A RANGE-WIDE ECTOPARASITE SURVEY FOR ALLEGHENY WOODRATS (NEOTOMA MAGISTER)

Allegheny woodrats (Neotoma magister) are karst-specializing rodents that are rare or in conservation need in many states within their current range. Parasitism and habitat fragmentation have been suggested as primary reasons for declining populations. The presence, prevalence, and impact of ectoparasites, including fleas, ticks, and bots, is not fully understood rangewide. We collected Allegheny woodrat ectoparasites across 8 states in their range, identifying parasites via morphological and genetic means. Across contributions from 8 states, we discovered 2 woodrat-specific fleas parasitizing Allegheny woodrats: Orchopeas pennsylvanicus (all contributing states, n = 228) and Epitedia cavernicola (Indiana only, n = 9). The former was a new state record in New Jersey and Ohio. Woodrat specialists Ixodes woodi were morphologically identified as the dominant tick species (n = 38), and our contributions to genetic databases may ease confusion in future efforts. Three generalist species of ticks representing 8 individuals were identified as Dermacentor variabilis, Amblyomma americanum, and Ixodes scapularis. Only 2 bot fly species were recognized in Allegheny woodrats: 1 squirrel bot (Cuterebra emasculator) and 10 individuals of Cuterebra sp. not genetically conspecific to any known eastern U.S. rodent bot. The host specificity for fleas is not surprising, given that previous small-scale surveys and ticks primarily appear to be a mix of genus-specific (Ixodes woodi) and generalist species. There remains uncertainty with bots via morphological and genetic analyses. Our survey presents a wide-ranging baseline survey for Allegheny woodrats across their range, emphasizing the diversity (or specificity) of parasite groups for this species. An understanding of Allegheny woodrats and the health impact of ectoparasites is imperative because they face myriad challenges rangewide, especially considering the bot-driven demise of 1 woodrat in our study. Ectoparasites can have a marked impact on already-declining woodrat populations across their range and should not be overlooked in future surveys.

Long-term spring through fall capture data of Eptesicus fuscus in the eastern USA before and after white-nose syndrome

Emerging infectious diseases threaten wildlife populations. Without well monitored wildlife systems, it is challenging to determine accurate population and ecosystem losses following disease emergence. North American temperate bats present a unique opportunity for studying the broad impacts of wildlife disease emergence, as their federal monitoring programs were prioritized in the USA throughout the 20th century and they are currently threatened by the invasive fungal pathogen, Pseudogymnoascus destructans (Pd), which causes white-nose syndrome. Here we provide a long-term dataset for capture records of Eptesicus fuscus (big brown bat) across the eastern USA, spanning 16 years before and 14 years after Pd invasion into North America. These data represent 30,496 E. fuscus captures across 3,567 unique sites. We encourage the use of this dataset for quantifying impacts of wildlife disease and other threats to wildlife (e.g., climate change) with the incorporation of other available data. We welcome additional data contributions for E. fuscus captures across North and Central America as well as the inclusion of other variables into the dataset that contribute to the quantification of wildlife health.

Fall migration, oceanic movement, and site residency patterns of eastern red bats (Lasiurus borealis) on the mid-Atlantic Coast

Along the mid-Atlantic coast of the United States, eastern red bats (Lasiurus borealis) are present during fall mating and migration, though little is currently known about most aspects of bat migration. To reveal migration patterns, and understand drivers of over-water flight, we captured and radio-tagged 115 eastern red bats using novel technology, and subsequently tracked and described their movements throughout the region. We compared over-water flight movements to randomly generated patterns using a use-availability framework, and subsequently used a generalized linear mixed effects model to assess the relationship of over-water flight to atmospheric variables. We used hidden Markov models to assess daily activity patterns and site residency. Most bats with long-distance movements traveled in a southwesterly direction, however path vectors were often oriented interior toward the continental landmass rather than along the coastline. We observed that some bats transited wide sections of the Chesapeake and Delaware bays, confirming their ability to travel across large water bodies. This over-water flight typically occurred in the early hours of the night and during favorable flying conditions. If flight over large water bodies is a proxy for over-ocean flight, then collision risk at offshore wind turbines - a major source of migratory bat fatalities - may be linked nightly to warm temperatures that occur early in the fall season. Risk, then, may be somewhat predictable and manageable with mitigation options linking wind-energy operation to weather conditions and seasonality.

Hypertension severity, apparent treatment resistant hypertension and hyperuricemia in the REasons for Geographic And Racial Differences in Stroke (REGARDS) study

BACKGROUND

Prior studies have identified an association between hypertension and hyperuricemia; however, there has been limited research on the association between hypertension severity and hyperuricemia.

METHOD

We studied 997 Black and white adults with serum urate data from the reasons for geographic and racial differences in stroke (REGARDS) study. Hypertension was defined as SBP ≥ 140 mmHg or DBP ≥ 90 mmHg or self-reported use of antihypertensive medication. Apparent treatment-resistant hypertension (aTRH) was defined as a SBP ≥ 140 mmHg or DBP ≥ 90 mmHg with concurrent use of three classes of antihypertensive medications, or taking four or more classes of antihypertensive medication regardless of BP level. Controlled BP was defined as SBP <140 mmHg and DBP <90 mmHg.

RESULTS

Overall 5.9% of participants had aTRH and 36.6% had hyperuricemia, defined as serum urate >7.0 mg/dl for men and >6.0 mg/dl for women. After full multivariable adjustment, the odds ratio (OR) for hyperuricemia associated with hypertension was 1.60 [95% confidence interval (95% CI): 1.06-2.40]. Compared to participants not taking antihypertensive medication, the ORs for hyperuricemia for participants taking one, two and three classes of antihypertensive medication without aTRH were 1.98 (95% CI: 1.23-3.20), 2.08 (95% CI: 1.25-3.43), 4.31 (95% CI: 2.07-8.97), respectively, and 3.96 (95% CI: 1.75-8.96) for aTRH. Compared to participants without hypertension, the odds ratios for hyperuricemia were 1.67 (95% CI: 1.08-2.58) and 1.46 (95% CI: 0.88-2.44) among those with hypertension with and without controlled BP, respectively. Diuretic use was associated with a higher odds of hyperuricemia.

CONCLUSION

This study suggests that individuals taking more classes of antihypertensive medication may benefit from monitoring for hyperuricemia.

Association of Gout Polygenic Risk Score With Age at Disease Onset and Tophaceous Disease in European and Polynesian Men With Gout

OBJECTIVE

To determine whether a gout polygenic risk score (PRS) is associated with age at gout onset and tophaceous disease in European, East Polynesian, and West Polynesian men and women with gout.

METHODS

A 19-variant gout PRS was produced in 7 European gout cohorts (N = 4,016), 2 East Polynesian gout cohorts (N = 682), and 1 West Polynesian gout cohort (N = 490). Sex-stratified regression models were used to estimate the relationship between the PRS and age at gout onset and tophaceous disease.

RESULTS

The PRS was associated with earlier age at gout onset in men (β = -3.61 in years per unit PRS [95% confidence interval (95% CI) -4.32, -2.90] in European men; β = -6.35 [95% CI -8.91, -3.80] in East Polynesian men; β = -3.51 [95% CI -5.46, -1.57] in West Polynesian men) but not in women (β = 0.07 [95% CI -2.32, 2.45] in European women; β = 0.20 [95% CI -7.21, 7.62] in East Polynesian women; β -3.33 [95% CI -9.28, 2.62] in West Polynesian women). The PRS showed a positive association with tophaceous disease in men (odds ratio [OR] for the association 1.15 [95% CI 1.00, 1.31] in European men; OR 2.60 [95% CI 1.66, 4.06] in East Polynesian men; OR 1.53 [95% CI 1.07, 2.19] in West Polynesian men) but not in women (OR for the association 0.68 [95% CI 0.42, 1.10] in European women; OR 1.45 [95% CI 0.39, 5.36] in East Polynesian women). The PRS association with age at gout onset was robust to the removal of ABCG2 variants from the PRS in European and East Polynesian men (β = -2.42 [95% CI -3.37, -1.46] and β = -6.80 [95% CI -10.06, -3.55], respectively) but not in West Polynesian men (β = -1.79 [95% CI -4.74, 1.16]).

