Genetic epidemiology of rheumatoid arthritis

Chlamydia pneumoniae: An Etiologic Agent for Late-Onset Dementia

The disease known as late-onset Alzheimer's disease is a neurodegenerative condition recognized as the single most commonform of senile dementia. The condition is sporadic and has been attributed to neuronal damage and loss, both of which have been linked to the accumulation of protein deposits in the brain. Significant progress has been made over the past two decades regarding our overall understanding of the apparently pathogenic entities that arise in the affected brain, both for early-onset disease, which constitutes approximately 5% of all cases, as well as late-onset disease, which constitutes the remainder of cases. Observable neuropathology includes: neurofibrillary tangles, neuropil threads, neuritic senile plaques and often deposits of amyloid around the cerebrovasculature. Although many studies have provided a relatively detailed knowledge of these putatively pathogenic entities, understanding of the events that initiate and support the biological processes generating them and the subsequent observable neuropathology and neurodegeneration remain limited. This is especially true in the case of late-onset disease. Although early-onset Alzheimer's disease has been shown conclusively to have genetic roots, the detailed etiologic initiation of late-onset disease without such genetic origins has remained elusive. Over the last 15 years, current and ongoing work has implicated infection in the etiology and pathogenesis of late-onset dementia. Infectious agents reported to be associated with disease initiation are various, including several viruses and pathogenic bacterial species. We have reported extensively regarding an association between late-onset disease and infection with the intracellular bacterial pathogen Chlamydia pneumoniae. In this article, we review previously published data and recent results that support involvement of this unusual respiratory pathogen in disease induction and development. We further suggest several areas for future research that should elucidate details relating to those processes, and we argue for a change in the designation of the disease based on increased understanding of its clinical attributes.

Crosslinks Between Human Leukocyte Antigen DRB1*01 and Human Leukocyte Antigen DRB1*13 Allelic Variants and Occurrence of Rheumatoid Arthritis in Patients From Federation of Bosnia and Herzegovina

Objectives

This study aims to analyze human leukocyte antigen A (HLA-A), human leukocyte antigen B (HLA-B), human leukocyte antigen C (HLA-C), HLA-DRB1*, HLA-DRB3*, HLA-DRB4*, HLA-DRB5*, HLA-DQB1* loci expression in patients with rheumatoid arthritis (RA) in the Federation of Bosnia and Herzegovina.

Patients and methods

Deoxyribonucleic acid was isolated from peripheral blood of 48 RA patients (22 males, 26 females; mean age 36 years; range 2 to 63 years) and 104 healthy control individuals (52 males, 52 females; mean age 43 years; range 2 to 76 years). Deoxyribonucleic acid samples were analyzed using polymerase chain reaction-sequence-specific primers and sequence specific oligonucleotides methods.

Results

The most frequent allelic groups in RA patients were HLA-DRB1*01 (odds ratio=2.795; 95% confidence interval: 1.441-5.421; p=0.004) and HLA-DRB1*04 (odds ratio=2.573; 95% confidence interval: 1.214-5.453; p=0.023). Among RA patients, the most frequent genotype for the allelic group HLA-DRB1*, in the light of the common epitopes theory, was observed for DRB1*01/DRB1*13. This genotype indicates an increased incidence and relative risk (odds ratio=11.09).

Conclusion

The most common genotype in our RA patients was DRB1*01/DRB1*13, which showed increased frequency and a high relative risk. This genotype variant may be considered a predisposing factor for the development of RA.

The recurrence risk of genetic complex diseases

Complex inherited diseases affected by an interaction between collective effects of the genotype at one or multiple loci either to increase or to lower susceptibility to disease, combined with a variety of environmental exposures that may trigger, accelerate, exacerbate, or protect against the disease process. The new aspects of genetic techniques have been opened for diagnosis and analysis of inherited disorders. While appropriate Mendelian laws is applied to estimate the recurrence risk of single gene diseases, using empirical recurrence risks are the most important and available method to evaluate pedigree of complex (multifactorial), chromosomal, and unknown etiology disorders. Although, generally, empirical recurrent risks are not accurate, either because of the difference of gene frequencies and environmental factors among populations or heterogeneity of disease; using results of plenty family population studies, computerized estimating programs, genotyping technologies, and Genome-wide association studies (GWASs) of single nucleotide polymorphisms (SNPs), can make it possible nowadays to estimate these risks. The specific family situation and importance recurrence risks of some common complex genetic diseases will be presented in this review and some important multifactorial disorders’ recurrence risks will be summarized to help genetic counselors for supporting families and representing better view of genetic disorders.

PAD4: pathophysiology, current therapeutics and future perspective in rheumatoid arthritis

INTRODUCTION

Peptidyl arginine deiminase 4 (PAD4) is an enzyme that plays an important role in gene expression, turning out genetic code into functional products in the body. It is involved in a key post translational modification, which involves the conversion of arginine to citrulline. It regulates various processes such as apoptosis, innate immunity and pluripotency, while its dysregulation has a great impact on the genesis of various diseases. Over the last few years PAD4 has emerged as a potential therapeutic target for the treatment of rheumatoid arthritis (RA). Areas covered: In this review, we discuss the basic structure and function of PAD4, along with the role of altered PAD4 activity in the onset of RA and other maladies. We also elucidate the role of PAD4 variants in etiology of RA among several ethnic groups and the current pre-clinical inhibitors to regulate PAD4. Expert opinion: Citrullination has a crucial role in RA and several other disorders. Since PAD4 is an initiator of the citrullination, it is an important therapeutic target for inflammatory diseases. Therefore, an in depth knowledge of the roles and activity of PAD4 is required to explore more effective ways to conquer PAD4 related ailments, especially RA.

