A novel black poplar propolis extract with promising health-promoting properties: focus on its chemical composition, antioxidant, anti-inflammatory, and anti-genotoxic activities

Propolis is a resinous mixture produced by honeybees which has been used since ancient times for its useful properties. However, its chemical composition and bioactivity may vary, depending on the geographical area of origin and the type of tree bees use for collecting pollen. In this context, this research aimed to investigate the total phenolic content (using the Folin-Ciocalteu assay) and the total antioxidant capacity (using the FRAP, DPPH, and ABTS assays) of three black poplar (Populus nigra L.) propolis (BPP) solutions (S1, S2, and S3), as well as the chemical composition (HPLC-ESI-MSn) and biological activities (effect on cell viability, genotoxic/antigenotoxic properties, and anti-inflammatory activity, and effect on ROS production) of the one which showed the highest antioxidant activity (S1). The hydroalcoholic BPP solution S1 was a prototype of an innovative, research-type product by an Italian nutraceutical manufacturer. In contrast, hydroalcoholic BPP solutions S2 and S3 were conventional products purchased from local pharmacy stores. For the three extracts, 50 phenolic compounds, encompassing phenolic acids and flavonoids, were identified. In summary, the results showed an interesting chemical profile and the remarkable antioxidant, antigenotoxic, anti-inflammatory and ROS-modulating activities of the innovative BPP extract S1, paving the way for future research. In vivo investigations will be a possible line to take, which may help corroborate the hypothesis of the potential health benefits of this product, and even stimulate further ameliorations of the new prototype.

Antimicrobial Oleogel Containing Sustainably Prepared Silver-Based Nanomaterials for Topical Application

Oleogels containing silica-silver-based nanomaterials were prepared to be used as potential antimicrobial treatment for preventing and curing skin infections. Fumed silica was used as a bifunctional excipient able to offer support to silver-based nanoparticle growth and act as a gelling agent for oleogel formulation. First, silica-silver composites were prepared following a sustainable method by contact of fumed silica and silver nitrate in the presence of ethanol and successive UV irradiation. The composites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), ATR FT-IR spectroscopy and UV-Vis spectrophotometry. The presence of 8-20 nm spherical nanoparticles, in addition to the silica aggregates and AgNO3 crystals, was detected. The composites showed good antimicrobial activity against the Gram-negative Pseudomonas aeruginosa and the Gram-positive bacteria Staphylococcus aureus and Staphylococcus epidermidis. Thus, they were formulated in an oleogel, obtained using fumed silica as a gelling agent. For comparison, oleogels containing AgNO3 were prepared according to two different formulative techniques. The silica-silver-based oleogels showed good antimicrobial activity and did not show cytotoxic effects for fibroblasts and keratinocytes.

Efficacy of Violet-Blue (405 nm) LED Lamps for Disinfection of High-Environmental-Contact Surfaces in Healthcare Facilities: Leading to the Inactivation of Microorganisms and Reduction of MRSA Contamination

Effective disinfection procedures in healthcare facilities are essential to prevent transmission. Chemical disinfectants, hydrogen peroxide vapour (HPV) systems and ultraviolet (UV) light are commonly used methods. An emerging method, violet-blue light at 405 nm, has shown promise for surface disinfection. Its antimicrobial properties are based on producing reactive oxygen species (ROS) that lead to the inactivation of pathogens. Studies have shown significant efficacy in reducing bacterial levels on surfaces and in the air, reducing nosocomial infections. The aim of this study was to evaluate the antimicrobial effectiveness of violet-blue (405 nm) LED lamps on high-contact surfaces in a hospital infection-control laboratory. High-contact surfaces were sampled before and after 7 days of exposure to violet-blue light. In addition, the effect of violet-blue light on MRSA-contaminated surfaces was investigated. Exposure to violet-blue light significantly reduced the number of bacteria, yeasts and moulds on the sampled surfaces. The incubator handle showed a low microbial load and no growth after irradiation. The worktable and sink showed an inconsistent reduction due to shaded areas. In the second experiment, violet-blue light significantly reduced the microbial load of MRSA on surfaces, with a greater reduction on steel surfaces than on plastic surfaces. Violet-blue light at 405 nm has proven to be an effective tool for pathogen inactivation in healthcare settings Violet-blue light shows promise as an additional and integrated tool to reduce microbial contamination in hospital environments but must be used in combination with standard cleaning practices and infection control protocols. Further research is needed to optimise the violet-blue, 405 nm disinfection method.

