HLA-DRB1, especially the shared epitope (SE), is strongly associated with rheumatoid arthritis (RA). However, recent studies have shown that SE is at most weakly associated with RA without anti-citrullinated peptide/protein antibody (ACPA). We have recently reported that ACPA-negative RA is associated with specific HLA-DRB1 alleles and diplotypes. Here, we attempted to detect genetically different subsets of ACPA-negative RA by classifying ACPA-negative RA patients into two groups based on their positivity for rheumatoid factor (RF). HLA-DRB1 genotyping data for totally 954 ACPA-negative RA patients and 2,008 healthy individuals in two independent sets were used. HLA-DRB1 allele and diplotype frequencies were compared among the ACPA-negative RF-positive RA patients, ACPA-negative RF-negative RA patients, and controls in each set. Combined results were also analyzed. A similar analysis was performed in 685 ACPA-positive RA patients classified according to their RF positivity. As a result, HLA-DRB1*04:05 and *09:01 showed strong associations with ACPA-negative RF-positive RA in the combined analysis (p = 8.8×10−6 and 0.0011, OR: 1.57 (1.28–1.91) and 1.37 (1.13–1.65), respectively). We also found that HLA-DR14 and the HLA-DR8 homozygote were associated with ACPA-negative RF-negative RA (p = 0.00022 and 0.00013, OR: 1.52 (1.21–1.89) and 3.08 (1.68–5.64), respectively). These association tendencies were found in each set. On the contrary, we could not detect any significant differences between ACPA-positive RA subsets. As a conclusion, ACPA-negative RA includes two genetically distinct subsets according to RF positivity in Japan, which display different associations with HLA-DRB1. ACPA-negative RF-positive RA is strongly associated with HLA-DRB1*04:05 and *09:01. ACPA-negative RF-negative RA is associated with DR14 and the HLA-DR8 homozygote.
To investigate the associations between HLA-DRB1 shared epitope (SE) alleles and rheumatoid arthritis in subsets of rheumatoid arthritis defined by autoantibodies in three Asian populations from Malaysia.
1,079 rheumatoid arthritis patients and 1,470 healthy controls were included in the study. Levels of antibodies to citrullinated proteins (ACPA) and rheumatoid factors were assessed and the PCR-SSO method was used for HLA-DRB1 genotyping.
The proportion of ACPA positivity among Malay, Chinese and Indian rheumatoid arthritis patients were 62.9%, 65.2% and 68.6%, respectively. An increased frequency of SE alleles was observed in ACPA-positive rheumatoid arthritis among the three Asian ethnic groups. HLA-DRB1*10 was highly associated with rheumatoid arthritis susceptibility in these Asian populations. HLA-DRB1*0405 was significantly associated with susceptibility to rheumatoid arthritis in Malays and Chinese, but not in Indians. HLA-DRB1*01 did not show any independent effect as a risk factor for rheumatoid arthritis in this study and HLA-DRB1*1202 was protective in Malays and Chinese. There was no association between SE alleles and ACPA- negative rheumatoid arthritis in any of the three Asian ethnic groups.
The HLA-DRB1 SE alleles increase the risk of ACPA-positive rheumatoid arthritis in all three Asian populations from Malaysia.
OBJECTIVE—To examine the association of HLA-DRB1 alleles with polymyalgia rheumatica (PMR) in a Mediterranean country and to explore the role of HLA-DRB1 genes in determining disease severity.
METHODS—A five year prospective follow up study of 92 consecutive PMR patients diagnosed by the secondary referral centre of rheumatology of Reggio Emilia, Italy was conducted. HLA-DRB1 alleles were determined in the 92 patients, in 29 DR4 positive rheumatoid arthritis (RA) patients, and in 148 controls from the same geographical area by polymerase chain reaction amplification and oligonucleotide hybridisation.
RESULTS—No significant differences were observed in the frequencies of HLA-DRB1 types and in the expression of HLA-DRB 70-74 shared motif between PMR and controls. The frequency of the patients with double dose of epitope was low and not significantly different in PMR and in controls. No significant differences in the distribution of HLA-DR4 subtypes were observed between DR4+ PMR, DR+ RA, and DR4+ controls. Results of the univariate analysis indicated that an erythrocyte sedimentation rate (ESR) at diagnosis > 72 mm 1st h, the presence of HLA-DR1, DR10, rheumatoid epitope, and the type of rheumatoid epitope were significant risk factors associated with relapse/recurrence. Cox proportional hazards modelling identified two variables that independently increased the risk of relapse/recurrence: ESR at diagnosis > 72 mm 1st h (RR=1.5) and type 2 (encoded by a non-DR4 allele) rheumatoid epitope (RR=2.7).
CONCLUSION—These data from a Mediterranean country showed no association of rheumatoid epitope with PMR in northern Italian patients. A high ESR at diagnosis and the presence of rheumatoid epitope encoded by a non-DR4 allele are independent valuable markers of disease severity.
Objectives: To elucidate the contribution of HLA-DR-DQ haplotypes and their genotypic combinations to susceptibility to rheumatoid arthritis, and to evaluate the various models for HLA associated risk for the disease in a series of Finnish patients.
