High-resolution mapping identifies HLA class II associations with multifocal motor neuropathy.

OBJECTIVE: To gain further insight in the immunopathology underlying multifocal motor neuropathy (MMN) by exploring the association between MMN and the human leukocyte antigen (HLA) class II DRB1, DQB1, and DQA loci in depth and by correlating associated haplotypes to detailed clinical and anti-ganglioside antibody data. METHODS: We performed high-resolution HLA-class II typing for the DRB1, DQB1, and DQA1 loci in 126 well-characterized MMN patients and assessed disease associations with haplotypes. We used a cohort of 1305 random individuals as a reference for haplotype distribution in the Dutch population. RESULTS: The DRB1*15:01-DQB1*06:02 haplotype (OR 1.6 [95% CI 1.1-2.2], p < 0.05) and the DRB1*12:01-DQB1*03:01 haplotype (OR 2.7 [95% CI 1.2-5.5], p < 0.05) were more frequent in patients with MMN than in controls. These haplotypes were not associated with disease course, response to treatment or anti-ganglioside antibodies. CONCLUSIONS: MMN is associated with the DRB1*15:01-DQB1*06:02 and DRB1*12:01-DQB1*03:01 haplotypes. These HLA molecules or gene variants in their immediate vicinity may promote the specific inflammatory processes underlying MMN.

HLA associations in narcolepsy type 1 persist after the 2009 H1N1 pandemic.

We aimed to compare HLA-DQB1-associations in narcolepsy type 1 (NT1) patients with disease onset before and after the 2009 H1N1 pandemic in a large Dutch cohort. 525 NT1 patients and 1272 HLA-DQB1*06:02-positive healthy controls were included. Because of the discussion that has arisen on the existence of sporadic and post-H1N1 NT1, HLA-DQB1-associations in pre- and post-H1N1 NT1 patients were compared. The associations between HLA-DQB1 alleles and NT1 were not significantly different between pre- and post-H1N1 NT1 patients. Both HLA-DQB1-associations with pre- and -post H1N1 NT1 reported in recent smaller studies were replicated. Our findings combine the results of studies in pre- and post-H1N1 NT1 and argue against considering post-H1N1 NT1 as a different entity.

Paternal HLA-C is a risk factor in unexplained recurrent miscarriage.

PROBLEM: HLA-C is the only classical HLA-I antigen expressed on trophoblast. We hypothesized that the alloimmune response to paternal HLA-C plays a role in unexplained recurrent miscarriage. METHOD OF STUDY: In a case-control design, we included 100 women with at least three unexplained consecutive miscarriages along with their partners and children. For the first control group, we included 90 women with an uneventful singleton pregnancy without pregnancy complications in their history along with their children. The second control group consisted of 425 families. HLA-C*07 and HLA-C*17 frequencies, which are the most immunogenic HLA-C antigens, along with HLA-C mismatches, and the presence of specific HLA antibodies in the mother were determined. RESULTS: HLA-C and HLA-C*07 mismatches were significantly increased in couples with recurrent miscarriage compared to control subjects (P = .016, P = .008, respectively). The incidence of child-specific HLA-C*07/HLA-C*17 antibodies was increased in women with recurrent miscarriage (P = .007). CONCLUSION: The results show that HLA-C incompatibility between couples is significantly associated with unexplained recurrent miscarriage.

HLA dosage effect in narcolepsy with cataplexy.

