Bordetella pertussis Adenylate Cyclase Toxin Disrupts Functional Integrity of Bronchial Epithelial Layers

Post-print (lokagerð höfundar)The airway epithelium restricts the penetration of inhaled pathogens into the underlying tissue and plays a crucial role in the innate immune defense against respiratory infections. The whooping cough agent, Bordetella pertussis, adheres to ciliated cells of the human airway epithelium and subverts its defense functions through the action of secreted toxins and other virulence factors. We examined the impact of B. pertussis infection and of adenylate cyclase toxin-hemolysin (CyaA) action on the functional integrity of human bronchial epithelial cells cultured at the air-liquid interface (ALI). B. pertussis adhesion to the apical surface of polarized pseudostratified VA10 cell layers provoked a disruption of tight junctions and caused a drop in transepithelial electrical resistance (TEER). The reduction of TEER depended on the capacity of the secreted CyaA toxin to elicit cAMP signaling in epithelial cells through its adenylyl cyclase enzyme activity. Both purified CyaA and cAMP-signaling drugs triggered a decrease in the TEER of VA10 cell layers. Toxin-produced cAMP signaling caused actin cytoskeleton rearrangement and induced mucin 5AC production and interleukin-6 (IL-6) secretion, while it inhibited the IL-17A-induced secretion of the IL-8 chemokine and of the antimicrobial peptide beta-defensin 2. These results indicate that CyaA toxin activity compromises the barrier and innate immune functions of Bordetella-infected airway epithelia.We are grateful to Branislav Vecerek for providing anti-Bordetella serum. Christine Terryn graciously provided the macro for evaluating TiJOR. Blanka Jurkova is acknowledged for excellent technical help. This work was supported by a grant to Gudmundur H. Gudmundsson from the Icelandic Centre for Research (RANNIS - 152370) and the University of Iceland Research Fund. Further support came from Czech CSF grants GA15-09157S (to R.O.), GA18-20621S (to P.S.), and NV16-28126A (to P.S.); grant LM2015064 from the Ministry of Education, Youth and Sports of the Czech Republic (to R.O.); and the Modernization and Support the Research Activities of the National Infrastructure for Translational Medicine EATRIS-CZ project (CZ.02.1.01/0.0/0.0/16_013/0001818), funded by the Operational Programme Research, Development and Education.Peer reviewe