THE PILA REGULATORY GENE MODULATES THE PILUS-MEDIATED ADHESION OF NEISSERIA-MENINGITIDIS BY CONTROLLING THE TRANSCRIPTION OF PILC1

Adherence to eukaryotic cells is essential in the pathogenesis of Neis seria meningitidis. Pllus-mediated adhesion has been shown to play an essential role in this process, Pilin, the pilus major subunit, and tw o pilus associated proteins, PilC1 and PIlC2, are key components in me ningococcal adhesiveness, Phase and/or antigenic variation of these mo lecules are the only identified means by which N. meningitidis modulat es pilus-mediated adhesion, PIlA/PilB is a pleiotropic regulatory syst em first characterized in Neisseria gonorrhoeae where it controls pili n gene transcription. Similar alleles are found in N. meningitidis, To address the role of this regulatory pathway in N. meningitidis, we en gineered a meningococcal pilA mutant strain and analysed the consequen ces of this mutation on pilus-mediated adhesion using epithelial Hec-1 -B cells, This mutation resulted in a threefold reduction in adhesiven ess, As no change in the amount of pilin nor in pilin gene mRNA was de tected, we compared the expression of the pilC genes in both pilA and parental strains, Two transcriptional fusions pilC1-lacZ and pilC2-lac Z were constructed, A threefold reduction in beta-galactosidase activi ty was observed in the pilA mutant strain harbouring the pilC1-lacZ fu sion, No effect of the pilA mutation on p-galactosidase activity was o bserved in the strain carrying the pilC2-lacZ fusion, Gel retardation experiments confirmed that the PIlA protein binds to the promoter regi on of pilC1 but not of pilC2. Taken together, these data demonstrate t hat PIIA modulates meningococcal adhesiveness via the transcription of pilC1. Thus, in addition to phase variation, a more co-ordinate and r esponsive system may allow a fine adaptation of adhesiveness of mening ococci to various environmental signals.