Changes in GAD65Ab-specific antiidiotypic antibody levels correlate with changes in C-peptide levels and progression to islet cell autoimmunity

CONTEXT

The previously reported absence of 65-kDa glutamate decarboxylase antibody (GAD65Ab)-specific antiidiotypic antibodies (anti-Id) in type 1 diabetes (T1D) patients at clinical onset could be due to an inability to mount an antibody response to GAD65Ab or a longitudinal decline in anti-Id levels.

OBJECTIVE AND DESIGN

We investigated anti-Id levels in longitudinal samples obtained from T1D patients (n = 41) (clinical diagnosis - 12 months), and latent autoimmune diabetes in adults (LADA) patients (n = 32) who received alum-formulated human recombinant GAD65 (baseline - 12 months). We also determined anti-Id levels in a small cohort of Type 2 diabetes patients during their development of autoimmune T cell responses.

RESULTS

At clinical onset T1D patients presented no or low anti-Id levels. However, 22/41 T1D patients showed ≥50% increase in GAD65Ab-specific anti-Id levels during follow-up; peaking at 3 (n = 1), 6 (n = 10), 9 (n = 10), or 12 (n = 1) months. Increasing anti-Id levels marked patients who experienced a temporary increase in C-peptide levels. Anti-Id levels correlated significantly with glycated hemoglobin and C-peptide levels at 6 and 9 months (P values ranged from <0.001 to <0.05). In LADA patients receiving placebo, anti-Id levels declined in seven of nine patients, whereas four of five patients receiving 20 μg alum-formulated human recombinant GAD65 showed increasing anti-Id levels. Changes in anti-Id and C-peptide levels closely correlated (P < 0.0001). The significant decline in anti-Id levels (P = 0.03) in T2D patients developing T cell autoimmune responses supports our hypothesis that declining anti-Id levels are associated with developing islet autoimmunity.

CONCLUSIONS

The close association between GAD65Ab-specific anti-Id levels and β-cell function may provide a novel marker for the progression of autoimmune diabetes.

Genes and alcohol

The negative effects of excessive alcohol use include dependence, psychiatric co-morbidity and increased risk for suicide. A dominating risk factor is heritage. A large number of studies have addressed the genetic basis, either "candidate genes" in the brain reward system, or searched for unknown genes in family studies by linkage analysis. It is clear that no single gene polymorphism is of use in preventive medicine. A consistent finding, however, is that polymorphism in the alcohol dehydrogenase cluster and other metabolic pathways are of some relevance on a population basis, suggesting a link between alcohol toxicity in general and dependence. An emerging concern is potential gender differences as women, who are generally more sensitive, acquire male drinking habits.

Major histocompatibility complex class II transactivator gene polymorphism: associations with Löfgren's syndrome

The major histocompatibility complex (MHC) class II transactivator (MHC2TA) is known as a master regulator for expression of MHC class II molecules. In the present study, we investigated the influence on the risk for sarcoidosis of two variants of the MHC2TA gene, selected from previous association studies of inflammatory diseases. Seven hundred and twenty-eight sarcoidosis patients and 873 controls matched by ethnicity were included in the study. Patients were classified as with Löfgren's syndrome (or not) as subphenotypes. Individuals were genotyped for two single nucleotide polymorphisms (SNPs) of the MHC2TA gene, rs3087456 A/G and rs11074932 C/T, and were human leukocyte antigen (HLA)-DRB1-typed. After correction for multiple testing, our data showed a significant association with Löfgren's syndrome in allelic model for the rs3087456 SNP, which was not detected in non-Löfgren's patients. A similar trend was noted for the rs11074932 SNP. These risk factors were independent of HLA-DRB1*03, which is known to be associated with Löfgren's syndrome. The finding of a new genetic association between Löfgren's syndrome and MHC2TA gene polymorphisms, which seems independent of HLA-DRB1*03 and relates to the expression of MHC class II molecules, strongly supports the idea that Löfgren's syndrome is a separate disease entity.

