Compound heterozygosity of HLA-DR4 and DR1 antigens in Asian Indians increases the risk of extra-articular features in rheumatoid arthritis

The diagnostic utility of rheumatoid factor and anticitrullinated protein antibody for rheumatoid arthritis in the Indian population

Background

There is lack of Indian data on diagnostic utility of rheumatoid factor (RF) and anti-citrullinated protein antibody (ACPA) for diagnosis of rheumatoid arthritis (RA) and prevalence of these antibodies in patients with RA and the healthy population. The study was aimed to assess the diagnostic utility and prevalence of RF and ACPA at different titers in the Indian scenario.

Method

All the patients of RA fulfilling the European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) 2010 classification criteria and age and gender-matched healthy controls were included in the study. RF and ACPA were measured by nephelometry and the enzyme-linked immunosorbent assay (ELISA) method, respectively.

Result

Of 803 patients (291 men and 512 women) included, the RF was positive in 566 (70.5%) study patients. The ACPA was positive in 527 (71.7%) patients of 735 of them. Among 408 healthy controls, 45 (11%) were RF positive and 19 (4.7%) were ACPA positive.At the positive cutoff level, the RF had a specificity of 87.6% (95% confidence interval [CI] = 84.4-90.8; positive likelihood ratio [LR+] 5.7). Specificity at 2 and 3 times above the upper limit of normal (ULN) increased to 96.2% (95% CI = 94.3-98.1; LR+ 15.7) and 97.1% (95% CI = 95.5-98.7; LR+ 17.1), respectively.The specificity of ACPA at the positive cutoff level was 94.4% (95% CI = 92.2-96.6; LR+ 12.7), which increased to 98% (95% CI = 96.6-99.4), at 2xULN level. The likelihood ratio for ACPA at all cutoff levels measured was more than 10.

Conclusion

The sensitivity and specificity of RF and ACPA in our study population are comparable with those of other studies. ACPA at lower titers may have sufficient diagnostic utility for RA in an appropriate clinical setting.

STXBP6 and B3GNT6 Genes are Associated With Selective IgA Deficiency

Immunoglobulin A Deficiency (IgAD) is a polygenic primary immune deficiency, with a strong genetic association to the human leukocyte antigen (HLA) region. Previous genome-wide association studies (GWAS) have identified five non-HLA risk loci (IFIH1, PVT1, ATG13-AMBRA1, AHI1 and CLEC16A). In this study, we investigated the genetic interactions between different HLA susceptibility haplotypes and non-MHC genes in IgAD. To do this, we stratified IgAD subjects and healthy controls based on HLA haplotypes (N = 10,993), and then performed GWAS to identify novel genetic regions contributing to IgAD susceptibility. After replicating previously published HLA risk haplotypes, we compared individuals carrying at least one HLA risk allele (HLA-B*08:01-DRB1*03:01-DQB1*02:01 or HLA-DRB1*07:01-DQB1*02:02 or HLA-DRB1*01-DQB1*05:01) with individuals lacking an HLA risk allele. Subsequently, we stratified subjects based on the susceptibility alleles/haplotypes and performed gene-based association analysis using 572,856 SNPs and 24,125 genes. A significant genome-wide association in STXBP6 (rs4097492; p = 7.63 × 10^-9) was observed in the cohort carrying at least one MHC risk allele. We also identified a significant gene-based association for B3GNT6 (P _Gene = 2.1 × 10^-6) in patients not carrying known HLA susceptibility alleles. Our findings indicate that the etiology of IgAD differs depending on the genetic background of HLA susceptibility haplotypes.

Literature review of rheumatoid arthritis in India

AIM

Rheumatoid arthritis (RA) can lead to severe disability. This literature review assessed the descriptive epidemiology, comorbidities and extra-articular manifestations, functioning abilities and quality of life, and treatment patterns of RA patients in India.

METHOD

A literature review of all observational studies published from 1985 to 2012 was conducted using MEDLINE and Embase. Quantitative and qualitative findings were summarized.

RESULTS

Twenty-eight studies were identified for data extraction. Seven described the descriptive epidemiology of RA, 14 described comorbidities and extra-articular manifestations, nine described the functioning abilities and quality of life among patients, and 10 provided information on treatments.

