Antifungal and immunomodulatory activity of a novel cochleate for amphotericin B delivery against Sporothrix schenckii

Feasibility of the preparation of cochleate suspensions from naturally derived phosphatidylserines

Introduction

Cochleates are cylindrical particles composed of dehydrated phospholipid bilayers. They are typically prepared by addition of calcium ions to vesicles composed of negatively charged phospholipids such as phosphatidylserines (PS). Due to their high physical and chemical stability, they provide an interesting alternative over other lipid-based drug formulations for example to improve oral bioavailability or to obtain a parenteral sustained-release formulation.

Methods

In the present study, the feasibility to prepare cochleate suspensions from soy lecithin-derived phosphatidylserines (SPS) was investigated and compared to the "gold standard" dioleoyl-phosphatidylserine (DOPS) cochleates. The SPS lipids covered a large range of purities between 53 and >96% and computer-controlled mixing was evaluated for the preparation of the cochleate suspensions. Electron microscopic investigations were combined with small-angle x-ray diffraction (SAXD) and Laurdan generalized polarization (GP) analysis to characterize particle structure and lipid organization.

Results

Despite some differences in particle morphology, cochleate suspensions with similar internal lipid structure as DOPS cochleates could be prepared from SPS with high headgroup purity (≥96%). Suspensions prepared from SPS with lower purity still revealed a remarkably high degree of lipid dehydration and well-organized lamellar structure. However, the particle shape was less defined, and the typical cochleate cylinders could only be detected in suspensions prepared with higher amount of calcium ions. Finally, the study proves the feasibility to prepare suspensions of cochleates or cochleate-like particles directly from a calcium salt of soy-PS by dialysis.

Efficacy of Cochleated Amphotericin B in Mouse and Human Mucocutaneous Candidiasis

Candida albicans causes debilitating, often azole-resistant, infections in patients with chronic mucocutaneous candidiasis (CMC). Amphotericin B (AMB) resistance is rare, but AMB use is limited by parenteral administration and nephrotoxicity. In this study, we evaluated cochleated AMB (CAMB), a new oral AMB formulation, in mouse models of oropharyngeal candidiasis (OPC) and vulvovaginal candidiasis (VVC) and in patients with azole-resistant CMC. OPC and VVC were modeled in Act1^-/- mice, and mucosal tissue fungal burden was assessed after once-daily treatment with CAMB, vehicle, or AMB-deoxycholate (AMB-d). Four patients with azole-resistant CMC enrolled in a phase 2 CAMB dose-escalation study. The primary endpoint was clinical improvement at 2 weeks followed by optional extension for long-term CMC suppression to assess safety and efficacy. CAMB-treated mice had significantly reduced tongue and vaginal fungal burdens compared to vehicle-treated mice and exhibited comparable fungal burden reduction relative to AMB-d-treated mice. All CAMB-treated patients reached clinical efficacy by 2 weeks, three at 400 mg twice daily and one at 200 mg twice-daily dosing. All patients continued to the extension phase, with three having sustained clinical improvement of OPC and esophageal candidiasis (EC) for up to 60 months. One patient had a relapse of esophageal symptoms at week 24 and was withdrawn from further study. Clinical responses were not seen for onychomycosis or VVC. CAMB was safe and well-tolerated, without any evidence of nephrotoxicity. In summary, oral CAMB reduced tongue and vaginal fungal burdens during murine candidiasis. A proof-of-concept clinical trial in human CMC showed efficacy with good tolerability and safety. This study has been registered at ClinicalTrials.gov under identifier NCT02629419.

