The influence of age at onset and gender on the HLA-DQA1, DQB1 association in Chinese children with insulin dependent diabetes mellitus

Sex-specific differences in peripheral blood leukocyte transcriptional response to LPS are enriched for HLA region and X chromosome genes

Sex-specific differences in prevalence are well documented for many common, complex diseases, especially for immune-mediated diseases, yet the precise mechanisms through which factors associated with biological sex exert their effects throughout life are not well understood. We interrogated sex-specific transcriptional responses of peripheral blood leukocytes (PBLs) to innate immune stimulation by lipopolysaccharide (LPS) in 46 male and 66 female members of the Hutterite community, who practice a communal lifestyle. We identified 1217 autosomal and 54 X-linked genes with sex-specific responses to LPS, as well as 71 autosomal and one X-linked sex-specific expression quantitative trait loci (eQTLs). Despite a similar proportion of the 15 HLA genes responding to LPS compared to all expressed autosomal genes, there was a significant over-representation of genes with sex by treatment interactions among HLA genes. We also observed an enrichment of sex-specific differentially expressed genes in response to LPS for X-linked genes compared to autosomal genes, suggesting that HLA and X-linked genes may disproportionately contribute to sex disparities in risk for immune-mediated diseases.

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.

Balancing selection and heterogeneity across the classical human leukocyte antigen loci: a meta-analytic review of 497 population studies

This paper presents a meta-analysis of high-resolution human leukocyte antigen (HLA) allele frequency data describing 497 population samples. Most of the datasets were compiled from studies published in eight journals from 1990 to 2007; additional datasets came from the International Histocompatibility Workshops and from the AlleleFrequencies.net database. In all, these data represent approximately 66,800 individuals from throughout the world, providing an opportunity to observe trends that may not have been evident at the time the data were originally analyzed, especially with regard to the relative importance of balancing selection among the HLA loci. Population genetic measures of allele frequency distributions were summarized across populations by locus and geographic region. A role for balancing selection maintaining much of HLA variation was confirmed. Further, the breadth of this meta-analysis allowed the ranking of the HLA loci, with DQA1 and HLA-C showing the strongest balancing selection and DPB1 being compatible with neutrality. Comparisons of the allelic spectra reported by studies since 1990 indicate that most of the HLA alleles identified since 2000 are very-low-frequency alleles. The literature-based allele-count data, as well as maps summarizing the geographic distributions for each allele, are available online.

Studies of HLA associations in male and female patients with Guillain–Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)

HLA associations are found to differ with the gender of the patient in some autoimmune diseases. Here we have investigated whether there are gender-related HLA associations in Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), both of which occur more frequently in male patients than in females. In GBS, no particular HLA associations were noted, except for a slight negative association in both males and females for carriage of HLA-DR5. In CIDP, the gene frequency and the frequency of individuals positive for HLA-DR2 were greater in female patients than female controls, although this was statistically significant only for the gene frequency. Furthermore more female CIDP patients were homozygous for DR2, than male CIDP patients, or male or female controls and patients with GBS. This suggests that sex-related factors may interact with the risk associated with carriage of HLA-DR2 for development of CIDP.

The role of HLA class I gene variation in autoimmune diabetes

The use of DNA-based genetic typing has enabled the identification of type 1 diabetes mellitus (T1DM) susceptible and protective major histocompatibility complex (MHC) class II alleles and haplotypes. The application of this approach has also progressed to locate MHC class I alleles that contribute to the clinicopathology of T1DM. Recent studies have shown a widespread involvement of genes from the MHC class I gene region in the clinicopathology of T1DM. These genes are shown to be involved in contributing to progression from the preclinical stage of the disease, which is characterized by the occurrence of islet-specific antibodies, to clinical disease and also to the occurrence of autoimmunity. They can either contribute directly to disease development or indirectly in concert with other susceptible MHC class II alleles or haplotypes via linkage disequilibrium. Class I alleles may also be negatively associated with T1DM. These findings are useful for the development of future strategies in designing tolerogenic approaches for the prevention or even reversal of T1DM. In this article, the latest evidence for the different kinds of participation of HLA class I genes in the etiology of T1DM is reviewed. A meta-analysis which included existing association studies was also carried out in order to re-assess the relevance of class I genes in diabetes development. The analysis of an enlarged heterogeneous sample confirmed the involvement of previously detected serotypes in the etiology of T1DM, such as A24, B8 and B18, and revealed hitherto unknown associations with B60 and B62. The analysis points out that much of the conflicting results of previous association studies originate from inadequate sample sizes and accentuate the value of future investigations of larger samples for identifying linkage in multigenic diseases.

Comparison of nucleotide sequence of p2C region in diabetogenic and non-diabetogenic Coxsacie virus B5 isolates

Enteroviruses are environmental triggers in the pathogenesis of type 1 diabetes mellitus (DM). A sequence of six identical amino acids (PEVKEK) is shared by the 2C protein of Coxsackie virus B and the glutamic acid decarboxylase (GAD) molecules. Between 1995 and 2002, we investigated 22 Coxsackie virus B5 (CVB5) isolates from southern Taiwan. Four of these isolates were obtained from four new-onset type 1 DM patients with diabetic ketoacidosis. We compared a 300 nucleotide sequence in the 2C protein gene (p2C) in 24 CVB5 isolates (4 diabetogenic, 18 non-diabetogenic and 2 prototype). We found 0.3-10% nucleotide differences. In the four isolates from type 1 DM patients, there was only 2.4-3.4% nucleotide difference, and there was only 1.7-7.1% nucleotide difference between type 1 DM isolates and non-diabetogenic isolates. Comparison of the nucleotide sequence between prototype virus and 22 CVB5 isolates revealed 18.4-24.1% difference. Twenty-one CVB5 isolates from type 1 DM and non-type 1 DM patients contained the PEVKEK sequence, as shown by the p2C nucleotide sequence. Our data showed that the viral p2C sequence with homology with GAD is highly conserved in CVB5 isolates. There was no difference between diabetogenic and non-diabetogenic CVB5 isolates. All four type 1 DM patients had at least one of the genetic susceptibility alleles HLA-DR, DQA1, DQB1. Other genetic and autoimmune factors such as HLA genetic susceptibility and GAD may also play important roles in the pathogenesis in type 1 DM.

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.

Analysis of children with type 1 diabetes in Korea: high prevalence of specific anti-islet autoantibodies, immunogenetic similarities to Western populations with "unique" haplotypes, and lack of discrimination by aspartic acid at position 57 of DQB

This study analyzed the expression of anti-islet autoantibodies and HLA-DR and -DQ genotypes in Korean children with type 1 diabetes mellitus (T1DM). The positivity of the anti-ICA512, anti-GAD65, and anti-insulin autoantibodies in the newly onset T1DM patients (n = 15) was 66.7%, 86.7%, and 46.7%, respectively, and all of them had one or more of the autoantibodies. HLA analysis showed higher frequencies of HLA-DRB1*0301, *0405, *09012 and -DQB1*0201, *0401, *03032 alleles in T1DM patients compared to controls (P(c) < 0.05). Because HLA-DQB1*0401, *03032 alleles carry aspartic acid at position 57 of DQB, susceptibility to T1DM in Korean children was not related to the presence of aspartic acid at position 57 of DQB1 locus. We suggest this unique HLA-DR, -DQ allele distribution might be an important factor for the low incidence of T1DM in Korea, and the combined anti-islet autoantibody assays could be valuable screening markers for the early detection of T1DM in Korea.