Role of HLA class II alleles in Korean patients with IDDM

Critical Amino Acid Variants in HLA-DRB1 and -DQB1 Allotypes in the Development of Classical Type 1 Diabetes and Latent Autoimmune Diabetes in Adults in the Japanese Population

The effects of amino acid variants encoded by the human leukocyte antigen (HLA) class II on the development of classical type 1 diabetes (T1D) and latent autoimmune diabetes in adults (LADA) have not been fully elucidated. We retrospectively investigated the HLA-DRB1 and -DQB1 genes of 72 patients with classical T1D and 102 patients with LADA in the Japanese population and compared the frequencies of HLA-DRB1 and -DQB1 alleles between these patients and the Japanese populations previously reported by another institution. We also performed a blind association analysis with all amino acid positions in classical T1D and LADA, and compared the associations of HLA-DRB1 and -DQB1 amino acid positions in classical T1D and LADA. The frequency of DRß-Phe-13 was significantly higher and those of DRß-Arg-13 and DQß-Gly-70 were significantly lower in patients with classical T1D and LADA than in controls. The frequencies of DRß-His-13 and DQß-Glu-70 were significantly higher in classical T1D patients than in controls. The frequency of DRß-Ser-13 was significantly lower and that of DQß-Arg-70 was significantly higher in LADA patients than in controls. HLA-DRß1 position 13 and HLA-DQß1 position 70 could be critical amino acid positions in the development of classical T1D and LADA.

Genetic Epidemiology of Type 1 Diabetes in the 22 Arab Countries

Type 1 diabetes (T1D) is a complex autoimmune disorder that results from the T cell-mediated destruction of the pancreatic β cells and is due to interactions between environmental and genetic factors. Although Arabs have one of the highest global incidence and prevalence rates of T1D, unfortunately, there is a dearth of information regarding the genetic epidemiology of T1D in the Arab world. Arabs share several HLA haplotypes with other ethnic groups, which confer either susceptibility or protection to T1D, but they have specific haplotypes that are distinctive from other ethnicities. Among different Arab countries, several non-HLA genes were reported to be associated with susceptibility to T1D, including CTLA4, CD28, PTPN22, TCRβ, CD3z, IL15, BANK1, and ZAP70. In Arab countries, consanguinity, endogamy, and first-cousin marriage rates are some of the highest reported worldwide and are responsible for the creation of several inbreeding communities within the Arab world that have led to an increase in homozygosity of both the HLA haplotypes and non-HLA genes associated with either protection or susceptibility to T1D among Arabs. Homozygosity reduces the HLA complexity and is expected to facilitate our understanding of the mode of inheritance of HLA haplotypes and provide valuable insight into the intricate genotype-phenotype correlations in T1D patients. In this review, based on literature studies, I will discuss the current epidemiological profile and molecular genetic risks of Arabs with T1D.

HLA-DQB1* alleles and genetic susceptibility to type 1 diabetes mellitus

AIM: To determine human leukocyte antigen (HLA)-DQB1 allele association with susceptibility to type 1 diabetes (T1D) and to clinical and laboratory findings.

METHODS: This study was conducted on 85 unrelated Egyptian children with T1D recruited consecutively from the Pediatric Diabetes Endocrinology outpatients Clinic; Mansoura University Children’s Hospital, Egypt. Patient mean follow up period was 2.5 years. Patients were subdivided according to level of HbA1c (optimal/suboptimal control < 8.5% and poor control ≥ 8.5%). The control group consisted of 113 unrelated age- and sex-matched healthy subjects without T1D or other autoimmune diseases. Genomic DNA extraction was done for all subjects using a DNA isolation kit. HLA-Class II-DQB1 allele typing was carried out with a polymerase chain reaction-sequence-specific oligonucleotide probe using a INNO-LiPA HLA-DQB1 update kit.

RESULTS: Significant differences were detected between Egyptian patients with T1D and control groups in the frequencies of DQB1*02 [44.4% vs 18.6%, corrected P value (Pc) < 0.001] and DQB1*03 (41.2% vs 24.4%, Pc < 0.001). Significant differences were also observed between control groups and T1D patients in the frequencies of DQB1*05 (14.6% vs 7.2%, P = 0.029) and DQB1*06 (34.1% vs 7.2%, P < 0.001). However, after correction for multiple comparisons, the significance was retained for HLA-DQB1*06 (Pc < 0.001) but lost for HLA-DQB1*05. HLA-DQB1*0201, *0202, *030201 were positively associated with T1D (Pc = 0.014, Pc < 0.001, and Pc < 0.001 respectively), while HLA-DQB1*060101 was negatively associated (Pc < 0.001) with the condition. Although the HLA-DQB1 alleles 030101 and 050101 were significantly higher in controls (P = 0.016, P = 0.025 respectively), both of them lost statistical significance after correction of P value. The frequency of the HLA-DQB1 genotypes 02/02, 02/03, and 03/03 was higher in T1D patients, and the frequency of the genotypes 03/06, 05/06, and 06/06 was higher in controls, these differences being statistically significant before correction. After correction, the genotypes 02/02, 02/03 in T1D, and the genotypes 03/06, 06/06 in controls were still significant (Pc = 0.01, Pc < 0.001, Pc < 0.001, and Pc = 0.04, respectively). Non-significant associations were found between the frequency HLA-DQB1 alleles and genotypes in T1D in relation to the grade of diabetic control, Microalbuminuria, age, gender, age of presentation, weight, height, frequency of diabetic ketoacidosis (P = 0.42), serum cholesterol, and fasting and post-prandial level of C-peptide (P = 0.83, P = 0.9, respectively).