Methods: 322 Finnish patients with rheumatoid arthritis were typed for common north European HLA-DR-DQ haplotypes and compared with a series of 1244 artificial family based control haplotypes.
Results: The association of the so called shared epitope (SE) haplotypes (DRB1*0401, *0404, *0408, and *01) with rheumatoid arthritis was confirmed. The DRB1*0401 haplotypes carried a far stronger risk for the disease than the (DRB1*01/10)-(DQA1*01)-DQB1*0501 haplotypes. Seven protective HLA haplotypes—(DRB1*15)-(DQA1*01)-DQB1*0602; (DRB1*08)-(DQA1*04)-DQB1*04; (DRB1*11/12)-DQA1*05-DQB1*0301; (DRB1*1301)-(DQA1*01)-DQB1*0603; (DRB1*1302)-(DQA1*01)-DQB1*0604; (DRB1*07)-DQA1*0201-DQB1*0303; and (DRB1*16)- (DQA1*01)-DQB1*0502—were identified. In accordance with the reshaped shared epitope hypothesis, all the protective DRB1 alleles in these haplotypes share either isoleucine at position 67 or aspartic acid at position 70 in their third hypervariable region motif. However, differences in the disease risk of haplotypes carrying the same DR but different DQ alleles were also found: (DRB1*07)-DQA1*0201-DQB1*0303 was protective, while (DRB1*07)-DQA1*0201-DQB1*02 was neutral. The same haplotypes carried different risks for rheumatoid arthritis depending on their combination in genotypes.
Conclusions: When assessing the influence of HLA genes on the susceptibility to rheumatoid arthritis, not only should the HLA-DR or -DQ alleles or haplotypes be unravelled but also the genotype. The effect of HLA class II region genes is more complicated than any of the existing hypotheses can explain.
To clarify the influence of the HLA‐DRB1 locus on the susceptibility to rheumatoid arthritis and the production of anti‐cyclic citrullinated peptide antibodies (anti‐CCP) in a Portuguese population.
Methods: 141 patients with rheumatoid arthritis fulfilling the American College of Rheumatology 1987 revised criteria for rheumatoid arthritis were compared with 150 healthy controls. Human leucocyte antigen (HLA)‐DRB1 locus genotyping was assessed by polymerase chain reaction reverse probing assays and sequence‐specific primers. Anti‐CCP antibodies were quantified by ELISA in patients with rheumatoid arthritis. Frequencies between groups were compared by the two‐sided Fisher's exact test and considered significant if p<0.05.
The HLA‐DRB1*04 and HLA‐DRB1*10 groups were highly associated with rheumatoid arthritis (p<0.001 and p = 0.031, respectively). High titres of anti‐CCP antibodies were largely associated with the presence of HLA‐DRB1*04/10.
The well‐recognised susceptibility alleles to rheumatoid arthritis, HLA‐DRB1*04, were associated with rheumatoid arthritis in Portuguese patients. The relatively rare DRB1*10 was also associated with rheumatoid arthritis, as was described previously in other southern European countries. Both groups were associated with high anti‐CCP titres, reinforcing its relevance to disease onset.
The purpose of this study was to investigate the association between HLA-DRB1 alleles with susceptibility to rheumatoid arthritis (RA) and production of antibodies against citrullinated proteins (ACPA) and rheumatoid factor (RF).
We studied 408 patients (235 with RA, 173 non-RA) and 269 controls. ACPA, RF and HLA-DR typing were determined.
We found an increased frequency of HLA DRB1 alleles with the shared epitope (SE) in ACPA-positive RA. Inversely, HLA DRB1 alleles encoding DERAA sequences were more frequent in controls than in ACPA-positive RA, and a similar trend was found for HLA DR3. However, these results could not be confirmed after stratification for the presence of the SE, probably due to the relatively low number of patients. These data may suggest that the presence of these alleles may confer a protective role for ACPA-positive RA. In RA patients we observed association between SE alleles and ACPA titers in a dose-dependent effect. The presence of HLA DR3 or DERAA-encoding alleles was associated with markedly reduced ACPA levels. No association between RF titers and HLA DR3 or DERAA-encoding alleles was found.
HLA DRB1 alleles with the SE are associated with production of ACPA. DERAA-encoding HLA-DR alleles and HLA DR3 may be protective for ACPA-positive RA.
Human leucocyte antigen (HLA) genes predict disease severity in psoriasis (HLA‐Cw6) and rheumatoid arthritis (shared epitope (SE)), but the situation is unclear for psoriatic arthritis (PsA).
To determine the association of the HLA‐Cw6 and HLA‐DRB1 gene with disease severity in a large UK cohort with PsA.
Genotyping of the HLA‐Cw and HLA‐DRB1 loci was undertaken in DNA samples from patients with PsA (n = 480). Stratification and regression analysis were used within the PsA cases to determine whether HLA‐Cw6, HLA‐DRB1 or the presence of the SE alleles predicted disease severity as measured by the Health Assessment Questionnaire score, the total number of damaged or involved joints adjusted for disease duration and disease‐modifying antirheumatic treatments.
