This blog has previously highlighted the use of genetically modified bacteria as therapeutics, including a previous post detailing its effectiveness in treating patients impaired in proper nitrogen regulation. Here we focus on recent work from Korea in which a non-virulent form of Salmonella was engineered to express Vibrio vulnificus flagellin B (FlaB). Using human cell culture they demonstrated that this Salmonella resulted in infiltration of tumors with immune cells with activation of M1 macrophages and inhibition of M2 macrophages. Using knockout cell lines, they also showed that this activity required TL4 signaling. Finally, using mice they showed significant decreases in tumor size in about half of the animals treated. This is an exciting step forward in using genetically modified bacteria in cancer immunotherapeutics.