CONCLUSION

Genetic risk variants for gout also harbor risk for earlier age at gout onset and tophaceous disease in European and Polynesian men. Our findings suggest that earlier gout onset involves the accumulation of gout risk alleles in men but perhaps not in women, and that this genetic risk is shared across multiple ancestral groups.

SMOC2 gene interacts with APOL1 in the development of end-stage kidney disease: A genome-wide association study

Background

Some but not all African-Americans (AA) who carry APOL1 nephropathy risk variants (APOL1) develop kidney failure (end-stage kidney disease, ESKD). To identify genetic modifiers, we assessed gene-gene interactions in a large prospective cohort of the REasons for Geographic and Racial Differences in Stroke (REGARDS) study.

Methods

Genotypes from 8,074 AA participants were obtained from Illumina Infinium Multi-Ethnic AMR/AFR Extended BeadChip. We compared 388 incident ESKD cases with 7,686 non-ESKD controls, using a two-locus interaction approach. Logistic regression was used to examine the effect of APOL1 risk status (using recessive and additive models), single nucleotide polymorphism (SNP), and APOL1^*SNP interaction on incident ESKD, adjusting for age, sex, and ancestry. APOL1 ^*SNP interactions that met the threshold of 1.0 × 10^-5 were replicated in the Genetics of Hypertension Associated Treatment (GenHAT) study (626 ESKD cases and 6,165 controls). In a sensitivity analysis, models were additionally adjusted for diabetes status. We conducted additional replication in the BioVU study.

Results

Two APOL1 risk alleles prevalence (recessive model) was similar in the REGARDS and GenHAT studies. Only one APOL1-SNP interaction, for rs7067944 on chromosome 10, ~10 KB from the PCAT5 gene met the genome-wide statistical threshold (P _interaction = 3.4 × 10^-8), but this interaction was not replicated in the GenHAT study. Among other relevant top findings (with P _interaction < 1.0 × 10^-5), a variant (rs2181251) near SMOC2 on chromosome six interacted with APOL1 risk status (additive) on ESKD outcomes (REGARDS study, P _interaction =5.3 × 10^-6) but the association was not replicated (GenHAT study, P _interaction = 0.07, BioVU study, P _interaction = 0.53). The association with the locus near SMOC2 persisted further in stratified analyses. Among those who inherited ≥1 alternate allele of rs2181251, APOL1 was associated with an increased risk of incident ESKD (OR [95%CI] = 2.27[1.53, 3.37]) but APOL1 was not associated with ESKD in the absence of the alternate allele (OR [95%CI] = 1.34[0.96, 1.85]) in the REGARDS study. The associations were consistent after adjusting for diabetes.

Conclusion

In a large genome-wide association study of AAs, a locus SMOC2 exhibited a significant interaction with the APOL1 locus. SMOC2 contributes to the progression of fibrosis after kidney injury and the interaction with APOL1 variants may contribute to an explanation for why only some APOLI high-risk individuals develop ESKD.

Local genetic covariance between serum urate and kidney function estimated with Bayesian multitrait models

Hyperuricemia (serum urate &gt;6.8 mg/dl) is associated with several cardiometabolic and renal diseases, such as gout and chronic kidney disease. Previous studies have examined the shared genetic basis of chronic kidney disease and hyperuricemia in humans either using single-variant tests or estimating whole-genome genetic correlations between the traits. Individual variants typically explain a small fraction of the genetic correlation between traits, thus the ability to map pleiotropic loci is lacking power for available sample sizes. Alternatively, whole-genome estimates of genetic correlation indicate a moderate correlation between these traits. While useful to explain the comorbidity of these traits, whole-genome genetic correlation estimates do not shed light on what regions may be implicated in the shared genetic basis of traits. Therefore, to fill the gap between these two approaches, we used local Bayesian multitrait models to estimate the genetic covariance between a marker for chronic kidney disease (estimated glomerular filtration rate) and serum urate in specific genomic regions. We identified 134 overlapping linkage disequilibrium windows with statistically significant covariance estimates, 49 of which had positive directionalities, and 85 negative directionalities, the latter being consistent with that of the overall genetic covariance. The 134 significant windows condensed to 64 genetically distinct shared loci which validate 17 previously identified shared loci with consistent directionality and revealed 22 novel pleiotropic genes. Finally, to examine potential biological mechanisms for these shared loci, we have identified a subset of the genomic windows that are associated with gene expression using colocalization analyses. The regions identified by our local Bayesian multitrait model approach may help explain the association between chronic kidney disease and hyperuricemia.

APOL1 Risk Variants Associated with Serum Albumin in a Population-Based Cohort Study

INTRODUCTION

The association of apolipoprotein L1 (APOL1) nephropathy risk variants (APOL1), unique to African-ancestry (African-American [AA]) populations, with systemic inflammation, a contributor to chronic kidney disease (CKD) and end-stage kidney disease (ESKD) is ill-defined. This study aimed to describe the role of inflammatory markers in the relationship between APOL1 and incident kidney outcomes using a prospective cohort study.

METHODS

APOL1 high-risk status under a recessive genetic model was studied in 10,605 AA adults aged ≥45 years from the Reasons for Geographic and Racial Differences in Stroke study. The primary variables of interest were inflammatory markers: C-reactive protein (mg/dL), white blood cell count (cells/mm3), and serum albumin (sALB) (mg/dL). High inflammation status was defined if at least one of these inflammatory markers exceeded clinical threshold. The association between APOL1 and biomarkers were assessed using regression models adjusting for age, sex, ancestry, hypertension, lipid medications, albumin-to-creatinine ratio, and estimated glomerular filtration rate (eGFR). Models were stratified by diabetes status. We identified incident ESKD using USRDS linkage, and we defined incident CKD as an eGFR <60 mL/min/1.73 m2 and ≥25% decline in the eGFR and normal baseline eGFR and tested for mediation of APOL1 and outcomes by biomarkers using the causal inference approach.

RESULTS

Among 7,151 participants with data available on all inflammation markers, 4,479 participants had ≥1 marker meeting the clinical threshold. APOL1 high-risk status was associated with lower adjusted odds of reduced sALB {odds ratio (OR) (95% confidence interval [CI]): 0.59 [0.36, 0.96])}, and this association was significant in people with diabetes (OR [95% CI]: 0.40 [0.18, 0.89]) but not in those without diabetes. There was no association of APOL1 high-risk status with other markers or high inflammation status. APOL1 was independently associated with ESKD (OR [95% CI] = 1.78 [1.28, 2.48]) and CKD (OR [95% CI] = 1.38 [1.00, 1.91]). On mediation analysis, the direct effect between APOL1 and ESKD strengthened after accounting for sALB, but the estimated mediated effect was not statistically significant (OR [95% CI]: 0.98 [0.92, 1.05], p = 0.58).

CONCLUSION

APOL1 high-risk variants were associated with sALB. However, sALB did not statistically mediate the association between APOL1 and incident ESKD.

The scope and severity of white-nose syndrome on hibernating bats in North America

Assessing the scope and severity of threats is necessary for evaluating impacts on populations to inform conservation planning. Quantitative threat assessment often requires monitoring programs that provide reliable data over relevant spatial and temporal scales, yet such programs can be difficult to justify until there is an apparent stressor. Leveraging efforts of wildlife management agencies to record winter counts of hibernating bats, we collated data for 5 species from over 200 sites across 27 U.S. states and 2 Canadian provinces from 1995 to 2018 to determine the impact of white-nose syndrome (WNS), a deadly disease of hibernating bats. We estimated declines of winter counts of bat colonies at sites where the invasive fungus that causes WNS (Pseudogymnoascus destructans) had been detected to assess the threat impact of WNS. Three species undergoing species status assessment by the U.S. Fish and Wildlife Service (Myotis septentrionalis, Myotis lucifugus, and Perimyotis subflavus) declined by more than 90%, which warrants classifying the severity of the WNS threat as extreme based on criteria used by NatureServe. The scope of the WNS threat as defined by NatureServe criteria was large (36% of Myotis lucifugus range) to pervasive (79% of Myotis septentrionalis range) for these species. Declines for 2 other species (Myotis sodalis and Eptesicus fuscus) were less severe but still qualified as moderate to serious based on NatureServe criteria. Data-sharing across jurisdictions provided a comprehensive evaluation of scope and severity of the threat of WNS and indicated regional differences that can inform response efforts at international, national, and state or provincial jurisdictions. We assessed the threat impact of an emerging infectious disease by uniting monitoring efforts across jurisdictional boundaries and demonstrated the importance of coordinated monitoring programs, such as the North American Bat Monitoring Program (NABat), for data-driven conservation assessments and planning.

