CXCL8 and infection: To test this, we infected the human colonic epithelial cell line HT-29 with S. Typhi mutants grown under non-invasive conditions (i.e., low salt) and measured secretion of the pro-inflammatory cytokine IL-8 as an indication of TLR-dependent signaling at 6 and 18 hours post-infection (p.i.)(Fig 6A and 6B).