HLA antigens in Tlingit Indians with rheumatoid arthritis

The Impact of Rheumatoid Arthritis on First Nations and How We Can Work With Communities to Prevent It

Rheumatoid arthritis (RA) is prevalent in many Indigenous North American First Nations (FN) and tends to be seropositive, familial, and disabling, as well as associated with highly unfavorable outcomes such as early mortality. The risk of developing RA is based on a perfect storm of gene-environment interactions underpinning this risk. The gene-environment interactions include a high frequency of shared epitope encoding HLA alleles, particularly HLA-DRB1*1402, in the background population, and prevalent predisposing environmental factors such as smoking and periodontal disease. Together, these provide a compelling rationale for an RA prevention agenda in FN communities. Our research team has worked in partnership with several FN communities to prospectively follow the first-degree relatives of FN patients with RA, with the aim of better understanding the preclinical stages of RA in this population. We have focused on specific features of the anticitrullinated protein antibodies (ACPA) and other proteomic biomarkers as predictors of future development of RA. These studies have now led us to consider interventions having a favorable risk-benefit ratio if applied at a stage prior to a hypothetical "point of no return," when the autoimmunity potentially becomes irreversible. Based on a supportive mouse model and available human studies of curcumin, omega-3, and vitamin D supplements, we are undertaking studies where we screen communities using dried blood spot technology adapted for the detection of ACPA, and then enrolling ACPA-positive individuals in studies that use a combination of these supplements. These studies are guided by shared decision-making principles.

Indonesians Human Leukocyte Antigen (HLA) Distributions and Correlations with Global Diseases

In Human, Major Histocompatibility Complex known as Human Leukocyte Antigen (HLA). The HLA grouped into three subclasses regions: the class I region, the class II region, and the class III region. There are thousands of polymorphic HLAs, many of them are proven to have correlations with diseases. Indonesia consists of diverse ethnicity people and populations. It carries a unique genetic diversity between one and another geographical positions. This paper aims to extract Indonesians HLA allele data, mapping the data, and correlating them with global diseases. From the study, it is found that global diseases, like Crohn's disease, rheumatoid arthritis, Graves' disease, gelatin allergy, T1D, HIV, systemic lupus erythematosus, juvenile chronic arthritis, and Mycobacterial disease (tuberculosis and leprosy) suspected associated with the Indonesian HLA profiles.

A Prospective Study of the Development of Inflammatory Arthritis in the Family Members of Indigenous North American People With Rheumatoid Arthritis

OBJECTIVE

To determine the incidence of inflammatory arthritis and autoantibody prevalence in Indigenous North American people.

METHODS

Unaffected relatives of Indigenous North Americans with rheumatoid arthritis (RA) from central Canada and Alaska were systematically monitored from 2005 to 2017. Rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPAs) were tested at every visit, and a subset was tested for ACPA fine specificity using a custom multiplex assay. Multistate models based on all available study visits were developed to determine the likelihood of transitioning between autoantibody states, or to inflammatory arthritis.

RESULTS

Eighteen of 374 relatives (4.8%) developed inflammatory arthritis during follow-up (after a mean ± SD of 4.7 ± 2.4 years), yielding a transition rate of 9.2 cases/1,000 person-years. Thirty percent of those who developed inflammatory arthritis were seronegative at baseline, but all were seropositive at inflammatory arthritis onset. Although 30% of ACPA/RF double-seropositive individuals developed inflammatory arthritis (after 3.2 ± 2.2 years), the majority of these individuals did not develop inflammatory arthritis. Multistate modeling indicated a 71% and 68% likelihood of ACPA and RF seropositive states, respectively, reverting to a seronegative state after 5 years, and a 39% likelihood of an ACPA/RF double-seropositive state becoming seronegative. Fine specificity testing demonstrated an expansion of the ACPA repertoire prior to the development of inflammatory arthritis.

CONCLUSION

Despite a high incidence of inflammatory arthritis in this cohort of at-risk relatives of Indigenous North Americans with RA, a large proportion of autoantibody-positive individuals do not develop inflammatory arthritis and revert back to an autoantibody-negative state.

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.

Molecular basis for increased susceptibility of Indigenous North Americans to seropositive rheumatoid arthritis

OBJECTIVE

The pathogenetic mechanisms by which HLA-DRB1 alleles are associated with anticitrullinated peptide antibody (ACPA)-positive rheumatoid arthritis (RA) are incompletely understood. RA high-risk HLA-DRB1 alleles are known to share a common motif, the 'shared susceptibility epitope (SE)'. Here, the electropositive P4 pocket of HLA-DRB1 accommodates self-peptide residues containing citrulline but not arginine. HLA-DRB1 His/Phe13β stratifies with ACPA-positive RA, while His13βSer polymorphisms stratify with ACPA-negative RA and RA protection. Indigenous North American (INA) populations have high risk of early-onset ACPA-positive RA, whereby HLA-DRB1*04:04 and HLA-DRB1*14:02 are implicated as risk factors for RA in INA. However, HLA-DRB1*14:02 has a His13βSer polymorphism. Therefore, we aimed to verify this association and determine its molecular mechanism.

