Age-dependent association of HLA-A24 in Japanese IDDM patients

Bridging Mice to Men: Using HLA Transgenic Mice to Enhance the Future Prediction and Prevention of Autoimmune Type 1 Diabetes in Humans

Similar to the vast majority of cases in humans, the development of type 1 diabetes (T1D) in the NOD mouse model is due to T-cell mediated autoimmune destruction of insulin producing pancreatic β cells. Particular major histocompatibility complex (MHC) haplotypes (designated HLA in humans; and H2 in mice) provide the primary genetic risk factor for T1D development. It has long been appreciated that within the MHC, particular unusual class II genes contribute to the development of T1D in both humans and NOD mice by allowing for the development and functional activation of β cell autoreactive CD4 T cells. However, studies in NOD mice have revealed that through interactions with other background susceptibility genes, the quite common class I variants (K(d), D(b)) characterizing this strain's H2 (g7) MHC haplotype aberrantly acquire an ability to support the development of β cell autoreactive CD8 T cell responses also essential to T1D development. Similarly, recent studies indicate that in the proper genetic context some quite common HLA class I variants also aberrantly contribute to T1D development in humans. This review focuses on how "humanized" HLA transgenic NOD mice can be created and used to identify class I dependent β cell autoreactive CD8 T cell populations of clinical relevance to T1D development. There is also discussion on how HLA transgenic NOD mice can be used to develop protocols that may ultimately be useful for the prevention of T1D in humans by attenuating autoreactive CD8 T cell responses against pancreatic β cells.

Novel gene associations in type 1 diabetes

Recent genome-wide association studies have been able to identify multiple new gene loci affecting type 1 diabetes susceptibility, but the impact of these new defined loci seems to decrease in parallel with their number. The HLA gene region remains the main nominator of genetic susceptibility, although the identity of important genes and especially the mechanisms of their action are still largely unclear. Products of HLA and most other known risk genes are involved in regulation of the immune system in accordance with the autoimmune nature of the disease. The multitude of genes involved in the pathogenesis implies complex pathways where multiple steps in each may be essential in turning the balance of immune response to beta-cell destructing autoimmunity.

Bridging mice to men: using HLA transgenic mice to enhance the future prediction and prevention of autoimmune type 1 diabetes in humans

Similar to the vast majority of cases in humans, the development of type 1 diabetes (T1D) in the NOD mouse model is due to T-cell mediated autoimmune destruction of insulin-producing pancreatic beta cells. Particular major histocompatibility complex (MHC) haplotypes (designated HLA in humans and H2 in mice) provide the primary genetic risk factor for T1D development. It has long been appreciated that within the MHC, particular unusual class II genes contribute to the development of T1D in both humans and NOD mice by allowing for the development and functional activation of beta-cell autoreactive CD4 T cells. However, studies in NOD mice have revealed that through interactions with other background susceptibility genes, the quite common class I variants (K(d), D(b)) characterizing this strain's H2 ( g7 ) MHC haplotype aberrantly acquire an ability to support the development of beta cell autoreactive CD8 T-cell responses also essential to T1D development. Similarly, recent studies indicate that in the proper genetic context some quite common HLA class I variants also aberrantly contribute to T1D development in humans. This chapter will focus on how "humanized" HLA transgenic NOD mice can be created and used to identify class I-dependent beta cell autoreactive CD8 T-cell populations of clinical relevance to T1D development. There is also discussion on how HLA transgenic NOD mice can be used to develop protocols that may ultimately be useful for the prevention of T1D in humans by attenuating autoreactive CD8 T-cell responses against pancreatic beta cells.

