Recombinant Expression of a Tick Saliva Serine Protease Inhibitor

Abstract

The Ixodes scapularis tick is a medically important vector of five out of the 15 reportable human tick borne disease agents, making it a great concern to public health. In order to develop vaccines against tick borne disease agents, it is imperative to understand the mechanisms of tick feeding. During feeding, ticks inject saliva containing several proteins into host, including serpins (serine protease inhibitors). Serpins are the largest superfamily of protease inhibitors and are believed to aid the successful transmission of disease agents into a host by allowing ticks to evade host defenses during feeding. Tick serpins inhibit host proteolytic defense pathways like coagulation, inflammation, hemostasis, and much more. In this study, yeast recombinant protein expression constructs of Serpin 1B, was prepared using Pichia pastoris expression system. Large-scale expression of Serpin 1B, purification, and substrate hydrolysis experiments were subsequently performed. This project successfully cloned and expressed Serpin1B using Pichia pastoris expression system. In this study, biochemical characterization showed that rSerpin1B inhibits chymotrypsin by at least 33% and trypsin by 99%.