Higher Serum Urate Levels Are Associated With an Increased Risk for Sudden Cardiac Death

OBJECTIVE

To determine the association of serum urate (SU) levels with sudden cardiac death and incident coronary heart disease (CHD), separately, among adults without a history of CHD.

METHODS

We conducted a case-cohort analysis of Black and White participants aged ≥ 45 years enrolled in the REason for Geographic And Racial Differences in Stroke (REGARDS) study without a history of CHD at baseline between 2003 and 2007. Participants were followed for sudden cardiac death or incident CHD (i.e., myocardial infarction [MI] or death from CHD excluding sudden cardiac death) through December 31, 2013. Baseline SU was measured in a random sample of participants (n = 840) and among participants who experienced sudden cardiac death (n = 235) or incident CHD (n = 851) during follow-up.

RESULTS

Participants with higher SU levels were older and more likely to be male or Black. The crude HR (95% CI) per 1 mg/dL higher SU level was 1.26 (1.14-1.40) for sudden cardiac death and 1.17 (1.09-1.26) for incident CHD. After adjustment for age, sex, race, and cardiovascular risk factors, the HR (95% CI) per 1 mg/dL higher SU level was 1.19 (1.03-1.37) for sudden cardiac death and 1.05 (0.96-1.15) for incident CHD. HRs for sudden cardiac death were numerically higher among participants aged 45-64 vs ≥ 65 years, without vs with diabetes, and among those of White vs Black race, although P values for effect modification were all ≥ 0.05.

CONCLUSION

Higher SU levels were associated with an increased risk for sudden cardiac death but not with incident CHD.

Decreased Levels of STAT1 and Interferon-γ-Induced STAT1 Phosphorylation in Rheumatoid Arthritis CD4 and CD8 T Cells

Objective

We investigated whether a previously reported association of IFNGR expression with rheumatoid arthritis (RA) and its radiographic severity reflects differences in proximal interferon‐γ (IFN‐γ) signaling in T cells from patients with RA compared with healthy controls (HC).

Methods

Using phosphoflow cytometry, we compared IFN‐γ–stimulated signal transducer and activator of transcription 1 (STAT1) activation in CD4⁺ and CD8⁺ T‐cell populations from patients with RA and HC.

Results

Compared with controls, patients with RA had a higher proportion of CD4⁺ T cells, associated with expansion of the CD4⁺ effector memory subset. Several CD4⁺ T‐cell types exhibited reduced IFN‐γ–induced phosphoSTAT1^Y701 (pSTAT1^Y701) in patients with RA compared with HC. Engaging the T‐cell receptor (TCR) complex on CD4⁺ T cells during IFN‐γ stimulation abrogated the reduction in STAT1 activation in patients with RA but had no effect in HC. The phosphorylation of STAT1^S727 was similar in CD4⁺ T cells from patients with RA and HC. In contrast to CD4⁺ T cells, IFN‐γ–induced pSTAT1^Y701 levels in CD8⁺ T cells were equivalent or higher in patients with RA compared with HC. Total STAT1 levels (phosphorylated + unphosphorylated) were lower in CD4⁺ and CD8⁺ T cells from patients with RA compared with HC.

Conclusion

We report diminished IFN‐γ–induced pSTAT1^Y701 levels in CD4⁺ T cells in patients with RA, which were restored by TCR engagement. There were lower levels of total STAT1 in patients with RA compared with HC, but this likely does not explain diminished IFN‐γ–induced pSTAT1^Y701 levels in CD4⁺ T cells because activation in CD8⁺ T cells was higher or equivalent to that seen in HC. The enhanced IFNGR expression in patients with RA reported previously may reflect a compensatory mechanism to overcome deficiency in IFN‐γ responsiveness.

Genetic correlations between traits associated with hyperuricemia, gout, and comorbidities

Hypertension, obesity, chronic kidney disease and type 2 diabetes are comorbidities that have very high prevalence among persons with hyperuricemia (serum urate > 6.8 mg/dL) and gout. Here we use multivariate genetic models to test the hypothesis that the co-association of traits representing hyperuricemia and its comorbidities is genetically based. Using Bayesian whole-genome regression models, we estimated the genetic marker-based variance and the covariance between serum urate, serum creatinine, systolic blood pressure (SBP), blood glucose and body mass index (BMI) from two independent family-based studies: The Framingham Heart Study-FHS and the Hypertension Genetic Epidemiology Network study-HyperGEN. The main genetic findings that replicated in both FHS and HyperGEN, were (1) creatinine was genetically correlated only with urate and (2) BMI was genetically correlated with urate, SBP, and glucose. The environmental covariance among the traits was generally highest for trait pairs involving BMI. The genetic overlap of traits representing the comorbidities of hyperuricemia and gout appears to cluster in two separate axes of genetic covariance. Because creatinine is genetically correlated with urate but not with metabolic traits, this suggests there is one genetic module of shared loci associated with hyperuricemia and chronic kidney disease. Another module of shared loci may account for the association of hyperuricemia and metabolic syndrome. This study provides a clear quantitative genetic basis for the clustering of comorbidities with hyperuricemia.

The comparative effect of exposure to various risk factors on the risk of hyperuricaemia: diet has a weak causal effect

BACKGROUND

Prevention of hyperuricaemia (HU) is critical to the prevention of gout. Understanding causal relationships and relative contributions of various risk factors to hyperuricemia is therefore important in the prevention of gout. Here, we use attributable fraction to compare the relative contribution of genetic, dietary, urate-lowering therapy (ULT) and other exposures to HU. We use Mendelian randomisation to test for the causality of diet in urate levels.

METHODS

Four European-ancestry sample sets, three from the general population (n = 419,060) and one of people with gout (n = 6781) were derived from the Database of Genotypes and Phenotypes (ARIC, FHS, CARDIA, CHS) and UK Biobank. Dichotomised exposures to diet, genetic risk variants, BMI, alcohol, diuretic treatment, sex and age were used to calculate adjusted population and average attributable fractions (PAF/AAF) for HU (≥0.42 mmol/L [≥7 mg/dL]). Exposure to ULT was also assessed in the gout cohort. Two sample Mendelian randomisation was done in the UK Biobank using dietary pattern-associated genetic variants as exposure and serum urate levels as outcome.

RESULTS

Adherence to dietary recommendations, BMI (< 25 kg/m²), and absence of the SLC2A9 rs12498742 urate-raising allele produced PAFs for HU of 20 to 24%, 59 to 69%, and 57 to 64%, respectively, in the three non-gout cohorts. In the gout cohort, diet, BMI, SLC2A9 rs12498742 and ULT PAFs for HU were 12%, 49%, 48%, and 63%, respectively. Mendelian randomisation demonstrated weak causal effects of four dietary habits on serum urate levels (e.g. preferentially drinking skim milk increased urate, β = 0.047 mmol/L, P = 3.78 × 10^-8). These effects were mediated by BMI, and they were not significant (P ≥ 0.06) in multivariable models assessing the BMI-independent effect of diet on urate.

CONCLUSIONS

Diet has a relatively minor role in determining serum urate levels and HU. In gout, the use of ULT was the largest attributable fraction tested for HU.

Gout is associated with an increased risk for incident heart failure among older adults: the REasons for Geographic And Racial Differences in Stroke (REGARDS) cohort study

Background

Gout has been associated with a higher risk for coronary heart disease (CHD) and stroke in some prior studies. Few studies have assessed the association of gout with incident heart failure (HF).

