Bordetella pertussis virulence factors.

Bordetella pertussis virulence factors. Bordetella pertussis produces a series of virulence factors that are involv ed in one of several steps of the pathogenesis of whooping cough. By compar ison to other infectious diseases, such as diphtheria or tetanus, pertussis has initially been viewed as a mere toxin-mediated disease in which pertus sis toxin plays the major key role. However, if is now clear that the expre ssion of the disease requires numerous virulence factors that have classica lly been subdivided into adhesins and toxins. The major adhesins are filame ntous haemagglutinin, pertactin and the fimbriae, and the major toxins are pertussis toxin, adenylate cyclase and dermonecrotic toxin, in addition to non-protein toxins, such as tracheal cytotoxin and lipopolysaccharide. In a ddition to their function as individual virulence factors, adhesins and tox ins may also act in synergy to favour efficient B. pertussis infection. Mor e recently, new approaches to the study of virulence, essentially based on genomics, have revealed that the molecular mechanisms of B. pertussis virul ence is far more complex than initially assumed, and that it involves addit ional virulence factors. The production of most, but not all of these facto rs is Under the control of a two-component regulatory system named BvgA/S. This system is able to sense signals from the environment and transmit this information via a phosphorylation cascade to a transcriptional activator. The phosphorylated activator can then, in turn, induce the expression of th e various virulence genes. The precise role of the newly identified virulen ce factors is not yet known, but will undoubtedly be the focus of future st udies. (C) 2001 Editions scientifiques et medicales Elsevier SAS.