Opposing effects of the D70 mutation and the shared epitope in HLA-DR4 on disease activity and certain disease phenotypes in rheumatoid arthritis

Immunogenicity of a rheumatoid arthritis protective sequence when acquired through microchimerism

HLA class II genes provide the strongest genetic contribution to rheumatoid arthritis (RA). HLA-DRB1 alleles encoding the sequence DERAA are RA-protective. Paradoxically, RA risk is increased in women with DERAA⁺ children born prior to onset. We developed a sensitive qPCR assay specific for DERAA, and found 53% of DERAA^-/- women with RA had microchimerism (Mc; pregnancy-derived allogeneic cells) carrying DERAA (DERAA-Mc) vs. 6% of healthy women. DERAA-Mc quantities correlated with an RA-risk genetic background including DERAA-binding HLA-DQ alleles, early RA onset, and aspects of RA severity. CD4⁺ T cells showed stronger response against DERAA⁺ vs. DERAA^- allogeneic cell lines in vitro, in line with an immunogenic role of allogeneic DERAA. Results indicate a model where DERAA-Mc activates DERAA-directed T cells that are naturally present in DERAA^-/- individuals and can have cross-reactivity against joint antigens. Moreover, we provide an explanation for the enigmatic observation that the same HLA sequence differentially affects RA risk through Mendelian inheritance vs. microchimeric cell acquisition.

Human Leukocyte Antigen-Disease Associations in Rheumatoid Arthritis

The cause and pathogenesis of rheumatoid arthritis (RA) are influenced by environmental and genetic risk factors. Shared epitope-coding human leukocyte antigen (HLA)-DRB1 alleles increase RA risk and severity; however, the underlying mechanisms of action remain unclear. In contrast, several other DRB1 alleles protect against RA. Additionally, genome-wide association studies suggest that RA associates with other, HLA and non-HLA, genes; but the relative contributions of such risk loci to RA are incompletely understood. Future research challenges include integrating the epidemiologic and genomic data into validated arthritogenic pathways and determining the mechanisms of interaction between RA risk genes and environmental influences.

A reciprocal HLA-Disease Association in Rheumatoid Arthritis and Pemphigus Vulgaris

Human leukocyte antigens (HLA) have been extensively studied as being antigen presenting receptors, but many aspects of their function remain elusive, especially their association with various autoimmune diseases. Here we discuss an illustrative case of the reciprocal relationship between certain HLA-DRB1 alleles and two diseases, rheumatoid arthritis (RA) and pemphigus vulgaris (PV). RA is strongly associated with HLA-DRB1 alleles that encode a five amino acid sequence motif in the 70-74 region of the DR beta chain, called the shared epitope (SE), while PV is associated with the HLA-DRB1*04:02 allele that encodes a different sequence motif in the same region. Interestingly, while HLA-DRB1*04:02 confers susceptibility to PV, this and other alleles that encode the same sequence motif in the 70-74 region of the DR beta chain are protective against RA. Currently, no convincing explanation for this antagonistic effect is present. Here we briefly review the immunology and immunogenetics of both diseases, identify remaining gaps in our understanding of their association with HLA, and propose the possibility that the 70-74 DR beta epitope may contribute to disease risk by mechanisms other than antigen presentation.

Crossreactivity to vinculin and microbes provides a molecular basis for HLA-based protection against rheumatoid arthritis

The HLA locus is the strongest risk factor for anti-citrullinated protein antibody (ACPA)(+) rheumatoid arthritis (RA). Despite considerable efforts in the last 35 years, this association is poorly understood. Here we identify (citrullinated) vinculin, present in the joints of ACPA(+) RA patients, as an autoantigen targeted by ACPA and CD4(+) T cells. These T cells recognize an epitope with the core sequence DERAA, which is also found in many microbes and in protective HLA-DRB1*13 molecules, presented by predisposing HLA-DQ molecules. Moreover, these T cells crossreact with vinculin-derived and microbial-derived DERAA epitopes. Intriguingly, DERAA-directed T cells are not detected in HLA-DRB1*13(+) donors, indicating that the DERAA epitope from HLA-DRB1*13 mediates (thymic) tolerance in these donors and explaining the protective effects associated with HLA-DRB1*13. Together our data indicate the involvement of pathogen-induced DERAA-directed T cells in the HLA-RA association and provide a molecular basis for the contribution of protective/predisposing HLA alleles.