Methods

We analyzed data from 5713 black and white men and women ≥ 65.5 years of age in the population-based REasons for Geographic And Racial Differences in Stroke (REGARDS) cohort study who had Medicare coverage without a history of HF, CHD, or stroke at baseline between 2003 and 2007. Gout was defined by ≥ 1 hospitalization or ≥ 2 outpatient visits with a diagnosis code for gout in Medicare claims prior to each participant’s baseline study examination. REGARDS study participants were followed for HF hospitalization, CHD, stroke, and all-cause mortality as separate outcomes through December 31, 2016. Analyses were replicated in a random sample of 839,059 patients ≥ 65.5 years of age with Medicare coverage between January 1, 2008, and June 30, 2015, who were followed through December 31, 2017.

Results

Among REGARDS study participants included in the current analysis, the mean age at baseline was 72.6 years, 44.9% were men, 31.4% were black, and 3.3% had gout. Over a median follow-up of 10.0 years, incidence rates per 1000 person-years among participants with and without gout were 13.1 and 4.4 for HF hospitalization, 16.0 and 9.3 for CHD, 9.3 and 8.2 for stroke, and 55.0 and 37.1 for all-cause mortality, respectively. After multivariable adjustment for sociodemographic variables and cardiovascular risk factors, hazard ratios (95% CI) comparing participants with versus without gout were 1.97 (1.22, 3.19) for HF hospitalization, 1.21 (0.79, 1.84) for CHD, 0.83 (0.48, 1.43) for stroke, and 1.08 (0.86, 1.35) for all-cause mortality. The multivariable-adjusted hazard ratio for HF hospitalization with reduced and preserved left ventricular ejection fraction among participants with versus without gout was 1.77 (95% CI 0.83, 3.79) and 2.32 (95% CI 1.12, 4.79), respectively. The multivariable-adjusted hazard ratio for heart failure hospitalization associated with gout among the 839,059 Medicare beneficiaries was 1.32 (95% CI 1.25, 1.39).

Conclusion

Among older adults, gout was associated with an increased risk for incident HF but not for incident CHD, incident stroke, or all-cause mortality.

Genetic influences on susceptibility to rheumatoid arthritis in African-Americans

Large meta-analyses of rheumatoid arthritis (RA) susceptibility in European (EUR) and East Asian (EAS) populations have identified >100 RA risk loci, but genome-wide studies of RA in African-Americans (AAs) are absent. To address this disparity, we performed an analysis of 916 AA RA patients and 1392 controls and aggregated our data with genotyping data from >100 000 EUR and Asian RA patients and controls. We identified two novel risk loci that appear to be specific to AAs: GPC5 and RBFOX1 (PAA < 5 × 10-9). Most RA risk loci are shared across different ethnicities, but among discordant loci, we observed strong enrichment of variants having large effect sizes. We found strong evidence of effect concordance for only 3 of the 21 largest effect index variants in EURs. We used the trans-ethnic fine-mapping algorithm PAINTOR3 to prioritize risk variants in >90 RA risk loci. Addition of AA data to those of EUR and EAS descent enabled identification of seven novel high-confidence candidate pathogenic variants (defined by posterior probability > 0.8). In summary, our trans-ethnic analyses are the first to include AAs, identified several new RA risk loci and point to candidate pathogenic variants that may underlie this common autoimmune disease. These findings may lead to better ways to diagnose or stratify treatment approaches in RA.

Severity of Hypertension Mediates the Association of Hyperuricemia With Stroke in the REGARDS Case Cohort Study

Previous studies do not widely support hyperuricemia as a risk factor for stroke and other cardiovascular diseases. We assessed the relationship between hyperuricemia and ischemic stroke (≈900 cases) using a large data set from the REGARDS study (Reasons for Geographic and Racial Differences in Stroke). We employed a case-cohort design (incident stroke cases and randomly selected cohort participants) and weighted Cox-proportional hazard models to estimate the association of serum urate level ≥6.8 mg/dL (ie, hyperuricemia) and 6.0 to <6.8 mg/dL versus <6.0 mg/dL (reference) with incident stroke. Analyses were stratified by race, gender, and age. Mediation of cardiovascular disease comorbidities on the serum urate-stroke association was tested. Hyperuricemia was associated with stroke (hazard ratio, 1.40 [95% CI, 1.10-1.78]) after adjustment for demographic variables and systolic and diastolic blood pressure. This association was substantially attenuated (hazard ratio, 1.17 [95% CI, 0.90-1.51]) by additional covariate adjustment. In particular, apparent treatment-resistant hypertension (systolic blood pressure ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg on 3 antihypertensive medications or use of ≥4 antihypertensive medications) and the count of antihypertensive medication classes significantly reduced the effect of hyperuricemia on ischemic stroke. Specifically, apparent treatment-resistant hypertension and number of antihypertensive, respectively, mediate 45% and 43% of the association. There was no effect modification in the association between hyperuricemia and stroke by age, race, or gender. We conclude that hyperuricemia may be a risk factor for stroke. The substantial attenuation of this association by apparent treatment-resistant hypertension and number of antihypertensive suggests that severe hypertension may be a mediator.

Abstract 188: Association Between Uric Acid and Stroke in the REgards Case-cohort Study

Introduction: The association between hyperuricemia and stroke has been inconsistent especially after adjustment for cardiovascular risk factors. Previous studies were limited in the number of events and did not measure these associations in subgroups.

Methods: We used a stratified case-cohort design within the REasons for Geographic and Racial Differences in Stroke study. Clinically adjudicated stroke events (n=903) were defined as focal neurologic deficit lasting >24 hours or non-focal neurological symptoms with brain imaging consistent with stroke. Controls (n=951) were a random stratified sample selected from baseline to ensure representation of high-risk groups. Uric acid was assayed using the baseline sample and categorized into three groups: < 6 (referent), 6-6.8, ≥ 6.8 mg/dl (hyperuricemia). Cox-proportional-hazard-models adjusted for demographic and clinical variables were fit to examine the association between uric acid levels and stroke. We repeated the analysis stratified by race, gender, and age (</≥ 65years) and finally, since uric acid is associated with hypertension, explored the count of antihypertensive treatment classes (nHTN) as a potential mediator.

Results: Hyperuricemic individuals were more likely to be male and black. Hyperuricemia versus the referent category was significantly associated with stroke after adjustment for race, sex, age, and age*race interaction [model 1 HR(95%CI)= 1.42(1.12-1.80)], and after further adjustment for systolic and diastolic blood pressure [HR (95%CI)= 1.42(1.12-1.80)]. The associations was attenuated after full adjustment [HR (95%CI)= 1.22(0.91-1.63)]. Incremental adjustment by clinical variables suggested nHTN attenuated the association between hyperuricemia and stroke. Results were similar for hyperuricemia within subgroups defined by age, gender and race, except among men <65 years [HR (95%CI)= 2.72(1.25-5.93)]. Mediation analysis estimated that nHTN accounted for 43%(95%CI: 15 to 158%) of the relationship.

Conclusion: We observed a significant association between hyperuricemia and stroke that was partially dependent upon hypertension severity (count of antihypertensive treatment classes). The association was strongest among males aged <65 years.

HLA-DRB1 Amino Acid Positions and Residues Associated with Antibody-positive Rheumatoid Arthritis in Black South Africans

OBJECTIVE

To investigate the association of specific amino acid positions, residues, and haplotypes of HLA-DRB1 in black South Africans with autoantibody-positive rheumatoid arthritis (RA).

METHODS

High-resolution HLA-DRB1 genotyping was performed in 266 black South Africans with autoantibody-positive RA and 362 ethnically and geographically matched controls. The alleles were converted to specific amino acid residues at polymorphic sites for downstream analyses. Logistic regression models were used to test whether variability at site, specific amino acid residues, and haplotypes (constructed from positions 11, 71, and 74) were associated with RA.