RGMA and IL21R show association with experimental inflammation and multiple sclerosis

Rat chromosome 1 harbors overlapping quantitative trait loci (QTL) for cytokine production and experimental models of inflammatory diseases. We fine-dissected this region that regulated cytokine production, myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE), anti-MOG antibodies and pristane-induced arthritis (PIA) in advanced intercross lines (AILs). Analysis in the tenth and twelfth generation of AILs resolved the region in two narrow QTL, Eae30 and Eae31. Eae30 showed linkage to MOG-EAE, anti-MOG antibodies and levels of interleukin-6 (IL-6). Eae31 showed linkage to EAE, PIA, anti-MOG antibodies and levels of tumor necrosis factor (TNF) and IL-6. Confidence intervals defined a limited set of potential candidate genes, with the most interesting being RGMA, IL21R and IL4R. We tested the association with multiple sclerosis (MS) in a Nordic case-control material. A single nucleotide polymorphism in RGMA associated with MS in males (odds ratio (OR)=1.33). Polymorphisms of RGMA also correlated with changes in the expression of interferon-gamma (IFN-gamma) and TNF in cerebrospinal fluid of MS patients. In IL21R, there was one positively associated (OR=1.14) and two protective (OR=0.87 and 0.68) haplotypes. One of the protective haplotypes correlated to lower IFN-gamma expression in peripheral blood mononuclear cells of MS patients. We conclude that RGMA and IL21R and their pathways are crucial in MS pathogenesis and warrant further studies as potential biomarkers and therapeutic targets.

Genetic variants of CC chemokine genes in experimental autoimmune encephalomyelitis, multiple sclerosis and rheumatoid arthritis

Multiple sclerosis (MS) is a complex disorder of the central nervous system, causing inflammation, demyelination and axonal damage. A limited number of genetic risk factors for MS have been identified, but the etiology of the disease remains largely unknown. For the identification of genes regulating neuroinflammation we used a rat model of MS, myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE), and carried out a linkage analysis in an advanced intercross line (AIL). We thereby redefine the Eae18b locus to a 0.88 Mb region, including a cluster of chemokine genes. Further, we show differential expression of Ccl2, Ccl11 and Ccl11 during EAE in rat strains with opposite susceptibility to EAE, regulated by genotype in Eae18b. The human homologous genes were tested for association to MS in 3841 cases and 4046 controls from four Nordic countries. A haplotype in CCL2 and rs3136682 in CCL1 show a protective association to MS, whereas a haplotype in CCL13 is disease predisposing. In the HLA-DRB1* 15 positive subgroup, we also identified an association to a risk haplotype in CCL2, suggesting an influence from the human leukocyte antigen (HLA) locus. We further identified association to rheumatoid arthritis in CCL2, CCL8 and CCL13, indicating common regulatory mechanisms for complex diseases.

Cornulin, a marker of late epidermal differentiation, is down-regulated in eczema

BACKGROUND

Eczema is a common chronic inflammatory skin disorder which shows strong genetic predisposition. To identify new potential molecular determinants of the disease pathogenesis, we performed a gene expression study in an eczema mouse model. This analysis identified a marked down regulation of the cornulin gene (CRNN), a member of the epidermal differentiation complex, in the eczema-like skin. We then investigated CRNN as an eczema candidate gene and studied its polymorphism and the expression in the skin of eczema patients.

METHODS

An eczema-like phenotype was induced in mice by allergen (Der p2) patching. Gene expression analysis was performed with the subtractive suppression hybridization method and validated by real time PCR and the transmission disequilibrium test was used to test for genetic associations in 406 multiplex eczema families.

