The meningococcal PilT protein is required for induction of intimate attachment to epithelial cells following pilus-mediated adhesion

The ability of Neisseria meningitidis (MC) to interact with cellular barrie rs is essential to its pathogenesis. With epithelial cells, this process ha s been modeled in two steps. The initial stage of localized adherence is me diated by bacterial pill, After this phase, MC disperse and lose piliation, thus leading to a diffuse adherence. At this stage, microvilli have disapp eared, and MC interact intimately with cells and are, in places, located on pedestals of actin, thus realizing attaching and effacing (AE) lesions. Th e bacterial attributes responsible for these latter phenotypes remain unide ntified. Considering that bacteria are nonpiliated at this stage, pill cann ot be directly responsible for this effect. However, the initial phase of p ilus-mediated localized adherence is required for the occurrence of diffuse adherence, loss of microvilli, and intimate attachment, because nonpiliate d bacteria are not capable of such a cellular interaction. In this work, we engineered a mutation in the cytoplasmic nucleotide-binding protein PilT a nd showed that this mutation increased piliation and abolished the dispersa l phase of bacterial clumps as well as the loss of piliation, Furthermore, no intimate attachment nor AE lesions were observed. On the other hand, Pil T(-) MC remained adherent as piliated clumps at all times. Taken together t hese data demonstrate that the induction of diffuse adherence, intimate att achment, and AE lesions after pilus-mediated adhesion requires the cytoplas mic PilT protein.