"Humanized" HLA transgenic NOD mice to identify pancreatic beta cell autoantigens of potential clinical relevance to type 1 diabetes

The mechanistic basis by which the H2(g7) major histocompatibility complex (MHC) provides the primary risk factor for the development of T cell-mediated autoimmune type 1 diabetes (T1D) in non-obese diabetic (NOD) mice involves contributions not only from the unusual A(g7) class II molecule, but also from the more common K(d) and/or D(b) class I variants it encodes. Similarly, transgenic studies in NOD mice have confirmed the possibility first suggested in association studies that in the proper genetic context the common human HLA-A2.1 class I variant can mediate diabetogenic CD8 T cell responses. T1D continues to develop in a further refined NOD stock that expresses human HLA-A2.1, but no murine class I molecules (designated NOD.beta2m-.HHD). Islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) is an important antigenic target of diabetogenic CD8 cells in standard NOD mice. Three IGRP-derived peptides have also been identified that are presented by human HLA-A2.1 molecules to diabetogenic CD8 T cells in NOD.beta2m-.HHD mice. At least one of these IGRP peptides (265-273) can also be the target of autoreactive CD8 T cells in HLA-A2.1-expressing human T1D patients. Studies are currently under way to determine whether HLA-A2.1-restricted IGRP peptides can be used in a tolerance-inducing protocol that inhibits T1D development in NOD. beta2m-.HHD mice. If so, this knowledge could ultimately lead to the development of a similar T1D prevention protocol in humans.

Slowly progressing form of type 1 diabetes mellitus in children: genetic analysis compared with other forms of diabetes mellitus in Japanese children

AIMS

Slowly progressing insulin-dependent diabetes mellitus (SPIDDM, hereafter referred to as IDDMS in this article) is a unique subtype of type 1 diabetes in Japanese children. To clarify the genetic background of IDDMS, we analyzed HLA-DRB1, -DQB1 and -DQA1 alleles, phenotypes, and genotypes and compared them with acute-onset type 1 diabetes, non-insulin-dependent diabetes mellitus (NIDDM), and control subjects.

METHODS

HLA-DRB1, -DQA1, and -DQB1 types were defined by DNA analysis using polymerase chain reaction (PCR), and typing for human leukocyte antigen (HLA) was performed by the sequencing-based typing (SBT) method using Match Maker and MT Navigator in combination. HLA-A24 was determined by the PCR-sequence-specific oligo-nucleotide probe (PCR-SSOP) method. The 234 patients with type 1 diabetes were divided into three groups: 32 cases of IDDMS, 137 cases of acute-onset form aged more than 5 yr (IDDMA), and 65 cases of acute-onset form less than 5 yr of age at onset (IDDME). In addition, we studied 55 children with type 2 diabetes (NIDDM) and 97 normal controls.

RESULTS

The patients with IDDMS were older at diagnosis and had a greater body mass index (BMI) than those with IDDM (A + E). The prevalence of islet autoantbodies was not significantly different from IDDMA. The allele frequencies of DRB1*0405, DQA1*0302, and DQB1*0401 were significantly increased; however, DRB1*0901, DQA1*03, DQB1*0303, and HLA-A24 were low and not significantly different from control subjects.

CONCLUSIONS

HLA phenotypes and genotypes in patients with IDDMS were different from those in NIDDM and control subjects and were closer to those of IDDMA. Together with a low prevalence of HLA-A24, the genetic features are similar to those of SPIDDM and latent autoimmune diabetes in adults (LADA) in adults. In our series, the clinical features such as lack of obesity and lack of responsiveness to oral hypoglycemic agents were most different from those of adults' onset.

Seroconversion of glutamic acid decarboxylase antibodies in a patient initially diagnosed as having type 2 diabetes mellitus

A 61-year-old man admitted in July 1998 had suffered from thirst, polydipsia and polyuria for three years. Diet and transient insulin therapy had induced good blood glucose control which was maintained by metformin hydrochloride for a year. Although it worsened, conventional insulin treatment re-implemented good blood glucose control. Glutamic acid decarboxylase antibodies (GAD-Ab) had been negative up to this point. After 8 months, blood glucose levels became elevated. To date, the GAD-Ab has been positive (112-120 U/ml), and the serum and urine C-peptide levels are decreased. Seroconversion of GAD-Ab should be noted in patients initially diagnosed as having GAD-Ab negative type 2 diabetes mellitus.

