Reduced display of conformational epitopes in the N-terminal truncated GAD65 isoform: relevance for people with stiff person syndrome or DQ8/8-positive Type 1 diabetes mellitus.

AIMS: To investigate whether the N-terminal truncated glutamic acid decarboxylase 65 (GAD65) isoform is as well recognized by people with stiff person syndrome as it is by people with Type 1 diabetes, and whether conformational GAD65 antibody epitopes are displayed properly by the isoform. METHODS: GAD65 antibody-positive healthy individuals (n=13), people with stiff-person syndrome (n=15) and children with new-onset Type 1 diabetes (n=654) were analysed to determine binding to full-length GAD65 and the N-terminal truncated GAD65 isoform in each of these settings. GAD65 autoantibody epitope specificity was correlated with binding ratios of full-length GAD65/N-terminal truncated GAD65. RESULTS: The N-terminal truncated GAD65 isoform was significantly less recognized in GAD65Ab-positive people with stiff-person syndrome (P=0.002) and in healthy individuals (P=0.0001) than in people with Type 1 diabetes. Moreover, at least two specific conformational GAD65Ab epitopes were not, or were only partially, presented by the N-terminal truncated GAD65 isoform compared to full-length GAD65. Finally, an N-terminal conformational GAD65Ab epitope was significantly less recognized in DQ8/8 positive individuals with Type 1 diabetes (P=0.02). CONCLUSIONS: In people with stiff person syndrome preferred binding to the full-length GAD65 isoform over the N-terminal truncated molecule was observed. This binding characteristic is probably attributable to reduced presentation of two conformational epitopes by the N-terminal truncated molecule. These findings support the notion of disease-specific GAD65Ab epitope specificities and emphasize the need to evaluate the applicability of novel assays for different medical conditions.

Altered regulatory T cell phenotype in latent autoimmune diabetes of the adults (LADA).

Latent autoimmune diabetes of the adults (LADA) accounts for up to 12% of all patients with diabetes. Initially the disease resembles type 2 diabetes (T2D); however, the typical presence of ß cell autoantibodies indicates an autoimmune basis of LADA. While dysfunctional regulatory T cells (Tregs ) have been implicated in autoimmune diabetes, these cells have been scarcely studied in LADA. The aim of this study was to investigate the frequency and phenotype of circulating Tregs in LADA patients early during disease progression. Flow cytometric analysis was performed on whole blood and peripheral mononuclear cells (PBMC) from patients diagnosed with LADA prior to insulin deficiency (n = 39) and from healthy volunteers (n = 20). Overall, we found the frequency and activation status of peripheral putative Tregs to be altered in LADA patients compared to healthy controls. While total T cells and CD4(+) T cells expressing high levels of CD25 (CD4(+) CD25(hi) ) were unchanged, the frequency and total numbers of CD4(+) T cells expressing an intermediate level of CD25 (CD4(+) CD25(int) ) were decreased in LADA patients. Interestingly, the expression of the Treg -specific marker forkhead box protein 3 (FoxP3), as well as the activation and memory makers CD69, cytotoxic T lymphocyte associated antigen 4 (CTLA-4), CCR4 and CD45RO were increased in CD4(+) CD25(+) T cells of the patients. Our data depict phenotypical changes in T cells of LADA patients that may reflect a derangement in peripheral immune regulation contributing to the slow process leading to insulin-dependent diabetes in these patients.

Pancreas volume and fat fraction in children with Type 1 diabetes.