CONCLUSION: The Current work suggests that HLA-DQB1 alleles *030201, *0202, *0201, and genotypes 02/03, 02/02 may be susceptibility risk factors for development of T1D in Egyptian children, while the HLA-DQB1*060101 allele, and 03/06, 06/06 genotypes may be protective factors. HLA-DQB1 alleles and genotypes do not contribute to microalbuminuria or grade of diabetic control.

Newborn HLA-DR,DQ genotype screening: age- and ethnicity-specific type 1 diabetes risk estimates

OBJECTIVE

Certain human leukocyte antigen (HLA)-DR,DQ genotypes have been associated with type 1 diabetes mellitus (T1DM) risk, although it is unknown whether the association is due to alleles, haplotypes, genotypes, the formation of heterodimers, or all of the above. To characterize the role of the HLA-DR,DQ genotype and ethnicity on the onset age of T1DM, we analyzed these factors in patients with T1DM and the general population.

METHODS

One thousand three hundred twenty-two well-characterized patients with T1DM were compared with 3339 children from the general population of Denver, Colorado, USA. Because of the extensive available data across age and ethnic groups, this study population is unique.

RESULTS

The HLA-DR3/4,DQB1*0302, DRX/4,DQB1*0302 (where X=1, 4, 8, and 9), and HLA--DR3/3 genotypes were associated with T1DM, supporting previous research. Additionally, the DR3/9 genotype showed a positive association with T1DM, which has not previously been described in Caucasian populations. The HLA-DR3/4*0302 genotype was most strongly associated with T1DM in diabetic individuals with the youngest onset age. Genotype frequencies were similar between Hispanics and non-Hispanic whites, except for the DR3/3 genotype, which was more likely to be found in non-Hispanic whites.

CONCLUSIONS

These results indicate that there are multiple alleles and genotypes associated with T1DM and that the risk associated with different genetic markers depends on the age of disease onset, suggesting that some markers may be involved in more rapid disease progression.

The rare HLA-DQA1*03-DQB1*02 haplotype confers susceptibility to type 1 diabetes in whites and is preferentially associated with early clinical disease onset in male subjects

The heterozygous combination of DQA1*03-DQB1*0302 (DQ8) and DQA1*05-DQB1*0201 (DQ2) confers the highest known HLA-DQ-linked risk for type 1 diabetes, suggesting a role for transcomplementation. The trans-heterodimer encoded by DQA1*03 and DQB1*02 is also rarely observed in cis in whites. Islet antibody-positive diabetic patients (P; n = 2,238) and control subjects (C; n = 2,223) of white descent were genotyped by a HLA-DQA1-DQB1 dot-blot method. The presence of the DQA1*03-DQB1*02 haplotype was observed in 22 patients (1%) versus 6 controls (0.3%) (odds ratio [OR] = 3.7, p = 0.005). It was more prevalent in whites of Northern African descent, but both in European (n = 3,813) and in Northern African whites (n = 648), the DQA1*03-DQB1*02 haplotype tended to be associated with diabetes (respectively, P 0.3% vs. C 0.03%, OR = 12.2, p = 0.005; and P 2.1% vs. C 0.6%, OR = 3.8, p = 0.03). DRB1 typing revealed that DQA1*03-DQB1*02 is usually associated with the DRB1*0405 risk allele in European patients and with DRB1*0405, DRB1*07 and DRB1*09 in Northern African whites. Like in DQ2/DQ8-positive patients, the presence of DQA1*03-DQB1*02 is preferentially associated with younger age at clinical onset than in other genotypes, but unlike in subjects carrying DQ2/DQ8, earlier clinical manifestation was mostly restricted to male subjects, often carrying DR3 and/or DQB1*02 on the other chromosome. These results are compatible with an effect of cis-encoded heterodimers or with previously suggested interactions of X-linked genetic factors with (DR3-)DQB1*02 haplotypes.

