Almudena Corrales

Common Variants of TLR1 Associate with Organ Dysfunction and Sustained Pro-Inflammatory Responses during Sepsis

Background Toll-like receptors (TLRs) are critical components for host pathogen recognition and variants in genes participating in this response influence susceptibility to infections. Recently, TLR1 gene polymorphisms have been found correlated with whole blood hyper-inflammatory responses to pathogen-associated molecules and associated with sepsis-associated multiorgan dysfunction and acute lung injury (ALI). We examined the association of common variants of TLR1 gene with sepsis-derived complications in an independent study and with serum levels for four inflammatory biomarkers among septic patients. Methodology/Principal Findings Seven tagging single nucleotide polymorphisms of the TLR1 gene were genotyped in samples from a prospective multicenter case-only study of patients with severe sepsis admitted into a network of intensive care units followed for disease severity. Interleukin (IL)-1β, IL-6, IL-10, and C-reactive protein (CRP) serum levels were measured at study entry, at 48 h and at 7th day. Alleles -7202G and 248Ser, and the 248Ser-602Ile haplotype were associated with circulatory dysfunction among severe septic patients (0.001≤p≤0.022), and with reduced IL-10 (0.012≤p≤0.047) and elevated CRP (0.011≤p≤0.036) serum levels during the first week of sepsis development. Additionally, the -7202GG genotype was found to be associated with hospital mortality (p = 0.017) and ALI (p = 0.050) in a combined analysis with European Americans, suggesting common risk effects among studies. Conclusions/Significance These results partially replicate and extend previous findings, supporting that variants of TLR1 gene are determinants of severe complications during sepsis.

North African Influences and Potential Bias in Case-Control Association Studies in the Spanish Population

Background Despite the limited genetic heterogeneity of Spanish populations, substantial evidences support that historical African influences have not affected them uniformly. Accounting for such population differences might be essential to reduce spurious results in association studies of genetic factors with disease. Using ancestry informative markers (AIMs), we aimed to measure the African influences in Spanish populations and to explore whether these might introduce statistical bias in population-based association studies. Methodology/Principal Findings We genotyped 93 AIMs in Spanish (from the Canary Islands and the Iberian Peninsula) and Northwest Africans, and conducted population and individual-based clustering analyses along with reference data from the HapMap, HGDP-CEPH, and other sources. We found significant differences for the Northwest African influence among Spanish populations from as low as ≈5% in Spanish from the Iberian Peninsula to as much as ≈17% in Canary Islanders, whereas the sub-Saharan African influence was negligible. Strikingly, the Northwest African ancestry showed a wide inter-individual variation in Canary Islanders ranging from 0% to 96%, reflecting the violent way the Islands were conquered and colonized by the Spanish in the XV century. As a consequence, a comparison of allele frequencies between Spanish samples from the Iberian Peninsula and the Canary Islands evidenced an excess of markers with significant differences. However, the inflation of p-values for the differences was adequately controlled by correcting for genetic ancestry estimates derived from a reduced number of AIMs. Conclusions/Significance Although the African influences estimated might be biased due to marker ascertainment, these results confirm that Northwest African genetic footprints are recognizable nowadays in the Spanish populations, particularly in Canary Islanders, and that the uneven African influences existing in these populations might increase the risk for false positives in association studies. Adjusting for population stratification assessed with a few dozen AIMs would be sufficient to control this effect.

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.

