One of the major virulence factors of H.
pylori is the vacuolating toxin VacA (13, 19, 26). VacA is
expressed as a 140-kDa protoxin and undergoes proteolytic
processing to yield an 88-kDa secreted toxin (13). VacA is
secreted through an autotransporter (type V) pathway as a
soluble protein into the extracellular space, and a proportion
also remains attached to the bacterial cell surface