Sporothrix schenckii regulates macrophage inflammatory responses via the c-JUN-induced Dab2 transcription

Macrophages, which serve as a bridge between innate and adaptive immunity, play an important role in sporotrichosis. Sporothrix schenckii infections can produce immune responses such as macrophage polarization and inflammatory factor secretion. In the early stages of inflammation, the expression of DAB2 in macrophages is increased, which controls the secretion of inflammatory factors and affects the polarization of macrophages. However, the expressions and mechanisms of DAB2 in sporotrichosis are not clear. In this study, we examined the expression of DAB2 and its regulation of inflammatory factors under conditions of Sporothrix schenckii infection. Our results indicated that the Sporothrix schenckii infection increased the expression of DAB2 and revealed a mixed M1/M2-like type of gene expression in BMDMs with the inhibited Il6, Il1β and Arg1, and induced Tnfα, Il10 and Mgl1. The deficiency of Dab2 gene suspended the changes of cytokines. In addition, JNK activity in BMDMs was inhibited by Sporothrix schenckii infection, leading to an increase in c-JUN. We also identified c-JUN as a transcription factor for Dab2 through chromatin immunoprecipitation and luciferase reporter assays. In an in vivo mouse model, sporotrichosis induced skin lesions were accompanied with an upregulation of c-JUN and inhibition of JNK activity, which were in accord with findings from in vitro experiments. Taken together, these findings indicate that in the early stages of Sporothrix schenckii infection there is a promotion of DAB2 expression through the JNK/c-JUN pathway, effects which can then control the expression of inflammatory factors.

Meta-Analysis of Drug Delivery Approaches for Treating Intracellular Infections

This meta-analysis aims to evaluate the trend, methodological quality and completeness of studies on intracellular delivery of antimicrobial agents. PubMed, Embase, and reference lists of related reviews were searched to identify original articles that evaluated carrier-mediated intracellular delivery and pharmacodynamics (PD) of antimicrobial therapeutics against intracellular pathogens in vitro and/or in vivo. A total of 99 studies were included in the analysis. The most commonly targeted intracellular pathogens were bacteria (62.6%), followed by viruses (16.2%) and parasites (15.2%). Twenty-one out of 99 (21.2%) studies performed neither microscopic imaging nor flow cytometric analysis to verify that the carrier particles are present in the infected cells. Only 31.3% of studies provided comparative inhibitory concentrations against a free drug control. Approximately 8% of studies, albeit claimed for intracellular delivery of antimicrobial therapeutics, did not provide any experimental data such as microscopic imaging, flow cytometry, and in vitro PD. Future research on intracellular delivery of antimicrobial agents needs to improve the methodological quality and completeness of supporting data in order to facilitate clinical translation of intracellular delivery platforms for antimicrobial therapeutics.

Future Directions for Clinical Respiratory Fungal Research

There has been a growing appreciation of the importance of respiratory fungal diseases in recent years, with better understanding of their prevalence as well as their global distribution. In step with the greater awareness of these complex infections, we are currently poised to make major advances in the characterization and treatment of these fungal diseases, which in itself is largely a consequence of post-genomic technologies which have enabled rational drug development and a path towards personalized medicines. These advances are set against a backdrop of globalization and anthropogenic change, which have impacted the world-wide distribution of fungi and antifungal resistance, as well as our built environment. The current revolution in immunomodulatory therapies has led to a rapidly evolving population at-risk for respiratory fungal disease. Whilst challenges are considerable, perhaps the tools we now have to manage these infections are up to this challenge. There has been a welcome acceleration of the antifungal pipeline in recent years, with a number of new drug classes in clinical or pre-clinical development, as well as new focus on inhaled antifungal drug delivery. The "post-genomic" revolution has opened up metagenomic diagnostic approaches spanning host immunogenetics to the fungal mycobiome that have allowed better characterization of respiratory fungal disease endotypes. When these advances are considered together the key challenge is clear: to develop a personalized medicine framework to enable a rational therapeutic approach.

