Candidate Role for Toll-like Receptor 3 L412F Polymorphism and Infection in Acute Exacerbation of Idiopathic Pulmonary Fibrosis.

The Toll-like receptor 3 Leu412Phe ( L412F) polymorphism attenuates cellular antiviral responses and is associated with accelerated disease progression in idiopathic pulmonary fibrosis (IPF). The role of L412F in bacterial infection in IPF or in acute exacerbations (AE) has not been reported. To characterize the association between L412F and AE-related death in IPF. To determine the effect of L412F on the lung microbiome and on antibacterial TLR responses of primary lung fibroblasts from patients with IPF. TLR-mediated antibacterial and antiviral responses were quantitated in L412F wild-type and 412F-heterozygous primary lung fibroblasts from patients with IPF using ELISA, Western blot analysis, and quantitative PCR. Hierarchical heatmap analysis was employed to establish bacterial and viral clustering in nasopharyngeal lavage samples from patients with AE-IPF. 16S ribosomal RNA quantitative PCR and pyrosequencing were used to determine the effect of L412F on the IPF lung microbiome. A significant increase in AE-related death in patients with 412F-variant IPF was reported. We established that 412F-heterozygous IPF lung fibroblasts have reduced antibacterial TLR responses to LPS (TLR4), Pam3CYSK4 (TLR1/2), flagellin (TLR5), and FSL-1 (TLR6/1) and have reduced responses to live infection. Using 16S ribosomal RNA sequencing, we demonstrated that 412F-heterozygous patients with IPF have a dysregulated lung microbiome with increased frequencies of and . This study reveals that L412F dysregulates the IPF lung microbiome and reduces the responses of IPF lung fibroblasts to bacterial TLR agonists and live bacterial infection. These findings identify a candidate role for L412F in viral- and bacterial-mediated AE death.