TCR-CD3ζ gene polymorphisms and expression profile in rheumatoid arthritis

OBJECTIVES

Recent evidence has demonstrated that CD3ζ (also called CD247) play a vital role in multiple autoimmune diseases. In this study, we explored the association between CD247 gene single-nucleotide polymorphisms (SNPs) and rheumatoid arthritis (RA) in a Chinese Han population. We also evaluated the CD3ζ expression profile in peripheral blood mononuclear cells (PBMCs) from patients with RA and health controls.

METHODS

Three CD247 polymorphisms (rs704853, rs1214611 and rs858554) were studied in 612 patients with RA and 848 controls in a Chinese population. Genotyping was performed using the Fluidigm 192.24 Dynamic Array™ Integrated Fluidic Circuit (IFC). For gene expression study, CD3ζ mRNA levels of 36 patients with RA and 39 healthy individuals were assessed by real-time polymerase chain reaction (RT-PCR). Data were analyzed by SPSS 11.5 software.

RESULTS

A significant association between rs858554 polymorphism and RA was found under all genetic models (all p < 0.05). Moreover, we found the genotype distribution and allele frequency of rs858554 were significant associated with ACCP⁺ and RF⁺ phenotype as compare to health controls (all p < 0.05). Unfortunately, we did not detect any significant associations between rs704853, rs1214611 and RA susceptibility and autoantibody profiles (all p > 0.05). The gene expression assays showed that CD3ζ mRNA levels were downregulated in PBMCs of patients with RA when compared to healthy controls.

CONCLUSIONS

Our results, the first reported for distinct Chinese populations, support a role of the CD247 gene in the susceptibility to RA. Further studies with more sample size are necessary to clarify the exact role of CD247 gene in the pathogenesis of RA.

Analysis of four serum biomarkers in rheumatoid arthritis: association with extra articular manifestations in patients and arthralgia in relatives

OBJECTIVES

To evaluate the frequency of four serum biomarkers in RA patients and their relatives and identify possible associations with clinical findings of the disease.

METHODS

This was a transversal analytical study. Anti-cyclic citrullinated peptide (anti-CCP), anti-mutated citrullinated vimentin (anti-MCV) and IgA-rheumatoid factor (RF) were determined by ELISA and IgM-RF by latex agglutination in 210 RA patients, 198 relatives and 92 healthy controls from Southern Brazil. Clinical and demographic data were obtained through charts review and questionnaires.

RESULTS

A higher positivity for all antibodies was observed in RA patients when compared to relatives and controls (p<0.0001). IgA-RF was more frequent in relatives compared to controls (14.6% vs. 5.4%, p=0.03, OR=2.98; 95% CI=1.11-7.98) whereas anti-CCP was the most common biomarker among RA patients (75.6%). Concomitant positivity for the four biomarkers was more common in patients (46.2%, p<0.0001). Relatives and controls were mostly positive for just one biomarker (20.2%, p<0.0001 and 15.2%, p=0.016, respectively). No association was observed between the number of positive biomarkers and age of disease onset, functional class or tobacco exposure. In seronegative patients predominate absence of extra articular manifestations (EAMs) (p=0.01; OR=3.25; 95% CI=1.16-10.66). Arthralgia was present in positive relatives, regardless the type of biomarker.

CONCLUSIONS

A higher number of biomarkers was present in RA patients with EAMs. Positivity of biomarkers was related to arthralgia in relatives. These findings reinforce the link between distinct biomarkers and the pathophysiologic mechanisms of AR.

Sex Differences in Genetic and Environmental Influences on Longitudinal Change in Functional Ability in Late Adulthood

OBJECTIVES

To determine the extent to which genetic and environmental factors contribute to individual and gender differences in aging of functional ability.

METHOD

Twenty assessments of functional ability are collected as part of the longitudinal Swedish Adoption/Twin Study of Aging from 859 twins aged 50-88 at the first wave. Participants completed up to 6 assessments covering a 19-year period. Factor analysis was used to create 3 factors: flexibility, fine motor skills, and balance.

RESULTS

Latent growth curve analysis demonstrated increasing disability and variability after age 70. For flexibility, results indicated significant sex differences in mean change trajectories but no sex differences in components of variance. No sex differences were found for fine motor movement. For balance, there were no sex differences in mean change trajectories; however, there was significant genetic variance for changes in balance in women after age 70 but not for men.

DISCUSSION

Although idiosyncratic environmental influences account for a large part of increasing variance, correlated and shared rearing environmental effects were also evident. Thus, both microenvironmental (individual) and macroenvironmental (family and cultural) effects, as well as genetic factors, affect maintenance of functional ability in late adulthood.

Association of interleukin-18 (-137G/C) polymorphism with rheumatoid arthritis and systemic lupus erythematosus: a meta-analysis

BACKGROUND

Recent studies have suggested that interleukin (IL)-18 gene (-137G/C) polymorphism is associated with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). However, other studies did not confirm this correlation.