METHODS

HLA genotype was compared in 344 INA patients with RA and 352 controls. Structures of HLA-DRB1*1402-class II loaded with vimentin-64Arg59-71, vimentin-64Cit59-71 and fibrinogen β-74Cit69-81 were solved using X-ray crystallography. Vimentin-64Cit59-71-specific and vimentin59-71-specific CD4+ T cells were characterised by flow cytometry using peptide-histocompatibility leukocyte antigen (pHLA) tetramers. After sorting of antigen-specific T cells, TCRα and β-chains were analysed using multiplex, nested PCR and sequencing.

RESULTS

ACPA+ RA in INA was independently associated with HLA-DRB1*14:02. Consequent to the His13βSer polymorphism and altered P4 pocket of HLA-DRB1*14:02, both citrulline and arginine were accommodated in opposite orientations. Oligoclonal autoreactive CD4+ effector T cells reactive with both citrulline and arginine forms of vimentin59-71 were observed in patients with HLA-DRB1*14:02+ RA and at-risk ACPA- first-degree relatives. HLA-DRB1*14:02-vimentin59-71-specific and HLA-DRB1*14:02-vimentin-64Cit59-71-specific CD4+ memory T cells were phenotypically distinct populations.

CONCLUSION

HLA-DRB1*14:02 broadens the capacity for citrullinated and native self-peptide presentation and T cell expansion, increasing risk of ACPA+ RA.

Immunogenetic Risks of Anti-Cyclical Citrullinated Peptide Antibodies in a North American Native Population with Rheumatoid Arthritis and Their First-degree Relatives

Objective.

To determine the prevalence of anti-cyclic citrullinated peptide (anti-CCP) antibodies in unaffected relatives of North American Native probands with rheumatoid arthritis (RA); and the associations of the shared epitope (SE) and HLA-DRB1*0901 with RA and anti-CCP antibodies.

Methods.

The subjects were RA probands, affected relatives, unaffected first-degree (FDR) and more distant relatives, and unaffected controls from the same population. HLA-DRB1 typing was determined by DNA sequencing and anti-CCP antibodies were determined by ELISA.

Results.

DRB1*0901, SE, and SE/DRB1*0901 genotypes were all associated with RA. SE/DRB1*0901, but not other SE genotypes, was associated with disease onset at age < 16 years. The frequency of anti-CCP antibodies was 82% in RA probands, 17% in FDR, 11% in more distant relatives, and 3% in controls. Among unaffected relatives, a significant increased risk of anti-CCP was associated with SE/DRB1*0901 genotype, but not with SE.

Conclusion.

An independent association of the non-SE allele DRB1*0901 with RA was confirmed in this population, and this allele in combination with a SE allele was associated with younger age at disease onset. FDR of RA probands have a higher prevalence of anti-CCP antibodies than more distant relatives and unrelated controls, suggesting a gradient of risk for disease development. Immunogenetic risks may act early in disease pathogenesis at the level of initiation of RA autoantibody formation; however, it is not clear what additional genetic and environmental risks are involved in progression to clinical disease.

Resequencing of the human major histocompatibility complex in patients with rheumatoid arthritis and healthy controls in Alaska Natives of Southeast Alaska

High prevalence and severity of rheumatoid arthritis (RA) with an early age of onset have previously been described in Alaska Native and American Indian (AN/AI) populations. The contribution of HLA-DRB1 alleles encoding a similar amino acid sequence, referred to as the shared epitope (SE), to RA risk is well recognized in multiple populations worldwide. DRB1*1402 allele is the major SE-encoding allele in AN/AI populations. However, DRB1*1402 is highly prevalent in healthy Alaska Natives of Southeast Alaska (AN), with no significant difference from RA patients, indicating this allele alone is not informative for defining genetic risk and non-human leukocyte antigen (non-HLA) genes are likely important in AN. We sought to deep resequence the human major histocompatibility complex (MHC) to characterize the single-nucleotide polymorphism (SNP) haplotypes within this region in RA cases and controls in AN. Approximately 99 kb of the MHC was resequenced with 95 amplicons throughout this region. Thirty-four cases and 74 controls were examined. A total of 696 SNPs were discovered from 85 of the selected 95 amplicons. Disease association signals were detected for nine of the 95 amplicons analyzed. Increased risk of RA was associated with five amplicons in the class I, class II or class III region and resistance to disease with four amplicons in the class I region. Our results indicate that non-HLA MHC genes and/or unknown exogenous factors likely modulate risk of RA in the AN population.

Identification of susceptibility and protective major histocompatibility complex haplotypes in canine diabetes mellitus

Diabetes mellitus occurs spontaneously in dogs, which is believed to have an autoimmune component and to be a model of human latent autoimmune diabetes of adults (LADA). Some dog breeds (e.g. Samoyed) are particularly predisposed, whereas others (e.g. Boxer) are highly resistant. With the completion of the Dog Genome Assembly, comparative genomic studies of complex diseases in dogs, including diabetes, could provide an important investigative approach into such disorders. Type 1 diabetes in humans is strongly associated with major histocompatibility complex (MHC) class II polymorphisms. We have investigated whether canine dog leucocyte antigen (DLA) class II haplotypes are associated with diabetes. DNA from 460 cases and 1047 controls were genotyped for DLA-DRB1, DLA-DQA1 and DLA-DQB1 using sequence-based typing. Three DLA haplotypes, DRB1*009/DQA1*001/DQB1*008, DRB1*015/DQA1*0061/DQB1*023 and DRB1*002/DQA1*009/DQB1*001, were found at significantly increased frequency in cases with diabetes compared with controls. One DLA-DQ haplotype, DQA1*004/DQB1*013, was significantly reduced in cases with diabetes. Further analysis showed that DQA1 alleles carrying arginine at codon 55 of DQA1 were increased in dogs with diabetes. To our knowledge, this is the first report of a comparative study of MHC and diabetes in a non-rodent species. Since no laboratory model of LADA exists and dogs and humans share similar environments, further research into canine diabetes is warranted.

