Expression levels of the gene encoding tumor necrosis factor α (TNF-α), an inflammation mediator, were increased in the spleens of mice infected with the WT, but not in the spleens of mice infected with the ΔinvG ΔssaV or the PBS-injected controls, indicating that STm infection leads to increased expression of specific gene such as Tnfa in a virulence factor-dependent fashion (Fig 8D). Here, TNF is linked to infection.