**4. Conclusions**

Ecotin, a serine peptidase inhibitor (ISP), found first in *E. coli*, is a key factor in bacterial defense against the immunological barriers of vertebrate host organisms. Genomic studies demonstrated that parasites from the Trypanosomatida taxon are unique eukaryotic organisms harboring different ecotin-like encoding genes. Considering existence of trypanosomatida species with bacterial endosymbionts and the genomic context of ISPs demonstrated in this chapter, the evolutive origin of ecotin-like genes in trypanosomatids probably occurred by horizontal transfer from a symbiont bacterium, in a common ancestor of the clade, and this event was followed

*Exploring the Evolutionary Origin and Biological Role of the* Trypanosoma cruzi *Ecotin-Like… DOI: http://dx.doi.org/10.5772/intechopen.109929*

by successive duplications and losses that would explain the current pattern. *T. cruzi* present only one copy of ISP (TcISP) with high structural similarity to ecotin from *E. coli* and a strong inhibitory activity on human neutrophil elastase, indicating an exogenous activity and interaction with vertebrate host serine peptidases involved in the modulation of the immune system. The recombinant TcISP2 protein was immunogenic in a murine model, allowing the detection of antibodies in the chronic phase of *T.cruzi* infection, which suggested that this protein can also be tested as a target for serological diagnosis and for investigation of disease prognosis.