HLA‐Cw6 was found to be in linkage disequilibrium with HLA‐DRB1*07 (r2 = 0.46). Patients with PsA who carried both HLA‐Cw6 and HLA‐DRB1*07 had fewer damaged or involved joints (41% fewer damaged (95% CI 23% to 55%, p = 0.02) and 31% fewer involved joints (95% CI 16% to 44%, p<0.001)) compared with those who carried neither HLA‐Cw6 nor HLA‐DRB1*07 alleles. Those who carried either HLA‐Cw6 or HLA‐DRB1*07 alleles alone had no evidence of a reduction in joint involvement. The SE, HLA‐DRB1*03 and HLA‐DRB1*04 alleles did not predict severity using these outcome measures.
Patients with PsA carrying both HLA‐Cw6 and HLA‐DRB1*07 alleles have a less severe course of arthritis. This suggests that a protective locus lies on a haplotype marked by these alleles. No association was detected with disease severity and SE status.
Rheumatoid arthritis (RA) is a complex polygenic disease of unknown etiology. HLA-DRB1 alleles encoding the shared epitope (SE) (RAA amino acid pattern in positions 72 to 74 of the third hypervariable region of the DRβ1 chain) are associated with RA susceptibility. A new classification of HLA-DRB1 SE alleles has been developed by Tezenas du Montcel and colleagues to refine the association between HLA-DRB1 and RA. In the present study, we used RA samples collected worldwide to investigate the relevance of this new HLA-DRB1 classification in terms of RA susceptibility across various Caucasoid and non-Caucasoid patients.
Eighteen subsamples were defined from a total number of 759 cases and 789 controls and grouped in 10 samples on the basis of their ethnic origin. HLA-DRB1 alleles were divided into five groups (S1, S2, S3D, S3P, and X) according to the new HLA-DRB1 allele classification. The whole analysis was performed by comparing carrier frequencies for the five HLA-DRB1 allele groups between RA patients and controls across the 10 Caucasoid and non-Caucasoid samples. The Mantel-Haenszel method of meta-analysis provided a global odds ratio (OR) estimate with 95% confidence interval (CI).
A positive association with RA susceptibility was found for S2 allele carriers (OR 2.15, 95% CI 1.54 to 3.00; p < 10-5) and S3P allele carriers (OR 2.74, 95% CI 2.01 to 3.74; p < 10-5). A negative association was found for S1 alleles (OR 0.60, 95% CI 0.48 to 0.76; p < 10-4) and X alleles (OR 0.58, 95% CI 0.39 to 0.84; p = 4 × 10-3). No significant association was highlighted for the S3D group of alleles (OR 0.89, 95% CI 0.69 to 1.14; p = 0.89). The complementary genotype analysis fit with the genotype risk hierarchy previously reported in Caucasoid RA patients.
So far, the present study is the first attempt to investigate the relevance of this new HLA-DRB1 classification in terms of RA susceptibility on both Caucasoid and non-Caucasoid samples. Our results support the hypothesis of a differential role played by different HLA-DRB1 allele groups in RA susceptibility across different ethnic backgrounds and confirm the interest of such an HLA-DRB1 classification in differentiating predisposing and protective alleles.
Psoriasis of early onset (type I; age of onset ⩽40 years) is associated with HLA-Cw*06 while the shared epitope (SE) is associated with rheumatoid arthritis susceptibility. Our aim was to investigate the role of HLA-Cw*06 and HLA-DRB1 genes (including SE) with psoriatic arthritis (PsA) susceptibility.
In a case–control association study, HLA-Cw*06 phenotype frequencies were compared between patients with PsA (n = 480), psoriasis alone (n = 611) and healthy controls (n = 166). Similarly, at the HLA-DRB1 locus, phenotype and SE frequencies were compared in patients with PsA (n = 480), early undifferentiated inflammatory arthritis alone (n = 1621) and healthy controls (n = 537).
The HLA-Cw*06 phenotype was associated with type I psoriasis (OR 6.9, 95% CI 4.4, 11.1, p = 2.2×10−21) and with patients with PsA having type I psoriasis (OR 5.0, 95% CI 3.2, 7.9, p = 4.39×10−13), but not with patients with PsA having type II psoriasis (age of onset >40 years). HLA-DRB1*07, in linkage disequilibrium with HLA-Cw*06, was also associated with patients with PsA having type I psoriasis (OR 2.7, 95% CI 2.1, 3.7, p<0.00001). HLA-DRB1*04 alleles and the SE were associated with undifferentiated inflammatory arthritis but not with PsA.
The SE is not a PsA susceptibility locus. HLA-Cw*06 and HLA-DRB1*07 are associated with patients with PsA having type I psoriasis, suggesting that the primary association is with age of onset of psoriasis. Patients with PsA having type I psoriasis, therefore, have a genetic background different to those with type II psoriasis, and adjustment for this is necessary in future studies that investigate the genetic susceptibility of PsA.
