Adenylate cyclase on Bordetella pertussis attachment to alveolar cells: its interaction with filamentous haemagglutinin

M. L. PÉREZ VIDAKOVICS, D. SERRA, O. YANTORNO Y M. E. RODRÍGUEZ

Puerto Iguazú, Misiones, Argentina

Congreso; XL Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2004

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Bordetella pertussis is the etiological agent of whooping cough, a disease that have been lately increasing all over the world. Understanding the pathogenesis is mandatory to improve prevention strategies. Bacterial adherence to respiratory cells is a crucial step in colonisation. In this study we used alveolar epithelial human cells (A549) to evaluate the role of the main virulence factors on bacterial attachment. Our results showed that solely the lack of either Filamentous Hemagglutinin (FHA) or Adenylate Cyclase toxin (Cya) significantly decrease bacterial attachment rates compared to the wild type strain (80% and 40%, respectively). FHA is a well known adhesin but Cya has never been described involved in bacterial-cell interaction. Adherence assays of wild type bacteria ran in the presence or the absence of anti-FHA antibodies, anti-Cya polyclonal antibodies, or anti-Cya blocking monoclonal antibodies directed against either each or both toxic activities of Cya (adenylate cyclase and haemolitic) suggested that neither Cya has adhesive activity in this system nor any of the toxic activities of Cya are required for efficient interaction with alveolar cells. Recent studies have demonstrated Cya and FHA to be associated on the surface of B. pertussis. The lack of Cya might affect surface associated FHA eventually influencing B. pertussis attachment. Although immunoblot analysis showed the lack of Cya not to prevent FHA localisation in the outer membrane, attachment assays performed in the presence of heparin suggested that the absence of Cya indeed modifies the carbohidrate-binding site of FHA (the site involved in FHA-mediated bacterial binding to epithelial cells) in a way that it is less efficient in mediating bacterial attachment but it is not longer inhibitable by heparin. We propose the presence of Cya in the surface of B. pertussis to play a role in the functionality of FHA as an adhesin. Inasmuch as downregulation of Cya has been reported required for successful host colonisation the change in this binding site of the surface associated FHA might play a role in vivo.