Determination of the differential proteome and lipidome of Amblyomma aureolatum ticks in response to Rickettsia rickettsii infection

Abstract

Rock Mountain Spotted Fever, known in Brazil as Brazilian Spotted Fever (BSF), is the most severe rickettsiosis that affects humans. The etiologic agent of BSF, the obligate intracellular bacterium Rickettsia rickettsii, is transmitted by bite of different tick species. In Brazil, the ticks Amblyomma cajennense and A. aureolatum are the two major vectors. Besides the low prevalence of infected ticks from BSF endemic areas, experimentally infected ticks present lower reproductive and survival rates. These data suggest that the bacterium is also detrimental to its vector ticks. With the aim of elucidating the molecular mechanisms of R. rickettsii pathogenicity against its vectors, we determined the effects of an infection on the gene expression profile of A. aureolatum and A. cajennense. We observed the induction of one antimicrobial peptide (hebraein), proteins with serine protease inhibidor domain (Kunitz-type), secreted proteins, and mitochondrial proteins in the salivary glands of both tick species. The central aim of the present study is to determine if the gene expression modulation observed reflects in alterations of protein concentrations in salivary glands of infected ticks. To that end, we will use a proteomic approach. In addition, we intend to identify proteins and lipids that are differentially secreted in infected tick saliva. Therefore, the specifc objectives of the present study are to determine, using mass spectrometry (MS): (i) the proteome (set of proteins) of salivary glands and (ii) the proteome and lipidome (set of lipids) of saliva of A. aureolatum infected or not with R. rickettsii. Some of the proteins and lipds identified by MS will be then selected for the determination of their specific role in acquisition and transmission of the bacterium. (AU)