Integrative approaches for large-scale transcriptome-wide association studies

Many genetic variants influence complex traits by modulating gene expression, thus altering the abundance of one or multiple proteins. Here we introduce a powerful strategy that integrates gene expression measurements with summary association statistics from large-scale genome-wide association studies (GWAS) to identify genes whose cis-regulated expression is associated with complex traits. We leverage expression imputation from genetic data to perform a transcriptome-wide association study (TWAS) to identify significant expression-trait associations. We applied our approaches to expression data from blood and adipose tissue measured in ∼ 3,000 individuals overall. We imputed gene expression into GWAS data from over 900,000 phenotype measurements to identify 69 new genes significantly associated with obesity-related traits (BMI, lipids and height). Many of these genes are associated with relevant phenotypes in the Hybrid Mouse Diversity Panel. Our results showcase the power of integrating genotype, gene expression and phenotype to gain insights into the genetic basis of complex traits.

Activated immune-inflammatory pathways are associated with long-standing depressive symptoms: Evidence from gene-set enrichment analyses in the Young Finns Study

We used genome wide expression (GWE) data of circulating blood cells and pathway analysis to investigate the inflammatory and other molecular pathways that may be associated with long-standing depressive symptoms. Participants were 607 women and 316 men (mean age 42 years) from the Young Finns Study who participated in three consecutive study phases in 2001, 2007 and 2012. Using Gene-set enrichment analyses (GSEA) we focused our analyses to pathways (available in MSigDB database) that are likely to affect immunological and inflammatory processes. GSEA were performed for blood cell GWE data in 2012. Depressive symptoms were assessed using a modified 21-item Beck Depression Inventory in each of the three study phases. Participants who scored in the top quartile of depressive symptoms in each of the three measurement points (n = 191) differed from other participants (n = 732) in several gene-set pathways related to inflammatory processes or immune-inflammatory signaling including interleukin (IL-1) pathway, and pathways related to various immuno-inflammatory processes, such as toll-like, the NEF protein, the nuclear factor kB, the kinase AKT and the mature B cell antigen receptor pathway (false discovery rates, FDRs<0.12). The results provide novel genome wide molecular evidence that support the association between chronic depressive symptoms and altered immune-inflammatory regulation.

Consumption of meat is associated with higher fasting glucose and insulin concentrations regardless of glucose and insulin genetic risk scores: a meta-analysis of 50,345 Caucasians

BACKGROUND

Recent studies suggest that meat intake is associated with diabetes-related phenotypes. However, whether the associations of meat intake and glucose and insulin homeostasis are modified by genes related to glucose and insulin is unknown.

OBJECTIVE

We investigated the associations of meat intake and the interaction of meat with genotype on fasting glucose and insulin concentrations in Caucasians free of diabetes mellitus.

DESIGN

Fourteen studies that are part of the Cohorts for Heart and Aging Research in Genomic Epidemiology consortium participated in the analysis. Data were provided for up to 50,345 participants. Using linear regression within studies and a fixed-effects meta-analysis across studies, we examined 1) the associations of processed meat and unprocessed red meat intake with fasting glucose and insulin concentrations; and 2) the interactions of processed meat and unprocessed red meat with genetic risk score related to fasting glucose or insulin resistance on fasting glucose and insulin concentrations.

RESULTS

Processed meat was associated with higher fasting glucose, and unprocessed red meat was associated with both higher fasting glucose and fasting insulin concentrations after adjustment for potential confounders [not including body mass index (BMI)]. For every additional 50-g serving of processed meat per day, fasting glucose was 0.021 mmol/L (95% CI: 0.011, 0.030 mmol/L) higher. Every additional 100-g serving of unprocessed red meat per day was associated with a 0.037-mmol/L (95% CI: 0.023, 0.051-mmol/L) higher fasting glucose concentration and a 0.049-ln-pmol/L (95% CI: 0.035, 0.063-ln-pmol/L) higher fasting insulin concentration. After additional adjustment for BMI, observed associations were attenuated and no longer statistically significant. The association of processed meat and fasting insulin did not reach statistical significance after correction for multiple comparisons. Observed associations were not modified by genetic loci known to influence fasting glucose or insulin resistance.

CONCLUSION

The association of higher fasting glucose and insulin concentrations with meat consumption was not modified by an index of glucose- and insulin-related single-nucleotide polymorphisms. Six of the participating studies are registered at clinicaltrials.gov as NCT0000513 (Atherosclerosis Risk in Communities), NCT00149435 (Cardiovascular Health Study), NCT00005136 (Family Heart Study), NCT00005121 (Framingham Heart Study), NCT00083369 (Genetics of Lipid Lowering Drugs and Diet Network), and NCT00005487 (Multi-Ethnic Study of Atherosclerosis).

The Biomarker GlycA Is Associated with Chronic Inflammation and Predicts Long-Term Risk of Severe Infection

The biomarker glycoprotein acetylation (GlycA) has been shown to predict risk of cardiovascular disease and all-cause mortality. Here, we characterize biological processes associated with GlycA by leveraging population-based omics data and health records from >10,000 individuals. Our analyses show that GlycA levels are chronic within individuals for up to a decade. In apparently healthy individuals, elevated GlycA corresponded to elevation of myriad inflammatory cytokines, as well as a gene coexpression network indicative of increased neutrophil activity, suggesting that individuals with high GlycA may be in a state of chronic inflammatory response. Accordingly, analysis of infection-related hospitalization and death records showed that increased GlycA increased long-term risk of severe non-localized and respiratory infections, particularly septicaemia and pneumonia. In total, our work demonstrates that GlycA is a biomarker for chronic inflammation, neutrophil activity, and risk of future severe infection. It also illustrates the utility of leveraging multi-layered omics data and health records to elucidate the molecular and cellular processes associated with biomarkers.

Gene-Environment Interactions of Circadian-Related Genes for Cardiometabolic Traits

OBJECTIVE

Common circadian-related gene variants associate with increased risk for metabolic alterations including type 2 diabetes. However, little is known about whether diet and sleep could modify associations between circadian-related variants (CLOCK-rs1801260, CRY2-rs11605924, MTNR1B-rs1387153, MTNR1B-rs10830963, NR1D1-rs2314339) and cardiometabolic traits (fasting glucose [FG], HOMA-insulin resistance, BMI, waist circumference, and HDL-cholesterol) to facilitate personalized recommendations.

RESEARCH DESIGN AND METHODS

We conducted inverse-variance weighted, fixed-effect meta-analyses of results of adjusted associations and interactions between dietary intake/sleep duration and selected variants on cardiometabolic traits from 15 cohort studies including up to 28,190 participants of European descent from the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium.

RESULTS

We observed significant associations between relative macronutrient intakes and glycemic traits and short sleep duration (<7 h) and higher FG and replicated known MTNR1B associations with glycemic traits. No interactions were evident after accounting for multiple comparisons. However, we observed nominally significant interactions (all P < 0.01) between carbohydrate intake and MTNR1B-rs1387153 for FG with a 0.003 mmol/L higher FG with each additional 1% carbohydrate intake in the presence of the T allele, between sleep duration and CRY2-rs11605924 for HDL-cholesterol with a 0.010 mmol/L higher HDL-cholesterol with each additional hour of sleep in the presence of the A allele, and between long sleep duration (≥9 h) and MTNR1B-rs1387153 for BMI with a 0.60 kg/m(2) higher BMI with long sleep duration in the presence of the T allele relative to normal sleep duration (≥7 to <9 h).

CONCLUSIONS

Our results suggest that lower carbohydrate intake and normal sleep duration may ameliorate cardiometabolic abnormalities conferred by common circadian-related genetic variants. Until further mechanistic examination of the nominally significant interactions is conducted, recommendations applicable to the general population regarding diet—specifically higher carbohydrate and lower fat composition—and normal sleep duration should continue to be emphasized among individuals with the investigated circadian-related gene variants.

Kindlin 3 (FERMT3) is associated with unstable atherosclerotic plaques, anti-inflammatory type II macrophages and upregulation of beta-2 integrins in all major arterial beds

BACKGROUND

Kindlins (FERMT) are cytoplasmic proteins required for integrin (ITG) activation, leukocyte transmigration, platelet aggregation and thrombosis. Characterization of kindlins and their association with atherosclerotic plaques in human(s) is lacking.