OBJECTIVE

The objective of this study was to evaluate the relationships of IL-18 -137G/C and RA and SLE using a meta-analysis.

METHODS

Pubmed, Embase and Cochrane library databases were systemically searched. Data were extracted by two independent reviewers and pooled odds ratio (OR) with 95% confidence interval (CI) was calculated.

RESULTS

In RA, the overall ORs and 95% CIs of -137C were 1.03, 0.88-1.22 (p=0.391); 1.22, 0.89-1.68 (p=0.020) and 1.06, 0.93-1.21 (p=0.110) in dominant, recessive, and additive models, respectively. Furthermore, in SLE, the overall ORs and 95% CIs of -137C were 1.10, 0.94-1.29 (p=0.980); 1.21, 0.91-1.60 (p=0.010) and 1.10, 0.97-1.24 (p=0.454) in dominant, recessive, and additive models, respectively. IL-18 -137G/C could increase the risk of RA and SLE. No publication bias was found in this meta-analysis. After population stratification analysis, under recessive model, the pooled ORs and 95% CIs of -137C were 1.14, 0.82-1.60 (p=0.008) and 1.01, 0.66-1.55 (p=0.004) in European RA patients and Asian SLE patients, respectively.

CONCLUSIONS

This meta-analysis showed that IL-18 -137G/C was a risk factor for RA and SLE, especially for RA in Europeans and SLE in Asians.

The impact of improved microarray coverage and larger sample sizes on future genome-wide association studies

Genome-wide association studies (GWAS) have identified many single nucleotide polymorphisms (SNPs) associated with complex traits. However, the genetic heritability of most of these traits remains unexplained. To help guide future studies, we address the crucial question of whether future GWAS can detect new SNP associations and explain additional heritability given the new availability of larger GWAS SNP arrays, imputation, and reduced genotyping costs. We first describe the pairwise and imputation coverage of all SNPs in the human genome by commercially available GWAS SNP arrays, using the 1000 Genomes Project as a reference. Next, we describe the findings from 6 years of GWAS of 172 chronic diseases, calculating the power to detect each of them while taking array coverage and sample size into account. We then calculate the power to detect these SNP associations under different conditions using improved coverage and/or sample sizes. Finally, we estimate the percentages of SNP associations and heritability previously detected and detectable by future GWAS under each condition. Overall, we estimated that previous GWAS have detected less than one-fifth of all GWAS-detectable SNPs underlying chronic disease. Furthermore, increasing sample size has a much larger impact than increasing coverage on the potential of future GWAS to detect additional SNP-disease associations and heritability.

Associations of HLA-DRB1 alleles with anti-citrullinated protein antibody-positive and anti-citrullinated protein antibody-negative rheumatoid arthritis in northern east part of Turkey

AIM

The aim of this study was to investigate the associations between human leukocyte antigen (HLA)-DRB1 alleles with genetic susceptibility to rheumatoid arthritis (RA) and production of antibodies against cyclic citrullinated peptide (anti-CCP antibody) and rheumatoid factor (RF) in Turkish RA patients.

METHODS

We studied 291 RA patients and 253 controls. Genotyping was performed by polymerase chain reaction with sequence-specific oligonucleotide probes hybridization method. Serum levels of anti-CCP antibody, IgM-RF and high sensitive C-reactive protein titers were measured by commercial kits using immunological methods.

RESULTS

We found that HLA-DRB1*04 and *09 alleles were associated in anti-CCP+ and anti-CCP+ RA patients (P < 0.0001 and P < 0.001, respectively), while DRB1*01 and *04 were determined to be higher in RF+ RA patients (P < 0.001 and P < 0.0001, respectively). Moreover, DRB1*11 and DRB1*13 alleles were determined to be lower in RF and anti-CCP/RF+ RA patients (P < 0.001 for both). HLA-DRB1*04 was identified as a common responsible allele for susceptibility to the disease in anti-CCP, RF and anti-CCP/RF- RA patients (P = 0.0018, P = 0.0004 and P = 0.0023, respectively). HLA-DRB1*13 allele alone was found to be protective against to anti-CCP+ and RF- RA (P = 0.0003 and P = 0.006, respectively). On the contrary, there was no protective allele in anti-CCP/RF- RA as well as anti-CCP- RA patients.

CONCLUSION

This study indicates that associate and protective HLA-DRB1 allele distributions are different in autoantibody (anti-CCP or RF or anti-CCP/RF)+ RA and autoantibody- RA patients, with exceptions of DRB1*04 and DRB1*13.

