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

Rationale: The Toll-like receptor 3 Leu412Phe (TLR3 L412F) polymorphism attenuates cellular antiviral responses and is associated with accelerated disease progression in idiopathic pulmonary fibrosis (IPF). The role of TLR3 L412F in bacterial infection in IPF or in acute exacerbations (AE) has not been reported. Objectives: To characterize the association between TLR3 L412F and AE-related death in IPF. To determine the effect of TLR3 L412F on the lung microbiome and on antibacterial TLR responses of primary lung fibroblasts from patients with IPF. Methods: 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 TLR3 L412F on the IPF lung microbiome. Measurements and Main Results: 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 Pseudomonas aeruginosa infection. Using 16S ribosomal RNA sequencing, we demonstrated that 412F-heterozygous patients with IPF have a dysregulated lung microbiome with increased frequencies of Streptococcus and Staphylococcus spp. Conclusions: This study reveals that TLR3 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 TLR3 L412F in viral- and bacterial-mediated AE death.

The polymorphism L412F in TLR3 inhibits autophagy and is a marker of severe COVID-19 in males.

The polymorphism L412F in TLR3 has been associated with several infectious diseases. However, the mechanism underlying this association is still unexplored. Here, we show that the L412F polymorphism in TLR3 is a marker of severity in COVID-19. This association increases in the sub-cohort of males. Impaired macroautophagy/autophagy and reduced TNF/TNFα production was demonstrated in HEK293 cells transfected with TLR3L412F-encoding plasmid and stimulated with specific agonist poly(I:C). A statistically significant reduced survival at 28 days was shown in L412F COVID-19 patients treated with the autophagy-inhibitor hydroxychloroquine (p = 0.038). An increased frequency of autoimmune disorders such as co-morbidity was found in L412F COVID-19 males with specific class II HLA haplotypes prone to autoantigen presentation. Our analyses indicate that L412F polymorphism makes males at risk of severe COVID-19 and provides a rationale for reinterpreting clinical trials considering autophagy pathways.Abbreviations: AP: autophagosome; AUC: area under the curve; BafA1: bafilomycin A1; COVID-19: coronavirus disease-2019; HCQ: hydroxychloroquine; RAP: rapamycin; ROC: receiver operating characteristic; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2; TLR: toll like receptor; TNF/TNF-α: tumor necrosis factor.