Ag/Ag3PO4 Nanoparticle-Decorated Hydroxyapatite Functionalized Calcium Carbonate: Ultrasound-Assisted Sustainable Synthesis, Characterization, and Antimicrobial Activity

Silver nanoparticles are usually prepared by the reduction of silver cations through chemical and non-sustainable procedures that involve the use of reducing chemical agents. Therefore, many efforts have been made in the search for sustainable alternative methods. Among them, an ultrasound-assisted procedure could be a suitable and sustainable method to afford well-dispersed and nanometric silver particles. This paper describes a sustainable, ultrasound-assisted method using citrate as a reducing agent to prepare silver@hydroxyapatite functionalized calcium carbonate composites. For comparison, an ultrasound-assisted reduction was performed in the presence of NaBH₄. The composites obtained in the presence of these two different reducing agents were compared in terms of nanoparticle nature, antimicrobial activity, and cytotoxic activity. The nanoparticle nature was investigated by several techniques, including X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy, UV-Vis spectroscopic measurements, and X-ray photoemission spectroscopy. Nanoparticles with a predominance of Ag or Ag₃PO₄ were obtained according to the type of reducing agent used. All composites were tested for antimicrobial and antibiofilm activities against Gram-positive and Gram-negative (Staphylococcus aureus and Pseudomonas aeruginosa, respectively) bacteria and for cytotoxicity towards human skin keratinocytes and human fibroblasts. The nature of the nanoparticles, Ag or Ag₃PO₄, and their predominance seemed to affect the in vitro silver release and the antimicrobial and antibiofilm activities. The composites obtained by the citrate-assisted reduction gave rise to the best results.

Alginate Ag/AgCl Nanoparticles Composite Films for Wound Dressings with Antibiofilm and Antimicrobial Activities

Recently, silver-based nanoparticles have been proposed as components of wound dressings due to their antimicrobial activity. Unfortunately, they are cytotoxic for keratinocytes and fibroblasts, and this limits their use. Less consideration has been given to the use of AgCl nanoparticles in wound dressings. In this paper, a sustainable preparation of alginate AgCl nanoparticles composite films by simultaneous alginate gelation and AgCl nanoparticle formation in the presence of CaCl₂ solution is proposed with the aim of obtaining films with antimicrobial and antibiofilm activities and low cytotoxicity. First, AgNO₃ alginate films were prepared, and then, gelation and nanoparticle formation were induced by film immersion in CaCl₂ solution. Films characterization revealed the presence of both AgCl and metallic silver nanoparticles, which resulted as quite homogeneously distributed, and good hydration properties. Finally, films were tested for their antimicrobial and antibiofilm activities against Staphylococcus epidermidis (ATCC 12228), Staphylococcus aureus (ATCC 29213), Pseudomonas aeruginosa (ATCC 15692), and the yeast Candida albicans. Composite films showed antibacterial and antibiofilm activities against the tested bacteria and resulted as less active towards Candida albicans. Film cytotoxicity was investigated towards human dermis fibroblasts (HuDe) and human skin keratinocytes (NCTC2544). Composite films showed low cytotoxicity, especially towards fibroblasts. Thus, the proposed sustainable approach allows to obtain composite films of Ag/AgCl alginate nanoparticles capable of preventing the onset of infections without showing high cytotoxicity for tissue cells.

