Trypanosoma simiae and Trypanosoma congolense: surface glycoconjugates of procyclic forms-the same coats on different hangers?

Leptomonas pyrrhocoris: Genomic insight into Parasite's Physiology

BACKGROUND

Leptomonas pyrrhocoris is a parasite of the firebug Pyrrhocoris apterus. This flagellate has been recently proposed as a model species for studying different aspects of the biology of monoxenous trypanosomatids, including host - parasite interactions. During its life cycle L. pyrrhocoris never tightly attaches to the epithelium of the insect gut. In contrast, its dixenous relatives (Leishmania spp.) establish a stable infection via attachment to the intestinal walls of their insect hosts.

MATERIAL AND METHODS

This process is mediated by chemical modifications of the cell surface lipophosphoglycans. In our study we tested whether the inability of L. pyrrhocoris to attach to the firebug's midgut is associated with the absence of these glycoconjugates. We also analyzed evolution of the proteins involved in proper lipophosphoglycan assembly, cell attachment and establishment of a stable infection in L. pyrrhocoris, L. seymouri, and Leishmania spp. Our comparative analysis demonstrated differences in SCG/L/R repertoire between the two parasite subgenera, Leishmania and Viannia, which may be related to distinct life strategies in various Leishmania spp. The genome of L. pyrrhocoris encodes 6 SCG genes, all of which are quite divergent from their orthologs in the genus Leishmania. Using direct probing with an antibody recognizing the β-Gal side chains of lipophosphoglycans, we confirmed that these structures are not synthesized in L. pyrrhocoris.

CONCLUSION

We conclude that either the SCG enzymes are not active in this species (similarly to SCG5/7 in L. major), or they possess a different biochemical activity.

Identification of total and differentially expressed excreted-secreted proteins from Trypanosoma congolense strains exhibiting different virulence and pathogenicity

Animal trypanosomosis is a major constraint to livestock productivity in the tropics and has a significant impact on the life of millions of people globally (mainly in Africa, South America and south-east Asia). In Africa, the disease in livestock is caused mainly by Trypanosoma congolense, Trypanosoma vivax, Trypanosoma evansi and Trypanosoma brucei brucei. The extracellular position of trypanosomes in the bloodstream of their host requires consideration of both the parasite and its naturally excreted-secreted factors (secretome) in the course of pathophysiological processes. We therefore developed and standardised a method to produce purified proteomes and secretomes of African trypanosomes. In this study, two strains of T. congolense exhibiting opposite properties of both virulence and pathogenicity were further investigated through their secretome expression and its involvement in host-parasite interactions. We used a combined proteomic approach (one-dimensional SDS-PAGE and two-dimensional differential in-gel electrophoresis coupled to mass spectrometry) to characterise the whole and differentially expressed protein contents of secretomes. The molecular identification of differentially expressed trypanosome molecules and their correlation with either the virulence process or pathogenicity are discussed with regard to their potential as new diagnostic or therapeutic tools against animal trypanosomosis.

Identification and molecular characterization of a novel stage-specific surface protein of Trypanosoma congolense epimastigotes

The cattle pathogen Trypanosoma congolense expresses life cycle stage-specific surface molecules involved in adaptation to different host and vector environments. Here we report the discovery and molecular characterization of a novel stage-specific GPI-anchored surface glycoprotein that is selectively expressed in the epimastigote (EMF) life cycle stage of T. congolense. Culture supernatants of EMF but not of procyclic culture forms (PCFs) promoted adhesion of PCF parasites in an in vitro assay. Biosynthetic labeling experiments showed that these EMF culture supernatants contained a 100kDa trypanosome-derived protein that was not present in supernatants from PCF. We named this molecule "congolense epimastigote-specific protein" (CESP). The gene encoding CESP was isolated from an EMF cDNA library after immunoscreening. The multicopy gene had a 2070-bp open reading frame that encodes a polypeptide of 689 amino acids with a predicted mass of 72.9kDa. The discrepancy between the predicted (72.9kDa) and observed (100kDa) masses may be explained partially by glycosylation of the molecule which has six potential N-glycosylation sites and a predicted GPI anchor. Indeed, metabolic labeling of CESP with [(3)H] ethanolamine revealed that CESP was a GPI-anchored protein. Confocal laser scanning microscopy showed that CESP was expressed only on the surface of the EMF stage of the parasite. The identification of CESP as a unique component of culture supernatants from EMF and that such supernatants can confer plastic-adhesive ability on PCF suggest that CESP is worth further investigation as an adhesion molecule that perhaps allows T. congolense EMF to adhere to the tsetse proboscis.