BmTI-A, a Kunitz type inhibitor from Rhipicephalus microplus able to interfere in vessel formation

• rBmTI-A inhibited vessel formation “in vitro” model by decreasing kinin releasing.
• BmTI-A gene is highly expression in the Rhipicephalus microplus midgut and native protein concentrated in eggs and larvae, these findings suggest that BmTI-A is produced in midgut.
• BmTI-A inhibitory activity for plasmin and neutrophil elastase may has a role in the inhibition of vessel formation.

Rhipicephalus microplus is an ectoparasite responsible for transmissions of babesiosis and anaplasmosis causing large losses to livestock production. To survive R. microplus tick produces several active molecules, such as protease inhibitors. This ectoparasite has been described as a rich source of serine protease inhibitors most of them are Kunitz-BPTI members named BmTIs which have no clear function yet. In the present work, we described the expression and functional characterization of rBmTI-A which showed to be similar to the native BmTI-A, a double-headed Kunitz-BPTI inhibitor, capable to inhibit trypsin, human neutrophil elastase (HNE), human plasma kalikrein (HuPK) and human plasmin. rBmTI-A was able to cause a decrease of HUVEC cell viability. Besides, the rBmTI-A showed to be a potent inhibitor of “in vitro” vessel formation. Our results suggested that BmTI-A may participate in the blood acquisition process interfering in the vessel formation during the tick parasite life stage, around 20 days. In conclusion, BmTI-A is a promising molecule to be used in the drug design and development of new method of R. microplus control.