Intranasal delivery of LaAg vaccine improves immunity of aged mice against visceral Leishmaniasis

There are no approved vaccines yet for human visceral leishmaniasis (VL), the most severe form of the leishmaniasis clinical manifestations that is fatal in over 95 % of untreated cases. It is well-accepted that immunological changes during aging have deleterious impact on the efficacy of vaccines and response to infections. In this work, we compared the response of young and aged mice to intranasal vaccination with killed Leishmania amazonensis promastigote antigens (LaAg) that were then challenged with L. infantum infection, a species that causes visceral leishmaniasis. Intranasal vaccination with LaAg induced a similar reduction in parasitism and hepatosplenomegaly in both young and aged mice compared to their unvaccinated counterparts. Following infection, there was also a less prominent inflammatory profile particularly in the vaccinated aged group, with lower production of TNF-α and nitrite compared to the respective unvaccinated group. Interestingly, the LaAg intranasal vaccination promoted increased production of IFN-γ that was observed in both young- and aged vaccinated groups. Additionally, CD4+ and CD8+T cells from both vaccinated groups presented decreased expression of the inhibitory receptors PD-1 and KLRG1 compared to their unvaccinated controls. Interestingly, a strong positive correlation was observed between the expression of both inhibitory receptors PD-1 and KLRG1 and parasitism, which was more conspicuous in the unvaccinated-aged mice than in the others. Overall, this study helps define new strategies to improve vaccine effectiveness and provides a perspective for prophylactic alternatives against leishmaniasis.

Synthesis and evaluation of hybrid sulfonamide-chalcones with potential antileishmanial activity

Leishmaniasis is an emerging tropical infectious disease caused by a protozoan parasite of the genus Leishmania. In this work, the molecular hybridization between a trimethoxy chalcone and a sulfonamide group was used to generate a series of sulfonamide-chalcones. A series of eight sulfonamide-chalcone hybrids were made with good yields (up to 95%). These sulfonamide-chalcones were tested against promastigotes of Leishmania amazonensis and cytotoxicity against mouse macrophages, which showed good antileishmanial activity with IC50  = 1.72-3.19 µM. Three of them (10c, 10g, and 10h) were also highly active against intracellular amastigotes and had a good selectivity index (SI > 9). Thus, those three compounds were docked in the cytosolic tryparedoxin peroxidase (cTXNPx) enzyme of the parasite, and molecular dynamics simulations were carried out. This enzyme was selected as a target protein for the sulfonamide-chalcones due to the fact of the anterior report, which identified a strong and stable interaction between the chalcone NAT22 (6) and the cTXNPx. In addition, a prediction of the drug-likeness, and the pharmacokinetic profile of all compounds were made, demonstrating a good profile of those chalcones.

Crosslinked chitosan microparticles as a safe and efficient DNA carrier for intranasal vaccination against cutaneous leishmaniasis

Intranasal (i.n.) vaccination with adjuvant-free plasmid DNA encoding the leishmanial antigen LACK (LACK DNA) has shown to induce protective immunity against both cutaneous and visceral leishmaniasis in rodents. In the present work, we sought to evaluate the safety and effectiveness of d,l-glyceraldehyde cross-linked chitosan microparticles (CCM) as a LACK DNA non-intumescent mucoadhesive delivery system. CCM with 5 μm of diameter was prepared and adsorbed with a maximum of 2.4 % (w/w) of DNA with no volume alteration. Histological analysis of mouse nostrils instilled with LACK DNA / CCM showed microparticles to be not only mucoadherent but also mucopenetrant, inducing no local inflammation. Systemic safeness was confirmed by the observation that two nasal instillations one week apart did not alter the numbers of bronchoalveolar cells or blood eosinophils; did not alter ALT, AST and creatinine serum levels; and did not induce cutaneous hypersensitivity. When challenged in the footpad with Leishmania amazonensis, mice developed significantly lower parasite loads as compared with animals given naked LACK DNA or CCM alone. That was accompanied by increased stimulation of Th1-biased responses, as seen by the higher T-bet / GATA-3 ratio and IFN-γ levels. Together, these results demonstrate that CCM is a safe and effective mucopenetrating carrier that can increase the efficacy of i.n. LACK DNA vaccination against cutaneous leishmaniasis.

Cysteinyl-leukotrienes promote cutaneous Leishmaniasis control

Leishmaniasis is a neglected tropical parasitic disease with few approved medications. Cutaneous leishmaniasis (CL) is the most frequent form, responsible for 0.7 - 1.0 million new cases annually worldwide. Leukotrienes are lipid mediators of inflammation produced in response to cell damage or infection. They are subdivided into leukotriene B4 (LTB₄) and cysteinyl leukotrienes LTC4 and LTD4 (Cys-LTs), depending on the enzyme responsible for their production. Recently, we showed that LTB₄ could be a target for purinergic signaling controlling Leishmania amazonensis infection; however, the importance of Cys-LTs in the resolution of infection remained unknown. Mice infected with L. amazonensis are a model of CL infection and drug screening. We found that Cys-LTs control L. amazonensis infection in susceptible (BALB/c) and resistant (C57BL/6) mouse strains. In vitro, Cys-LTs significantly diminished the L. amazonensis infection index in peritoneal macrophages of BALB/c and C57BL/6 mice. In vivo, intralesional treatment with Cys-LTs reduced the lesion size and parasite loads in the infected footpads of C57BL/6 mice. The anti-leishmanial role of Cys-LTs depended on the purinergic P2X7 receptor, as infected cells lacking the receptor did not produce Cys-LTs in response to ATP. These findings suggest the therapeutic potential of LTB4 and Cys-LTs for CL treatment.

Development of Immunological Assays Based on Leishmania donovani Antigen for Diagnosis of Canine Visceral Leishmaniasis and Their Multicenter Evaluation in Brazil and Italy

Canine visceral leishmaniasis (CVL) due to Leishmania infantum infection is a zoonotic disease prevalent in the areas of South America and the Mediterranean. Infected dogs as reservoirs can contribute to disease transmission and can be a scourge to public health. Therefore, early diagnosis of infected dogs may play a pivotal role in circumscribing disease progression. Invasive tissue aspiration and insufficient serological methods impair a single assay for prompt CVL diagnosis. In the present study, we aimed to evaluate the potential of Leishmania donovani isolated membrane protein, LAg, for the diagnosis of CVL through immunological assays. Initially, enzyme-linked immunosorbent assay was done with Brazilian dog sera to evaluate the performance of LAg in diagnosing CVL and found sensitivity and specificity of 92.50% and 95%, respectively. The study further confirmed the diagnostic efficacy of LAg in a dipstick format. The dipstick test of canine sera from three centers in Brazil and one center in Italy collectively showed sensitivity values in the range of 53.33% to 100% in recognizing symptomatic dogs and specificity values between 75% and 100% to rule out healthy dogs. Moreover, a rapid immunochromatographic test was developed and optimized using LAg. This test was able to identify 94.73% of CVL of Brazilian origin with specificity of 97.29%. The current results highlight the reactive potential of the L. donovani antigen, LAg, for L. infantum CVL diagnosis and support our previous findings, which suggest the utility of LAg for the diagnosis of both L. donovani and L. infantum human VL in a variety of endemic regions. LAg as a diagnostic candidate may be employed to identify comprehensive CVL cases in epidemiological areas.