METHODS AND RESULTS

Exploratory microarray (MA) was first performed followed by selective quantitative validation of robustly expressed genes with qRT-PCR low-density array (LDA). In LDA, ITGA1 (1.30-fold, p = 0.041) and ITGB3 (1.37-fold, p = 0.036) were upregulated in whole blood samples of patients with coronary artery disease (CAD) compared to healthy controls. In arterial plaques, both robustly expressed transcript variants of FERMT3 (MA: 5.90- and 3.4-fold; LDA: 3.99-fold, p < 0.0001 for all) and ITGB2 (MA: 4.81- and 4.92-fold; LDA: 5.29-fold, p < 0.0001 for all) were upregulated while FERMT2 was downregulated (MA: -1.61-fold; LDA: -2.88-fold, p < 0.0001 for both). The other integrins (ITGA1, ITGAV, ITGB3, ITGB5) were downregulated. All these results were replicated in at least one arterial bed. The latter FERMT3 transcript variant associated with unstable plaques (p = 0.0004). FERMT3 correlated with M2 macrophage markers and in hierarchical cluster analysis clustered with inflammatory and macrophage markers, while FERMT2 correlated with SMC-rich plaque markers and clustered with SMC markers. In confocal immunofluorescence analysis, FERMT3 protein colocalized with abundant CD68-positive cells of monocytic origin in the atherosclerotic plaques, while co-localization of FERMT3 with HHF35 indicative of smooth muscle cells was low.

CONCLUSIONS

Kindlin-3 (FERMT3) is upregulated in atherosclerotic, especially unstable plaques, mainly in cells of monocytic origin and of M2 type. Simultaneous upregulation of ITGB2 suggests a synergistic effect on leukocyte adherence and transmigration into the vessel wall.

Meta-analysis of Genome-wide Association Studies for Neuroticism, and the Polygenic Association With Major Depressive Disorder

IMPORTANCE

Neuroticism is a pervasive risk factor for psychiatric conditions. It genetically overlaps with major depressive disorder (MDD) and is therefore an important phenotype for psychiatric genetics. The Genetics of Personality Consortium has created a resource for genome-wide association analyses of personality traits in more than 63,000 participants (including MDD cases).

OBJECTIVES

To identify genetic variants associated with neuroticism by performing a meta-analysis of genome-wide association results based on 1000 Genomes imputation; to evaluate whether common genetic variants as assessed by single-nucleotide polymorphisms (SNPs) explain variation in neuroticism by estimating SNP-based heritability; and to examine whether SNPs that predict neuroticism also predict MDD.

DESIGN, SETTING, AND PARTICIPANTS

Genome-wide association meta-analysis of 30 cohorts with genome-wide genotype, personality, and MDD data from the Genetics of Personality Consortium. The study included 63,661 participants from 29 discovery cohorts and 9786 participants from a replication cohort. Participants came from Europe, the United States, or Australia. Analyses were conducted between 2012 and 2014.

MAIN OUTCOMES AND MEASURES

Neuroticism scores harmonized across all 29 discovery cohorts by item response theory analysis, and clinical MDD case-control status in 2 of the cohorts.

RESULTS

A genome-wide significant SNP was found on 3p14 in MAGI1 (rs35855737; P = 9.26 × 10-9 in the discovery meta-analysis). This association was not replicated (P = .32), but the SNP was still genome-wide significant in the meta-analysis of all 30 cohorts (P = 2.38 × 10-8). Common genetic variants explain 15% of the variance in neuroticism. Polygenic scores based on the meta-analysis of neuroticism in 27 cohorts significantly predicted neuroticism (1.09 × 10-12 < P < .05) and MDD (4.02 × 10-9 < P < .05) in the 2 other cohorts.

CONCLUSIONS AND RELEVANCE

This study identifies a novel locus for neuroticism. The variant is located in a known gene that has been associated with bipolar disorder and schizophrenia in previous studies. In addition, the study shows that neuroticism is influenced by many genetic variants of small effect that are either common or tagged by common variants. These genetic variants also influence MDD. Future studies should confirm the role of the MAGI1 locus for neuroticism and further investigate the association of MAGI1 and the polygenic association to a range of other psychiatric disorders that are phenotypically correlated with neuroticism.

Interleukin-6 and microRNA profiles induced by oral bacteria in human atheroma derived and healthy smooth muscle cells

BACKGROUND

Atherosclerosis is an inflammatory disease with possible contributions from bacterial antigens. We aimed to investigate the role of oral bacteria as inducers of inflammatory cascades in smooth muscle cells from carotid endarterectomy patients (AthSMCs) and healthy controls (HSMCs).

FINDINGS

Inactivated Streptococcus mitis, S. sanguinis, S. gorgonii, Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis were used to stimulate inflammation in HSMCs and AthSMCs. Tumor necrosis factor-α (TNFα) was used as a positive control in all stimulations. Interleukin-6 (IL-6) levels were determined from cell culture supernatants and microRNA expression profiles from cells after 24 h of bacterial stimulation. Genome wide expression (GWE) analyses were performed after 5 h stimulation. All studied bacteria induced pro inflammatory IL-6 production in both SMCs. The most powerful inducer of IL-6 was A. actinomycetemcomitans (p < 0.001). Of the 84 studied miRNAs, expression of 9 miRNAs differed significantly (p ≤ 0.001) between HSMCs and AthSMCs stimulated with inactivated bacteria or TNFα. The data was divided into two groups: high IL-6 producers (A. actinomytectemcomititans and TNFα) and low IL-6 producers (streptococcal strains and P. gingivalis). The expression of 4 miRNAs (miR-181-5p, -186-5p, -28-5p and -155-5p) differed statistically significantly (p < 0.001) between healthy HSMCs and AthSMCs in the low IL-6 producer group. According to multidimensional scaling, two gene expression clusters were seen: one in HSMCs and one AthSMCs.

CONCLUSIONS

Our results suggest that inactivated oral bacteria induce inflammation that is differently regulated in healthy and atherosclerotic SMCs.

A genome-wide expression quantitative trait loci analysis of proprotein convertase subtilisin/kexin enzymes identifies a novel regulatory gene variant for FURIN expression and blood pressure

Proprotein convertase subtilisin/kexin (PCSK) enzymes cleave and convert their immature substrates into biologically active forms. Polymorphisms in the PCSK genes have been reported to associate with human diseases and phenotypes, including hypercholesterolemia and blood pressure (BP), and targeting PCSKs is considered a promising future form of drug therapy. PCSK processing is readily induced upon upregulation of the enzyme, but the genetic factors contributing to PCSK expression have not been thoroughly characterized. To gain a comprehensive understanding of the genetic regulation of PCSK expression, we performed, for the first time, a genome-wide expression quantitative trait loci (eQTL) analysis using mRNA expression in >1400 human peripheral blood samples from the Cardiovascular Risk in Young Finns Study and ca. ten million single-nucleotide polymorphisms (SNPs). The expression data showed clear expression for FURIN, PCSK5, PCSK7 and MBTPS1 (membrane-bound transcription factor peptidase, site 1) mRNAs in virtually all tested samples. A discovery analysis demonstrated a genome-wide significant (p < 5 × 10(-8)) association with the selected PCSK probes for 1024 variants, which were located at ten independent loci. Of these loci, 5/10 could be confirmed to regulate PCSK expression in two additional and independent sample sets. Finally, a phenotypic analysis demonstrated that a novel cis-eQTL SNP rs4702 for FURIN is strongly associated with both diastolic (p = 0.012) and systolic (p = 0.035) BP levels, as well as peripheral vascular resistance (p = 0.003). These findings indicate that the expression of the PCSK enzymes is regulated by genetic factors, which have biological roles in health and disease.

Habitual sleep duration is associated with BMI and macronutrient intake and may be modified by CLOCK genetic variants

BACKGROUND

Short sleep duration has been associated with greater risks of obesity, hypertension, diabetes, and cardiovascular disease. Also, common genetic variants in the human Circadian Locomotor Output Cycles Kaput (CLOCK) show associations with ghrelin and total energy intake.

OBJECTIVES

We examined associations between habitual sleep duration, body mass index (BMI), and macronutrient intake and assessed whether CLOCK variants modify these associations.

DESIGN

We conducted inverse-variance weighted, fixed-effect meta-analyses of results of adjusted associations of sleep duration and BMI and macronutrient intake as percentages of total energy as well as interactions with CLOCK variants from 9 cohort studies including up to 14,906 participants of European descent from the Cohorts for Heart and Aging Research in Genomic Epidemiology Consortium.