RESULTS

Of the 29 amino acid positions examined, positions 11, 13, and 33 (permutation p = 3.4^e-26, 1.2^e-27, and 2.1^e-28, respectively) showed the strongest association with RA. Univariate analyses of individual amino acid residues showed valine at position 11 (OR 5.1, 95% CI 3.7-7.0) and histidine at position 13 (OR 6.1, 95% CI 4.2-8.6) conferred the highest risk. The valine containing haplotypes of position 11, 71, 74, V_K_A conferred the most risk (OR 4.52, 95% CI 2.68-7.61) and conversely the haplotype with serine at this position, S_K_R, conferred the most protection (OR 0.83, 95% CI 0.61-1.15).

CONCLUSION

Autoantibody-positive RA in black South Africans is associated with histidine at position 13 and valine at position 11 of HLA-DRB1, and haplotypes with valine at position 11 conferred the highest risk; conversely, serine at position 11 conveyed protection.

Untangling the complex relationships between incident gout risk, serum urate, and its comorbidities

BACKGROUND

Many gout comorbidities (e.g., hypertension) are correlated with serum urate. In this investigation, we identified risk factors (e.g., systolic blood pressure [SBP]), that (1) are associated with incident gout, (2) have effects on gout risk that cannot be fully explained by correlated differences in serum urate, and (3) may modulate the relationship between gout and serum urate.

METHODS

Using data from the Atherosclerosis Risk in Communities (ARIC) study, we estimated the unadjusted associations between gout and risk factors by calculating ORs and using chi-square tests. The adjusted associations were analyzed using logistic regression by sequentially adding (1) one risk factor at a time or (2) all risk factors, to a baseline model that includes serum urate only. Stepwise selection was used to select main effects. Two-way interactions of variables from the main effects model were also analyzed.

RESULTS

Average gout incidence was 2.7 per 1000 people per year. Serum urate was highly associated with incident gout, with odd ratios of 3.16 [95% CI 2.11, 4.76] and 25.9 [95% CI 17.2, 38.4] for moderately high (6-8 mg/dl) and high serum urate (> 8 mg/dl), relative to normal serum urate (< 6 mg/dl), respectively. Ethnicity and SBP were independently and additively associated with gout after accounting for serum urate levels. No significant interactions were found between serum urate and ethnicity or SBP.

CONCLUSIONS

Ethnicity and hypertension are predictive of gout risk, and the associations cannot be fully explained by serum urate. For serum urate levels near the crystallization threshold (6-8 mg/dl) African Americans and people with hypertension are at two to three times greater risk for developing gout. The gout risk for this group appears to increase before the onset of severe hyperuricemia.

Coronary Artery Calcification and Rheumatoid Arthritis: Lack of Relationship to Risk Alleles for Coronary Artery Disease in the General Population

OBJECTIVE

Coronary artery disease (CAD) in the general population is characterized by an increased frequency of particular susceptibility single-nucleotide polymorphisms (SNPs). Because the frequency of CAD is increased among patients with rheumatoid arthritis (RA), we sought to determine whether the frequency of these SNPs is increased in RA patients with CAD, hypothesizing that RA could enhance CAD risk by acting through established genetic pathways predisposing to CAD.

METHODS

Coronary artery calcification (CAC) as detected by computed tomography was used as a measure of CAD in 561 patients with RA. One hundred SNPs associated with CAD in the general population were genotyped or imputed, and their relationship to CAC was established through multiple regression analysis for individual SNPs and a genetic risk score representing their cumulative effect.

RESULTS

Ninety-one CAD-related SNPs were genotyped successfully; of these, 81 exhibited no association with CAC (Agatston units) or different CAC categorizations, either individually or collectively, in the genetic risk score. Only rs579459 (ABO) and rs17676451 (HAL) had a consistent positive association between genotype and CAC, with a significant increase in the frequency of the effect allele in both homozygous and heterozygous genotype distributions. Five were variably negatively associated. Furthermore, a positive association between the Disease Activity Score in 28 joints and CAC was observed, and after adjustment for traditional cardiovascular risk factors, it was not modified by correcting for the CAD-related SNP genetic risk score.

CONCLUSION

The increased risk of CAC in patients with RA does not appear to operate primarily through established genetically regulated atherogenic mechanisms that are preponderant in the general population.

Dense Genotyping of Immune-Related Regions Identifies Loci for Rheumatoid Arthritis Risk and Damage in African Americans

Over 100 risk loci for rheumatoid arthritis (RA) have been identified in individuals of European and Asian descent, but the genetic basis for RA in African Americans is less well understood. We genotyped 610 African Americans with autoantibody positive RA and 933 African American controls on the ImmunoChip (iChip) array. Using multivariable regression we evaluated the association between iChip markers and the risk of RA and radiographic severity. The single nucleotide polymorphism (SNP) rs1964995 (OR = 1.97, p = 1.28 × 10^-15) near HLA-DRB1 was the most strongly associated risk SNP for RA susceptibility; SNPs in AFF3, TNFSF11, and TNFSF18 loci were suggestively associated (10^-4 < p < 3.1 × 10^-6). Trans-ethnic fine mapping of AFF3 identified a 90% credible set containing previously studied variants including rs9653442, rs7608424, and rs6712515 as well as the novel candidate variant rs11681966; several of these likely influence AFF3 gene expression level. Variants in TNFRSF9, CTLA4, IL2RA, C5/TRAF1, and ETS1 - but no variants within the major histocompatibility complex - were associated with RA radiographic severity. Conditional regression and pairwise linkage disequilibrium (LD) analyses suggest that additional pathogenic variants may be found in ETS1 and IL2RA beyond those found in other ethnicities. In summary, we use the dense genotyping of the iChip array and unique LD structure of African Americans to validate known risk loci for RA susceptibility and radiographic severity, and to better characterize the associations of AFF3, ETS1, and IL2RA.

Association of anti-peptidyl arginine deiminase antibodies with radiographic severity of rheumatoid arthritis in African Americans

Background

Evidence suggests that the presence of peptidyl arginine deiminase type 4 (PAD4) antibodies is associated with radiographic-severity rheumatoid arthritis (RA) among Caucasian patients. The presence of anti-PAD4 antibodies that were cross-reactivity against PAD3 was associated with more aggressive erosive disease (compared with the presence of anti-PAD4 antibodies without anti-PAD3 crossreactivity) in Caucasian RA patients. The objectives of this study were to determine the prevalence of serum anti-PAD4 and anti-PAD4/PAD3 cross-reactive autoantibodies in African Americans with RA and whether these antibodies associate with radiographic severity and radiographic progression.

Methods

Serum anti-PAD4 and anti-PAD4/PAD3 antibodies were measured by immunoprecipitation, and the temporal trends in titers were analyzed. We compared total radiographic scores among anti-PAD4-positive, anti-PAD4/PAD3-positive, and anti-PAD4-negative patients and used a zero-inflated negative binomial model to determine associations between radiographic severity and antibody status. Logistic regression was used to analyze radiographic progression.

Results

Of 192 African-American patients with RA, 73 % were anti-citrullinated peptide/protein antibody (ACPA)-positive, 46 out of 192 (24 %) of whom had serum anti-PAD4 antibodies. Median (interquartile range) total Sharp van der Heijde radiographic scores were 2 (1–97.5) in ACPA-positive patients and 0 (0–3) in ACPA-negative patients (P < 0.001). Of the 46 anti-PAD4-positive patients, 20 had anti-PAD4 antibodies that cross-reacted with PAD3. In patients with early RA, anti-PAD4 and anti-PAD4/PAD3 antibody titers increased over time (P = 0.006, P = 0.001, respectively). Median (interquartile range) total radiographic scores were higher for anti-PAD4-positive than for anti-PAD4-negative patients (3 (1–115) versus 2 (0–11), respectively; P = 0.005). Median (interquartile range) total radiographic score for anti-PAD4/PAD3-positive patients was 76 (3–117) (P < 0.001) versus anti-PAD4-negative patients. Only anti-PAD4/PAD3 antibodies associated with radiographic severity (incidence rate ratio = 2.81; 95 % confidence interval 1.23, 6.43).