Rheumatoid arthritis in American Indians and Alaska Natives: a review of the literature

BACKGROUND AND OBJECTIVES

An increased prevalence of rheumatoid arthritis (RA) has been reported in several American Indian and Alaska Native (AI/AN) populations. This article reviews the prevalence of RA in these populations, including clinical and serologic features.

METHODS

References were taken from Medline through November 2003, in addition to the Arctic Health Literature Database and the American Indian and Alaska Native Health Bibliography.

RESULTS

Published articles reveal an increased prevalence of RA in the Tlingit, Yakima, Pima, and Chippewa Indians. Clinically the disease in these groups is often severe, with early age of onset, high frequency of radiographic erosions, rheumatoid nodules, and positive rheumatoid factor. Studies of HLA alleles in cases and controls have found a high frequency of HLA DRB1*1402.

CONCLUSIONS

The increased prevalence of RA and more severe disease in specific AI/AN populations suggest an important genetic influence on the development of RA in AI/AN populations. A high frequency of specific high-risk HLA alleles in these populations may account for some of the increased risk, but other genetic factors are likely to contribute. Environmental factors have not been studied in detail, but may also play an important role.

RELEVANCE

Understanding the patterns and burden of disease in AI/AN populations may contribute to understanding the etiology of RA and to the development of preventive strategies.

Rheumatic disease in native american children: Opportunities and challenge

Rheumatic diseases are prevalent in Native American adults at rates five to seven times higher than those seen in the Caucasian population. Little, however, has been published concerning rheumatic diseases in Native American children. The authors' work in Oklahoma and with tribes on the northern Great Plains demonstrates high rates of childhood-onset rheumatic disease in this population. Familial disease is common, and large, multiplex kindreds showing strong founder effects are likely found within specific Native American tribes. However, a deeper understanding of the genetic and environmental triggers of rheumatic disease in Native Americans will require a respect and appreciation for the specific and unique cultural and social issues that impinge on research with Native Americans and other indigenous people.

Geographic patterns of functional categories of HLA-DRB1 alleles: a new approach to analyse associations between HLA-DRB1 and disease

Because specific amino acids found within the peptide-binding cleft of human leukocyte antigen (HLA) molecules have been implicated in HLA/disease associations, an approach which consists in grouping the alleles according to their functional properties at the protein level may enable us to better understand HLA associations than the conventional allelic classification. In this study, we applied this methodology to investigate the associations between HLA-DRB1 and rheumatoid arthritis. The alleles were first classified into seven functional categories [restrictive supertype patterns (RSPs)], among which three were known to be significantly associated with susceptibility (one category) or resistance (two categories) to rheumatoid arthritis. The frequencies of these categories were then estimated in 104 population samples previously tested for HLA-DRB1, and their variability was analysed spatially on a worldwide scale by applying an original methodology for detecting discontinuities in geographically patterned data. RSP frequencies were also compared to known values of rheumatoid arthritis prevalence in some populations. The results indicated that the three RSP frequency distributions were geographically structured, and that these patterns could generally be explained by the history of human migrations. However, the peculiar pattern observed for RSP 'A' (conferring susceptibility to rheumatoid arthritis) indicated a possible association with some latitude-dependent disease. Furthermore, the very high correlation coefficient found between RSP 'A' frequencies and rheumatoid arthritis prevalence confirmed the significant disease association of this functional category. In contrast, the putative protective effect of the other RSPs ('De' and 'Q') was not detectable at the worldwide level, but may be significant in specific geographic areas. This study shows that population genetic diversity analyses based on a functional grouping of HLA alleles provide an efficient way to explore the mutual influence of HLA genetic variation and disease.

Prognostic use of human leukocyte antigen genotyping for rheumatoid arthritis susceptibility, disease course, and clinical stratification

HLA markers of the class II region are important for determination of the predisposition to RA, clinical manifestations, and rate of progression of joint destruction in this autoimmune disease. Furthermore, evidence emerges indicating that HLA markers also have an impact on treatment outcome in RA. Currently, several immunopathogenetic models of HLA-dependent influences in RA are under debate. These models insufficiently explain the graded influence of HLA-DR and HLA-DQ on manifestation and joint destruction, however. Currently, there is not enough evidence to unequivocally identify a primary susceptibility locus or to pinpoint the HLA-dependent mechanism in RA. Overall, the influence of HLA class II markers on disease susceptibility is rather restricted, and, in turn, their utility in establishing the diagnosis of RA is of limited use. Although relative risks are higher for the association of particular genotypes with extra-articular forms of RA, HLA genotyping may not contribute to prognostication in individual patients but may aid in disease stratification. In contrast, HLA genotyping in early RA, particularly when combined with the determination of RFs and determination of the presence of bony erosions, is of value to identify patients at risk for poor outcome. In turn, these patients may benefit from early aggressive therapy, and HLA genotyping should be useful to aid in risk stratification in patients and thus helpful for the choice of treatment. Lastly, disease and risk stratification based on HLA markers along with the elucidation of HLA-dependent mechanisms may facilitate the development of specific immunotherapy modalities.