Enzymatic synthesis of capric acid-rich structured lipids and their effects on mice with high-fat diet-induced obesity

The objective of this study was to produce structured lipids (SLs) by enzymatic acidolysis using Rhizopus oryzae lipase covalently immobilized in a low-cost material. Grape seed oil was used to synthesize SLs containing the medium-chain fatty acid (C10:0) capric acid. SL synthesis led to 38.8% medium-chain fatty acid incorporation with 5 reuses of the enzymatic derivative. The reaction conditions for the synthesis of MLM-TAGs (triacylglycerols with one long- and two medium-chain acyl residues) were at a molar ratio of fatty acid:oil of 3:1, performed at 40 °C and lipase immobilized load of 5% (w/w). The in vivo effects of SLs were studied in Swiss mice fed premade diets: control (C) diet, high-fat diet (HFD) with 100% lipid content as lard, HFD with 50% lipid content as grape seed oil (HG) or HFD with 50% lipid content as capric acid-containing SLs produced from grape seed oil (HG-MCT). Mice from HG and HG-MCT groups had decreases in body weight gain and reductions in the weights of white adipose tissues. In addition, HG and HG-MCT mice had low plasma levels of glucose and total cholesterol, and improvements in the glucose tolerance. HG and HG-MCT diets have remarkable antioxidant properties, since low plasma levels of TBARS (thiobarbituric acid reactive substances, biomarkers of lipid peroxidation) were found in mice fed these diets. Interestingly, TBARS levels in HG-MCT mice were further decreased than values of HG mice. Mice fed HG and HG-MCT diets also showed preservation in the activity of the antioxidant enzyme paraoxonase 1. Both HG and HG-MCT diets promoted reduction of IL-6 and IL-10 production by splenocytes. The capric acid-containing SLs produced from grape seed oil emerges as a functional oil capable to mitigate obesity complications resulting from oxidative stress and inflammation.

Antifungal activity of Acylhydrazone derivatives against Sporothrix spp

Sporotrichosis is an emerging mycosis caused by members of the genus Sporothrix The disease affects humans and animals, particularly cats, which plays an important role in the zoonotic transmission. Feline sporotrichosis treatment options include itraconazole (ITC), potassium iodide and amphotericin B, drugs usually associated with deleterious adverse reactions and refractoriness in cats, especially when using ITC. Thus, affordable, non-toxic and clinically effective anti-Sporothrix agents are needed. Recently, acylhydrazones (AH), molecules targeting vesicular transport and cell cycle progression, exhibited a potent antifungal activity against several fungal species and displayed low toxicity when compared to the current drugs. In this work, the AH derivatives D13 and SB-AF-1002 were tested against Sporothrix schenckii and Sporothrix brasiliensis Minimal inhibitory concentrations of 0.12 - 1 μg/mL were observed for both species in vitro D13 and SB-AF-1002 showed an additive effect with itraconazole. Treatment with D13 promoted yeast disruption with release of intracellular components, as confirmed by transmission electron microscopy of S. brasiliensis exposed to the AH derivatives. AH-treated cells displayed thickening of the cell wall, discontinuity of the cell membrane and an intense cytoplasmic degeneration. In a murine model of sporotrichosis, treatment with AH derivatives was more efficient than ITC, the drug of choice for sporotrichosis. The results of the preliminary clinical study in cats indicate that D13 is safe and has potential to become a therapeutic option for sporotrichosis when associated to ITC. Our results expand the antifungal broadness of AH derivatives and suggest that these drugs could be exploited to combat sporotrichosis.

Branched amphotericin functional poly(N-isopropyl acrylamide): an antifungal polymer

Branched poly(N-isopropylacrylamide) was functionalized with Amphotericin B (AmB) at the chain ends to produce an antifungal material. The polymer showed antifungal properties against AmB-sensitive strains of Candida albicans, Fusarium keratoplasticum and Aspergillus flavus (minimal inhibitory concentration ranged from 5 to 500 µg ml^-1) but was not effective against an AmB resistant strain of C. albicans nor against Candida tropicalis. The polymer end groups bound to the AmB target, ergosterol, and the fluorescence spectrum of a dye used as a solvatochromic probe, Nile red, was blue shifted indicating that segments of the polymer became desolvated on binding. The polymer was less toxic to corneal and renal epithelial cells and explanted corneal tissue than the free drug. Also, the polymer did not induce reactive oxygen species release from peripheral blood mononuclear cells, nor did it cause a substantial release of the proinflammatory cytokines, tumour necrosis factor-α and interleukin-1β (at 0.5 mg ml^-1).