Conclusion

This analysis suggests that autoantibodies against PAD4 and PAD3 proteins may serve as biomarkers for identifying African-American patients with RA and higher radiographic severity.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-1126-7) contains supplementary material, which is available to authorized users.

Typology as a Moderating Variable in Success in Science

Myers-Briggs Type Indicator (MBTI) was examined for its utility as a predictor of intellective behaviors. For beginning, intermediate and advanced high school students measures of GPA, IQ, science achievement, and science aptitude were obtained. MBTI subscales were dichotomized and criteria were analyzed relative to the resultant eight groups. MBTI subscales provided evidence that typology may well be a moderating factor in intellective performance. The intuition (S-N) scale provided consistent indication of typological differences moderating performance. MBTI appeared to be more appropriate for heterogeneous groups and lost its discriminatory utility with homogeneous groups.

Serum urate gene associations with incident gout, measured in the Framingham Heart Study, are modified by renal disease and not by body mass index

We hypothesized that serum urate-associated SNPs, individually or collectively, interact with BMI and renal disease to contribute to risk of incident gout. We measured the incidence of gout and associated comorbidities using the original and offspring cohorts of the Framingham Heart Study. We used direct and imputed genotypes for eight validated serum urate loci. We fit binomial regression models of gout incidence as a function of the covariates, age, type 2 diabetes, sex, and all main and interaction effects of the eight serum urate SNPs with BMI and renal disease. Models were also fit with a genetic risk score for serum urate levels which corresponds to the sum of risk alleles at the eight SNPs. Model covariates, age (P = 5.95E-06), sex (P = 2.46E-39), diabetes (P = 2.34E-07), BMI (P = 1.14E-11) and the SNPs, rs1967017 (P = 9.54E-03), rs13129697 (P = 4.34E-07), rs2199936 (P = 7.28E-03) and rs675209 (P = 4.84E-02) were all associated with incident gout. No BMI by SNP or BMI by serum urate genetic risk score interactions were statistically significant, but renal disease by rs1106766 was statistically significant (P = 6.12E-03). We demonstrated that minor alleles of rs1106766 (intergenic, INHBC) were negatively associated with the risk of incident gout in subjects without renal disease, but not for individuals with renal disease. These analyses demonstrate that a significant component of the risk of gout may involve complex interplay between genes and environment.

The role of genetic variants in CRP in radiographic severity in African Americans with early and established rheumatoid arthritis

This study investigates the association of CRP (C-reactive protein) single-nucleotide polymorphisms (SNPs) with plasma CRP levels and radiographic severity in African Americans with early and established rheumatoid arthritis (RA). Using a cross-sectional case-only design, CRP SNPs were genotyped in two independent sets of African Americans with RA: Consortium for the Longitudinal Evaluation of African Americans with RA (CLEAR 1) and CLEAR 2. Radiographic data and CRP measurements were available for 294 individuals from CLEAR 1 (median (interquartile range (IQR) 25-75) disease duration of 1 (0.6-1.6) year) and in 407 persons from CLEAR 2 (median (IQR 25-75) disease duration of 8.9 (3.5-17.7) years). In CLEAR 1, in adjusted models, the minor allele of rs2808630 was associated with total radiographic score (incident rate ratio 0.37 (95% confidence interval (CI) 0.19-0.74), P-value=0.0051). In CLEAR 2, the minor allele of rs3093062 was associated with increased plasma CRP levels (P-value=0.002). For each rs3093062 minor allele, the plasma CRP increased by 1.51 (95% CI 1.15-1.95) mg dl(-1) when all the other covariates remained constant. These findings have important implications for assessment of the risk of joint damage in African Americans with RA.

Expression of Interferon-γ Receptor Genes in Peripheral Blood Mononuclear Cells Is Associated With Rheumatoid Arthritis and Its Radiographic Severity in African Americans

OBJECTIVE

The factors responsible for radiographic severity in African American patients with rheumatoid arthritis (RA) are poorly understood. We sought to identify genes whose expression in peripheral blood mononuclear cells is associated with radiographic severity in RA.

METHODS

In the first phase of the study, we performed real-time quantitative polymerase chain reaction to analyze the expression of 182 candidate genes in 40 African American RA patients with extremes of radiographic damage (low versus high radiographic scores) and disease duration (≤2 years versus >2 years) and 20 healthy African American control subjects; the genes were selected based on plausible immune pathways. In the second phase, we analyzed the expression of the genes that were shown to be significantly associated with radiographic scores in 576 African American patients with RA and 51 African American control subjects who had not been studied previously, accounting for autoantibody status and disease duration.

RESULTS

We observed significant differences in IFNGR1 expression between patients with RA and control subjects (adjusted P [P(adj)] = 6 × 10(-14)) and in IFNGR2 expression between RA patients with erosions and those with no erosions (P(adj) = 0.01 by Wilcoxon's rank sum test). We also observed significant correlations between IFNGR2 expression and radiographic scores (P(adj) = 0.03 for erosions, P(adj) = 0.04 for joint space narrowing, and P(adj) = 0.03 for total radiographic score [zero-inflated negative binomial regression model]) and annualized progression rate (P(adj) = 0.0024 by Spearman's correlation analysis).

CONCLUSION

These findings have important implications with respect to the role of interferon-γ (IFNγ) in the pathogenesis of RA and may lead to identification of a biomarker for radiographic damage. Additional studies are needed to define the cell subsets responsible for the association of IFNγ receptor gene expression with radiographic findings, which downstream mechanisms are involved, and generalizability to other RA populations.

HLA-DRB1-associated rheumatoid arthritis risk at multiple levels in African Americans: hierarchical classification systems, amino acid positions, and residues

OBJECTIVE

To evaluate HLA-DRB1 genetic risk of rheumatoid arthritis (RA) in African Americans by 3 validated allele classification systems and by amino acid position and residue, and to compare genetic risk between African American and European ancestries.

METHODS

Four-digit HLA-DRB1 genotyping was performed on 561 autoantibody-positive African American cases and 776 African American controls. Association analysis was performed on Tezenas du Montcel (TdM), de Vries (DV), and Mattey classification system alleles and separately by amino acid position and individual residues.

RESULTS

TdM S2 and S3P alleles were associated with RA (odds ratio [95% confidence interval] 2.8 [2.0-3.9] and 2.1 [1.7-2.7], respectively). The DV (P = 3.2 × 10(-12)) and Mattey (P = 6.5 × 10(-13)) system alleles were both protective in African Americans. Amino acid position 11 (permutation P < 0.00001) accounted for nearly all variability explained by HLA-DRB1, although conditional analysis demonstrated that position 57 was also significant (0.01 ≤ permutation P ≤ 0.05). The valine and aspartic acid residues at position 11 conferred the highest risk of RA in African Americans.

CONCLUSION

With some exceptions, the genetic risk conferred by HLA-DRB1 in African Americans is similar to that in individuals of European ancestry at multiple levels: classification system (e.g., TdM), amino acid position (e.g., 11), and residue (Val11). Unlike that reported for individuals of European ancestry, amino acid position 57 was associated with RA in African Americans, but positions 71 and 74 were not. Asp11 (odds ratio 1 in European ancestry) corresponds to the 4-digit classical allele *09:01, which is also a risk allele for RA in Koreans.

Periodontitis and Porphyromonas gingivalis in patients with rheumatoid arthritis

OBJECTIVE

To examine the degree to which shared risk factors explain the relationship of periodontitis (PD) to rheumatoid arthritis (RA) and to determine the associations of PD and Porphyromonas gingivalis with pathologic and clinical features of RA.

METHODS

Patients with RA (n = 287) and patients with osteoarthritis as disease controls (n = 330) underwent a standardized periodontal examination. The HLA-DRB1 status of all participants was imputed using single-nucleotide polymorphisms from the extended major histocompatibility complex. Circulating anti-P gingivalis antibodies were measured using an enzyme-linked immunosorbent assay, and subgingival plaque was assessed for the presence of P gingivalis using polymerase chain reaction (PCR). Associations of PD with RA were examined using multivariable regression.