Tumour necrosis factor microsatellites and HLA-DRB1*, HLA-DQA1*, and HLA-DQB1* alleles in Peruvian patients with rheumatoid arthritis

OBJECTIVE

To study the association between rheumatoid arthritis (RA) and HLA and tumour necrosis factor (TNF) polymorphism in Peruvian mestizo patients in comparison with ethnically similar controls.

METHODS

Seventy nine patients with RA and 65 ethnically matched healthy controls were genotyped for HLA-DRB1, HLA-DQA1, HLA-DQB1, and TNFalpha and TNFbeta alleles using PCR amplification. Clinical severity was assessed as mild, moderate, or severe in 35 of the patients.

RESULTS

TNFalpha6 showed the strongest association with disease susceptibility. The TNFalpha6 allele was more common in patients than in controls (p<0.0076) and the proportion of patients with at least one copy of this allele was greater (p<0.015, relative risk 2.35). Among the HLA-DRB1* alleles with the shared epitope sequence, only the DRB1*1402 allele was significantly increased in patients compared with controls (p<0.0311), as was the proportion of patients with at least one copy of this allele (p<0.0232, relative risk 2.74). In contrast, the overall frequency of alleles with the shared epitope was not different in patients and controls. The haplotype HLA-DRB1*1402-DQB1*0301-DQA1*0401 was significantly more common in patients. TNFalpha6 was more common in patients whether or not they had this haplotype. None of the 11 patients lacking the TNFalpha6 allele had severe disease.

CONCLUSIONS

This study shows for the first time that TNF gene polymorphism is associated with susceptibility to RA in a non-white population. TNFalpha6 and HLA-DRB1*1402 independently conferred significantly increased risk in Peruvian mestizo patients.

Protection against severe disease is conferred by DERAA-bearing HLA-DRB1 alleles among HLA-DQ3 and HLA-DQ5 positive rheumatoid arthritis patients

Experimental studies in transgenic mice have suggested that HLA-DQ predisposes to rheumatoid arthritis (RA), but could also modulate disease severity by presenting peptides derived from self-DR molecules. In particular, a short amino acid sequence, (70)DERAA(74), in the third hypervariable region of HLA-DRB1 confers protection for the disease, while particular HLA-DQ [DQB1*0501/DQA1*01 (DQ5) and DQB1*03/DQA1*03 (DQ3)] molecules predispose to the disease. We have therefore analyzed the allelic distribution of HLA-DRB1, DQA1, and DQB1 and the presence of rheumatoid factor and nodules among 199 German RA patients and 196 healthy controls. Our results show that HLA-DQB1*03/DQA1*03 (or DRB1*04) predisposes to RA more than HLA-DQB1*0501/DQA1*01 (i.e., DRB1*01 and DRB1*10). Homozygosity for DQ3 confers the strongest genetic risk for RA (OR = 19.79 compared to OR = 10.05 for two doses of shared epitope (SE) positive HLA-DRB1 alleles). Furthermore, patients carrying both predisposing DQ and (70)DERAA(74)-positive HLA-DRB1 alleles are more often rheumatoid factor (RF) negative than patients carrying predisposing DQ alleles alone. Only one out of 14 patients (7%) with a protective combination (DQ3/(70)DERAA(74) and DQ5/(70)DERAA(74)) had rheumatoid nodules compared to 67 out of 144 patients (46.5%) with predisposing DQ alleles alone (OR = 0.12, 95% CI: 0.02-0.72, p = 0.004). These results demonstrate a protective role of (70)DERAA(74)-positive DRB1 alleles against disease severity among RA 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.

Risk for rheumatic disease in relation to ethnicity and admixture

Risk of systemic lupus erythematosus (SLE) is high in west Africans compared with Europeans, and risk of rheumatoid arthritis (RA) is high in Native Americans compared with Europeans. These differences are not accounted for by differences in allele or haplotype frequencies in the human leucocyte antigen (HLA) region or any other loci known to influence risk of rheumatic disease. Where there has been admixture between two or more ethnic groups that differ in risk of disease, studies of the relationship of disease risk to proportionate admixture can help to distinguish between genetic and environmental explanations for ethnic differences in disease risk and to map the genes underlying these differences.

[Clinical characteristics of familial rheumatoid arthritis in Spain. A study of 73 families. Spanish Consortium for Rheumatoid Arthritis (CEAR) and European Consortium for Familial Rheumatoid Arthritis (ECRAF)]

OBJECTIVE

To describe clinical characteristics and the homogeneity of disease expression between involved members in multicase Spanish rheumatoid arthritis (RA) families.

PATIENTS AND METHODS

73 families with two or more siblings with RA were found, with a total of 149 patients distributed in 79 pairs (70 sib pairs, and 3 sib trios). Demographic, clinical and radiological characteristics were recorded in a standard questionnaire.

RESULTS

Clinical characteristics were similar to those of sporadic RA with a high frequency of women (78%), positive rheumatoid factor (RF) (86%), erosions (89%) and a 25% of the patients having extraarticular disease. The most important variable in disease severity was disease duration. The concordance between family members of the same age and calendar year of disease onset, and the pattern of disease expression, was not higher than expected, showing that the disease is heterogenic.