AIMS: People with Type 1 diabetes have smaller pancreases than healthy individuals. Several diseases causing pancreatic atrophy are associated with pancreatic steatosis, but pancreatic fat in Type 1 diabetes has not been measured. This cross-sectional study aimed to compare pancreas size and fat fraction in children with Type 1 diabetes and controls. METHODS: The volume and fat fraction of the pancreases of 22 children with Type 1 diabetes and 29 controls were determined using magnetic resonance imaging. RESULTS: Pancreas volume was 27% smaller in children with diabetes (median 34.9 cm(3) ) than in controls (47.8 cm(3) ; P < 0.001). Pancreas volume correlated positively with age in controls (P = 0.033), but not in children with diabetes (P = 0.649). Pancreas volume did not correlate with diabetes duration, but it did correlate positively with units of insulin/kg body weight/day (P = 0.048). A linear model of pancreas volume as influenced by age, body surface area and insulin units/kg body weight/day found that insulin dosage correlated with pancreas volume after controlling for both age and body surface area (P = 0.009). Pancreatic fat fraction was not significantly different between the two groups (1.34% vs. 1.57%; P = 0.891). CONCLUSIONS: Our findings do not indicate that pancreatic atrophy in Type 1 diabetes is associated with an increased pancreatic fat fraction, unlike some other diseases featuring reduced pancreatic volume. We speculate that our results may support the hypotheses that much of pancreatic atrophy in Type 1 diabetes occurs before the clinical onset of the disease and that exogenous insulin administration decelerates pancreatic atrophy after diabetes onset.

Non-HLA type 1 diabetes genes modulate disease risk together with HLA-DQ and islet autoantibodies.

The possible interrelations between human leukocyte antigen (HLA)-DQ, non-HLA single-nucleotide polymorphisms (SNPs) and islet autoantibodies were investigated at clinical onset in 1-34-year-old type 1 diabetes (T1D) patients (n=305) and controls (n=203). Among the non-HLA SNPs reported by the Type 1 Diabetes Genetics Consortium, 24% were supported in this Swedish replication set including that the increased risk of minor PTPN22 allele and high-risk HLA was modified by GAD65 autoantibodies. The association between T1D and the minor AA+AC genotype in ERBB3 gene was stronger among IA-2 autoantibody-positive patients (comparison P=0.047). The association between T1D and the common insulin (AA) genotype was stronger among insulin autoantibody (IAA)-positive patients (comparison P=0.008). In contrast, the association between T1D and unidentified 26471 gene was stronger among IAA-negative (comparison P=0.049) and IA-2 autoantibody-negative (comparison P=0.052) patients. Finally, the association between IL2RA and T1D was stronger among IAA-positive than among IAA-negative patients (comparison P=0.028). These results suggest that the increased risk of T1D by non-HLA genes is often modified by both islet autoantibodies and HLA-DQ. The interactions between non-HLA genes, islet autoantibodies and HLA-DQ should be taken into account in T1D prediction studies as well as in prevention trials aimed at inducing immunological tolerance to islet autoantigens.

Zinc transporter 8 (ZnT8) autoantibody epitope specificity and affinity examined with recombinant ZnT8 variant proteins in specific ZnT8R and ZnT8W autoantibody-positive type 1 diabetes patients.

Variant-specific zinc transporter 8 autoantibodies (ZnT8A) against either arginine (R) or tryptophan (W) at amino acid (aa) position 325 of the zinc transporter 8 (ZnT8) has been identified in type 1 diabetes (T1D) patients. Reciprocal cross-over tests revealed differences in half-maximal binding to indicate variable affinity of patient ZnT8 autoantibodies. Insufficient recombinant ZnT8 variant proteins have precluded detailed analyses of ZnT8 autoantibody affinity. The aims in the present study were to (i) generate recombinant ZnT8R- and ZnT8W-aa275-369 proteins; (ii) test the ZnT8R- and ZnT8W-aa275-369 proteins in reciprocal competitive radiobinding assays (RBA) against ZnT8R- and ZnT8W-aa268-369 labelled with (35) S-methionine; and (iii) determine the specificity and affinity of sera specific for either ZnT8 arginine (R) or ZnT8 tryptophan (W) autoantibodies in newly diagnosed T1D patients. The results demonstrate, first, that it was possible to produce recombinant human MBP-ZnT8-aa275-369 protein purified to homogeneity for RBA reciprocal competition experiments. Secondly, high-titre ZnT8WA sera diluted to half maximal binding showed significant specificity for respective variants of either ZnT8R or ZnT8W. Thirdly, ZnT8WA-positive sera showed high affinity for ZnT8W compared to ZnT8RA for ZnT8R. These data demonstrate that T1D patients may have single amino acid-specific autoantibodies directed against either ZnT8R or ZnT8W and that the autoantibody affinity to the respective variant may be different. Further studies are needed to assess the mechanisms by which variant-specific ZnT8A of variable affinity develop and their possible role in the pathogenic process leading to the clinical onset of T1D.

