Heritability estimates of innate immunity: an extended twin study

Testing the mate-choice hypothesis of the female orgasm: disentangling traits and behaviours

BACKGROUND

The evolution of the female orgasm in humans and its role in romantic relationships is poorly understood. Whereas the male orgasm is inherently linked to reproduction, the female orgasm is not linked to obvious reproductive or survival benefits. It also occurs less consistently during penetrative sex than does the male orgasm. Mate-choice hypotheses posit that the wide variation in female orgasm frequency reflects a discriminatory mechanism designed to select high-quality mates.

OBJECTIVE

We aimed to determine (1) whether women report that their orgasm frequency varies between partners, (2) whether this variation reflects mates' personal characteristics, and (3) whether this variation reflects own and partner sexual behaviour during intercourse.

DESIGN

We collected survey data from 103 women who rated (1) the extent to which their orgasm frequency varied between partners, (2) the characteristics of previous sexual partners who induced high-orgasm frequency and those who induced low-orgasm frequency, and (3) the specific behaviours during sex with those partners. This is the first study to test within-woman variation in orgasm and partner traits.

RESULTS

Overall, women reported variation in their orgasm rates with different partners. Partners who induced high-orgasm rates were rated as more humorous, creative, warm, faithful, and better smelling than partners who induced low-orgasm rates, and also engaged in greater efforts to induce partner orgasm.

CONCLUSIONS

Some assumptions and predictions of mate-choice hypotheses of female orgasm were supported, while other aspects of our findings provide reasons to remain sceptical.

Eco-immunology and bioinvasion: revisiting the evolution of increased competitive ability hypotheses

Immunity is at the core of major theories related to invasion biology. Among them, the evolution of increased competitive ability (EICA) and EICA‐refined hypotheses have been used as a reference work. They postulate that the release from pathogens often experienced during invasion should favour a reallocation of resources from (costly) immune defences to beneficial life‐history traits associated with invasive potential. We review studies documenting immune changes during animal invasions. We describe the designs and approaches that have been applied and discuss some reasons that prevent drawing generalized conclusions regarding EICA hypotheses. We detail why a better assessment of invasion history and immune costs, including immunopathologies and parasite communities, could improve our understanding of the relationships between immunity and invasion success. Finally, we propose new perspectives to revisit the EICA hypotheses. We first emphasize the neutral and adaptive mechanisms involved in immune changes, as well as timing of the later. Such investigation will help decipher whether immune changes are a consequence of pre‐adaptation, or the result of postintroduction adaptations to invasion front conditions. We next bring attention to new avenues of research that remain unexplored, namely age‐dependent immunity and gut microbiota, potential key factors underlying adaptation to invasion front environment and modulating invasion success.

Cytokine production capacity in depression and anxiety

Recent studies have suggested that immune function may be dysregulated in persons with depressive and anxiety disorders. Few studies examined the expression of cytokines in response to ex vivo stimulation of blood by lipopolysaccharide (LPS) to study the innate production capacity of cytokines in depression and anxiety. To investigate this, baseline data from the Netherlands Study of Depression and Anxiety (NESDA) were used, including persons (18-65 years; 66% women) with current (that is, past month; N=591) or remitted (N=354) DSM-IV depressive or anxiety disorders and healthy controls (N=297). Depressive and anxiety symptoms were measured by means of the Inventory of Depressive Symptomatology (IDS) and the Beck Anxiety Inventory (BAI). Using Multi-Analyte Profiling technology, plasma levels of 13 cytokines were assayed after whole blood stimulation by addition of LPS. Basal plasma levels of C-reactive protein, interleukin-6 and tumor necrosis factor-α were also available. A basal and a LPS summary index were created. Results show that LPS-stimulated inflammation was associated with increased odds of current depressive/anxiety disorders (odds ratio (OR)=1.28, P=0.009), as was the case for basal inflammation (OR=1.28, P=0.001). These associations were no longer significant after adjustment for lifestyle and health (OR=1.13, P=0.21; OR=1.07, P=0.45, respectively). After adjustment for lifestyle and health, interleukin-8 was associated with both remitted (OR=1.25, P=0.02) and current (OR=1.28, P=0.005) disorders. In addition, LPS-stimulated inflammation was associated with more severe depressive (β=0.129, P<0.001) and anxiety (β=0.165, P<0.001) symptoms, as was basal inflammation. Unlike basal inflammation, LPS-stimulated inflammation was still associated with (anxiety) symptom severity after adjustment for lifestyle and health (IDS: interleukin (IL)-8, MCP-1, MMP2; BAI: LPS index, IL-6, IL-8, IL-10, IL-18, MCP-1, MMP2, TNF-β). To conclude, lifestyle and health factors may partly explain higher levels of basal, as well as LPS-stimulated inflammation in persons with depressive and anxiety disorders. However, production capacity of several cytokines was positively associated with severity of depressive and in particular anxiety symptoms, even while taking lifestyle and health factors into account. Elevated IL-8 production capacity in both previously and currently depressed and anxious persons might indicate a genetic vulnerability for these disorders.

The Novel ASIC2 Locus is Associated with Severe Gingival Inflammation

An increasing body of evidence suggests a significant genetic regulation of inflammatory response mechanisms; however, little is known regarding the genetic determinants of severe gingival inflammation (GI). We conducted a genome-wide association study of severe GI among 4077 European American adults, participants in the Dental Atherosclerosis Risk In Communities cohort. The severe GI trait was defined dichotomously using the 90^th percentile of gingival index ≥2 extent score. Genotyping was performed with the Affymetrix 6.0 array platform and an imputed set of 2.5 million markers, based on HapMap Phase II CEU build 36, was interrogated. Genetic models were based on logistic regression and controlled for ancestry (10 principal components), sex, age, and examination center. One locus on chromosome 17 met genome-wide statistical significance criteria-lead single nucleotide polymorphism (SNP): rs11652874 [minor allele frequency=0.06, intronic to ASIC2 (acid sensing ionic channel-2, formerly named ACCN1); odds ratio=2.1, 95% confidence interval=1.6-2.7, p=3.9×10^-8]. This association persisted among subjects with severe periodontitis and was robust to adjustment for microbial plaque index. Moreover, the minor [G] allele was associated with higher levels of severe GI in stratified analyses among subsets of participants with high load of either "red" or "orange" complex pathogens, although this association was not statistically significant. While these results will require replication in independent samples and confirmation by mechanistic studies, this locus appears as a promising candidate for severe gingival inflammation. Our findings suggest that genetic variation in ASIC2 is significantly associated with severe gingival inflammation and the association is plaque-independent.

Associations between Single Nucleotide Polymorphisms of High Mobility Group Box 1 Protein and Clinical Outcomes in Korean Sepsis Patients

PURPOSE

High mobility group box 1 (HMGB1) plays a central role in the pathogenesis of sepsis and multiple organ dysfunction syndromes. We investigated the associations of a single nucleotide polymorphism (SNP; rs1045411) in HMGB1 with various clinical parameters, severity, and prognosis in patients with sepsis, severe sepsis, or septic shock.

MATERIALS AND METHODS

We enrolled 212 adult patients followed for 28 days. All patients were genotyped for rs1045411, and the serum levels of HMGB1 and several cytokines were measured.

RESULTS

The proportions of patients according to genotype were GG (71.2%), GA (26.4%), and AA (2.4%). Among patients with chronic lung disease comorbidity, patients with a variant A allele had higher positive blood culture rates and higher levels of various cytokines [interleukin (IL)-1β, IL-6, IL-10, IL-17, and tumor necrosis factor-α] than those with the GG genotype. In the analysis of those with diabetes as a comorbidity, patients with a variant A allele had higher blood culture and Gram-negative culture rates than those with GG genotypes; these patients also had a higher levels of IL-17. In the analysis of those with sepsis caused by a respiratory tract infection, patients with a variant A allele had higher levels of IL-10 and IL-17 (all p<0.05). This polymorphism had no significant impact on patient survival.

