HLA haplotypes in non-familial rheumatoid arthritis

Polymorphism in the tumor necrosis factor-alpha gene promoter is associated with severity of rheumatoid arthritis in the Czech population

Rheumatoid arthritis (RA) is a model of multigenic inflammatory disorder in which tumor necrosis factor-alpha (TNF-alpha) plays an important role. Genetic factors may be implicated in the susceptibility to disease initiation as well as in severity of disease course. Elevated levels of TNF-alpha in the plasma and synovial fluid from RA patients may be associated with polymorphisms in the promoter region of the TNF-alpha gene. The aim of this study was to elucidate putative association between the -308 G/A polymorphism in the promoter region of the TNF-alpha gene and susceptibility to onset and severity of RA. A total of 130 RA patients and a control group of 150 healthy subjects with similar age and sex distribution were available for the study. All patients fulfilled the American College of Rheumatology revised criteria for RA. RA patients had a disease duration of at least 2 years. Radiographs of both hands of all RA patients were scored with the Steinbrocker method. There were 15 patients of stage I (nonerosive form) of RA and 114 patients of stages II-IV (erosive form). To assess the RA patient's functional ability, the Health Assessment Questionnaire (HAQ) was used. The -308 G/A promoter polymorphism of the TNF-alpha gene was detected by polymerase chain reaction and restriction fragment length polymorphism analysis. No differences in genotype distribution and allelic frequences of -308 G/A TNF-alpha promoter polymorphism have been found between RA patients and the control group. Significant differences have been observed within the RA group divided according to the radiographic progression of disease based on the Steinbrocker radiographic score and functional ability (HAQ). These results suggest an association of the -308 G/A polymorphism of the TNF-alpha gene with the severity of RA.

Association of HLA-DR3 with anti-cyclic citrullinated peptide antibody-negative rheumatoid arthritis

OBJECTIVE

Recent data have shown that the most prominent and longest known genetic risk factors for rheumatoid arthritis (RA), HLA-DRB1 shared epitope alleles, are only associated with RA that is characterized by the presence of antibodies against cyclic citrullinated peptide (anti-CCP antibodies) and not with anti-CCP-negative RA. We undertook this study to investigate whether anti-CCP-negative RA is associated with other HLA-DRB1 alleles.

METHODS

HLA typing was performed for 377 patients from the Leiden Early Arthritis Clinic who were diagnosed as having RA within the first year of followup (206 anti-CCP-positive patients and 171 anti-CCP-negative patients), 235 patients who, after 1 year, had undifferentiated arthritis (UA) (28 anti-CCP-positive patients and 207 anti-CCP-negative patients), and 423 healthy control subjects. Odds ratios (ORs) with 95% confidence intervals (95% CIs) for HLA-DRB1 allele frequencies were determined for all patient groups compared with the healthy control group.

RESULTS

HLA-DR3 was more frequently present in the anti-CCP-negative RA group than in the control group (OR 1.84, 95% CI 1.26-2.67). This was not the case for anti-CCP-positive RA (OR 0.92, 95% CI 0.60-1.40). HLA-DR3 was also more frequently present in anti-CCP-negative UA patients (OR 1.59, 95% CI 1.10-2.28), but not in anti-CCP-positive UA patients (OR 0.68, 95% CI 0.17-1.92).

CONCLUSION

HLA-DR3 is associated with anti-CCP-negative arthritis and not with anti-CCP-positive arthritis. These data show that distinct genetic risk factors are associated with the presence of anti-CCP antibodies in RA and indicate that different pathogenetic mechanisms underlie anti-CCP-positive and anti-CCP-negative RA.

