IL6 and infection: Expression of genes encoding key cytokines (IL-6, TNFα, IL-1β) and BIRC3, which is involved in innate immune signalling and has been shown to increase in expression during infections of human cells with NTHi [48], were similar in mice infected with Hi2019ΔlldD and Hi2019WT at 6 h post-infection, while at 24 h and 48 h post-infection gene expression levels were reduced between 2.5- and 11-fold (S5 Fig, 2-Way ANOVA, p<0.05) in mice infected with Hi2019ΔlldD, in keeping with the reduction of Hi2019ΔlldD CFUs recovered at these timepoints.