CONCLUSION

The variant A allele of rs1045411 appears to be associated with a more severe inflammatory response than the GG genotype under specific conditions.

Genetic and environmental determinants of population variation in interleukin-6, its soluble receptor and C-reactive protein: insights from identical and fraternal twins

Interleukin-6 and C-reactive protein are commonly assessed biomarkers linked to illness, obesity, and stressful life events. However, relatively little is known about their heritability. By comparing Caucasian twins from the Midlife in the US project (MIDUS), we estimated the heritability of IL-6, its soluble receptor, and CRP. Based on the hypothesis that adiposity might contribute more to IL-6 than to sIL-6r, we fit heritability models quantifying the extent to which each reflected genetic and environmental factors shared with obesity. Genetic influences on IL-6 and its receptor proved to be distinct. Further, the appearance of a heritable basis for IL-6 was mediated largely via shared paths with obesity. Supporting this conclusion, we confirmed that when unrelated adult controls are carefully matched to twin participants on BMI, age, gender and socioeconomic indices, their IL-6 is similar to the corresponding twins. In contrast, the effect of BMI on CRP was split between shared genetics and environmental influences. In conclusion, IL-6 is strongly affected by factors associated with obesity accounting for its lability and responsiveness to diet, life style and contemporaneous events.

Associations of cytokine genes with Alzheimer's disease and depression in an elderly Korean population

BACKGROUND

Inflammatory processes regulated by cytokines are important in the aetiology of Alzheimer's disease (AD) and depression. Differences in transcriptional activities associated with several genetic polymorphisms affect cytokine production. We investigated the involvement of alleles associated with higher production of proinflammatory and lower production of anti-inflammatory cytokines in AD and depression in a community-dwelling sample of elderly individuals.

METHOD

A total of 732 community-dwelling elders were clinically evaluated for AD applying the NINCDS-ADRDA criteria and for depression applying the Geriatric Mental State Schedule. Genotyping was performed for six proinflammatory (interleukin (IL)-1β -511C/T and +3953C/T, IL-6 -174G/C, IL-8 -251T/A, tumour necrosis factor (TNF)-α -850C/T) and two anti-inflammatory (IL-4 +33T/C, IL-10 -1082G/A) cytokines. The sums of risk alleles of proinflammatory and anti-inflammatory cytokine genes were estimated. Age, gender, education and apolipoprotein E genotype were considered covariates.

RESULTS

TNF-α -308G/A and IL-8 -251T/A were significantly associated with AD and IL-1β +3953C/T with late-life depression, while the significance of these associations was lost after Bonferroni correction. A greater number of risk alleles producing proinflammatory cytokines was significantly associated with AD, but not with depression, after adjustment for the covariates. No association was found between an increased number of risk alleles for anti-inflammatory cytokine production and either AD or depression.

CONCLUSIONS

The present findings support the inflammatory hypothesis in the aetiology of AD as measured by several cytokine genes associated with increased proinflammatory cytokine production.

LPS-Stimulated Whole Blood Cytokine Production Is Not Related to Disease Behavior in Patients with Quiescent Crohn's Disease

Introduction

Crohn’s disease (CD) is a chronic inflammatory disease in which cytokines play a pivotal role in the induction and maintenance of inflammation. Innate cytokine production is genetically determined and varies largely between individuals; this might impact the severity of inflammation. We aimed to assess whether ex-vivo endotoxin-stimulated levels of cytokines could be associated with disease phenotype.

Methods

Patients with quiescent CD (Harvey-Bradshaw Index ≤ 4 and negative inflammation markers) who were not using immunomodulating drugs or biologicals were eligible. Historical disease characteristics (localization, behavior, number of bowel resections, drug history, extra-intestinal symptoms) were extracted from medical records. We measured cytokine levels (tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and IL-10) in supernatants of lipopolysaccharide (LPS) -stimulated whole blood cultures and correlated these with disease characteristics and age- and sex-matched healthy controls. In addition, we analyzed whether single nucleotide polymorphisms (SNPs) in the promoter region of the TNF-α gene were related to TNF-α levels.

Results

We included 75 patients with CD and 24 healthy controls. Six patients were excluded because of increased inflammation markers resulting in a total of 69 patients. The mean age (SD) of patients with CD was 51.2 (12.3) years with a mean (SD) disease duration of 24.1 (11.5) years. Disease localization, peri-anal involvement and behavior were not related to LPS-stimulated TNF-α, IL-1β, IL-6 or IL-10 levels. In addition, combination of localization with behavior to differentiate mild from severe disease type showed no significant differences. TNF-α levels were higher in patients with CD (428 pg/ml IQR [267-468]) compared to healthy controls (459 pg/ml IQR [364-570], p=0.02). We found no associations between SNPs in the promoter region and TNF-α levels.

Conclusion

In this study, innate cytokine production of TNF-α, IL-1β, IL-6 and IL-10 was not related to historical disease characteristics or disease severity in patients with quiescent CD. These findings suggest that genetically determined levels of these cytokines obtained from LPS-stimulated whole blood cultures are not linked with disease behavior or severity.

Trans-Species Polymorphism in Immune Genes: General Pattern or MHC-Restricted Phenomenon?

Immunity exhibits extraordinarily high levels of variation. Evolution of the immune system in response to host-pathogen interactions in particular ecological contexts appears to be frequently associated with diversifying selection increasing the genetic variability. Many studies have documented that immunologically relevant polymorphism observed today may be tens of millions years old and may predate the emergence of present species. This pattern can be explained by the concept of trans-species polymorphism (TSP) predicting the maintenance and sharing of favourable functionally important alleles of immune-related genes between species due to ongoing balancing selection. Despite the generality of this concept explaining the long-lasting adaptive variation inherited from ancestors, current research in TSP has vastly focused only on major histocompatibility complex (MHC). In this review we summarise the evidence available on TSP in human and animal immune genes to reveal that TSP is not a MHC-specific evolutionary pattern. Further research should clearly pay more attention to the investigation of TSP in innate immune genes and especially pattern recognition receptors which are promising candidates for this type of evolution. More effort should also be made to distinguish TSP from convergent evolution and adaptive introgression. Identification of balanced TSP variants may represent an accurate approach in evolutionary medicine to recognise disease-resistance alleles.

Biomarkers Related to Carotid Intima-Media Thickness and Plaques in Long-Term Survivors of Ischemic Stroke

Lifestyle risk factors, inflammation and genetics play a role in the development of atherosclerosis. We therefore studied Fc gamma receptor (FcγR) polymorphisms, interleukin (IL)-10 polymorphisms and other biomarkers related to carotid intima-media thickness (cIMT) in patients with ischemic stroke at a young age. Patients were evaluated 12 years after stroke occurrence. Patients (n = 232) 49 years of age or younger with an index stroke between 1988 and 1997 were retrospectively selected. Blood samples were taken at a first follow-up 6 years after the stroke. At a second follow-up, additional arterial events were registered for 140 patients, new blood samples were taken, and measurements of cIMT and blood pressure (BP) were performed. Unadjusted logistic regression analysis showed that cIMT ≥1 mm was associated with age, male gender, additional arterial events, BP, cholesterol, sedimentation rate, haemoglobin, triglycerides, creatinine, glycolysed haemoglobin (HbA1c) and FcγRIIIB-NaII/NaII. Adjusted backward stepwise logistic regression showed significance for age (odds ratio (OR) 1.13, 95 % confidence interval (CI) 1.04 to1.23, p = 0.003), male gender (OR 4.07, 95 % CI 1.15 to 14.5, p = 0.030), HbA1c (OR 6.65, 95 % CI 1.21 to 36.5, p = 0.029) and FcγRIIIB-NaII/NaII (OR 3.94, 95 % CI 1.08 to 14.3, p = 0.037). In this long-term follow-up study of patients with ischemic stroke at a young age, FcγRIIIB-NaII/NaII was identified as a possible contributing factor for cIMT ≥1 mm together with known risk factors, such as age, male gender, systolic BP, additional arterial events and HbA1c.