Serological evaluation of possible exposure to Ljungan virus and related parechovirus in autoimmune (type 1) diabetes in children.

Exposure to Ljungan virus (LV) is implicated in the risk of autoimmune (type 1) diabetes but possible contribution by other parechoviruses is not ruled out. The aim was to compare children diagnosed with type 1 diabetes in 2005-2011 (n = 69) with healthy controls (n = 294), all from the Jämtland County in Sweden, using an exploratory suspension multiplex immunoassay for IgM and IgG against 26 peptides of LV, human parechoviruses (HPeV), Aichi virus and poliovirus in relation to a radiobinding assay (RBA) for antibodies against LV and InfluenzaA/H1N1pdm09. Islet autoantibodies and HLA-DQ genotypes were also determined. 1) All five LV-peptide antibodies correlated to each other (P < 0.001) in the suspension multiplex IgM- and IgG-antibody assay; 2) The LV-VP1_31-60-IgG correlated with insulin autoantibodies alone (P = 0.007) and in combination with HLA-DQ8 overall (P = 0.022) as well as with HLA-DQ 8/8 and 8/X subjects (P = 0.013); 3) RBA detected LV antibodies correlated with young age at diagnosis (P < 0.001) and with insulin autoantibodies (P < 0.001) especially in young HLA-DQ8 subjects (P = 0.004); 4) LV-peptide-VP1_31-60-IgG correlated to RBA LV antibodies (P = 0.009); 5) HPeV3-peptide-IgM and -IgG showed inter-peptide correlations (P < 0.001) but only HPeV3-VP1_1-30-IgG (P < 0.001) and VP1_95-124-IgG (P = 0.009) were related to RBA LV antibodies without relation to insulin autoantibody positivity (P = 0.072 and P = 0.486, respectively). Both exploratory suspension multiplex IgG to LV-peptide VP1_31-60 and RBA detected LV antibodies correlated with insulin autoantibodies and HLA-DQ8 suggesting possible role in type 1 diabetes. It remains to be determined if cross-reactivity or concomitant exposure to LV and HPeV3 contributes to the seroprevalence.

Doubly Reactive INS-IGF2 Autoantibodies in Children with Newly Diagnosed Autoimmune (type 1) Diabetes.

The splice variant INS-IGF2 entails the preproinsulin signal peptide, the insulin B-chain, eight amino acids of the C-peptide and 138 unique amino acids from an ORF in the IGF2 gene. The aim of this study was to determine whether levels of specific INS-IGF2 autoantibodies (INS-IGF2A) were related to age at diagnosis, islet autoantibodies, HLA-DQ or both, in patients and controls with newly diagnosed type 1 diabetes. Patients (n = 676), 0-18 years of age, diagnosed with type 1 diabetes in 1996-2005 and controls (n = 363) were analysed for specific INS-IGF2A after displacement with both cold insulin and INS-IGF2 to correct for non-specific binding and identify double reactive sera. GADA, IA-2A, IAA, ICA, ZnT8RA, ZnT8WA, ZnT8QA and HLA-DQ genotypes were also determined. The median level of specific INS-IGF2A was higher in patients than in controls (P < 0.001). Irrespective of age at diagnosis, 19% (126/676) of the patients had INS-IGF2A when the cut-off was the 95th percentile of the controls (P < 0.001). The risk of INS-IGF2A was increased among HLA-DQ2/8 (OR = 1.509; 95th CI 1.011, 2.252; P = 0.045) but not in 2/2, 2/X, 8/8, 8/X or X/X (X is neither 2 nor 8) patients. The association with HLA-DQ2/8 suggests that this autoantigen may be presented on HLA-DQ trans-heterodimers, rather than cis-heterodimers. Autoantibodies reactive with both insulin and INS-IGF2A at diagnosis support the notion that INS-IGF2 autoimmunity contributes to type 1 diabetes.

