Late P. aeruginosa CF isolates display low protease activity and decreased ability to inhibit antiviral response. (A) Characteristics of longitudinal isolates of P. aeruginosa from CF patients. (B) Protease activity of P. aeruginosa CF isolates was assessed using skim milk agar. (C) BEAS2B cells were pretreated with conditioned medium of P. aeruginosa from (A) or control medium and subsequently infected with RSV. Induction of MX1 and OAS1 mRNA were analyzed by qRT-PCR after 14 h. (D) Spearman correlation of protease activity and induction of MX1 or OAS1 mRNA measured in (B,C). (E) LasR genetic mutations and resulting changes in protein translation found in CF isolates described in (A). All experiments n = 4, ANOVA and Bonferroni post-test was used for statistical analysis. Significant differences were considered at *p < 0.05, **p < 0.01, and ***p < 0.001 as compared to the control condition. n.s., not significant.