Peptide-specific cytotoxicity of T lymphocytes against glutamic acid decarboxylase and insulin in type 1 diabetes mellitus

Cytotoxic T lymphocytes (CTL) against pancreatic beta-cells probably play a major role in the etiology of type 1 diabetes mellitus (DM). CTLs recognize a complex formed between MHC class I and antigenic peptides fragments derived from intracellular processing of proteins. However, the exogenous peptides, which show strong affinities to MHC class I, can be presented. In this study, we focused on the cytotoxic activity of peripheral lymphocytes in patients with type 1 DM against the peptides of glutamic acid decarboxylase (GAD) and insulin, which can bind MHC class 1 A24. Lymphocytes were isolated from peripheral blood of 12 type 1 DM patients and eight healthy control subjects. The effector cells were cultured with peptides, IL-2 and IL-7, restimulated weekly by autologous antigen presenting cells, which were cultured with IL-4 and GM-CSF. On day 21, CTL activities of cultured effector cells were tested against autologous EB-blast cells as target cells pulsed with the stimulating peptides using 51Cr release assay. The results showed that cytotoxicity against insulin peptide binding to MHC class I A24 was observed in lymphocytes of four out of ten patients with type 1 DM. The mean cytotoxicity was 46.0% of the maximum release. The antibody against HLA-class I inhibited this effect. Cytotoxicity against GAD peptide which bind MHC class I A24 was not observed in seven patients. None of healthy controls showed cytotoxicity against GAD or insulin peptides was observed. This is the first report describing the cytotoxic activity of CD8+ T lymphocytes against insulin in type 1 DM.

Age-related association of MHC class I chain-related gene A (MICA) with type 1 (insulin-dependent) diabetes mellitus

To assess the contribution of the HLA class I region to susceptibility to and heterogeneity of type 1 diabetes, we investigated the association of polymorphism of MHC class I chain-related gene A (MICA) with age-at-onset as well as susceptibility to type 1 diabetes. One hundred one Japanese patients and 110 healthy control subjects were studied. The frequency of A4 allele was significantly higher and that of A6 allele was significantly lower in patients than in control subjects. The frequency of A5.1 allele was highest in early-onset patients (23.0%), intermediate in intermediate-onset patients (9.2%) and lowest in late-onset patients (7.7%) (trend chi-squared test, p = 0.0098). A5. 1 allele was strongly associated with HLA-B7 and Cw7, suggesting that MICA*A5.1-B7-Cw7 haplotype contains a gene responsible for age-at-onset. A4 allele was associated with a susceptible haplotype, DR4-DQB1*0401, and A6 allele was associated with a protective haplotype, DR2-DQB1*0601, suggesting that the association of MICA with type 1 diabetes susceptibility may be due to linkage disequilibrium with class II haplotypes. These data suggest that MICA gene is associated with age-at-onset and that a gene (or genes) responsible for age-at-onset of type 1 diabetes is located in the HLA class I region, probably near the region of MICA-B-C.

Analysis of tumor necrosis factor-alpha promoter polymorphism in type 1 diabetes: HLA-B and -DRB1 alleles are primarily associated with the disease in Japanese

Polymorphisms in the 5'-flanking region of the tumor necrosis factor (TNF)-alpha gene were examined to study the genetic background of type 1 diabetes in Japanese. Five different biallelic polymorphisms were examined in 136 type 1 diabetic patients and 300 control subjects. The frequencies of individuals carrying TNF-alpha-857T allele (designated as TNFP-D allele) or -863A/-1,031C allele (designated as TNFP-B allele) were significantly increased in the patients as compared with the controls. Since these TNF-alpha alleles are in linkage disequilibria with certain DRB1 and HLA-B alleles, two-locus analyses were carried out. The TNFP-D allele did not increase the risk in either the presence or absence of the DRB1*0405 or HLA-B54 allele, while the DRB1*0405 and HLA-B54 alleles per se could confer susceptibility in both the TNFP-D allele-positive and -negative populations. Moreover, an odds ratio was remarkably elevated in the population carrying both DRB1*0405 and HLA-B54. Similarly, the TNFP-B allele did not show significant association with the disease in either the HLA-B61-positive or -negative population, while the HLA-B61 allele could significantly increase the risk in the TNFP-B allele-positive population. These data suggest that the associations of TNFP-D and -B alleles may be secondary to their linkage disequilibria with the susceptible HLA class I and class II alleles. Because HLA-B and DRB1 genes were independently associated, both of these genes may be contributed primarily to the pathogenesis of type 1 diabetes in Japanese.

