title: Quantification of the adenylate cyclase toxin of Bordetella pertussis in vitro and during respiratory infection.
abstract: Whooping cough results from infection of the respiratory tract with Bordetella pertussis, and the secreted adenylate cyclase toxin (ACT) is essential for the bacterium to establish infection. Despite extensive study of the mechanism of ACT cytotoxicity and its effects over a range of concentrations in vitro, ACT has not been observed or quantified in vivo, and thus the concentration of ACT at the site of infection is unknown. The recently developed baboon model of infection mimics the prolonged cough and transmissibility of pertussis, and we hypothesized that measurement of ACT in nasopharyngeal washes (NPW) from baboons, combined with human and in vitro data, would provide an estimate of the ACT concentration in the airway during infection. NPW contained up to ≈ 10(8) CFU/ml B. pertussis and 1 to 5 ng/ml ACT at the peak of infection. Nasal aspirate specimens from two human infants with pertussis contained bacterial concentrations similar to those in the baboons, with 12 to 20 ng/ml ACT. When ≈ 10(8) CFU/ml of a laboratory strain of B. pertussis was cultured in vitro, ACT production was detected in 60 min and reached a plateau of ≈ 60 ng/ml in 6 h. Furthermore, when bacteria were brought into close proximity to target cells by centrifugation, intoxication was increased 4-fold. Collectively, these data suggest that at the bacterium-target cell interface during infection of the respiratory tract, the concentration of ACT can exceed 100 ng/ml, providing a reference point for future studies of ACT and pertussis pathogenesis.
authors: Division of Infectious Diseases and International Health, Department of Medicine, University of Virginia School of Medicine, Charlottesville, Virginia, USA.
authors: Joshua C
authors: JC
authors: Eby
authors: Mary C
authors: MC
authors: Gray
authors: Jason M
authors: JM
authors: Warfel
authors: Christopher D
authors: CD
authors: Paddock
authors: Tara F
authors: TF
authors: Jones
authors: Shandra R
authors: SR
authors: Day
authors: James
authors: J
authors: Bowden
authors: Melinda D
authors: MD
authors: Poulter
authors: Gina M
authors: GM
authors: Donato
authors: Tod J
authors: TJ
authors: Merkel
authors: Erik L
authors: EL
authors: Hewlett
mesh_terms: D037361:Adenylate Cyclase Toxin / Q000032:analysis*; D000818:Animals; D058491:Bacterial Load; D001886:Bordetella pertussis / Q000201:enzymology* / Q000302:isolation & purification; D002478:Cells, Cultured; D015169:Colony Count, Microbial; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D009305:Nasopharynx / Q000201:enzymology* / Q000382:microbiology; D010215:Papio; D014917:Whooping Cough / Q000382:microbiology*
chemical_list: D037361:Adenylate Cyclase Toxin