Immunogenicity of SARS-CoV-2 Trimeric Spike Protein Associated to Poly(I:C) Plus Alum

The SARS-CoV-2 pandemic has had a social and economic impact worldwide, and vaccination is an efficient strategy for diminishing those damages. New adjuvant formulations are required for the high vaccine demands, especially adjuvant formulations that induce a Th1 phenotype. Herein we assess a vaccination strategy using a combination of Alum and polyinosinic:polycytidylic acid [Poly(I:C)] adjuvants plus the SARS-CoV-2 spike protein in a prefusion trimeric conformation by an intradermal (ID) route. We found high levels of IgG anti-spike antibodies in the serum by enzyme linked immunosorbent assay (ELISA) and high neutralizing titers against SARS-CoV-2 in vitro by neutralization assay, after two or three immunizations. By evaluating the production of IgG subtypes, as expected, we found that formulations containing Poly(I:C) induced IgG2a whereas Alum did not. The combination of these two adjuvants induced high levels of both IgG1 and IgG2a. In addition, cellular immune responses of CD4⁺ and CD8⁺ T cells producing interferon-gamma were equivalent, demonstrating that the Alum + Poly(I:C) combination supported a Th1 profile. Based on the high neutralizing titers, we evaluated B cells in the germinal centers, which are specific for receptor-binding domain (RBD) and spike, and observed that more positive B cells were induced upon the Alum + Poly(I:C) combination. Moreover, these B cells produced antibodies against both RBD and non-RBD sites. We also studied the impact of this vaccination preparation [spike protein with Alum + Poly(I:C)] in the lungs of mice challenged with inactivated SARS-CoV-2 virus. We found a production of IgG, but not IgA, and a reduction in neutrophil recruitment in the bronchoalveolar lavage fluid (BALF) of mice, suggesting that our immunization scheme reduced lung inflammation. Altogether, our data suggest that Alum and Poly(I:C) together is a possible adjuvant combination for vaccines against SARS-CoV-2 by the intradermal route.

Targeting chalcone binding sites in living Leishmania using a reversible fluorogenic benzochalcone probe

Chalcones (1,3-diphenyl-2-propen-1-ones) either natural or synthetic have a plethora of biological properties including antileishmanial activities, but their development as drugs is hampered by their largely unknown mechanisms of action. We demonstrate herein that our previously described benzochalcone fluorogenic probe (HAB) could be imaged by fluorescence microscopy in live Leishmania amazonensis promastigotes where it targeted the parasite acidocalcisomes, lysosomes and the mitochondrion. As in the live zebrafish model, HAB formed yellow-emitting fluorescent complexes when associated with biological targets in Leishmania. Further, we used HAB as a reversible probe to study the binding of a portfolio of diverse chalcones and analogues in live promastigotes, using a combination of competitive flow cytometry analysis and cell microscopy. This pharmacological evaluation suggested that the binding of HAB in promastigotes was representative of chalcone pharmacology in Leishmania, with certain exogenous chalcones exhibiting competitive inhibition (ca. 20-30%) towards HAB whereas non-chalconic inhibitors showed weak capacity (ca. 3-5%) to block the probe intracellular binding. However, this methodology was restricted by the strong toxicity of several competing chalcones at high concentration, in conjunction with the limited sensitivity of the HAB fluorophore. This advocates for further optimization of this undirect target detection strategy using pharmacophore-derived reversible fluorescent probes.

Chalcones identify cTXNPx as a potential antileishmanial drug target

With current drug treatments failing due to toxicity, low efficacy and resistance; leishmaniasis is a major global health challenge that desperately needs new validated drug targets. Inspired by activity of the natural chalcone 2’,6’-dihydroxy-4’-methoxychalcone (DMC), the nitro-analogue, 3-nitro-2’,4’,6’- trimethoxychalcone (NAT22, 1c) was identified as potent broad spectrum antileishmanial drug lead. Structural modification provided an alkyne containing chemical probe that labelled a protein within the parasite that was confirmed as cytosolic tryparedoxin peroxidase (cTXNPx). Crucially, labelling is observed in both promastigote and intramacrophage amastigote life forms, with no evidence of host macrophage toxicity. Incubation of the chalcone in the parasite leads to ROS accumulation and parasite death. Deletion of cTXNPx, by CRISPR-Cas9, dramatically impacts upon the parasite phenotype and reduces the antileishmanial activity of the chalcone analogue. Molecular docking studies with a homology model of in-silico cTXNPx suggest that the chalcone is able to bind in the putative active site hindering access to the crucial cysteine residue. Collectively, this work identifies cTXNPx as an important target for antileishmanial chalcones.

Leishmaniasis is an insect vector-borne parasitic disease. With >350 million people world wide considered at risk, 12 million people currently infected and an economic cost that can be estimated in terms of >3.3 million working life years lost, leishmaniasis is a major global health challenge. The disease is of particular importance in Brazil. Current treatment of leishmaniasis is difficult requiring a long, costly course of drug treatment using old drugs with poor safety indications requiring close medical supervision. Moreover, resistance to current antileishmanials is growing, emphasising a major need for new drug targets. In earlier work we had identified a naturally inspired chalcone which had promising antileishmanial activity but with no known mode of action. In this work we use an analogue of this molecule as an activity based probe to identify a protein target of the chalcone. This protein, cTXNPx, has a major role in protecting the parasite against attack by reactive oxygen species in the host cell. By inhibiting this protein the parasite can no longer survive in the host. Collectively this work validates cTXNPx as a drug target with the chalcone as a lead structure for future drug discovery programmes.

Intranasal immunization with chitosan microparticles enhances lack-dna vaccine protection and induces specific long-lasting immunity against visceral leishmaniasis

Development of a protective vaccine against Leishmania depends on antigen formulation and adjuvants that induce specific immunity and long-lasting immune responses. We previously demonstrated that BALB/c mice intranasally vaccinated with a plasmid DNA encoding the p36/LACK leishmanial antigen (LACK-DNA) develop a protective immunity for up to 3 months after vaccination, which was linked with the systemic expression of vaccine mRNA in peripheral organs. In this study, LACK-DNA vaccine was associated with biocompatible chitosan microparticles cross-linked with glyceraldehyde (CMC) to boost the long-lasting immunity against the late L. infantum challenge. Infection at 7 days, 3 or 6 months after vaccination resulted in significantly lower parasite loads when compared with non-vaccinated controls. Besides, LACK-DNA-chitosan vaccinated mice showed long-time protection observed after the late time point challenge. The achieved protection was correlated with an enhanced spleen cell responsiveness to parasite antigens, marked by increased proliferation and IFN-γ as well as decreased IL-10 production. Moreover, we found diminished systemic levels of TNF-α that was compatible with the better health condition observed in LACK-DNA/CMC vaccinated-infected mice. Together, our data indicate the feasibility of chitosan microparticles as a delivery system tool to extend the protective immunity conferred by LACK-DNA vaccine, which may be explored in vaccine formulations against Leishmania parasite infections.

Nanoparticles Loaded with a New Thiourea Derivative: Development and In vitro Evaluation Against Leishmania amazonensis

BACKGROUND

Leishmaniasis is a neglected tropical disease caused by protozoa of the genus Leishmania. Current treatments are restricted to a small number of drugs that display both severe side effects and a potential for parasites to develop resistance. A new N-(3,4-methylenedioxyphenyl)-N'- (2-phenethyl) thiourea compound (thiourea 1) has shown promising in vitro activity against Leishmania amazonensis with an IC₅₀ of 54.14 μM for promastigotes and an IC₅₀ of 70 μM for amastigotes.

OBJECTIVE

To develop a formulation of thiourea 1 as an oral treatment for leishmaniasis, it was incorporated into Nanoparticles (NPs), a proven approach to provide long-acting drug delivery systems.