The aims of this study were to summarize results on the association of HLA-DRB1 with rheumatoid arthritis (RA) in Asians and to determine if the shared epitope (SE) hypothesis could explain the meta-analysis results. Among the papers published between January 1987 and July 2006 on RA susceptibility in Asian-Mongoloid populations (Korean, Japanese, Chinese, and Thai), 12 were selected for the meta-analysis. Mongoloid-Asian patients with RA had significantly higher frequencies of HLA-DRB1*0101, *0401, *0410, and *1001 than controls (OR 1.5-2.1, p<0.05 for association). When analyses were restricted to more ethnically homogeneous populations, HLA-DRB1*0405 showed a significant susceptibility to RA in Koreans (OR 5.65, 95% CI 4.32-7.39), whereas the HLA-DRB1*0301, *0403, *0406, *0701, *1301, and *1405 alleles showed protective association with RA (OR 0.32-0.70, p<0.05 for association). In conclusion, it was found that HLA-DRB1 *0101, *0401, *0405, *0410, and *1001 are susceptible, while HLA-DRB1*0301, *0403, *0406, *0701, *1301, and *1405 are protective in Asian-Mongoloids. All the RA-associated alleles except DRB1*0301 could be explained by the structural model supporting the SE hypothesis that RA susceptibility is determined by the combination of amino acid residues at HLA-DR β71 and β74, not by β71 alone.
Arthritis, Rheumatoid; Genetics; Epitopes; HLA-DRB1; Meta-analysis; Asian Continental Ancestry Group
OBJECTIVE—To study HLA class II association in reactive arthritis.
METHODS—63 patients with reactive arth-ritis and 46 with rheumatoid arthritis were included in the study. HLA-DR alleles were determined by using a sequence specific PCR method. Oligonucleotide hybridisation was used for definition of DRB1*04 subtypes and DQB1 alleles. HLA-B27 was determined by standard microcytotoxity test or by PCR. HLA-B27 subtyping was made by sequencing.
RESULTS—46 (73%) of 63 patients with reactive arthritis were HLA-B27 positive and 24 (38%) were HLA-DRB1*04 positive. When haplotypes were inferred according to the known associations between DRB1 and DQB1 alleles, the frequency of DRB1*04-DQB1*0301 haplotype was found to be 13% (12/92) in HLA-B27 positive reactive arthritis patients, in contrast to 0% in HLA-B27 negative reactive arthritis (P = 0.04) and 1% in random controls (P = 0.0009). However, this combination was also found in 5% of 84 HLA-B27 positive control haplotypes, showing a linkage disequilibrium between B27 and this particular class II haplotype. HLA-DRB1*0408 subtype was found in 8/24 (33%) of the HLA-DRB1*04 alleles in patients with reactive arthritis, accounting for most DQB1*0301 haplotypes, but only in 5/55 (9%) of the DRB1*04 alleles in random controls (P = 0.017). All reactive arthritis patients with this subtype were positive for HLA-B27. DRB1*04-DQB1*0302 haplotype was increased in patients with rheumatoid arthritis (28/92, 30%) compared with reactive arthritis (12/126, 10%) or with the controls (12/100, 12%; P = 0.003). HLA-B*2705 was by far the dominant B27 subtype both in reactive arthritis patients with the particular DRB1*0408-DQB1*0301 haplotype and in controls. It was found in 11 out of 12 DR analysed patients, as well as in 10 out of 11 randomly selected B27 positive controls.
CONCLUSIONS—Although no single class II allele was found to be increased among patients with reactive arthritis, HLA-B27, DRB1*0408, and DQB1*0301 might exert a haplotypic effect in the pathogenesis of reactive arthritis, or they may be markers of a subset of B27 haplotypes conferring susceptibility.
OBJECTIVE—It has recently been observed that non-inherited maternal DR4 antigens (NIMAs) of DR4 negative rheumatoid arthritis (RA) patients were increased compared with non-inherited paternal DR4 antigens (NIPAs). The aim of this study was to determine the prevalence of non-inherited DR4 antigens and DRB1 alleles in parents of RA patients.
METHODS—HLA-DR serology and DRB1 typing was performed in 97 RA patients and their parents. NIMA and NIPA frequencies were compared, stratified according to the presence of DR4 and/or the shared epitope (SE).
RESULTS—In DR4 negative patients, NIMA DR4 was increased compared with NIPA DR4 (OR 3.10, 95% CI 0.76, 12.70). When combined with results from a previous study this increase was significant (OR 3.65, 95% CI 1.29, 10.31). The NIMA effect of SE positive DR4 subtypes in this study (OR 4.73, 95% CI 0.94, 23.8) was stronger than the NIMA effect of combined SE positive DRB1 alleles (OR 2.19 95% CI 0.36, 13.22).
CONCLUSIONS—The association between non-inherited maternal HLA-DR4 alleles and the susceptibility to RA was observed in two independent populations.