RESULTS

Der p 2 patched mice developed a localized eczema and a Th 2 skewed systemic response. Real time PCR analysis confirmed a down regulation of CRNN mRNA in eczema-like skin in the mouse model and in human eczema. The CRNN polymorphism rs941934 was significantly associated with atopic eczema in the genetic analysis (P = 0.006), though only as part of an extended haplotype including a known associated variant (2282del4) in the filaggrin gene.

CONCLUSIONS

CRNN mRNA expression is decreased in eczematous skin. Further studies are needed to verify whether the associated cornulin polymorphism contribute to the genetic susceptibility in eczema.

The non-inherited maternal HLA haplotype affects the risk for type 1 diabetes

The aim was to test the hypothesis that the human leucocyte antigen (HLA) haplotype that is not inherited from the mother, that is, the non-inherited maternal antigen (NIMA) affects the risk for type 1 diabetes (T1D). A total of 563 children with T1D and 286 non-diabetic control children from Sweden were genotyped for DRB1, DQA1 and DQB1 alleles. The frequency of positively (DR4-DQA1*0301-B1*0302 and DR3-DQA1*0501-B1*0201), negatively (DR15-DQ A1*0102-B1*0602) or neutrally (all other) T1D associated HLA haplotypes were compared between NIMA and non-inherited paternal antigen (NIPA). All comparisons were carried out between HLA-matched patients and controls. The frequency of positively associated NIMA was higher among both DR4/X-positive healthy individuals compared wit DR4/X-positive patients (P < 0.00003) and DR3/X-positive healthy individuals compared with DR3/X-positive patients (P < 0.009). No such difference was observed for NIPA. High-risk NIMA was increased compared to NIPA among healthy DR3/X- and DR4/X-positive children (P < 0.05). There was no difference in frequency of positively associated haplotypes between patient NIMA and NIPA. The NIMA but not the NIPA affects the risk for T1D, suggesting that not only the inherited but also non-inherited maternal HLA haplotypes, perhaps through microchimerism or other mechanisms, may influence the risk for the disease.

No evidence of association of the PDCD1 gene with Type 1 diabetes

AIMS

To test the association between the immunoreceptor PD-1 (PDCD1) gene and Type 1 diabetes mellitus (T1DM). This gene has been reported to be associated with other autoimmune diseases such as systemic lupus erythematosus (SLE) as well as T1DM.

METHODS

Genotyping of single nucleotide polymorphisms (SNPs) in the PDCD1 gene was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), pyrosequencing and TaqMan in two separate cohorts of Swedish patients and control subjects: a family study consisting of 184 multiplex and eight simplex families and a case-control study consisting of 586 patients and 836 control subjects. Three SNPs were genotyped: PD-1 7146, PD-1 7785 and PD-1 8738.

RESULTS

We did not detect any association or linkage between SNPs in PDCD1 and T1DM. We further performed a meta-analysis for association of PD-1 7146, PD-1 7785 and PD-1 8738 to T1DM. We detected heterogeneity in association with weak evidence for overall association.

CONCLUSIONS

We conclude that PDCD1 is unlikely to be a major susceptibility gene for T1DM.

Islet cell autoantibody levels after the diagnosis of young adult diabetic patients

AIMS

The aim was to determine the course of islet cell antibodies [glutamate decarboxylase (GADA), tyrosine phosphatase-like islet antigen 2 (IA-2A) and islet cell (ICA)] after the diagnosis of the diabetic patient.

METHODS

The Diabetes Incidence Study in Sweden (DISS) attempted to prospectively enrol all newly diagnosed diabetic patients aged 15-34 years during 1992 and 1993. C-peptide and autoantibody levels were determined from venous blood samples at diagnosis and again at yearly intervals for 6 years.