HLA-DRB1 allele distribution and its relation to rheumatoid arthritis in eastern Black Sea Turkish population

Rheumatoid arthritis (RA [MIM 180300]) is a complex, polygenic inflammatory autoimmune disease, resulting from interactions between genetic and environmental factors. Some of the RA-associated HLA-DRB1 alleles have shared epitope, but their distribution varies among different racial/ethnic groups. This study was aimed at investigating the distribution of HLA-DRB1 alleles in patients with RA in eastern Black Sea region of Turkey. DNA samples of 320 patients with RA and 360 healthy controls were studied for the determination of HLA-DRB1 allele distribution using PCR-SSP method. The allele frequencies of HLA-DRB1*01, *04, and *09 were higher in patients with RA compared with the controls (P < 0.005, P < 0.0001, and P < 0.01, respectively). On the other hand, in patients with RA, HLA-DRB1*13 allele was lower than the controls (P < 0.001). Of the HLA-DRB1*04 subgroups, *0401 (40.83% vs. 18.75%, P < 0.001) was the most frequent allele in patients with RA, while DRB1*0402 (30.00% vs. 12.50%, P < 0.005) allele in the controls. HLA-DRB1 allele frequencies in the patients with RA and the controls showed Hardy-Weinberg rule compliance. Results of this study indicate that HLA-DRB1*01, *04, and *09 alleles were associated with RA, and HLA-DRB1*13 was protective allele against RA. Among the subgroups of HLA-DRB1*04, *0401 was detected to be RA associated, while *0402 was being protective. These results have some differences compared with previous reports originating from other regions of Turkey.

Anti-cyclic citrullinated peptide antibodies and rheumatoid factor in rheumatoid arthritis patients and relatives from Brazil

OBJECTIVES

To evaluate the prevalence of anti-cyclic citrullinated peptide (anti-CCP) antibodies and RF in RA patients and their relatives from Southern Brazil.

METHODS

Anti-CCP2 and IgM-RF were evaluated in 156 RA patients and 200 relatives. Sera from 100 healthy unrelated individuals were used as control. The anti-CCP2 was detected by ELISA and the IgM-RF using the latex agglutination test.

RESULTS

We identified 117 anti-CCP2 (75%)-positive and 106 RF (67.9%)-positive patients. Anti-CCP2 was increased in relatives (5.5%; 11/200) when compared with unrelated individuals (1%; P = 0.050). Titre of anti-CCP2 in RA patients did not differ from relatives [140.4 (75.7) vs 115.6 (84.2) U, respectively; P = 0.30]. Positive relatives were younger than patients for anti-CCP2 (P = 0.0081), RF (P < 0.001) and both concomitantly (P = 0.012), and although there was no difference for anti-CCP2 positivity according to gender, increased RF positivity and concomitant anti-CCP2/RF were observed in the female relatives (P = 0.067 and 0.082, respectively). No difference regarding the relative degree of tobacco use in relatives was detected. Among the 11 anti-CCP2-positive relatives, 2 females had RA diagnosis established and 6 individuals presented with joint symptoms suggestive of RA.

CONCLUSION

The results demonstrate a significant positivity of anti-CCP2 in relatives of RA patients from Brazil and reinforce the importance of serological tools to identify undiagnosed RA.

The genetic interpretation of area under the ROC curve in genomic profiling

Genome-wide association studies in human populations have facilitated the creation of genomic profiles which combine the effects of many associated genetic variants to predict risk of disease. The area under the receiver operator characteristic (ROC) curve is a well established measure for determining the efficacy of tests in correctly classifying diseased and non-diseased individuals. We use quantitative genetics theory to provide insight into the genetic interpretation of the area under the ROC curve (AUC) when the test classifier is a predictor of genetic risk. Even when the proportion of genetic variance explained by the test is 100%, there is a maximum value for AUC that depends on the genetic epidemiology of the disease, i.e. either the sibling recurrence risk or heritability and disease prevalence. We derive an equation relating maximum AUC to heritability and disease prevalence. The expression can be reversed to calculate the proportion of genetic variance explained given AUC, disease prevalence, and heritability. We use published estimates of disease prevalence and sibling recurrence risk for 17 complex genetic diseases to calculate the proportion of genetic variance that a test must explain to achieve AUC = 0.75; this varied from 0.10 to 0.74. We provide a genetic interpretation of AUC for use with predictors of genetic risk based on genomic profiles. We provide a strategy to estimate proportion of genetic variance explained on the liability scale from estimates of AUC, disease prevalence, and heritability (or sibling recurrence risk) available as an online calculator.

Genome-wide association studies in human populations have facilitated the creation of genomic profiles that combine the effects of many associated genetic variants to predict risk of disease. However, genomic profiles are inherently constrained in their ability to classify diseased from non-diseased individuals dictated by the genetic epidemiology of the disease. In this paper, we use a genetic interpretation to provide insight into the constraints on genomic profiles for risk prediction. We provide a strategy to estimate proportion of genetic variance explained on the liability scale from estimates of AUC, disease prevalence, and heritability available as an online calculator.

Sporadic cases are the norm for complex disease

The results of genome-wide association studies have revealed that most human complex diseases (for example, cancer, diabetes and psychiatric disorders) are affected by a large number of variants, each of which explains a small increase in disease risk, suggesting a pattern of polygenic inheritance. At the same time, it has been argued that most complex diseases are genetically heterogeneous because many sporadic cases are observed, as well as cases with a family history. In this study, under the assumption of polygenic inheritance, we derive the expected proportion of sporadic cases using analytical methods and simulation. We show how the proportion of sporadic cases depends on disease prevalence (K) and heritability on the underlying liability scale (h(L)(2)). We predict the underlying heritability and the proportion of sporadic cases for a range of human complex diseases, and show that this proportion is typically large. For a disease with h(L)(2)=63% and K=0.4%, such as schizophrenia, >83% of proband cases are predicted to be sporadic (no affected first-, second- and third-degree relatives) in typical families (on an average, two children per couple). For the majority of these diseases, a large proportion of sporadic cases is expected under the polygenic model, implying that the observed large proportion of sporadic cases is not informative to the causal mechanism of a complex genetic disease.