Genetic analysis of leukocyte type-I interferon production and risk of coronary artery disease

OBJECTIVE

Patients with systemic lupus erythematosus are genetically predisposed to enhanced production of the type-I interferon IFN-α and are also at elevated risk of developing atherosclerosis compared with healthy subjects. We aimed to test whether genetic predisposition to increased type-I IFN production affects risk of coronary artery disease.

APPROACH AND RESULTS

Using a list of 11 single nucleotide polymorphisms from the results of genome-wide association studies for systemic lupus erythematosus, which we hypothesised would be enriched in variants that regulate type-I IFN production, we identified a genetic risk score based on 3 single nucleotide polymorphisms (rs10516487, rs3131379 and rs7574865), which correlated significantly with production of IFN-α by human peripheral leukocytes stimulated with CpG-oligonucleotide (n=60, P=1.50 × 10(-5)). These single nucleotide polymorphisms explained 27.8% of variation in the CpG-oligonucleotide-induced IFN-α response and were also associated with Toll-like receptor-7/8- and Toll-like receptor-9-dependent IFN-α and IFN-β responses, but were not associated with inflammatory cytokine production in response to Toll-like receptor-4 stimulation or risk of coronary artery disease in 22,233 cases and 64,762 controls (odds ratio 1.00, 95% CI 0.98-1.02) using Mendelian randomization-based analyses. Coronary artery disease risk was also not associated with the full panel of 11 systemic lupus erythematosus single nucleotide polymorphisms or loci responsible for the monogenic type-I interferonopathies Aicardi-Goutières syndrome and Spondyloenchondrodysplasia with immune dysregulation.

CONCLUSIONS

The results argue against the potential utility of drugs targeting type-I IFN production for coronary artery disease. The use of genetic variants that modify leukocyte signaling pathways, rather than circulating biomarkers, as instruments in Mendelian randomization analyses may be useful for studies investigating causality of other candidate pathways of atherogenesis.

Variation in the human immune system is largely driven by non-heritable influences

There is considerable heterogeneity in immunological parameters between individuals, but its sources are largely unknown. To assess the relative contribution of heritable versus non-heritable factors, we have performed a systems-level analysis of 210 healthy twins between 8 and 82 years of age. We measured 204 different parameters, including cell population frequencies, cytokine responses, and serum proteins, and found that 77% of these are dominated (>50% of variance) and 58% almost completely determined (>80% of variance) by non-heritable influences. In addition, some of these parameters become more variable with age, suggesting the cumulative influence of environmental exposure. Similarly, the serological responses to seasonal influenza vaccination are also determined largely by non-heritable factors, likely due to repeated exposure to different strains. Lastly, in MZ twins discordant for cytomegalovirus infection, more than half of all parameters are affected. These results highlight the largely reactive and adaptive nature of the immune system in healthy individuals.

Duffy antigen receptor genetic variant and the association with Interleukin 8 levels

The aim of this study is to identify loci associated with circulating levels of Interleukin 8 (IL8). We investigated the associations of 121,445 single nucleotide polymorphisms (SNPs) from the Illumina 200K CardioMetabochip with IL8 levels in 1077 controls from the Stockholm Heart Epidemiology Program (SHEEP) study, using linear regression under an additive model of inheritance. Five SNPs (rs12075A/G, rs13179413C/T, rs6907989T/A, rs9352745A/C, rs1779553T/C) reached the pre-defined threshold of genome-wide significance (p<1.0×10(-5)) and were tested for in silico replication in three independent populations, derived from the PIVUS, MDC-CC and SCARF studies. IL8 was measured in serum (SHEEP, PIVUS) and plasma (MDC-CC, SCARF). The strongest association was found with the SNP rs12075 A/G, Asp42Gly (p=1.6×10(-6)), mapping to the Duffy antigen receptor for chemokines (DARC) gene on chromosome 1. The minor allele G was associated with 15.6% and 10.4% reduction in serum IL8 per copy of the allele in SHEEP and PIVUS studies respectively. No association was observed between rs12075 and plasma IL8.

CONCLUSION

rs12075 was associated with serum levels but not with plasma levels of IL8. It is likely that serum IL8 represents the combination of levels of circulating plasma IL8 and additional chemokine liberated from the erythrocyte DARC reservoir due to clotting. These findings highlight the importance of understanding IL8 as a biomarker in cardiometabolic diseases.

Variants of the IL-10 gene associate with muscle strength in elderly from rural Africa: a candidate gene study

Recently, it has been shown that the capacity of the innate immune system to produce cytokines relates to skeletal muscle mass and strength in older persons. The interleukin-10 (IL-10) gene regulates the production capacities of IL-10 and tumour necrosis factor-α (TNF-α). In rural Ghana, IL-10 gene variants associated with different production capacities of IL-10 and TNF-α are enriched compared with Caucasian populations. In this setting, we explored the association between these gene variants and muscle strength. Among 554 Ghanaians aged 50 years and older, we determined 20 single nucleotide polymorphisms in the IL-10 gene, production capacities of IL-10 and TNF-α in whole blood upon stimulation with lipopolysaccharide (LPS) and handgrip strength as a proxy for skeletal muscle strength. We distinguished pro-inflammatory haplotypes associated with low IL-10 production capacity and anti-inflammatory haplotypes with high IL-10 production capacity. We found that distinct haplotypes of the IL-10 gene associated with handgrip strength. A pro-inflammatory haplotype with a population frequency of 43.2% was associated with higher handgrip strength (P = 0.015). An anti-inflammatory haplotype with a population frequency of 7.9% was associated with lower handgrip strength (P = 0.006). In conclusion, variants of the IL-10 gene contributing to a pro-inflammatory cytokine response associate with higher muscle strength, whereas those with anti-inflammatory response associate with lower muscle strength. Future research needs to elucidate whether these effects of variation in the IL-10 gene are exerted directly through its role in the repair of muscle tissue or indirectly through its role in the defence against infectious diseases.

Genetic and environmental influences on the prospective correlation between systemic inflammation and coronary heart disease death in male twins

OBJECTIVE

Because of lack of evidence, we aimed to examine to what degree low-grade systemic inflammation and coronary heart disease (CHD) death shared common genetic and environmental substrates.