Functional impact of a spectrum of interstitial lung abnormalities in rheumatoid arthritis

BACKGROUND

Approximately 10% of patients with rheumatoid arthritis (RA) have interstitial lung disease (ILD), and one-third have subclinical ILD on chest CT scan. In this study, we aimed to further characterize functional decrements in a spectrum of RA-associated ILD.

METHODS

All subjects were enrolled in the Brigham and Women's Hospital Rheumatoid Arthritis Sequential Study (BRASS). The presence of interstitial lung abnormalities (ILAs) on clinically indicated chest CT scans was determined using a previously validated sequential reading method. Univariate and multivariate analyses were used to assess the association between degree of ILAs and physiologic, functional, and demographic variables of interest.

RESULTS

Of 1,145 BRASS subjects, 91 subjects (8%) were included in this study. Twelve had radiologically severe ILAs, 34 had ILAs, and 38 had no ILAs on CT scan. Subjects with radiologically severe ILAs were older (P = .0037), had increased respiratory symptoms (cough, P = .027; dyspnea, P = .010), and more severe RA disease (rheumatoid factor, P = .018; total swollen joints, P = .046) compared with subjects with no ILAs. Participants also had a trend toward having an increased smoking history (P = .16) and having lower FVC % predicted (77% vs 94%, P = .097) and diffusion capacity of carbon monoxide % predicted (52% vs 77%, P = .068). Similar but attenuated increases in respiratory symptoms, functional decrements, and RA disease severity were observed in subjects with ILAs compared with those with no ILAs.

CONCLUSIONS

We have shown that patients with RA have varying degrees of ILAs that are associated with a spectrum of functional and physiologic decrements. Our findings suggest that improved risk stratification and detection of ILAs will provide a therapeutic window that could improve RA-ILD outcomes.

The influence of polygenic risk scores on heritability of anti-CCP level in RA

The objective of this study was to study genetic factors that influence quantitative anticyclic citrullinated peptide (anti-CCP) antibody levels in RA patients. We carried out a genome-wide association study (GWAS) meta-analysis using 1975 anti-CCP+ RA patients from three large cohorts, the Brigham Rheumatoid Arthritis Sequential Study (BRASS), North American Rheumatoid Arthritis Consortium (NARAC) and the Epidemiological Investigation of RA (EIRA). We also carried out a genome-wide complex trait analysis (GCTA) to estimate the heritability of anti-CCP levels. GWAS-meta-analysis showed that anti-CCP levels were most strongly associated with the human leukocyte antigen (HLA) region with a P-value of 2 × 10(-11) for rs1980493. There were 112 SNPs in this region that exceeded the genome-wide significance threshold of 5 × 10(-8), and all were in linkage disequilibrium (LD) with the HLA- DRB1*03 allele with LD r(2) in the range of 0.25-0.88. Suggestive novel associations outside of the HLA region were also observed for rs8063248 (near the GP2 gene) with a P-value of 3 × 10(-7). None of the known RA risk alleles (∼52 loci) were associated with anti-CCP level. Heritability analysis estimated that 44% of anti-CCP variation was attributable to genetic factors captured by GWAS variants. In summary, anti-CCP level is a heritable trait, and HLA-DR3 and GP2 are associated with lower anti-CCP levels.

Associations of smoking and alcohol consumption with disease activity and functional status in rheumatoid arthritis

OBJECTIVE

To investigate the associations of smoking and alcohol consumption with disease activity and functional status in rheumatoid arthritis (RA).

METHODS

We conducted a prospective study consisting of 662 patients with RA who were followed up to 7 years from the Brigham and Women's Hospital Rheumatoid Arthritis Sequential Study. Smoking and alcohol consumption were assessed through yearly questionnaires. The disease activity and functional status were measured annually by the Disease Activity Score examined in 28 commonly affected joints using C-reactive protein (DAS28-CRP3) and the Modified Health Assessment Questionnaire (MHAQ). Linear mixed models were developed to assess the longitudinal effects of smoking and alcohol consumption on DAS28-CRP3 and MHAQ after adjustment for potential confounders. The HLA-DRB1 shared epitope (HLA-SE) by smoking and alcohol interactions were also evaluated in the analysis.

