Inactivation of DsbA alters the behaviour of Shigella flexneri towards murine and human-derived macrophage-like cells

The mutants of Shigella flexneri, Sh4 (dsbA::kan) and Sh42 (dsbA33G), behav e differently towards murine and human-derived macrophage-like cells in vit ro. Sh4 was trapped in the phagocytic. vacuoles of the murine J774 cells as evidenced by its colony forming units plus and minus chloroquine exposure in a gentamicin protection assay, and by light and transmission electron mi croscopy (TEM). Sh42, similar to the wild-type M90TS, was able to escape fr om the vacuoles and kill host cells presumably by inducing apoptosis. In U9 37 cells, unlike M90TS that was free in the cytosol, both Sh4 and Sh42 grew poorly. TEM revealed that Sh4 and Sh42 were trapped within the U937 phagoc ytic vacuoles. Furthermore, the two mutants induced different patterns of i nterleukin-1 beta and tumour necrosis factor-alpha expression, which might explain why they possess different immunogenic properties in vivo. (C) 2001 Federation of European Microbiological Societies. Published by Elsevier Sc ience B.V. All rights reserved.