APPROACH AND RESULTS

From the 41-year prospective National Heart, Lung, and Blood Institute Twin Study, we included 950 middle-aged male twins at baseline (1969-1973). Low-grade systemic inflammation was measured with plasma levels of interleukin-6 (IL-6) and C-reactive protein. Univariate and bivariate structural equation models were used, adjusted for a risk score for CHD death. The score-adjusted heritability was 19% for IL-6, 27% for C-reactive protein, and 22% for CHD death. The positive phenotypic correlation of IL-6 with CHD death (radjusted=0.27; 95% confidence interval [CI], 0.08-0.43) was driven by additive genetic factors (contribution [relative contribution], 0.30 [111%]) but attenuated by unique environment (-0.03 [-11%]). The genetic correlation between IL-6 and CHD death was 0.74 (95% CI, 0.21-1.00), whereas the unique environmental correlation was -0.05 (95% CI, -0.35 to 0.25). The proportion of genetic variance for CHD death shared with that for IL-6 was 74%. The phenotypic correlation of C-reactive protein with CHD death (radjusted=0.10; 95% CI, -0.02 to 0.22) was explained by additive genetic factors (0.20 [149%]) but was attenuated by the unique environment (-0.09 [-49%]). The genetic correlation of C-reactive protein with CHD death was 0.63 (95% CI, -0.07 to 1.00), whereas the unique environmental correlation was -0.07 (95% CI, -0.29 to 0.17).

CONCLUSIONS

Low-grade systemic inflammation, measured by IL-6, and long-term CHD death share moderate genetic substrates that augment both traits.

Basal inflammation and innate immune response in chronic multisite musculoskeletal pain

Dysregulation of the immune system may play a role in chronic pain, although study findings are inconsistent. This cross-sectional study examined whether basal inflammatory markers and the innate immune response are associated with the presence and severity of chronic multisite musculoskeletal pain. Data were used on 1632 subjects of the Netherlands Study of Depression and Anxiety. The Chronic Pain Grade questionnaire was used to determine the presence and severity of chronic multisite musculoskeletal pain. Subjects were categorized in a chronic multisite musculoskeletal pain group (n=754) and a control group (n=878). Blood levels of the basal inflammatory markers C-reactive protein, interleukin-6, and tumor necrosis factor-alpha were determined. To obtain a measure of the innate immune response, 13 inflammatory markers were assessed after lipopolysaccharide (LPS) stimulation in a subsample (n=707). Subjects with chronic multisite musculoskeletal pain showed elevated levels of basal inflammatory markers compared with controls, but statistical significance was lost after adjustment for lifestyle and disease variables. For some LPS-stimulated inflammatory markers, we did find elevated levels in subjects with chronic multisite musculoskeletal pain both before and after adjustment for covariates. Pain severity was not associated with inflammation within chronic pain subjects. An enhanced innate immune response in chronic multisite musculoskeletal pain may be examined as a potential biomarker for the onset or perpetuation of chronic pain.

Intracellular cytokine production and cognition in healthy older adults

Elevated concentrations of the pro-inflammatory cytokines IL-1β and IL-6 have been associated with impaired cognitive performance. There are, however, few studies that have examined the relationship between cytokine production and specific aspects of cognition in healthy older individuals. Two-colour flow cytometry was used to determine intracellular cytokine production by activated monocytes, and neuropsychological tests were performed using the Cambridge Neuropsychological Test Automated Battery (CANTAB) in 93 apparently healthy men and women aged 55-70 years. A series of hierarchical regression analyses was carried out to examine the contribution of IL-1β and IL-6 (% expression and production (antibody binding capacity (ABC))) to recognition, attention and working memory, after controlling for socio-demographic variables (age, sex and social class). IL-1β% expression and IL-6 production predicted aspects of working memory. Recognition memory was found to be sensitive to the affects of age and social class. The current study suggests that higher intracellular cytokine production by activated monocytes may be predictive of lower cognitive performance in working memory in healthy older individuals. These findings indicate that utilization of models for in vivo cytokine production upon immune challenge may be useful in studying specific aspects of memory affected during inflammatory responses, for example in individuals at risk for cognitive decline owing to age-related inflammatory disorders.

Relationship of serum interleukin-10 and its genetic variations with ischemic stroke in a Chinese general population

BACKGROUND AND PURPOSE

Anti-inflammatory cytokine and its genetic variations may play an important role in the process of atherosclerosis. We assessed whether serum interleukin-10 (IL-10) and its genetic variations are associated with ischemic stroke in a Chinese general population.

METHODS

An epidemiological survey on cardiovascular diseases and their risk factors was carried in a general population in Beijing in 2005. Serum IL-10, IL-6, p-selectin, soluble intercellular adhesion molecule-1 and C-reactive protein were analyzed using ELISA kits, while three IL-10 Single Nucleotide Polymorphisms (SNP) (rs1800872, rs1554286 and rs3021094) were genotyped in 1475 participants.

RESULTS

A high serum IL-10 (top tertile) was significantly associated with ischemic stroke (multivariable adjusted odds ratio (OR) =0.50; 95%CI 0.31-0.81). Rs1800872 (AA vs. AC+CC genotype, OR=1.60; 1.06-2.39), rs1554286(TT vs. CT+CC genotype, OR=1.59; 1.06-2.39), and rs3021094 (CC/CA vs. AA genotype, OR=1.64; 1.04-2.60) were all significantly associated with ischemic stroke even after controlling for age, sex, smoking, systolic blood pressure, total cholesterol, glucose, body mass index and serum IL-10. The SNP score (a summary index of these SNPs) and IL-10 (top tertile) together significantly improved the discriminative power in predicting ischemic stroke by 3.3% (95%CI: 0.2-6.4, p=0.0398) compared to predictions based on conventional risk factors alone.

CONCLUSIONS

The lower serum IL-10 concentration and its selected genetic variations were significantly associated with an increased likelihood of ischemic stroke in this cross-sectional study. Our results suggest that more prospective studies should be conducted to provide stronger evidence justifying the use of IL-10 and its SNPs as new biomarkers to identify a predisposition towards ischemic stroke.

Research review: the role of cytokines in depression in adolescents: a systematic review

BACKGROUND

While cytokines have been implicated in the pathophysiology of depression in adults, the potential role in younger age groups such as adolescents is less clear. This article therefore reviews the literature (a) to explore the relationship between cytokines and depression in adolescents, and (b) to examine how cytokines may be related to adolescent depression in the context of other neurobiological theories of depression.

METHOD

A systematic review of the scientific literature on the subject was conducted in February 2013, searching the Web of Knowledge, PubMed (Medline), PsycInfo and Cochrane electronic databases.

RESULTS

Eighteen studies were identified measuring both depression or depressive symptoms and cytokines or immune markers in adolescents. Adolescents with depression show age-specific characteristics of the immune and inflammatory system, specifically in NK cell activity and in pro-inflammatory cytokines (such as IL-1β and TNF-α). In addition, the role of cytokines in adolescent depression is influenced by neurodevelopment, hormonal changes, stress and trauma.

CONCLUSIONS

There may be differences in the neurobiology of adolescent major depressive disorder (MDD) compared with adult MDD. Increased understanding of the role of cytokines in adolescent MDD may lead to improved outcomes in the treatment of adolescent depression.

Pro-inflammatory capacity of classically activated monocytes relates positively to muscle mass and strength

In mice, monocytes that exhibit a pro-inflammatory profile enter muscle tissue after muscle injury and are crucial for clearance of necrotic tissue and stimulation of muscle progenitor cell proliferation and differentiation. The aim of this study was to test if pro-inflammatory capacity of classically activated (M1) monocytes relates to muscle mass and strength in humans. This study included 191 male and 195 female subjects (mean age 64.2 years (SD 6.4) and 61.9 ± 6.4, respectively) of the Leiden Longevity Study. Pro-inflammatory capacity of M1 monocytes was assessed by ex vivo stimulation of whole blood with Toll-like receptor (TLR) 4 agonist lipopolysaccharide (LPS) and TLR-2/1 agonist tripalmitoyl-S-glycerylcysteine (Pam₃Cys-SK₄), both M1 phenotype activators. Cytokines that stimulate M1 monocyte response (IFN-γ and GM-CSF) as well as cytokines that are secreted by M1 monocytes (IL-6, TNF-α, IL-12, and IL-1β) were measured. Analyses were adjusted for age, height, and body fat mass. Upon stimulation with LPS, the cytokine production capacity of INF-γ, GM-CSF, and TNF-α was significantly positively associated with lean body mass, appendicular lean mass and handgrip strength in men, but not in women. Upon stimulation with Pam₃Cys-SK₄, IL-6; TNF-α; and Il-1β were significantly positively associated with lean body mass and appendicular lean in women, but not in men. Taken together, this study shows that higher pro-inflammatory capacity of M1 monocytes upon stimulation is associated with muscle characteristics and sex dependent.