CONCLUSION

This review is confined to studies with small sample sizes, cross-sectional designs, and/or clinical settings that may not be representative of the entire Indian population. There is a need for more robust studies, as conclusions for the entire Indian RA population cannot be drawn from only the current observational studies.

Challenges in the pursuit of immune tolerance

Strategies for inducing immune tolerance are fundamentally similar across a spectrum of immune-mediated disorders, including allergic disease, autoimmunity, and rejection of allografts. In each case, the objective of establishing an immunoregulatory balance is challenged by variable upswings in effector cell populations and proinflammatory mediators of immunity, requiring careful, and innovative therapeutic intervention to restore stability. The Immune Tolerance Network, an international consortium sponsored by the National Institutes of Health, seeks to advance both the scientific understanding and the clinical success of immune therapies for these disorders, through an innovative and collaborative effort involving clinical trials and mechanistic studies. Over the last decade, scientists have evaluated cell-based ablation and deviation strategies in trials using lymphocyte-specific targeting, induction of host-donor hematopoietic chimerism, induction of antigen-specific immune regulation, and a variety of antigen desensitization approaches. In this article, we review some of the highlights of this experience and discuss the potential for progress, utilizing new insights into regulatory mechanisms and biomarker signatures of tolerance.

Association of rheumatoid arthritis with HLA-DR1 and HLA-DR4 in Hungary

Susceptibility to and outcome for rheumatoid arthritis (RA) have been associated with particular HLA-DR alleles, but these alleles vary among ethnic groups and geographic areas. The frequency of HLA-DR1 (HLA-DRB1*0101, DRB1*0102) and HLA-DR4 (DRB1*0401, DRB1*0404) alleles is elevated among Caucasian patients with RA. We studied a northeastern Hungarian population of RA patients to determine the frequency of HLA-DR1 and HLA-DR4 phenotypes in this population and to compare it with healthy control subjects, as well as to investigate whether the presence of these alleles could be a marker for RA. We performed HLA-DRB1 genotyping (DRB1*01-DRB1*16) in 83 RA patients and 55 healthy controls using polymerase chain reaction with sequence-specific primers (PCR-SSP). In the case of HLA-DR1- or HLA-DR4-positive patients, the DR1 and DR4 subtypes were also determined. The frequency of HLA-DR4 alleles was significantly higher in RA patients than in controls (31.3 vs. 10.9%; P <.05). HLA-DR1, in particular, tended to be more frequent in patients than in controls (32.5 vs. 18.1%). Among the HLA-DR4 subtypes, DRB1*0401 and DRB1*0404 were the most common alleles found in both groups. However, no significant differences were seen in the frequency of HLA-DRB1*0401 and HLA-DRB1*0404 between RA patients and controls. In contrast, HLA-DRB1*0405 and HLA-DRB1*0408 were significantly more common in RA patients than in control subjects. Among HLA-DR1 subtypes, the DRB1*0101 allele was most commonly detected, but HLA-DRB1*0101 as well as DRB1*0102 and DRB1*0105 were similarly frequent in RA patients and controls. HLA-DR12 was more common among controls than in RA patients (18.1 vs. 0%; P <.05). Our results generally agree with the findings in other Caucasian populations. Nonetheless, we found differences in the frequency of HLA-DR1 and HLA-DR4 subtypes among Hungarian patients compared with reports from other geographic regions (e.g., Finland and Asia). Our data suggest that in northeastern Hungary, HLA-DR4 as well as its subtypes DRB1*0405 and DRB1*0408 may be involved in susceptibility to RA, but HLA-DR1 may not. In addition, the presence of HLA-DR12, at least in Hungary, may protect from this disease.

Genetic studies, clinical heterogeneity, and disease outcome studies in rheumatoid arthritis

HLA haplotypes influence various clinical RA features considered to reflect severity in case-control and cohort studies. Of particular note is the fact that HLA generally influences the development of erosive and sometimes seropositive and nodular disease; in prospective studies, it noticeably affects joint surgical intervention. These are valuable clues indicating that HLA influences RA severity and chronicity. Nevertheless, HLA influences are generally weak enough so as to require large study subject numbers for detection. As a result, HLA genotyping has restricted usefulness for prediction of clinical severity in individual patients.