METHODS

Poly (D,L-Lactic-co-Glycolic Acid) (PLGA) polymeric NPs containing thiourea 1 were obtained through a nanoprecipitation methodology associated with solvent evaporation. The NPs containing thiourea 1 were characterized for Encapsulation Efficiency (EE%), reaction yield (% w/w), surface charge, particle size and morphology by Transmission Electron Microscopy (TEM).

RESULTS

NPs with thiourea 1 showed an improved in vitro leishmanicidal activity with a reduction in its cytotoxicity against macrophages (CC₅₀>100 μg/mL) while preserving its IC₅₀ against intracellular amastigotes (1.46 ± 0.09 μg/mL). This represents a parasite Selectivity Index (SI) of 68.49, which is a marked advancement from the reference drug pentamidine (SI = 30.14).

CONCLUSION

The results suggest that the incorporation into NPs potentiated the therapeutic effect of thiourea 1, most likely by improving the selective delivery of the drug to the phagocytic cells that are targeted for infection by L. amazonensis. This work reinforces the importance of nanotechnology in the acquisition of new therapeutic alternatives for oral treatments.

MPLA and AddaVax® Adjuvants Fail to Promote Intramuscular LaAg Vaccine Protectiveness against Experimental Cutaneous Leishmaniasis

There is so far no vaccine approved for human leishmaniasis, mainly because of the lack of appropriate adjuvants. This study aimed to evaluate in mice the capacity of a mixture of monophosphoryl lipid A (MPLA) and AddaVax^® adjuvants in enhancing the efficacy of a Leishvacin^®-like vaccine comprised of Leishmania amazonensis whole antigens (LaAg). For that, mice were immunized with LaAg plus MPLA/AddaVax^® by the intramuscular route (i.m.) prior to challenge with 2 × 10⁵ and 2 × 10⁶ living parasites. Immunization with LaAg alone reduced the lesion growth of the 2 × 10⁵-challenged mice only in the peak of infection, but that was not accompanied by reduced parasite load, and thus not considered protective. Mice given a 2 × 10⁶ -challenge were not protected by LaAg. The association of LaAg with MPLA/AddaVax^® was able to enhance the cutaneous hypersensitivity response compared with LaAg alone. Despite this, there was no difference in proliferative cell response to antigen ex vivo. Moreover, regardless of the parasite challenge, association of LaAg with MPL/AddaVax^® did not significantly enhance protection in comparison with LaAg alone. This work demonstrated that MPL/AddaVax^® is not effective in improving the efficacy of i.m. LaAg vaccine against cutaneous leishmaniasis.

Antileishmanial Chemotherapy through Clemastine Fumarate Mediated Inhibition of the Leishmania Inositol Phosphorylceramide Synthase

Current chemotherapeutics for leishmaniasis have multiple deficiencies, and there is a need for new safe, efficacious, and affordable medicines. This study describes a successful drug repurposing approach that identifies the over-the-counter antihistamine, clemastine fumarate, as a potential antileishmanial drug candidate. The screening for inhibitors of the sphingolipid synthase (inositol phosphorylceramide synthase, IPCS) afforded, following secondary screening against Leishmania major (Lmj) promastigotes, 16 active compounds. Further refinement through the dose response against LmjIPCS and intramacrophage L. major amastigotes identified clemastine fumarate with good activity and selectivity with respect to the host macrophage. On target engagement was supported by diminished sensitivity in a sphingolipid-deficient L. major mutant (ΔLmjLCB2) and altered phospholipid and sphingolipid profiles upon treatment with clemastine fumarate. The drug also induced an enhanced host cell response to infection indicative of polypharmacology. The activity was sustained across a panel of Old and New World Leishmania species, displaying an in vivo activity equivalent to the currently used drug, glucantime, in a mouse model of L. amazonensis infection. Overall, these data validate IPCS as an antileishmanial drug target and indicate that clemastine fumarate is a candidate for repurposing for the treatment of leishmaniasis.

Encapsulation in lipid-core nanocapsules improves topical treatment with the potent antileishmanial compound CH8

Cutaneous leishmaniasis (CL) is a neglected parasitic disease conventionally treated by multiple injections with systemically toxic drugs. Aiming at a more acceptable therapy, we developed lipid-core nanocapsules (LNCs) entrapping the potent antileishmanial chalcone (CH8) for topical application. Rhodamine-labeled LNC (Rho-LNC-CH8) was produced for imaging studies. LNC-CH8 and Rho-LNC-CH8 had narrow size distributions (polydispersity index <0.10), with similar mean sizes (~180 nm) by dynamic light scattering. In vitro, Rho-LNC-CH8 was rapidly internalized by extracellular Leishmania amazonensis parasites macrophages in less than 15 min. LNC-CH8 activated macrophage oxidative mechanisms more efficiently than CH8, and was more selectively toxic against the intracellular parasites. In vivo, topically applied Rho-LNC-CH8 efficiently permeated mouse skin. In L. amazonensis-infected mice, LNC-CH8 reduced the parasite load by 86% after three weeks of daily topical treatment, while free CH8 was ineffective. In conclusion, LNC-CH8 has strong potential as a novel topical formulation for CL treatment.

Novel and safe single-dose treatment of cutaneous leishmaniasis with implantable amphotericin B-loaded microparticles

The development of an effective amphotericin B (AmB) topical formulation to replace the systemically toxic injections currently used in cutaneous leishmaniasis (CL) treatment is challenging due to poor absorption through the skin. Aiming at an effective local chemotherapy, we designed PLGA (poly(lactide-co-glycolide acid) microparticles loaded with deoxycholate amphotericin B (d-AmB) for both macrophage intracellular targeting and sustained extracellular release. For that, d-AmB/PLGA microparticles with sizes ranging from 0.5 μm to 20 μm were synthesized and tested both in vitro and in vivo. In vitro, d-AmB/PLGA was more selectively active against intracellular amastigotes of Leishmania amazonensis than free d-AmB (selectivity index = 50 and 25, respectively). In vivo, the efficacy of a single intralesional (i.l) injection with d-AmB/PLGA was determined in early and established BALB/c mouse ear lesions. In early lesions, a single injection given on day 10 of infection was more effective in controlling parasite growth than eight i.l. injections with free d-AmB, as measured on day 120. Such d-AmB/PLGA injection was also effective in established lesions (day 30), leading to 97% parasite burden reduction, as compared with d-AmB or liposomal AmB (Ambisome®) i.l. injection containing the same AmB dose. Pharmacokinetic studies showed that following d-AmB/PLGA injection, AmB leaked slower from non-infected than infected ears, yet remaining in the ear tissue for as long as 30 days. Of interest, AmB was not detectable in the circulating plasma for at least two weeks of d-AmB/PLGA injection, contrasting with the rapid and durable (2 days) detection after free d-AmB injection. Despite the transient ear swelling and local cell infiltration, no alterations in AST, ALT and creatinine serum levels was induced by d-AmB/PLGA. For its approved components, local efficacy, and single-dose applicability, this novel and safe AmB microparticle depot formulation has strong potential as a new therapy for human CL.