RESULTS

We observed a significant association between sleep duration and lower BMI (β ± SE = 0.16 ± 0.04, P < 0.0001) in the overall sample; however, associations between sleep duration and relative macronutrient intake were evident in age- and sex-stratified analyses only. We observed a significant association between sleep duration and lower saturated fatty acid intake in younger (aged 20-64 y) adults (men: 0.11 ± 0.06%, P = 0.03; women: 0.10 ± 0.05%, P = 0.04) and with lower carbohydrate (-0.31 ± 0.12%, P < 0.01), higher total fat (0.18 ± 0.09%, P = 0.05), and higher PUFA (0.05 ± 0.02%, P = 0.02) intakes in older (aged 65-80 y) women. In addition, the following 2 nominally significant interactions were observed: between sleep duration and rs12649507 on PUFA intake and between sleep duration and rs6858749 on protein intake.

CONCLUSIONS

Our results indicate that longer habitual sleep duration is associated with lower BMI and age- and sex-specific favorable dietary behaviors. Differences in the relative intake of specific macronutrients associated with short sleep duration could, at least in part, explain previously reported associations between short sleep duration and chronic metabolic abnormalities. In addition, the influence of obesity-associated CLOCK variants on the association between sleep duration and macronutrient intake suggests that longer habitual sleep duration could ameliorate the genetic predisposition to obesity via a favorable dietary profile.

Blood microRNA profile associates with the levels of serum lipids and metabolites associated with glucose metabolism and insulin resistance and pinpoints pathways underlying metabolic syndrome: the cardiovascular risk in Young Finns Study

Since metabolic syndrome (MetS) is a collection of cardiovascular risk factors involving multiple signaling systems, we related the metabolic abnormalities associated with MetS with circulating microRNA profiles to pinpoint the affected signaling pathways. The blood microRNA profile, genome wide gene expression and serum NMR metabolomics were analyzed from 71 participants of the Young Finns Study. We found nine microRNAs that associated significantly with metabolites connected to MetS. MicroRNA-144-5p concentration correlated with glucose levels, hsa-1207-5p with glycosylated hemoglobin and hsa-miR-484 with metabolites related to insulin resistance. Hsa-miR-625-3p correlated with cholesterol levels, hsa-miR-1237-3p and hsa-miR-331-3p expression with certain fatty acids levels and hsa-miR-129-1-3p, -129-2-3p, and -1288-3p with glycerol levels. The down-regulated targets of miR-1207-5p and -129-2-3p were enriched in PI3K and MAPK pathways and 8 out of the 12 enriched pathways were down-regulated in individuals with MetS. In conclusion microRNAs associated with several aspects of MetS, possibly regulating glucose and lipid metabolism.

Harmonization of Neuroticism and Extraversion phenotypes across inventories and cohorts in the Genetics of Personality Consortium: an application of Item Response Theory

Mega- or meta-analytic studies (e.g. genome-wide association studies) are increasingly used in behavior genetics. An issue in such studies is that phenotypes are often measured by different instruments across study cohorts, requiring harmonization of measures so that more powerful fixed effect meta-analyses can be employed. Within the Genetics of Personality Consortium, we demonstrate for two clinically relevant personality traits, Neuroticism and Extraversion, how Item-Response Theory (IRT) can be applied to map item data from different inventories to the same underlying constructs. Personality item data were analyzed in >160,000 individuals from 23 cohorts across Europe, USA and Australia in which Neuroticism and Extraversion were assessed by nine different personality inventories. Results showed that harmonization was very successful for most personality inventories and moderately successful for some. Neuroticism and Extraversion inventories were largely measurement invariant across cohorts, in particular when comparing cohorts from countries where the same language is spoken. The IRT-based scores for Neuroticism and Extraversion were heritable (48 and 49 %, respectively, based on a meta-analysis of six twin cohorts, total N = 29,496 and 29,501 twin pairs, respectively) with a significant part of the heritability due to non-additive genetic factors. For Extraversion, these genetic factors qualitatively differ across sexes. We showed that our IRT method can lead to a large increase in sample size and therefore statistical power. The IRT approach may be applied to any mega- or meta-analytic study in which item-based behavioral measures need to be harmonized.

High birth weight is associated with obesity and increased carotid wall thickness in young adults: the cardiovascular risk in young Finns study

OBJECTIVE

There is some evidence that people born with high birth weight may be at increased risk of cardiovascular disease in adulthood. Details of the underlying mechanisms remain unknown. We sought to determine whether people born large for gestational age have poor arterial health, increased adiposity, and a poor cardiovascular risk factor profile.

APPROACH AND RESULTS

Carotid intima-media thickness, brachial flow-mediated dilatation, and cardiovascular risk factors were compared between young adults (24-45 years) born at term who were large for gestational age (birth weight >90th percentile; n=171), and a control group with normal birth weight (50-75th percentile; n=525), in the Cardiovascular Risk in Young Finns Study. Those born large for gestational age had higher body mass index throughout childhood, adolescence, and as young adults (26.4 kg/m(2) [SD 4.9], versus normal birth weight 25.1 kg/m(2) [SD 4.6]; P=0.002), and 2-fold greater risk of obesity. Other cardiovascular risk factors and arterial function did not differ; however, carotid intima-media thickness was increased in people born large for gestational age (0.60 mm [SD 0.09], versus normal birth weight 0.57 mm [SD 0.09]; P=0.003), independent of cardiovascular risk factors (P=0.001 after adjustment). Both obesity and high birth weight were independently associated with carotid intima-media thickness in a graded and additive fashion.

CONCLUSIONS

Young adults born large for gestational age are more likely to be obese, yet have an otherwise healthy cardiovascular risk profile. Nonetheless, they have increased carotid intima-media thickness, a marker of subclinical atherosclerosis, consistent with an increased risk of cardiovascular disease.

Association of Neuroimmune Guidance Cue Netrin-1 and Its Chemorepulsive Receptor UNC5B With Atherosclerotic Plaque Expression Signatures and Stability in Human(s)

Background—

Macrophage (MΦ) infiltration and smooth muscle cell (SMC) proliferation are hallmarks of atherosclerosis and unstable plaques. Neuroimmune guidance cue 1 (netrin-1 [NTN1]) plays a critical role controlling MΦ trafficking and SMC activation. Characterization of expression of NTN1 and its receptors and their association with plaque stability in human(s) is lacking.

Methods and Results—

The expression of NTN1 and its receptors did not differ in either whole blood or circulating monocytes from patients with coronary artery disease (n=55) compared with healthy controls (n=45). However, NTN1 was downregulated (−2.9-fold; P <0.0001) and UNC5B upregulated (2.2-fold; P <0.0001) in atherosclerotic plaques (n=68), whereas there were no differences in other NTN1 receptors compared with histologically normal controls (n=28). Increased UNC5B expression is associated with histologically more stable plaques ( P =0.011). NTN1 expression correlated positively with SMC markers and signatures and negatively with inflammatory markers and M1 and especially M2 signatures in the atherosclerotic plaques. UNC5B clustering correlated positively with inflammatory and MΦ markers. NTN1 protein colocalized with CD68-positive cells of monocytic origin and muscle-actin-specific-antibody (HHF3)-positive cells indicative of SMCs in the plaques and only with SMCs in the control samples. NTN1 protein was highly expressed in the intimal layer of the control vessels.

Conclusions—

Present findings provide support for the hypothesis that dysregulation of expression of NTN1 in SMCs and its chemorepulsive receptor UNC5B in macrophages are involved in the development of atherosclerosis and unstable plaques.

Genome-wide association study on dimethylarginines reveals novel AGXT2 variants associated with heart rate variability but not with overall mortality

AIMS

The purpose of this study was to identify novel genetic variants influencing circulating asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) levels and to evaluate whether they have a prognostic value on cardiovascular mortality.

