Trypanosoma evansi secretome carries potential biomarkers for Surra diagnosis

Extracellular vesicles released by Trypanosoma evansi: induction analysis and proteomics

Trypanosoma evansi is a unicellular protozoan responsible for causing a disease known as "surra," which is found in different regions of the world and primarily affects horses and camels. Few information is known about virulence factors released from the parasite within the animals. The organism can secrete extracellular vesicles (EVs), which transport a variety of molecules, including proteins. Before being considered exclusively as a means for eliminating unwanted substances, extracellular vesicles (EVs) have emerged as key players in intercellular communication, facilitating interactions between cells, host cells, and parasites, and even between parasites themselves. Thus, they may be used as potential biomarkers. This study aimed to assess the induction of EVs production by Ca+2, conduct a proteomic analysis of the EVs released by T. evansi, and identify epitopes that could serve as biomarkers. The findings indicated that Ca+2 is not an effective promoter of vesiculation in T. evansi. Furthermore, the proteomic analysis has identified multiple proteins that have been investigated as biomarkers or vaccine antigens, previously. A total of 442 proteins were identified, with 7 of them specifically recognizing 9 epitopes that are unique to T. evansi. At least one of these epitopes of TevSTIB805.9.11580 have been previously identified, which increases the possibility of further investigating its potential as a biomarker.

Shotgun proteomics of detergent-solubilized proteins from Trypanosoma evansi

Trypanosoma evansi, the causative agent of surra, is the most prevalent pathogenic salivarian trypanosome and affects the majority of domesticated and wild animals in endemic regions. This work aimed to analyze detergent-solubilized T. evansi proteins and identify potential diagnostic biomarkers for surra. Triton X-114-extracted membrane-enriched proteins (MEP) of T. evansi bloodstream forms were analyzed using a gel-free technique (LC-ESI-MS/MS). 247 proteins were identified following the MS analysis of three biological and technical replicates. Two of these proteins were predicted to have a GPI-anchor, 100 (40%) were predicted to have transmembrane domains, and 166 (67%) were predicted to be membrane-bound based on at least one of six features: location (WolfPSORT, DeepLoc-2.0, Protcomp-9.0), transmembrane, GPI, and gene ontology. It was predicted that 76 (30%) of proteins had membrane evidence. Typical membrane proteins for each organelle were identified, among them ISG families (64, 65, and 75 kDa), flagellar calcium-binding protein, 24 kDa calflagin, syntaxins and oligosaccharyltransferase some of which had previously been studied in other trypanosomatids. T. evansi lacks singletons and exclusive orthologous groups, whereas three distinct epitopes have been identified. Data are available via ProteomeXchange with identifier PXD040594. SIGNIFICANCE: Trypanosoma evansi is a highly prevalent parasite that induces a pathological condition known as "surra" in various species of ungulates across five continents. The infection gives rise to symptoms that are not pathognomonic, thereby posing challenges in its diagnosis and leading to substantial economic losses in the livestock industry. A significant challenge arises from the absence of a diagnostic test capable of distinguishing between Trypanosoma equiperdum and T. evansi, both of which are implicated in equine diseases. Therefore, there is a pressing need to conduct research on the biochemistry of the parasite in order to identify proteins that could potentially serve as targets for differential diagnosis or therapeutic interventions.

A Flow Cytometry Study of the Binding and Stimulation Potential of Inactivated Trypanosoma evansi toward Dromedary Camel Leukocytes

Surra, a wasting disease caused by Trypanosoma evansi, is one of the major animal health burdens in camel-rearing countries, imposing significant economic losses due to reduced fertility and high mortality rates. The present study used inactivated T. evansi (from the Card Agglutination Test for Trypanosomes/Trypanosoma evansi; CATT/T. evansi) and flow cytometry to investigate their binding and activation potential toward camel leukocyte subsets. Labeling T. evansi with propidium iodide (PI) enabled their flow cytometric enumeration and identification with forward scatter (FSC; indicative for cell size) and side scatter (SSC; indicative for cell internal complexity) characteristics that are comparable with values reported for Trypanosoma cruzi. The incubation of PI-labeled non-opsonized T. evansi with camel leukocyte populations revealed that camel monocytes have the highest potential to bind T. evansi, followed by granulocytes and lymphocytes. The identification of pattern recognition receptors (PRRs) on camel immune cells and the pathogen-associated molecular patterns (PAMPs) in T. evansi that are responsible for this different binding capacity requires further studies. Stimulation of camel neutrophils with Trypanosoma evansi induced shape change, reactive oxygen species (ROS) production, and neutrophil extracellular traps (NET)-formation. To ensure that T. evansi, in the parasite concentration used in this study, is not apoptotic or necrotic to camel leukocytes, we evaluated cell apoptosis and necrosis after stimulation with T. evansi. The results revealed no impact of T. evansi stimulation for 2 h on the cell viability of camel leukocytes. Subsequent work may focus on the diagnostic employment of labeled T. evansi and flow cytometry for the detection of anti-Trypanosoma antibodies in camel serum. In addition, more efforts should be deployed to investigate the host-pathogen interaction mechanisms and the escape mechanisms of T. evansi in camels. To complete these data, further studies using the living or freshly killed parasites could also be implemented in camels and/or horses.

Validation of in vitro-produced and freeze-dried whole cell lysate antigens for ELISA Trypanosoma evansi antibody detection in camels

Trypanosoma evansi is a blood parasite responsible for surra in mammals, with a high impact in camels and horses. The WOAH-recommended reference method for detecting immunoglobulin G directed against T. evansi is ELISA, using whole cell lysate antigens (WCLAs). WCLAs are prepared with T. evansi produced in laboratory rodents, separated from blood cells using DE-cellulose anion exchange chromatography. As parasite lysates are fragile, antigens are preserved frozen pending use. For these reasons and others, T. evansi WCLAs are not commercially available. They are produced in small quantities, in a limited number of specialized laboratories, and they require a reliable and expensive cold chain for their shipment. In this study, we assessed and validated in vitro production of T. evansi and lyophilization of WCLAs in comparison with the reference method using frozen WCLAs prepared with parasites produced in rodents. Using a set of 400 samples monthly collected from 12 naturally infected camels followed-up for 1384 days, and two batches of referenced serum samples (infected, n = 12; non-infected, n = 15), statistical studies on qualitative and semi-quantitative results of the ELISAs did not show any significant difference when comparing the four combinations of parasites produced in vivo or in vitro, and frozen or freeze-dried WCLSAs. A repeatability study (28 repeats in 9 serum samples) was fully satisfying (p-value = 0.055). With the more convenient in vitro-produced freeze-dried WCLAs it was possible to: (i) avoid the ethical concern of in vivo production, (ii) improve the standardization of antigen production, (iii) secure antigen preservation during shipment and (iv) save a considerable amount of money (DE52-cellulose and dry-ice cold chain being avoided). Additional studies with other Trypanosoma spp are required for further extending ELISA to regional laboratories in enzootic areas, especially in view of the current progress in the "Progressive Control Pathway" (PCP) for trypanosomes in Africa.