Requirements for invasion of epithelial cells by Actinobacillus actinomycetemcomitans

Abstract

Actinobacilus actinomycetemcomitans, an oral bacterium implicated in human periodontal disease, was recently demonstrated to invade cultured epithelial cells (D. H. Meyer, P. K. Sreenivasan, and P. M. Fives-Taylor, Infect. Immun. 59:2719-2726. This report characterizes the requirements for invasion of KB cells by A. actinomycetemcomitans. The roles of bacterial and host factors were investigated by using selective agents that influence specific bacterial or host cell functions. Inhibition of bacterial protein synthesis decreased invasion, suggesting the absence of a preformed pool of proteins involved in A. actinomycetemcomitans invasion. Inhibition of bacterial and eukaryotic energy synthesis also decreased invasion, confirming that A. actinomycetemcomitans invasion is an active process. Bacterial adherence to KB cells was indicated by scanning electron microscopy of infected KB cells. Further, the addition ofA. actinomycetemcomitans-specific serum to the bacterial inoculum reduced invasion substantially, suggesting a role for bacterial attachment in invasion. Many of the adherent bacteria invaded the epithelial cells under optimal conditions. Inhibitors of receptor-mediated endocytosis inhibited invasion byA. actinomycetemcomitans. Like that of many facultatively intracellular bacteria, A. actinomycetemcomitans invasion was not affected by eukaryotic endosomal acidification. These are the first published observations describing the requirements for epithelial cell invasion by a periodontopathogen. They demonstrate that A. actinomycetemcomitans utilizes a mechanism similar to those used by many but not all invasive bacteria to gain entry into eukaryotic cells. 1239 Vol. 61, No. 4 on July 16, 2020 by guest http://iai.asm.org/ Downloaded from human periodontal disease.

Mechanisms of Actinobacillus Actinomycetemcomitans‐Induced Expression of Interleukin‐8 in Gingival Epithelial Cells

“…Regarding the pathogenesis of A.a.-associated periodontal lesions, it is known that microorganisms adhering to as well as invading epithelial cells are major mechanisms of infection. 35 However, our data show that invasion by vital A.a. is not necessary for epithelial upregulation of IL-8, since sonicated extracts induced an IL-8 response comparable to that reported from vital bacteria. 2 This has important implications in clinical periodontics, because bacterial virulence factors that remain in the periodontal pocket can activate immune responses with detrimental consequences for the periodontium.…”

Subgingival Chlorhexidine Varnish Administration as an Adjunct to Same‐Day Full‐Mouth Root Planing. I. Clinical Observations

“…Indeed, bacterial invasion in cementum, radicular dentin, and the surrounding periodontal tissues has been reported. [23][24][25][26][27][28] Chemomechanical treatment concepts were developed as a result of the increased awareness of these limitations of SRP.…”

Virulence factors of Actinobacillus actinomycetemcomitans relevant to the pathogenesis of inflammatory periodontal diseases

“…The ability to invade was strain-dependent with the most invasive being as invasive as entero-invasive Escherichia coli. Subsequently, these workers reported that invasion was prevented by inhibition of bacterial protein synthesis, bacterial energy produc-tion, mammalian cell energy production and receptor-mediated endocytosis [35]. Another epithelial cell line susceptible to invasion by A. actinomycetemcomitans is HEp-2 (derived from an epidermoid carcinoma of the larynx) from which viable bacteria could be recovered [36].…”