Identification of a major locus, TNF1, that controls BCG-triggered tumor necrosis factor production by leukocytes in an area hyperendemic for tuberculosis

BACKGROUND

Tumor necrosis factor (TNF) is a key immune regulator of tuberculosis resistance, as exemplified by the highly increased risk of tuberculosis disease among individuals receiving TNF-blocker therapy.

METHODS

We determined the extent of TNF production after stimulation with BCG or BCG plus interferon gamma (IFN-γ) using a whole blood assay in 392 children belonging to 135 nuclear families from an area hyperendemic for tuberculosis in South Africa. We conducted classical univariate and bivariate genome-wide linkage analysis of TNF production using the data from both stimulation protocols by means of an extension of the maximum-likelihood-binomial method for quantitative trait loci to multivariate analysis.

RESULTS

Stimulation of whole blood by either BCG or BCG plus IFN-γ resulted in a range of TNF release across subjects. Extent of TNF production following both stimulation protocols was highly correlated (r = 0.81). We failed to identify genetic linkage of TNF release when considering each stimulus separately. However, using a multivariate approach, we detected a major pleiotropic locus (P < 10(-5)) on chromosome region 11p15, termed TNF locus 1 (TNF1), that controlled TNF production after stimulation by both BCG alone and BCG plus IFN-γ.

CONCLUSIONS

The TNF1 locus was mapped in the vicinity of the TST1 locus, previously identified in the same family sample, that controls tuberculin skin test (TST) negativity per se, that is, T-cell-independent resistance to Mycobacterium tuberculosis infection. This suggested that there is a connection between TST negativity per se and TNF production.

Genome-Wide Association Study of Genetic Variants in LPS-Stimulated IL-6, IL-8, IL-10, IL-1ra and TNF-α Cytokine Response in a Danish Cohort

Background

Cytokine response plays a vital role in various human lipopolysaccharide (LPS) infectious and inflammatory diseases. This study aimed to find genetic variants that might affect the levels of LPS-induced interleukin (IL)-6, IL-8, IL-10, IL-1ra and tumor necrosis factor (TNF)-α cytokine production.

Methods

We performed an initial genome-wide association study using Affymetrix Human Mapping 500 K GeneChip® to screen 130 healthy individuals of Danish descent. The levels of IL-6, IL-8, IL-10, IL-1ra and TNF-α in 24-hour LPS-stimulated whole blood samples were compared within different genotypes. The 152 most significant SNPs were replicated using Illumina Golden Gate® GeneChip in an independent cohort of 186 Danish individuals. Next, 9 of the most statistical significant SNPs were replicated using PCR-based genotyping in an independent cohort of 400 Danish individuals. All results were analyzed in a combined study among the 716 Danish individuals.

Results

Only one marker of the 500 K Gene Chip in the discovery study showed a significant association with LPS-induced IL-1ra cytokine levels after Bonferroni correction (P<10⁻⁷). However, this SNP was not associated with the IL-1ra cytokine levels in the replication dataset. No SNPs reached genome-wide significance for the five cytokine levels in the combined analysis of all three stages.

Conclusions

The associations between the genetic variants and the LPS-induced IL-6, IL-8, IL-10, IL-1ra and TNF-α cytokine levels were not significant in the meta-analysis. This present study does not support a strong genetic effect of LPS-stimulated cytokine production; however, the potential for type II errors should be considered.

A one year longitudinal study of cytokine genes and depression in breast cancer

BACKGROUND

Since inflammatory cytokines have been implicated in the pathophysiology of both cancer and depression, genes that contribute to determining cytokine functional activity are reasonable candidate risk factors for depression related to cancer. This study aimed to investigate whether alleles related to higher pro-inflammatory and/or lower anti-inflammatory cytokine production would associate with depression in a cohort with breast cancer.

METHODS

A total of 309 women with breast cancer were evaluated one week after surgery, and 244 (79%) were followed one year later. Depression (major+minor depressive disorders) was diagnosed according to DSM-IV criteria using the Mini International Neuropsychiatric Interview on both occasions. Six pro-(TNF-α-850C/T and -308G/A, IL-1β-511C/T and +3953C/T, IL-6-174G/C, IL-8-251T/A) and two anti-inflammatory (IL-4 +33T/C, IL-10-1082G/A) cytokine polymorphisms were assayed, and total numbers of potential risk alleles were calculated for pro- and anti-inflammatory cytokine genes. Adjustments were made for demographic and clinical characteristics.

RESULTS

At baseline, 74 (24%) patients were classified with prevalent depression; and at follow-up, 19 (8%) and 25 (10%) patients were classified with persistent and incident depression, respectively. A higher number of pro-inflammatory cytokine risk alleles, and IL-1β-511T/T genotype individually, were independently associated with both prevalent depression at baseline and persistent depression at one year follow-up.

LIMITATIONS

Sample size was relatively small.

CONCLUSIONS

Our findings support the role of pro-inflammatory cytokines in the etiology of depression related to breast cancer, and provide novel evidence of a potential genetic basis for this.

Variation between Populations in the Innate Immune Response to Vaccine Adjuvants

The success of the World Health Organization recommended “Expanded Program of Immunization” (EPI) and similar regional or national programs has been astounding. However, infectious threats currently not covered by these programs continue to infect millions of infants around the world. Furthermore, many infants do not receive existing vaccines either on time or for the required number of doses to provide optimal protection. Nor do all infants around the world develop the same protective immune response to the same vaccine. As a result approximately three million infants die every year from vaccine preventable infections. To tackle these issues, new vaccines need to be developed as well as existing ones made easier to administer. This requires identification of age-optimized vaccine schedules and formulations. In order to be most effective this approach will need to take population-based differences in response to vaccines and adjuvants into account. This review summarizes what is currently known about differences between populations around the world in the innate immune response to existing as well as new and promising vaccine adjuvants.

Behçet's syndrome

Behçet's syndrome (BS) shows a peculiar distribution, with a much higher prevalence in countries along the ancient Silk Road compared with rest of the world. BS also seems to follow a more severe course in ethnic groups with higher prevalence. Diagnosis depends on clinical findings. Criteria sets may not help in patients with less frequent types of involvement. Management strategies should be modified according to the age and sex of the patient and the organs involved. Being a serious health problem in endemic areas, BS also attracts global attention as a model to study inflammatory diseases of unknown cause.

Household endotoxin levels and the risk of non-Hodgkin lymphoma

OBJECTIVE

Endotoxin, a component of the outer membrane of gram-negative bacteria, elicits a strong innate and inflammatory immune response associated with the secretion of proinflammatory cytokines, including tumor necrosis factor-alpha (TNF-α). Because TNF-α polymorphisms that increase TNF-α production are associated with an increased risk of non-Hodgkin lymphoma (NHL), we hypothesized that increased levels of household endotoxin would be associated with an increased NHL risk.