Nanoencapsulated retinoic acid as a safe tolerogenic adjuvant for intranasal vaccination against cutaneous leishmaniasis

Mucosal, but not peripheral, vaccination with whole Leishmania amazonensis antigen (LaAg) effectively protects mice against leishmaniasis, likely through a tolerogenic mechanism. Given the crucial role of retinoic acid (RA) in CD4⁺ Foxp3⁺ regulatory T cell (T_reg) differentiation and mucosal tolerance, here we evaluated the capacity of RA to improve intranasal (i.n.) vaccination with LaAg. To prevent degradation and possible mucosa irritation, RA was encapsulated in solid lipid nanoparticles (RA-SLN). Thus, BALB/c mice were given two i.n. doses of LaAg alone or in association with RA-SLN (LaAg/RA-SLN) prior to challenge with L. amazonensis. No histological sign of irritation or inflammation was produced in the nasal mucosa after RA-SLN administration. LaAg/RA-SLN vaccine was more effective in delaying lesion growth and reducing parasite burdens than LaAg alone (96% and 61% reduction, respectively). At two months after challenge, both vaccinated groups displayed similar T helper (Th) 1-skewed in situ cytokine responses, different from early infection where both Th1 and Th2 responses were suppressed, except for transforming growth factor (TGF)-β mRNA, that was higher in mice given RA-SLN. At the mucosa, RA-SLN promoted enhanced expression of interleukin (IL)-10 and CD4⁺ Foxp3⁺ T_reg population. In sum, these data show that RA-SLN is an effective and safe tolerogenic adjuvant for i.n. vaccination against leishmaniasis.

Dietary Vitamin D3 Deficiency Increases Resistance to Leishmania (Leishmania) amazonensis Infection in Mice

The leishmaniases are a group of diseases caused by Leishmania parasites, which have different clinical manifestations. Leishmania (Leishmania) amazonensis is endemic in South America and causes cutaneous leishmaniasis (CL), which can evolve into a diffuse form, characterized by an anergic immune response. Since the leishmaniases mainly affect poor populations, it is important to understand the involvement of immunonutrition, how the immune system is modulated by dietary nutrients and the effect this has on Leishmania infection. Vitamin D3 (VitD) is an immunonutrient obtained from diet or endogenously synthesized, which suppresses Th1 and Th17 responses by favoring T helper (Th) 2 and regulatory T cell (Treg) generation. Based on these findings, this study aims to evaluate dietary VitD influence on L. (L.) amazonensis experimental infection in C57BL/6 and BALB/c mice. Thus, C57BL/6 and BALB/c VitD deficient (VDD) mice were generated through dietary VitD restriction 45 days prior to infection. Both strains of VDD mice showed a more controlled lesion development compared to mice on a regular diet (Ctrl). There were no differences in serum levels of anti-Leishmania IgG1 and IgG2a, but there was a decrease in IgE levels in BALB/c VDD mice. Although CD4⁺ T cell number was not changed, the CD4⁺ IFN-y⁺ T cell population was increased in both absolute number and percentage in C57BL/6 and BALB/c VDD mice compared to Ctrl mice. There was also no difference in IL-4 and IL-17 production, however, there was reduction of IL-10 production in VDD mice. Together, our data indicate that VitD contributes to murine cutaneous leishmaniasis susceptibility and that the Th1 cell population may be related to the resistance of VDD mice to L. (L.) amazonensis infection.

Pam3CSK4 adjuvant given intranasally boosts anti-Leishmania immunogenicity but not protective immune responses conferred by LaAg vaccine against visceral leishmaniasis

The use of adjuvants in vaccine formulations is a well-established practice to improve immunogenicity and protective immunity against diseases. Previously, we have demonstrated the feasibility of intranasal vaccination with the antigen of killed Leishmania amazonensis promastigotes (LaAg) against experimental leishmaniasis. In this work, we sought to optimize the immunogenic effect and protective immunity against murine visceral leishmaniasis conferred by intranasal delivery of LaAg in combination with a synthetic TLR1/TLR2 agonist (Pam3CSK4). Intranasal vaccination with LaAg/PAM did not show toxicity or adverse effects, induced the increase of delayed-type hypersensitivity response and the production of inflammatory cytokines after parasite antigen recall. However, mice vaccinated with LaAg/PAM and challenged with Leishmania infantum presented significant reduction of parasite burden in both liver and spleen, similar to those vaccinated with LaAg. Although LaAg/PAM intranasal vaccination had induced higher frequencies of specific CD4⁺ and CD8⁺ T cells and increased levels of IgG2a antibody isotype in serum, both LaAg and LaAg/PAM groups presented similar levels of IL-4 and IFN-y and decreased production of IL-10 when compared to controls. Our results provide the first evidence of the feasibility of intranasal immunization with antigens of killed Leishmania in association with a TLR agonist, which may be explored for developing an effective and alternative strategy for vaccination against visceral leishmaniasis.

The role of TLR9 on Leishmania amazonensis infection and its influence on intranasal LaAg vaccine efficacy

Leishmania (L.) amazonensis is one of the etiological agents of cutaneous leishmaniasis (CL) in Brazil. Currently, there is no vaccine approved for human use against leishmaniasis, although several vaccine preparations are in experimental stages. One of them is Leishvacin, or LaAg, a first-generation vaccine composed of total L. amazonensis antigens that has consistently shown an increase of mouse resistance against CL when administered intranasally (i.n.). Since Toll-like receptor 9 (TLR9) is highly expressed in the nasal mucosa and LaAg is composed of TLR9-binding DNA CpG motifs, in this study we proposed to investigate the role of TLR9 in both L. amazonensis infection and in LaAg vaccine efficacy in C57BL/6 (WT) mice and TLR9^-/- mice. First, we evaluated, the infection of macrophages by L. amazonensis in vitro, showing no significant difference between macrophages from WT and TLR9^-/- mice in terms of both infection percentage and total number of intracellular amastigotes, as well as NO production. In addition, neutrophils from WT and TLR9^-/- mice had similar capacity to produce neutrophil extracellular traps (NETs) in response to L. amazonensis. L. amazonensis did not activate dendritic cells from WT and TLR9^-/- mice, analysed by MHCII and CD86 expression. However, in vivo, TLR9^-/- mice were slightly more susceptible to L. amazonensis infection than WT mice, presenting a larger lesion and an increased parasite load at the peak of infection and in the chronic phase. The increased TLR9^-/- mice susceptibility was accompanied by an increased IgG and IgG1 production; a decrease of IFN-γ in infected tissue, but not IL-4 and IL-10; and a decreased number of IFN-γ producing CD8⁺ T cells, but not CD4⁺ T cells in the lesion-draining lymph nodes. Also, TLR9^-/- mice could not control parasite growth following i.n. LaAg vaccination unlike the WT mice. This protection failure was associated with a reduction of the hypersensitivity response induced by immunization. The TLR9^-/- vaccinated mice failed to respond to antigen stimulation and to produce IFN-γ by lymph node cells. Together, these results suggest that TLR9 contributes to C57BL/6 mouse resistance against L. amazonensis, and that the TLR9-binding LaAg comprising CpG motifs may be important for intranasal vaccine efficacy against CL.

Leishmaniasis is a major neglected tropical disease, being responsible for more than 20 million deaths per year. The high mortality rate highlights the difficulties and ineffectiveness of the current prophylactic approaches and treatments currently available. Therefore, the development of an effective vaccine would be highly advantageous to circumvent these problems. Despite the many vaccines preparations that have been studied in the last few years, none have shown satisfactory efficacy to be approved for human use. Immune receptors, including the TLR family, are known to be important for host defense during parasitic infections, such as leishmaniasis, and also for vaccine efficacy. In this work, we investigate the role of TLR9 during Leishmania amazonensis infection in vaccinated and non-vaccinated mice. We used a C57BL/6 TLR9-/- mouse model and a first-generation vaccine preparation (LaAg) composed of a total lysate of L. amazonensis. We demonstrate that TLR9 is important for controlling leishmaniasis infection caused by L. amazonensis and is involved in the efficacy of the LaAg vaccine. These findings will certainly help in the development of a better vaccine against leishmaniasis.

