Filamentous hemagglutinin adhesin (FHA)

Filamentous hemagglutinin adhesin (FHA) is a large (~230–240 kDa), filamentous surface-exposed and secreted protein produced by Bordetella pertussis, the causative agent of whooping cough. It serves as the major adhesin facilitating bacterial attachment to ciliated epithelial cells of the human respiratory tract and plays an essential role in colonization and pathogenesis. FHA contains multiple binding domains capable of interacting with various host cell receptors, contributing both to adherence and immunomodulatory activities. Structurally, it features tandem β-helical repeats forming an elongated shaft with globular domains at one end; its N-terminal region includes a conserved TPS domain critical for secretion via the two-partner secretion pathway (TpsA/TpsB system)[1][2][4]. FHA is also involved in biofilm formation and can modulate host immune responses during infection[3][8]. While not targeted by small-molecule drugs, it is an important protective antigen included in acellular pertussis vaccines due to its immunogenicity and central role in virulence[9]. No approved drugs directly target FHA as a therapeutic mechanism. As a vaccine antigen, its mechanism of action is to elicit an immune response that neutralizes bacterial adherence. FHA-specific antibodies may be used to monitor immune response after vaccination or infection, but they are not standard clinical biomarkers for patient selection. There are no specific safety concerns related to targeting this molecule directly; as a vaccine component, general vaccine-related adverse effects apply.

Other names

FHAFilamentous haemagglutininBordetella pertussis filamentous hemagglutininFhaB (gene/protein precursor)