Effect of Vibrio cholerae neuraminidase on the phagocytosis of E. coli by macrophages in vivo and in vitro.

The mechanisms by which Vibrio cholerae neuraminidase VCN acts as an adjuvant is unclear. We have studied the effect of VCN on the phagocyotsis of E. coli 0111 K58 by macrophages in vivo and in vitro. (1) Using and in vivo intraperitoneal clearance test we have shown that prior injection of VCN (50 units/mouse) into the peritoneal cavity of mice enhances the clearance of the bacteria as efficiently as an optimal amount of opsonizing antiserum. We have also shown that the enhancement of intraperitoneal clearance by VCN is due to phagocytosis and intracellular killing of the organisms by macrophages. (2) VCN does not enhance the i.v. clearance of E. coli o111 K58. (3) VCN promotes the attachment of the organisms to and phagocytosis by peritoneal macrophages in vitro. Data are provided which suggest that the promotion of attachment and phagocytosis by VCN cannot be explained by a mere increase of passive absorption of the bacteria to the cell wall.