CONCLUSION

Environmental factors seem to be more important in RA susceptibility. Clinical characteristics of familiar RA in Spain do not seem to be different from sporadic RA, although differences were found in disease expression within families that may be due to variation of genetic or environmental factors, responsible for the susceptibility and disease duration.

Rheumatic diseases in North America's indigenous peoples

OBJECTIVES

There are at least 3 million North American Indians and Eskimos in North America. The epidemiology of rheumatic diseases in Native North Americans differs from that described for the remainder of the North American population. An enhanced understanding of rheumatic diseases in these indigenous people may provide valuable clues to the cause of these disorders and improve rheumatologic care.

METHODS

The world literature was searched for all reports of rheumatic diseases in North American Indians and Eskimos. The reports were reviewed and the findings summarized by disease process.

RESULTS

Many Native American groups have high prevalence rates of rheumatoid arthritis (RA), systemic lupus erythematosus, connective tissue diseases, and spondyloarthropathies. There appears to be a correlation between the pattern of rheumatic diseases in Native North Americans and the patterns of migration and ancestry. In general, Amerind Indians have increased rates of RA and connective tissue disease, while Na-Dene Indians and Eskimos have high rates of spondyloarthropathies. The RA seen in Native Americans is generally severe, seropositive, with an early age of onset, and frequent extraarticular manifestations. Many Native American groups have very high frequencies of the RA shared epitope. The majority of Native American and Eskimo groups also have high frequencies of HLA-B27, and some of the world's highest prevalence rates of spondyloarthropathies are described in these groups. Although some groups show a marked tendency to develop either Reiter's syndrome or ankylosing spondylitis, psoriatic and enteropathic arthritis are rare.

CONCLUSIONS

The excess rheumatic disease seen in this population is most likely genetic in origin. Because of the combination of high rates of rheumatic disease and relative genetic homogeneity, Native North Americans represent a singular opportunity to study genetic contributions to rheumatic disease. For clinicians, the index of suspicion for rheumatic diseases in North American Indians and Eskimos should be high, and the severe disease and sometimes atypical presentations kept in mind.

Polymorphism of the HLA-DRB1 locus in Colombian, Ecuadorian, and Chilean Amerinds

We have characterized the DRB1 genotypes in a sample of 64 South American Indians drawn from populations in Chile, Colombia, and Ecuador. No novel DRB1 alleles were found in the total of 17 different alleles characterized, indicating that rapid allelic generation does not occur at the DRB1 loci, in contrast to HLA-B. Comparison between Chilean and Colombian/Ecuadorian samples revealed no major differences in their allelic frequencies. In the combined Amerind sample the HLA-DRB1*0407 and HLA-DRB1*1402 alleles occurred in the highest frequencies (38% and 22%, respectively). Genetic distance measurement showed the HLA-DRB1 frequencies reported here to agree with findings in other Amerind groups. The high frequencies of both HLA-DRB1*0407 and HLA-DRB1*1602 alleles, in conjunction with their absence in Siberian samples, suggest that migratory groups other than Siberians may have been involved in the peopling of the Americas.

HLA markers and prediction of clinical course and outcome in rheumatoid arthritis

OBJECTIVE

To evaluate HLA markers as early prognostic factors for disease severity in rheumatoid arthritis (RA).

METHODS

HLA genotyping was carried out in a retrospective analysis of 66 RA patients and in a prospective study of 55 RA patients and 87 healthy controls using polymerase chain reaction-based methods for HLA-DRB1 specificities, DR4 alleles, and their linked DQB1 alleles, as well as HLA-B27. The clinical course of RA was assessed by clinical and radiologic scores. The impact of HLA markers was evaluated by epidemiologic means in addition to modeling using multiple logistic regression analysis.

RESULTS

Shared epitope-positive (HVR3+) DR4 alleles and the HVR3 amino acid cassette QKRAA were associated with RA in both longstanding (relative risk [RR] 3.34 and 3.19) and recent-onset (RR 2.1 and 2.37) RA. In longstanding RA, radiologic evidence of severe joint destruction (Larsen score > 1.62) was seen more often in HVR3 shared epitope-positive patients than in epitope-negative patients (odds ratio [OR] = 25.67, chi 2 = 13.59, P = 0.0003). Moreover, rank sum analysis of Larsen indices indicated significantly higher ranking for the presence of the RA-associated HVR3 cassettes (QKRAA, QRRAA) when expressed on a DR4 allele (P < 0.0001). In the prospective study, DR4-positive patients had a significantly increased risk (OR = 13.75, P = 0.00083) of developing bony erosions. In addition, HVR3 epitope-positive DR4-positive individuals had significantly higher Larsen indices than did epitope-negative patients (P = 0.0083). In particular, the presence of the HVR3 epitope on DR4 resulted in an increased a posteriori likelihood (0.91) of developing early erosive disease compared with an a priori risk of 0.62. Conversely, the likelihood decreased to a minimum of 0.35 when the HVR3 epitope was absent.

CONCLUSION

While the contribution of HLA typing to establishing the diagnosis of RA is limited, HLA-DR genotyping and DR4 subtype determination provide valuable markers for the prognosis of joint destruction in RA.