METHODS AND RESULTS

We conducted a genome-wide association study on the methylarginine traits and investigated the predictive value of the new discovered variants on mortality. Our meta-analyses replicated the previously known locus for ADMA levels in DDAH1 (rs997251; P = 1.4 × 10(-40)), identified two non-synomyous polymorphisms for SDMA levels in AGXT2 (rs37369; P = 1.4 × 10(-40) and rs16899974; P = 1.5 × 10(-38)) and one in SLC25A45 (rs34400381; P = 2.5 × 10(-10)). We also fine-mapped the AGXT2 locus for further independent association signals. The two non-synonymous AGXT2 variants independently associated with SDMA levels were also significantly related with short-term heart rate variability (HRV) indices in young adults. The major allele (C) of the novel non-synonymous rs16899974 (V498L) variant associated with decreased SDMA levels and an increase in the ratio between the low- and high-frequency spectral components of HRV (P = 0.00047). Furthermore, the SDMA decreasing allele (G) of the non-synomyous SLC25A45 (R285C) variant was associated with a lower resting mean heart rate during the HRV measurements (P = 0.0046), but not with the HRV indices. None of the studied genome-wide significant variants had any major effect on cardiovascular or total mortality in patients referred for coronary angiography.

CONCLUSIONS

AGXT2 has an important role in SDMA metabolism in humans. AGXT2 may additionally have an unanticipated role in the autonomic nervous system regulation of cardiac function.

Genome-Wide Association Study Identifies 3 Genomic Loci Significantly Associated With Serum Levels of Homoarginine

Background—

Low serum levels of the amino acid derivative, homoarginine, have been associated with increased risk of total and cardiovascular mortality. Homoarginine deficiency may be related to renal and heart diseases, but the pathophysiologic role of homoarginine and the genetic regulation of its serum levels are largely unknown.

Methods and Results—

In 3041 patients of the Ludwigshafen Risk and Cardiovascular Health (LURIC) study referred for coronary angiography and 2102 participants of the Young Finns Study (YFS), we performed a genome-wide association study to identify genomic loci associated with homoarginine serum levels and tested for associations of identified single-nucleotide polymorphisms with mortality in LURIC. We found genome-wide significant associations with homoarginine serum levels on chromosome 2 at the carbamoyl phosphate synthetase I locus, on chromosome 5 at the alanine-glyoxylate aminotransferase 2 locus, and on chromosome 15 at the glycine amidinotransferase locus, as well as a suggestive association on chromosome 6 at the Homo sapiens mediator complex subunit 23 gene/arginase I locus. All loci harbor enzymes located in the mitochondrium are involved in arginine metabolism. The strongest association was observed for rs1153858 at the glycine amidinotransferase locus with a P value of 1.25E-45 in the combined analysis and has been replicated in both the Die Deutsche Diabetes Dialyse Studie (4D study) and the Graz Endocrine Causes of Hypertension (GECOH) study.

Conclusions—

In our genome-wide association study, we identified 3 chromosomal regions significantly associated with serum homoarginine and another region with suggestive association, providing novel insights into the genetic regulation of homoarginine.

Higher maternal body mass index is associated with an increased risk for later type 2 diabetes in offspring

OBJECTIVES

To investigate whether the body mass index (BMI) of a child's mother is associated with an increased future risk of type 2 diabetes, independent of genetic risk or childhood metabolic, behavioral, and environmental factors.

STUDY DESIGN

The analyses were based on the Cardiovascular Risk in Young Finns Study including 1835 individuals aged 3-18 years at baseline with data on maternal BMI, childhood metabolic factors, as well as 34 newly identified type 2 diabetes susceptibility alleles. These subjects were then followed-up over 21-27 years.

RESULTS

Maternal BMI (OR for 1-SD increase 1.54 [95% CI 1.12-2.11], P = .008) and child's systolic blood pressure (1.54 [1.01-2.35], P = .04) were significantly associated with increased odds for later type 2 diabetes, in a multivariable analysis adjusted for age, sex, type 2 diabetes genetic risk score, childhood BMI, insulin, lipids, dietary factors, socioeconomic status, and mother's age, and history of type 2 diabetes. A risk prediction model, which included maternal BMI status outperformed one which utilized only child's BMI data (area under the receiver operating characteristic curve 0.720 vs 0.623, P = .02). The inclusion of genetic risk score and other baseline risk variables did not additionally improve prediction (area under the receiver operating characteristic curve 0.720 vs 0.745, P = .40).

CONCLUSIONS

Maternal BMI is a useful variable in determining offspring risk of developing type 2 diabetes.

Complementary prediction of cardiovascular events by estimated apo- and lipoprotein concentrations in the working age population. The Health 2000 Study

BACKGROUND

Apolipoprotein A-I (apoA-I) and B (apoB) and multiple lipoprotein cardiovascular risk factors can be computationally estimated with our extended Friedewald approach (EFW) from classical inputs. Their impact on cardiovascular events and mortality in the working age population is not known.

METHODS

The working age (≤ 65 years, n = 5956) prospective population-based cohort (follow-up of 7.8 ± 0.9 years; 46,572 patient years, 409 non-fatal incident cardiovascular events, and 55 cardiovascular and 266 all-cause deaths) had their total serum cholesterol (TC), triglycerides (TG), and HDL-C measured. Continuous net reclassification improvement (NRI) was calculated.

RESULTS

In Cox models adjusted with cardiovascular risk factors, EFW-HDL(2)-C (HR 0.78, 95% CI 0.67-0.91; NRI 16.5%), apoA-I (HR 0.78, 95% CI 0.69-0.89; NRI 15.2%), apoB/apoA-I (HR 1.23, 95% CI 1.08-1.40; NRI 20.6%), and VLDL-TG (HR 1.15, 95% CI 1.05-1.25; NRI 20.1%) were associated with incident non-fatal cardiovascular events and improved risk prediction compared with TC, LDL-C, or non-HDL-C. Cardiovascular deaths could be best predicted with EFW apoB (HR 1.81, 95% CI 1.18-2.77; NRI 77.3%).

CONCLUSIONS

EFW approach-derived HDL(2)-C, apoA-I, apoB/apoA-I, and VLDL-TG improve prediction of non-fatal cardiovascular events, and apoB of cardiovascular mortality, and can be utilized for risk estimation in a working age population without extra cost.

Meta-analysis investigating associations between healthy diet and fasting glucose and insulin levels and modification by loci associated with glucose homeostasis in data from 15 cohorts

Whether loci that influence fasting glucose (FG) and fasting insulin (FI) levels, as identified by genome-wide association studies, modify associations of diet with FG or FI is unknown. We utilized data from 15 U.S. and European cohort studies comprising 51,289 persons without diabetes to test whether genotype and diet interact to influence FG or FI concentration. We constructed a diet score using study-specific quartile rankings for intakes of whole grains, fish, fruits, vegetables, and nuts/seeds (favorable) and red/processed meats, sweets, sugared beverages, and fried potatoes (unfavorable). We used linear regression within studies, followed by inverse-variance-weighted meta-analysis, to quantify 1) associations of diet score with FG and FI levels and 2) interactions of diet score with 16 FG-associated loci and 2 FI-associated loci. Diet score (per unit increase) was inversely associated with FG (β = -0.004 mmol/L, 95% confidence interval: -0.005, -0.003) and FI (β = -0.008 ln-pmol/L, 95% confidence interval: -0.009, -0.007) levels after adjustment for demographic factors, lifestyle, and body mass index. Genotype variation at the studied loci did not modify these associations. Healthier diets were associated with lower FG and FI concentrations regardless of genotype at previously replicated FG- and FI-associated loci. Studies focusing on genomic regions that do not yield highly statistically significant associations from main-effect genome-wide association studies may be more fruitful in identifying diet-gene interactions.

Genome-wide association study pinpoints a new functional apolipoprotein B variant influencing oxidized low-density lipoprotein levels but not cardiovascular events: AtheroRemo Consortium

BACKGROUND

Oxidized low-density lipoprotein may be a key factor in the development of atherosclerosis. We performed a genome-wide association study on oxidized low-density lipoprotein and tested the impact of associated single-nucleotide polymorphisms (SNPs) on the risk factors of atherosclerosis and cardiovascular events.