Variability in the CIITA gene interacts with HLA in multiple sclerosis.

The human leukocyte antigen (HLA) is the main genetic determinant of multiple sclerosis (MS) risk. Within the HLA, the class II HLA-DRB1*15:01 allele exerts a disease-promoting effect, whereas the class I HLA-A*02 allele is protective. The CIITA gene is crucial for expression of class II HLA molecules and has previously been found to associate with several autoimmune diseases, including MS and type 1 diabetes. We here performed association analyses with CIITA in 2000 MS cases and up to 6900 controls as well as interaction analysis with HLA. We find that the previously investigated single-nucleotide polymorphism rs4774 is associated with MS risk in cases carrying the HLA-DRB1*15 allele (P=0.01, odds ratio (OR): 1.21, 95% confidence interval (CI): 1.04-1.40) or the HLA-A*02 allele (P=0.01, OR: 1.33, 95% CI: 1.07-1.64) and that these associations are independent of the adjacent confirmed MS susceptibility gene CLEC16A. We also confirm interaction between rs4774 and HLA-DRB1*15:01 such that individuals carrying the risk allele for rs4774 and HLA-DRB1*15:01 have a higher than expected risk for MS. In conclusion, our findings support previous data that variability in the CIITA gene affects MS risk, but also that the effect is modulated by MS-associated HLA haplotypes. These findings further underscore the biological importance of HLA for MS risk.

Prevalence of obesity was related to HLA-DQ in 2-4-year-old children at genetic risk for type 1 diabetes.

OBJECTIVES: Body size is postulated to modulate type 1 diabetes as either a trigger of islet autoimmunity or an accelerator to clinical onset after seroconversion. As overweight and obesity continue to rise among children, the aim of this study was to determine whether human leukocyte antigen DQ (HLA-DQ) genotypes may be related to body size among children genetically at risk for type 1 diabetes. METHODS: Repeated measures of weight and height were collected from 5969 children 2-4 years of age enrolled in The Environmental Determinants of Diabetes in the Young prospective study. Overweight and obesity was determined by the International Obesity Task Force cutoff values that correspond to body mass index (BMI) of 25 and 30 kg m(-)(2) at age 18. RESULTS: The average BMI was comparable across specific HLA genotypes at every age point. The proportion of overweight was not different by HL A, but percent obesity varied by age with a decreasing trend among DQ2/8 carriers (P for trend=0.0315). A multivariable regression model suggested DQ2/2 was associated with higher obesity risk at age 4 (odds ratio, 2.41; 95% confidence interval, 1.21-4.80) after adjusting for the development of islet autoantibody and/or type 1 diabetes. CONCLUSIONS: The HLA-DQ2/2 genotype may predispose to obesity among 2-4-year-old children with genetic risk for type 1 diabetes.

Antibodies to influenza virus A/H1N1 hemagglutinin in Type 1 diabetes children diagnosed before, during and after the SWEDISH A(H1N1)pdm09 vaccination campaign 2009-2010.

