Recombinant Actinobacillus actinomycetemcomitans cytolethal distending toxin proteins are required to interact to inhibit human cell cycle progression and to stimulate human leukocyte cytokine synthesis

• Published in: Infection and immunity Vol. 69; no. 9; pp. 5925 - 5930
• Main Authors: AKIFUSA, Sumio, POOLE, Stephen, LEWTHWAITE, Jo, HENDERSON, Brian, NAIR, Sean P
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01-09-2001
• Series: Note
• Subjects: Actinobacillus actinomycetemcomitans; Actinobacillus Infections - microbiology; Aggregatibacter actinomycetemcomitans - metabolism; Aggregatibacter actinomycetemcomitans - pathogenicity; Bacterial Toxins - genetics; Bacterial Toxins - metabolism; Bacterial Toxins - pharmacology; Bacteriology; Biological and medical sciences; CdtA protein; CdtB protein; CdtC protein; Cell Cycle; Cell Line; Cloning, Molecular; Cytokines - biosynthesis; Fundamental and applied biological sciences. Psychology; Genetics; Humans; interleukin 1b; Leukocytes, Mononuclear - immunology; Microbiology; Molecular Pathogenesis; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Human; Stomatology; Leukocyte; Escherichia coli; Cytokine; Stimulation; Subunit; Pasteurellaceae; Toxin; Periodontal disease; Cell line; Gene; Periodontitis; Actinobacillus actinomycetemcomitans; Cell cycle; Bacteria; Epithelial cell; Recombinant protein; Enterobacteriaceae; Clone
• ISSN: 0019-9567; 1098-5522
• DOI: 10.1128/IAI.69.9.5925-5930.2001

It has recently been discovered that Actinobacillus actinomycetemcomitans, an oral bacterium causing periodontitis, produces cytolethal distending toxin (CDT), a cell cycle-modulating toxin that has three protein subunits: CdtA, CdtB, and CdtC. In this study, we have cloned and expressed each toxin gene from A. actinomycetemcomitans in Escherichia coli and purified the recombinant Cdt proteins to homogeneity. Individual Cdt proteins failed to induce cell cycle arrest of the human epithelial cell line HEp-2. The only combinations of toxin proteins causing cell cycle arrest were the presence of all three Cdt proteins and the combination of CdtB and CdtC. A similar experimental protocol was used to determine if recombinant Cdt proteins were able to induce human peripheral blood mononuclear cells (PBMCs) to produce cytokines. The individual Cdt proteins were able to induce the synthesis by PBMCs of interleukin-1beta (IL-1beta), IL-6, and IL-8 but not of tumor necrosis factor alpha, IL-12, or granulocyte-macrophage colony-stimulating factor, with CdtC being the most potent and CdtB being the least potent cytokine inducer. There was evidence of synergism between these Cdt proteins in the stimulation of cytokine production, most markedly with gamma interferon, which required the minimum interaction of CdtB and -C to stimulate production.