Inflammation and Immune-Related Candidate Gene Associations with Acute Lung Injury Susceptibility and Severity: A Validation Study

Introduction: Common variants in genes related to inflammation, innate immunity, epithelial cell function, and angiogenesis have been reported to be associated with risks for Acute Lung Injury (ALI) and related outcomes. We tested whether previously-reported associations can be validated in an independent cohort at risk for ALI. Methods: We identified 37 genetic variants in 27 genes previously associated with ALI and related outcomes. We prepared allelic discrimination assays for 12 SNPs from 11 genes with MAF>0.05 and genotyped these SNPs in Caucasian subjects from a cohort of critically ill patients meeting criteria for the systemic inflammatory response syndrome (SIRS) followed for development of ALI, duration of mechanical ventilation, and in-hospital death. We tested for associations using additive and recessive genetic models. Results: Among Caucasian subjects with SIRS (n = 750), we identified a nominal association between rs2069832 in IL6 and ALI susceptibility (OR$_{adj}$ 1.61; 95% confidence interval [CI], 1.04–2.48, P = 0.03). In a sensitivity analysis limiting ALI cases to those who qualified for the Acute Respiratory Distress Syndrome (ARDS), rs61330082 in NAMPT was nominally associated with risk for ARDS. In terms of ALI outcomes, SNPs in MBL2 (rs1800450) and IL8 (rs4073) were nominally associated with fewer ventilator-free days (VFDs), and SNPs in NFE2L2 (rs6721961) and NAMPT (rs61330082) were nominally associated with 28-day mortality. The directions of effect for these nominal associations were in the same direction as previously reported but none of the associations survived correction for multiple hypothesis testing. Conclusion: Although our primary analyses failed to statistically validate prior associations, our results provide some support for associations between SNPs in IL6 and NAMPT and risk for development of lung injury and for SNPs in IL8, MBL2, NFE2L2 and NAMPT with severity in ALI outcomes. These associations provide further evidence that genetic factors in genes related to immunity and inflammation contribute to ALI pathogenesis

Genetic Variation in the FAS Gene and Associations with Acute Lung Injury

Rationale: Fas (CD95) modulates apoptosis and inflammation and is believed to play an important role in lung injury

A Genome-wide In Vitro Bacterial-Infection Screen Reveals Human Variation in the Host Response Associated with Inflammatory Disease

Recent progress in cataloguing common genetic variation has made possible genome-wide studies that are beginning to elucidate the causes and consequences of our genetic differences. Approaches that provide a mechanistic understanding of how genetic variants function to alter disease susceptibility and why they were substrates of natural selection would complement other approaches to human-genome analysis. Here we use a novel cell-based screen of bacterial infection to identify human variation in Salmonella-induced cell death. A loss-of-function allele of CARD8, a reported inhibitor of the proinflammatory protease caspase-1, was associated with increased cell death in vitro (p = 0.013). The validity of this association was demonstrated through overexpression of alternative alleles and RNA interference in cells of varying genotype. Comparison of mammalian CARD8 orthologs and examination of variation among different human populations suggest that the increase in infectious-disease burden associated with larger animal groups (i.e., herds and colonies), and possibly human population expansion, may have naturally selected for loss of CARD8. We also find that the loss-of-function CARD8 allele shows a modest association with an increased risk of systemic inflammatory response syndrome in a small study (p = 0.05). Therefore, a by-product of the selected benefit of loss of CARD8 could be increased inflammatory diseases. These results demonstrate the utility of genome-wide cell-based association screens with microbes in the identification of naturally selected variants that can impact human health

Genotype frequencies in at-risk controls versus ALI cases.

<p>HWE Hardy-Weinberg equilibrium;</p>a<p>p value for the Fisher's exact test comparing genotypes for at risk controls and ALI cases.</p

Associations with ALI susceptibility.

<p>Multivariate logistic regression adjusted for age, sex, APACHE III score, alcohol abuse, smoking status, and history of chronic renal failure and diabetes mellitus.</p

Flow diagram for Study design.

<p>Subjects with suspected systemic inflammatory response syndrome (SIRS), n = 1327, were enrolled at Harborview Medical Center (HMC), Seattle, WA during the period December 2006–December 2010. In this study, we excluded non-Caucasian subjects, subjects who were found to have previous enrollment or missing data, and subjects that did not meet 3 SIRS criteria present concurrently within a 24 hour period.</p

Genetic variants studied.

*<p>MAF, minor allele frequency in the HapMap;</p>**<p>CEU population; EA, European American; AA, African American; Number refers to number of subjects in group of the referenced study.</p

Associations with moderate or severe ARDS susceptibility.

<p>Multivariate logistic regression adjusted for age, sex, APACHE III score, alcohol abuse, smoking status, and history of chronic renal failure and diabetes mellitus. n = 414 (126 with ARDS).</p

Associations with VFDs.

<p>Multivariate linear regression adjusted for age, sex, APACHE III score, alcohol abuse, smoking status, and history of chronic renal failure and diabetes mellitus. n = 224.</p

HMC SIRS cohort population characteristics.

<p>Data is presented as mean ± SD for continuous variables and n (%) for categorical variables. P values represent results of t test comparison for difference of means for continuous variables and Fisher's exact test for frequency counts for categorical variables. IQR, interquartile range; VFD, ventilator free days; AKI, presence of acute kidney injury by AKIN score >/ = 1 with lowest creatinine during hospitalization used as baseline; Death, subject death within 28 days of admission.</p