HLA class II association with rheumatoid arthritis: facts and interpretations

We have reviewed the literature on the association of HLA class II with rheumatoid arthritis (RA). Strong linkage disequilibrium among DQB1, DQA1 and DRB1 alleles makes it difficult to evaluate the individual contribution of each locus. Nonetheless, there is a strong case for the role of DQB1*03 and *04 combined with DQA1*03 in susceptibility to severe RA while DQB1*0501 combined with DQA1*0101 and *0104 weakly predisposes to a mild form of RA. However, it is also clear that DRB1*0401 has a particular role in predisposition to the most severe form of the disease while other DRB1 alleles might provide protection. We would like to propose that in RA, as in type I diabetes, both DQ and DR loci contribute to predisposition to the disease.

HLA-DRB1 alleles associated with susceptibility or resistance to rheumatoid arthritis, articular deformities, and disability in Mexican Americans

OBJECTIVE

To study the genetics (HLA-DRB1 allele associations) of rheumatoid arthritis (RA) susceptibility and severity among Mexican Americans, an important, but understudied, US population.

METHODS

HLA-DRB1 alleles were compared between 141 Mexican American patients with RA and 54 unrelated Mexican Americans without RA, and the association of these alleles with articular deformities and disability was examined. HLA-DRB1 alleles were typed using polymerase chain reaction-sequence-specific primer amplification and were classified according to the 1996 World Health Organization nomenclature.

RESULTS

Of the 141 patients, 105 (74%) had at least 1 copy of the shared epitope (SE) sequence, compared with 29 (54%) of the 54 controls (P = 0.007). A significant gene-dose effect was observed, with 31 patients (22%) being homozygous for the SE compared with 1 (2%) of the controls (P = 0.004). In terms of disease severity, only 3% of RA patients who were "null" for the SE were outliers in the rate of development of articular deformities, compared with 10% of heterozygotes and 27% of homozygotes (P = 0.002). Patients who were DRB1*08 positive had significantly fewer deformities per year of disease and a slower rate of development of disability than did patients with other DRB1 alleles.

CONCLUSION

HLA-DRB1 alleles containing the SE are associated with susceptibility to RA in Mexican Americans, and may also be associated with a more rapid development of articular deformities and disability. HLA-DRB1*08 appears to have a protective influence on RA susceptibility and disease severity in Mexican Americans.

HLA-DQ-associated predisposition to and dominant HLA-DR-associated protection against rheumatoid arthritis

We have recently proposed a new hypothesis to explain the association of Human Leukocyte Antigen (HLA) with rheumatoid arthritis (RA) predisposition. In this model, which challenges the Shared Epitope (SE) hypothesis, HLA-DQ predisposes while HLA-DR protects. In the present study, we have compared these two models in an Early Arthritis Clinic started in 1993 in the Department of Rheumatology at the Leiden University Medical Centre. Out of 524 patients who enrolled this programme in the period 1993-1998 and completed the one year follow-up, 155 have been classified as RA. These patients along with 306 consecutive cadaveric renal organ donors have been typed for HLA-DR and -DQ. The distributions of predisposing DR alleles according to SE, and predisposing DQ and protective DR according to our model were analysed. We found that two doses of predisposing DQ alleles strongly predisposed to RA, even in individuals with a single dose of SE while DRB1 alleles carrying the motif DERAA confered a dominant protection in DQ5-positive individuals. We conclude that the present findings are consistent with our previously described model of HLA and RA association. Using this new model, we have been able to characterise two novel groups of individuals on the basis of their HLA typing: one strongly predisposed to RA and one protected. Knowing the mechanism of HLA-related dominant natural protection may help in designing novel treatment modalities for RA.