Epidemiology of chronic arthritis in childhood

This study was performed to review reports of the descriptive epidemiology of chronic arthritis in childhood and to analyze the factors that may explain differences in its reported frequency. Articles were retrieved by searching MEDLINE and EMBASE under the following index terms: juvenile rheumatoid arthritis (JRA), juvenile chronic arthritis (JCA), spondyloarthropathy, epidemiology, prevalence, and incidence. For reports published between 1977 to 1982, the Index Medicus was used. All original articles that provided prevalence or incidence rates, population size, or number of cases, were reviewed and entered into the analysis. Variables analyzed were disease prevalence and incidence. Modifier variables investigated were diagnostic criteria, source population, geographic origin of the report (Europe or North America), duration of the study, and race of the population studied. Diagnostic criteria had no effect on reported prevalence or incidence rates. Prevalence per 100,000 at risk obtained from population studies (132, 95% CI: 119, 145) was significantly higher than values derived from practitioner- (26, 95% CI: 23, 29) or clinic-based studies (12, 95% CI: 10, 15) (P = .02). North American clinic-based studies had higher prevalence values compared with European reports (32, 95% CI: 26, 38 versus 8, 95% CI: 5, 11, P = .009). None of the factors analyzed accounted for the variability in reported incidence rates. An effect of race was detected only in the distribution of patients among onset subsets. Thus, the percentage of patients with pauciarticular JRA was highest in series of North American and European caucasian patients (58, 95% CI: 56, 60) compared with series of East Indian (25, 95% CI: 20, 31), native North American Indian (26, 95% CI: 15, 37), or other races (31, 95% CI: 28, 35) (P = .001). In contrast, the percentage of patients with polyarticular JRA was lowest in the former (27, 95% CI: 25, 28) compared with the other racial groups (East Indian, 61, 95% CI: 55, 66; native North American Indian, 64, 95% CI: 53, 76; other races, 34, 95% CI: 30, 38) (P = .004). Although an effect of source population on reported prevalence was confirmed, the effect of geographic origin suggests that environmental or ethnic differences also may influence the prevalence of chronic arthritis in children. Differences in the percentages of patients with pauciarticular and polyarticular JRA may reflect racial differences in the prevalence of these conditions.

Six new DR52-associated DRB1 alleles, three of DR8, two of DR11, and one of DR6, reflect a variety of mechanisms which generate polymorphism in the MHC

We have sequenced DNA from six new DR52-associated DRB1 alleles initially detected by PCR/SSOP analysis. Three DR8 associated alleles differed from previously known alleles by single nucleotide substitutions. DRB1*0807 and DRB1*0811 both vary from DRB1*08021 at codon 57 resulting in two different amino acids at this residue. DRB1*0807 was identified in samples of Brazilian origin while *0811 was identified among samples from the Tlingit Native American population of Southeast Alaska. DRB1*0814, identified in a family of Chinese origin, differed from DRB1*08032 at codon 12 at both the nucleotide and the amino acid level. In addition, two alleles of DR11, DRB1*1113 and *1119, were each detected in Caucasian individuals. DRB1*1113 differs from other DR11 alleles at codons 37, 67, 70 and 74, while DRB1*1119 differs from *1101 by a single nucleotide substitution at codon 67. Finally, DRB1*1418 was detected in a sample from an Asian or Pacific Islander and shares sequences with several other DR52-associated DRB1 alleles. These six DRB1 alleles appear to have been generated by either gene conversion events, DRB1*1113 and *1418, or by point mutations, DRB1*0814, *0807, *0811 and *1119, although the single nucleotide substitutions found in the latter three alleles are also present in at least one other DRB1 allele and, therefore, could have been the product of gene conversions.

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.

Extended HLA haplotypes among the Bari Amerindians of the Perija Range. Relationship to other tribes based on four-loci haplotype frequencies

Extended HLA haplotypes among Bari Amerindians living at the Perija Range on the limits between Colombia and Venezuela have been defined using serology for class I, electrophoresis and immuno-fixation for Bf and C4, and PCR-SSO for class II loci typing. Haplotypes were assigned based on family studies and gene frequencies were calculated using a subset of less related subjects selected from the genealogy. No rare class III variants were observed, but the characteristic low HLA diversity of isolated Amerindians populations present also in the Bari extends to Bf and C4. Thus there were only 22 different haplotypes segregating in families when nine loci were considered. All of them except three carried Bf*S, C4A*3, C4B*1. The null allele C4A*Q0 reached a frequency of 0.147 and was predominantly present in A24 Cw7 B39 DRB1*0411 haplotypes. In contrast to what has been reported using HLA alleles or class I haplotype frequencies and other isolated South American tribes, genetic distance estimates based on A-Cw-B-DR haplotype frequencies show a closer relationship between the two linguistically but geographically distant Venezuelan tribes, the Bari and the Warao, as compared to two culturally different Brazilian populations. The information reported here will be useful for identifying ancestral haplotypes in native peoples of America, for population comparison, and for discussing the differential influence of MHC haplotype diversity and population survival when similar data on other Amerindian tribes becomes available.

