Anopheline anti-platelet protein from a malaria vector mosquito has anti-thrombotic effects in vivo without compromising hemostasis

IntroductionThe saliva of blood-feeding animals (e.g., mosquitoes, ticks, bats) has pharmacological activities that facilitate efficient blood-sucking. We previously identified a unique anti-platelet protein, anopheline anti-platelet protein (AAPP), from the salivary gland of female Anopheles stephensi (human malaria vector mosquito). AAPP specifically blocks platelet adhesion to collagen by binding directly to collagen and subsequently aggregating platelets. To examine the potential of AAPP as a therapeutic agent, we investigated the in vivo anti-thrombotic effects of AAPP.Materials and MethodsEffects of AAPP on whole blood/platelet aggregation in mice were examined. AAPP was also challenged in an established model of pulmonary thromboembolism in mice. We simultaneously investigated the side-effects of the protein (prolongation of bleeding time and coagulation time). Aspirin was used as a positive control for comparison of anti-thrombotic effects.Results and ConclusionsAAPP inhibited whole blood aggregation induced by collagen at 10 mg/kg body weight. AAPP prevented pulmonary death at a lower dose (3 mg/kg) without prolongation of bleeding time compared with aspirin (100 mg/kg) that compromised hemostasis. AAPP and aspirin did not affect coagulation time. These results indicate that AAPP has great potential as a new anti-platelet agent with a better risk/benefit ratio than that seen with aspirin (the most widely used anti-platelet agent).