Peptic ulcer disease in the 1990s: an Asian perspective

Peptic ulcer disease is still a common disease in many parts of Asia, although it is less common today than it was 2-3 decades ago. Contrary to this general trend, peptic ulcers are on the rise in the elderly, particularly elderly females. Two important factors that could explain the observed changes in the trends of peptic ulcer disease are: Helicobacter pylori and NSAID. The seroprevalence of H. pylori, determined in three previous studies, would appear to have decreased over the last few decades, while NSAID and aspirin are used increasingly for arthritis, cerebrovascular disease and coronary artery disease. The major complication of peptic ulcer disease is gastrointestinal haemorrhage and in the 1990s endoscopic haemostatic therapy has replaced surgery as the treatment of choice. Treatment of peptic ulcer disease caused by H. pylori is directed at eradication of H. pylori itself; four classes of drug regimens are currently available for this. Antibiotic resistance, particularly metronidazole resistance, is an important factor that determines the outcome of therapy. Metronidazole resistance is reported to be present in 50% of all strains of H. pylori in Hong Kong and Singapore, and is present in 80-90% of all strains in India. Eradication rates in Asia, may for this reason, differ from those in the West, if the regimen contains metronidazole. Treatment of NSAID-associated ulcer consists of discontinuation of NSAID, if possible, and administration of anti-secretory drugs such as H2 blockers, proton pump inhibitors or mucosal protective agents. Co-prescription with misoprostol has been shown to reduce the risk of NSAID-induced ulcer. New NSAID or NO NSAID are being developed with few gastrointestinal side effects.

Immune response of HLA-DQ8 transgenic mice to peptides from the third hypervariable region of HLA-DRB1 correlates with predisposition to rheumatoid arthritis

The major histocompatibility complex class II genes play an important role in the genetic predisposition to many autoimmune diseases. In the case of rheumatoid arthritis (RA), the human leukocyte antigen (HLA)-DRB1 locus has been implicated in the disease predisposition. The "shared epitope" hypothesis predicts that similar motifs within the third hypervariable (HV3) regions of some HLA-DRB1 alleles are responsible for the class II-associated predisposition to RA. Using a line of transgenic mice expressing the DQB1*0302/DQA1*0301 (DQ8) genes in the absence of endogenous mouse class II molecules, we have analyzed the antigenicity of peptides covering the HV3 regions of RA-associated and nonassociated DRB1 molecules. Our results show that a correlation exists between proliferative response to peptides derived from the HV3 regions of DRB1 chains and nonassociation of the corresponding alleles with RA predisposition. While HV3 peptides derived from nonassociated DRB1 molecules are highly immunogenic in DQ8 transgenic mice, all the HV3 peptides derived from RA-associated DRB1 alleles fail to induce a DQ8-restricted T-cell response. These data suggest that the role of the "shared epitope" in RA predisposition may be through the shaping of the T-cell repertoire.

Extraarticular manifestations of rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic inflammatory disease that can involve other tissues and organs as well as synovial joints. This chapter reviews the clinical aspects of extra-articular RA, from the early descriptions in rheumatology texts to reports from more recent cross-sectional and inception cohort studies. There is no agreed classification for these manifestations and, because criteria and definitions vary so much, this report includes not only the classic extra-articular features but also the non-articular complications of RA, for example normochromic normocytic anaemia and chronic leg ulcers, and the important disease-associated comorbidities, including non-Hodgkin's lymphoma, ischaemic heart disease and osteoporosis. Incidence and frequency figures for extra-articular RA vary according to study design. Nodules are the most common extra-articular feature, and are present in up to 30%; many of the other classic features occur in 1% or less in normal clinic settings. Sjögren's syndrome, anaemia of chronic disease and pulmonary manifestations are relatively common - in 6-10% - are frequently present in early disease and are all related to worse outcomes measures of rheumatoid disease, in particular functional impairment and mortality. Currently, there are no reliable predictors for these features in early RA, although they are associated with men, smokers, more severe joint disease, worse function, high levels of inflammatory markers, and the presence of rheumatoid factor (RF), antinuclear antibodies (ANA) and the RA HLA-related shared epitope. Many of these manifestations are related to the more active and severe RA, so early and more aggressive RA drug therapies are being employed and, although evidence from randomised studies is not available, this approach would seem appropriate in view of the adverse effect of extra-articular manifestations on RA outcomes. Unfortunately, specific therapies for extra-articular manifestations of RA are largely disappointing or unavailable, except for steroids and cyclophosphamide for vasculitis. The place for biological therapies is still not clear. Pulmonary fibrosis in RA has a poor prognosis whether treated with large doses of steroids, cytotoxic or disease modifying drugs like cyclosporine, or biologics. In summary, extra-articular features and non-articular complications of RA are common and are generally related to worse disease. They need to be recognised early and managed promptly.