Figure 6.

TrxA contributes to L. monocytogenes infection and virulence within mice. (A) Adhesion, invasion, and proliferation of L. monocytogenes in human intestinal epithelial cells, Caco-2. Cells infected with L. monocytogenes strains at the indicated time points were lysed and viable bacteria serially plated on BHI agar plates. The number of bacteria able to invade cells and survive are expressed as means ± SD of the recovery rate for each strain. ^*P < 0.05; ^**P < 0.01. (B) Actin tail formation in Caco-2 cells infected with L. monocytogenes strains 6 h post inoculation. Bacteria were detected with anti-Lm (green), bacteria actin tails and host actin using phalloidine (red), and cell nucleus labeled with DAPI (blue). Scale bar is 10 μm. The high-magnification images displayed at the bottom of each image show F-actin (red), bacteria (green), and nuclei (blue). (C) Proliferation of L. monocytogenes in mouse organs. Mice inoculated i.p. with L. monocytogenes strains (1 × 10⁶ CFU) were euthanized 48 h after infection, and organs (liver and spleen) recovered and homogenized. Homogenates were serially plated on BHI agar. Numbers of bacteria colonized in liver and spleen are expressed as means ± SD of the recovery rate per organ for each group. ^*P < 0.05; ^**P < 0.01; ns means no significance. (D,E) The interactions analysis of TrxA (D) or the oxidized forms of TrxA (TrxA_ox) (E) with PrfA, the central virulence regulator of Listeria, by using the ITC assay. For all titrations, raw data are presented in the upper panel and fitted binding curves in the lower panel.