HLA haplotypes associated with type 1 diabetes mellitus in North Indian children

Human leukocyte antigen (HLA) encoded susceptibility to develop type 1 diabetes mellitus (T1DM) has been investigated in children from North India. The results revealed significantly increased prevalence of HLA-A26, -B8, and -B50 among patients and strong positive association of the disease with DRB1*0301 (82.1% vs 13.9%, chi2=71.3, odds ratio [OR]=28.3) and a negative association with DRB1*02 (chi2=12.2, PF=38.5). HLA-DQB1*0201 occurred in 96.4% of the patients, whereas the heterodimer DQA1*0501-DQB1*0201 was present in 82.1% of patients (60.7% in single dose and 21.4% in double dose) and revealed significant deviation from the healthy controls (chi2=74.1, pc=6.0E-10). In addition to DRB1*03, positive association was also observed with DRB1*09 (14.3% vs 1.3%, chi2=13.4) and DRB1*04 (39.3% vs 15.6%, chi2=8.39). No HLA association was observed in relation to residual pancreatic beta-cell function or associated thyroid autoimmunity. Family analysis revealed involvement of multiple DR3+ve haplotypes with T1DM in North Indian children with A26-B8-DRB1*03 (25% vs 3.5%, chi2=16.9, p=3.96E-05) and Ax-B50-DRB1*03 (25% vs 0.7%, chi2=44.7, p=9.88E-11) being the most frequent haplotypes encountered among patients. The classical Caucasian haplotype A1-B8-DRB1*03 was infrequent (7.2%) among the diabetic children. The study highlights the race specificity of HLA association and disease associated HLA haplotypes in T1DM among North Indian children.

Clinical characteristics, GAD antibody (GADA) and change of C-peptide in Korean young age of onset diabetic patients

AIMS

To investigate the association of clinical and immunological markers with diabetes classification in newly diagnosed young diabetic patients at disease onset.

METHODS

Eighty-two diabetic patients recruited within 1 year of onset (mean age 23.0 +/- 7.1, M:F = 46:36) were divided into three groups, namely: a low fasting C-peptide (FC) level at baseline group (the low FC group (n = 14, FC < 0.18 nmol/l)), an intermediate FC group (n = 29, 0.18 nmol/l < or = FC < 0.37 nmol/l), and a high FC group (n = 39, 0.37 nmol/l < or = FC). Patients were reclassified at follow-up (mean follow-up period 3.7 +/- 1.4 years) in the same manner as described above into low FC group (n = 31), intermediate FC group (n = 20), and high FC group (n = 31). The clinical characteristics and prevalence of GADA were compared.

RESULTS

Patients in the high FC group at baseline had a higher body mass index (BMI), a higher frequency of a family history of diabetes, a higher meal-stimulated C-peptide increment, a lower frequency of ketonuria, a lower frequency of history of diabetic ketoacidosis, and a lower frequency of insulin therapy at diagnosis than those in the low and intermediate FC groups at baseline. Insulin secretory capacity, which was represented by fasting C-peptide, was affected by BMI at diagnosis and the presence of GADA. All the patients of the low FC group on follow-up were finally classified as having Type 1 diabetes; moreover, the factors that determined the type of diabetes were lower BMI at onset, GADA positivity, insulin therapy, lower fasting C-peptide level and lower meal-stimulated C-peptide increment at initial admission.

CONCLUSIONS

Our study suggests that follow-up involving C-peptide and GADA measurements in combination with clinical characteristics is useful for discriminating between the types of diabetes in these groups.

Genetic risk and protective factors for idiopathic inflammatory myopathy in Koreans and American whites: a tale of two loci

OBJECTIVE

To better understand genetic contributions to autoimmunity, immunogenetic markers were studied in two racially discrete and geographically isolated populations of patients with idiopathic inflammatory myopathy (IIM).

METHODS

Clinical characteristics, as well as clinical and autoantibody subsets, were defined in 151 American white patients and 50 Korean patients with IIM. HLA-DRB1 and DQA1 genotyping was performed on patients and racially matched controls by standard molecular techniques. Gm allotypes and phenotypes were determined by the hemagglutination-inhibition method.

RESULTS

HLA-DRB1*0301, the linked allele DQA1*0501, and DRB1 alleles sharing the first hypervariable region motif 9EYSTS13 were major genetic risk factors for the development of myositis in whites (corrected P [Pcorr] < 0.0004, odds ratio [OR] 11.2, 4.5, and 3.1, respectively, for each factor versus controls). Although both the white and Korean patients had a similar distribution of clinical characteristics, autoantibody profiles, and clinical groups, no HLA-DRB1 nor DQA1 allele or motif was found to be a risk factor for IIM in the Korean patients. However, DRB1*14 was a protective factor in Korean patients without myositis-specific autoantibodies (Pcorr = 0.004, OR 0.046). In addition, although no Gm phenotype or allotype was identified as a risk factor in whites, Gm 21 was a protective factor for the development of IIM in Koreans (Pcorr = 0.024, OR 0.3).

CONCLUSION

Although myositis patients in the US and Korea share similar clinical and serologic features, the immune response genes predisposing to and protecting from myositis in each of these ethnic groups differ at two chromosomal loci. These data suggest that multiple genetic loci should be studied to identify risk and protective factors for some autoimmune diseases in various ethnic populations.