RESULTS

After the first year, the odds of remaining GADA positive decreased by 9% per year [odds ratio (OR) = 0.91, 95% confidence interval (CI) = 0.85-0.96] while the mean GADA index remained unchanged ( = 0.8, P = 0.37). There was no change in the percentage of subjects testing IA-2A positive after the first year ( = 0.1, P = 0.75). However, the mean index decreased 0.04 per year (95% CI: 0.03-0.05)-a 7.9% decline (95% CI: 5.4-10.4%). The odds of a subject testing positive for ICA decreased by 24% per year (OR = 0.76, 95% CI = 0.70-0.82). The mean ICA levels decreased 0.75 per year (95% CI: 0.66-0.84)-a 16.4% decline (95% CI: 14.1-18.6%). The rate of change in titres for all three autoantibodies was independent of gender, human leucocyte antigen genotype and C-peptide status.

CONCLUSIONS

GADA levels remained high while ICA levels declined. In contrast to a previous study, we found that the proportion of IA-2A subjects remaining positive did not decrease after the first year, while the average index decreased slightly.

Relative predispositional effects of HLA class II DRB1-DQB1 haplotypes and genotypes on type 1 diabetes: a meta-analysis

The direct involvement of the human leukocyte antigen class II DR-DQ genes in type 1 diabetes (T1D) is well established, and these genes display a complex hierarchy of risk effects at the genotype and haplotype levels. We investigated, using data from 38 studies, whether the DR-DQ haplotypes and genotypes show the same relative predispositional effects across populations and ethnic groups. Significant differences in risk within a population were considered, as well as comparisons across populations using the patient/control (P/C) ratio. Within a population, the ratio of the P/C ratios for two different genotypes or haplotypes is a function only of the absolute penetrance values, allowing ranking of risk effects. Categories of consistent predisposing, intermediate ('neutral'), and protective haplotypes were identified and found to correlate with disease prevalence and the marked ethnic differences in DRB1-DQB1 frequencies. Specific effects were identified, for example for predisposing haplotypes, there was a statistically significant and consistent hierarchy for DR4 DQB1*0302s: DRB1*0405 =*0401 =*0402 > *0404 > *0403, with DRB1*0301 DQB1*0200 (DR3) being significantly less predisposing than DRB1*0402 and more than DRB1*0404. The predisposing DRB1*0401 DQB1*0302 haplotype was relatively increased compared with the protective haplotype DRB1*0401 DQB1*0301 in heterozygotes with DR3 compared with heterozygotes with DRB1*0101 DQB1*0501 (DR1). Our results show that meta-analyses and use of the P/C ratio and rankings thereof can be valuable in determining T1D risk factors at the haplotype and amino acid residue levels.

IA-2 autoantibodies in incident type I diabetes patients are associated with a polyadenylation signal polymorphism in GIMAP5

In a large case-control study of Swedish incident type I diabetes patients and controls, 0-34 years of age, we tested the hypothesis that the GIMAP5 gene, a key genetic factor for lymphopenia in spontaneous BioBreeding rat diabetes, is associated with type I diabetes; with islet autoantibodies in incident type I diabetes patients or with age at clinical onset in incident type I diabetes patients. Initial scans of allelic association were followed by more detailed logistic regression modeling that adjusted for known type I diabetes risk factors and potential confounding variables. The single nucleotide polymorphism (SNP) rs6598, located in a polyadenylation signal of GIMAP5, was associated with the presence of significant levels of IA-2 autoantibodies in the type I diabetes patients. Patients with the minor allele A of rs6598 had an increased prevalence of IA-2 autoantibody levels compared to patients without the minor allele (OR=2.2; Bonferroni-corrected P=0.003), after adjusting for age at clinical onset (P=8.0 x 10(-13)) and the numbers of HLA-DQ A1*0501-B1*0201 haplotypes (P=2.4 x 10(-5)) and DQ A1*0301-B1*0302 haplotypes (P=0.002). GIMAP5 polymorphism was not associated with type I diabetes or with GAD65 or insulin autoantibodies, ICA, or age at clinical onset in patients. These data suggest that the GIMAP5 gene is associated with islet autoimmunity in type I diabetes and add to recent findings implicating the same SNP in another autoimmune disease.