We determined A/H1N1-hemagglutinin (HA) antibodies in relation to HLA-DQ genotypes and islet autoantibodies at clinical diagnosis in 1141 incident 0.7-to 18-year-old type 1 diabetes patients diagnosed April 2009-December 2010. Antibodies to (35) S-methionine-labelled A/H1N1 hemagglutinin were determined in a radiobinding assay in patients diagnosed before (n = 325), during (n = 355) and after (n = 461) the October 2009-March 2010 Swedish A(H1N1)pdm09 vaccination campaign, along with HLA-DQ genotypes and autoantibodies against GAD, insulin, IA-2 and ZnT8 transporter. Before vaccination, 0.6% patients had A/H1N1-HA antibodies compared with 40% during and 27% after vaccination (P < 0.0001). In children <3 years of age, A/H1N1-HA antibodies were found only during vaccination. The frequency of A/H1N1-HA antibodies during vaccination decreased after vaccination among the 3 < 6 (P = 0.006) and 13 < 18 (P = 0.001), but not among the 6 < 13-year-olds. HLA-DQ2/8 positive children <3 years decreased from 54% (15/28) before and 68% (19/28) during, to 30% (9/30) after vaccination (P = 0.014). Regardless of age, DQ2/2; 2/X (n = 177) patients had lower frequency (P = 0.020) and levels (P = 0.042) of A/H1N1-HA antibodies compared with non-DQ2/2; 2/X (n = 964) patients. GADA frequency was 50% before, 60% during and 51% after vaccination (P = 0.009). ZnT8QA frequency increased from 30% before to 34% during and 41% after vaccination (P = 0.002). Our findings suggest that young (<3 years) along with DQ2/2; 2/X patients were low responders to Pandemrix(®) . As the proportion of DQ2/8 patients <3 years of age decreased after vaccination and the frequencies of GADA and ZnT8QA were enhanced, it cannot be excluded that the vaccine affected clinical onset of type 1 diabetes.

Next-generation sequencing for viruses in children with rapid-onset type 1 diabetes.

AIMS/HYPOTHESIS: Viruses are candidate causative agents in the pathogenesis of autoimmune (type 1) diabetes. We hypothesised that children with a rapid onset of type 1 diabetes may have been exposed to such agents shortly before the initiation of islet autoimmunity, possibly at high dose, and thus study of these children could help identify viruses involved in the development of autoimmune diabetes. METHODS: We used next-generation sequencing to search for viruses in plasma samples and examined the history of infection and fever in children enrolled in The Environmental Determinants of Diabetes in the Young (TEDDY) study who progressed to type 1 diabetes within 6 months from the appearance of islet autoimmunity, and in matched islet-autoantibody-negative controls. RESULTS: Viruses were not detected more frequently in plasma from rapid-onset patients than in controls during the period surrounding seroconversion. In addition, infection histories were found to be similar between children with rapid-onset diabetes and control children, although episodes of fever were reported less frequently in children with rapid-onset diabetes. CONCLUSIONS/INTERPRETATION: These findings do not support the presence of viraemia around the time of seroconversion in young children with rapid-onset type 1 diabetes.

Thyroid autoimmunity in relation to islet autoantibodies and HLA-DQ genotype in newly diagnosed type 1 diabetes in children and adolescents.

AIMS/HYPOTHESIS: The aim of this work was to investigate, in children newly diagnosed with type 1 diabetes: (1) the prevalence of autoantibodies against thyroid peroxidase (TPOAb) and thyroglobulin (TGAb); and (2) the association between TPOAb, TGAb or both, with either islet autoantibodies or HLA-DQ genes. METHODS: Blood samples from 2,433 children newly diagnosed with type 1 diabetes were analysed for TPOAb and TGAb in addition to autoantibodies against arginine zinc transporter 8 (ZnT8RA), tryptophan zinc transporter 8 (ZnT8WA), glutamine zinc transporter 8 (ZnT8QA), glutamic acid decarboxylase (GADA), insulin (IAA), insulinoma-associated protein-2 (IA-2A), HLA-DQA-B1 genotypes, thyroid-stimulating hormone (TSH) and free thyroxine (T4). RESULTS: At type 1 diabetes diagnosis, 12% of the children had thyroid autoantibodies (60% were girls; p < 0.0001). GADA was positively associated with TPOAb (p < 0.001) and with TGAb (p < 0.001). In addition, ZnT8A was associated with both TPOAb (p = 0.039) and TGAb (p = 0.015). DQB1*05:01 in any genotype was negatively associated with TPOAb (OR 0.55, 95% CI 0.37, 0.83, p value corrected for multiple comparisons (p c) = 0.012) and possibly with TGAb (OR 0.55, 95% CI 0.35, 0.87, p c = 0.07). Thyroid autoimmunity in children newly diagnosed with type 1 diabetes was rarely (0.45%) associated with onset of clinical thyroid disease based on TSH and free T4. CONCLUSIONS/INTERPRETATION: GADA and ZnT8A increased the risk for thyroid autoimmunity at the time of clinical diagnosis of type 1 diabetes, while HLA-DQB1*05:01 reduced the risk. However, the associations between thyroid autoimmunity and HLA-DQ genotype were weak and did not fully explain the co-occurrence of islet and thyroid autoimmunity.

