Trypanosomatid paraites, despite phylogenetically close, elaborated opposite infectious strategies, being intracellular for Leishmania and extracellular for Trypanosoma. Nevertheless these strategies share key elements to survive and adapt to their hosts, such as mechanisms of interaction to modulate macrophage activation in their favor, by manipulating several cellular metabolic pathways. Some excreted/secreted (ES) molecules from parasites and sugar-binding host receptors play a major role in this dialogue. Antigens released from promastigote forms have been identified as potent modulators of the immune system, having a crucial role in promoting the establishment and maintenance of the infection by interfering in the activation of effector mechanisms, such as the microbicidal activity of macrophages and cytokine production. Moreover, interesting studies using released antigens from Leishmania sp. as a model demonstrated their potency to induce host protection and be used for vaccine development against leishmaniasis (CaniLeish®). 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 secretomes of African trypanosomes, and further investigated their secretome expression and its involvement in host-parasite interactions. The molecular identification of differentially expressed trypanosome molecules and their correlation with either the virulence process or pathogenicity define the secretome as a new active biological compartment.