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. Transcriptome profiling in unfractionated lung tissue from mice treated intranasally with bacterial lysate (OM-85)