Tick feeding regulation by orthologous tick saliva serine protease inhibitors

Texas A&M University, College Station TX

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Abstract

DESCRIPTION (provided by applicant): In the United States human vector borne diseases are primarily tick borne. The goals of this research are identification, characterization and validation of Amblyomma americanum and Ixodes scapularis tick saliva serine protease inhibitors (serpins) as vaccine target antigens for immunization of white tailed deer against tick infestation. To complete feeding, ticks must overcome host defense reactions, blood coagulation, complement activation and inflammation, all of which are serine protease mediated pathways that are tightly controlled by serpins. Our lab and others have proposed that during feeding, ticks express and inject serpins into the host to regulate evasion of host defense response to tick feeding activity. In an ongoing NIHR03 project in its final year we have screened 10 A. americanum (Aam) tick salivary gland (SG) serpin, and validated that 2 of the serpins (S), AamS6 and AamS8 are secreted into tick saliva, which is proxy for their injection into the host during tick feeding. We have extended these studies and identified 14 blood meal responsive I. scapularis tick SG serpins. In this proposal we will utilize protocols developed in the NIHR03 project to validate secretion of the 14 I. scapularis SG serpins into tick saliva. We have observed that the two A. americanum tick saliva serpins as well as the I. ricinus tick saliva serpin are highly conserved in ticks. Thus, we hypothesize that ticks utilize orthologous tick saliva serpins to regulate tick feeding and that immunologically blocking tick saliva serpin functions will prevent feeding success of multiple tick species. The importance of white tailed deer (Odocoileus virginianus) in the emergence of major human tick borne diseases (TBD) in the United States, Lyme disease, human anaplasmosis, babesiosis and ehrlichiosis and the southern tick-associated rash illness (STARI) has been recognized. Thus data in this proposal will be directly relevant towards efforts to develop novel technologies to prevent human TBD. There are 3 specific aims in this application. The first is to validate secretion of 16 blood meal responsive I. scapularis tick salivary gland serpins into tick saliva. The second is to characterize role(s) of A. americanum and I. scapularis native tick saliva serpins in tick feeding regulation. To validate tick immunity and anamnestic antibody response to tick infestation of white tailed deer immunized with recombinant tick saliva serpin antigens.