The biological and biochemical analysis of a tick-encoded serine protease inhibitor (S6) and its role in the feeding cycle of Amblyomma americanum

Ticks parasitize a wide-range of hosts including companion animals, livestock, and humans. Surpassing all other arthropods in terms of the diverse number of pathogens they vector, ticks are second only to mosquitoes in terms of medical importance. Global costs associated with tick control and treatment of tick-borne diseases (TBD) is estimated to be billions of dollars annually. Suppression of tick vector populations remains the primary method of reducing the impact of TBDs. Tick control has traditionally been accomplished by chemical acaricide application. Unfortunately, their overuse and aggressive application have caused many negative effects, including the increasing prevalence of acaricide-resistant ticks, and environmental and food product contamination. These factors have necessitated the need for the development of safer, more sustainable means of controlling ticks. Among the attempted methods, immunological tick control has shown to be most promising. In order for anti-tick vaccines to be developed, a more thorough understanding of the molecular physiology of the tick feeding cycle is necessary to identify potential target antigens. We are studying the role of a serine protease inhibitor (serpin), S6, in the Lone Star Tick (Amblyomma americanum) as a possible target antigen for an anti-tick vaccine. To assess the viability of S6, the following objectives will be accomplished: correlation of transcript expression patterns with protein production though reverse transcription polymerase chain reaction (RT-PCR) and western blot analysis, functional characterization using a complex formation assay, and evaluation of the ticks’ ability to feed after gene knockdown of S6 using RNA interference (RNAi).