Assessing the Validity of Asthma Associations for Eight Candidate Genes and Age at Diagnosis Effects

Background Before the advent of genome-wide association studies (GWAS), ADAM33, ADRB2, CD14, MS4A2 (alias FCER1B), IL13, IL4, IL4R, and TNF constituted the most replicated non-HLA candidate genes with asthma and related traits. However, except for the IL13-IL4 region, none of these genes have been found in close proximity of genome-wide significant hits among GWAS for asthma or related traits. Here we aimed to assess the reproducibility of these asthma associations and to test if associations were more evident considering the effect of age at diagnosis. Methodology/Principal Findings We systematically evaluated 286 common single nucleotide polymorphisms (SNPs) of these 8 genes in a sample of 1,865 unrelated Spanish individuals (606 asthmatics and 1,259 controls). We found that variants at MS4A2, IL4R and ADAM33 genes demonstrated varying association effects with the age at diagnosis of asthma, with 10 SNPs showing study-wise significance after the multiple comparison adjustment. In addition, in silico replication with GWAS data supported the association of IL4R. Conclusions/Significance Our results support the important role of MS4A2, IL4R and ADAM33 genes in asthma and/or atopy susceptibility. However, additional studies in larger samples sets are needed to firmly implicate these genes in asthma susceptibility, and also to identify the causal variation underlying the associations found.

Common variants of NFE2L2 gene predisposes to acute respiratory distress syndrome in patients with severe sepsis

IntroductionThe purpose of this study was to investigate whether common variants across the nuclear factor erythroid 2-like 2 (NFE2L2) gene contribute to the development of the acute respiratory distress syndrome (ARDS) in patients with severe sepsis. NFE2L2 is involved in the response to oxidative stress, and it has been shown to be associated with the development of ARDS in trauma patients.MethodsWe performed a case–control study of 321 patients fulfilling international criteria for severe sepsis and ARDS who were admitted to a Spanish network of post-surgical and critical care units, as well as 871 population-based controls. Six tagging single-nucleotide polymorphisms (SNPs) of NFE2L2 were genotyped, and, after further imputation of additional 34 SNPs, association testing with ARDS susceptibility was conducted using logistic regression analysis.ResultsAfter multiple testing adjustments, our analysis revealed 10 non-coding SNPs in tight linkage disequilibrium (0.75 ≤ r2 ≤ 1) that were associated with ARDS susceptibility as a single association signal. One of those SNPs (rs672961) was previously associated with trauma-induced ARDS and modified the promoter activity of the NFE2L2 gene, showing an odds ratio of 1.93 per T allele (95 % confidence interval, 1.17–3.18; p = 0.0089).ConclusionsOur findings support the involvement of NFE2L2 gene variants in ARDS susceptibility and reinforce further exploration of the role of oxidant stress response as a risk factor for ARDS in critically ill patients.

Correction: Lung Transcriptomics during Protective Ventilatory Support in Sepsis-Induced Acute Lung Injury

The accession number for the complete microarray data set deposited in ArrayExpress appears incorrectly throughout the article as E-MEXP-12345. The correct accession number should be E-MTAB-2673.

No association between genetic ancestry and susceptibility to asthma or atopy in Canary Islanders.

Asthma is a complex respiratory disease characterized by chronic inflammation of airways and frequently associated with atopic symptoms. The population from the Canary Islands, which has resulted from a recent admixture of North African and Iberian populations, shows the highest prevalence of asthma and atopic symptoms among the Spanish populations. Although environmental particularities would account for the majority of such disparity, genetic ancestry might play a role in increasing the susceptibility of asthma or atopy, as have been demonstrated in other recently African-admixed populations. Here, we aimed to explore whether genetic ancestry was associated with asthma or related traits in the Canary Islanders. For that, a total of 734 DNA samples from unrelated individuals of the GOA study, self-reporting at least two generations of ancestors from the Canary Islands (391 asthmatics and 343 controls), were successfully genotyped for 83 ancestry informative markers (AIMs), which allowed to precisely distinguishing between North African and Iberian ancestries. No association was found between genetic ancestry and asthma or related traits after adjusting by demographic variables differing among compared groups. Similarly, none of the individual AIMs was associated with asthma when results were considered in the context of the multiple comparisons performed (0.005 ≤ p value ≤ 0.042; 0.221 ≤ q value ≤ 0.443). Our results suggest that if genetic ancestry were involved in the susceptibility to asthma or related traits among Canary Islanders, its effects would be modest. Larger studies, examining more genetic variants, would be needed to explore such possibility.