Genome-wide linkage analysis of allergic rhinoconjunctivitis in a Swedish population

BACKGROUND

Allergic rhinoconjunctivitis is a common complex disorder characterized by itching and irritation in the nose, bouts of sneezing, watery rhinorrhoea, nasal congestion and itchy eyes with tears and swelling. Like other atopic disorders such as allergic asthma and atopic dermatitis, the development involves complex interactions of genes and environmental factors.

OBJECTIVE

The purpose of this study was to identify susceptibility loci for allergic rhinoconjunctivitis.

METHODS

We conducted a genome-wide linkage analysis using a non-parametric, affected-relative-pair method. The 250 families used were collected originally for an atopic dermatitis linkage study.

RESULTS

Three regions showed favour in evidence of linkage to allergic rhinoconjunctivitis: 3q13 (D3S1278: logarithm of odds ratio (LOD)=1.64, P<0.003), 4q34-35 (D4S1652: LOD=1.49, P<0.005) and 18q12 (D18S535: LOD=1.94, P<0.002). In addition, four regions showed weaker evidence in favour of linkage: 6p22-24 (D6S1959: LOD=1.39, P<0.006), 9p11-q12 (D9S1118: LOD=1.15, P<0.02), 9q33.2-34.3 (D9S915: LOD=1.29, P<0.01) and 17q11.2 (D17S1294: LOD=1.13, P<0.02). In single-point analysis, one locus on chromosome 3 close to marker D3S1278 reaches the suggestive level (LOD=2.28, P<6 x 10(-4)) while one on chromosome 17 close to marker D17S921 almost reaches this level (LOD=2.17, P<8 x 10(-4), Table 3).

CONCLUSION

Our results support the linkage to allergic rhinoconjunctivitis on 3q13, 6p23-p24 and 9q34.3 shown in previous investigations.

Elevated expression and genetic association links the SOCS3 gene to atopic dermatitis

In a systematic analysis of global gene-expression patterns, we found that SOCS3 messenger RNA was significantly more highly expressed in skin from patients with atopic dermatitis than in skin from healthy controls, and immunohistochemical analysis confirmed a similar elevation of SOCS3 protein. Furthermore, we found a genetic association between atopic dermatitis and a haplotype in the SOCS3 gene in two independent groups of patients (P<.02 and P<.03). These results strongly suggest that SOCS3, located in a chromosomal region previously linked to the disease (17q25), is a susceptibility gene for atopic dermatitis.

Susceptibility loci for atopic dermatitis on chromosome 21 in a Swedish population

BACKGROUND

Atopic dermatitis (AD) is a hereditary, pruritic, chronic, relapsing, inflammatory skin disease resulting from multiplex interactions between genes and environmental factors. We have previously found several loci showing suggestive linkage on chromosomes 3q14, 13q14, 15q14-15 and 17q21, and weaker linkage to chromosomes 1p32, 4q24-26 and 21q21 in 109 Swedish families.

METHODS

In order to confirm the linkage to chromosome 21, we carried out a replication linkage analysis with additional microsatellite markers on chromosome 21 in another set of 295 families.

RESULTS

In the extended material, the Z-score was 2.40 (P < 7.4 x 10(-4)) in the region 21q21 for a semi-quantitative variable measurement; the severity of AD. When combining the two data sets into 404 families and stratifying according to asthma status, suggestive linkage was found only in the group of AD patients who also had asthma (Z-score 2.45, P < 7.4 x 10(-4) and 2.69, P < 7.4 x 10(-4)) in two different regions.

CONCLUSIONS

Our results suggest that 21q21 could contain a susceptibility gene modulating the severity of AD especially in combination with asthma.

