MAPK8 and infection: To test whether the presence of OspF altered MAPK signaling during infection, we compared MAPK phosphorylation patterns in mammalian cells infected with wild-type or ΔospF Shigella. As previously observed, infection with wild-type Shigella resulted in strong SAP/JNK phosphorylation [28], weak ERK phosphorylation [29], and no detectable p38 phosphorylation (Figure 4A).