INTERACTION OF NEISSERIA-MENINGITIDIS WITH A POLARIZED MONOLAYER OF EPITHELIAL-CELLS

An important step in the pathogenesis of Neisseria meningitidis is the crossing of two cellular barriers, one in the nasopharynx and one in the brain. To approach the mechanisms by which this bacterium can achi eve these goals, we studied the interactions between N. meningitidis a nd a monolayer of polarized tight junction-forming T84 cells grown on filter units. A capsulated, piliated, Opa(-), and Opc(-) N. meningitid is strain is shown to be capable of adhering to and crossing this mono layer several orders of magnitude more efficiently than an isogenic no npiliated derivative. This bacterial interaction does not affect the b arrier function of tight junctions, as assessed by (i) the absence of modification of the transepithelial resistance, (ii) the lack of incre ase of [H-3]inulin penetration across the monolayer, and (iii) the abs ence of delocalization of ZO-1, a tight junction protein. Electron mic roscopy studies and confocal examinations demonstrated that N. meningi tidis (i) induces cytoskeletal rearrangements with actin polymerizatio n beneath adherent bacteria, (ii) is intimately attached to the apical membrane of the cells, and (iii) can be internalized inside cells. Im munofluorescent staining with antipilus antibodies showed evidence tha t meningococcal piliation was dramatically reduced at later time point s of bacterial cell interaction compared to the early phase of this in teraction. In addition, adhesive bacteria recovered from an infected m onolayer are piliated, capsulated, Opa(-), and Opc(-), a phenotype sim ilar to that of the parental strain. Taken together, these data demons trate that following pilus-mediated adhesion, N. meningitidis is invol ved in an intimate attachment which requires a bacterial component dif ferent from Opa and Ope and that meningococci cross a monolayer of tig ht-junction-forming epithelial cells by using a transcellular pathway rather than a paracellular route.