METHODS

We evaluated this association in the National Cancer Institute/Surveillance, Epidemiology and End Results (NCI/SEER) NHL multicenter population-based case-control study. Used vacuum cleaner bags were collected from participants during a home interview. Dust samples from the bags of 594 cases and 442 controls were analyzed for endotoxin [endotoxin unit (EU)/mg of dust] using the kinetic chromogenic Limulus amebocyte lysate assay. Multivariable logistic regression was used to estimate the effect of endotoxin on NHL risk adjusted for age, sex, race, education, study center, and farm exposure.

RESULTS

Endotoxin was not associated with NHL overall [odds ratio (OR) for highest quartile of endotoxin levels = 0.81, 95 % confidence interval (CI) = 0.55, 1.20; p for trend = 0.35] or with diffuse large B-cell lymphoma (OR = 0.63, 95 % CI = 0.34, 1.16; p = 0.31) or follicular lymphoma (OR = 1.07, 95 % CI = 0.61, 1.89; p = 0.73) subtypes. Both working and living on a farm were associated with higher household endotoxin levels compared to never working (p = 0.009) or living (p = 0.01) on a farm. Excluding farmers from the analysis did not change the results.

CONCLUSIONS

We found no evidence of a role for household endotoxin in NHL etiology.

Associations of cytokine gene polymorphisms with post-stroke depression

OBJECTIVES

Inflammatory cytokines are implicated in the pathophysiology of both stroke and depression, and their production is influenced by the transcriptional activity of particular gene polymorphisms. We hypothesised that alleles related to higher pro-inflammatory and/or lower anti-inflammatory cytokine production would be associated with post-stroke depression (PSD).

METHODS

In 276 stroke cases, depression was diagnosed using DSM-IV, and classified into major PSD (N = 29), all (major plus minor) PSD (N = 77), and control (N = 199) groups. Genotyping for six pro-inflammatory polymorphisms (TNF-α -850C/T and -308G/A, IL-1β -511C/T and + 3953C/T, IL-6 -174G/C, and IL-8 -251T/A) and two anti-inflammatory polymorphisms (IL-4 + 33T/C and IL-10 -1082G/A) was conducted. Individual associations with PSD were estimated using logistic regression models. Total numbers of potential risk alleles were calculated for pro-inflammatory and anti-inflammatory cytokine genes and analysed against depression using χ(2)-tests.

RESULTS

The IL-4 + 33C/C genotype was associated with major PSD, and the IL-10 -1082A/A genotype was associated with all PSD. Increasing numbers of risk alleles for these two anti-inflammatory cytokine genotypes were significantly associated with both PSD categories. No significant associations were found with any pro-inflammatory cytokine allele.

CONCLUSIONS

Alleles associated with reduced anti-inflammatory cytokine function were associated with PSD, supporting the cytokine hypothesis in its etiology.

Interleukin-6 promoter variants, prostate cancer risk, and survival

BACKGROUND

Inflammation has been implicated in prostate cancer (PCa) pathogenesis. Promoter DNA variants responsible for differential expression of key cytokines may therefore influence susceptibility to PCa.

METHODS

Two interleukin-6 (IL-6) promoter variants, -174G>C and -6331T>C, were genotyped for association with PCa risk and survival using the Risk Factors for Prostate Cancer Study (RFPCS, 825 cases and 732 controls) and the Melbourne Collaborative Cohort Study (MCCS, 818 cases and 1,745 controls). Impact of genotypes on IL-6 transcriptional activity was measured using Low Density Arrays.

RESULTS

A significant increase in IL-6 transcriptional activity in malignant compared to benign prostate tissue supports a role for IL-6 in PCa. The -174G>C variant showed no association with PCa risk, overall survival, or IL-6 transcriptional activity. The -6331 C-allele was significantly associated with an increased risk in the RFPCS (OR = 1.29, 95% CI = 1.08-1.54), but not in the MCCS. In the MCCS however, cases presenting with a CC genotype conferred a higher risk of mortality (HR = 2.27, 95% CI = 1.34-3.85), which was maintained although reduced overall in the pooled analysis with RFPCS (HR = 1.68, 95% CI = 1.10-2.54). Furthermore, we associate the minor C-allele with a significant decrease in IL-6 transcriptional activity.

CONCLUSIONS

While our study refutes a role for IL-6 -174G>C, it is the first to implicate -6331T>C with PCa risk and poor survival. Our observation that -6331T>C has a significant impact on IL-6 transcriptional activity, calls for further investigations into the role of this variant as a novel PCa biomarker.

Physical health and incident late-life depression: modification by cytokine genes

Inflammatory cytokines have been implicated in the pathophysiology of depression, potentially underlying its association with worse physical health. Cytokine production is influenced by the transcriptional activity of several polymorphisms. We hypothesized that alleles related to higher proinflammatory and/or lower anti-inflammatory cytokine production would strengthen the association between physical disorders and late-life depression. In a 2-year prospective study of a community sample of 521 older people, information on number of physical disorders, diagnosis of depression (Geriatric Mental State), and genotypes for 6 pro-inflammatory (tumor necrosis factor-α -850C/T and -308G/A, interleukin (IL)-1β -511C/T and +3953C/T, IL-6 -174G/C, IL-8 -251T/A) and 2 anti-inflammatory (IL-4 +33T/C, IL-10 -1082G/A) cytokine polymorphisms were ascertained. Total numbers of potential risk alleles were calculated for pro- and anti-inflammatory cytokine genes. Interactions between baseline physical disorders and cytokine genotypes were investigated for incident depression. The associations between physical disorders and incident depression were significant in the presence of 2 alleles related to higher proinflammatory cytokine production (tumor necrosis factor-α -850T and IL-8 -251A), and 1 allele related to lower anti-inflammatory cytokine production (IL-4 +33C). Significant gene-environment interactions, independent of all covariates, were found for total number of risk alleles on both pro- and anti-inflammatory cytokine genes in addition to the above 3 individual single nucleotide polymorphisms. The present findings support cytokine-mediated inflammatory pathways underlying at least some of the well-recognized association between worse physical health and late-life depression, and provide novel evidence of a genetic basis for this.

Additive, non-additive and maternal effects of cytokine transcription in response to immunostimulation with Vibrio vaccine in Chinook salmon (Oncorhynchus tshawytscha)

Estimation of quantitative genetic parameters is important for improving salmonid broodstock management in commercial and government hatcheries. Using a replicated 2 × 2 factorial breeding design (48 families and 192 individuals), we partitioned early immune response transcription variation into additive genetic, non-additive genetic, and maternal components in juvenile Chinook salmon (Oncorhynchus tshawytscha). Transcription of four cytokine genes (IL1, TNF-α, IL-8, IL8-R) and two control genes (IgM and RPS-11) was measured relative to an endogenous control (EF1a) before and 24 h after immune stimulation with Vibrio vaccine. Additive genetic variation was not significant for cytokine transcription and heritability ranged from 0.44 (in pre-challenge IL1) to 0.04 (in post-challenge TNF-α). Non-additive genetic variance was significant in post-challenge IL1 (18 %) and TNF-α (12 %) while maternal effects contributed to pre-challenge cytokine transcription. Cytokine transcription co-expressed within but not between pre- and post-challenge states. The lack of additive genetic effects indicates that cytokine transcription is not a likely candidate for selection programs to improve immune function in Chinook salmon. Our results add to the growing evidence that non-additivity in salmon is common and contributes to our understanding of the genetic architecture of transcription. This indicates that transcription variation may act to maintain genetic variation and facilitate rapid adaptive response in salmonids.

