Aedes albopictus D7 Salivary Protein Prevents Host Hemostasis and Inflammation

Abstract

Mosquitoes inject saliva into the host skin to facilitate blood meal acquisition through active compounds that prevent hemostasis. D7 proteins are among the most abundant components of the mosquito saliva and act as scavengers of biogenic amines and eicosanoids. Several members of the D7 family have been characterized at the biochemical level; however, none have been studied thus far in Aedes albopictus, a permissive vector for several arboviruses that causes extensive human morbidity and mortality. Here, we report the binding capabilities of a D7 long form protein from Ae. albopictus (AlboD7L1) by isothermal titration calorimetry and compared its model structure with previously solved D7 structures. The physiological function of AlboD7L1 was demonstrated by ex vivo platelet aggregation and in vivo leukocyte recruitment experiments. AlboD7L1 binds host hemostasis agonists, including biogenic amines, leukotrienes, and the thromboxane A2 analog U-46619. AlboD7L1 protein model predicts binding of biolipids through its N-terminal domain, while the C-terminal domain binds biogenic amines. We demonstrated the biological function of AlboD7L1 as an inhibitor of both platelet aggregation and cell recruitment of neutrophils and eosinophils. Altogether, this study reinforces the physiological relevance of the D7 salivary proteins as anti-hemostatic and anti-inflammatory molecules that help blood feeding in mosquitoes.

Novel salivary antihemostatic activities of long-form D7 proteins from the malaria vector Anopheles gambiae facilitate hematophagy

“…However, at the 3 μM concentration, AngaD7L3 did reduce platelet aggregation when induced by serotonin alone (but not at 1 μM of AngaD7L3). Serotonin alone is not a potent agonist, and while it can induce platelet shape change, the platelets eventually disaggregate ( 22 ). We therefore combined serotonin and collagen to produce a full aggregation response.…”

“…The inhibition of platelet aggregation induced by U-46619 has been reported in other mosquito D7 proteins. AlboD7L1 and CxD7L2 had a low U-46619–induced platelet inhibiting effect because of their low binding affinity to U-46619 ( 22 , 28 ). AnSt-D7L1 and AeD7L2, which both tightly bind U-46619, displayed a strong inhibition effect on platelet aggregation ( 16 , 27 ).…”

“…aegypti AeD7L2, and Culex quinquefasciatus CxD7L2 ( Fig. S6 ) ( 3 , 14 , 16 , 22 , 26 , 27 , 28 ). Ae.…”

“…This function is similar to that of D7s from other mosquito species. AnSt-D7L1, AlboD7L1, CxD7L2, and AeD7L2 also bind U-46619 ( 16 , 22 , 27 , 28 ). Both AeD7L2 and AnSt-D7L1 were also shown to inhibit vascular contraction ( 16 , 27 ).…”

“…This effect has been observed in other nonanopheline mosquito species such as Ae. albopictus AlboD7L1 and C. quinquefasciatus CxD7L2 ( 22 , 28 ). The A. gambiae short-forms D7r1-D7r4 are also known to bind serotonin and likely inhibit platelet aggregation and vasoconstriction ( 3 ).…”