Narcolepsy with cataplexy is a sleep disorder caused by the loss of hypocretin-producing neurons in the hypothalamus. It is tightly associated with a specific human leukocyte antigen (HLA)-allele: HLA-DQB1*06:02. Based on this, an autoimmune process has been hypothesized. A functional HLA-DQ molecule consists of a DQα and a DQß chain. HLA-DQB1*06:02 (DQß) has a strong preference for binding to HLA-DQA1*01:02 (DQα), and together they form the functional DQ0602 dimer. A dosage effect would be expected if the HLA-DQ0602 dimer itself is directly involved in the aetiology. An increased expression of the HLA-DQ0602 dimer is expected in individuals homozygous for HLA-DQB1*06:02-DQA1*01:02, but is also hypothesized in individuals heterozygous for HLA-DQB1*06:02 and homozygous for HLA-DQA1*01:02. To study the impact of the expression of the HLA-DQ0602 dimer on narcolepsy susceptibility, 248 Dutch narcolepsy patients and 1272 Dutch control subjects, all of them positive for DQB1*06:02 (heterozygous and homozygous), were HLA-genotyped with attention not only to DQB1 but also to DQA1*01:02. DQB1*06:02-DQA1*01:02 homozygosity was significantly more often seen in patients compared to controls (O.R. 2.29) confirming previous observations. More importantly, a significantly higher prevalence of homozygosity for DQA1*01:02 was found in HLA-DQB1*06:02 heterozygous patients compared to controls (O.R. 2.37, p < 0.001). The latter finding clearly supports a direct role of the HLA-DQ molecule in the development of disease.

Anti-CarP antibodies in two large cohorts of patients with rheumatoid arthritis and their relationship to genetic risk factors, cigarette smoking and other autoantibodies.

INTRODUCTION: In rheumatoid arthritis (RA), several genetic risk factors and smoking are strongly associated with the presence of anticitrullinated protein antibodies (ACPA), while much less is known about risk factors for ACPA-negative RA. Antibodies against carbamylated proteins (anti-CarP) have been described in both ACPA-positive and ACPA-negative RA patients. In this study, we have analysed the relationships among anti-CarP antibodies, ACPA, genetic risk factors (HLA-DRB1 alleles and PTPN22) and smoking in RA. METHODS: Presence of antibodies to carbamylated fetal calf serum (CarP-FCS) and fibrinogen (CarP-Fib) was determined by inhouse ELISAs among RA cases in the Leiden Early Arthritis Clinic (n=846) and in the Swedish Epidemiological Investigation of Rheumatoid Arthritis (n=1985) cohorts. ORs for associations with different HLA-DRB1 alleles, PTPN22 genotypes and smoking were calculated separately for each cohort as well as in meta-analysis in RA subsets defined by the presence/absence of anti-CarP and anticyclic citrullinated peptide (anti-CCP) antibodies. RESULTS: In both cohorts, anti-CarP antibody positivity was mainly detected in the anti-CCP-positive population (49%-73%), but also in the anti-CCP-negative population (8%-14%). No associations between anti-CarP antibodies and HLA-DRB1 shared epitope alleles could be identified, while there were data to support an association between anti-CarP-FCS and HLA-DRB1*03. Further analyses did not reveal any specific associations of anti-CarP antibodies with other HLA-DRB1 alleles, PTPN22 genotypes or smoking. CONCLUSIONS: Anti-CarP antibodies were present in both ACPA-positive and ACPA-negative RA. There were no significant associations among anti-CarP antibodies and HLA-DRB1 alleles, PTPN22 or smoking. These data suggest that different biological mechanisms may underlie anti-CarP versus anti-CCP antibody formation.

DQB1 locus alone explains most of the risk and protection in narcolepsy with cataplexy in Europe.

STUDY OBJECTIVE: Prior research has identified five common genetic variants associated with narcolepsy with cataplexy in Caucasian patients. To replicate and/or extend these findings, we have tested HLA-DQB1, the previously identified 5 variants, and 10 other potential variants in a large European sample of narcolepsy with cataplexy subjects. DESIGN: Retrospective case-control study. SETTING: A recent study showed that over 76% of significant genome-wide association variants lie within DNase I hypersensitive sites (DHSs). From our previous GWAS, we identified 30 single nucleotide polymorphisms (SNPs) with P < 10(-4) mapping to DHSs. Ten SNPs tagging these sites, HLADQB1, and all previously reported SNPs significantly associated with narcolepsy were tested for replication. PATIENTS AND PARTICIPANTS: For GWAS, 1,261 narcolepsy patients and 1,422 HLA-DQB1*06:02-matched controls were included. For HLA study, 1,218 patients and 3,541 controls were included. MEASUREMENTS AND RESULTS: None of the top variants within DHSs were replicated. Out of the five previously reported SNPs, only rs2858884 within the HLA region (P < 2x10(-9)) and rs1154155 within the TRA locus (P < 2x10(-8)) replicated. DQB1 typing confirmed that DQB1*06:02 confers an extraordinary risk (odds ratio 251). Four protective alleles (DQB1*06:03, odds ratio 0.17, DQB1*05:01, odds ratio 0.56, DQB1*06:09 odds ratio 0.21, DQB1*02 odds ratio 0.76) were also identified. CONCLUSION: An overwhelming portion of genetic risk for narcolepsy with cataplexy is found at DQB1 locus. Since DQB1*06:02 positive subjects are at 251-fold increase in risk for narcolepsy, and all recent cases of narcolepsy after H1N1 vaccination are positive for this allele, DQB1 genotyping may be relevant to public health policy.

