TLR5 Mutation Ties Lung Microbiome to IPF - Drug Tested in Mice

Two drugs are approved for idiopathic pulmonary fibrosis, but neither improves symptoms — patients still die. IPF scars lung tissue until breathing becomes impossible, and its triggers have stayed largely mysterious. Now a team at the National Institute of Environmental Health Sciences has pinned down a genetic mechanism that links the lung microbiome to the disease, and tested a drug that blocks the pathway in mice.

First Genetic Link Between the Lung Microbiome and IPF

Stavros Garantziotis and his colleagues found that a mutation in the Tlr5 gene — which encodes a receptor that detects bacteria and triggers immune responses — makes mice far more vulnerable to lung fibrosis. TLR5 receptors normally live on airway cells and, after a lung injury, keep harmful bacterial populations in check. When the receptor is broken, the microbial balance shifts, fibrosis accelerates.

This is the first study to directly connect a genetic defect in the lung's immune surveillance with IPF development. Brian Oliver, a respiration researcher at the University of Technology Sydney, called it “a very novel idea” — most researchers would not have looked at TLR5 in the context of fibrotic lung disease.

Mice Without the Receptor Sicker, Die Faster

To model IPF, the researchers gave mice a drug that damages lung tissue. In animals with the Tlr5 gene deleted, fibrosis was significantly worse, weight loss more severe, and survival rates dropped compared to control mice that still had the functional receptor. The knockout mice also showed reduced microbial diversity and lower antimicrobial activity in their lung-lining cells.

Garantziotis argues that the TLR5 pathway acts as a gatekeeper after lung injury: it stops opportunistic bacteria from overgrowing and triggering runaway scarring. Without it, the lung can’t recover.

Targeting the Pathway Blocks Fibrosis

If the same mechanism operates in humans — and the authors point to correlational data suggesting it does — then a drug that restores or activates TLR5 signaling could prevent IPF from progressing after an initial injury. Garantziotis’ team has already tested a compound in the mouse model that targets the TLR5 protein and prevented fibrosis development.

The two existing IPF drugs (pirfenidone and nintedanib) only slow decline. A therapy that intervenes at the root cause — the microbiome-immune crosstalk — would be a fundamentally different approach. Clinical trials in humans would be the next hurdle, but for a disease that has seen no symptom-improving therapy, even a clear mechanism is progress.

Source: This mysterious lung disease affects millions of people - a drug tested in mice shows promise
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