Keywords: rheumatoid arthritis; non-inherited maternal DR4 antigens; HLA; genetics
OBJECTIVE--To reproduce findings from previous reports that non-inherited maternal HLA class II antigens might contribute to rheumatoid arthritis (RA) susceptibility in the offspring. METHODS--Families were recruited from the Arthritis and Rheumatism Council's National Repository of RA families and HLA-DRB1 alleles were examined in these individuals and their first degree relatives using DNA typing methods. RESULTS--There was no evidence of an increase in either non-inherited maternal HLA-DR4 or the HLA-DRB1 shared epitope as a whole compared with the frequency expected using the non-inherited paternal antigens as controls. CONCLUSIONS--The numbers of probands who were shared epitope negative were small, but we are unable to confirm in these families the findings that non-inherited maternal HLA contributes an additional susceptibility factor to rheumatoid arthritis.
The revised shared epitope (SE) concept in rheumatoid arthritis (RA) is based on the presence (S) or absence (X) of the SE RAA amino acid motif at positions 72 to 74 of the third hypervariable region of the various human leucocyte antigen (HLA)-DRB1 alleles. The purpose of this study was to investigate SE subtypes on the basis of the American College of Rheumatology 1987 revised criteria for the classification of RA in a cohort of South African RA patients (n = 143) and their association with clinical and circulating biomarkers of disease activity (autoantibodies, acute phase reactants and cytokines).
Genomic DNA was analysed using high-resolution recombinant sequence-specific oligonucleotide PCR typing of the HLA-DRB1 allele. Subtypes of the SE were classified according to the amino acids at positions 72 to 74 for the RAA sequence, and further sub-divided according to the amino acids at positions 70 and 71, which either contribute to (S2, S3P), or negate (S1, S3D) RA susceptibility. Disease activity was assessed on the basis of (1) Disease Activity Score in 28 joints using C-reactive protein (CRP), (2) rheumatoid factor (RF), (3) CRP and (4) serum amyloid A by nephelometry, anticyclic citrullinated peptide antibodies (aCCP) by an immunofluorometric procedure, and cytokines by multiplex bead array technology.
Of the 143 RA patients, 81 (57%) were homozygous (SS) and 50 (35%) were heterozygous (SX) for the SE alleles with significant overexpression of S2 and S3P (respective odds ratios (ORs) 5.3 and 5.8; P < 0.0001), and 12 (8%) were classified as no SE allele (XX). Both the SS and SX groups showed a strong association with aCCP positivity (OR = 10.2 and P = 0.0010, OR = 9.2 and P = 0.0028, respectively) relative to the XX group. Clinical scores and concentrations of the other biomarkers of disease activity (RF, CRP and T helper cell type 1 (Th1), Th2, macrophage and fibroblast cytokines) were also generally higher in the SS group than in the SX and XX groups.
RA susceptibility alleles investigated according to revised criteria for the classification of RA were significantly increased in South African RA patients and strongly associated with aCCP in particular as well as with circulating cytokines and disease severity.
anticyclic citrullinated peptide antibodies; C-reactive protein; fibroblast cytokines; macrophage cytokines; rheumatoid factor; serum amyloid A; Th1/Th2 cytokines
Certain sequences present in the hypervariable region of human leucocyte antigen (HLA)‐DRB1 known as the shared epitope (SE) are hypothesised to increase the risk of rheumatoid arthritis (RA), whereas alleles encoding aspartic acid at position 70 (D70 alleles) may have a protective effect.
Patient HLA‐DRB1 serotypes were assessed and the genotypes encoding the SE motif or the putatively protective D70 motif identified in a large RA cohort. Logistic regression was used to analyse associations of genotype with presence of disease, comorbidities and disease severity, and association between genotype and change in disease activity over time.
The 689 patients enrolled had a mean (SD) age of 57.9 (13.7) years and mean (SD) disease duration of 15.3 (12.7) years. In a comparison with 482 ethnicity matched population‐based controls, the D70 sequence exerted a strong protective effect (OR = 0.52, p<0.001) that remained significant when the SE at the same locus was accounted for (OR = 0.72, 95% CI 0.60 to 0.86, p<0.001). The SE assessed on all HLA‐DRB1 serotypic backgrounds except DR1 was associated with RA susceptibility (additive OR = 2.43, p<0.001). Associations were found between SE and serum levels of rheumatoid factor (p<0.001, with correlation of 0.18) and anti‐cyclic citrullinated peptide antibodies (p<0.001, with correlation of 0.25) but not with serum C‐reactive protein.
The D70 allele has a significant protective effect that is mitigated but still significant when the risk effect of the SE at the same locus is taken into account. The presence of the SE on DR4 is associated with greater RA susceptibility and certain disease‐activity measures.
rheumatoid arthritis; genetics; shared epitope; patient registry
To study the gene–environment interaction of tobacco exposure and shared epitope on autoantibodies in patients with rheumatoid arthritis and undifferentiated arthritis.
From incident cases of arthritis (n = 1305), patients who did not fulfil any classification criteria (undifferentiated arthritis (n = 486)) and those who fulfilled the American College of Rheumatology criteria for rheumatoid arthritis (n = 407) were identified. IgM rheumatoid factor (RF), anti‐cyclic‐citrullinated peptide (CCP) antibodies, and HLA‐DRB1 alleles were determined.