Epistasis between two HLA antigens defines a subset of individuals at a very high risk for ankylosing spondylitis.

OBJECTIVES: Susceptibility to spondyloarthritis (SpA) is largely genetically determined. To understand increasingly complex genetic associations, one approach is to study epistasis or genetic interactions. Several associations between HLA antigens and SpA including HLA-B27 have been reported. In this study, we investigated epistasis between common HLA class I risk antigens in ankylosing spondylitis (AS), the most typical form of SpA. METHODS: In 154 patients with AS and 5584 controls, HLA class I antigens were analysed for association with AS. Biological interaction was analysed by investigating whether the effects of the risk factors combined departed from additivity. RESULTS: Apart from the association with HLA-B27, we found an association between HLA-B60 and AS (OR 1.8; 95% CI 1.2 to 2.8). This was confirmed in a meta-analysis (OR 2.2; CI 1.8 to 2.8). While 18.2% of AS patients had both HLA-B27 and HLA-B60, this combination was found in only 0.4% of controls. Using AS patients without HLA-B27 and HLA-B60 as a reference, the relative risk (RR) for disease in HLA-B27-/HLA-B60+ patients was 1.2 (95% CI 0.3 to 4.1). For HLA-B27+/HLA-B60- the RR was 69 (95% CI 40 to 111) but increased to 342 (95% CI 147 to 708) in HLA-B27+/HLA-B60+ patients. For the interaction, the relative excess risk due to interaction was 251, the attributable proportion was 0.8 and the synergy index was 4.7. The interaction was confirmed in an independent cohort. CONCLUSIONS: There is a strong epistatic interaction between HLA-B60 and HLA-B27 in AS susceptibility. As a result, individuals with the HLA-B27+/HLA-B60+ genotype are at a very high risk of developing AS.

Genetic HLA associations in complex regional pain syndrome with and without dystonia.

UNLABELLED: We previously showed evidence for a genetic association of the human leukocyte antigen (HLA) system and complex regional pain syndrome (CRPS) with dystonia. Involvement of the HLA system suggests that CRPS has a genetic component with perturbed regulation of inflammation and neuroplasticity as possible disease mechanisms. However, it is at present unclear whether the observed association with HLA-B62 and HLA-DQ8 in CRPS patients with dystonia also holds true for patients without dystonia. Therefore, we tested the possible association with HLA-B62 and HLA-DQ8 in a clinically homogeneous group of 131 CRPS patients without dystonia. In addition, we investigated the possible association with other alleles of the HLA-A, HLA-B, HLA-C, HLA-DR, and HLA-DQ loci. We showed an increased prevalence of HLA-DQ8 (molecularly typed as HLA-DQB1*03:02; OR = 1.65 [95% CI 1.12-2.42], P = .014) in CRPS without dystonia, whereas no association was observed for HLA-B62 (molecularly typed as HLA-B*15:01; OR = 1.22 [95% CI .78-1.92], P = .458). Our data suggest that CRPS with and CRPS without dystonia may be genetically different, but overlapping, disease entities because only HLA-DQ8 is associated with both. The findings also indicate that distinct biological pathways may play a role in both CRPS subtypes. PERSPECTIVE: This study is the first to replicate a specific HLA region conferring genetic risk for the development of CRPS. Moreover, associations of HLA-DQ8 with both CRPS with and CRPS without dystonia, and HLA-B62 only with CRPS with dystonia, suggest that these disease entities may be genetically different, but overlapping.

