Bordetella pertussis, etiologic agent of whooping cough, has been extensively studied over the past 10-20 years with regard to its toxins and their mechanisms of action, even to the molecular level. Two toxins in particular, pertussis toxin and adenylate cyclase toxin, have been shown to impair the function of immune effector cells, perhaps explaining the mechanism of prolonged infection with B. pertussis and the susceptibility of patients to secondary infection. Since available data do not support the hypothesis the B. pertussis causes intoxication by releasing large quantities of toxin into the environment, it is now essential that the possibility of toxin delivery by direct bacteria-host immune cell interaction by investigated. Preliminary data indicate the B. pertussis bind avidly to human phagocytic cells and rapidly inhibit their immune effector function. The overall goal of this project is to determine how intact B. pertussis evade or disarm polymorphonuclear and mononuclear phagocytes to cause infection and, ultimately, the clinical disease of whooping cough. Virulent and avirulent B. pertussis will be compared for their attachment to, phagocytosis by, and intracellular fate within phagocytes. Then, the effects of intact B. pertussis on leukocyte chemotaxis, phagocytosis and killing of other microbes, oxidative responses to soluble and particulate stimuli, and degranulation and phagolysosome fusion will be evaluated. The mechanisms by which B. pertussis elicit the inhibitory effects on phagocyte function will be addressed by studying: 1) the biochemical consequences of bacteria-host cell interaction (cyclic AMP and GMP levels, ADP-ribosylation of pertussis toxin substrates); 2) the necessity for bacterial viability; 3) the impact on phagocyte ultrastructure; 4) modification of the inhibitory effects by antibodies against B. pertussis and by complement; 5) transposon Tn5 mutants of B. pertussis specifically deficient in known virulence factors. Complete characterization of the interaction between B. pertussis and human polymorphonuclear and mononuclear phagocytes will provide important new insights into the pathophysiology and immunobiology of infection and may result in new approaches to immunoprophylaxis or therapy for pertussis.
