Biology subjects

Cayet, D.

Publications and source records attributed to Cayet, D..

4 recordsLinked to original sources

bioRxiv2025

Local tolerance and innate immune activation of primary human respiratory cells exposed to flagellin

Antibiotic-resistant respiratory infections can lead to treatment failure, highlighting the need for alternative strategies. FLAMOD, a recombinant flagellin, stimulates innate immunity via Toll-like receptor 5 when delivered intranasally. In mice, FLAMOD protects against bacterial pneumonia. The protection is associated with activation of airway epithelial cells. This study aimed to assess the tolerance of human primary respiratory epithelium to FLAMOD administered apically as liquid droplets or by nebulization, to measure the innate immune response, and the pharmacokinetics of FLAMOD. We used epithelia reconstituted from human nasal and bronchial (MucilAir), small airways (SmallAir) and alveolar (AlveolAir) primary epithelial cells, cultured at the air-liquid interface. We report that daily administration of escalating doses of FLAMOD for 5 days was well tolerated by epithelia as barrier integrity, cilia motion and cell viability were not affected. FLAMOD was rapidly degraded without leakage into the basal compartment. Each epithelial model exhibited responses involving pathways of innate defense and immune cell infiltration, which were dose-dependent, with an effective concentration of FLAMOD in the picomolar range. Similar tolerance profile and immune responses were obtained with airway epithelium from cystic fibrosis and chronic obstructive pulmonary disease patients. In conclusion, this study supports the stimulation of epithelial Toll-like receptor 5 signaling to fight against infections of vulnerable patients.

cell biology↗

bioRxiv2025

Flagellin-mediated TLR5 activation enhances innate immune responses in healthy and diseased human airway epithelium

Bacterial pneumonia poses a significant challenge to public health, often leading to antibiotic treatment failure. Enhancing innate immunity represents a promising adjunctive strategy to conventional antibiotic therapy. Bacterial flagellin, a Toll-like receptor 5 (TLR5) agonist, has been shown to stimulate innate immune defenses when delivered via the respiratory route, demonstrating efficacy in both preventing and treating bacterial pneumonia in murine models. This protective effect is primarily mediated through TLR5-driven activation of airway epithelial cells. This study aimed to characterize the immunomodulatory effects of flagellin on human primary respiratory epithelium. Using the MucilAir air-liquid interface model and RNA sequencing, we demonstrated that apical administration of flagellin induced robust immune responses in airway epithelium derived from healthy individuals, as well as patients with chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF). TLR5-mediated epithelial signaling triggered key immune-related pathways, including cytokine production, leukocyte chemotaxis, neutrophil recruitment, and antimicrobial defense, with strong commonalities across healthy and diseased airway epithelia. Furthermore, we demonstrated that flagellin effectively activated epithelial immune responses even in the presence of the bacteria Pseudomonas aeruginosa or Streptococcus pneumoniae. However, epithelial activation alone was insufficient to directly limit bacterial colonization or replication, highlighting the potential role of epithelial-immune cell interactions in achieving effective bacterial clearance. These findings support TLR5 activation as a promising therapeutic strategy to enhance host defense mechanisms and improve treatment outcomes for bacterial pneumonia in both healthy individuals and patients with COPD or CF.

immunology↗

bioRxiv2025

Flagellin nebulization enhances respiratory immune responses in the porcine model

Respiratory delivery of the Toll-like receptor 5 agonist FLAMOD, a recombinant flagellin, offers a promising approach for treating bacterial pneumonia. FLAMOD stimulates the airway epithelium, mobilizing and activating immune cells and effectors to combat infections. While previous evidences were obtained in mouse models, this study represents the first comprehensive assessment of FLAMOD delivered by nebulization in pigs. Our results demonstrate that a single nebulization of FLAMOD did not cause any adverse effects on clinical parameters. Histological analysis supported that FLAMOD treatment led to immune cell infiltration in the lung tissue, indicative of an active immune response. Flow cytometry confirmed granulocyte recruitment in conducting airways. RNA sequencing established immune activation across the respiratory tract, from the nose, trachea, bronchi to the lungs, highlighting innate immunity, bacterial defense, cytokine and chemokine signaling, and granulocyte chemotaxis as key biological pathways. These findings demonstrated the capacity of FLAMOD to induce a robust and common immune response throughout the porcine respiratory system as well as specific compartmentalized immune signatures. This study establishes FLAMOD as a potent activator of innate immunity, providing a proof-of-concept for inhalation-based therapeutic strategies to combat bacterial pneumonia in the clinical setting.

immunology↗

bioRxiv2024

Targeted delivery of flagellin by nebulization offers optimized respiratory immunity and defense against pneumococcal pneumonia

Novel therapeutic strategies are urgently needed to combat pneumonia caused by Streptococcus pneumoniae strains resistant to standard-of-care antibiotics. Previous studies have shown that targeted stimulation of lung innate immune defenses through intranasal administration of the Toll-like receptor 5 agonist flagellin, improves the treatment of pneumonia when combined with antibiotics. To promote translation to the clinic application, this study assessed the direct delivery of flagellin to the airways through nebulization using a vibrating mesh nebulizer in mice. Intranasal delivery achieved approximately 40% lung deposition of the administered flagellin dose, whereas nebulization yielded less than 1%. Despite these differences, nebulized flagellin induced a transient activation of lung innate immunity characterized by cytokine/chemokine production and neutrophil infiltration into airways analogous to intranasal administration. Furthermore, inhalation by nebulization resulted in an accelerated resolution of systemic pro-inflammatory responses. Lastly, adjunct therapy combining nebulized flagellin and amoxicillin proved effective against antibiotic-resistant pneumococcal pneumonia in mice. We posit that flagellin aerosol therapy represents a safe and promising approach to address bacterial pneumonia within the context of antimicrobial resistance.

microbiology↗