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Glucantime (SbV) is the first-line treatment against American Tegumentary Leishmaniasis. Resistance cases to this drug have been reported and related to host characteristics and parasite phenotypes. In this study, 12 Leishmania (Viannia) braziliensis isolates from patients that presented clinical cure (Responders—R) and relapse or therapeutic failure (Non-responders—NR) after treatment with antimony, were analyzed. These parasites were assessed by in vitro susceptibility to SbIII and SbV, serine proteases activity measured with substrate (z-FR-AMC) and specific inhibitors (TLCK, AEBSF and PMSF). In vitro susceptibility of axenic amastigotes to SbIII showed a significant difference between R and NR groups. The protease assays showed that TLCK inhibited almost 100% of activity in both axenic amastigotes and promastigotes while AEBSF inhibited around 70%, and PMSF showed lower inhibition of some isolates. Principal component and clustering analysis performed with these data yielded one homogeneous cluster with only NR isolates and three heterogeneous clusters with R and NR isolates. Additionally, differential expression of subtilisins (LbrM.13.0860 and LbrM.28.2570) and TXNPx (LbrM.15.1080) was evaluated in promastigotes and axenic amastigotes from both groups. The results showed a higher expression of LbrM.13.0860 and LbrM.15.1080 genes in axenic amastigotes, while LbrM.28.2570 gene had the lowest expression in all isolates, regardless of the parasite form. The data presented here show a phenotypic heterogeneity among the parasites, suggesting that exploration of in vitro phenotypes based on SbIII and serine proteases profiles can aid in the characterization of L. (V.) braziliensis clinical isolates.

Proteases are virulence factors with a recognized impact on the Leishmania spp. life cycle. This study considers a set of analyses measuring phenotypic factors of L. (V.) braziliensis clinical isolates as promastigotes growth curves, murine peritoneal macrophages infection, inflammatory mediators production, and serine proteases gene expression (subtilisin 13: S13, subtilisin 28: S28, oligopeptidase B: OPB) assessing these isolates’ fitness on in vitro conditions. Parasites had different behavior during the early growth phase from day zero to day three, and all isolates reached the stationary growth phase between days four and seven. Macrophages infection showed two tendencies, one of decreased infection rate and number of parasites per macrophage (Infection Index <1000) and another with a constant infection index (≥1400). TNF-α (≥10 pg/mL) detected in infections by 75% of isolates, IL-6 (≥80 pg/mL) by 30% of isolates and low levels of NO (≥0.01µM) in almost all infections. Gene expression showed higher values of S13 (≥2RQ) in the intracellular amastigotes of all the isolates evaluated. On the contrary, S28 expression was low (≤1RQ) in all isolates. OPB expression was different between promastigotes and intracellular amastigotes, being significantly higher (≥2RQ) in the latter form of 58% of the isolates. Predictive structural assays of S13 and OPB were performed to explore temperature influence on gene expression and the encoded proteases. Gene expression data is discussed based on in silico predictions of regulatory regions that show plasticity in the linearity index of secondary structures of S13 and OPB 3’-untranslated regions of mRNA, dependent on temperature changes. While hairpin structures suggest an active region of mRNA for both genes above 26°C, pseudoknot structure found in S13 is an indication of a particular profile of this gene at mammalian host temperatures (37°C). Furthermore, the predicted 3D structures are in accordance with the influence of these temperatures on the catalytic site stability of both enzymes, favoring their action over peptide substrates. Data gathered here suggest that L. (V.) braziliensis serine proteases can be influenced by the temperature conditions affecting parasite fitness throughout its life cycle.

Glucantime® (SbV) is the first-line treatment against leishmaniasis in South America. Its effectiveness has been associated with modulation of the parasite detoxification system that, in turn, is related to serine proteases such as subtilisins. In this study, 12 Leishmania (Viannia) braziliensis isolates from patients that presented clinical cure (Responders - R) and relapse or therapeutic failure (Non-responders - NR) were used. The parasites were assessed by in vitro susceptibility to SbIII and SbV, serine proteases activity – measured with z-FR-AMC as substrate and specific inhibitors – and expression of subtilisins and tryparedoxin-peroxidase (TXNPx). In vitro susceptibility of axenic amastigotes to SbIII showed a significant difference between R and NR groups. TLCK inhibited almost 100 % of activity in both axenic amastigotes and promastigotes while AEBSF inhibited around 70 %, and PMSF showed lower inhibition of specific isolates. Principal component and clustering analysis yielded one homogeneous cluster with only NR isolates and three heterogeneous clusters with R and NR isolates. Additionally, transcripts of subtilisins (LbrM.13.0860 and LbrM.28.2570) and TXNPx (LbrM.15.1080) were detected in promastigotes and axenic amastigotes from both groups. The data presented here show a phenotypic heterogeneity among the parasites, suggesting that exploration of in vitro phenotypes based on SbIII and serine proteases profiles can aid in the characterization of L. (V.) braziliensis clinical isolates.

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BACKGROUND Leishmania parasites carry a double-stranded RNA virus (Leishmania RNA virus -LRV) that has been divided in LRV1 and LRV2.OBJECTIVES Leishmania (Viannia) braziliensis clinical isolates were assessed in order to determine LRV presence.METHODS Two-round polymerase chain reaction (PCR and nested PCR) was performed to detect LRV1 or LRV2 in L. (V.) braziliensis clinical isolates (n = 12). FINDINGS LRV1 was detected in three clinical isolates which was phylogenetically related to other sequences reported from other American tegumentary leishmaniasis (ATL) endemic areas of Brazil. Patients infected with L. (V.) braziliensis LRVnegative showed only cutaneous lesions while LRV-positive reported different manifestations.MAIN CONCLUSION Data presented here show for the first time that LRV1 is circulating in L. (V.) braziliensis clinical isolates from Rio de Janeiro State in Brazil.

Background: Glucantime® (SbV) is considered the first-line treatment against American Tegumentary Leishmaniasis in South America, though increased parasite resistance towards it have been reported and hampered its effectiveness. In this context, subtilisins serine proteases have been related to parasites’ susceptibility to drugs such as SbV and derivatives, through modulation of the parasite detoxification system. However, little is known about parasites causing ATL and their distinct responses towards this treatment.Methods: The study was conducted using Leishmania (Viannia) braziliensis clinical isolates from patients that presented clinical cure or Responders (R) and relapse/therapeutic failure or Non-responders (NR). Twelve clinical isolates were used to assess their in vitro susceptibility to SbIII and SbV, serine proteases activity, and expression of subtilisins-like and tryparedoxin-peroxidase (TXNPx) transcripts. Results: SbIII was able to better distinguish axenic amastigotes from each clinical group. These isolates were also assessed for serine protease activity, using z-FR-AMC as substrate and detecting distinct enzyme profiles with specific inhibitors. TLCK inhibited almost 100% of activity in both promastigotes and axenic amastigotes while AEBSF inhibited around 70%. PMSF showed low inhibition of specific isolates (35%). Gathering all the quantitative data, we performed principal component analysis and then used the K-means algorithm to cluster the isolates. This analysis yielded one cluster with only one isolate (R isolate), one homogeneous cluster (NR isolates), and three heterogeneous clusters (R and NR isolates). Additionally, gene transcripts of subtilisins and TXNPx were detected in promastigotes and axenic amastigotes from both groups. Conclusions: Cluster analysis showed that there is a phenotypic heterogeneity among the isolates, however, exploration of in vitro phenotypes based on SbIII and serine proteases profiles can aid in the characterization and better understanding of L. (V.) braziliensis clinical isolates.