The Hookworm Platelet Inhibitor: Functional Blockade of Integrins GPIIb/IIIa (αIIbβ3) and GPIa/IIa (α2β1) Inhibits Platelet Aggregation and Adhesion In Vitro

Hookworms, aggressive, blood-feeding, intestinal nematodes, are currently a leading cause of iron deficiency anemia in the developing world. An inhibitor of platelet aggregation and adhesion has been partially purified and characterized from soluble protein extracts of adult Ancylostoma caninum hookworms. This protein, named the hookworm platelet inhibitor, has an estimated molecular mass of 15 kDa as determined by size-exclusion chromatography. In addition to blocking platelet aggregation in response to a variety of agonists, the partially purified inhibitor also prevents adhesion of resting platelets to immobilized fibrinogen and collagen. Inhibitory monoclonal antibodies were used to identify specific blockade of cell surface integrins GPIIb/IIIa (alphaIIbbeta3) and GPIa/IIa (alpha2beta1), the platelet receptors for fibrinogen and collagen, respectively. This broad-spectrum anti-platelet activity is also present in excretory and secretory products of adult worms, suggesting a biologic role for the hookworm platelet inhibitor in vivo.