In rheumatoid arthritis, an interaction was found between tobacco exposure and shared epitope for the presence of anti‐CCP antibodies, as the odds ratio for anti‐CCP antibodies in patients having both tobacco exposure (TE) and shared epitope (SE) was higher than the summed odds ratios of patients having only tobacco exposure or shared epitope (odds ratios: TE+/SE−, 1.07; TE−/SE+, 2.49; and TE+/SE+, 5.27—all relative to TE−/SE−). A similar effect was found for RF, but stratification showed that the interaction primarily associated with the anti‐CCP antibody response. In patients with undifferentiated arthritis at two weeks, or with persistent undifferentiated arthritis after one year, no interaction between tobacco exposure and shared epitope was observed for the presence of autoantibodies.
Tobacco exposure increases the risk factor for anti‐CCP antibodies only in shared epitope positive patients with rheumatoid arthritis. The gene–environment interaction between smoking and shared epitope leading to autoantibodies is specific for rheumatoid arthritis and is not observed in undifferentiated arthritis.
rheumatoid arthritis; anti‐CCP antibodies; rheumatoid factor; smoking; shared epitope
To determine whether shared epitope (SE)–containing HLA–DRB1 alleles are associated with rheumatoid arthritis (RA) in African Americans and whether their presence is associated with higher degrees of global (genome-wide) genetic admixture from the European population.
In this multicenter cohort study, African Americans with early RA and matched control subjects were analyzed. In addition to measurement of serum anti–cyclic citrullinated peptide (anti-CCP) antibodies and HLA–DRB1 genotyping, a panel of >1,200 ancestry-informative markers was analyzed in patients with RA and control subjects, to estimate the proportion of European ancestry.
The frequency of SE-containing HLA–DRB1 alleles was 25.2% in African American patients with RA versus 13.6% in control subjects (P = 0.00005). Of 321 patients with RA, 42.1% had at least 1 SE-containing allele, compared with 25.3% of 166 control subjects (P = 0.0004). The mean estimated percent European ancestry was associated with SE-containing HLA–DRB1 alleles in African Americans, regardless of disease status (RA or control). As reported in RA patients of European ancestry, there was a significant association of the SE with the presence of the anti-CCP antibody: 86 (48.9%) of 176 patients with anti-CCP antibody–positive RA had at least 1 SE allele, compared with 36 (32.7%) of 110 patients with anti-CCP antibody–negative RA (P = 0.01, by chi-square test).
HLA–DRB1 alleles containing the SE are strongly associated with susceptibility to RA in African Americans. The absolute contribution is less than that reported in RA among populations of European ancestry, in which ~50–70% of patients have at least 1 SE allele. As in Europeans with RA, the SE association was strongest in the subset of African American patients with anti-CCP antibodies. The finding of a higher degree of European ancestry among African Americans with SE alleles suggests that a genetic risk factor for RA was introduced into the African American population through admixture, thus making these individuals more susceptible to subsequent environmental or unknown factors that trigger the disease.
The HLA-DRB1 gene was reported to be associated with anticitrullinated protein/peptide autoantibody (ACPA) production in rheumatoid arthritis (RA) patients. A new classification of HLA-DRB1 alleles, reshaping the shared epitope (SE) hypothesis, was recently found relevant in terms of RA susceptibility and structural severity.
We investigated the relevance of this new classification of HLA-DRB1 SE+ alleles in terms of rheumatoid factor (RF) and ACPA production in a sample of French RA patients.
We studied 160 early RA patients included in a prospective longitudinal cohort of French Caucasian patients with recent-onset arthritis. RF, anticyclic citrullinated peptide 2 (anti-CCP2) and antideiminated human fibrinogen autoantibodies (AhFibA) were assessed in all patients at inclusion. The HLA-DRB1 gene was typed by PCR-sequence specific oligonucleotides probes (PCR-SSOP), and SE+ alleles were classified into four groups (S1, S2, S3P, S3D) according to the new classification.
The new classification of HLA-DRB1 SE+ alleles distinguishes predisposing and protective alleles for RF, anti-CCP2 or AhFibA production. The presence of S2 or S3P alleles is associated with both RF, anti-CCP2 or AhFibA positivity, whereas the presence of S3D or S1 alleles appears to be protective for RF, anti-CCP2 or AhFibA positivity.
The new classification of HLA-DRB1 SE+ alleles is relevant in terms of autoantibody production in early RA patients by differentiating predisposing and protective alleles for RF or ACPA production.
OBJECTIVE—To analyse the influence of shared epitope positive HLA-DRB1 alleles (QKRAA or QRRAA) ) on rheumatoid arthritis (RA) susceptibility and severity in Chileans, a population that exhibits a weak association with HLA-DR4.
METHODS—Prevalence of alleles DRB1*01 and DRB1*04 alleles was determined by polymerase chain reaction amplification and sequence specific oligonucleotide hybridisation in 129 RA patients with defined clinical features and in 97 healthy controls.
