Phenotypic variants of meningococci and their potential in phagocytic interactions: The influence of opacity proteins, pili, PilC and surface sialic acids

In previous studies we have examined the roles of meningococcal surface structures (capsule, lipopolysaccharides, pill and opacity proteins: Opa and Ope) in bacterial interactions with human epithelial, endothelial 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 polymorphonuclear phagocytes (PMN). In addition, we examined the potential influence of the pilus-associated protein, PilC, previously known to affect epithelial cell interactions. The data show that, as with monocytes, opacity proteins affect bacterial interactions with PMN and require surface sialic acids (on capsule and LPS) to be down-modulated in order to function, Also, in contrast to their role in human epithelial and endothelial adherence, neither pill nor PilC expression had any effect on phagocytic cell interactions with respect to induction of chemiluminescence as well as phagocytic killing. Examination of the relative influence of Opa and Ope indicated that Opa proteins are more effective than Ope in PMN interactions whereas the reverse was the case with monocytes. These results suggest that Opa and Ope mediate interactions with phagocytic cells via distinct mechanisms. Observations presented here and reported previously collectively show that the structural requirements of meningococci for interacting with phagocytes, in the absence of opsonins, are present in the phenotype which is often isolated 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 appears to be refractory to interactions with phagocytic cells. (C) 1997 Academic Press Limited.