F2 and pertussis: Continued research has revealed a more complex picture of pertussis pathogenesis and virulence factors [25,26] and adhesins such as fimbrial hemagglutinin (FHA), and fimbrial proteins 2/3 (Fim 2/3), and the autotransporter pertactin (Prn) have been included in acellular vaccines, yet PT remains central in disease and immunity.