METHODS AND RESULTS

A discovery genome-wide association study was performed on a population of young healthy white individuals (N=2080), and the SNPs associated with a P<5×10(-8) were replicated in 2 independent samples (A: N=2912; B: N=1326). Associations with cardiovascular endpoints were also assessed with 2 additional clinical cohorts (C: N=1118; and D: N=808). We found 328 SNPs associated with oxidized low-density lipoprotein. The genetic variant rs676210 (Pro2739Leu) in apolipoprotein B was the proxy SNP behind all associations (P=4.3×10(-136), effect size=13.2 U/L per allele). This association was replicated in the 2 independent samples (A and B, P=2.5×10(-47) and 1.1×10(-11), effect sizes=10.3 U/L and 7.8 U/L, respectively). In the meta-analyses of cohorts A, C, and D (excluding cohort B without angiographic data), the top SNP did not associate significantly with the age of onset of angiographically verified coronary artery disease (hazard ratio=1.00 [0.94-1.06] per allele), 3-vessel coronary artery disease (hazard ratio=1.03 [0.94-1.13]), or myocardial infarction (hazard ratio=1.04 [0.96-1.12]).

CONCLUSIONS

This novel genetic marker is an important factor regulating oxidized low-density lipoprotein levels but not a major genetic factor for the studied cardiovascular endpoints.

A comparison of the accuracy of Illumina HumanHT-12 v3 Expression BeadChip and TaqMan qRT-PCR gene expression results in patient samples from the Tampere Vascular Study

AIMS

This study was set up to compare the accuracy, sensitivity and specificity of gene expression results between the Illumina HumanHT-12 v3 Expression BeadChip (GWE) and the TaqMan qRT-PCR low-density array (LDA) in atherosclerotic plaques.

METHODS

Gene expression levels of 196 genes were determined from 22 atherosclerotic samples and 6 controls with both the GWE and the LDA.

RESULTS

The accuracies of GWE in comparison to that of qRT-PCR for absolute fold changes (FC) 1.2, 1.6, 2.0 and 3.0 between cases and controls were 73.5%, 79.1%, 72.4% and 60.7%, respectively. The correlation of expression measurements between these methods was good (r = 0.87, y = 0.151 + 0.586x), and the Bland-Altman plot showed that for highly up- or down-regulated transcripts, GWE yields lower absolute FC values than LDA.

CONCLUSION

Gene expression results obtained with the GWE are replicated with high accuracy in LDA, even for technically demanding atherosclerotic samples.

Smooth muscle cells in human atherosclerosis: proteomic profiling reveals differences in expression of Annexin A1 and mitochondrial proteins in carotid disease

Smooth muscle cells (SMC) contribute to the development and stability of atherosclerotic lesions. The molecular mechanisms that mediate their properties are incompletely defined. We employed proteomics and in vitro functional assays to identify the unique characteristics of intimal SMC isolated from human carotid endarterectomy specimens and medial SMC from thoracic aortas and carotids. We verified our findings in the Tampere Vascular Study. Human atheroma-derived SMC exhibit decreased expression of mitochondrial proteins ATP Synthase subunit-beta and Aldehyde dehydrogenase 2, and decreased mitochondrial activity when compared to control SMC. Moreover, a comparison between plaque-derived SMC isolated from patients with or without recent acute cerebrovascular symptoms uncovered an increase in Annexin A1, an endogenous anti-inflammatory protein, in the asymptomatic group. The deletion of Annexin A1 or the blockade of its signaling in SMC resulted in increased cytokine production at baseline and after stimulation with the pro-inflammatory cytokine Tumor Necrosis Factor α. In summary, our proteomics and biochemical analysis revealed mitochondrial damage in human plaque-derived SMC as well as a role of Annexin A1 in reducing the production of pro-inflammatory mediators in SMC.

Tissue inhibitor of matrix metalloproteinases 4 (TIMP4) in a population of young adults: relations to cardiovascular risk markers and carotid artery intima-media thickness. The Cardiovascular Risk in Young Finns Study

OBJECTIVES

The tissue inhibitor of metalloproteinases 4 (TIMP4) is present in significant amounts in human atherosclerotic coronary artery lesions, but its relations with the early pathogenesis of atherosclerotic changes have not been clarified. We studied the associations of circulating TIMP4 with pre-clinical markers of atherosclerosis and traditional cardiovascular risk factors by using longitudinal data on carotid artery intima-media (cIMT) thickness in a population-based cohort of asymptomatic young adult Finns.

METHODS

Data on cIMT, plasma TIMP4, lipids, CRP, blood pressure, BMI, smoking status and daily alcohol intake were obtained from 980 24-39 year-old participants in 2001. The 6-year follow-up in cIMT measurements were performed in 2007 for 769 participants.

RESULTS

Plasma TIMP4 concentrations (mean ± SD) were 2.3 ± 1.7 ng/mL in men and 2.5 ± 1.8 ng/mL in women. Age, LDL-cholesterol, BMI and systolic blood pressure were directly associated with TIMP4 concentration. In a multivariable model, the independent determinants of TIMP4 included systolic blood pressure (p = 0.008) and daily smoking (p = 0.009), both being inversely associated with TIMP4. These two baseline variables explained 1.5% of the variation in TIMP4. TIMP4 was significantly and inversely associated with cIMT measured 6 years later (beta =- 0.0135, p = 0.01) explaining 0.7% of the variability of cIMT.

CONCLUSION

In young apparently healthy adults, circulating TIMP4 concentration was independently and inversely associated with cIMT, a marker of vascular structure and function.

Childhood Physical, Environmental, and Genetic Predictors of Adult Hypertension

Background—

Hypertension is a major modifiable cardiovascular risk factor. The present longitudinal study aimed to examine the best combination of childhood physical and environmental factors to predict adult hypertension and furthermore whether newly identified genetic variants for blood pressure increase the prediction of adult hypertension.

Methods and Results—

The study cohort included 2625 individuals from the Cardiovascular Risk in Young Finns Study who were followed up for 21 to 27 years since baseline (1980; age, 3–18 years). In addition to dietary factors and biomarkers related to blood pressure, we examined whether a genetic risk score based on 29 newly identified single-nucleotide polymorphisms enhances the prediction of adult hypertension. Hypertension in adulthood was defined as systolic blood pressure ≥130 mm Hg and/or diastolic blood pressure ≥85 mm Hg or medication for the condition. Independent childhood risk factors for adult hypertension included the individual's own blood pressure ( P <0.0001), parental hypertension ( P <0.0001), childhood overweight/obesity ( P =0.005), low parental occupational status ( P =0.003), and high genetic risk score ( P <0.0001). Risk assessment based on childhood overweight/obesity status, parental hypertension, and parental occupational status was superior in predicting hypertension compared with the approach using only data on childhood blood pressure levels (C statistics, 0.718 versus 0.733; P =0.0007). Inclusion of both parental hypertension history and data on novel genetic variants for hypertension further improved the C statistics (0.742; P =0.015).

Conclusions—

Prediction of adult hypertension was enhanced by taking into account known physical and environmental childhood risk factors, family history of hypertension, and novel genetic variants. A multifactorial approach may be useful in identifying children at high risk for adult hypertension.

Immunosuppression Adversely Affects TST but Not IGRAs in Patients with Psoriasis or Inflammatory Musculoskeletal Diseases

The performance of the interferon gamma release assays (IGRAs) and tuberculin skin test (TST) was reviewed retrospectively in patients with psoriasis, inflammatory musculoskeletal diseases, or miscellaneous inflammatory conditions. The study was carried out over a 22-month period using 109 records of patients with psoriasis (n = 21), musculoskeletal disease (n = 74), or other inflammatory conditions (n = 14). Forty-four (48%) of 109 patients were on immunosuppressive therapy and 38/109 (35%) on systemic glucocorticoid therapy. The agreement between the IGRAs was substantial (κ = 0.71) whilst that between the IGRAs and TST was low (κ = 0.32). Logistic regression models revealed that IGRAs associated with risk factors for latent tuberculosis infection better than TST. TST was influenced by age, BCG vaccination, sex, and glucocorticoid therapy. We found that IGRAs performed equally well with low level of indeterminate results (1-2%). IGRAs were superior to TST because the latter was influenced by BCG-vaccination status and immunosuppressive therapy.