RESULTS

The median followup time of the cohort was 4 years. Current smoking was not associated with DAS28-CRP3 in our study, but was associated with a higher MHAQ than nonsmokers with seropositive RA (p = 0.05). Alcohol consumption showed an approximate J-shaped relationship with MHAQ, with the minima occurring at 5.1-10.0 g/day. Compared to no alcohol use, alcohol consumption of 5.1-10.0 g/day was associated with a significant decrease of MHAQ (p = 0.02). When stratified by HLA-SE, the effect of alcohol consumption appeared to be stronger in HLA-SE-positive RA than HLA-SE-negative RA.

CONCLUSION

We found that current smoking was associated with a worse functional status, while moderate alcohol consumption was associated with a better functional status in RA. Replications of these findings in other prospective studies are needed.

HLA-DRB1 shared epitope-dependent DR-DQ haplotypes are associated with both anti-CCP-positive and -negative rheumatoid arthritis in Chinese Han

The association between Human Leukocyte Antigen (HLA) class II and rheumatoid arthritis (RA) has been extensively studied, but few reported DR-DQ haplotype. Here we investigated the association of HLA-DRB1, DQA1, DQB1, and DR-DQ haplotypes with RA susceptibility and with anti-CCP antibodies in 281 RA patients and 297 control in Han population. High-resolution genotyping were performed. The HLA-DRB1 shared epitope (SE)-encoding allele *0405 displayed the most significant RA association (P = 1.35×10⁻⁶). The grouped DRB1 SE alleles showed great association with RA (P = 3.88×10⁻¹³). The DRB1 DRRAA alleles displayed significant protective effects (P = 0.021). The SE-dependent DR-DQ haplotype SE-DQ3/4/5 remained strong association with both anti-CCP -positive (P = 3.71×10⁻¹³) and -negative RA (P = 3.89×10⁻⁵). Our study revealed that SE alleles and its haplotypes SE-DQ3/4/5 were highly associated with RA susceptibility in Han population. The SE-DQ3/4/5 haplotypes were associated with both anti-CCP positive RA and -negative RA.

Genetics and epigenetics of rheumatoid arthritis

Investigators have made key advances in rheumatoid arthritis (RA) genetics in the past 10 years. Although genetic studies have had limited influence on clinical practice and drug discovery, they are currently generating testable hypotheses to explain disease pathogenesis. Firstly, we review here the major advances in identifying RA genetic susceptibility markers both within and outside of the MHC. Understanding how genetic variants translate into pathogenic mechanisms and ultimately into phenotypes remains a mystery for most of the polymorphisms that confer susceptibility to RA, but functional data are emerging. Interplay between environmental and genetic factors is poorly understood and in need of further investigation. Secondly, we review current knowledge of the role of epigenetics in RA susceptibility. Differences in the epigenome could represent one of the ways in which environmental exposures translate into phenotypic outcomes. The best understood epigenetic phenomena include post-translational histone modifications and DNA methylation events, both of which have critical roles in gene regulation. Epigenetic studies in RA represent a new area of research with the potential to answer unsolved questions.

A spectrum of susceptibility to rheumatoid arthritis within HLA-DRB1: stratification by autoantibody status in a large UK population

Previously-proposed rheumatoid arthritis (RA) HLA-DRB1 susceptibility and protective models were compared, based on amino acids at positions 67-74 and autoantibody combinations. 3 657 RA patients and 1 357 controls were studied using logistic regression, with secondary stratification by anti-citrullinated peptide antibodies(ACPA) and rheumatoid factor(RF). Susceptibility models were based on previously defined HLA-DRB1 shared epitope(SE) subgroups. (70)DERAA(74), D(70) and I(67) protective models were compared, adjusting for HLA-DRB1 SE. A hierarchy of risk was observed within the HLA-DRB1 SE, particularly for ACPA-positive and RF-positive RA: HLA-DRB1(*)0401∼(*)0404>(*)0101∼(*)1001 ((*)0404>(*)0101: P=0.0003). HLA-DRB1(*)0401/(*)0404 compound heterozygosity conferred a risk similar to (*)0401 homozygosity (P=0.70). Protective effects of D(70) and I(67) were similar. Predictions of the D(70) model fitted the data better than those of the I(67) model. The protective effect of D(70) showed a gene-dose effect (OR 0.82, 95% CI 0.73-0.92, P=5.8 × 10(-4)), but was only seen in RA patients positive for RF or ACPA. HLA-DRB1 SE alleles were also associated with ACPA-negative, RF-positive RA (OR 1.42 (1.15-1.76), P=0.0012). In conclusion, HLA-DRB1 SE alleles show heterogeneity in RA susceptibility; their major effect appears to be mediated by ACPA positivity, but a significant association of HLA-DRB1 SE with RF-positive, ACPA-negative RA was also observed. D(70) specifically protected against antibody-positive RA.