Aetiological factors of importance for the development of rheumatoid arthritis

OBJECTIVE

To evaluate exposure to external factors associated with risk or prevention of rheumatoid arthritis (RA).

METHODS

Two hundred and ninety-three incident cases of RA and 1346 population-based referents were included in a case-referent study, in which previous exposure experiences were collected through a postal questionnaire.

RESULTS

An inverse association between RA and additional schooling after compulsory school was seen for men. Current smoking was associated with significantly increased risks of RA for men and women [odds ratio (OR) 2.9, 95% confidence interval (CI) 1.4-6.4, and OR 1.8, 95% CI 1.1-2.9, respectively], as was previous smoking for men (OR 2.3, 95% CI 1.2-4.4). There were also indications of relationships between previous use of a private well and RA in both men and women.

CONCLUSION

Several previously published associations have been reproduced in the present study, which also generates some new hypotheses that suggest further research.

Influence of peptidylarginine deiminase type 4 genotype and shared epitope on clinical characteristics and autoantibody profile of rheumatoid arthritis

BACKGROUND

Recent evidence suggests that distinction of subsets of rheumatoid arthritis (RA) depending on anti-cyclic citrullinated peptide antibody (anti-CCP) status may be helpful in distinguishing distinct aetiopathologies and in predicting the course of disease. HLA-DRB1 shared epitope (SE) and peptidylarginine deiminase type 4 (PADI4) genotype, both of which have been implicated in anti-CCP generation, are assumed to be associated with RA.

OBJECTIVES

To elucidate whether PADI4 affects the clinical characteristics of RA, and whether it would modulate the effect of anti-CCPs on clinical course. The combined effect of SE and PADI4 on autoantibody profile was also analysed.

METHODS

373 patients with RA were studied. SE, padi4_94C>T, rheumatoid factor, anti-CCPs and antinuclear antibodies (ANAs) were determined. Disease severity was characterised by cumulative therapy intensity classified into ordinal categories (CTI-1 to CTI-3) and by Steinbrocker score.

RESULTS

CTI was significantly associated with disease duration, erosive disease, disease activity score (DAS) 28 and anti-CCPs. The association of anti-CCPs with CTI was considerably influenced by padi4_94C>T genotype (C/C: OR(adj) = 0.93, p(adj) = 0.92; C/T: OR(adj) = 2.92, p(adj) = 0.093; T/T: OR(adj) = 15.3, p(adj) = 0.002). Carriage of padi4_94T exhibited a significant trend towards higher Steinbrocker scores in univariate and multivariate analyses. An association of padi4_94C>T with ANAs was observed, with noteworthy differences depending on SE status (SE-: OR(adj) = 6.20, p(adj)<0.04; SE+: OR(adj) = 0.36, p(adj) = 0.02) and significant heterogeneity between the two SE strata (p = 0.006).

CONCLUSIONS

PADI4 genotype in combination with anti-CCPs and SE modulates clinical and serological characteristics of RA.

Transfer of the shared epitope through microchimerism in women with rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is an autoimmune disease that affects mostly women and is associated with HLA-DRB1 genes having in common a shared epitope sequence. In parallel, cells and/or DNA originating from pregnancy (microchimerism) persist for decades and could contribute to autoimmunity. The aim of this study was to examine whether microchimerism may be a source of the shared epitope among women with RA.

METHODS

Women with RA and healthy women who lacked RA-associated genes such as HLA-DRB1*01 (n=33 and n=46, respectively) and/or HLA-DRB1*04 (n=48 and n=64, respectively), were tested for DRB1*01 or DRB1*04 microchimerism by HLA-specific quantitative polymerase chain reaction assays. As controls, alleles not associated with RA (DQB1*02 and DRB1*15/16) were also analyzed.

RESULTS

Compared with healthy women, women (42% with RA had a higher frequency and higher levels of DRB1*04 microchimerism versus 8%; P=0.00002) as well as DRB1*01 microchimerism (30% versus 4%; P=0.0015). Moreover, no difference in microchimerism was observed for alleles not associated with RA.

CONCLUSION

Women with RA had microchimerism with RA-associated HLA alleles, but not with non-RA-associated HLA alleles, more often and at higher levels compared with healthy women. These observations are the first to indicate that microchimerism can contribute to the risk of an autoimmune disease by providing HLA susceptibility alleles.

Mechanisms of disease: genetics of rheumatoid arthritis--ethnic differences in disease-associated genes

Large studies on the genetics of common rheumatic diseases, such as rheumatoid arthritis and systemic lupus erythematosus, have identified multiple polymorphisms related to disease susceptibility, including peptidylarginine deiminase 4 (PADI4) and protein tyrosine phosphatase N22 (PTPN22). Some of the identified genes are associated with multiple autoimmune disorders, and some seem to have unique associations with particular disease entities. Although the molecules encoded by these genes have a primary role in the molecular pathways of autoimmunity, genetic variations and contribution to disease susceptibility seem to vary between ethnic groups. In this Review, we report the findings on genes associated with rheumatoid arthritis and focus on the differences in the frequency of polymorphisms between various ethnic groups.

