OM-85’s anti-rhinovirus response assessed on human primary nasal epithelial cells

OM-85 (Broncho-Vaxom®) is a bacterial lysate known for its beneficial effects on respiratory tract infections and is currently used orally as a preventive measure. Recently, airway application of OM-85 also conferred protective effects. Respiratory infections are caused among others by rhinoviruses (RV), which use the nasal epithelium as an initial contact site. In an attempt to get a deeper understanding of OM-85’s protective mechanisms, we investigated if the microbial product modulates the defence functions of the nasal epithelium. Human primary nasal epithelial cells (pNECs) grown at the air-liquid interface underwent basolateral or apical OM-85 treatment, to mimic the oral and nasal application of the drug. During or after the treatment and subsequent RV-16 infection, the effect of the microbial product on RV replication and pNEC anti-RV innate immune signalling was investigated. Additionally, epithelial barrier integrity was assessed and the functioning of the mucociliary escalator was evaluated by the ciliary beating frequency (CBF). RV replication, the anti-RV innate immune response (gene expression of CXCL10, CXCL8, IL6, and RV relevant pathogen recognition receptors), and the epithelial barrier integrity were not modulated by OM-85 treatment in our set-up. Conversely, the CBF was increased by 6-23% in pNECs treated basolaterally with OM-85 during differentiation and in apically treated mature pNECs. Our results show no modulation of the anti-RV response by OM-85 in pNECs. CBF on the other hand was increased by the treatment, but it is unknown whether this effect can contribute to the in vivo reduction of respiratory disease severity, as observed in animal and clinical studies.