Whether, when and how chronic inflammation increases the risk of developing late-onset Alzheimer's disease

Neuropathological studies have revealed the presence of a broad variety of inflammation-related proteins (complement factors, acute-phase proteins, pro-inflammatory cytokines) in Alzheimer's disease (AD) brains. These constituents of innate immunity are involved in several crucial pathogenic events of the underlying pathological cascade in AD, and recent studies have shown that innate immunity is involved in the etiology of late-onset AD. Genome-wide association studies have demonstrated gene loci that are linked to the complement system. Neuropathological and experimental studies indicate that fibrillar amyloid-β (Aβ) can activate the innate immunity-related CD14 and Toll-like receptor signaling pathways of glial cells for pro-inflammatory cytokine production. The production capacity of this pathway is under genetic control and offspring with a parental history of late-onset AD have a higher production capacity for pro-inflammatory cytokines. The activation of microglia by fibrillar Aβ deposits in the early preclinical stages of AD can make the brain susceptible later on for a second immune challenge leading to enhanced production of pro-inflammatory cytokines. An example of a second immune challenge could be systemic inflammation in patients with preclinical AD. Prospective epidemiological studies show that elevated serum levels of acute phase reactants can be considered as a risk factor for AD. Clinical studies suggest that peripheral inflammation increases the risk of dementia, especially in patients with preexistent cognitive impairment, and accelerates further deterioration in demented patients. The view that peripheral inflammation can increase the risk of dementia in older people provides scope for prevention.

Genome-wide associated loci influencing interleukin (IL)-10, IL-1Ra, and IL-6 levels in African Americans

Interleukins (ILs) are key mediators of the immune response and inflammatory process. Plasma levels of IL-10, IL-1Ra, and IL-6 are associated with metabolic conditions, show large inter-individual variations, and are under strong genetic control. Therefore, elucidation of the genetic variants that influence levels of these ILs provides useful insights into mechanisms of immune response and pathogenesis of diseases. We conducted a genome-wide association study (GWAS) of IL-10, IL-1Ra, and IL-6 levels in 707 non-diabetic African Americans using 5,396,780 imputed and directly genotyped single nucleotide polymorphisms (SNPs) with adjustment for gender, age, and body mass index. IL-10 levels showed genome-wide significant associations (p  < 5 × 10(-8)) with eight SNPs, the most significant of which was rs5743185 in the PMS1 gene (p = 2.30 × 10(-10)). We tested replication of SNPs that showed genome-wide significance in 425 non-diabetic individuals from West Africa, and successfully replicated rs17365948 in the YWHAZ gene (p = 0.02). IL-1Ra levels showed suggestive associations with two SNPs in the ASB3 gene (p = 2.55 × 10(-7)), ten SNPs in the IL-1 gene family (IL1F5, IL1F8, IL1F10, and IL1Ra, p = 1.04 × 10(-6) to 1.75 × 10(-6)), and 23 SNPs near the IL1A gene (p = 1.22 × 10(-6) to 1.63 × 10(-6)). We also successfully replicated rs4251961 (p = 0.009); this SNP was reported to be associated with IL-1Ra levels in a candidate gene study of Europeans. IL-6 levels showed genome-wide significant association with one SNP (RP11-314E23.1; chr6:133397598; p = 8.63 × 10(-9)). To our knowledge, this is the first GWAS on IL-10, IL-1Ra, and IL-6 levels. Follow-up of these findings may provide valuable insight into the pathobiology of IL actions and dysregulations in inflammation and human diseases.

A pilot study of host genetic variants associated with influenza-associated deaths among children and young adults

Low-producing MBL2 genotypes may have increased risk for MRSA co-infection.

We compared the prevalence of 8 polymorphisms in the tumor necrosis factor and mannose-binding lectin genes among 105 children and young adults with fatal influenza with US population estimates and determined in subanalyses whether these polymorphisms were associated with sudden death and bacterial co-infection among persons with fatal influenza. No differences were observed in genotype prevalence or minor allele frequencies between persons with fatal influenza and the reference sample. Fatal cases with low-producing MBL2 genotypes had a 7-fold increased risk for invasive methicillin-resistant Staphylococcus aureus (MRSA) co-infection compared with fatal cases with high- and intermediate-producing MBL2 genotypes (odds ratio 7.1, 95% confidence interval 1.6–32.1). Limited analysis of 2 genes important to the innate immune response found no association between genetic variants and fatal influenza infection. Among children and young adults who died of influenza, low-producing MBL2 genotypes may have increased risk for MRSA co-infection.

Human Cytokine Response to ex vivo Amyloid-β Stimulation is Mediated by Genetic Factors

Through its ability to induce the enhanced release and production of cytokines, amyloid-β is responsible for the chronic inflammatory response that contributes to Alzheimer's disease (AD). Determining whether the response of monocytes to amyloid-β stimulation is under genetic control may help understand the basis of why some people are more prone to develop neuronal degeneration than others. In the current study we investigated the heritability of the cytokine (IL-10, IL-6, IL-1β, IL-1ra, TNF-[.alpha]) production capacity upon ex vivo stimulation with amyloid-β in whole blood samples of 222 twins and 85 singleton siblings from 139 extended twin families. It was found that individual differences in amyloid-β-induced cytokine production capacity are to a large extent of genetic origin, with heritability estimates ranging from 55% (IL-1β) to 68% (IL-6). We conclude that genes influencing amyloid-β-induced cytokine response may provide clues to the progression of AD pathology.

Evidence of genetic susceptibility to infectious mononucleosis: a twin study

Infectious mononucleosis is a clinical manifestation of primary Epstein-Barr virus infection. It is unknown whether genetic factors contribute to risk. To assess heritability, we compared disease concordance in monozygotic to dizygotic twin pairs from the population-based California Twin Program and assessed the risk to initially unaffected co-twins. One member of 611 and both members of 58 twin pairs reported a history of infectious mononucleosis. Pairwise concordance in monozygotic and dizygotic pairs was respectively 12·1% [standard error (s.e.)=1·9%] and 6·1% (s.e.=1·2%). The relative risk (hazard ratio) of monozygotic compared to dizygotic unaffected co-twins of cases was 1·9 [95% confidence interval (CI) 1·1-3·4, P=0·03], over the follow-up period. When the analysis was restricted to same-sex twin pairs, that estimate was 2·5 (95% CI 1·2-5·3, P=0·02). The results are compatible with a heritable contribution to the risk of infectious mononucleosis.

Association of TNFSF8 polymorphisms with peripheral neutrophil count

OBJECTIVE

To investigate the association between 347 single-nucleotide polymorphisms within candidate genes of the tumor necrosis factor, interleukin 1 and interleukin 6 families with neutrophil count.

PATIENTS AND METHODS

Four hundred cases with heart failure after myocardial infarction (MI) were matched by age, sex, and date of incident MI to 694 controls (MI without post-MI heart failure). Both genotypes and neutrophil count at admission for incident MI were available in 314 cases and 515 controls.

RESULTS

We found significant associations between the TNFSF8 poly morphisms rs927374 (P=5.1 x 10(-5)) and rs2295800 (P=1.3 x 10(-4)) and neutrophil count; these single-nucleotide polymorphisms are in high linkage disequilibrium (r(2)=0.97). Associations persisted after controlling for clinical characteristics and were unchanged after adjusting for case-control status. For rs927374, the neutrophil count of GG homozygotes (7.6±5.1) was 16% lower than that of CC homozygotes (9.0±5.2).

CONCLUSION

The TNFSF8 polymorphisms rs927374 and rs2295800 were associated with neutrophil count. This finding suggests that post-MI inflammatory response is genetically modulated.