The constancy of work-related empowerment

OBJECTIVE

This study describes experiences of work empowerment among staff members at the Rheumatism Foundation Hospital in Helsinki, Finland.

METHODS

The data were collected on two occasions in 2004 and 2005 using a structured questionnaire with background variables and items concerning verbal, behavioural and outcome empowerment. The questionnaires were sent to all (n1=115, n2=112) members of multidisciplinary teams at the Rheumatism Foundation Hospital, with the exception of physicians, departmental secretaries and administrative personnel. The response rate at both data collections was 58%. The data were analysed by statistical methods.

RESULTS

No statistically significant differences were seen in work empowerment between the two data collections. Perceptions of work-related empowerment were relatively strong.

CONCLUSIONS

Work-related empowerment appears to be relatively constant and independent of changes in the organization. Indeed there is good reason to ask whether work empowerment is primarily a function of the individual employee's strengths and competencies.

Regulatory polymorphisms in extracellular matrix protease genes and susceptibility to rheumatoid arthritis: a case-control study

Many extracellular matrix (ECM) proteases seem to be important in rheumatoid arthritis (RA) and regulation of their transcription levels is a critical mechanism for controlling their activity. We have investigated, therefore, whether the best-characterized single nucleotide polymorphisms (SNPs) affecting transcription of the ECM proteases that have been related with joint pathology are associated with RA susceptibility. Nine SNPs in eight genes were selected by bibliographic search, including SNPs in the genes encoding matrix metalloproteinase (MMP)1, MMP2, MMP3, MMP7, MMP9, MMP13, plasminogen activator, tissue type (PLAT) and PAI-1. They were studied in a case-control setting that included 550 RA patients and 652 controls of Spanish ancestry from a single center. Genotyping was performed by single-base extension. Only two of the nine SNPs showed significant association with RA susceptibility. RA patients showed increased frequencies of the -7351 T allele of the gene encoding PLAT (36.4% versus 32.1% in controls, p = 0.026) and the -1306 T allele of the gene encoding MMP2 (24.5% versus 20.3% in controls, p = 0.013). These two alleles seemed to cooperate according to an additive model with respect to increased RA susceptibility (p = 0.004), and they were the low-expression alleles of the respective SNPs in a PLAT enhancer and the MMP2 promoter. These findings are in agreement with previous data suggesting that these two ECM proteases have a protective role in RA pathology. Confirmation of these associations will be needed to support these hypotheses. The remaining SNPs did not show association, either individually or collectively. Therefore, although regulatory SNPs in ECM proteases did not show any major effect on RA susceptibility, it was possible to find modest associations that, if replicated, will have interesting implications in the understanding of RA pathology.

Extensive multiallelic analysis of the relationship between HLA-DRB1 and rheumatoid arthritis using a Bayesian partition model

To analyse the association between individual HLA-DRB1 locus genotypes and rheumatoid arthritis (RA) susceptibility, taking in account the multiallelic nature of the shared epitope (SE). In total, 538 patients and 536 controls were genotyped for 12 alleles of the HLA-DRB1 locus. A Bayesian partition model and multivariate logistic models were used to assess the role of the SE and of its individual components. The SE was associated with RA susceptibility (odds ratio (OR) 2 versus 0 SE copy=9.99 (95 CI 4.69-15.30) and OR 1 versus 0 SE copy=3.16 (95% CI 2.42-4.12)). The Bayesian partition model supplied a permutation of the HLA-DRBA locus alleles ordered by increasing disease risk. Alleles associated with highest risks are those that code for the SE. The individual OR estimations for the HLA-DRB1 locus genotypes went from OR=1.00 (95% CI 1.00-1.25) for the less associated genotype to OR=21.40 (95% CI 8.02-65.79) for the most associated one. In conclusion, the allele order risk and the OR estimations for individual genotypes of the HLA-DRB1 locus were consistent with the SE theory. Using an exploratory statistical method without a priori hypothesis, our study allowed a detailed analysis of the multiallelic nature of the SE.

Interleukin-18 promoter polymorphism in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease in which interleukin (IL)-18 plays an important role. However, there are controversial reports on IL-18 promoter polymorphism as an independent marker of RA susceptibility. The aim of present study was to examine the IL-18 promoter polymorphism in patients with RA, and its association with disease susceptibility, activity and severity. We examined 309 patients with RA from a Polish population diagnosed according to the criteria of American College of Rheumatology. An allele-specific polymerase chain reaction was used for analysis of the polymorphisms in positions - 137 and - 607 in promoter region of IL-18 gene. A significantly decreased number of subjects with AC/AC and AG/AG diplotypes was observed among RA patients as compared with healthy controls (OR - 0.51, 95%CI 0.28-0.95, P = 0.045) and (OR - 0.12, 95% CI 0.02-0.97, P = 0.042), respectively. Nevertheless, there was no significant association with disease activity, joint erosions, extra-articular manifestations, rheumatoid factor. Above results suggest that IL-18-137 and - 607 promoter polymorphisms are not the significant factors influencing RA course and severity in a Polish population.