Anorexia nervosa and the Val158Met polymorphism of the COMT gene: meta-analysis and new data.

OBJECTIVES: This study aimed to test the association between the Val158Met polymorphism (rs4680) of the catechol-O-methyl transferase gene and anorexia nervosa (AN). METHODS: First, an association study on two cohorts (306 cases and 1009 controls from Utrecht, and 174 cases and 466 controls from Leiden/NTR) was performed. Subsequently, the results were integrated into a meta-analysis, together with all the case-control and family-based studies, which were testing the same hypothesis and were available in the literature. Altogether, eight studies (11 datasets) were included in this meta-analysis, with a total of 2021 cases, 2848 controls, and 89 informative (heterozygous) trios. RESULTS: The present association studies found no association between AN and rs4680 when testing the allelic contrast [Utrecht odds ratio (OR)=1.14, P=0.14; Leiden OR=1.02, P=0.85]. There was an indication of an association under the dominant model of genetic effect in the Utrecht cohort (for the Met allele, OR=1.42, P=0.03). Nevertheless, the meta-analyses of both the allelic contrast and the dominant effect were nonsignificant (the allelic pooled OR=1.03, P=0.42 and the dominant pooled OR=1.1, P=0.18). The meta-analyses were performed under the fixed-effect model and there was no significant heterogeneity among the effect sizes. CONCLUSION: Meta-analytically combined evidence from the present genotypings and the literature search shows that the effect sizes are homogeneous across studies and that rs4680 is not associated with AN.

Composition of human skin microbiota affects attractiveness to malaria mosquitoes.

The African malaria mosquito Anopheles gambiae sensu stricto continues to play an important role in malaria transmission, which is aggravated by its high degree of anthropophily, making it among the foremost vectors of this disease. In the current study we set out to unravel the strong association between this mosquito species and human beings, as it is determined by odorant cues derived from the human skin. Microbial communities on the skin play key roles in the production of human body odour. We demonstrate that the composition of the skin microbiota affects the degree of attractiveness of human beings to this mosquito species. Bacterial plate counts and 16S rRNA sequencing revealed that individuals that are highly attractive to An. gambiae s.s. have a significantly higher abundance, but lower diversity of bacteria on their skin than individuals that are poorly attractive. Bacterial genera that are correlated with the relative degree of attractiveness to mosquitoes were identified. The discovery of the connection between skin microbial populations and attractiveness to mosquitoes may lead to the development of new mosquito attractants and personalized methods for protection against vectors of malaria and other infectious diseases.

Genome-wide association study identifies new HLA class II haplotypes strongly protective against narcolepsy.

Narcolepsy is a rare sleep disorder with the strongest human leukocyte antigen (HLA) association ever reported. Since the associated HLA-DRB1*1501-DQB1*0602 haplotype is common in the general population (15-25%), it has been suggested that it is almost necessary but not sufficient for developing narcolepsy. To further define the genetic basis of narcolepsy risk, we performed a genome-wide association study (GWAS) in 562 European individuals with narcolepsy (cases) and 702 ethnically matched controls, with independent replication in 370 cases and 495 controls, all heterozygous for DRB1*1501-DQB1*0602. We found association with a protective variant near HLA-DQA2 (rs2858884; P < 3 x 10(-8)). Further analysis revealed that rs2858884 is strongly linked to DRB1*03-DQB1*02 (P < 4 x 10(-43)) and DRB1*1301-DQB1*0603 (P < 3 x 10(-7)). Cases almost never carried a trans DRB1*1301-DQB1*0603 haplotype (odds ratio = 0.02; P < 6 x 10(-14)). This unexpected protective HLA haplotype suggests a virtually causal involvement of the HLA region in narcolepsy susceptibility.

Protection against anti-citrullinated protein antibody-positive rheumatoid arthritis is predominantly associated with HLA-DRB1*1301: a meta-analysis of HLA-DRB1 associations with anti-citrullinated protein antibody-positive and anti-citrullinated protein antibody-negative rheumatoid arthritis in four European populations.

