Intranasal administration of OM-85, a bacterial lysate, alters lung transcriptional profiles and protects against experimental asthma

Background: Microbial interventions against allergic asthma have robust epidemiologic underpinnings and the potential to recalibrate disease-inducing immune responses. Oral administration of OM-85, a standardized lysate of human airways bacteria, is widely used empirically to prevent respiratory infections, and a clinical trial is testing its ability to prevent asthma in at-risk children. On the other hand, we previously showed that intra-nasal administration of products from microbe-rich farm environments abrogate experimental allergic asthma. Objectives: To investigate whether direct administration of OM-85 to the airway compartment protects against experimental allergic asthma, and to identify protective cellular and molecular mechanisms activated through this natural route. Methods: BALB/cJ mice (7-8 weeks old) sensitized and challenged with Ovalbumin received OM-85 intra-nasally, and cardinal cellular and molecular asthma phenotypes were measured. Murine lung gene expression was profiled by RNA-sequencing. Results: Airway administration of OM-85 suppressed allergic asthma and altered the transcriptome profile in unfractionated lung tissue. Conclusion We provide the first demonstration that administration of a standardized bacterial lysate to the airway compartment protects from experimental allergic asthma by engaging multiple immune pathways. Overall design: Transcriptome profiling in unfractionated lung tissue from mice treated intranasally with bacterial lysate (OM-85)