RESULTS

Presence of PD was more common in patients with RA and patients with anti-citrullinated protein antibody (ACPA)-positive RA (n = 240; determined using the anti-cyclic citrullinated peptide 2 [anti-CCP-2] test) than in controls (35% and 37%, respectively, versus 26%; P = 0.022 and P = 0.006, respectively). There were no differences between RA patients and controls in the levels of anti-P gingivalis or the frequency of P gingivalis positivity by PCR. The anti-P gingivalis findings showed a weak, but statistically significant, association with the findings for both anti-CCP-2 (r = 0.14, P = 0.022) and rheumatoid factor (RF) (r = 0.19, P = 0.001). Presence of PD was associated with increased swollen joint counts (P = 0.004), greater disease activity according to the 28-joint Disease Activity Score using C-reactive protein level (P = 0.045), and higher total Sharp scores of radiographic damage (P = 0.015), as well as with the presence and levels of anti-CCP-2 (P = 0.011) and RF (P < 0.001). The expression levels of select ACPAs (including antibodies to citrullinated filaggrin) were higher in patients with subgingival P gingivalis and in those with higher levels of anti-P gingivalis antibodies, irrespective of smoking status. Associations of PD with established seropositive RA were independent of all covariates examined, including evidence of P gingivalis infection.

CONCLUSION

Both PD and P gingivalis appear to shape the autoreactivity of RA. In addition, these results demonstrate an independent relationship between PD and established seropositive RA.

Immunochip identifies novel, and replicates known, genetic risk loci for rheumatoid arthritis in black South Africans

The aim of this study was to identify genetic variants associated with rheumatoid arthritis (RA) risk in black South Africans. Black South African RA patients (n = 263) were compared with healthy controls (n = 374). Genotyping was performed using the Immunochip, and four-digit high-resolution human leukocyte antigen (HLA) typing was performed by DNA sequencing of exon 2. Standard quality control measures were implemented on the data. The strongest associations were in the intergenic region between the HLA-DRB1 and HLA-DQA1 loci. After conditioning on HLA-DRB1 alleles, the effect in the rest of the extended major histocompatibility (MHC) diminished. Non-HLA single nucleotide polymorphisms (SNPs) in the intergenic regions LOC389203|RBPJ, LOC100131131|IL1R1, KIAA1919|REV3L, LOC643749|TRAF3IP2, and SNPs in the intron and untranslated regions (UTR) of IRF1 and the intronic region of ICOS and KIAA1542 showed association with RA (p < 5 × 10(-5)). Of the SNPs previously associated with RA in Caucasians, one SNP, rs874040, locating to the intergenic region LOC389203|RBPJ was replicated in this study. None of the variants in the PTPN22 gene was significantly associated. The seropositive subgroups showed similar results to the overall cohort. The effects observed across the HLA region are most likely due to HLA-DRB1, and secondary effects in the extended MHC cannot be detected. Seven non-HLA loci are associated with RA in black South Africans. Similar to Caucasians, the intergenic region between LOC38920 and RBPJ is associated with RA in this population. The strong association of the R620W variant of the PTPN22 gene with RA in Caucasians was not replicated since this variant was monomorphic in our study, but other SNP variants of the PTPN22 gene were also not associated with RA in black South Africans, suggesting that this locus does not play a major role in RA in this population.

Comparison of the disease activity score using erythrocyte sedimentation rate and C-reactive protein in African Americans with rheumatoid arthritis

OBJECTIVE

The Disease Activity Score based on 28 joints (DAS28) has been increasingly used in clinical practice and research studies of rheumatoid arthritis (RA). Studies have reported discordance between DAS28 based on erythrocyte sedimentation rate (ESR) versus C-reactive protein (CRP) in patients with RA. However, such comparison is lacking in African Americans with RA.

METHODS

This analysis included participants from the Consortium for the Longitudinal Evaluation of African Americans with Early Rheumatoid Arthritis (CLEAR) registry, which enrolls self-declared African Americans with RA. Using tender and swollen joint counts, separate ESR-based and CRP-based DAS28 scores (DAS28-ESR3 and DAS28-CRP3) were calculated, as were DAS28-ESR4 and DAS28-CRP4, which included the patient's assessment of disease activity. The scores were compared using paired t-test, simple agreement and κ, correlation coefficient, and Bland-Altman plots.

RESULTS

Of the 233 included participants, 85% were women, mean age at enrollment was 52.6 years, and median disease duration at enrollment was 21 months. Mean DAS28-ESR3 was significantly higher than DAS28-CRP3 (4.8 vs 3.9; p < 0.001). Similarly, mean DAS28-ESR4 was significantly higher than DAS28-CRP4 (4.7 vs 3.9; p < 0.001). ESR-based DAS28 remained higher than CRP-based DAS28 even when stratified by age, sex, and disease duration. Overall agreement was not high between DAS28-ESR3 and DAS28-CRP3 (50%) or between DAS28-ESR4 and DAS28-CRP4 (59%). DAS28-CRP3 underestimated disease activity in 47% of the participants relative to DAS28-ESR3 and DAS28-CRP4 in 40% of the participants relative to DAS28-ESR4.

CONCLUSION

There was significant discordance between the ESR-based and CRP-based DAS28, a situation that could affect clinical treatment decisions for African Americans with RA.

Clinical response within 12 weeks as a predictor of future low disease activity in patients with early RA: results from the TEAR Trial

OBJECTIVE

Rapidly predicting future outcomes based on short-term clinical response would be helpful to optimize rheumatoid arthritis (RA) management in early disease. Our aim was to derive and validate a clinical prediction rule to predict low disease activity (LDA) at 1 year among patients participating in the Treatment of Early Aggressive Rheumatoid Arthritis (TEAR) trial escalating RA therapy by adding either etanercept or sulfasalazine + hydroxychloroquine [triple therapy (TT)] after 6 months of methotrexate (MTX) therapy.

METHODS

Eligible subjects included in the derivation cohort (used for model building, n = 186) were participants with moderate or higher disease activity [Disease Activity Score 28-erythrocyte sedimentation rate (DAS-ESR) > 3.2] despite 24 weeks of MTX monotherapy who added either etanercept or sulfasalazine + hydroxychloroquine. Clinical characteristics measured within the next 12 weeks were used to predict LDA 1 year later using multivariable logistic regression. Validation was performed in the cohort of TEAR patients randomized to initially receive either MTX + etanercept or TT.

RESULTS

The derivation cohort yielded 3 prediction models of varying complexity that included age, DAS28 at various timepoints, body mass index, and ESR (area under the receiver-operator characteristic curve up to 0.83). Accuracy of the prediction models ranged between 80% and 95% in both derivation and validation cohorts, depending on the complexity of the model and the cutpoints chosen for response and nonresponse. About 80% of patients could be predicted to be responders or nonresponders at Week 12.

CONCLUSION

Clinical data collected early after starting or escalating disease-modifying antirheumatic drug/biologic treatment could accurately predict LDA at 1 year in patients with early RA. For patients predicted to be nonresponders, treatment could be changed at 12 weeks to optimize outcomes.

Association of single-nucleotide polymorphisms in CCR6, TAGAP, and TNFAIP3 with rheumatoid arthritis in African Americans

OBJECTIVE

We previously reported an analysis of single-nucleotide polymorphisms (SNPs) in 3 validated European rheumatoid arthritis (RA) susceptibility loci, TAGAP, TNFAIP3, and CCR6, in African American patients with RA. Unexpectedly, the disease-associated alleles were different in African Americans from those in Europeans. In an effort to better define their contribution, we performed additional SNP genotyping in these genes.

METHODS

Seven SNPs were genotyped in 446 African American patients with RA and in 733 African American control subjects. Differences in minor allele frequency between the RA cases and controls were analyzed after controlling for the global proportion of European admixture, and pairwise linkage disequilibrium (LD) was estimated among the SNPs.