A Critical Review of Analytical Methods for Quantification of Amphotericin B in Biological Samples and Pharmaceutical Formulations

Amphotericin B (AmB) is an important antifungal agent available in the clinical practice with the action mechanism related to the inhibition of ergosterol molecule present in the fungal cell wall. Given this, in order to expand AmB knowledge, this review article gathers important information of the AmB physical, chemical, and biological properties. In addition, the main analytical methods for quantifying and determining the AmB were also reported in this review, such as high-performance liquid chromatography (HPLC), liquid chromatography, tandem mass spectrophotometry (LC-MS/MS), immunoenzymatic assay (ELISA), capillary zone electrophoresis (CE) stands out and among others. Based in this review article, the scientific community will have important information to choose the best method for analysis in their scientific or clinical research, providing greater security and reliability in the obtained results.

Encochleated Amphotericin B: Is the Oral Availability of Amphotericin B Finally Reached?

As the oldest and for many decades the only available agent for the treatment of life-threatening invasive fungal diseases, amphotericin B (AmB) is known for its broad-spectrum fungicidal activity against a wide range of yeasts and molds. However, the main drawback of the present formulations remains its toxicity, the limited use to intravenous administration, and the higher costs associated with the better tolerated lipid formulations. The novel nanoparticle-based encochleated AmB (CAmB) formulation encapsulates, protects, and delivers its cargo molecule AmB in the interior of a calcium-phospholipid anhydrous crystal. Protecting AmB from harsh environmental conditions and gastrointestinal degradation, CAmB offers oral availability in conjunction with reduced toxicity. Matinas BioPharma, Bedminster, NJ is on the way to develop CAmB named MAT2203, currently undergoing Phase II clinical trials.

Lipid Systems for the Delivery of Amphotericin B in Antifungal Therapy

Amphotericin B (AmB), a broad-spectrum polyene antibiotic in the clinic for more than fifty years, remains the gold standard in the treatment of life-threatening invasive fungal infections and visceral leishmaniasis. Due to its poor water solubility and membrane permeability, AmB is conventionally formulated with deoxycholate as a micellar suspension for intravenous administration, but severe infusion-related side effects and nephrotoxicity hamper its therapeutic potential. Lipid-based formulations, such as liposomal AmB, have been developed which significantly reduce the toxic side effects of the drug. However, their high cost and the need for parenteral administration limit their widespread use. Therefore, delivery systems that can retain or even enhance antimicrobial efficacy while simultaneously reducing AmB adverse events are an active area of research. Among those, lipid systems have been extensively investigated due to the high affinity of AmB for binding lipids. The development of a safe and cost-effective oral formulation able to improve drug accessibility would be a major breakthrough, and several lipid systems for the oral delivery of AmB are currently under development. This review summarizes recent advances in lipid-based systems for targeted delivery of AmB focusing on non-parenteral nanoparticulate formulations mainly investigated over the last five years and highlighting those that are currently in clinical trials.

A Recombinant Enolase-Montanide™ PetGel A Vaccine Promotes a Protective Th1 Immune Response against a Highly Virulent Sporothrix schenckii by Toluene Exposure

The effect of vaccination in fungal strains that suffered changes in their virulence by exposure to environmental contaminants is largely known. Growing reports of resistance to antifungal drugs and the emergence of new highly virulent strains, possibly acquired in the environment, prompt the design of new vaccines able to prevent and combat emerging mycotic diseases. In this study, we evaluated the protective capacity of an enolase-based vaccine and Montanide PetGel A (PGA) as an adjuvant against S. schenckii with increased virulence by exposure to toluene. The adjuvanted vaccine induced a strong specific Th1 response and protective immunity against a challenge with either wildtype or toluene-adapted S. schenckii in Balb/c mice. This study highlights the role of the adjuvant PGA driving the quality of the anti-sporothrix immunity and the key component in the vaccine efficacy.