Genetic variants and blood pressure in a population-based cohort: the Cardiovascular Risk in Young Finns study

Clinical relevance of a genetic predisposition to elevated blood pressure was quantified during the transition from childhood to adulthood in a population-based Finnish cohort (N=2357). Blood pressure was measured at baseline in 1980 (age 3-18 years) and in follow-ups in 1983, 1986, 2001, and 2007. Thirteen single nucleotide polymorphisms associated with blood pressure were genotyped, and 3 genetic risk scores associated with systolic and diastolic blood pressures and their combination were derived for all of the participants. Effects of the genetic risk score were 0.47 mm Hg for systolic and 0.53 mm Hg for diastolic blood pressures (both P<0.01). The combination genetic risk score was associated with diastolic blood pressure from age 9 years onward (β=0.68 mm Hg; P=0.015). Replications in 1194 participants of the Bogalusa Heart Study showed essentially similar results. The participants in the highest quintile of the combination genetic risk score had a 1.82-fold risk of hypertension in adulthood (P<0.0001) compared with the lowest quintile, independent of a family history of premature hypertension. These findings show that genetic variants are associated with preclinical blood pressure traits in childhood; individuals with several susceptibility alleles have, on average, a 0.5-mm Hg higher blood pressure, and this trajectory continues from childhood to adulthood.

Childhood environmental and genetic predictors of adulthood obesity: the cardiovascular risk in young Finns study

CONTEXT

Obesity from childhood to adulthood is associated with adverse health later in life. Increased youth BMI is a risk factor for later obesity, but it is unknown whether identification of other risk factors, including recently discovered genetic markers, would help to identify children at risk of developing adult obesity.

OBJECTIVES

Our objective was to examine the childhood environmental and genetic predictors of adult obesity.

DESIGN, SETTING, AND PARTICIPANTS

We followed 2119 individuals of the Cardiovascular Risk in Young Finns Study for up to 27 yr since baseline (1980, age 3-18 yr).

MAIN OUTCOME MEASURE

We evaluated adult obesity [body mass index (BMI) ≥ 30 kg/m(2)].

RESULTS

The independent predictors (P < 0.05) of adult obesity included childhood BMI, C-reactive protein (CRP), family income (inverse), mother's BMI, and polymorphisms near genes TFAP2B, LRRN6C, and FLJ35579. A risk assessment based on childhood BMI, mother's BMI, and family income was superior in predicting obesity compared with the approach using data only on BMI (C-statistics 0.751 vs. 0.772, P = 0.0015). Inclusion of data on childhood CRP and novel genetic variants for BMI did not incrementally improve C-value (0.779, P = 0.16). A nonlaboratory risk score (childhood BMI, mother's BMI, and family income) predicted adult obesity in all age groups between 3-18 yr (P always <0.001).

CONCLUSIONS

Childhood BMI, CRP, family income (inversely), mother's BMI, and polymorphisms near genes FLJ35779, TFAP2B, and LRRN6C are independently related to adulthood obesity. However, because genetic risk markers and CRP only marginally improve the prediction, our results indicate that children at high risk of adult obesity can be identified using a simple non-laboratory-based risk assessment.

Expression and sequence diversity of the complement regulating outer surface protein E in Borrelia afzelii vs. Borrelia garinii in patients with erythema migrans or neuroborreliosis

Outer surface protein E (OspE) is a complement factor H-binding virulence factor of borrelial subspecies. It is usually absent from in vitro grown Borrelia garinii, although in vivo B. garinii causes neuroborreliosis (NB). We analyzed the presence and sequence spectrum of the ospE genes in vivo in Borrelia spirochetes. DNA samples from the skin, serum and cerebrospinal fluid (CSF) of patients with infections caused by Borrelia afzelii or B. garinii were studied, and anti-OspE antibodies in the corresponding patient sera were detected by IgG ELISA using recombinant OspE as an antigen. ospE genes were found in 20 of 23 erythema migrans (EM) skin biopsies with B. afzelii, in 2 EM skin biopsies with unknown underlying subspecies, in 5 of 9 EM biopsies with B. garinii, and in 1 of 4 CSF samples of NB patients with B. garinii infection. All OspE sequences from B. garinii samples were identical. In contrast, OspE of B. afzelii origin showed more variation. Anti-OspE antibodies were found in 8/21 (38.0%) sera from patients with B. afzelii-associated EM. In conclusion, our results indicate that all borrelial subspecies, but not necessarily all strains, causing human infections can carry ospE genes to protect themselves against complement attack in vivo.

Effector memory T-cells dominate immune responses in tuberculosis treatment: antigen or bacteria persistence?

OBJECTIVE

To compare ex vivo immunological responses upon stimulation of lymphocytes with Mycobacterium tuberculosis-specific antigens in three groups: 1) subjects diagnosed with tuberculosis (TB) in the early 1940s and 1950s but who did not receive anti-tuberculosis chemotherapy (n = 5), 2) subjects treated with anti-tuberculosis agents prior to the rifampicin (RMP) era (n = 26) and 3) subjects who received RMP as a part of modern combination therapy (n = 7).

DESIGN

A total of 38 healthy subjects, mean age 70 +/- 13 years, with a history of previously treated TB were recruited. Peripheral blood mononuclear cells were collected and analysed as a batch by ELISpot. Representative samples with high reactivities were further immunophenotypically characterised.

RESULTS

No differences between the studied groups were detected with regard to the frequencies of reactive lymphocytes. The dominant immunophenotypic profile of the representative responders, irrespective of the treatment schemes, was CD4+CD45RO+CD45RA-CD27-CD28-CCR7-, compatible with the fast reacting effector memory T-cell lineage (T(EM)).

CONCLUSION

Specific T(EM) cells persist even in subjects treated for TB decades ago with modern anti-tuberculosis chemotherapy. Additional studies are needed to address the question of what drives the survival of T(EM) after adequate treatment: persistence of antigens or bacteria.

IGRA tests perform similarly to TST but cause no adverse reactions: pediatric experience in Finland

Background

Two commercial interferon gamma release assays (IGRAs) (QuantiFERON^®-TB Gold in Tube and T SPOT^®-TB) to detect a contact with M. tuberculosis have recently become available. The majority of studies agree that the sensitivity and specificity of these methods are superior to the Tuberculin Skin Tests (TSTs) in detecting an exposure to bacteria in latently infected individuals and in clinical tuberculosis. However, the data in children remains limited.

Findings

Consecutively collected samples from children (n = 99) representing age range from zero to 18 years were analyzed in a retrospective non-blinded study. The two IGRAs were modified and adapted to the needs of Finland, a country of a low tuberculosis incidence. For 27 children, both tests were performed simultaneously and compared with the TST and clinician's diagnosis. The sensitivity, specificity, and accuracy of both IGRAs was determined. QuantiFERON TB Gold and T SPOT-TB performed (respectively) as follows: sensitivities 0.92 (95% confidence interval, CI, 0.67–0.99) and 0.85 (0.64–0.95); specificities 0.91 (0.77–0.97) and 1.00 (0.93–1.00); accuracies 0.91 (0.80–0.97) and 0.96 (0.88–0.99). This compares favorably to the TST whose known figures are 0.90, 0.95, and 0.95, respectively. The agreement between the IGRAs was high, k = 0.89. Finally, both methods agreed well with the TST, k = 0.86 for TST/QuantiFERON-TB Gold and k = 0.76 for TST/T SPOT-TB.

Conclusion

The sensitivity and specificity of IGRA methods compares well with the TST without the inconveniences and complications associated with TST, including exaggerated delayed type hypersensitivity reactions. These properties place them as acceptable substitutes for TST.

Antibody responses to borrelia IR(6) peptide variants and the C6 peptide in Swedish patients with erythema migrans

The aim of this study was to evaluate the antibody responses to different VlsE protein IR(6) peptide variants and the synthetic C6 peptide in acute and convalescent (2-3 and 6 months) serum samples from Swedish patients with clinical erythema migrans (EM). Serum samples were prospectively collected from 148 patients with EM and compared to serum samples obtained from 200 healthy blood donors. The IgG responses to 3 IR(6) peptide variants originating from Borrelia burgdorferi (B. burgdorferi) sensu stricto, B. garinii, and B. afzelii were measured by enzyme-linked immunosorbent assays (ELISAs) and compared to a commercial C6 peptide ELISA. Seropositivity rate in the IR(6) or C6 peptide ELISAs ranged from 32% to 58% at presentation, 30-52% after 2-3 months, and 20-36% after 6 months. At presentation, positive antibodies in any of the 4 ELISAs were found in 66%. In 7/52 (13%), C6-negative EM cases, serological reaction was found to the B. burgdorferi sensu stricto-derived IR(6) peptide. In patients reporting previous LB compared to those without previous LB, significantly higher seropositivity rates were noted for all IR(6) peptides, but not for the C6 peptide. In the serology of EM in Europe, C6 ELISA does not seem to cover all cases. An ELISA using a mixture of B. burgdorferi sensu stricto IR(6) peptide and the C6 peptide could be of value in the serodiagnosis of LB in Europe. Further studies on combinations of variant IR(6) peptides and the C6 peptide in other manifestations of LB are needed to address this issue.