Work-related empowerment of the multidisciplinary team at the Rheumatism Foundation Hospital

Carried out as part of a staff development project, this study describes the experiences of work-related empowerment within a multidisciplinary team at the Rheumatism Foundation Hospital in Finland. The data were collected using a structured questionnaire consisting of background variables and questions concerning verbal, behavioural and outcome empowerment. The questionnaire was sent to all members of the multidisciplinary team at the Rheumatism Foundation Hospital, with the exception of physicians, departmental secretaries and administrative personnel. The response rate was 58%. The data were examined using statistical methods. The multidisciplinary team felt quite strong verbal and behavioural empowerment, but was less confident in terms of outcome empowerment. Several factors were found to be associated with the different fields of empowerment. In conclusion, the multidisciplinary team felt quite strong work-related empowerment.

Detailed analysis of the variability of peptidylarginine deiminase type 4 in German patients with rheumatoid arthritis: a case-control study

Peptidylarginine deiminase type 4 (PADI4) genotypes were shown to influence susceptibility to rheumatoid arthritis (RA) in the Japanese population. Such an association could not previously be confirmed in different European populations. In the present study, we analysed exons 2-4 of PADI4 in 102 German RA patients and 102 healthy individuals to study the influence of PADI4 variability on RA susceptibility by means of haplotype-specific DNA sequencing. Analyses of the influence of PADI4 and HLA-DRB1 genotypes on disease activity and on levels of anti-cyclic citrullinated peptide antibodies were performed. Comparing the frequencies of PADI4 haplotype 4 (padi4_89*G, padi4_90*T, padi4_92*G, padi4_94*T, padi4_104*C, padi4_95*G, padi4_96*T) (patients, 14.7%; controls, 7.8%; odds ratio = 2.0, 95% confidence interval = 1.1-3.8) and carriers of this haplotype (patients, 27.5%; controls, 13.7%; odds ratio = 2.4, 95% confidence interval = 1.2-4.8), a significant positive association of PADI4 haplotype 4 with RA could be demonstrated. Other PADI4 haplotypes did not differ significantly between patients and controls. Regarding the individual PADI4 variants, padi4_89 (A-->G), padi4_90 (C-->T), and padi4_94 (C-->T) were significantly associated with RA (patients, 49.5%; controls, 38.7%; odds ratio = 1.6, 95% confidence interval = 1.1-2.3). Considering novel PADI4 variants located in or near to exons 2, 3, and 4, no quantitative or qualitative differences between RA patients (8.8%) and healthy controls (10.8%) could be demonstrated. While the PADI4 genotype did not influence disease activity and the anti-cyclic citrullinated peptide antibody level, the presence of the HLA-DRB1 shared epitope was significantly associated with higher anti-cyclic citrullinated peptide antibody levels (P = 0.033). The results of this small case-control study support the hypothesis that variability of the PADI4 gene may influence susceptibility to RA in the German population. Quantitative or qualitative differences in previously undefined PADI4 variants between patients and controls could not be demonstrated.

Prognostic significance of CD40 expression in malignant lymphoma developing in rheumatoid arthritis

PURPOSE

CD40, a member of tumor necrosis factor receptor superfamily, is expressed in synovial fluid B cells in rheumatoid arthritis (RA) and is postulated to contribute to RA progression. In this study, prognostic significance of CD40 expression was analyzed in B cell lymphoproliferative disorders (LPD) developing in RA.

METHOD

CD40 expression was immunohistochemically examined in 35 cases of B-cell LPD developing in RA and in 32 of sporadic B-cell LPD as control. CD40 expression at mRNA level evaluated by quantitative reverse transcription-PCR and at protein level evaluated by immunohistochemistry correlated.

RESULTS

Frequency of diffuse large B-cell lymphoma (DLBCL) in RA- and sporadic-LPD was 71.4 and 59.3%, respectively. CD40 positive rate in RA-LPD (62.9%) was significantly higher than that in sporadic LPD (37.5%) (P = 0.015). Interval between onset of RA and LPD development was shorter in CD40 positive cases than in negative cases (median 120 and 204 months, respectively) (P < 0.07). Five-year survival rate in CD40 positive DLBCL cases (75%) was significantly better than that in negative cases (25%) (P < 0.05).

CONCLUSION

RA-LPD is characterized by the higher frequency of CD40 expression compared to sporadic LPD and CD40 positive cases which showed more favorable prognosis than those without CD40 expression.

Interleukin-18-promoter polymorphisms are not relevant in rheumatoid arthritis

Interleukin-18 (IL-18), a member of the IL-1 family, is known to play a relevant role in rheumatoid arthritis (RA) physiopathology mainly by promoting the inflammatory response. The aim of this work was to investigate the possible implication of two single-nucleotide polymorphisms (SNPs) [-607 A/C (rs1946518) and -137 G/C (rs187238)] within the IL-18-promoter region in RA predisposition and clinical course. A total of 362 unrelated RA patients and 339 healthy controls were genotyped using a real-time polymerase chain reaction (PCR) method for the -607 A/C SNP and a sequence-specific PCR method (PCR-SSP) for the -137 G/C polymorphism. No statistically significant differences were observed for both -607 and -137 IL-18-promoter polymorphisms between RA patients and controls, considering either allelic or genotypic frequencies. In addition, no association was found with the haplotypes inferred by the two polymorphisms and RA susceptibility. This was also the case when RA patients were stratified according to sex, age at the onset of the disease, rheumatoid factor status, and extraarticular manifestations. Our data suggest that -607 A/C (rs1946518) and -137 G/C (rs187238) polymorphisms within the IL-18-promoter region do not play a major role in RA predisposition.

