Interaction of Trypanosoma evansi with the plasminogen-plasmin system

- T. evansi binds plasminogen and plasmin on the plasmatic membrane surface.
- The binding of plasminogen and plasmin on the surface of T. evansi is mediated by receptors high and low affinity.
- Several proteins with molecular masses between ∼18 and ∼70 kDa are responsible for plamin/plasminogen binding.
- This parasite-plasminogen interaction may be important in the establishment of the infection in the vertebrate host.

Trypanosoma evansi is a widely-distributed haemoflagellated parasite of veterinary importance that infects a variety of mammals including horses, mules, camels, buffalos, cattle and deer. It is the causal agent of a trypanosomiasis known as Surra which produces epidemics of great economic importance in Africa, Asia and South America. The main pathology includes an enlarged spleen with hypertrophy of lymphoid follicles, congested lungs, neuronal degeneration and meningoencephalitis, where migration of the parasites from the blood to the tissues is essential. Most cells, including pathogenic cells, use diverse strategies for tissue invasion, such as the expression of surface receptors to bind plasminogen or plasmin. In this work, we show that T. evansi is able to bind plasminogen and plasmin on its surface. The analysis of this binding revealed a high affinity dissociation constant (Kd of 0.080 ± 0.009 μM) and 1 × 105 plasminogen binding sites per cell. Also a second population of receptors with a Kd of 0.255 ± 0.070 μM and 3.2 × 104 plasminogen binding sites per cell was determined. Several proteins with molecular masses between ∼18 and ∼70 kDa are responsible for this binding. This parasite-plasminogen interaction may be important in the establishment of the infection in the vertebrate host, where the physiological concentration of available plasminogen is around 2 μM.