Utility of mouse precision cut lung slices as an in vitro model for interrogating the lung immune response against bacterial pathogens in the context of immunomodulatory therapeutics.

High rates of respiratory infections have been observed in patients following treatment with immunomodulatory therapeutics, yet preclinical assessment and mechanistic understanding of drug-associated infection risk remains a challenge. Here, an ex vivo infection model of mouse precision-cut lung slices (PCLS) is described to address this gap. Naïve mouse PCLS were pre-treated with immunomodulatory drugs previously reported to exacerbate clinical infection risk (Idelalisib, Anakinra and Tofacitinib), followed by incubation with the lung pathogen Streptococcus pneumoniae. Bacterial uptake by the PCLS and cytokine release was measured to assess innate responses. Both Anakinra and Tofacitinib increased intracellular accumulation of bacteria within epithelial cells and reduced inflammatory cytokine release in a dose-dependent manner. Idelalisib also increased bacterial uptake with an inverse dose-response relationship, while the inhibitory effects on cytokine release were dose-dependent. These effects were confirmed in normal human bronchial epithelial cells (NHBE), suggesting that low concentrations of Idelalisib might negatively impact essential innate immune pathways. RNA-Seq analysis of the lung slices revealed the activation of key pathways linked to the innate immune response following infection, including PI3K signaling, oxidative stress response, cytoskeletal reorganization and autophagy. Notably, these pathways were modulated in the presence of Idelalisib and translation of the involvement of these pathways in the response to S. pneumoniae was confirmed in NHBE. In conclusion, the PCLS model offers potential to inform early risk assessment whilst aiding mechanistic understanding of the immunomodulatory impact of drug candidates on the lung.