Proteomics Informed by Transcriptomics for a Qualitative and Quantitative Analysis of the Sialoproteome of Ornithodoros Moubata Adult Ticks

Background: The argasid tick Ornithodoros moubata is the main vector in mainland Africa of the African swine fever virus and the spirochete Borrelia duttoni , which causes human relapsing fever. Elimination of O. moubata populations would contribute to the prevention and control of these two severe diseases. The development of anti-tick vaccines is an eco-friendly and sustainable method for the elimination of tick populations. The tick saliva forms part of the tick-host interface and knowing its composition is key for the identification and selection of vaccine candidate antigens. The aim of the present work is to expand the data on the saliva proteome composition of O. moubata adult ticks, particularly of female ticks, since a more in-depth knowledge of the O. moubata sialome will allow identifying and selecting novel salivary antigens as targets for tick vaccines. Methods We have analysed samples of female and male saliva using two different mass spectrometry approaches: data-dependent acquisition LC-MS/MS and sequential window acquisition of all theoretical fragment ion spectra mass spectrometry (SWATH-MS). To maximise the number of protein identifications, a proteomics informed by transcriptomics (PIT) analysis was applied using the O. moubata salivary transcriptomic dataset previously obtained by RNAseq. Results The SWATH-MS proved to be superior to LC-MS/MS in the study of female saliva since it increased by 60% the number of identified proteins, enhanced the reproducibility of the results and provided a quantitative image of the saliva components. As a whole, we have identified 299 non-redundant proteins in the O. moubata saliva and quantified the expression of 165 of them in both male and female saliva, among which 13 were significantly overexpressed in females and 40 in males. These results evidence important quantitative differences between sexes in the saliva proteome. Conclusions This work expand our knowledge of the O. moubata sialome, particularly of female ticks, by increasing the identification of novel salivary proteins and functions at the tick–host feeding interface. The integration of this new knowledge together with the information from the O. moubata sialotranscriptome will allow a more rational selection of the salivary candidates as antigen targets for tick vaccine development.