Figure 1.

Virulence factors roles in their insect vectors intestine tract. T. brucei: Variant surface glycoprotein (VSGs) released from the membrane are incorporated by the peritrophic matrix, reducing its protective function by interfering with the host cell internal pathways. Following VSG release, the surface coat is replaced by procyclins that may protect the parasite against digestive enzymes and hydrolases in the tsetse fly midgut. Leishmania spp.: Inside the invertebrate vector intestines, lipophosphoglycans (LPGs) and gp63 ensure the parasite adhesion to the midgut epithelial cells and alongside proteophosphoglycans (PPGs), protect the parasite against the action of host digestive enzymes. T. cruzi: The parasite adhesion is performed by glycoinositolphospholipids (GIPLs), cruzipain, trans-sialidases (TS) and the mucin group TcSMUG L. The protection against the digestive enzymes may be performed by gp63 via its metalloprotease activity; TS may be involved in protection from glycolytic enzymes; and the mucin group TcSMUG S may perform roles of protease resistance.