Cell-specific activation of nuclear factor-kappa B by the parasite Trypanosoma cruzi promotes resistance to intracellular infection

The transcription factor nuclear factor-kappa B (NF-kappa B) is central to the innate and acquired immune response to microbial pathogens, coordinatin g cellular responses to the presence of infection. Here we demonstrate a di rect role for NF-kappa B activation in controlling intracellular infection in nonimmune cells. Trypanosoma cruzi is an intracellular parasite of mamma lian cells with a marked preference for infection of myocytes. The molecula r basis for this tissue tropism is unknown. Trypomastigotes, the infectious stage of T. cruzi, activate nuclear translocation and DNA binding of NF-ka ppa B p65 subunit and NF-kappa B-dependent gene expression in epithelial ce lls, endothelial cells, and fibroblasts. Inactivation of epithelial cell NF -kappa B signaling by inducible expression of the inhibitory mutant I kappa BaM significantly enhances parasite invasion. T, cruzi do not activate NF- kappa B in cells derived from skeletal, smooth, or cardiac muscle, despite the ability of these cells to respond to tumor necrosis factor-alpha with N F-kappa B activation. The in vitro infection level in these muscle-derived cells is more than double that seen in the other cell types tested. Therefo re, the ability of T. cruzi to activate NF-kappa B correlates inversely wit h susceptibility to infection, suggesting that NF-kappa B activation is a d eterminant of the intracellular survival and tissue tropism of T. cruzi.