HLA class II and HLA-B27 oligotyping in two Siberian native population groups

It was the purpose of this study to better define the frequency of HLA-B27 subtypes and HLA class II alleles among indigenous populations from the eastern tip of the Chukotka Peninsula of Siberia, Russia, which have higher frequencies of HLA-B27 (40%) and spondyloarthropathies (2%) than Caucasian populations and test the hypothesis that these populations are more closely related to Orientals. Siberian Eskimos and Chukchi residing in four coastal villages on the Chukotka Peninsula inhabited by Siberian Eskimos and Chukchi people were examined using oligotyping of the polymerase-chain reaction-amplified second and third exons of the HLA-B27 gene. HLA-class II alleles (DRB1, DQA1 and DQB1) were similarly determined. Of 88 HLA-B27 positive individuals from these villages, all had HLA-B*2705, including the four patients with Reiter's syndrome and the five ankylosing spondylitis, except one Eskimo control who had HLA-B*2702. None had HLA-B*2704, a frequent subtype in Orientals. HLA-class II typing in 70 Siberian Eskimos and 71 Siberian coastal Chukchi revealed HLA-DRB1*0401, DRB1*0802, *0901 and *1402 to account for nearly all the DRB1 alleles found in this population, similar to what has been described in Eskimos in Alaska, but different from Chinese or native Americans in the U.S. The overwhelming majority of the individuals examined had HLA-DQB1*0301, similar to what has been observed in Native Americans. The Siberian Eskimos differed from the coastal Chukchi only in the occurrence of HLA-DRB1*0701, DQA1*0201, DQB1*0201 alleles, which occurred only in the former group. These data suggest that the Chukotka population is genetically more closely related to Caucasians and native Americans and less to other Oriental populations.

Meta-analysis reveals association between most common class II haplotype in full-heritage Native Americans and rheumatoid arthritis

The association of RA with the alleles at the HLA system was tested among Pima and Tohono O'odham Indians (Pimans) of the Gila River Indian Community of Arizona. Serologic class I (HLA-A, -B, and -C) alleles were typed in 51 individuals with RA and in 302 without RA. Serologic class II (HLA-DR, DQ; DR52 DR53) alleles were typed in a subset of 47 with RA and 147 without RA. Molecular subtypes of DR3X6, DRB1*1402, and *1406 were determined in 29 individuals, 16 with RA and 13 without RA. Among the cases with RA, 46 of 47 had the serologic antigen HLA-DR3X6, as did 140 of 147 of those without the disease. However, this association was not statistically significant because of the high prevalence of the antigen in the controls. Data from Pimans were analyzed with similar results from the Tlingit and Yakima Indians. A meta-analysis employing the Mantel-Haenszel procedure, stratified by tribe, revealed a statistically significant association between the most common haplotype, DRB1*1402 DQA1*0501 DQB1*0301 DRB3*0101, and RA (summary odds ratio = 2.63, 95% confidence interval = 1.08, 6.46). There was also a statistically significant difference in the genotype distributions of one class I locus, HLA-C, between those with and without RA (chi 2 = 12.4, 5 df; p = 0.03). It is concluded that the association with the most common class II haplotype in full-heritage Native Americans might help explain their high prevalence of RA.

Major histocompatibility complex class II alleles and haplotypes and blood groups of four Amerindian tribes of northern Colombia

MHC class II alleles and haplotypes were determined from unrelated individuals and families of the Arhuaco (n = 107), Kogi (n = 42), Arsario (n = 18), and Wayú (n = 88) tribes located in the northern part of Colombia. Class II DRB, DQA1, and DQB1 alleles were determined by PCR-SSO and PCR-RFLP based methods. Four haplotypes, [DRB1*0407, DRB4*0101, DQA1*03, DQB1*0302]; [DRB1*0403, DRB4*0101, DQA1*03, DQB1*0302]; [DRB1*1402/1406, DRB3*0101, DQA1*0501, DQB1*0301]; and [DRB1*0802, DQA1*0401, DQB1*0402], were observed among these four tribes. In addition to these haplotypes, the Wayú Indians showed a frequency of 21.3% for the [DRB1*1602, DRB5*02, DQA1*0501, DQB1*0301] haplotype, 13.1% for the [DRB1*0411, DRB4*0101, DQA1*03, DQB1*0302] haplotype, and 8.1% for the [DRB1*0411, DRB4*0101, DQA1*03, DQB1*0402] haplotype. Red cell antigen typing was used to calculate genetic admixture. The Kogi and Arsario showed no genetic admixture while the Arhuaco tribe showed admixture with genes of African origin and the Wayú showed admixture with Caucasians as well as genes of African origin. These findings were confirmed by the MHC class II allele and haplotype data obtained, as alleles and haplotypes of Caucasian and African origin were detected in the Wayú and Arhuaco and not in the Kogi or Arsario. These studies will be important in disease association and transplantation studies for Amerindian and colombian populations and for correlating genetic traits with the anthropologic and linguistic data available in order to better understand the Amerindian populations.

Decreasing incidence and prevalence of rheumatoid arthritis in Pima Indians over a twenty-five-year period

OBJECTIVE

To evaluate temporal trends in the incidence of rheumatoid arthritis (RA).

METHODS

Incident cases of RA were identified among a population-based cohort of Pima Indians in Arizona over the period 1965-1990.

