Date of Award

2020-01-01

Degree Name

Doctor of Philosophy

Department

Biological Sciences

Advisor(s)

Igor C. Almeida

Abstract

Triatomines are blood-sucking arthropods that transmit Trypanosoma cruzi, the etiologic agent of Chagas disease (ChD). Triatomines use bioactive molecules in the saliva for successful blood feeding and to evade the hemostatic and immune defense system of the hosts. Knowing the saliva composition could be useful for a better understanding which and how insect-derived molecules might influence host-parasite interactions. Previous studies have shown that some saliva-derived proteins and lipids can modulate the host immune system and increase T. cruzi infection. We hypothesize that the triatomine saliva contains a great diversity of lipids and proteins that can modulate the mammalian host immune response favoring blood-feeding and pathogen transmission. Moreover, these molecules could be used as biomarker of vector bite. Thus, the main purpose of this work is to conduct an omics (proteomic, lipidomic, and metabolomic) analysis on the saliva of different species of triatomines and identify these potential molecules. To address our hypoThesis, we first identified the proteins, lipids, and metabolites (Specific Aim 1), and then tested the immunoreactivity against sera of negative or positive ChD patients (Specific Aim 2). Saliva of two species from North America, Meccus pallidipennis and Triatoma lecticularia, and two from South America, Panstrongylus herreri and Rhodnius prolixus, were obtained by dissection of the triatomine salivary glands. The proteins were digested using a Filter-Aided Sample Prep (FASP) kit. Extracellular vesicles (EVs) were recovered in the triatomine saliva after ultrafiltration. The lipids and metabolites were extracted by Folchâ??s partition. Resulting peptides, lipids and metabolites were analyzed by high-resolution liquid chromatography-tandem mass spectrometry (HR-LC-MS/MS) in a QE-Plus Orbitrap mass spectrometer. Immunoreactivity against sera of negative or positive ChD patients was screened by chemiluminescent enzyme-linked immunosorbent assay (CL-ELISA). Significant qualitative and quantitative differences were observed at protein, lipid, and metabolite levels between the four-triatomine species. No clustering regarding geographical origin was noticed; however, considerable differences were observed regarding the tribes of the four triatomine species analyzed. The most abundant proteins in triatomine saliva belong to the lipocalin group. EVs were found for the first time in the triatomine saliva. Different immunoreactivity against salivary antigens with ChD sera from different countries was found. Eighteen lipid classes were identified in the triatomine saliva, including the lyso-phosphatidylcholine (LPC)-C16:0 previously described. Arachidonic acid (C20:4), the precursor of prostaglandins, and some purines such as adenosine, were also detected. In conclusion, our findings will further our understanding of potential effects of triatomine saliva in the establishment and long-term maintenance of T. cruzi infection within the mammalian host.

Language

en

Provenance

Received from ProQuest

File Size

131 pages

File Format

application/pdf

Rights Holder

Maria Tays Mendes

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