Prophylactic Inhaled Pattern Recognition Receptor Agonists Reprogram Lung Epithelial Response and Prevent Type 2...

Area of Science:

• Immunology
• Pulmonology
• Allergy Research

Background:

• Allergic lung diseases, such as those induced by house dust mite (HDM), involve complex immune responses in the airways.
• Current treatments aim to manage symptoms, but preventing sensitization and underlying inflammation remains a key challenge.
• The precise mechanisms by which prophylactic treatments modulate lung immune cell interactions to prevent allergic inflammation are not fully understood.

Purpose of the Study:

• To elucidate the immunomodulatory effects of inhaled ODN M362 and Pam2CSK4 (Pam2ODN) on lung cells and immune responses in a mouse model of allergic lung disease.
• To investigate how Pam2ODN pretreatment influences dendritic cell (DC) populations and T helper cell polarization following house dust mite (HDM) sensitization.
• To determine the impact of Pam2ODN on gene expression and chromatin accessibility in lung epithelial cells.

Main Methods:

• Mice were prophylactically treated with inhaled Pam2ODN before sensitization with house dust mite (HDM).
• Immune cell populations (dendritic cells, T cells) in the lungs were analyzed using flow cytometry.
• Bulk and single-cell RNA sequencing (RNA-seq) were performed on whole lung tissue and isolated lung epithelial cells.
• Analysis of gene expression, inflammatory pathways, and chromatin accessibility was conducted.

Main Results:

• Pam2ODN inhalation before HDM sensitization suppressed airway Th2 polarization without altering Th1 or regulatory T cell (Treg) responses.
• Pretreatment with Pam2ODN inhibited the recruitment of monocyte-derived dendritic cells (moDCs) and conventional Type 2 dendritic cells (DC2s).
• Pam2ODN prevented the HDM-induced reduction in conventional Type 1 dendritic cells (DC1s) and restricted the expression of pro-inflammatory transcripts in the lung.
• Single-cell analysis revealed that Pam2ODN attenuated pro-inflammatory pathways and chromatin accessibility in lung epithelial cells.

Conclusions:

• Inhaled Pam2ODN reprograms lung epithelial cells to reduce the production of Th2-promoting cytokines in response to allergens.
• Pam2ODN effectively modulates dendritic cell populations, preserving protective DC1s while limiting inflammatory DC recruitment.
• These findings support Pam2ODN as a potential prophylactic strategy to mitigate chronic allergic lung diseases by establishing immune tolerance.