Using genetic and clinical data to understand response to disease-modifying anti-rheumatic drug therapy: data from the Brigham and Women's Hospital Rheumatoid Arthritis Sequential Study

The objective of this review is to report on the progress of the Brigham and Women's Hospital Rheumatoid Arthritis Sequential Study (BRASS) Registry data collection and summarize previous research in understanding therapeutic response to DMARDs using clinical and genetic data. The BRASS Registry, established in 2003, is a large, single-centre, prospective and observational cohort of 1100 RA patients. Patients with either new-onset or established RA disease are recruited from the practices of rheumatologists. Annual visits collect information on demographics, 28-joint DAS-CRP3 (DAS-28-CRP3), medication use, comorbidities and functional status (Modified Health Assessment Questionnaire, Short Form Health Survey 12). Two published studies have utilized BRASS to examine genetic predictors of treatment response. In a cross-sectional study, examining the association between candidate single nucleotide polymorphisms (SNPs) and disease activity in a subset of 120 RA patients on MTX monotherapy, the minor allele of ATIC rs4673993 was associated with low disease activity (P=0.01, DAS-28-CRP3≤3.2). In an international collaboration, 55 BRASS patients receiving anti-TNF therapy were genotyped for 31 SNPs associated with the risk of RA. With our collaborators, we discovered an SNP at the protein tyrosine phosphatase, receptor type, C (PTPRC) gene locus that was associated with EULAR 'good response'. With accurate data collection and the capacity to run genome-wide association studies and SNP analyses, the BRASS Registry has the ability to determine the contribution of genetic variants to disease onset and to assess their usefulness as biomarkers for treatment response and drug toxicity.

Aberrant IgG galactosylation precedes disease onset, correlates with disease activity, and is prevalent in autoantibodies in rheumatoid arthritis

OBJECTIVE

To examine the association between aberrant IgG galactosylation and disease parameters in rheumatoid arthritis (RA).

METHODS

Analysis of N-glycan in serum samples from multiple cohorts was performed. The IgG N-glycan content and the timing of N-glycan aberrancy relative to disease onset were compared in healthy subjects and in patients with RA. Correlations between aberrant galactosylation and disease activity were assessed in the RA cohorts. The impact of disease activity, sex, age, anti-cyclic citrullinated peptide (anti-CCP) antibody titer, disease duration, and C-reactive protein level on aberrant galactosylation was determined using multivariate analysis. The N-glycan content was also compared between epitope affinity-purified autoantibodies and the remaining IgG repertoire in RA patients.

RESULTS

Our results confirm the aberrant galactosylation of IgG in RA patients as compared with healthy controls (mean +/- SD 1.36 +/- 0.43 versus 1.01 +/- 0.23; P < 0.0001). We observed a significant correlation between levels of aberrant IgG galactosylation and disease activity (Spearman's rho = 0.37, P < 0.0001). This correlation was higher in women (Spearman's rho = 0.60, P < 0.0001) than in men (Spearman's rho = 0.16, P = 0.10). Further, aberrant IgG galactosylation substantially predated the onset of arthritis and the diagnosis of RA (3.5 years) and resided selectively in the anticitrullinated antigen fraction.

CONCLUSION

Our findings identify aberrant IgG galactosylation as a dysregulated component of the humoral immune response in RA that begins prior to disease onset, associates with disease activity in a sex-specific manner, and resides preferentially in autoantibodies.

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.