OBJECTIVE: The protective effect of HLA-DRB1 alleles on the development of rheumatoid arthritis (RA) is poorly understood. The aim of this study was to perform a meta-analysis of 4 European populations to investigate which HLA-DRB1 alleles are associated with protection in anti-citrullinated protein antibody (ACPA)-positive RA and ACPA-negative RA. METHODS: Data for >2,800 patients and >3,000 control subjects for whom information on HLA-DRB1 typing and ACPA status was available were collected from 4 European countries: Norway, Sweden, The Netherlands, and Spain. The odds ratios (ORs) and 95% confidence intervals (95% CIs) associated with the different HLA-DRB1 alleles were analyzed in a combined meta-analysis focused on protective alleles and classifications. The analysis of ACPA-positive RA was stratified for the shared epitope (SE) alleles, to correct for skewing due to this association. RESULTS: In ACPA-positive RA, the only alleles that conveyed protection after stratification for SE were HLA-DRB1*13 alleles (OR 0.54 [95% CI 0.38-0.77]). The protective effect of the allele classifications based on the DERAA and D70 sequences was no longer present after exclusion of DRB1*13 (for D70, OR 0.97 [95% CI 0.75-1.25]), indicating that DRB1*13, rather than the DERAA or D70 sequence as such, is associated with protection. Among the DRB1*13 alleles, only DRB1*1301 was associated with protection (OR 0.24 [95% CI 0.09-0.59]). Protection appeared to follow a north-to-south gradient, with the strongest association in northern European countries. In ACPA-negative RA, there were no robust associations with HLA-DRB1 alleles. CONCLUSION: Our data do not support any of the classifications of protective alleles and indicate that protection against ACPA-positive RA is predominantly associated with HLA-DRB1*1301.

HLA-B62 and HLA-DQ8 are associated with Complex Regional Pain Syndrome with fixed dystonia.

Complex Regional Pain Syndrome (CRPS) is clinically characterized by pain in combination with sensory, autonomic, and motor symptoms that may include weakness, tremor, myoclonus and dystonia of the affected limb(s). The syndrome is multifactorial in origin and mostly attributed to tissue injury. There is some evidence that the human leukocyte antigen (HLA) system plays a role in the pathophysiology of CRPS, but previous studies lacked power. Here we performed the most extensive study investigating the contribution of HLA alleles (i.e. HLA-A, HLA-B, HLA-DRB1, and HLA-DQB1) in 150 CRPS patients who also had fixed dystonia. HLA-B62 (OR=2.05 [95% CI 1.41-2.99], P=0.0005) and HLA-DQ8 (OR=1.75 [95% CI 1.20-2.57], P=0.005) were found significantly associated with CRPS and dystonia. The association remained significant after correction (HLA-B62 P(corrected) [P(c)] = 0.02 and HLA-DQ8 P(c)=0.04). The involvement of HLA-B62 and HLA-DQ8 in CRPS with dystonia may indicate that these HLA loci are implicated in the susceptibility or expression of the disease.

Confirmation of STAT4, IL2/IL21, and CTLA4 polymorphisms in rheumatoid arthritis.

