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Chagas' disease is a neglected infectious illness, caused by the protozoan Trypanosoma cruzi. It remains a challenging health issue in Latin America, where it is endemic, and so far there is no immunoprophylatic vaccine or satisfactory chemotherapic treatment for its chronic stage. The present work addressed the analysis of the plasma membrane (PM) subproteome from T. cruzi human-hosted life stages, trypomastigote and axenic amastigote, by two complementary PM protein enrichment techniques followed by identification using an LC-MS/MS approach. The results revealed an extensive repertoire of proteins in the PM subproteomes, including enzymes that might be suitable candidates for drug intervention. The comparison of the cell surface proteome among the life forms revealed some potentially stage-specific enzymes, although the majority was shared by both stages. Bioinformatic analysis showed that the vast majority of the identified proteins are membrane-derived and/or possess predicted transmembrane domains. They are mainly involved in host cell infection, protein adhesion, cell signaling, and the modulation of mammalian host immune response. Several virulence factors and proteins potentially capable of acting at a number of metabolic pathways of the host and also to regulate cell differentiation of the parasite itself were also found.

Dipetalogaster maxima is a blood-sucking Hemiptera that inhabits sylvatic areas in Mexico. It usually takes its blood meal from lizards, but following human population growth, it invaded suburban areas, feeding also on humans and domestic animals. Hematophagous insect salivary glands produce potent pharmacologic compounds that counteract host hemostasis, including anticlotting, antiplatelet, and vasodilatory molecules. To obtain further insight into the salivary biochemical and pharmacologic complexity of this insect, a cDNA library from its salivary glands was randomly sequenced. Salivary proteins were also submitted to one- and two-dimensional gel electrophoresis (1DE and 2DE) followed by mass spectrometry analysis. We present the analysis of a set of 2728 cDNA sequences, 1375 of which coded for proteins of a putative secretory nature. The saliva 2DE proteome displayed approximately 150 spots. The mass spectrometry analysis revealed mainly lipocalins, pallidipins, antigen 5-like proteins, and apyrases. The redundancy of sequence identification of saliva-secreted proteins suggests that proteins are present in multiple isoforms or derive from gene duplications.

Comparative proteome analysis of developmental stages of the human pathogen Trypanosoma cruzi was carried out by isotope-coded affinity tag technology (ICAT) associated with liquid cromatography-mass spectrometry peptide sequencing (LC-MS/MS). Protein extracts of the protozoan trypomastigote and amastigote stages were labeled with heavy (D8) and light (D0) ICAT reagents and subjected to cation exchange and avidin affinity chromatographies followed by LC-MS/MS analysis. High confidence sequence information and expression levels for 41 T. cruzi polypeptides, including metabolic enzymes, paraflagellar rod components, tubulins, and heat-shock proteins were reported. Twenty-nine proteins displayed similar levels of expression in both forms of the parasite, nine proteins presented higher levels in trypomastigotes, whereas three were more expressed in amastigotes.