Local interleukin-10 production during respiratory syncytial virus bronchiolitis is associated with post-bronchiolitis wheeze

Background

Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in infants. Following RSV bronchiolitis, 50% of children develop post-bronchiolitis wheeze (PBW). Animal studies have suggested that interleukin (IL)-10 plays a critical role in the pathogenesis of RSV bronchiolitis and subsequent airway hyperresponsiveness. Previously, we showed that ex vivo monocyte IL-10 production is a predictor of PBW. Additionally, heterozygosity of the single-nucleotide polymorphism (SNP) rs1800872 in the IL10 promoter region was associated with protection against RSV bronchiolitis.

Methods

This study aimed to determine the in vivo role of IL-10 in RSV pathogenesis and recurrent wheeze in a new cohort of 235 infants hospitalized for RSV bronchiolitis. IL-10 levels in nasopharyngeal aspirates (NPAs) were measured at the time of hospitalization and the IL10 SNP rs1800872 genotype was determined. Follow-up data were available for 185 children (79%).

Results

Local IL-10 levels during RSV infection turned out to be higher in infants that later developed physician diagnosed PBW as compared to infants without PBW in the first year after RSV infection (958 vs 692 pg/ml, p = 0.02). The IL10 promoter SNP rs1800872 was not associated with IL-10 concentration in NPAs.

Conclusion

The relationship between high local IL-10 levels during the initial RSV infection and physician diagnosed PBW provides further evidence of the importance of the IL-10 response during RSV bronchiolitis.

The influence of genetic variation on innate immune activation in an environment with high infectious pressure

Interleukin-10 (IL-10) production is under tight genetic control in populations living in affluent environments. However, little is known about the role of IL10 genetics on cytokine production in populations living in environments with high infectious pressure. We have previously reported that, in a rural Ghanaian population, the most common IL10 haplotype associates with a pro-inflammatory response. Here, we aim to replicate these findings in an independent sample of the same population 2 years later. IL-10 and tumour necrosis factor-α (TNF-α) protein concentrations were determined in whole-blood samples ex vivo stimulated with lipopolysaccharide and zymosan in 2006 (n=615) and 2008 (n=647). The association between IL10 single nucleotide polymorphisms and Z-scores of IL-10 and TNF-α levels was analysed in each population subset. The most common IL10 haplotype was associated with a significantly lower IL-10 production and nonsignificantly increased TNF-α levels. The correlation between repeated cytokine assays, based on 111 individuals with measurements in both 2006 and 2008, was r=0.53 (P<0.001) for IL-10 and r=0.36 (P<0.001) for TNF-α. The replication of our previously found effect of variation in the IL10 gene on IL-10 production and the correlation between repeated cytokine stimulation assays provide evidence that IL10 genetics have an important role in regulating the host response under high infectious pressure.

Exploring biologically relevant pathways in frailty

BACKGROUND

Frailty is a late-life syndrome of vulnerability to adverse health outcomes characterized by a phenotype that includes muscle weakness, fatigue, and inflammatory pathway activation. The identification of biologically relevant pathways that influence frailty is challenged by its biological complexity and the necessity in separating disease states from the syndrome of frailty. As with longevity research, genetic analyses may help to provide insights into biologically relevant pathways that contribute to frailty.

METHODS

Based on current understanding of the physiological basis of frailty, we hypothesize that variation in genes related to inflammation and muscle maintenance would associate with frailty. One thousand three hundred and fifty-four single-nucleotide polymorphisms were genotyped across 134 candidate genes using the Illumina Genotyping platform, and the rank order by strength of association between frailty and genotype was determined in a cross-sectional study.

RESULTS

Although no single-nucleotide polymorphism reached study-wide significance after controlling family-wise false-discovery rate at 0.05, single-nucleotide polymorphisms within the 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR), Caspase 8 (CASP8), CREB-binding protein (CREBBP), lysine acetyltransferase 2B (KAT2B), and beta-transducin repeat containing (BTRC) loci were among those strongly associated with frailty.

CONCLUSIONS

The apoptosis- and transcription regulation-related pathways highlighted by this preliminary analysis were consistent with prior gene expression studies in a frail mouse model and provide useful etiological insights for future biological studies of frailty.

Interleukin-1 receptor-associated kinase 3 gene associates with susceptibility to acute lung injury

Sepsis is the most common cause of acute lung injury (ALI), leading to organ dysfunction and death in critically ill patients. Previous studies associated variants of interleukin-1 receptor-associated kinase genes (IRAKs) with differential immune responses to pathogens and with outcomes during sepsis, and revealed that increased expression levels of the IRAK3 gene were correlated with poor outcomes during sepsis. Here we explored whether common variants of the IRAK3 gene were associated with susceptibility to, and outcomes of, severe sepsis. After our discovery of polymorphism, we genotyped a subset of seven single-nucleotide polymorphisms (SNPs) in 336 population-based control subjects and 214 patients with severe sepsis, collected as part of a prospective study of adults from a Spanish network of intensive care units. Whereas IRAK3 SNPs were not associated with susceptibility to severe sepsis, rs10506481 showed a significant association with the development of ALI among patients with sepsis (P = 0.007). The association remained significant after adjusting for multiple comparisons, population stratification, and clinical variables (odds ratio, 2.50; 95% confidence interval, 1.15-5.47; P = 0.021). By imputation, we revealed three additional SNPs independently associated with ALI (P < 0.01). One of these (rs1732887) predicted the disruption of a putative human-mouse conserved transcription factor binding site, and demonstrated functional effects in vitro (P = 0.017). Despite the need for replication in independent studies, our data suggest that common SNPs in the IRAK3 gene may be determinants of sepsis-induced ALI.

A common haplotype of the TNF receptor 2 gene modulates endotoxin tolerance

Endotoxin tolerance is characterized by the suppression of further TNF release upon recurrent exposure to LPS. This phenomenon is proposed to act as a homeostatic mechanism preventing uncontrolled cytokine release such as that observed in bacterial sepsis. The regulatory mechanisms and interindividual variation of endotoxin tolerance induction in man remain poorly characterized. In this paper, we describe a genetic association study of variation in endotoxin tolerance among healthy individuals. We identify a common promoter haplotype in TNFRSF1B (encoding TNFR2) to be strongly associated with reduced tolerance to LPS (p = 5.82 × 10(-6)). This identified haplotype is associated with increased expression of TNFR2 (p = 4.9 × 10(-5)), and we find basal expression of TNFR2, irrespective of genotype and unlike TNFR1, is associated with secondary TNF release (p < 0.0001). Functional studies demonstrate a positive-feedback loop via TNFR2 of LPS-induced TNF release, confirming this previously unrecognized role for TNFR2 in the modulation of LPS response.

Inflammatory gene variants in the Tsimane, an indigenous Bolivian population with a high infectious load

The Tsimane of lowland Bolivia are an indigenous forager-farmer population living under conditions resembling pre-industrial European populations, with high infectious morbidity, high infection and inflammation, and shortened life expectancy. Analysis of 917 persons ages 5 to 60+ showed that allele frequencies of 9 SNPs examined in the apolipoprotein E (apoE), C-reactive protein (CRP), and interleukin-6 (IL-6) genes differed from some European, African, and north Asian-derived populations. The apoE2 allele was absent, whereas four SNPs related to CRP and IL-6 were monomorphic: CRP (rs1800947, rs3093061, and rs3093062) and IL-6 (rs1800795). No significant differences in apoE, CRP, and IL-6 variants across age were found CRP levels were higher in carriers of two CRP proinflammatory SNPs, whereas they were lower in carriers of apoE4. Taken together the evidence for (1) different allele frequencies between the Tsimane and other populations and (2) the correlations of CRP and apoE alleles with blood CRP may suggest that these variants are under selection in response to a high infection environment.