SigB is required for the replication of SCV CF07-S within CF cells.

<p>(A) Infection kinetics of shCFTR Calu-3 cells (<i>i.e.</i>, CF-like cells) by strains CF07-L, CF07-S, CF07-SΔ<i>sigB</i> and CF07-SΔ<i>fnbA</i>. Statistically significant differences in CFU/insert recovered from infected cells are indicated (**, <i>P</i><0.01; ***, <i>P</i><0.001 ; ****, <i>P</i><0.0001 ; two-way ANOVA with Bonferonni's posttest, <i>n</i> = 3–7). (B) CFU ratios recovered from cells infected with CF07-L, CF07-S, CF07-SΔ<i>sigB</i> and CF07-SΔ<i>sigB</i> carrying the empty vector (pFM1) or the <i>sigB</i> expression vector (pFM2) 48 h post-invasion. For cells infected with strains carrying a vector, the post-invasion media was supplemented with 0.25 µM CdCl₂. Statistically significant differences between the CFU ratios recovered from cells infected with the different strains are indicated (*, <i>P</i><0.05; ***, <i>P</i><0.001; ANOVA with Tuckey's posttest, <i>n</i> = 3–7). (C) Host cell lysis was evaluated 48 h following invasion with CF07-L, CF07-S and CF07-SΔ<i>sigB</i> by performing LDH cytotoxicity assays. Statistically significant differences are indicated (*, <i>P</i><0.05; **, <i>P</i><0.01; ANOVA with Tuckey's posttest, <i>n</i> = 4). Results are expressed as means with standard deviations.