[WS5-2] Virulence factors of A. actinomycetemcomitans and their etiologic significance in periodontitis
Aggregatibacter actinomycetemcomitans (Aa), a facultative anaerobic gram-negative rod, is one of the oral commensals that is a causative etiological pathogen of aggressive periodontitis (AgP). The potential virulence factors of this organism, leukotoxin, cytolethal distending toxin (CDT), and lipopolysaccharide (LPS), have been studied extensively in the context of modulating the host immune response. Following colonization and attachment to the gingival epithelium, Aa employs these virulence factors to evade host innate defense mechanisms and drive a pathophysiological inflammatory response. This organism can induce bone resorption by inflammation in periodontal tissue. The JP2 Aa clone is considered a possible etiological agent of AgP in adolescents living in or originating from North Africa, where this disease is highly prevalent. The aggressive form, site specificity, racial tropism, onset in adolescence, and infection by Aa JP2 clone are characteristics of AgP. Although both the bacterium and the disease have been well studied, the relations between the virulence factors of this bacterium and its pathophysiology remain unclear. In this session, the mechanisms of action of Aa virulence factors in AgP will be presented. Next, the putative disease onset mechanism and therapeutic strategies for this disease based on this mechanism will be discussed.