RESULTS—The shared epitope was found in 70 (54%) of the RA patients and in 29 (30%) of controls (odds ratio (OR) =3; 95% confidence intervals (CI) = 1.5, 5.1; p = 0.0004), and was present in a double dose in 20% of patients versus 4% of controls (OR = 6; 95% CI = 2, 21; p = 0.0009). HLA-DRB1*0403 was the most prevalent DR4 subtype in controls (19%). HLA-DRB1*0404 or *0408 were the alleles most prominently associated with RA, 19% versus 6 % in controls (OR=3; 95% CI = 1.3, 10; p = 0.01). The risk of RA in those carrying a double dose of the shared epitope was 7.5 times that seen in patients lacking the epitope. Disease severity was moderate: 33% had extra-articular manifestations. The double dose was associated with an increased risk of vasculitis or extra-articular manifestations. However, 59 patients (46%) did not carry the shared epitope and 18 of them (31%) had extra-articular manifestations.
CONCLUSIONS—The weak association of RA with DR4 in Chileans seems to relate to a relatively high frequency of the DRB1*0403 allele among DR4 subtypes. As in other populations, the shared epitope in double dose is associated with RA development, especially in its more severe forms. However, both development and expression of severe forms of the disease were independent of the shared epitope in a high proportion of patients, thus emphasising the genetic heterogeneity of the disease and the possible involvement of other genetic elements.
BACKGROUND AND OBJECTIVES:
Analysis of the role of different alleles of human leukocyte antigen (HLA) in rheumatoid arthritis (RA) patients is necessary in many populations and geographical areas. The aim of the present study was to investigate the frequency of HLA-DRB1 alleles in RA patients, comparing with that in control group in southeast Iran.
DESIGN AND SETTING:
Case-control study of rheumatoid arthritis patients referred to rheumatology clinic at university hospital.
PATIENTS AND METHODS:
The frequency of HLA-DRB1 alleles was determined in 79 RA patients and 93 healthy subjects in Zahedan, southeast Iran. HLA-DRB1 allele types were identified by polymerase chain reaction with sequence-specific primer (PCR-SSP).
The HLA-DRB1*10 allele showed a significantly higher frequency in patients with RA (OR=2.698, 95% CI=1.087-6.699, P=.045), while the frequency of DRB1*03 allele in these subjects was significantly lower than that in the control group (OR=0.447, 95% CI=0.2285-0.8729, P=.021). The frequencies of DRB1*01, DRB1*04, DRB1*07, DRB1*09, DRB1*11, DRB1*13, DRB1*14, DRB1*15, DRB1*16 were not significantly different between RA subjects and the control group.
The data suggest that the DRB1*10 allele is a risk factor and DRB1*03 is protective for RA in this population.
OBJECTIVE—To determine whether glutathione S-transferase GSTM1, GSTM3, GSTT1, and GSTP1 genotypes influence susceptibility or outcome in rheumatoid arthritis (RA).
METHODS—277 RA patients were compared with 577 controls to examine any associations between GST genotypes and susceptibility to RA. The effect of genotypes on outcome (Larsen and functional scores) and time integrated acute phase responses (erythrocyte sedimentation rate and C reactive protein) was assessed in 122 patients with disease duration of 5-10 years. GST and HLA-DRB1 genotypes were determined using polymerase chain reaction based assays. Data were analysed using multiple regression analysis with correction for age, sex, disease duration, and the DRB1 associated shared epitope (SE) and rheumatoid factor (RF) positivity where appropriate.
RESULTS—The GSTM1*A/*B genotype was less common in RA cases (3 of 276) than in controls (22 of 591) (exact p=0.047), though significance was lost when adjustment was made for multiple comparisons. The Larsen score was higher (p=0.039) in the GSTM1 null patients (89.9) than those with other GSTM1 genotypes (74.7), and this was independent of the SE. Again, correction for multiple testing resulted in loss of significance. The difference in Larsen scores between patients homozygous or negative for the SE (87.9 v 74.3) was similar to that between GSTM1 null and non-null patients. No associations between GSTM3 or GSTT1 genotypes and disease markers were identified although the association between GSTP1*B/*B and Larsen score approached significance (p=0.096).
CONCLUSION—It is proposed that certain GSTs may influence susceptibility and radiological progression in RA and that this is independent of the effect of the HLA-DRB1 associated SE. The mechanism for this effect is presumed to be because of differences in the ability of various GST enzymes to utilise the cytotoxic products of oxidant stress. Although significance was lost after correction for multiple testing, the data indicate that further studies may be of value in RA to determine the influence of the GST and other genes involved in cellular protection against oxidative stress.