Pilot study of diagnostic potential of the Mycobacterium tuberculosis recombinant HBHA protein in a vaccinated population in Finland

BACKGROUND

In recent years T cell based interferon gamma release assays (IGRA) have been developed for immunodiagnosis of M. tuberculosis infection. At present these assays do not discriminate between disease and latency. Therefore, more promising antigens and diagnostic tools are continuously being searched for tuberculosis immunodiagnostics. The heparin binding hemagglutinin (HBHA) is a surface protein of M. tuberculosis which promotes bacterial aggregation and adhesion to non-phagocytic cells. It has been previously assumed that native, methylated form of this protein would be a promising antigen to discriminate latent from active infection.

METHODOLOGY AND PRINCIPAL FINDINGS

We performed a pilot investigation to study humoral and T-cell mediated immunological responses to recombinant HBHA produced in M. smegmatis or to synthetic peptides in patients with recent or past tuberculosis, with atypical mycobacteriosis, or in healthy vaccinated individuals. The T cell reactivities to HBHA were compared to the respective reactivities towards Purified Protein Derivative (PPD) and two surface secreted proteins, ie. Early Secretory Antigen Target-6 (ESAT-6) and Culture Filtrate Protein-10 (CFP-10). Our pilot results indicate that methylated recombinant HBHA induced a strong T cell mediated immune response and the production of IgG and IgM-class antibodies in all patient groups, most surprisingly in young Finnish vaccinees, as well. We observed a positive correlation between the reactivities to HBHA and non-specific PPD among all studied subjects. As expected, ESAT-6 and CFP-10 were the most powerful antigens to discriminate disease from immunity caused by vaccination.

CONCLUSIONS

On the basis of results of this exploratory investigation we raise concerns that in countries like Finland, where BCG vaccination was routinely used, HBHA utility might not be sufficient for diagnostics because of inability to explicitly discriminate tuberculosis infection from immunoreactivity caused by previous BCG vaccination.

Antibodies to recombinant decorin-binding proteins A and B in the cerebrospinal fluid of patients with Lyme neuroborreliosis

Cerebrospinal fluid (CSF) and serum samples from 34 patients with proven neuroborreliosis (NB) and 22 patients with suspected neuroborreliosis (SNB) from Finland were analysed for antibodies to decorin-binding proteins A (DbpA) and B (DbpB). Antibodies to recombinant protein antigens originating from Borrelia burgdorferi sensu stricto, B. afzelii, or B. garinii species were studied by enzyme-linked immunosorbent assay (ELISA). Of the 34 patients with NB, 100% of the CSF and 88% of the serum samples had IgG antibodies to 1 to 3 variants of DbpA and 79% of the CSF and 70% of the serum samples were positive for 1 to 3 DbpB variants. Antibodies to DbpB seemed to be associated with lymphocytic pleocytosis in the CSF and short duration of the disease, whereas antibodies to DbpA in the CSF were observed irrespective of the duration of the disease and lymphocytic pleocytosis. Among the variant antigens, CSF reactivity was mainly with the DbpB from B. garinii, whereas positivity with the DbpA from B. afzelii or B. garinii predominated. The results suggest that CSF antibodies to DbpB might be useful as a marker of active infection whereas antibodies to DbpA seem to persist a long time after acute phases of NB.

Outer surface protein E antibody response and its effect on complement factor H binding to OspE in Lyme borreliosis

Borrelia burgdorferi sensu stricto and B. afzelii, but not B. garinii, are able to escape complement attack by binding factor H via OspE proteins. Recent finding of ospE genes also in B. garinii isolates has raised the question whether, under in vivo-conditions, B. garinii also expresses OspE proteins and consequently induces an antibody response. We set up an IgG ELISA by using recombinant OspE as an antigen. Sixty percent of acute and 64% of convalescent 25 erythema migrans patient samples were positive for anti-OspE antibodies. Anti-OspE antibodies were also found in the sera (83.6%) and cerebrospinal fluids (36%) of patients with neuroborreliosis. Since B. garinii is the major causative agent of neuroborreliosis, the result suggests that OspE is expressed by B. garinii in vivo. Of the 10 acrodermatitis chronica atrophicans patients, 80% had anti-OspE antibodies. Anti-OspE antibody positive sera inhibited factor H binding to Borrelia more efficiently than normal control sera (65% vs. 33.7%). Our results indicate that Borrelia spirochetes, including B. garinii, can induce the production of anti-OspE antibodies. This implies that OspE protein is produced in vivo by B. garinii possibly enabling it to escape complement and cause a CNS infection.

Duration of antibiotic treatment in disseminated Lyme borreliosis: a double-blind, randomized, placebo-controlled, multicenter clinical study

Despite rather strict recommendations for antibiotic treatment of disseminated Lyme borreliosis (LB), evidence-based studies on the duration of antibiotic treatment are scarce. The aim of this multicenter study was to determine whether initial treatment with intravenous ceftriaxone (CRO) for 3 weeks should be extended with a period of adjunct oral antibiotic therapy. A total of 152 consecutive patients with LB were randomized in a double-blind fashion to receive either amoxicillin (AMOX) 1 g or placebo (PBO) twice daily for 100 days. Both groups received an initial treatment of intravenous CRO 2 g daily for 3 weeks, followed by the randomized drug or PBO. The outcome was evaluated using the visual analogue scale at the follow-up visits. The final analysis included 145 patients, of whom 73 received AMOX and 72 PBO. Diagnoses of LB were categorized as either definite or possible, on the basis of symptoms, signs, and laboratory results. The diagnosis was definite in 52 of the 73 (71.2%) AMOX-treated patients and in 54 of the 72 (75%) PBO patients. Of the patients with definite diagnoses, 62 had neuroborreliosis, 45 arthritis or other musculoskeletal manifestations, and 4 other manifestations of LB. As judged by the visual analogue scale and patient records, the outcome after a 1-year follow-up period was excellent or good in 114 (78.6%) patients, controversial in 14 (9.7%) patients, and poor in 17 (11.7%) patients. In patients with definite LB, the outcome was excellent or good in 49 (92.5%) AMOX-treated patients and 47 (87.0%) PBO patients and poor in 3 (5.7%) AMOX-treated patients and 6 (11.1%) PBO patients (difference nonsignificant, p = 0.49). Twelve months after the end of intravenous antibiotic therapy, the levels of antibodies against Borrelia burgdorferi were markedly decreased in 50% of the patients with definite LB in both groups. The results indicate that oral adjunct antibiotics are not justified in the treatment of patients with disseminated LB who initially receive intravenous CRO for 3 weeks. The clinical outcome cannot be evaluated at the completion of intravenous antibiotic treatment but rather 6-12 months afterwards. In patients with chronic post-treatment symptoms, persistent positive levels of antibodies do not seem to provide any useful information for further care of the patient.

Immune responses to borrelial VlsE IR6 peptide variants

Laboratory confirmation of Lyme borreliosis (LB) relies mainly on the demonstration of anti-borrelial antibodies. In recent studies, a novel VlsE protein IR(6) peptide-based assay has been introduced. Our aim was to evaluate the IR(6) peptides from three Borrelia burgdorferi sensu lato genospecies in the serodiagnosis of European and North American patients. Five VlsE protein IR(6) peptide variants representing sequences from B. burgdorferi sensu stricto, B. garinii, and B. afzelii were used as antigens in both IgG and IgM enzyme-linked immunosorbent assays (ELISA). Serum antibodies of 187 patients at different stages of LB from Europe and the United States were evaluated for serodiagnosis. For comparison samples were tested with one of the commercial IR(6) ELISAs. Three B. afzelii IR(6) variant peptides revealed antibodies that were concordant with each other. B. burgdorferi sensu stricto peptide antibodies mostly paralleled B. afzelii peptide antibodies, and positive values were also obtained in the majority of European sera. For several sera, B. garinii IR(6) peptide antibodies were discordant to B. afzelii peptide antibodies. The commercial IR(6) peptide antibody assay (C6 ELISA) results correlated better with B. burgdorferi sensu stricto IR(6) than with B. garinii IR(6) peptide IgG results, especially in sera from patients with facial palsy. Thus, antibody specificity to IR(6) peptides may vary according to the infecting Borrelia species. In some manifestations of the disease, C6 ELISA may not cover all LB cases. Evidently, the methodological aspects in ELISA design for peptide antibody measurements are important as well as the amino acids sequence of the antigen.

