The Impact of Two Purified Forms of B. Pertussis CyaA on Oxidative Burst

Background: Adenylate cyclase toxin (CyaA) is an important virulence factor of Bordetella pertussis, the causative agent of whooping cough, and a potential component of acellular pertussis vaccine. Objectives: In the present study the impact of invasive CyaA on oxidative activities of phagocytes was compared with the other form of this molecule to investigate the activity of different parts of molecules on leukocytes. Materials and Methods: The work involved the production of two purified forms of CyaA with different enzymic and invasive properties. They were: the native enzymatically-active, invasive toxin (CyaA), an invasive derivative lacking AC enzymic activity (CyaA*). Different concentrations of CyaA and CyaA* were used to investigate dose-dependent effects of the toxins on oxidative burst in U937 human monoblastic cells, J774.2 mouse macrophage-like cells and fresh human granulocyte cells by Burst Test assay. Results: Significant effects were observed with 0.2 µg protein/mL of CyaA. For instance, there was almost complete (80%) inhibition of phagocytosis by J774.2 cells and 70% inhibition of phagocotosis by human granulocyte cells. The results showed that production of the oxidative burst was significantly impaired by increasing concentrations of CyaA compared to cells treated with PBS. However, there was no significant effect with CyaA* on either cells. Conclusions: The results of the study showed that both enzymatic and invasive functions were required for the oxidative burst effects of adenylate cyclase toxin in leukocytes.