We have demonstrated that the 80 kDa POP Tc80 (prolyl oligopeptidase of Trypanosoma cruzi) is involved in the process of cell invasion, since specific inhibitors block parasite entry into non-phagocytic mammalian host cells. In contrast with other POPs, POP Tc80 is capable of hydrolysing large substrates, such as fibronectin and native collagen. In this study, we present the cloning of the POPTc80 gene, whose deduced amino acid sequence shares considerable identity with other members of the POP family, mainly within its C-terminal portion that forms the catalytic domain. Southern-blot analysis indicated that POPTc80 is present as a single copy in the genome of the parasite. These results are consistent with mapping of POPTc80 to a single chromosome. The active recombinant protein (rPOP Tc80) displayed kinetic properties comparable with those of the native enzyme. Novel inhibitors were assayed with rPOP Tc80, and the most efficient ones presented values of inhibition coefficient K_i≤1.52 nM. Infective parasites treated with these specific POP Tc80 inhibitors attached to the surface of mammalian host cells, but were incapable of infecting them. Structural modelling of POP Tc80, based on the crystallized porcine POP, suggested that POP Tc80 is composed of an α/β-hydrolase domain containing the catalytic triad Ser⁵⁴⁸–Asp⁶³¹–His⁶⁶⁷ and a seven-bladed β-propeller non-catalytic domain. Docking analysis suggests that triple-helical collagen access to the catalytic site of POP Tc80 occurs in the vicinity of the interface between the two domains.

Lutzomyia evansi, a phlebotomine insect endemic to Colombia’s Caribbean coast, is considered to be the main vector of visceral and cutaneous leishmaniasis in the region. Although insects of this species can harbor pathogenic and non-pathogenic microorganisms in their intestinal microbiota, there is little information available about the diversity of gut bacteria present in Lutzomyia evansi. In this study, conventional microbiological methods and molecular tools were used to assess the composition of bacterial communities associated with Lutzomyia evansi guts in immature and adult stages of natural populations from the department of Sucre (Caribbean coast of Colombia). Sand flies were collected from two locations (peri-urban and jungle biotype) in the Department of Sucre (Caribbean coast of Colombia). A total of 752 Lutzomyia evansi intestines were dissected. In this study, 125 bacterial strains were isolated from different culture media (LB Agar, MacConkey Agar). Different methods were used for bacterial identification, including ribosomal intergenic spacer analysis (RISA) and analysis of the 16S rRNA and gyrB gene sequences. The genetic profiles of the bacterial populations were generated and temporal temperature gradient gel electrophoresis (TTGE) was used to compare them with total gut DNA. We also used PCR and DNA sequence analysis to determine the presence of Wolbachia endosymbiont bacteria and Leishmania parasites. The culture-dependent technique showed that the dominant intestinal bacteria isolated belong to Acinetobacter, Enterobacter, Pseudomonas, Ochrobactrum, Shinella and Paenibacillus in the larval stage; Lysobacter, Microbacterium, Streptomyces, Bacillus and Rummeliibacillus in the pupal stage; and Staphylococcus, Streptomyces, Brevibacterium, Acinetobacter, Enterobacter and Pantoea in the adult stage. Statistical analysis revealed significant differences between the fingerprint patterns of the PCR-TTGE bands in bacterial communities from immature and adult stages. Additionally, differences were found in bacterial community structure in fed females, unfed females, males and larvae. The intestinal bacteria detected by PCR-TTGE were Enterobacter cloacae and Bacillus thuringiensis, which were present in different life stages of Lu. evansi, and Burkholderia cenocepacia and Bacillus gibsonii, which were detected only in the larval stage. Wolbachia and Leishmania were not detected in gut samples of Lutzomyia evansi. The analyses conducted using microbiological and molecular approaches indicated significant variations in the bacterial communities associated with the gut of Lu. evansi, depending on the developmental stage and food source. We propose that these elements affect microbial diversity in L. evansi guts and may in turn influence pathogen transmission to humans bitten by this insect.

Pathogens depend on peptidase activities to accomplish many physiological processes, including interaction with their hosts, highlighting parasitic peptidases as potential drug targets. In this study, a major leucyl aminopeptidolytic activity was identified in Trypanosoma cruzi, the aetiological agent of Chagas disease.