Bordetella pertussis infection: Pathogenesis, diagnosis, management, and the role of protective immunity

Whooping cough is presently one of the ten most common causes of death from infectious disease worldwide. Despite a high vaccine uptake, resurgences o f this disease have been observed in several countries. Virulence factors o f Bordetella pertussis include agglutinogens, fimbriae, P.69/pertactin, per tussis toxin, filamentous haemagglutinin, adenylate cyclase, tracheal cytot oxin, dermonecrotic toxin, lipopoly-saccharide, tracheal colonisation facto r, serum resistance factor, and type III secretion. Virulence factor expres sion is regulated by the bvgAS locus, a two-component signal transduction s ystem. The pathophysiologic sequence consists of attachment (fimbriae, P.69 /pertactin, tracheal colonisation factor, pertussis toxin, filamentous haem agglutinin), evasion of host defence (adenylate cyclase, pertussis toxin, s erum resistance factor), local effects (tracheal cytotoxin), and systemic e ffects (pertussis toxin). Bordetella pertussis is transmitted by respirator y droplets and causes disease only in humans. Various diagnostic methods ar e available, including culture, serological methods, and the polymerase cha in reaction. Serotyping of isolates to detect agglutinogens 2 and 3 is usef ul because serotype 1,2 may be associated with higher mortality, and antibo dies to these antigens (agglutinins) may be protective in both animals and humans. Immunisation using whole-cell vaccine is effective but is reactogen ic. Acellular vaccines containing one to five components are being used inc reasingly in various countries. Protective immunity to pertussis correlates with high levels of antibody to each of pertactin, fimbriae, and pertussis toxin; however, doubt remains as to the relationship between agglutinogen 3 and fimbria 3, making results of trials investigating these virulence fac tors difficult to interpret.