Antigenicity of borrelial protein BBK32 fragments in early Lyme borreliosis

Recombinantly produced borrelial BBK32 protein fragments originating from Borrelia burgdorferi sensu stricto, Borrelia garinii and Borrelia afzelii were evaluated as antigens in the serology of Lyme borreliosis (LB). In ELISA, a mid-portion hydrophilic fragment reacted with LB patient sera. Of the 23 patients with culture- or PCR-positive erythema migrans (EM), 43 % at diagnosis and 52 % at convalescence were positive for at least one Borrelia species-specific variant BBK32 fragment antigen. In parallel ELISAs with BBK32 whole proteins from the three borrelial subspecies as antigens, 17 % at diagnosis and 26 % at convalescence were positive. These results suggest that BBK32 protein fragments may improve the early IgG serology of LB compared to the BBK32 whole protein.

Immunoglobulins and complement factor C4 in adult rhinosinusitis

We assessed whether complement and its factor C4 or abnormal immunoglobulin levels are associated with chronic or recurrent rhinosinusitis. We used multiple patient and control groups to obtain clinically meaningful data. Adult chronic or recurrent rhinosinusitis and acute purulent rhinosinusitis patients were compared with unselected adults and controls without previous rhinosinusitis. Associated clinical factors were reviewed. Levels of immunoglobulins, plasma C3, C4 and classical pathway haemolytic activity were analysed. C4 immunophenotyping was used to detect C4A and C4B deficiencies as null alleles. Complement was up-regulated in rhinosinusitis. C4A nulls and low IgA, IgG, IgG1, IgG2, IgG3 and IgG4 levels were all more common in chronic or recurrent rhinosinusitis patients than in unselected and healthy controls. We searched for relevant differences between the patient groups. According to stepwise logistic regression analysis, nasal polyposis [odds ratio (OR) 10.64, 95% confidence interval (CI) 2.5-45.7, P = 0.001], bronchial asthma (OR 8.87, 95% CI 2.3-34.9, P = 0.002), C4A null alleles (OR 5.84, 95% CI 1.4-24.9, P = 0.017) and low levels of IgG4 together with either IgG1 or IgG2 (OR 15.25, 95% CI 1.4-166.8, P = 0.026) were more common in chronic or recurrent rhinosinusitis than in acute rhinosinusitis patients. Isolated low IgG subclasses had limited value in patient assessment. C4A null alleles are associated with chronic or recurrent rhinosinusitis, potentially through their effect on immune defence and inflammation control. Multiple clinical and immunological parameters may need to be evaluated when searching for prognostic variables.

New antigens for serologic diagnosis of neuroborreliosis in children

OBJECTIVE

To evaluate serology with novel Borrelia-specific protein or peptide antigens in the laboratory diagnosis of neuroborreliosis (NB) in children.

METHODS

The performance of enzyme-linked immunosorbent assays with several recombinant borrelial protein antigens and invariable region 6 synthetic peptide antigen and of a commercial enzyme-linked immunosorbent assay with the flagella antigen were evaluated in the serodiagnosis and follow-up of children with clinical suspicion of NB. Serum samples were obtained from 20 children with neurologic symptoms indicative of NB. The patients were retrospectively divided into 2 groups based on the laboratory tests at presentation indicating definite (n = 7) or probable (n = 13) NB.

RESULTS

In addition to cerebrospinal fluid (CSF) lymphocytic pleocytosis and CSF antiflagella antibodies, all 7 patients with definite NB had serum IgG antibodies to at least 2 of the 3 novel antigens at presentation. The 13 patients with probable NB had variable laboratory findings: CSF pleocytosis (n = 7), CSF antiflagella IgM antibodies (n = 4), serum antiflagella IgM and/or IgG antibodies (n = 10). Of these 13 patients, 7 had serum IgG antibodies to 2 of the 3 novel antigens at presentation. During long term follow-up, serum anti-invariable region 6 antibodies disappeared.

CONCLUSIONS

The present study suggests that assessment of serum antibodies to a panel of Borrelia-specific antigens could improve the laboratory diagnosis of NB at presentation.

IgG subclass response to human parvovirus B19 infection

BACKGROUND

IgG antibodies are essential to immunity against human parvovirus B19 and can neutralize infection both in bone marrow cell cultures infected in vitro and in chronically infected immunosuppressed individuals.

OBJECTIVES

To assess the levels and response kinetics of IgG subclasses towards individual structural proteins of human parvovirus B19.

STUDY DESIGN

Subclasses of IgG for capsid proteins VP1 or VP2 were quantified by EIA using monoclonal antibodies in 30 acutely infected and 30 convalescent patients, as well as in 32 remotely infected and 20 non-infected controls.

RESULTS

In all groups of seropositive individuals the predominant subclass for either structural protein was IgG1. Subclass IgG3 was associated with acute infection. By contrast, IgG4 appeared months after infection, and occurred specifically towards VP1. The ratio of VP1-specific subclasses IgG3 and IgG4 provided a diagnostic test for recent infection with a specificity of 98% and a sensitivity of 97%.

CONCLUSIONS

Comparative measurement of VP1-specific IgG3 and IgG4 is useful in diagnosis. The IgG4 results point to long-term expression of immunologically active VP1 and to T-cell help of T(h)2 type for B-cells recognizing VP1.

Diagnosis of Lyme neuroborreliosis with antibodies to recombinant proteins DbpA, BBK32, and OspC, and VlsE IR6 peptide

Three recombinant antigens, decorin binding protein A (DbpA), BBK32, and outer surface protein C (OspC), and IR(6) peptide of borrelial VlsE protein, were evaluated for the diagnosis of neuroborreliosis (NB), using cerebrospinal fluid (CSF) and serum samples from 89 patients. Their performances in enzyme-linked immunosorbent assay (ELISA) were compared with that of commercial flagella antigen. IgG ELISAs were performed with three variants of each recombinant antigen originating from Borrelia burgdorferi sensu stricto, B. afzelii and B. garinii, and with the IR(6) peptide. IgM antibodies were analysed against OspC and flagella. Of the patients whose CSF contained elevated anti-flagella IgG antibodies, 93% were positive for at least three of the new antigens. Of those with negative or borderline CSF anti-flagella antibodies, 51% were positive for three new antigens. Antibodies to BBK32 were detectable mainly in early disease. Antibodies to DbpA and IR(6) were observed in early and late NB. The use of the new antigens at presentation of the disease improved the laboratory diagnosis of NB. In IgG ELISAs, the diagnostic sensitivity of assays with the new antigens was between 75 and 88%, but was only 52% with the flagella antigen. The discriminatory power between patient and control samples appeared better in the CSF than in the serum. We suggest that assessment of CSF antibodies to at least two antigens, using either flagella and one of the new antigens or two of the new antigens, would improve the current diagnostic yield of NB.

Varicella zoster and Borrelia burgdorferi are the main agents associated with facial paresis, especially in children

BACKGROUND

The etiology of facial paresis (FP) often remains unresolved. Yet, a microbial association is frequently suspected.

OBJECTIVE

To evaluate the infectious etiology of FP by using sensitive tests.

STUDY DESIGN

We studied the serum and cerebrospinal fluid of 42 patients diagnosed with idiopathic peripheral facial paresis using sensitive serological methods and nucleic acid detection and for reference, 42 patients with other neurological disorders (OND) matched for age, sex, season and geographical area.

RESULTS

Varicella zoster virus and Borrelia burgdorferi accounted for 56% of all associated agents in children with FP compared with 11% of OND (P=0.01). In adults, the respective numbers were 29 and 13%. Other treatable etiological agents, Chlamydia pneumoniae and Mycoplasma pneumoniae, accounted for 11% in children and 8% in adults and with the same prevalence between patients with FP and OND.

CONCLUSIONS

Microbes, with specific therapy available accounted for 52% of all associated agents in the patients with FP when compared with 26% in controls with OND (P=0.04). Based on this, we conclude that the patients with FP may benefit from antimicrobial therapy.