Antigenicity and epitope specificity of ZnT8 autoantibodies in type 1 diabetes.

The single nucleotide polymorphism (SNP) rs13266634 encodes either an Arginine (R) or a Tryptophan (W) (R325W) at the amino acid position 325 in the Zinc Transporter 8 (ZnT8) protein. Autoantibodies (Ab) that recognize ZnT8R, ZnT8W or both at the polymorphic site are common in newly diagnosed type 1 diabetes (T1D) patients. The epitope specificity and affinity of ZnT8Ab are poorly understood, but may be of importance for the prediction and clinical classification of T1D. Therefore, the aims were to 1) determine the immunogenicity of short (318-331) ZnT8 peptides in mice and 2) test the affinity of short and long (268-369) ZnT8 proteins in T1D patients positive for either ZnT8RAb or ZnT8wAb. Sera from BALB/cByJ mice immunized with short R, W or Q (Glutamine) ZnT8 peptides were tested for ZnT8-peptide antibodies in ELISA and radiobinding assay (RBA). Using reciprocal permutation experiment, short synthetic ZnT8R and ZnT8W (318-331) and long in vitro transcription translation ZnT8R and ZnT8W (268-369) proteins were tested in competitive RBA with R- and W-monospecific T1D sera samples. All mouse sera developed non-epitope-specific peptide antibodies in ELISA and only 6/12 mice had ZnT8-RWQ antibodies in RBA. Both long ZnT8R and ZnT8W (268-369), but not any short, proteins displaced labelled ZnT8 (268-369) proteins in binding to T1D ZnT8Ab-specific sera. The reciprocal cross-over tests showed that half-maximal displacement varied 2- to 11-fold indicating variable affinity of patient ZnT8Ab, signifying crucial autoantibody epitope spreading. The present approach should make it possible to dissect the importance of the R325W ZnT8 autoantigen epitope in the T1D pathogenesis.

Residual beta cell function at diagnosis of type 1 diabetes in children and adolescents varies with gender and season.

BACKGROUND: There are seasonal variations and gender differences in incidence of type 1 diabetes (T1D), metabolic control and responses to immune interventions at onset of the disease. We hypothesized that there are seasonal and gender differences in residual insulin secretion already at diagnosis of T1D. METHODS: In 2005, a national study, the Better Diabetes Diagnosis, was started to classify all newly diagnosed children and adolescents with diabetes. About 95% (3824/4017) of the patients were classified as T1D, and our analyses are based on the patients with T1D. RESULTS: C-peptide was lower in younger children, 0-10 years of age (0.23 ± 0.20 nmol/L) than in older children, 11-18 years of age (0.34 ± 0.28 nmol/L) (p < 0.000 ). There was a seasonal variation in non-fasting serum C-peptide, significantly correlated to the seasonal variation of diagnosis (p < 0.01). Most children were diagnosed in January, February and March as well as in October when C-peptide was highest, whereas fewer patients were diagnosed in April and May when serum C-peptide was significantly lower (p < 0.01). The seasonal variation of C-peptide was more pronounced in boys than in girls (p < 0.000 and p < 0.01, respectively). Girls had higher C-peptide than boys (p < 0.05), especially in early puberty. CONCLUSIONS: Both seasonal and gender differences in residual beta cell function exist already at diagnosis of T1D. These observations have consequences for treatment and for randomizing patients in immune intervention clinical trials.

The environment and the origins of islet autoimmunity and Type 1 diabetes.