OBJECTIVE: Recent advances have led to novel identification of genetic polymorphisms that are associated with susceptibility to rheumatoid arthritis (RA). Currently, 5 loci (HLA, PTPN22, TRAF1/C5, TNFAIP3, and STAT4) have been consistently reported, whereas others have been observed less systematically. The aim of the present study was to independently replicate 3 recently described RA susceptibility loci, STAT4, IL2/IL21, and CTLA4, in a large Dutch case-control cohort, and to perform a meta-analysis of all published studies to date and investigate the relevance of the findings in clinically well-defined subgroups of RA patients with or without autoantibodies. METHODS: The STAT4, IL2/IL21, and CTLA4 gene polymorphisms (rs7574865, rs6822844, and rs3087243, respectively) were genotyped in 877 RA patients and 866 healthy individuals. A meta-analysis of all published studies of disease association with these polymorphisms was performed using the Mantel-Haenszel fixed-effects method. RESULTS: An association of STAT4, IL2/IL21, and CTLA4 with RA was detected in Dutch patients (odds ratio [OR] 1.19 [P=0.031], OR 0.84 [P=0.051], and OR 0.87 [P=0.041], respectively). Results from the meta-analysis confirmed an association of all 3 polymorphisms with RA in Caucasians (OR 1.24 [P=1.66x10(-11)], OR 0.78 [P=5.6x10(-5)], and OR 0.91 [P=1.8x10(-3)], respectively). The meta-analysis also revealed that STAT4 predisposed to disease development equally in patients with autoantibodies and those without autoantibodies, and that CTLA4 enhanced the development of anti-citrullinated protein antibody (ACPA)-positive RA as compared with ACPA-negative RA. CONCLUSION: Our results replicate and firmly establish the association of STAT4 and CTLA4 with RA and provide highly suggestive evidence for IL2/IL21 loci as a risk factor for RA. Given the strong statistical power of our meta-analysis to confirm a true-positive association, these findings provide considerable support for the involvement of CTLA4 in distinct subsets of RA patients.

Evidence for natural killer cell-mediated protection from metastasis formation in uveal melanoma patients.

PURPOSE: In uveal melanoma, low human leukocyte antigen (HLA) class I expression on primary tumors is associated with a decreased risk of metastasis. Consequently, it has been suggested that natural killer (NK) cells, which detect decreased expression of HLA class I, are involved in the immune control of metastases. In this study, three novel lines of evidence were identified that support a role for NK cells. METHODS: Uveal melanoma cell lines were used to determine the expression of NK cell receptor ligands (MICA, MICB, ULBP1-3, CD112, CD155, and HLA class I) and to examine sensitivity to lysis by human NK cell lines. Because interactions between polymorphic killer immunoglobulin receptors (KIRs) and HLA regulate NK cell function, KIR and HLA genotyping was performed on 154 patients with uveal melanoma and 222 healthy control subjects. RESULTS: First, all 11 uveal melanoma cell lines tested expressed ligands for activating as well as inhibitory NK cell receptors. Second, such cell lines were lysed efficiently by human NK cells in vitro. Finally, the HLA-C genotype was related to the risk of metastasis-related death in patients with uveal melanoma: The patients carrying HLA-C alleles encoding ligands for KIR2DL1 and KIR2DL2/3 (HLA-C group 1/group 2 heterozygous patients), both inhibitory NK receptors, had a longer metastasis-free survival than did those carrying HLA-C ligands for either KIR2DL1 (HLA-C group 2 homozygotes) or KIR2DL2/3 (HLA-C group 1 homozygotes). CONCLUSIONS: Together, the data support a role for NK cells in the prevention of uveal melanoma metastases.

Phenotypic variance in childhood coeliac disease and the HLA-DQ/DR dose effect.

OBJECTIVE: Coeliac disease (CD) is associated with HLA-DQ2 and DQ8. The clinical picture is variable and certain human leucocyte antigen (HLA) DQ/DR combinations have a higher relative risk (RR) for CD than others. Moreover, the HLA-DQ gene-dose effect has an impact on the strength of the gluten-specific T-cell response and thus may correlate with clinical presentation and severity of CD. The aim of this study was to determine the correlation between HLA-DQ/DR-based genotypes and the variation in phenotypes of the disease. MATERIAL AND METHODS: A total of 113 non-related Caucasian children clinically diagnosed with CD during the period 1980-2003 with a known HLA type were included in the study. Patients were divided into four categories according to amount of disease expression predisposing to HLA-DQ2 or HLA-DQ8 molecules and the known RR of their HLA-DR/DQ type for CD: high (DR3DQ2 homozygous and DR3DQ2/DR7DQ2), substantial (DR3DQ2/DR5DQ7 and DR5DQ7/DR7DQ2), moderate (DR3DQ2-DR4DQ8 and DR3DQ2/DR*DQ*) and low (DR7DQ2/DR*DQ*, DR4DQ8- DR*DQ* and DR*DQ*- DR*DQ*). The clinical data and HLA genotypes of these patients were compared. RESULTS: The 113 children were diagnosed with CD at a mean age of 4.6 years and boys were significantly older than girls when diagnosed (p=0.01). RR for having CD was highest for the high HLA-risk group (RR 8.1). With the exception of a greater frequency of abdominal distension and fewer non-gastrointestinal symptoms in the substantial HLA-risk group, there were no significant differences in clinical characteristics or degree of severity of the small-bowel histological findings between the children in the different HLA-risk groups. CONCLUSION: No correlation was found between disease severity and a double HLA-DQ2 gene dose.