Keywords: rheumatoid arthritis; glutathione S-transferase; polymorphism; shared epitope
In humans, HLA-DR alleles sharing amino acids at the third hypervariable region with DRB1*0401(shared epitope) are associated with a predisposition to rheumatoid arthritis, whereas DRB1*0402 is not associated with such a predisposition. Both DRB1*0402 and DRB1*0401 occur in linkage with DQ8 (DQB1*0302). We have previously shown that transgenic (Tg) mice expressing HLA-DRB1*0401 develop collagen-induced arthritis. To delineate the role of “shared epitope” and gene complementation between DR and DQ in arthritis, we generated DRB1*0402, DRB1*0401.DQ8, and DRB1*0402.DQ8 Tg mice lacking endogenous class II molecules, AEo. DRB1*0402 mice are resistant to develop arthritis. In double-Tg mice, the DRB1*0401 gene contributes to the development of collagen-induced arthritis, whereas DRB1*0402 prevents the disease. Humoral response to type II collagen is not defective in resistant mice, although cellular response to type II collagen is lower in *0402 mice compared with *0401 mice. *0402 mice have lower numbers of T cells in thymus compared with *0401 mice, suggesting that the protective effect could be due to deletion of autoreactive T cells. Additionally, DRB1*0402 mice have a higher number of regulatory T cells and show increased activation-induced cell death, which might contribute toward protection. In DRB1*0401.DQ8 mice, activated CD4+ T cells express class II genes and can present DR4- and DQ8-restricted peptides in vitro, suggesting a role of class II+ CD4 T cells locally in the joints. The data suggest that polymorphism in DRB1 genes determines predisposition to develop arthritis by shaping the T cell repertoire in thymus and activating autoreactive or regulatory T cells.
Rheumatoid arthritis, a chronic inflammatory joint disease, is strongly associated with HLA-DRB1*01 and *04 alleles that have in common similar 5-amino acid motifs in the third hypervariable region of DRβ1 (QKRAA, QRRAA, RRRAA), the so called shared epitope (SE). Most patients with RA carry 1 or 2 doses of the SE, with particular genetic combinations at higher risk. In recent work we provided evidence that patients who lack HLA-DRB1*01 and/or *04 alleles can acquire RA susceptibility through fetal, maternal or iatrogenic microchimerism. We also discuss how Mc carrying HLA-DRB1*04 alleles is more likely to be present in the peripheral blood of RA patients compared to Mc carrying HLA-DRB1*01 alleles. We further analyze our results in light of the hierarchy for RA risk with different combinations of the SE. How Mc could contribute to RA susceptibility and whether it also contributes to the hierarchy of risk observed with particular combinations of SE-containing alleles is certainly the beginning of an intriguing story and may offer hope for future therapeutic and/or preventative interventions.
microchimerism; HLA; shared epitope; rheumatoid arthritis
To provide a table indicating the risk for developing anti citrullinated protein antibody (ACPA) positive rheumatoid arthritis (RA) according to one’s HLA-DRB1 genotype.
We HLA-DRB1 genotyped 857 patients with ACPA positive RA and 2178 controls from South Eastern and Eastern France and calculated Odds Ratios (OR) for developing RA for 106 of 132 possible genotypes accounting for 97% of subjects.
HLA-DRB1 genotypic ORs for developing ACPA positive RA range from 28 to 0.19. HLA-DRB1 genotypes with HLA-DRB1*04SE (HLA-DRB1*0404, HLA-DRB1*0405, HLA-DRB1*0408), HLA-DRB1*04∶01, HLA-DRB1*01 are usually associated with high risk for developing RA. The second HLA-DRB1 allele in genotype somewhat modulates shared epitope associated risk. We did not identify any absolutely protective allele. Neither the Reviron, nor the du Montcel models accurately explains our data which are compatible with the shared epitope hypothesis and suggest a dosage effect among shared epitope positive HLA-DRB1 alleles, double dose genotypes carrying higher ORs than single dose genotypes.
HLA-DRB1 genotypic risk for developing ACPA positive RA is influenced by both HLA-DRB1 alleles in genotype. We provide an HLA-DRB1 genotypic risk table for ACPA positive RA.
An association has previously been shown between antibiotic-refractory Lyme arthritis, the human histocompatibility leukocyte antigen (HLA)–DR4 molecule, and T cell recognition of an epitope of Borrelia burgdorferi outer-surface protein A (OspA163–175). We studied the frequencies of HLA-DRB1-DQA1-DQB1 haplotypes in 121 patients with antibiotic-refractory or antibiotic-responsive Lyme arthritis and correlated these frequencies with in vitro binding of the OspA163–175 peptide to 14 DRB molecules. Among the 121 patients, the frequencies of HLA-DRB1-DQA1-DQB1 haplotypes were similar to those in control subjects. However, when stratified by antibiotic response, the frequencies of DRB1 alleles in the 71 patients with antibiotic-refractory arthritis differed significantly from those in the 50 antibiotic-responsive patients (log likelihood test, P = 0.006; exact test, P = 0.008; effect size, Wn = 0.38). 7 of the 14 DRB molecules (DRB1*0401, 0101, 0404, 0405, DRB5*0101, DRB1*0402, and 0102) showed strong to weak binding of OspA163–175, whereas the other seven showed negligible or no binding of the peptide. Altogether, 79% of the antibiotic-refractory patients had at least one of the seven known OspA peptide–binding DR molecules compared with 46% of the antibiotic-responsive patients (odds ratio = 4.4; P < 0.001). We conclude that binding of a single spirochetal peptide to certain DRB molecules is a marker for antibiotic-refractory Lyme arthritis and might play a role in the pathogenesis of the disease.