title: Neuraminidase-dependent hamagglutination of human erythrocytes by human strains of Actinomyces viscosus and Actinomyces naeslundii.
abstract: Human A, B, and O erythrocytes (RBC) were agglutinated by many human strains of Actinomyces viscosus and A. naeslundii. At 37 degrees C, these bacterium-mediated hemagglutination reactions required the action of bacterial neuraminidase upon the RBC; however, at 4 degrees C, the requirement for neuraminidase was not as striking. Bacterial cell suspensions which caused hemagglutination at 37 degrees C contained both soluble extracellular and cell-associated neuraminidase activities as shown by enzyme assays using a soluble substrate (i.e., alpha 1-acid glycoprotein). Bacterium-mediated hemagglutination occurred only in the presence of soluble neuraminidase activity, and the rate of hemagglutination could be inhibited by 2-deoxy-2,3-dehydro-N-acetylneuraminic acid, a competitive inhibitor of purified soluble neuraminidase from A. viscosus T14V. Suspensions of bacteria which contained only cell-associated neuraminidase activity were unable to initiate hemagglutination, but they caused immediate hemagglutination when mixed with neuraminidase-treated RBC. All hemagglutination reactions were reversible in the presence of 0.02 M lactose and were abolished by heating (85 degrees C for 30 min) the actinomycete cells but not the RBC. The proposed mechanism of hemagglutination involves two sequential steps: (i) the action of neuraminidase to unmask galactose-containing receptors on the RBC and (ii) the multivalent binding of these receptors by many low-affinity lection sites on the bacterial surface.
mesh_terms: D000190:Actinomyces / Q000201:enzymology / Q000276:immunology*; D055598:Chemical Phenomena; D002621:Chemistry; D003016:Clostridium perfringens / Q000201:enzymology; D003080:Cold Temperature; D003773:Dental Plaque / Q000276:immunology; D004912:Erythrocytes / Q000276:immunology*; D006023:Glycoproteins / Q000378:metabolism; D006384:Hemagglutination; D006801:Humans; D009439:Neuraminidase / Q000494:pharmacology*; D012794:Sialic Acids / Q000494:pharmacology; D012995:Solubility; D013045:Species Specificity
chemical_list: D006023:Glycoproteins; D012794:Sialic Acids; D009439:Neuraminidase