Suppressive effects of Vochysia divergens aqueous leaf extract and its 5-methoxyflavone on murine macrophages and lymphocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Vochysia divergens Pohl (Vochysiaceae), popularly known as "Cambará", is a tree that is resistant to the seasonal floods in the Pantanal, and usually found in monodominant stands called "Cambarazal". The inhabitants of the Pantanal exploit this tree for medicinal uses. Infusions and decoctions of its leaves are taken as teas, particularly for the treatment of asthma, flu and diarrhea, according to the local tradition transmitted empirically through the generations.

AIM OF THE STUDY

To evaluate the beneficial health effects related to the ethnomedicinal uses of V. divergens (Vd) by using biomonitored fractionation of an aqueous leaf extract.

MATERIALS AND METHODS

The aqueous leaf extract was obtained by decoction, and then the extract was fractionated by a combination of separation techniques including precipitation, organic partition and chromatography. Chromatographic analyses of the active samples were carried out using HPLC-DAD-MS. Flavonoid 1 was isolated from the n-BuOH fraction through classic chromatographic techniques. The inhibitory effects and cytotoxicity of the Vd extract, fractions and flavonoid 1 on NO and TNF-α production were assessed in LPS-stimulated RAW 264.7 macrophage cultures. Additionally, suppression on the proliferation of BALB/c lymphocytes was estimated by [³H] thymidine incorporation. The antioxidant activity of the samples was verified by SNP and DPPH assays and the suppression of the iNOS protein expression was evaluated through Western blotting.

RESULTS

The HPLC-DAD-MS analysis of the Vd extract led to the identification of 5-methoxyluteolin-7-O-β-glucopyranoside (2), rutin (4) and the tannin galloyl-HHDP-glucopyranoside (3), besides the main flavonoid 3',5-dimethoxyluteolin-7-O-β-glucopyranoside (1), which was biologically evaluated in comparison with luteolin aglycone. The Vd extract, n-BuOH fraction and flavonoid 1 inhibited NO and TNF-α production by LPS-stimulated macrophages. The reduction of NO levels was mediated mainly by suppression of the iNOS expression. In addition, both the Vd extract (IC₅₀ 13.6 µg/mL) and flavonoid 1 (IC₅₀ 19.8 µg/mL; 41.6 µM) strongly inhibited stimulated lymphocyte proliferation when compared to the immunosuppressive agent cyclosporin A (IC₅₀ 43.8 µg/mL; 36.4 µM). The Vd extract also showed a scavenging activity toward DPPH and NO free radicals. This is the first report describing the immunomodulatory potential of V. divergens and its major flavonoid (1).

CONCLUSION

Our findings showed that the aqueous leaf extract of V. divergens and its flavonoid reduced the production of excessive pro-inflammatory markers, collaborating with the Pantanal folk medicinal tradition that recommends the tea of cambará leaves for both asthma and flu. In addition, this study contributes to the knowledge of the pharmacological properties of 5-methoxy flavones, a poorly investigated subclass of flavonoids.

Optimization of Aqueous Extraction from Kalanchoe pinnata Leaves to Obtain the Highest Content of an Anti-inflammatory Flavonoid using a Response Surface Model

INTRODUCTION

The medicinal plant Kalanchoe pinnata is a phenolic-rich species used worldwide. The reports on its pharmacological uses have increased by 70% in the last 10 years. The leaves of this plant are the main source of an unusual quercetin-diglycosyl flavonoid (QAR, quercetin arabinopyranosyl rhamnopyranoside), which can be easily extracted using water. QAR possess a strong in vivo anti-inflammatory activity.

OBJECTIVE

To optimize the aqueous extraction of QAR from K. pinnata leaves using a three-level full factorial design.

MATERIAL AND METHODS

After a previous screening design, time (x₁ ) and temperature (x₂ ) were chosen as the two independent variables for optimization. Freeze-dried leaves were extracted with water (20% w/v), at 30°C, 40°C or 50°C for 5, 18 or 30 min. QAR content (determined by HPLC-DAD) and yield of extracts were analyzed. The optimized extracts were also evaluated for cytotoxicity.

RESULTS

The optimal heating times for extract yield and QAR content were similar in two-dimensional (2D) surface responses (between 12.8 and 30 min), but their optimal extraction temperatures were ranged between 40°C and 50°C for QAR content and 30°C and 38°C for extract yield. A compromise region for both parameters was at the mean points that were 40°C for the extraction temperature and 18 min for the total time.

CONCLUSION

The optimized process is faster and spends less energy than the previous one (water; 30 min at 55°C); therefore is greener and more attractive for industrial purposes. This is the first report of extraction optimization of this bioactive flavonoid. Copyright © 2018 John Wiley & Sons, Ltd.

Intralesional uridine-5'-triphosphate (UTP) treatment induced resistance to Leishmania amazonensis infection by boosting Th1 immune responses and reactive oxygen species production

Leishmania amazonensis is the etiologic agent of cutaneous leishmaniasis, an immune-driven disease causing a range of clinical symptoms. Infections caused by L. amazonensis suppress the activation and function of immune cells, including macrophages, dendritic cells, and CD4⁺ T cells. In this study, we analyzed the course of infection as well as the leishmanicidal effect of intralesional UTP treatment in L. amazonensis-infected BALB/c mice. We found that UTP treatment reduced the parasitic load in both footpad and lymph node sites of infection. UTP also boosted Th1 immune responses, increasing CD4⁺ T cell recruitment and production of IFN-γ, IL-1β, IL-12, and TNF-α. In addition, the role of UTP during innate immune response against L. amazonensis was evaluated using the air pouch model. We observed that UTP augmented neutrophil chemoattraction and activated microbicidal mechanisms, including ROS production. In conclusion, our data suggested an important role for this physiological nucleotide in controlling L. amazonensis infection, and its possible use as a therapeutic agent for shifting immune responses to Th1 and increasing host resistance against L. amazonensis infection.

Depot Subcutaneous Injection with Chalcone CH8-Loaded Poly(Lactic-Co-Glycolic Acid) Microspheres as a Single-Dose Treatment of Cutaneous Leishmaniasis

Conventional chemotherapy of cutaneous leishmaniasis (CL) is based on multiple parenteral or intralesional injections with systemically toxic drugs. Aiming at a single-dose localized therapy, biodegradable poly(lactic-co-glycolic acid) (PLGA) microparticles loaded with 7.8% of an antileishmanial nitrochalcone named CH8 (CH8/PLGA) were constructed to promote sustained subcutaneous release. In vitro, murine macrophages avidly phagocytosed CH8/PLGA smaller than 6 μm without triggering oxidative mechanisms. Upon 48 h of incubation, both CH8 and CH8/PLGA were 40 times more toxic to intracellular Leishmania amazonensis than to macrophages. In vivo, BALB/c were given one or three subcutaneous injections in the infected ear with 1.2 mg/kg of CH8 in free or CH8/PLGA forms, whereas controls received three CH8-equivalent doses of naked PLGA microparticles or meglumine antimoniate (Glucantime; Sanofi-Aventis). Although a single injection with CH8/PLGA reduced the parasite loads by 91%, triple injections with free CH8 or CH8/PLGA caused 80 and 97% reductions, respectively, in relation to saline controls. Meglumine antimoniate treatment was the least effective (only 36% reduction) and the most toxic, as indicated by elevated alanine aminotransferase serum levels. Together, these findings show that CH8/PLGA microparticles can be effectively and safely used for single-dose treatment of CL.

Repurposing as a strategy for the discovery of new anti-leishmanials: the-state-of-the-art

Leishmaniasis is a vector-borne neglected tropical disease caused by protozoan parasites of the genus Leishmania for which there is a paucity of effective viable non-toxic drugs. There are 1·3 million new cases each year causing considerable socio-economic hardship, best measured in 2·4 million disability adjusted life years, with greatest impact on the poorest communities, which means that desperately needed new antileishmanial treatments have to be both affordable and accessible. Established medicines with cheaper and faster development times may hold the cure for this neglected tropical disease. This concept of using old drugs for new diseases may not be novel but, with the ambitious target of controlling or eradicating tropical diseases by 2020, this strategy is still an important one. In this review, we will explore the current state-of-the-art of drug repurposing strategies in the search for new treatments for leishmaniasis.