Linkage disequilibrium and haplotype blocks in the MHC vary in an HLA haplotype specific manner assessed mainly by DRB1*03 and DRB1*04 haplotypes

First generation linkage disequilibrium (LD) and haplotype maps of the human major histocompatibility complex (MHC) have been generated in order to aid the unraveling of the numerous disease predisposing genes in this region by offering a first set of haplotype tagSNPs. Several parameters, like the population studied, the marker map used, the density of polymorphisms and the applied algorithm, are influencing the appearance of haplotype blocks and selection of tags. The MHC comprises a limited number of ancestral, conserved haplotypes. We address the impact of the underlying HLA haplotypes on the LD patterns, haplotype blocks and tag selection throughout the entire extended MHC (xMHC) by studying DR-DQ haplotypes, mainly those carrying DRB1*03 and DRB1*04 alleles. We observed significantly different degree and extent of LD calculated on different HLA backgrounds, as well as variation in the size and boundaries of the defined haplotype and tags selected. Our results demonstrate that the underlying ancestral HLA haplotypic architecture is yet another parameter to take into consideration when constructing LD maps of the xMHC. This may be essential for mapping of disease susceptibility genes since many diseases are associated with and map on particular HLA haplotypes.

Polymorphisms of estrogen receptor beta gene are associated with hypospadias

INTRODUCTION

Hypospadias is a common male congenital urethral malformation, defined as the displacement of the urethral meatus ventrally from the tip of the glans penis. The importance of androgen receptor in male external genitalia development has been well recognized. Recently, the presence of active estrogen receptors (ER) in the developing male external genitalia has also been demonstrated. There are two isoforms of the human estrogen receptor, ESR1 and ESR2, which occur, with distinct tissue and cell patterns of expression. We hypothesized that modifications in these nuclear receptors' genes could lead to hypospadias.

MATERIALS AND METHODS

We screened 60 boys with hypospadias for mutations in the coding regions of ESR1 and ESR2 genes, by denaturing high-performance liquid chromatography and automated sequence analysis. We also genotyped the CA repeat polymorphism in ESR2 and the TA repeat polymorphism in ESR1.

RESULTS

The CA repeat polymorphism in ESR2 is prolonged in hypospadias patients compared to controls (p < 0.05). Prolongation of this CA repeat polymorphism has previously been associated with lower levels of testosterone. Six patients presented the genetic variant 2681-4A > G (rs944050) in the heterozygous form in ESR2, which was a significantly higher frequency than in the control population (p < 0.05). One of these patients also presented a 266_267insC in exon 1 of ESR2, which is also a known single nucleotide polymorphism (SNP; rs3832949). In ESR1, no significant gene alteration was found to be associated with hypospadias.

CONCLUSIONS

Our results suggest that variations in the ESR2 might influence susceptibility to hypospadias.

D6S265*15 marks a DRB1*15, DQB1*0602 haplotype associated with attenuated protection from type 1 diabetes mellitus

AIMS/HYPOTHESIS

The HLA class II DQB1*0602 allele confers strong dominant protection against type 1 diabetes but protection is not absolute. The aim of this study was to identify markers within the HLA region that differentiate DQB1*0602 haplotypes and show different associations with disease risk.

METHODS

We defined alleles at eight microsatellite markers spanning the HLA region in a case-control cohort from Sweden.

RESULTS

We found that allele 15 at marker D6S265 (109 kb centromeric of HLA-A) was over-represented among patients carrying DRB1*15, DQB1*0602. A detailed haplotype analysis showed that DRB1*15, DQB1*0602 haplotypes carrying D6S265*15 have a ten-fold higher odds ratio (OR) than those carrying other alleles and thus confer reduced protection [OR D6S265*15=0.186 (95% CI 0.074, 0.472) vs OR D6S265*15-=0.017 (95% CI 0.005, 0.062), p<0.001].

CONCLUSIONS/INTERPRETATION

Our data support the existence of a locus that modifies the protective effect associated with DQB1*0602. Typing for allele D6S265*15 can identify a less protective DQB1*0602 haplotype, thereby allowing a more accurate prediction of type 1 diabetes risk.

