Role of Tick Metalloprotease Inhibitors in the Transmission of Borrelia burgdorferi

Project summary. This project aims to characterize the previously unstudied roles of tick inhibitors of metalloproteases, a class of proteases requiring metal cofactors, in the transmission of the Lyme disease agent by blacklegged nymphal ticks. This goal is based on evidence that these proteases are among the largest class of innate immunity effector proteases in the skin, which ticks must block to feed and transmit tick-borne disease agents. Preliminary findings demonstrate that these candidate proteins are functional and that their mRNA expression significantly increases in blacklegged ticks infected with the Lyme disease agent, suggesting that these proteins may play roles in the transmission of the disease. The overarching hypothesis is that ticks inject these candidate proteins to suppress the functions of metalloproteases, allowing them to complete feeding and transmit tick-borne disease agents. This hypothesis will be tested in two specific aims, starting with unveiling the protease inhibition profiles of putative tick inhibitors of metalloproteases in skin and plasma using protein-to- protein interaction assays to identify key anti-tick innate immunity proteins that are blocked by candidate proteins. The second specific aim will involve elucidating the roles of tick inhibitors of metalloproteases in Lyme disease agent transmission using RNA interference technology in a mouse model to knock down the target protein's mRNA. Successful completion of this project will provide novel insights into how blacklegged nymphal ticks utilize tick inhibitors of metalloproteases to evade skin immunity and lay the groundwork for the development of a tick- antigen-based vaccine to prevent Lyme disease. This application responds to notices of special interest related to immune responses to arthropod feeding (NOT-AI-21-059) and advancing research for tick-borne diseases (NOT-AI-23-013).