The role of the P2X7 receptor in murine cutaneous leishmaniasis: aspects of inflammation and parasite control

Leishmania amazonensis is the etiological agent of diffuse cutaneous leishmaniasis. The immunopathology of leishmaniasis caused by L. amazonensis infection is dependent on the pathogenic role of effector CD4⁺ T cells. Purinergic signalling has been implicated in resistance to infection by different intracellular parasites. In this study, we evaluated the role of the P2X7 receptor in modulating the immune response and susceptibility to infection by L. amazonensis. We found that P2X7-deficient mice are more susceptible to L. amazonensis infection than wild-type (WT) mice. P2X7 deletion resulted in increased lesion size and parasite load. Our histological analysis showed an increase in cell infiltration in infected footpads of P2X7-deficient mice. Analysis of the cytokine profile in footpad homogenates showed increased levels of IFN-γ and decreased TGF-β production in P2X7-deficient mice, suggesting an exaggerated pro-inflammatory response. In addition, we observed that CD4⁺ and CD8⁺ T cells from infected P2X7-deficient mice exhibit a higher proliferative capacity than infected WT mice. These data suggest that P2X7 receptor plays a key role in parasite control by regulating T effector cells and inflammation during L. amazonensis infection.

Efficacy of intranasal LaAg vaccine against Leishmania amazonensis infection in partially resistant C57Bl/6 mice

Background

We have previously demonstrated that intranasal vaccination of highly susceptible BALB/c mice with whole Leishmania amazonensis antigens (LaAg) leads to protection against murine cutaneous leishmaniasis. Here, we evaluate the response of partially resistant C57BL/6 mice to vaccination as a more representative experimental model of human cutaneous leishmaniasis.

Methods

C57BL/6 mice from different animal facilities were infected with L. amazonensis (Josefa strain) to establish the profile of infection. Intranasal vaccination was performed before the infection challenge with two doses of 10 μg of LaAg alone or associated with the adjuvant ADDAVAX® by instillation in the nostrils. The lesion progression was measured with a dial caliper and the parasite load by limited dilution assay in the acute and chronic phases of infection. Cytokines were quantified by ELISA in the homogenates of infected footpads.

Results

C57BL/6 mice from different animal facilities presented the same L. amazonensis infection profile, displaying a progressive acute phase followed by a controlled chronic phase. Parasites cultured in M199 and Schneider’s media were equally infective. Intranasal vaccination with LaAg led to milder acute and chronic phases of the disease. The mechanism of protection was associated with increased production of IFN-gamma in the infected tissue as measured in the acute phase. Association with the ADDAVAX® adjuvant did not improve the efficacy of intranasal LaAg vaccination. Rather, ADDAVAX® reduced vaccination efficacy.

Conclusion

This study demonstrates that the efficacy of adjuvant-free intranasal vaccination with LaAg is extendable to the more resistant C57Bl/6 mouse model of infection with L. amazonensis, and is thus not exclusive to the susceptible BALB/c model. These results imply that mucosal immunomodulation by LaAg leads to peripheral protection irrespective of the genetic background of the host.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1822-9) contains supplementary material, which is available to authorized users.

How Sorbitan Monostearate Can Increase Drug-Loading Capacity of Lipid-Core Polymeric Nanocapsules

Lipid-core polymeric nanocapsules are innovative devices that present distinguished characteristics due to the presence of sorbitan monostearate into the oily-core. This component acted as low-molecular-mass organic gelator for the oil (medium chain triglycerides). The organogel-structured core influenced the polymeric wall characteristics disfavoring the formation of more stable polymer crystallites. This probably occurred due to interpenetration of these pseudo-phases. Sorbitan monostearate dispersed in the oily-core was also able to interact by non-covalent bonding with the drugs increasing the drug loading capacity more than 40 times compared to conventional nanocapsules. We demonstrated that the drug-models quercetin and quercetin pentaacetate stabilized the organogel network probably due to interactions of the drug molecules with the sorbitan monostearate headgroups by hydrogen bonding.

Intranasal vaccination with extracellular serine proteases of Leishmania amazonensis confers protective immunity to BALB/c mice against infection

Background

Previously, we demonstrated that unlike subcutaneous or intramuscular vaccination, intranasal vaccination of BALB/c mice with whole Leishmania amazonensis antigens leads to protection against cutaneous leishmaniasis. Here, the role of parasite serine proteases in the protective immunity was investigated.

Findings

Serine Proteases were partially purified from both soluble (LaSP-Sol) and extracellular (LaSP-Ex) Leishmania amazonensis promastigote extracts by aprotinin-agarose chromatography. BALB/c mice were intranasally immunized with LaSP-Sol and LaSP-Ex prior to infection with L. amazonensis. LaSP-Ex but not LaSP-Sol vaccination led to significantly smaller lesions and parasite burdens as compared with non-vaccinated controls. Protection was accompanied by systemic Th1 polarization with increased IFN-γ and decreased IL-4 and IL-10 splenic production. Likewise, increased production of IFN-γ, IL-12 and IL-4 concomitant with decreased TGF-β and TNF-α was locally observed in the infected footpad.

Conclusion

This study indicates that extracellular serine proteases of L. amazonensis are strong candidates for a more defined intranasal vaccine against cutaneous leishmaniasis.

Electronic supplementary material

The online version of this article (doi:10.1186/1756-3305-7-448) contains supplementary material, which is available to authorized users.

Periodate-oxidized ATP modulates macrophage functions during infection with Leishmania amazonensis

Previously, we showed that treating macrophages with ATP impairs the intracellular growth of Leishmania amazonensis, and that the P2X7 purinergic receptor is overexpressed during leishmaniasis. In the present study, we directly evaluated the effect of periodate-oxidized ATP (oATP) on parasite control in Leishmania-infected macrophages. We found that oATP impaired the attachment/entrance of L. amazonensis promastigotes to C57BL/6 mouse macrophages in a P2X7 receptor-independent manner, as macrophages from P2X7(-/-) mice were similarly affected. Although oATP directly inhibited the growth of axenic promastigotes in culture, promoted rapid ultrastructural alterations, and impaired Leishmania internalization by macrophages, it did not affect intracellular parasite multiplication. Upon infection, phagosomal acidification was diminished in oATP-treated macrophages, accompanied by reduced endosomal proteolysis. Likewise, MHC class II molecules expression and ectoATPase activity was decreased by oATP added to macrophages at the time of parasite infection. These inhibitory effects were not due to a cytotoxic effect, as no additional release of lactate dehydrogenase was detected in culture supernatants. Moreover, the capacity of macrophages to produce nitric oxide and reactive oxygen species was not affected by the presence of oATP during infection. We conclude that oATP directly affects extracellular parasite integrity and macrophage functioning.

Bone marrow-derived mononuclear cells promote improvement in glomerular function in rats with early diabetic nephropathy

BACKGROUND/AIMS

Diabetic nephropathy is one of the main causes of end-stage renal disease. The present study investigated the effect of mononuclear cell (MC) therapy in rats subjected to diabetic nephropathy.

METHODS

Male Wistar rats were divided into control (CTRL), diabetic (DM), CTRL+MC and DM+MC groups. Diabetes was induced by a single injection of streptozotocin (45 mg/kg, i.p.) and, 4 weeks later, 2×10(7) MCs were injected via the jugular vein.