Genetic and genomic studies of PADI4 in rheumatoid arthritis

OBJECTIVES

Strong genetic association of rheumatoid arthritis (RA) with PADI4 (peptidyl arginine deiminase) has previously been described in Japanese, although this was not confirmed in a subsequent study in the UK. We therefore undertook a further study of genetic association between PADI4 and RA in UK Caucasians and also studied expression of PADI4 in the peripheral blood of patients with RA.

METHODS

Seven single-nucleotide polymorphisms (SNP) were genotyped using polymerase chain reaction (PCR)-restriction fragment length polymorphism in 111 RA cases and controls. A marker significantly associated with RA (PADI4_100, rs#2240339) in this first data set (P = 0.03) was then tested for association in a larger group of 439 RA patients and 428 controls. PADI4 transcription was also assessed by real-time quantitative PCR using RNA extracted from peripheral blood mononuclear cells from 13 RA patients and 11 healthy controls.

RESULTS

A single SNP was weakly associated with RA (P = 0.03) in the initial case-control study, a single SNP (PADI4_100) and a two marker haplotype of that SNP and the neighbouring SNP (PADI4_104) were significantly associated with RA (P = 0.02 and P = 0.03 respectively). PADI4_100 was not associated with RA in a second sample set. PADI4 expression was four times greater in cases than controls (P = 0.004), but expression levels did not correlate with the levels of markers of inflammation.

CONCLUSION

PADI4 is significantly overexpressed in the blood of RA patients but genetic variation within PADI4 is not a major risk factor for RA in Caucasians.

Exploring the genetic basis of disease using RNA interference

Cancer and autoimmunity are polygenic diseases. In order to better understand the mechanisms of disease development and progression it is essential to uncover which genes are involved. Much has been learned from population studies in human patients by searching for polymorphic genetic loci associated with disease. In addition, animal models of tumor development, as well as models for various autoimmune conditions such as multiple sclerosis and Type I diabetes, have helped determine genetic loci that contribute to disease susceptibility. However, characterization of the exact genes involved is often difficult and requires lengthy and technically demanding genetic manipulations. The generation of knockout animals is the method of choice to probe single genes. However, this is not possible in all species or even in all inbred strains within a species. The recent discovery of a new post-transcriptional gene silencing pathway termed RNA interference, which is mediated by short fragments of double-stranded RNA (short-interfering RNA), has opened up new avenues for genetic manipulation of experimental animals. This review will consider how silencing genes by RNA interference within the context of experimental disease models promises to become a powerful new tool for the genetic analysis of cancer and autoimmunity. Advances in RNA interference technology now permit the relatively rapid generation of transgenic animals in a wide range of species with complex genetic backgrounds that were previously inaccessible to genetic manipulation. This novel approach should help refine the characterization of disease-associated genes, either by silencing specific candidates or even by screening a larger number of genes in vivo within a comparatively short time frame.

HLA-DRB1 alleles and HLA-DRB1 shared epitopes are markers for juvenile rheumatoid arthritis subgroups in Colombian mestizos

We studied the association of human leukocyte antigen (HLA)-DRB1 and HLA-DQB1 alleles and HLA haplotypes with juvenile rheumatoid arthritis (JRA) in 65 patients and 65 controls from Colombia. The JRA subsets were distinguished on the basis of criteria established by the American College of Rheumatology. Two alleles were associated with protection, HLA-DRB1*1501 (p = 0.002) and HLA-DRB1*1402 (p = 0.01). HLA-DRB1*1602 (p = 0.0000002) was associated with susceptibility for systemic JRA and HLA-DRB1*1104 (p = 0.0002) for pauciarticular JRA. Amino acid sequences at residues 70-74 of DRB1 chain shared by HLA-DRB1 alleles (shared epitomes) were also informative. The polyarticular JRA subset revealed association with (70)QRRAA(74), which includes HLA-DRB1*04, 01, and (70)DRRAA(74), which includes DRB1*1601, 1602, 1101, and 1104. Two new findings of interest were the association of the haplotypes DRB1*1104, DQB1*0301(p = 0.0002) with pauciarticular JRA and DRB1*1602, DQB1*0301 (p = 0.0000002) association with systemic JRA. The DRB1 alleles of these two haplotypes share the epitope (70)DRRAA(74)and were associated with both the pauciarticular and the systemic subset of JRA. Our results suggest that studies of disease susceptibility in populations of admixed genetic background should take into account the contribution of different ethnic groups or nationalities in the recruitment of controls and patients studied in order to rule out genetic stratification.

Identification of a novel DRB1*04 allele: DRB1*0445

The novel allele DRB1*0445 differs from DRB1*04051 by a single nucleotide substitution at codon 23 (CGG-->CCG), resulting in an amino-acid change from arginine to proline. The haplotype associated with the novel allele is A*2402-B*5401-Cw*0102-DRB1*0445-DRB4*01-DQB1*0302.