Function
The type IV secretion system VirB/VirD4 is a major virulence determinant for subversion of human endothelial cell (HEC) function. VirB-dependent changes of HEC include massive cytoskeletal rearrangements, a proinflammatory activation by nuclear factor NF-kappa-B, inhibition of early and late events of apoptosis, leading to an increased cell survival, and, at high infection doses, a cytostatic or cytotoxic effect, which interfers with a potent VirB-independent mitogenic activity. These changes of HEC require the T4S coupling protein VirD4 and at least one of the effector proteins BepA-G. VirB2 seems to constitute the major pilus component.