Molecular cloning of Ra-sHSPI, a novel member of the HSP20 family from Rhipicephalus annulatus salivary glands

Infestation of cattle by ticks of Rhipicephalus spp. results in severe veterinary and economical losses. Identification of novel proteins from tick salivary glands will enhance our understanding of several aspects of tick physiology and will aid in the development of anti-tick vaccines. Small heat shock proteins (HSPs) have important roles in infection and immunity, especially between invertebrate vectors and mammalian hosts while initially performing their molecular chaperone activity. Here, we report the identification of a small HSP gene from the salivary glands of Rhipicephalus annulatus ticks through immunoscreening of the corresponding cDNA expression library. The identified cDNA contained a 742 bp sequence with 543 bp open reading frame. It was subsequently cloned, expressed and successfully purified under both native and denaturing conditions. Sequence analysis and functional investigations showed that the protein belongs to the HSP20 family, hence the annotated name Ra-sHSPI. Indeed, recombinant Ra-sHSPI showed two typical in vitro activities of holdase chaperones, including thermal protection of bacterial cellular extracts and the recombinant HindIII at elevated temperatures. Moreover, the recombinant Ra-sHSPI showed strong immunogenic effect in animal model. These results pave the way toward further investigation of Ra-sHSPI role in ticks feeding and its potential use as protective antigen.