Candidate TLR and NLR innate immunity genes and cross shift pulmonary function changes among Western US dairy workers

Abstract

Objectives: Organic dust inhalation has been associated with obstructive and restrictive respiratory disease among dairy workers. Workers are exposed to a wide variety of known agents of respiratory disease including microorganisms and their cellular components which can stimulate innate immune responses through pattern recognition receptors (PRRs) such as Toll‐like (TLR) and NOD‐like (NLR) receptors. The goal of this study was to characterize cross‐shift changes in lung function for various single nucleotide polymorphisms (SNPs) in candidate innate immunity genes in the TLR and NLR pathways. Methods: Breathing‐zone personal work‐shift inhalable dust samples were collected with Button samplers and analyzed for endotoxin (rFCassay), 3‐Hydroxy Fatty Acids, Muramic Acid and Ergosterol (GC‐MSMS). Pulmonary function tests (PFT) before and after the work shift included: forced vital capacity (FVC), Forced Expiratory Volume in 1 second (FEV1), Forced Expiratory Flow (FEF) and the FEV1/FVC ratio. Venous blood samples were collected using Qiagen PAXgene tubes. Following DNA isolation (Puregene), candidate gene SNPs were analyzed using a custom genotyping array (Illumina GoldenGate assay on VeraCode technology) to include tagging SNPs for candidate genes in Hispanic populations. Genotyping data were managed using the Illumina BeadStudio. Additive genetic modeling approaches were used to describe the distribution of SNPs and their relation to PFT cross‐shift changes. Results: Eighty‐eight participants (91% Hispanic, 88% male) had PFT and genetic results. Geometric mean levels of endotoxin were 469 EU/m3. On average, FEV1 was significantly reduced across the work shift among all dairy workers (‐1.6%, 95% CI: ‐2.5, ‐0.7). Cross‐shift PFT changes were observed across SNPs of the TLR4, TLR2, LY96, NOD1, NOD2, interferon gamma (IFNG), and tumor necrosis factor alpha (TNFα) genes. No observable trends were identified for cluster of differentiation 14 (CD14) or TLR 9 genes. Conclusions: This is the first study among Hispanic dairy workers which characterizes candidate gene SNPs associated with the innate immune gene pathways. Crossshift PFT changes across SNPs were not always consistent with previous literature on other populations, including northern Europeans and children; however, evidence suggests that certain genetic pathways may modify the respiratory effects of primarily Hispanic workers exposed to high levels of dust and endotoxin