An Inhibitor of Thrombin-Stimulated Blood Platelet Aggregation from the Salivary Glands of the Hard Tick Amblyomma variegatum (Acari: Ixodidae)

Abstract

The tropical bont tick, Amblyomma variegatum can cause intense skin irritation and inflammation and bites that often develop into septic wounds or abscess in their host. Crude salivary gland extract (SGE) of partially engorged A. variegatum females as well as SGE protein fractions purified by three-step reverse phase HPLC procedure were tested for their anti-aggregatory effect on isolated human blood platelets stimulated with thrombin and compared with the effect of recombinant hirudin. At concentrations 10(-3) and 5 x 10(-3) microg protein/ml the following rank order of antiplatelet activity was detected: AV 16/3 (inhibitor purified from AV-III, third purification) > SGE > AV-II (fraction from first purification) > AV-III (fraction from first purification) > hirudin. The effect of all fractions tested was dose-dependent. For fraction AV 16/3, the inhibitory effect was 49 and 61% for 10(-3) and 5 x 10(-3) microg protein/ml, respectively. The results suggest that protein fractions from A. variegatum SGE possess an antithrombin effect on human blood platelets with hirudin-like activity.

Characterization of anti-hemostatic factors in the argasid, Argas monolakensis: Implications for the evolution of blood-feeding in the soft tick family

“…In the present study, we show that monobin, a thrombin inhibitor from Argas ticks are orthologous to ornithodorin and savignin. In contrast, a variety of nonorthologous thrombin inhibitors have been identified in hard ticks (Horn et al, 2000;Ibrahim et al, 2001;Kazimirova et al, 2002;Iwanaga et al, 2003;Lai et al, 2004;Imamura et al, 2005;Ciprandi et al, 2006;Nakajima et al, 2006). Similarly, the monogrins described in this study is orthologous to the platelet aggregation inhibitors that target GPIIbIIIa, savignygrin and disagregin described for the genus Ornithodoros (Karczewski et al, 1994;Mans et al, 2002c).…”

Protective immunity against Ixodes ricinus induced by a salivary serpin

“…Therefore, it is particular interesting to use serpins as anti-tick vaccine antigens because different members of this family of proteins are key regulators of either arthropod metabolism and/or host haemostasis. In addition, promising results have been reported using as vaccinating proteins serpins from other hard ticks A. hebraeum, A. variegatum, B. microplus, H. longicornis, and R. appendiculatus [16,[21][22][23] in their respective infestation models.…”

“…Exogenous serpins could therefore interfere at the bite site with the regular immune, inflammatory and coagulation reactions from the host. Serpins have been recently isolated from the hard ticks Amblyomma hebraeum, Amblyomma variegatum, B. microplus, Haemaphysalis longicornis, Ixodes scapularis, and Rhipicephalus appendiculatus [16,[21][22][23]]. An example of the action of tick serpins on the host defence mechanisms is the protein HLS2 from H. longicornis which delays coagulation time and inhibits thrombin activity [16].…”

Variegin, a Novel Fast and Tight Binding Thrombin Inhibitor from the Tropical Bont Tick

“…Salivary Gland Extracts and Estimation of Protein Concentrations-The extraction procedure of A. variegatum SGE and estimation of protein concentrations during fractionation were described previously (23). Briefly, adult female ticks that had been feeding on laboratory rabbits for 9 days (partially fed) were removed and mounted in Petri dishes dorsal side down, and their salivary glands were dissected out into 150 mM NaCl and stored at Ϫ70°C.…”