Human leukocyte antigen-A24 and -DQA1*0301 in Japanese insulin-dependent diabetes mellitus: independent contributions to susceptibility to the disease and additive contributions to acceleration of beta-cell destruction

The aim of this study is to identify insulin-dependent diabetes mellitus (IDDM)-susceptible HLA antigens in IDDM patients who do not have established risk allele, HLA-DQA1*0301, and analyze relationship of these HLA antigens and the degree of beta-cell destruction. In 139 Japanese IDDM patients and 158 normal controls, HLA-A, -C, -B, -DR and -DQ antigens were typed. Serum C-peptide immunoreactivity response (deltaCPR) to a 100-g oral glucose load < or = 0.033 nmol/l was regarded as complete beta-cell destruction. All 14 patients without HLA-DQA1*0301 had HLA-A24, whereas only 35 of 58 (60.3%) normal controls without HLA-DQA1*0301 and only 72 of 125 (57.6%) IDDM patients with HLA-DQA1*0301 had this antigen (Pc = 0.0256 and Pc = 0.0080, respectively). DeltaCPR in IDDM patients with both HLA-DQA1*0301 and HLA-A24 (0.097 +/- 0.163 nmol/L, mean +/- SD, n = 65) were lower than in IDDM patients with HLA-DQA1*0301 only (0.219 +/- 0.237 nmol/L, n = 45, P < 0.0001) and in IDDM patients with HLA-A24 only (0.187 +/- 0.198 nmol/L, n = 14, P = 0.0395). These results indicate that both HLA-DQA1*0301 and HLA-A24 contribute susceptibility to IDDM independently and accelerate beta-cell destruction in an additive manner.

Autoantibodies to multiple islet autoantigens in patients with abrupt onset type 1 diabetes and diabetes diagnosed with urinary glucose screening

It has been reported that there is a heterogeneity in the clinical course of Japanese patients with type 1 diabetes. To elucidate the associations of expression of autoantibodies to multiple islet antigens with age of onset and mode of diagnosis of diabetes in Japanese patients with type 1 diabetes, autoantibodies against the protein tyrosine phosphatase-like molecules ICA512 (IA-2) and phogrin (IA-2beta) (ICA512/phogrin-A), GAD (GADA), insulin (IAA), and islet cell cytoplasm (ICA) were determined in sera from 73 Japanese patients with type 1 diabetes obtained within 14 days of diagnosis. Patients were divided into groups based on the age of onset (</=10 years, n=24 and >10 years, n=49) or the mode of onset (abrupt onset, n=59 and urinary screening identified, n=14). Of 73 new-onset patients with type 1 diabetes, 43 (59%) and 32 (44%) had ICA512A and phogrin-A levels exceeding the 99th percentile of 184 normal control subjects, respectively. Forty-five patients (62%) were positive for either ICA512A or phogrin-A. The frequencies for other autoantibodies were 71% for GADA, 48% for IAA, and 62% for ICA. The frequency of ICA512/phogrin-A was significantly higher in patients with an age of onset less than 10 years (83%) than in patients aged >10 years (51%, P<0.01). The positivity of ICA512/phogrin-A was less in patients whose diabetes was diagnosed by the urine glucose screening test (21%, P<0.001) than in abrupt onset patients (71%). Combined analysis (>/=1 antibody) of GADA, IAA, and ICA512/phogrin-A detected 88% of abrupt onset and 93% of screening-positive patients vs. 70% and 29%, respectively, for ICA (P<0.0005). These results indicate that the expression of ICA512/phogrin-A and cytoplasmic ICA is less in patients identified by urinary glucose testing but indicate that with combined autoantibody testing 90% of patients can be identified independent of the mode of diagnosis.