RESULTS

The rats in the DM and DM+MC groups showed increased glycemia, glomerular filtration rate and glomerular tuff area versus control groups. The glomerular filtration rate and glomerular tuff area were normalized in the DM+MC group. No alterations were observed in the fractional excretion of electrolytes and proteinuria between the DM and DM+MC groups. TGF-β1 protein levels in the DM group were significantly increased versus control animals and normalized in the DM+MC group. An increase in ED1(+)/arginase I(+) macrophages and IL-10 renal expression was observed in the DM+MC group versus DM group.

CONCLUSIONS

Bone marrow-derived MC therapy was able to prevent glomerular alterations and TGF-β1 protein overexpression and modulated glomerular arginase I(+) macrophage infiltration in rats subjected to early diabetic nephropathy.

The stepwise selection for ketoconazole resistance induces upregulation of C14-demethylase (CYP51) in Leishmania amazonensis

Ketoconazole is a clinically safe antifungal agent that also inhibits the growth of Leishmania spp. A study was undertaken to determine whether Leishmania parasites are prone to becoming resistant to ketoconazole by upregulating C14-demethylase after stepwise pharmacological pressure. Leishmania amazonensis promastigotes [inhibitory concentration (IC)₅₀ = 2 µM] were subjected to stepwise selection with ketoconazole and two resistant lines were obtained, La8 (IC₅₀ = 8 µM) and La10 (IC₅₀ = 10 µM). As a result, we found that the resistance level was directly proportional to the C14-demethylase mRNA expression level; we also observed that expression levels were six and 12 times higher in La8 and La10, respectively. This is the first demonstration that L. amazonensis can up-regulate C14-demethylase in response to drug pressure and this report contributes to the understanding of the mechanisms of parasite resistance.

Flowers from Kalanchoe pinnata are a rich source of T cell-suppressive flavonoids

The chemical composition and immunosuppressive potential of the flowers from Kalanchoe pinnata (Crassulaceae) were investigated. We found that the aqueous flower extract was more active than the leaf extract in inhibiting murine T cell mitogenesis in vitro. Flavonoids isolated from the flower extract were identified and quantitated based on NMR and HPLC-DAD-MS analysis, respectively. Along with quercetin, four quercetin glycosyl conjugates were obtained, including quercetin 3-O-beta-D-glucuronopyranoside and quercetin 3-O-beta-D-glucopyranoside, which are described for the first time in K. pinnata. All flavonoids inhibited murine T cell mitogenesis and IL-2 and IL-4 production without cell toxicity. This is the first report on the pharmacological activity of flowers of a Kalanchoe species, which are not used for curative purposes. Our findings show that K. pinnata flowers are a rich source of T-suppressive flavonoids that may be therapeutically useful against inflammatory diseases.

Flowers from Kalanchoe pinnata are a Rich Source of T Cell-Suppressive Flavonoids

The chemical composition and immunosuppressive potential of the flowers from Kalanchoe pinnata (Crassulaceae) were investigated. We found that the aqueous flower extract was more active than the leaf extract in inhibiting murine T cell mitogenesis in vitro. Flavonoids isolated from the flower extract were identified and quantitated based on NMR and HPLC-DAD-MS analysis, respectively. Along with quercetin, four quercetin glycosyl conjugates were obtained, including quercetin 3-O-β-D-glucuronopyranoside and quercetin 3-O-β-D-glucopyranoside, which are described for the first time in K. pinnata. All flavonoids inhibited murine T cell mitogenesis and IL-2 and IL-4 production without cell toxicity. This is the first report on the pharmacological activity of flowers of a Kalanchoe species, which are not used for curative purposes. Our findings show that K. pinnata flowers are a rich source of T-suppressive flavonoids that may be therapeutically useful against inflammatory diseases.

Kalanchoe pinnata inhibits mast cell activation and prevents allergic airway disease

Aqueous extract of Kalanchoe pinnata (Kp) have been found effective in models to reduce acute anaphylactic reactions. In the present study, we investigate the effect of Kp and the flavonoid quercetin (QE) and quercitrin (QI) on mast cell activation in vitro and in a model of allergic airway disease in vivo. Treatment with Kp and QE in vitro inhibited degranulation and cytokine production of bone marrow-derived mast cells following IgE/FcɛRI crosslinking, whereas treatment with QI had no effect. Similarly, in vivo treatment with Kp and QE decreased development of airway hyperresponsiveness, airway inflammation, goblet cell metaplasia and production of IL-5, IL-13 and TNF. In contrast, treatment with QI had no effect on these parameters. These findings demonstrate that treatment with Kp or QE is effective in treatment of allergic airway disease, providing new insights to the immunomodulatory functions of this plant.

Use of in vivo and in vitro systems to select Leishmania amazonensis expressing green fluorescent protein

Various Leishmania species were engineered with green fluorescent protein (GFP) using episomal vectors that encoded an antibiotic resistance gene, such as aminoglycoside geneticin sulphate (G418). Most reports of GFP-Leishmania have used the flagellated extracellular promastigote, the stage of parasite detected in the midgut of the sandfly vector; fewer studies have been performed with amastigotes, the stage of parasite detected in mammals. In this study, comparisons were made regarding the efficiency for in vitro G418 selection of GFP-Leishmania amazonensis promastigotes and amastigotes and the use of in vivo G418 selection. The GFP-promastigotes retained episomal plasmid for a prolonged period and G418 treatment was necessary and efficient for in vitro selection. In contrast, GFP-amastigotes showed low retention of the episomal plasmid in the absence of G418 selection and low sensitivity to antibiotics in vitro. The use of protocols for G418 selection using infected BALB/c mice also indicated low sensitivity to antibiotics against amastigotes in cutaneous lesions.

Infection with Leishmania amazonensis upregulates purinergic receptor expression and induces host-cell susceptibility to UTP-mediated apoptosis

Nucleotides are released into the extracellular milieu from infected cells and cells at inflammatory sites. The extracellular nucleotides bind to specific purinergic (P2) receptors and thereby induce a variety of cellular responses including anti-parasitic effects. Here we investigated whether extracellular nucleotides affect leishmanial infection in macrophages, and found that UTP reduces strongly the parasite load in peritoneal macrophages. Ultrastructural analysis of infected cells revealed that UTP induced morphological damage in the intracellular parasites. Uridine nucleotides also induced dose-dependent apoptosis of macrophages and production of ROI and RNI only in infected macrophages. The intracellular calcium measurements of infected cells showed that the response to UTP, but not UDP, increased the sensitivity and amplitude of cytosolic Ca(2+) changes. Infection of macrophages with Leishmania upregulated the expression of P2Y(2) and P2Y(4) receptor mRNA. The data suggest indirectly that Leishmania amazonensis infection induces modulation and heteromerization of P2Y receptors on macrophages. Thus UTP modulates the host response against L. amazonensis infection. UTP and UTP homologues should therefore be considered as novel components of therapeutic strategies against cutaneous leishmaniasis.

MyD88-dependent TLR1/2 signals educate dendritic cells with gut-specific imprinting properties

Gut-associated dendritic cells (DC) synthesize all-trans retinoic acid, which is required for inducing gut-tropic lymphocytes. Gut-associated DC from MyD88(-/-) mice, which lack most TLR signals, expressed low levels of retinal dehydrogenases (critical enzymes for all-trans retinoic acid biosynthesis) and were significantly impaired in their ability to induce gut-homing T cells. Pretreatment of extraintestinal DC with a TLR1/2 agonist was sufficient to induce retinal dehydrogenases and to confer these DC with the capacity to induce gut-homing lymphocytes via a mechanism dependent on MyD88 and JNK/MAPK. Moreover, gut-associated DC from TLR2(-/-) mice, or from mice in which JNK was pharmacologically blocked, were impaired in their education to imprint gut-homing T cells, which correlated with a decreased induction of gut-tropic T cells in TLR2(-/-) mice upon immunization. Thus, MyD88-dependent TLR2 signals are necessary and sufficient to educate DC with gut-specific imprinting properties and contribute in vivo to the generation of gut-tropic T cells.