Hyaluronic acid conjugated multi-walled carbon nanotubes for colon cancer targeting

Purpose of the present research was to evaluate in vitro and in vivo potential of gemcitabine (GEM) loaded hyaluronic acid (HA) conjugated PEGylated multi-walled carbon nanotubes (GEM/HA-PEG-MWCNTs) for effective colon cancer targeting. HA was conjugated onto the surface of aminated or PEGylated MWCNTs which were evaluated for size, surface morphology, entrapment efficiency (~90%), in vitro drug release, in vitro cytotoxicity and in vivo performance in Sprague Dawley rats. In vitro release showed that the release rate of GEM in acidic conditions (pH 5.3) was faster than physiological conditions (PBS, pH 7.4) followed by a sustained release pattern. The developed GEM/HA-PEG-MWCNTs indicated significantly less hemolytic toxicity (7.73 ± 0.4%) paralleled to free GEM (18.71 ± 0.44%) and showed higher cytotoxicity against HT-29 colon cancer cell line. The antitumor study assured that GEM/HA-PEG-MWCNTs significantly reduced tumor volume as compared to free GEM and increased survival rate without noticeable loss in body weight. In vivo studies showed an improvement in pharmacokinetics in terms of remarkable escalation in mean residence time, half-life, AUC, AUMC, median survival time in tumor bearing rats treated with GEM/HA-MWCNTs and GEM/HA-PEG-MWCNTs as compared to free GEM (p ˂ 0.001). These outcomes proved engineered MWCNTs as a safe and effective nanomedicine in colon cancer targeting.

Sporothrix brasiliensis induces a more severe disease associated with sustained Th17 and regulatory T cells responses than Sporothrix schenckii sensu stricto in mice

Little is known about the differences in the CD4+ T-cell response induced by Sporothrix schenckii and Sporothrix brasiliensis, the most virulent species that cause sporotrichosis. Here, the helper (Th) and regulatory T cells (Tregs) responses were evaluated comparatively in a murine model of sporotrichosis on days 7, 21 and 35 after subcutaneous infection with either S. schenckii or S. brasiliensis conidia. The fungal load was measured at the site of infection, as well as in the liver and spleen. The Th1/Th17/Tregs responses were analyzed in the spleen, while the level of IL-2, IL-4, IL-6, TNF-alpha, IFN-ɣ, IL-17A and IL-10 cytokines were measured at the local site of infection on 24 h postinfections and in sera on the indicated days. S. brasiliensis caused a longer-lasting infection in the skin and chronic systemic dissemination associated to more severe granulomatous lesions. Similar Th1/Th1-Th17/Tregs responses were induced by both S. brasiliensis and S. schenckii on 7th and 21st d.p.i but on 35 d.p.i a reduction of Th1 and Th1-Th17 cells, associated to higher values of Th17/Tregs cells was observed only in S. brasiliensis-infected mice. In summary, S. brasiliensis caused a more severe disease associated with sustained Th17/Tregs responses than S. schenckii in mice.

Comparative efficacy and toxicity of two vaccine candidates against Sporothrix schenckii using either Montanide™ Pet Gel A or aluminum hydroxide adjuvants in mice

Sporotrichosis is an important zoonosis in Brazil and the most frequent subcutaneous mycosis in Latin America, caused by different Sporothrix species. Currently, there is no effective vaccine available to prevent this disease. In this study, the efficacy and toxicity of the adjuvant Montanide™ Pet Gel A (PGA) formulated with S. schenckii cell wall proteins (ssCWP) was evaluated and compared with that of aluminum hydroxide (AH). Balb/c mice received two subcutaneous doses (1st and 14th days) of either the unadjuvanted or adjuvanted vaccine candidates. On the 21st day, anti-ssCWP antibody levels (ELISA), the phagocytic index, as well as the ex vivo release of IFN-γ, IL-4, and IL-17 by splenocytes and IL-12 by peritoneal macrophages were assessed. Cytotoxicity of the vaccine formulations was evaluated in vitro and by histopathological analysis of the inoculation site. Both adjuvanted vaccine formulations increased anti-ssCWP IgG, IgG1, IgG2a, and IgG3 levels, although IgG2a levels were higher in response to PGA+CWP100, probably contributing to the increase in S. schenckii yeast phagocytosis by macrophages in the opsonophagocytosis assay when using serum from PGA+CWP100-immunized mice. Immunization with AH+CWP100 led to a mixed Th1/Th2/Th17 ex vivo cytokine release profile, while PGA+CWP100 stimulated a preferential Th1/Th2 profile. Moreover, PGA+CWP100 was less cytotoxic in vitro, caused less local toxicity and led to a similar reduction in fungal load in the liver and spleen of S. schenckii- or S. brasiliensis-challenged mice as compared with AH+CWP100. These results suggest that PGA may be an effective and safe adjuvant for a future sporotrichosis vaccine.