Increased risk of diabetes among relatives of female insulin-treated patients diagnosed at 15-34 years of age

AIMS

This study aimed to determine the risk of developing diabetes among relatives of patients diagnosed between 15 and 34 years of age who were treated with insulin. Our second aim was to determine whether there was a difference in risk of diabetes between relatives of male and female patients.

METHODS

A questionnaire was sent to patients in the Diabetes Incidence Study in Sweden registry diagnosed between 1983 and 1993 to determine the presence of first-degree relatives with diabetes.

RESULTS

In 3087 index patients treated with insulin, 17.8% (95% confidence interval 16.5, 19.2) had a first-degree relative (excluding offspring) treated with insulin, the frequency being higher in female (19.8%) than in male (16.5%, P = 0.018) patients. A total of 10.7% had a parent treated with insulin. The prevalence of insulin-treated diabetes was higher among parents of female (12.5%) than of male (9.5%), insulin-treated index patients (P = 0.0068). A similar difference was observed using life table analysis (P = 0.0025), which also showed that the risk by 63 years of age was 7.6% for parents of female and 4.9% for parents of male insulin-treated index patients. In insulin-treated index patients, 8.4% had a sibling with insulin-treated diabetes.

CONCLUSIONS

We conclude that the risk for relatives of women with insulin-treated diabetes was higher than for relatives of insulin-treated male patients. We suggest that greater genetic susceptibility is required for females compared with males in the 15-34 age group in order to develop diabetes and hence females might carry more diabetes genes since more of their relatives also develop diabetes.

Multiplicity of the antibody response to GAD65 in Type I diabetes

Type I diabetes (TID) is an autoimmune disease characterized in part by the presence of autoantibodies directed against glutamic acid decarboxylase 65 (GAD65), among other pancreatic islet antigens. We investigated the independent epitope specificities of these GAD65 antibodies (GAD65Ab) and their combinations in the sera of new onset TID patients and first-degree relatives positive for GAD65Ab. For our analysis, we used four GAD65-specific recombinant Fabs (rFabs) that recognize different conformational determinants of GAD65 located throughout the molecule, including the N-terminal, the middle and the C-terminal regions. We used these epitope-specific rFabs in competition assays to determine the binding specificity of the autoantibodies found in patient sera. Among the 61 sera from newly diagnosed GAD65Ab-positive TID patients GAD65 binding was competed for 23 sera by all four rFabs, 29 by at least two rFabs, and in nine sera were displaced by one or no rFab. In contrast, none of the 24 sera from GAD65Ab-positive first-degree relatives of TID patients were displaced by all four rFabs. When using all four rFabs simultaneously to compete with GAD65Ab binding, binding of sera from TID patients was reduced by an average of 70%. A significantly weaker competition was observed when evaluating sera of GAD65Ab-positive first-degree relatives (P < 0.0001).

Conformation-dependent GAD65 autoantibodies in diabetes

AIMS/HYPOTHESIS

Conformation-dependent autoantibodies directed against GAD65 are markers of Type 1 diabetes. In this study we aimed to determine whether the substitution of GAD65 with GAD67 amino acids would affect the binding of conformation-dependent GAD65 autoantibodies.

METHODS

We used PCR-based site-directed mutagenesis to generate a series of mutated GAD65 cDNA constructs in which specific GAD65 coding sequences for regions of the protein critical for autoantibody binding were replaced with GAD67 coding sequences.