Antileishmanial sesquiterpenes from the Brazilian red alga Laurencia dendroidea

Investigation of the bioactive crude extracts from two populations of the red alga Laurencia dendroidea from the southeastern Brazilian coast led to the identification of five sesquiterpenes: (+)-obtusane (1), a triquinane derivative (2), (-)-elatol (3), obtusol (4), and cartilagineol (5). An antileishmanial bioassay against Leishmania amazonensis was conducted for crude lipophilic extracts and for sesquiterpenes 2, 3, and 4. Compounds 3 and 4 displayed in vitro and in vivo leishmanicidal activity and very low cytotoxicity.

MyD88-dependent TLR signals are necessary and sufficient to confer dendritic cells with gut-specific imprinting properties. (161.2)

Lymphocyte migration is at the heart of normal and pathological immune responses in the intestinal mucosa. We and others have shown that, in addition to activating lymphocytes, gut-associated dendritic cells (GALT-DC) can metabolize dietary vitamin A into all-trans retinoic acid (RA), which is required for inducing gut-tropic lymphocytes and IgA antibody-secreting cells (IgA-ASC). GALT-DC from mice deficient in the intracellular signaling adaptor MyD88, which lack most Toll-like receptor (TLR) signals, were significantly impaired in their capacity to induce gut-homing T cells and IgA-ASC and expressed low levels of retinal dehydrogenases (RALDH), which are critical enzymes for RA biosynthesis. MyD88-/- mice were also impaired in generating gut-tropic T cells upon immunization and exhibited low numbers of intestinal IgA-ASC. Pre-treatment of murine spleen-DC and human monocyte-derived DC with a TLR1/2 agonist was sufficient to induce RALDH and to confer these extra-intestinal DC with the capacity to induce gut-homing lymphocytes and IgA-ASC via a mechanism dependent on MyD88 and c-JNK/MAPK. Thus, MyD88-dependent TLR signals are both necessary and sufficient to educate DC with gut-specific imprinting properties.

Nanostructured polymer and lipid carriers for sunscreen. Biological effects and skin permeation

The interest in developing new sunscreens is increasing due to the harmful effects of UV radiation on the skin, such as erythema, accelerated skin ageing (photoageing) and the induction of skin cancer. However, many molecular sunscreens penetrate into the skin causing photoallergies, phototoxic reactions and skin irritation. Thus, the aim of this work was the preparation and characterization of polymeric and solid lipid nanoparticles to act carriers of benzophenone-3 (BZ3), aiming to improve the safety of sunscreen products by increasing the sun protection factor (SPF), decreasing BZ3 skin penetration and decreasing BZ3 concentration in sunscreen formulation. BZ3 was encapsulated in poly(epsilon-caprolactone) (PCL) nanoparticles by the nanoprecipitation method and in solid lipid nanoparticles (SLN) by the hot high pressure homogenization method. The particles were stable for 40 days. The BZ3 encapsulated in PCL nanoparticles was released faster than BZ3 encapsulated in SLN. The sun protection factor increased when BZ3 was encapsulated in both nanostructures. However, BZ3 encapsulated in PCL nanoparticles decreased its skin permeation more than SLN-BZ3. Furthermore, BZ3 encapsulated in SLN did not exhibit cytotoxic or phototoxic effects in human keratinocytes (HaCaT cells) and BABL/c 3T3 fibroblasts, whereas PCL nanoparticles with BZ3 showed phototoxic potential in HaCaT cells. Nevertheless, BZ3 free and encapsulated in PCL nanoparticles or in SLN did not show allergic reactions in mice. Our results suggest that these nanostructures are interesting carriers for sunscreen.

Influence of cultivation conditions, season of collection and extraction method on the content of antileishmanial flavonoids from Kalanchoe pinnata

ETHNOPHARMACOLOGICAL RELEVANCE

Leaves from Kalanchoe pinnata (Lamarck) Persoon (Crassulaceae) are popularly used for healing wounds. Its antileishmanial properties are established in experimental animals, and its active flavonoid components have been identified.

AIM OF THE STUDY

In this study, we attempted to standardize the extract from K. pinnata leaves by evaluating the influence of season of harvest, sunlight exposure and method of extraction on antileishmanial flavonoids content.

MATERIALS AND METHODS

HPLC-DAD-MS was used to identify and quantify the active antileishmanial flavonoids in different extracts. ANOVA test for analyses of variance followed by the Tukey test of multiple comparisons were used in the statistical analysis. The antileishmanial potential was assessed by the activation of nitric oxide production by murine macrophage using the Griess method.

RESULTS

We demonstrated that active flavonoids were significantly more abundant when the leaves were collected in the summer, and that aqueous extraction at 50°C allowed the highest flavonoid extraction. The benefit of sunlight exposure was confirmed in plants cultivated under direct sunlight when compared with those that grown under shade. Under sunny conditions the yield of the most active antileishmanial favonoid quercitrin was increased by 7-fold. All aqueous extracts tested were capable to enhance the macrophage nitric oxide production. However, hot aqueous extract from leaves collected in summer exhibited the higher activity, in agreement with HPLC-DAD-MS analysis tendency. In addition, with the aim of reducing the individual chemical variations of the plant constituents and optimizing the production of the active extract, it was obtained in vitro monoclonal KP specimens that were easily adapted to field conditions and were able to produce antileishmanial flavonoids.

CONCLUSION

Our study reports the better conditions of cultivation, harvest and extraction protocol for obtaining a K. pinnata extract exhibiting the highest antileishmanial activity. Additionally, we propose the flavonoids quercetin 3-O-α-L-arabinopyranosyl (1→2)-α-L-rhamnopyranoside and quercitrin, as satisfactory chemical markers for standardization purposes.

Serine proteases of Leishmania amazonensis as immunomodulatory and disease-aggravating components of the crude LaAg vaccine

We previously demonstrated that intradermal and intramuscular vaccination with Leishmania amazonensis promastigote antigens (LaAg) increases the susceptibility of BALB/c mice to cutaneous leishmaniasis. In this study, we investigated the role played by serine and cysteine proteases as disease-promoting components of LaAg. Mice were immunized by the intramuscular route with LaAg that was pre-treated with a pool of serine or cysteine protease inhibitors (SPi and CPi, respectively) prior to infection with L. amazonensis. Neutralization of either enzyme type reversed the disease-promoting effect of LaAg, as seen by the slower lesion development. However, the parasite burden was only effectively controlled in mice receiving SPi-treated LaAg. Protection was associated with diminished production of TGF-beta and particularly IL-10 in response to parasite antigens by the lesion-draining lymph node cells of vaccinated mice relative to control. In vitro, soluble proteases isolated from LaAg (LaSP-Sol) directly activated IL-4, IL-10 and TGF-beta production by immune cells. Like native LaAg, vaccination with LaSP-Sol primed mice to respond to parasite challenge with a strong Jones-Mote cutaneous hypersensitivity reaction, and increased susceptibility to infection. Furthermore, neutralization of serine but not cysteine proteases blocked the capacity of LaAg to sensitize mice for Jones-Mote reaction. Together, these results indicate that soluble serine proteases are key components of LaAg responsible for its disease-promoting immunity.