title: The cytolethal distending toxin of Aggregatibacter actinomycetemcomitans inhibits macrophage phagocytosis and subverts cytokine production.
abstract: Aggregatibacter actinomycetemcomitans is an important periodontal pathogen that can participate in periodontitis and other non-oral infections. The cytolethal distending toxin (Cdt) is among the virulence factors produced by this bacterium. The Cdt is also secreted by several mucosa-associated Gram-negative pathogens and may play a role in perpetuating the infection by modulating the immune response. Although the toxin targets a wide range of eukaryotic cell types little is known about its activity on macrophages which play a key part in alerting the rest of the immune system to the presence of pathogens and their virulence factors. In view of this, we tested the hypothesis that the A. actinomycetemcomitans Cdt (AaCdt) disrupts macrophage function by inhibiting phagocytic activity as well as affecting the production of cytokines. Murine macrophages were co-cultured with either wild-type A. actinomycetemcomitans or a Cdt(-) mutant. Viable counts and qPCR showed that phagocytosis of the wild-type strain was significantly reduced relative to that of the Cdt(-) mutant. Addition of recombinant Aa(r)Cdt to co-cultures along with the Cdt(-) mutant diminished the phagocytic activity similar to that observed with the wild type strain. High concentrations of Aa(r)Cdt resulted in decreased phagocytosis of fluorescent bioparticles. Nitric oxide production was modulated by the presence of Cdt and the levels of IL-1β, IL-12 and IL-10 were increased. Production of TNF-α did not differ in the co-culture assays but was increased by the presence of Aa(r)Cdt. These data suggest that the Cdt may modulate macrophage function in A. actinomycetemcomitans infected sites by impairing phagocytosis and modifying the pro-inflammatory/anti-inflammatory cytokine balance.
authors.affiliation: Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil. Electronic address: esayuria@usp.br.
authors.forename: Ellen Sayuri
authors.initials: ES
authors.lastname: Ando-Suguimoto
authors.affiliation: Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
authors.forename: Maike Paulino
authors.initials: MP
authors.lastname: da Silva
authors.affiliation: Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
authors.forename: Dione
authors.initials: D
authors.lastname: Kawamoto
authors.affiliation: Division of Periodontology, Diagnostic Sciences and Dental Hygiene, Ostrow School of Dentistry of University of Southern California, USA.
authors.forename: Casey
authors.initials: C
authors.lastname: Chen
authors.affiliation: Department of Microbiology, School of Dental Medicine, University of Pennsylvania, PA, USA.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: DiRienzo
authors.affiliation: Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
authors.forename: Marcia Pinto Alves
authors.initials: MP
authors.lastname: Mayer
mesh_terms: D016976:Aggregatibacter actinomycetemcomitans / Q000737:chemistry* / Q000254:growth & development; D000818:Animals; D001427:Bacterial Toxins / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D015169:Colony Count, Microbial; D016207:Cytokines / Q000096:biosynthesis*; D042541:Intracellular Space / Q000187:drug effects / Q000382:microbiology; D008264:Macrophages / Q000187:drug effects / Q000382:microbiology* / Q000473:pathology*; D051379:Mice; D009569:Nitric Oxide / Q000096:biosynthesis; D010587:Phagocytosis / Q000187:drug effects*; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism
chemical_list: D001427:Bacterial Toxins; D016207:Cytokines; C067044:cytolethal distending toxin; D009569:Nitric Oxide
keywords: Aggregatibacter actinomycetemcomitans; Cytolethal distending toxin; Macrophage; Phagocytosis