PHENOTYPIC VARIANTS OF MENINGOCOCCI AND THEIR POTENTIAL IN PHAGOCYTICINTERACTIONS - THE INFLUENCE OF OPACITY PROTEINS, PILI, PILC AND SURFACE SIALIC ACIDS

In previous studies we have examined the roles of meningococcal surfac e structures (capsule, lipopolysaccharides, pill and opacity proteins: Opa and Ope) in bacterial interactions with human epithelial, endothe lial and mononuclear phagocytic cells. In the current investigations, using defined derivatives of a serogroup A strain C751 and a serogroup B strain MC58, we studied the roles of these structures with human po lymorphonuclear phagocytes (PMN). In addition, we examined the potenti al influence of the pilus-associated protein, PilC, previously known t o affect epithelial cell interactions. The data show that, as with mon ocytes, opacity proteins affect bacterial interactions with PMN and re quire surface sialic acids (on capsule and LPS) to be down-modulated i n order to function, Also, in contrast to their role in human epitheli al and endothelial adherence, neither pill nor PilC expression had any effect on phagocytic cell interactions with respect to induction of c hemiluminescence as well as phagocytic killing. Examination of the rel ative influence of Opa and Ope indicated that Opa proteins are more ef fective than Ope in PMN interactions whereas the reverse was the case with monocytes. These results suggest that Opa and Ope mediate interac tions with phagocytic cells via distinct mechanisms. Observations pres ented here and reported previously collectively show that the structur al requirements of meningococci for interacting with phagocytes, in th e absence of opsonins, are present in the phenotype which is often iso lated from the nasopharynx (asialylated, piliated, Opa/Opc(+)) whereas the phenotype prevalent in the blood (sialyted, piliated, Opa/Opc(+)) retains the ability to adhere to endothelial cells (via pill) but app ears to be refractory to interactions with phagocytic cells. (C) 1997 Academic Press Limited.