Redefining the HLA and RA association: to be or not to be anti-CCP positive

Rheumatoid Arthritis (RA) is the most common chronic inflammatory joint disease. The overall prevalence is 1% and in people older than 60 it is more than 2%. RA has auto-immune features: auto-antibodies against the Fc part of IgG, so-called Rheumatoid Factor (RF) are found more often in RA patients and more recently RA-specific auto-antibodies directed against Cyclic Citrunilated Peptides (CCP) have been discovered. Based on twin studies the contribution of genetic factors to the pathogenesis has been estimated to be about 60%. The main genetic contribution (about 40%) comes from the HLA complex. An association between HLA-DR4 and RA was already documented almost 30 years ago. This association was more prominent for severe forms of the disease. Because more HLA-DRB1 alleles appeared to be associated with RA and the products of these alleles shared a 5AA sequence in a peptide-binding pocket the so-called Shared Epitope (SE) hypothesis was formulated, the prediction being that these DRB1 molecules would bind an RA inducing peptide(s). Thus far however such (a) peptides remain elusive. Because the risk for RA associated with different but SE-identical DRB1 alleles varies considerably this SE can also not be the whole explanation for the HLA contribution to RA susceptibility/severity. A modified SE has been postulated and a role for DQ has been postulated. There is also evidence for a contribution of non-class II genes to susceptibility. About 5 years ago we have reported that certain HLA-DRB1 alleles are associated with protection from (severe) RA. The products of these alleles carry instead of the SE sequence another peptide anchor region consisting of the amino acid DERAA. In a large prospective cohort study we showed recently that these alleles indeed confer (dominant) protection both against developing RA and a severe course of the disease. This protection was observed both in the presence and the absence of SE susceptibility alleles. We are presently exploring the hypothesis that this protection is mediated by regulatory T cells reactive with the DERAA epitope. An obvious way to unravel the apparently complex association between HLA and RA is to reduce the heterogeneity of this multifactorial disease. Recently, we have discovered that SE positive DRB1 alleles are exclusively associated with CCP positive RA. The previously reported association with RF positive RA appeared to be secondary to the association with anti-CCP pos. RA. This was the case both for the association found for susceptibility and severity. Interestingly, DRB1*03 was exclusively associated with anti-CCP neg. RA. Because recent evidence puts the immune response against citrunilated proteins (CCP) as prime suspect for disease induction and progression in this subgroup of RA these observations are a big leap forwards in solving the HLA-RA puzzle.

Human leukocyte antigen-DRB1*1502 (DR2Dw12) transgene reduces incidence and severity of arthritis in mice

A strong correlation exists between susceptibility to RA in humans and some DRB1 alleles of the MHC region, such as DRB1*0401 and DRB1*0101. Meanwhile, incidences of other DR specificities, such as DR2, DR5, or DR7 have often been found reduced among RA patients. Like RA, susceptibility to mouse CIA is influenced by the MHC class II loci. To analyze the effect of a DRB1 molecule associated with low incidence of RA on mouse CIA, a human DRB1*1502 (DR2Dw12) transgene was introduced into CIA-susceptible B10.RQB3 (H2Aq) mice. Transgene-positive DRB1*1502 mice showed a significant reduction in the incidence and severity of arthritis. Moreover, the clinical reduction of arthritis correlated with the T-cell proliferative response of B10.RQB3-DRB1*1502 mice against a self-derived DRB1 peptide from the third hypervariable region. Our results suggest that the DRB1*1502-mediated protection against CIA can be explained by the DRB1 molecule acting as a source of self-antigenic peptide which interferes with the T-cell response against immunodominant regions(s) of the arthritogenic type II collagen molecule. By analogy, a similar mechanism might play a critical role in influencing the class II-associated predisposition to RA.

Polymorphism of HLA-DRB, -DQA1, and -DQB1 in rheumatoid arthritis in Asian Indians: association with DRB1*0405 and DRB1*1001

We investigated the DRB, DQA1, and DQB 1 polymorphism and haplotypes in sporadic and familial RA subjects of Asian Indian origin by PCR oligotyping using biotinylated SSOPs. Molecular subtyping of DRB 1*04 in RA patients showed strongest association with highest relative risk with DRB 1*0405, followed by DRBI*0401. A significant decreased frequency of DRBI*1502 was observed in patients compared to controls (chi 2 = 4.5). Among other alleles, DRBI*1001 was found to be significantly increased. A total of 73.3% of patients carried the shared sequence of the third HVR (67-74) of DRB1 domain compared to its presence in only 37.6% of controls. A significant number of patients carried DR4 haplotypes on DQBI*0302 (58%) as against DQBI*0301 which was present only on 10.5% of the haplotypes. When compared to controls, the difference was significant for the latter allele only. Few unique DRDQ haplotypes were observed in Asian Indians. Among DR-DQ haplotypes, DRB1*0401-DQB1*0302 gave the highest risk whereas DRB1*0403-DQB1*O301 was negatively associated. Alleles with negative charge at position 70 confer protection or are negatively associated with RA whereas among the associated alleles, glycine at position 86 resulted in higher risk than those with valine at this position. A heterogenous association of DQB1 alleles with DR4 subtypes, influencing susceptibility to RA, suggests the DQB locus is not primarily associated with RA and susceptibility lies in the sequence 67-74 of the DRB1 loci.