Type 1 diabetes involves the specific destruction of the pancreatic islet ß-cells, eventually resulting in a complete dependency of exogenous insulin. The clinical onset of diabetes is preceded by the appearance of autoantibodies against ß-cell antigens. The human leukocyte antigen (HLA) region is the single most important genetic determinant of Type 1 diabetes susceptibility, yet variability in the HLA region has been estimated to explain only approximately 60% of the genetic influence of the disease. Over 50 identified non-HLA genetic polymorphisms support the notion that genetics alone cannot explain Type 1 diabetes. Several lines of evidence indicate that environmental triggers may be integral in inducing the onset of islet autoimmunity in genetically susceptible individuals. The association between environmental factors and the clinical onset is complicated by observation that the rate of progression to clinical onset may be affected by environmental determinants. Hence, the environment may be aetiological as well as pathogenic. Putative inductive mechanisms include viral, microbial, diet-related, anthropometric and psychosocial factors. Ongoing observational cohort studies such as The Environmental Determinants of Diabetes in the Young (TEDDY) study aim to ascertain environmental determinants that may trigger islet autoimmunity and either speed up or slow down the progression to clinical onset in subjects with persistent islet autoimmunity.

Triple specificity of ZnT8 autoantibodies in relation to HLA and other islet autoantibodies in childhood and adolescent type 1 diabetes.

OBJECTIVE: To establish the diagnostic sensitivity of and the relationships between autoantibodies to all three Zinc transporter 8 (Zinc transporter 8 autoantibody to either one, two, or all three amino acid variants at position 325, ZnT8A) variants to human leukocyte antigen (HLA)-DQ and to autoantibodies to glutamic acid decarboxylase (GADA), insulinoma-associated protein 2 (IA-2A), and insulin (IAA). METHODS: We analyzed 3165 patients with type 1 diabetes (T1D) in the Better Diabetes Diagnosis study for HLA-DQ genotypes and all six autoantibodies (ZnT8RA, arginine 325 Zinc transporter 8 autoantibody; ZnT8WA, tryptophan 325 Zinc transporter 8 autoantibody; ZnT8QA, glutamine 325 Zinc transporter 8 autoantibody; GADA, IA-2A, and IAA). RESULTS: ZnT8A was found in 65% of the patients and as many as 108 of 3165 (3.4%) had 1-3 ZnT8A alone. None had ZnT8QA alone. Together with GADA (56%), IA-2A (73%), and IAA (33%), 93% of the T1D patients were autoantibody positive. All three ZnT8A were less frequent in children below 2 yr of age (p < 0.0001). All three ZnT8A were associated with DQA1-B1*X-0604 (DQ6.4) and DQA1-B1*03-0302 (DQ8). ZnT8WA and ZnT8QA were negatively associated with DQA1-B1*05-02 (DQ2). CONCLUSIONS: Analysis of ZnT8A increased the diagnostic sensitivity of islet autoantibodies for T1D as only 7% remained islet autoantibody negative. The association between DQ6.4 and all three ZnT8A may be related to ZnT8 antigen presentation by the DQ6.4 heterodimer.

Genetic dissection of autoimmune type I diabetes in the BB rat.

The BB rat is among the best models of insulin-dependent diabetes mellitus--with onset and pathogenesis closely resembling the human disease. One unusual feature is a severe T-cell lymphopenia, which appears to be inherited as a recessive trait controlled by a single gene, Lyp. Based on genetic analysis of several crosses, we show that development of diabetes involves at least three genes: Lyp, which is tightly linked to the neuropeptide Y (Npy) gene on chromosome 4, a gene linked to the major histocompatibility complex (MHC) on chromosome 20, and a third unmapped gene for which the Fischer rat strain carries an allele conferring resistance.

A genetic linkage map of the laboratory rat, Rattus norvegicus.

