Association of liposome-encapsulated trivalent antimonial with ascorbic acid: an effective and safe strategy in the treatment of experimental visceral leishmaniasis.

BACKGROUND: Visceral leishmaniasis (VL) is a chronic debilitating disease endemic in tropical and subtropical areas, caused by protozoan parasites of the genus Leishmania. Annually, it is estimated the occurrence of 0.2 to 0.4 million new cases of the disease worldwide. Considering the lack of an effective vaccine the afflicted population must rely on both, an accurate diagnosis and successful treatment to combat the disease. Here we propose to evaluate the efficacy of trivalent antimonial encapsulated in conventional liposomes, in association with ascorbic acid, by monitoring its toxicity and efficacy in BALB/c mice infected with Leishmania infantum. METHODOLOGY/PRINCIPAL FINDINGS: Infected mice were subjected to single-dose treatments consisting in the administration of either free or liposome-encapsulated trivalent antimony (SbIII), in association or not with ascorbic acid. Parasite burden was assessed in the liver, spleen and bone marrow using the serial limiting dilution technique. After treatment, tissue alterations were examined by histopathology of liver, heart and kidney and confirmed by serum levels of classic biomarkers. The phenotypic profile of splenocytes was also investigated by flow cytometry. Treatment with liposome-encapsulated SbIII significantly reduced the parasite burden in the liver, spleen and bone marrow. Co-administration of ascorbic acid, with either free SbIII or its liposomal form, did not interfere with its leishmanicidal activity and promoted reduced toxicity particularly to the kidney and liver tissues. CONCLUSIONS/SIGNIFICANCE: Among the evaluated posological regimens treatment of L. infantum-infected mice with liposomal SbIII, in association with ascorbic acid, represented the best alternative as judged by its high leishmanicidal activity and absence of detectable toxic effects. Of particular importance, reduction of parasite burden in the bone marrow attested to the ability of SbIII-carrying liposomes to efficiently reach this body compartment.

Isolation and enzyme bioprospection of endophytic bacteria associated with plants of Brazilian mangrove ecosystem.

The mangrove ecosystem is a coastal tropical biome located in the transition zone between land and sea that is characterized by periodic flooding, which confers unique and specific environmental conditions on this biome. In these ecosystems, the vegetation is dominated by a particular group of plant species that provide a unique environment harboring diverse groups of microorganisms, including the endophytic microorganisms that are the focus of this study. Because of their intimate association with plants, endophytic microorganisms could be explored for biotechnologically significant products, such as enzymes, proteins, antibiotics and others. Here, we isolated endophytic microorganisms from two mangrove species, Rhizophora mangle and Avicennia nitida, that are found in streams in two mangrove systems in Bertioga and Cananéia, Brazil. Bacillus was the most frequently isolated genus, comprising 42% of the species isolated from Cananéia and 28% of the species from Bertioga. However, other common endophytic genera such as Pantoea, Curtobacterium and Enterobacter were also found. After identifying the isolates, the bacterial communities were evaluated for enzyme production. Protease activity was observed in 75% of the isolates, while endoglucanase activity occurred in 62% of the isolates. Bacillus showed the highest activity rates for amylase and esterase and endoglucanase. To our knowledge, this is the first reported diversity analysis performed on endophytic bacteria obtained from the branches of mangrove trees and the first overview of the specific enzymes produced by different bacterial genera. This work contributes to our knowledge of the microorganisms and enzymes present in mangrove ecosystems.

Mixed formulation of conventional and pegylated liposomes as a novel drug delivery strategy for improved treatment of visceral leishmaniasis.

OBJECTIVE: Test the hypothesis that pegylated meglumine antimoniate-containing liposomes (LMA) and their mixture with non-pegylated (conventional) LMA may be more effective than conventional LMA against visceral leishmaniasis (VL), because of wider drug distribution among different mononuclear phagocyte system (MPS) tissues. METHODS: Sb was determined in the blood and MPS tissues after administration of pegylated or conventional LMA intravenously to mongrel dogs naturally infected with Leishmania infantum and Swiss mice. Pegylated and conventional LMA as well as their mixture were evaluated for their antileishmanial efficacy in BALB/c infected with L. infantum through determination of parasite load in liver, spleen and bone marrow. RESULTS: An improved targeting of Sb to the bone marrow of dogs was clearly evidenced, as an important impact of pegylation. In accordance with this data, pegylated LMA significantly reduced parasite load in bone marrow of infected mice, in contrast to conventional LMA. The mixed formulation of conventional and pegylated LMA promoted parasite suppression to a higher extent in both spleen and bone marrow, compared to pegylated or conventional LMA. CONCLUSIONS: The present work establishes for the first time the potential of mixed formulations of conventional and pegylated liposomes as a drug delivery strategy for improved treatment of VL.

Association of water extract of green propolis and liposomal meglumine antimoniate in the treatment of experimental visceral leishmaniasis.

This work investigated the use of water extract of green propolis (WEP) and its association with free or liposomal meglumine antimoniate (MA) for the treatment of murine visceral leishmaniasis. Mice infected with Leishmania infantum were treated with oral doses of WEP associated or not with a single dose of liposomal MA by intraperitoneal route. Parasite burden was assessed in the liver and spleen by limiting dilution assay, and alterations in the spleen cellular phenotype were evaluated by flow cytometry. Tissue damage was assessed by determination of biochemical markers of the liver, heart, and kidney function and histopathological analysis of the liver and spleen. Our data showed that treatment with WEP was able to reduce parasite load in the liver but not in the spleen. On the other hand, liposomal MA reduced parasite load in both organs. Unexpectedly, there was no synergism with the combination of WEP and liposomal MA in reducing the parasite load. The histopathological analysis showed that administration of WEP, liposomal MA, or their association was able to protect the liver and spleen from lesions caused by infection. No alteration in the profile of spleen cells by flow cytometry or in the liver, heart, and kidney functions by biochemical markers due to any of the treatments was observed. These results demonstrate that although WEP was able to significantly reduce the liver parasite load, its association with liposomal MA did not lead to significant improvement in reducing parasite load. On the other hand, treatment with WEP and/or liposomal MA protected the liver and spleen from lesions caused by the infection.