RESULTS

Among 2,894 subjects, 78 incident cases of RA were identified. The age-adjusted incidence declined by 55% in men (Ptrend = 0.225), and by 57% in women (Ptrend = 0.017) after controlling for oral contraceptive or estrogen use and for pregnancy experience. During the same period, age-adjusted prevalence rates of active RA decreased by 29% in men (Ptrend = 0.63) and by 40% in women (Ptrend = 0.02). Fewer than 17% of subjects with known RA were taking slow-acting antirheumatic drugs (SAARDs) in 1990.

CONCLUSION

The decrease in incidence and prevalence of RA in this population over such a short period implicates the involvement of an environmental factor(s), other than exogenous estrogens, in the pathogenesis of the disease. However, the possibility that the observed decrease might be explained by an increased use of SAARDs in subjects with RA cannot be excluded.

Amino acids in the peptide-binding groove influence an antibody-defined, disease-associated HLA-DR epitope

A shared amino-acid sequence on the alpha helix of certain DR beta 1 chains is predicted to generate a 'shared epitope' that is implicated in susceptibility to the development of rheumatoid arthritis (RA). Different relative risks (RR) for disease susceptibility and severity conferred by these DR beta 1 chains suggest that their 'shared epitopes' are not equivalent. A set of monoclonal antibodies (MoAb) that map to the critical region, and for which optimal binding depends on DR context and cell lineage, was used to test this idea. Mapping experiments using mutated DR beta 1* molecules showed that the antibody-binding epitopes are overlapping; residue 70Q is pivotal for each, but neighbouring residues on the alpha helix and on the floor of the groove are also involved. Importantly, these epitopes are profoundly modified by peptide loading of DR beta 1*0401 molecules. These data suggest that 'shared epitopes' on DR molecules that are associated with RA are influenced by their context; such structural modifications may be the basis for the varying susceptibilities conferred by these DR molecules for the development of RA.

Analysis of monoclonal antibodies specific for unique and shared determinants on HLA-DR4 molecules

The specificities for seven mAbs to HLA-DR4 were determined initially using homozygous BCLs and L-cell transfectants expressing wild-type DR molecules. Three antibodies (NFLD.D1, NFLD.M1, and NFLD.D7) bound all DR4 molecules, but only one was specific for DR4. Four antibodies (NFLD.D2, NFLD.D3, NFLD.D8, and NFLD.D10) reacted with some but not all DR4 subtypes and had extra reactions, particularly with DR gene products associated with susceptibility to RA. To localize the antibody-binding epitopes on DR4 molecules, the antibodies were then analyzed on transfectants expressing hybrid genes, which were generated by exon shuffling of DRB1*0403 and DRB1*0701. Two of the pan-DR4 antibodies bound epitopes that require the beta 2 domain while the third mapped primarily to the HVR-I region. One antibody NFLD.D10 to subtypes of DR4 mapped to residues 40-97 on DR beta 1*0403 chains. Comparison of reaction patterns with amino acid sequences suggest that the antibodies against subtypes of DR4 are specific primarily for a region containing sequences postulated to determine susceptibility to RA.

T-cell receptor polymorphisms in Tlingit Indians with rheumatoid arthritis

Rheumatoid arthritis (RA) develops as a result of the interaction of both genetic and environmental factors. Among the genes in humans that have been suggested as candidate susceptibility genes in RA are those encoding the T cell receptor for antigen (TCR). A high prevalence and early age of onset of RA has previously been reported in Alaskan Tlingit Indians. In this study, the frequency of seven different restriction fragment length polymorphisms (RFLPs) in the TCR alpha and beta gene complexes were measured in a population of Alaskan Tlingit Indians. No statistically significant differences were noted when the frequencies of these RFLPs were compared between Tlingits with RA and healthy controls (p > 0.05). These results do not support the hypothesis of an RA-susceptibility allele in the vicinity of these TCR alpha or beta genes. Since TCR RFLPs have not been extensively studied in native American populations, TCR polymorphism frequencies in the Tlingits were also compared to the frequencies observed in a second control group of healthy Caucasians. Statistically significant differences were observed in these comparisons implying a different distribution of individuals in these populations with different TCR repertoires.

Differences in HLA class II alleles of isolated South American Indian populations from Brazil and Argentina

We have studied the HLA class II alleles in 277 South American Indians, which included Argentinian tribes from the Gran Chaco: Toba (n = 135), Toba-Pilaga (n = 19), Mataco-Wichi (n = 49), and Xavantes, a tribe from Central Brazil (n = 74). In the Brazilian tribe, only four DR groups were found: DRB1*1602 (gf = 0.303), DRB1*04 including DRB1*0404 (gf = 0.070) and DRB1*0407 (gf = 0.077), DRB1*0802 (gf = 0.265), and DRB1*1402 (gf = 0.303). The HLA class II allele frequencies were similar among the different Argentinian tribes, and 90% of DRB1 alleles belonged to three families: DRB1*04 (including DRB1*0403, DRB1*0404, DRB1*0407, DRB1*0411, and DRB1*0417), DRB1*0802, and DRB1*14 (including DRB1*1402 and DRB1*1406). At the DPB1 locus, we found only seven alleles, the most frequent being DPB1*0402. Comparison of HLA class II alleles with those of North American Indians that we have previously studied shows that the frequency of some HLA class II alleles in Brazilian Xavantes resembles that of North American Indians more than that of the Argentinian Indian tribes. The allele DRB1*0417 was found exclusively in this population.