Dectin-1 expression by macrophages and related antifungal mechanisms in a murine model of Sporothrix schenckii sensu stricto systemic infection

The available information about the role of Dectin-1 in sporotrichosis is scarce. Hence, we aimed to assess Dectin-1 expression by macrophages and the activation of some related antifungal mechanisms during the Sporothrix schenckii sensu stricto infection as a first attempt to elucidate the role of this receptor in sporotrichosis. Balb/c mice were intraperitoneally infected with S. schenckii sensu stricto yeast ATCC 16345 and euthanized on days 5, 10 and 15 post-infection, when the following parameters were evaluated: fungal burden in spleen, Dectin-1 expression and nitric oxide (NO) production by peritoneal macrophages, as well as IL-1β, TNF-α and IL-10 ex vivo secretion by these same cells. Peritoneal macrophages were ex vivo challenged with either the alkali-insoluble fraction (F1) extracted from the S. schenckii cell wall, a commercially available purified β-1,3-glucan or whole heat-killed S. schenckii yeasts (HKss). Additionally, a Dectin-1 antibody-mediated blockade assay was performed on day 10 post-infection to assess the participation of this receptor in cytokine secretion. Our results showed that Dectin-1 expression by peritoneal macrophages was augmented on days 10 and 15 post-infection alongside elevated NO production and ex vivo secretion of IL-10, TNF-α and IL-1β. The antibody-mediated blockade of Dectin-1 inhibited cytokine production in both infected and non-infected mice, mainly after β-1,3-glucan stimulation. Our results suggest a role for Dectin-1 in triggering the immune response during S. schenckii infection.

Anti-inflammatory activity of Vismia guianensis (Aubl.) Pers. extracts and antifungal activity against Sporothrix schenckii

ETHNOPHARMACOLOGICAL RELEVANCE

Vismia guianensis (Aubl.) Pers. is traditionally used in North and Northeast of Brazil for the treatment of dermatomycoses. Since the strategy associating immunomodulators with antifungal drugs seems to be promissory to improve the treatment efficacy in fungal infections, we aimed to investigate the antifungal activity of V. guianensis ethanolic extract of leaves (VGL) and bark (VGB) against Sporothrix schenckii ATCC 16345 and their antinflammatory activities.

MATERIAL AND METHODS

The extracts were analyzed by HPLC-DAD-IT MS/MS for in situ identification of major compounds. Antifungal activity was evaluated in vitro (microdilution test) and in vivo using a murine model of S. schenckii infection. The production of TNF-α, IFN-γ, IL-4, IL-10 and IL-12 by measured by ELISA, as well as measured the production and inhibition of the NO after treatment with the plant extracts or itraconazole (ITR).

RESULTS

Two O-glucosyl-flavonoids and 16 prenylated benzophenone derivatives already described for Vismia were detected. Both VGL and VGB showed significant antifungal activity either in in vitro assay of microdilution (MIC=3.9µg/mL) and in vivo model of infection with reduction of S. schenckii load in spleen. It was also observed a predominance of reduction in the production of NO and the proinflammatory cytokines evaluated except TNFα, but with stimulation of IL-10, as evidence of a potential anti-inflammatory effect associated.

CONCLUSION

The results showed that both VGL and VGB have a significant antifungal against S. schenckii and an anti-inflammatory activity. These results can support the use of these extracts for alternative treatment of sporotrichosis.