RESULTS

Three SNPs were significantly associated with RA: the TNFAIP3 rs719149 A allele (OR 1.22 [95% confidence interval (95% CI) 1.03-1.44], P = 0.02), the TAGAP rs1738074 G allele (OR 0.75 [95% CI 0.63-0.89, P = 0.0012), and the TAGAP rs4709267 G allele (OR 0.74 [95% CI 0.60-0.91], P = 0.004). Pairwise LD between the TAGAP SNPs was low (r(2) = 0.034). The haplotype containing minor alleles for both TAGAP SNPs was uncommon (4.5%). After conditional analysis of each TAGAP SNP, its counterpart remained significantly associated with RA (rs1738074 for rs4709267 P = 0.00001 and rs4709267 for rs1738074 P = 0.00005), suggesting independent effects.

CONCLUSION

SNPs in regulatory regions of TAGAP and an intronic SNP (TNFAIP3) are potential susceptibility loci in African Americans. Pairwise LD, haplotype analysis, and SNP conditioning analysis suggest that these 2 SNPs in TAGAP are independent susceptibility alleles. Additional fine-mapping of this gene and functional genomic studies of these SNPs should provide further insight into the role of these genes in RA.

Use of a multiethnic approach to identify rheumatoid- arthritis-susceptibility loci, 1p36 and 17q12

We have previously shown that rheumatoid arthritis (RA) risk alleles overlap between different ethnic groups. Here, we utilize a multiethnic approach to show that we can effectively discover RA risk alleles. Thirteen putatively associated SNPs that had not yet exceeded genome-wide significance (p < 5 × 10(-8)) in our previous RA genome-wide association study (GWAS) were analyzed in independent sample sets consisting of 4,366 cases and 17,765 controls of European, African American, and East Asian ancestry. Additionally, we conducted an overall association test across all 65,833 samples (a GWAS meta-analysis plus the replication samples). Of the 13 SNPs investigated, four were significantly below the study-wide Bonferroni corrected p value threshold (p < 0.0038) in the replication samples. Two SNPs (rs3890745 at the 1p36 locus [p = 2.3 × 10(-12)] and rs2872507 at the 17q12 locus [p = 1.7 × 10(-9)]) surpassed genome-wide significance in all 16,659 RA cases and 49,174 controls combined. We used available GWAS data to fine map these two loci in Europeans and East Asians, and we found that the same allele conferred risk in both ethnic groups. A series of bioinformatic analyses identified TNFRSF14-MMEL1 at the 1p36 locus and IKZF3-ORMDL3-GSDMB at the 17q12 locus as the genes most likely associated with RA. These findings demonstrate empirically that a multiethnic approach is an effective strategy for discovering RA risk loci, and they suggest that combining GWASs across ethnic groups represents an efficient strategy for gaining statistical power.

Gene expression patterns in peripheral blood cells associated with radiographic severity in African Americans with early rheumatoid arthritis

Gene expression profiling may be used to stratify patients by disease severity to test the hypothesis that variable disease outcome has a genetic component. In order to define unique expression signatures in African American rheumatoid arthritis (RA) patients with severe erosive disease, we undertook a gene expression study using samples of RNA from peripheral blood mononuclear cells (PBMCs). RNA from baseline PBMC samples of 96 African American RA patients with early RA (<2 years disease duration) was hybridized to cDNA probes of the Illumina Human HT-V3 expression array. Expression analyses were performed using the ca. 25,000 cDNA probes, and then expression levels were compared to the total number of erosions in radiographs of the hands and feet at baseline and 36 months. Using a false discovery rate cutoff of Q = 0.30, 1,138 genes at baseline and 680 genes at 36 months significantly correlated with total erosions. No evidence of a signal differentiating disease progression, or change in erosion scores between baseline and 36 months, was found. Further analyses demonstrated that the differential gene expression signature was localized to the patients with the most erosive disease (>10 erosions). Ingenuity Pathway Analysis demonstrated that genes with fold change greater than 1.5 implicated immune pathways such as CTLA signaling in cytotoxic T lymphocytes. These results demonstrate that CLEAR patients with early RA having the most severe erosive disease, as compared to more mild cases (<10 erosions), may be characterized by a set of differentially expressed genes that represent biological pathways with relevance to autoimmune disease.

Most common single-nucleotide polymorphisms associated with rheumatoid arthritis in persons of European ancestry confer risk of rheumatoid arthritis in African Americans

OBJECTIVE

Large-scale genetic association studies have identified >20 rheumatoid arthritis (RA) risk alleles among individuals of European ancestry. The influence of these risk alleles has not been comprehensively studied in African Americans. We therefore sought to examine whether these validated RA risk alleles are associated with RA risk in an African American population.

METHODS

Twenty-seven candidate single-nucleotide polymorphisms (SNPs) were genotyped in 556 autoantibody-positive African Americans with RA and 791 healthy African American control subjects. Odds ratios (ORs) and 95% confidence intervals (95% CIs) for each SNP were compared with previously published ORs for RA patients of European ancestry. We then calculated a composite genetic risk score (GRS) for each individual based on the sum of all risk alleles.

RESULTS

Overlap of the ORs and 95% CIs between the European and African American populations was observed for 24 of the 27 candidate SNPs. Conversely, 3 of the 27 SNPs (CCR6 rs3093023, TAGAP rs394581, and TNFAIP3 rs6920220) demonstrated ORs in the opposite direction from those reported for RA patients of European ancestry. The GRS analysis indicated a small but highly significant probability that African American patients relative to control subjects were enriched for the risk alleles validated in European RA patients (P = 0.00005).

CONCLUSION

The majority of RA risk alleles previously validated for RA patients of European ancestry showed similar ORs in our population of African Americans with RA. Furthermore, the aggregate GRS supports the hypothesis that these SNPs are risk alleles for RA in the African American population. Future large-scale genetic studies are needed to validate these risk alleles and identify novel RA risk alleles in African Americans.

Associations of cigarette smoking with rheumatoid arthritis in African Americans

OBJECTIVE

To examine the associations of cigarette smoking with rheumatoid arthritis (RA) in African Americans, and to determine whether this association is impacted by the HLA-DRB1 shared epitope (SE).

METHODS

Smoking status, cumulative smoking exposure, and SE status were determined in African American patients with RA and African American healthy controls. Associations of smoking with RA were examined using age- and sex-adjusted logistic regression analyses. Additive and multiplicative SE-smoking interactions were examined.

RESULTS

After adjustment for age and sex, ever smoking (odds ratio [OR] 1.45, 95% confidence interval [95% CI] 1.07, 1.97) and current smoking (OR 1.56, 95% CI 1.07, 2.26), relative to never smoking, were more common in African American patients with RA (n = 605) than in controls (n = 255). The association of smoking with RA was limited to those with a cumulative exposure exceeding 10 pack-years, associations that were evident both in autoantibody-positive and in autoantibody-negative disease. There was evidence of a significant additive interaction between SE status and heavy smoking (≥10 pack-years) in relation to RA risk (attributable proportion [AP] due to interaction 0.58, P = 0.007), with similar results for the additive interaction between SE status and ever smoking (AP 0.47, P = 0.006). There was no evidence of multiplicative interactions.

CONCLUSION

Among African Americans, cigarette smoking is associated not only with the risk of autoantibody-positive RA but also with the risk of autoantibody-negative disease. The risk of RA attributable to smoking is limited to African Americans with more than 10 pack-years of exposure and is more pronounced among individuals positive for the HLA-DRB1 SE.

A Cytoplasmic Regulatory Mutant of Euglena: Constitutivity for the Light-Inducible Chloroplast Transfer RNAs

An ultraviolet-induced cytoplasmic mutant (G(1)BU) of Euglena gracilis Klebs var. bacillaris Pringsheim is described. G(1)BU, in addition to being golden in color and containing smaller amounts of chlorophyll than wild type when grown in the light, is a regulatory constitutive mutant for the light-inducible chloroplast isoleucine and methionine tRNAs; i.e., these two tRNAs are present in dark-grown G(1)BU cells at approximately the levels present in light-grown wild-type cells. Six other mutants were also examined for normal control of plastid tRNA biosynthesis; all four of the aplastidic mutants (lacking appreciable plastid structures and detectable plastid DNA) are incapable of chloroplast tRNA biosynthesis, whereas two other color mutants that do contain plastids and chloroplast DNA have normal plastid tRNA regulation.