RESULTS

The introduction of a point mutation at position 517, substituting glutamic acid with proline, markedly reduced the binding of disease-associated GAD65 antibodies. The binding of GAD65 antibodies to the E517P mutant was reduced in the sera of all newly diagnosed Type 1 diabetes patients ( n=85) by a mean of 72% ( p<0.0001) compared with binding to wild-type GAD65. Patients with latent autoimmune diabetes in adults ( n=24) showed a similar reduction in binding (79% reduction, p<0.0001). First-degree relatives who subsequently progressed to Type 1 diabetes ( n=12) showed a reduction in binding of 80% compared with a reduction of only 65% among relatives who had not progressed to disease ( n=38; p=0.025). In healthy GAD65Ab-positive individuals who did not progress to diabetes during a 9-year follow-up period ( n=51), binding to GAD65-E517P was reduced by only 28% compared with binding to wild-type GAD65.

CONCLUSIONS/INTERPRETATION

Differences in autoantibody binding to wild-type GAD65 versus GAD65-E517P may provide predictive information about Type 1 diabetes risk beyond that provided by the presence or absence of GAD65 autoantibodies. Lack of binding to mutant GAD65-E517P defines GAD65-positive individuals who are at higher risk of developing diabetes.

Normal weight promotes remission and low number of islet antibodies prolong the duration of remission in Type 1 diabetes

AIM

To identify clinical, immunological and biochemical factors that predict remission, and its duration in a large cohort of young adults with Type 1 diabetes mellitus (DM).

METHODS

In Sweden, 362 patients (15-34 years), classified as Type 1 DM were included in a prospective, nation-wide population-based study. All patients were followed at local hospitals for examination of HbA(1c) and insulin dosage over a median period after diagnosis of 5 years. Duration of remission, defined as an insulin maintenance dose </= 0.3 U/kg/24 h and HbA(1c) within the normal range, was analysed in relation to characteristics at diagnosis.

RESULTS

Remissions were seen in 43% of the patients with a median duration of 8 months (range 1-73). Sixteen per cent had a remission with a duration > 12 months. Among patients with antibodies (ab(+)), bivariate analysis suggested that adult age, absence of low BMI, high plasma C-peptide concentrations, lack of ketonuria or ketoacidosis at diagnosis and low insulin dose at discharge from hospital were associated with a high possibility of achieving remission. Multiple regression showed that normal weight (BMI of 20-24.9 kg/m(2)) was the only factor that remained significant for the possibility of entering remission. In survival analysis among ab(+) remitters, a low number of islet antibodies, one or two instead of three or four, were associated with a long duration of remissions.

CONCLUSION

In islet antibody-positive Type 1 DM, normal body weight was the strongest factor for entering remission, whilst a low number of islet antibodies was of importance for the duration.

HLA associations in type 1 diabetes: DPB1 alleles may act as markers of other HLA-complex susceptibility genes

Alleles at the HLA-DQB1, -DQA1 and -DRB1 loci are major determinants for susceptibility to develop type 1 diabetes (T1D). Increasing evidence supports that also other genes in, or near, the HLA complex contribute to the HLA-encoded risk. Alleles at the DPB1 locus have been suggested to directly influence the risk conferred by DQB1, DQA1 and DRB1 alleles, but the results are conflicting. We therefore genotyped 217 families from Norway, Denmark, Sweden and southern France to address the role of DPB1 alleles in T1D. After taking into account linkage disequilibrium (LD) with DQB1, DQA1 and DRB1 alleles, we found evidence that some DPB1 alleles are associated with modulating the risk of developing T1D. However, we show that the strong LD in the HLA complex, and the presence of extended haplotypes complicate the interpretation of the results. On DQ2-DR3 haplotypes, both allele 3 at microsatellite D6S2223 located 5.3-Mb telomeric of DPB1 and the extended DQ2-DR3-B18 haplotype display much stronger association than DPB1 alleles. When we exclude these effects, most of the apparent association of DPB1 alleles on DQ2-DR3 haplotypes disappear. Taken together, although we cannot completely rule out an effect of some DPB1 alleles, we propose that the statistically significant, albeit weak, DPB1 associations found are most likely the result of LD with another unidentified disease-susceptibility gene(s) in this region.