Effective detection of human leukocyte antigen risk alleles in celiac disease using tag single nucleotide polymorphisms.

BACKGROUND: The HLA genes, located in the MHC region on chromosome 6p21.3, play an important role in many autoimmune disorders, such as celiac disease (CD), type 1 diabetes (T1D), rheumatoid arthritis, multiple sclerosis, psoriasis and others. Known HLA variants that confer risk to CD, for example, include DQA1*05/DQB1*02 (DQ2.5) and DQA1*03/DQB1*0302 (DQ8). To diagnose the majority of CD patients and to study disease susceptibility and progression, typing these strongly associated HLA risk factors is of utmost importance. However, current genotyping methods for HLA risk factors involve many reactions, and are complicated and expensive. We sought a simple experimental approach using tagging SNPs that predict the CD-associated HLA risk factors. METHODOLOGY: Our tagging approach exploits linkage disequilibrium between single nucleotide polymorphism (SNPs) and the CD-associated HLA risk factors DQ2.5 and DQ8 that indicate direct risk, and DQA1*0201/DQB1*0202 (DQ2.2) and DQA1*0505/DQB1*0301 (DQ7) that attribute to the risk of DQ2.5 to CD. To evaluate the predictive power of this approach, we performed an empirical comparison of the predicted DQ types, based on these six tag SNPs, with those executed with current validated laboratory typing methods of the HLA-DQA1 and -DQB1 genes in three large cohorts. The results were validated in three European celiac populations. CONCLUSION: Using this method, only six SNPs were needed to predict the risk types carried by >95% of CD patients. We determined that for this tagging approach the sensitivity was >0.991, specificity >0.996 and the predictive value >0.948. Our results show that this tag SNP method is very accurate and provides an excellent basis for population screening for CD. This method is broadly applicable in European populations.

The MYO9B gene is a strong risk factor for developing refractory celiac disease.

BACKGROUND & AIMS: Celiac disease (CD) is associated with HLA-DQ2 and HLA-DQ8 and has been linked to genetic variants in the MYO9B gene on chromosome 19. HLA-DQ2 homozygosity is associated with complications of CD such as refractory celiac disease type II (RCD II) and enteropathy-associated T-cell lymphoma (EATL). We investigated whether MYO9B also predisposes to RCD II and EATL. METHODS: Genotyping of MYO9B and molecular HLA-DQ2 typing were performed on 62 RCD II and EATL patients, 421 uncomplicated CD patients, and 1624 controls. RESULTS: One single nucleotide polymorphism in MYO9B showed a significantly different allele distribution in RCD II and EATL patients compared with controls (P = .00002). The rs7259292 T allele was significantly more frequent in RCD II and EATL patients compared with CD patients (P = .0003; odds ratio [OR], 3.61; 95% confidence interval [CI], 1.78-7.31). The frequency of the haplotype carrying the T allele of this single nucleotide polymorphism was significantly increased in RCD II and EATL patients (11%), compared with controls (2%) and CD patients (3%) (OR, 6.76; 95% CI, 3.40-13.46; P = 2.27E-09 and OR, 4.22; 95% CI, 1.95-9.11; P = .0001, respectively). Both MYO9B rs7259292 and HLA-DQ2 homozygosity increase the risk for RCD II and EATL to a similar extent when compared with uncomplicated CD patients (OR, 4.3; 95% CI, 1.9-9.8 and OR, 5.4; 95% CI, 3.0-9.6, respectively), but there was no evidence for any interaction between these 2 risk factors. CONCLUSIONS: We show that both MYO9B and HLA-DQ2 homozygosity might be involved in the prognosis of CD and the chance of developing RCD II and EATL.