Sialidase Activity of the Periodontopathogen Tannerella forsythia Modulates Phagocytic Activity and Inflammatory Response of Macrophages.

Abstract

Sialidases (neuraminidase) are a large family of glycoside hydrolase enzymes found in a range of organisms that cleave the glycosidic bond between terminal sialic acids and underlying oligosaccharide chains. It has been demonstrated that Tannerella forsythia expresses two different sialidases, SiaH and NanH, with the latter being the primary sialidase. The NanH sialidase has been predicted to play a role in the organism's virulence based on in vitro data demonstrating that the NanH activity is responsible for promoting the organism’s ability to attach to and invade epithelial cells. The current study was undertaken to determine if NanH sialidase might impact the ability of T. forsythia to interact with and modulate the response of macrophages, the specialized phagocytes involved in the pathogenesis of periodontitis. For this purpose, we utilized in vitro phagocytic and cytokine assays using a human macrophage cell line challenged with either the wild-type or NanH-deficient T. forsythia strains. Our data showed that the NanH sialidase, by catalyzing the release of terminal sialic acid residues from macrophage surface receptors, can regulate phagocytic activity and cytokine responses. These data advance our knowledge of the NanH enzyme of T. forsythia as a potential virulence factor involved in the pathogenesis of periodontitis.