Genome-wide association study of determinants of anti-cyclic citrullinated peptide antibody titer in adults with rheumatoid arthritis

We carried out a genome-wide association study of genetic predictors of anti-cyclic citrullinated peptide antibody (anti-CCP) level in 531 self-reported non-Hispanic Caucasian Rheumatoid Arthritis (RA) patients enrolled in the Brigham Rheumatoid Arthritis Sequential Study (BRASS). For replication, we then analyzed 289 single nucleotide polymorphisms (SNPs) with P < 0.001 in BRASS in an independent population of 849 RA patients from the North American Rheumatoid Arthritis Consortium (NARAC). BRASS and NARAC samples were genotyped using the Affymetrix 100K and Illumina 550K platforms respectively. Association between SNPs and anti-CCP titer was tested using general linear models. The five most significant SNPs from BRASS all were within the major histocompatibility complex (MHC) region (P < or = 3.5 x 10(-6)). After controlling for the human leukocyte antigen shared epitope (HLA-SE), the top SNPs still yielded P values < 0.0002. In NARAC, a single SNP from the MHC region near BTNL2 and HLA-DRA, rs1980493 (r(2) = 0.85 with the top five SNPs from BRASS), was associated significantly with CCP titer (P = 6.1 x 10(-5)) even after adjustment for the HLA-SE (P = 0.0002). The top SNPs found in BRASS and NARAC had r(2) = 0.46 and 0.64, respectively, to HLA-DRB1 DR3 alleles. These results confirm that the most significant genome region affecting anti-CCP titers in RA is the MHC region. We identified a SNP in moderate linkage disequilibrium (LD) with HLA-DR3, which may influence anti-CCP titer independently of the HLA-SE.

A broad analysis of IL1 polymorphism and rheumatoid arthritis

OBJECTIVE

It has been suggested that polymorphisms in IL1 are correlated with severe and/or erosive rheumatoid arthritis (RA), but the implicated alleles have differed among studies. The aim of this study was to perform a broad and well-powered search for association between allelic polymorphism in IL1A and IL1B and the susceptibility to or severity of RA.

METHODS

Key coding and regulatory regions in IL1A and IL1B were sequenced in 24 patients with RA, revealing 4 novel single-nucleotide polymorphisms (SNPs) in IL1B. These and a comprehensive set of 24 SNPs tagging most of the underlying genetic diversity were genotyped in 3 independent RA case-control sample sets and 1 longitudinal RA cohort, totaling 3,561 patients and 3,062 control subjects.

RESULTS

No fully significant associations were observed. Analysis of the discovery case-control sample sets indicated a potential association of IL1B promoter region SNPs with susceptibility to RA (for RA3/A, odds ratio [OR] 1.27, P = 0.0021) or with the incidence of radiographic erosions (for RA4/C, OR 1.56, P = 0.036), but these findings were not replicated in independent case-control samples. No association with rheumatoid factor, anti-cyclic citrullinated peptide, or the Disease Activity Score in 28 joints was found. None of the associations previously observed in other studies were replicated here.

CONCLUSION

In spite of a broad and highly powered study, we observed no robust, reproducible association between IL1A/B variants and the susceptibility to or severity of RA in white individuals of European descent. Our results provide evidence that, in the majority of cases, polymorphism in IL1A and IL1B is not a major contributor to genetic susceptibility to RA.

Protective effect of noninherited maternal HLA-DR antigens on rheumatoid arthritis development

Rheumatoid arthritis (RA) is a complex genetic disorder in which the HLA-region contributes most to the genetic risk. HLA-DRB1-molecules containing the amino acid sequence DERAA (i.e., HLA-DRB1*0103, *0402, *1102, *1103, *1301, *1302, and *1304) are associated with protection from RA. It has been proposed that not only inherited but also noninherited HLA-antigens from the mother (NIMA) can influence RA-susceptibility. Up to now, no protective NIMAs were described. Here, we studied whether DERAA-containing HLA-DRB1-alleles as NIMA are associated with a protective effect. One hundred seventy-nine families were studied, 88 from the Netherlands and 91 from the United Kingdom. The frequency of DERAA-containing HLA-DRB1-alleles of the Dutch mothers (16.1%), but not of the fathers (26.2%), was lower compared with the general Dutch population (29.3%; P = 0.02). This was replicated in the English set of patients and controls (P = 0.01). Further, of all families, 45 contained at least one DERAA-negative child with RA and at least one DERAA-positive parent. The odds for the DERAA-negative RA patients of having a DERAA-positive mother was significantly lower compared with having a DERAA-positive father (OR 0.25; P = 0.003). These data show a protective NIMA-effect in a human autoimmune disease and indicate that a DERAA-positive mother can transfer protection against RA to her DERAA-negative child.