Consistently, wild-type (WT) typhoid toxin triggered a marked increase in the phosphorylation at Ser139 of H2AX, whereas little to no pH2AX signal was observed in cells left uninfected or infected with S. Typhi carrying the CdtBH160Q catalytic mutant (Fig 4B and 4C), indicating that this in vitro infection model can quantitatively evaluate the neutralizing function of antibodies targeting typhoid toxin. This evidence concerns the gene H2AX and infection.