransplantation in 5 patients (3 receiving islet after kidney transplants, and 2 receiving solitary islet transplants) and within 30 days in the third patient receiving solitary islet transplantation. GAD antibodies were of the IgG1 subclass, against major autoantigenic epitopes, and in cases of islet after kidney transplants, the responses were short-lived and not accompanied by HLA antibodies. Two of these patients had subsequent marked rises of IA-2 antibodies, and an additional patient had a marked rise in IgM-GAD antibodies 3 years after transplantation. Insulin independence was not achieved in patients with autoantibody elevations and was significantly less frequent in these patients. These data are consistent with a reactivation of autoimmunity that may be dependent on immunosuppression therapy and is associated with impaired graft function.

International Workshop on Lessons From Animal Models for Human Type 1 Diabetes: identification of insulin but not glutamic acid decarboxylase or IA-2 as specific autoantigens of humoral autoimmunity in nonobese diabetic mice

Several self-antigens have been reported as targets of the autoimmune response in nonobese diabetic (NOD) mice. The aim of this workshop was to identify autoantibody assays that could provide useful markers of autoimmunity in this animal model for type 1 diabetes. More than 400 serum samples from NOD (4, 8, and 12 weeks of age and at diabetes onset), BALB/c, and B6 mice were collected from six separate animal facilities, coded, and distributed to five laboratories for autoantibody measurement. Insulin autoantibodies (IAA) were measured by radiobinding assay (RBA) by four laboratories and by enzyme-linked immunosorbent assay (ELISA) in one laboratory. Using the 99th percentile of BALB/c and B6 control mice as the threshold definition of positivity, IAA by RBA were detected in NOD mice at frequencies ranging from 10 to 30% at age 4 weeks, from 26 to 56% at 8 weeks, from 42 to 56% at 12 weeks, and from 15 to 75% at diabetes onset. With ELISA, IAA signals differed significantly between control mouse strains and increased with age in both control and NOD mice, with frequencies in NOD animals being 0% at 4 weeks, 14% at 8 weeks, 19% at 12 weeks, and 42% at diabetes onset. For IAA, the ELISA results were relatively discordant with those of RBA. GAD autoantibody (GADA) and IA-2 autoantibody (IA-2A) signals obtained by RBA were low (maximum 2.5% of total) but were increased in NOD mice compared with control mice at diabetes onset (GADA 29-50%; IA-2A 36-47%). ELISA also detected GADA (42%) and IA-2A (50%) at diabetes onset, with results concordant with those of RBA. Remarkably, GADA and IA-2A frequencies varied significantly with respect to the source colony of NOD mice. Furthermore, whereas neither GADA nor IA-2A correlated with IAA, there was strong concordance between GADA and IA-2A in individual mice. Sera with increased binding to GAD and IA-2 also had increased binding to the unrelated antigen myelin oligodendrocyte glycoprotein, and binding to GAD could not be inhibited with excess unlabeled antigen, suggesting nonspecific interactions. In sum, this workshop demonstrated that IAA measured by sensitive RBA are a marker of autoimmunity in NOD mice and draw into question the true nature of GADA and IA-2A in this animal model.