Characterization of glycine rich proteins from the salivary glands of the lone star tick Amblyomma americanum

Ticks are blood sucking arthropods that feed on living hosts for up to three weeks. The ticks secrete a multitude of pharmacologically active proteins into the host during feeding which allow the tick to avoid the host immune response, establish a blood pool, and form a firm attachment. The firm attachment is facilitated by the formation of a cement cone which surrounds the tick mouthparts and intertwine between the host skin layers. In this study, gene expression of 44 A. americanum genes was measured throughout the bloodmeal to reveal the differential expression of these genes. Each of the genes tested exhibits a differential expression; however, at least one gene of each family is expressed throughout feeding. To further study the tick cement cones, an in vitro feeding system was developed which feeds nymph and adult ticks through a silicone membrane for an extended period of time better mimicking in vivo feeding than other in vitro methods. This allows the cement cone to form with no interference from skin host and hair. The cement cones were then collected and structurally compared to in vivo fed cement cones. Structural differences were identified; however, in vitro feeding allows for cone collection much earlier in the feeding process. A GRP was identified from both in vivo and in vitro fed cones, and a subset of GRPs were studied using RNA interference. The GRPs studied did not have any role in cement cone formation; however, there was significant change in microbial presence in the salivary glands. Inconsistent gene expression data in knock down ticks led to identification of differential expression during the stress response.