We report the construction of the first complete genetic linkage map of the laboratory rat. By testing 1171 simple sequence length polymorphisms (SSLPs), we have identified 432 markers that show polymorphisms between the SHR and BN rat strains and mapped them in a single (SHR x BN) F2 intercross. The loci define 21 large linkage groups corresponding to the 21 rat chromosomes, together with a pair of nearby markers on chromosome 9 that are not linked to the rest of the map. Because 99.5% of the markers fall into one of the 21 large linkage groups, the maps appear to cover the vast majority of the rat genome. The availability of the map should facilitate whole genome scans for genes underlying qualitative and quantitative traits relevant to mammalian physiology and pathobiology.

Age-dependent variation of genotypes in MHC II transactivator gene (CIITA) in controls and association to type 1 diabetes.

The major histocompatibility complex class II transactivator (CIITA) gene (16p13) has been reported to associate with susceptibility to multiple sclerosis, rheumatoid arthritis and myocardial infarction, recently also to celiac disease at genome-wide level. However, attempts to replicate association have been inconclusive. Previously, we have observed linkage to the CIITA region in Scandinavian type 1 diabetes (T1D) families. Here we analyze five Swedish T1D cohorts and a combined control material from previous studies of CIITA. We investigate how the genotype distribution within the CIITA gene varies depending on age, and the association to T1D. Unexpectedly, we find a significant difference in the genotype distribution for markers in CIITA (rs11074932, P=4 × 10(-5) and rs3087456, P=0.05) with respect to age, in the collected control material. This observation is replicated in an independent cohort material of about 2000 individuals (P=0.006, P=0.007). We also detect association to T1D for both markers, rs11074932 (P=0.004) and rs3087456 (P=0.001), after adjusting for age at sampling. The association remains independent of the adjacent T1D risk gene CLEC16A. Our results indicate an age-dependent variation in CIITA allele frequencies, a finding of relevance for the contrasting outcomes of previously published association studies.

Low risk HLA-DQ and increased body mass index in newly diagnosed type 1 diabetes children in the Better Diabetes Diagnosis study in Sweden.

OBJECTIVE: Type 1 diabetes and obesity has increased in childhood. We therefore tested the hypothesis that type 1 diabetes human leukocyte antigen DQ (HLA-DQ) risk genotypes may be associated with increased body mass index (BMI). DESIGN: The type 1 diabetes high-risk HLA-DQ A1*05:01-B1*02:01/A1*03:01-B1*03:02 genotype along with lower risk DQ genotypes were determined at the time of clinical onset by PCR and hybridization with allele-specific probes. BMI was determined after diabetes was stabilized. SUBJECTS: A total of 2403 incident type 1 diabetes children below 18 years of age were ascertained in the Swedish national Better Diabetes Diagnosis (BDD) study between May 2005 to September 2009. All children classified with type 1 diabetes, including positivity for at least one islet autoantibody, were investigated. RESULTS: Overall, type 1 diabetes HLA-DQ risk was negatively associated with BMI (P<0.0008). The proportion of the highest risk A1*05:01-B1*02:01/A1*03:01-B1)03:02 genotype decreased with increasing BMI (P<0.0004). However, lower risk type 1 diabetes DQ genotypes were associated with an increased proportion of patients who were overweight or obese (P<0.0001). Indeed, the proportion of patients with the low-risk A1*05:01-B1*02:01/A1*05:01-B1*02:01 genotype increased with increasing BMI (P<0.003). The magnitude of association on the multiplicative scale between the A1*05:01-B1*02:01/A1*05:01-B1*02:01 genotype and increased BMI was significant (P<0.006). The odds ratio in patients with this genotype of being obese was 1.80 (95% confidence interval 1.21-2.61; P<0.006). The increased proportion of overweight type 1 diabetes children with the A1*05:01-B1*02:01 haplotype was most pronounced in children diagnosed between 5 and 9 years of age. CONCLUSIONS: Susceptibility for childhood type 1 diabetes was unexpectedly found to be associated with the A1*05:01-B1*02:01/A1*05:01-B1*02:01 genotype and an increased BMI. These results support the hypothesis that overweight may contribute to the risk of type 1 diabetes in children positive for HLA-DQ A1*05:01-B1*02:01.