Drug efflux transporters in Staphylococcus pseudintermedius: in silico prediction and characterization of resistance

OBJECTIVES

To perform an in silico prediction of drug efflux pumps (EPs) in Staphylococcus pseudintermedius and investigate their role in conferring resistance to antibiotic and biocidal agents and biofilm formation.

METHODS

A S. pseudintermedius efflux mutant was obtained by stimulating an isogenic line (ATCC 49444) with increasing concentrations of an efflux system substrate. Changes in antimicrobial susceptibility and biofilm-forming capability were evaluated in the presence/absence of the EP inhibitors (EPIs) thioridazine and reserpine and the efflux activity was assayed by fluorometry. Homologues of EPs of Staphylococcus aureus and Staphylococcus epidermidis were searched by exploratory GenBank investigations. Gene expression analyses and sequencing were then conducted on selected genes.

RESULTS

Susceptibility to chlorhexidine, gentamicin and ciprofloxacin, but not enrofloxacin, was affected by the increased efflux and it was variably restored by the EPIs. The efflux mutant showed much greater biofilm formation that the original strain, which was significantly inhibited by thioridazine and reserpine at MIC/2. A high expression of norA, which was mgrA-independent, was found in the S. pseudintermedius efflux mutant, apparently regulated by an 11 bp deletion in its promoter region, whilst lmrB was transitorily overexpressed. icaA, which encodes the polysaccharide intercellular adhesin forming the extracellular matrix of staphylococcal biofilm, was also up-regulated.

CONCLUSIONS

EPs, particularly NorA, are supposed to have complex involvement in multiple stages of resistance development. Overexpression of EPs appears to be correlated with a remarkable increase of S. pseudintermedius biofilm production; however, the regulatory mechanisms remain to be explored.

Bud-Poplar-Extract-Embedded Chitosan Films as Multifunctional Wound Healing Dressing

Wounds represent a major global health challenge. Acute and chronic wounds are sensitive to bacterial infection. The wound environment facilitates the development of microbial biofilms, delays healing, and promotes chronic inflammation processes. The aim of the present work is the development of chitosan films embedded with bud poplar extract (BPE) to be used as wound dressing for avoiding biofilm formation and healing delay. Chitosan is a polymer with antimicrobial and hydrating properties used in wound dressing, while BPE has antibacterial, antioxidative, and anti-inflammatory properties. Chitosan-BPE films showed good antimicrobial and antibiofilm properties against Gram-positive bacteria and the yeast Candida albicans. BPE extract induced an immunomodulatory effect on human macrophages, increasing CD36 expression and TGFβ production during M1/M2 polarization, as observed by means of cytofluorimetric analysis and ELISA assay. Significant antioxidant activity was revealed in a cell-free test and in a human neutrophil assay. Moreover, the chitosan-BPE films induced a good regenerative effect in human fibroblasts by in vitro cell migration assay. Our results suggest that chitosan-BPE films could be considered a valid plant-based antimicrobial material for advanced dressings focused on the acceleration of wound repair.

Overcoming Antibiotic Resistance: Playing the 'Silver Nanobullet' Card

Enhancing the antibacterial activity of old antibiotics by a multitarget approach, such as combining antibiotics with metal nanoparticles, is a valuable strategy to overcome antibacterial resistance. In this work, the synergistic antimicrobial effect of silver nanoparticles and antibiotics, immobilized on a solid support, was investigated. Nanometric layered double hydroxides (LDH) based on Zn(II) and Al(III) were prepared by the double microemulsion technique. The dual function of LDH as an anionic exchanger and support for metal nanoparticles was exploited to immobilize both silver and antibiotics. Cefazolin (CFZ), a β-lactam, and nalidixic acid (NAL), a quinolone, were selected and intercalated into LDH obtaining ZnAl-CFZ and ZnAl-NAL samples. These samples were used for the growth of silver nanoparticles with dimension ranging from 2.5 to 8 nm. Silver and antibiotics release profiles, from LDH loaded with antibiotics and Ag/antibiotics, were evaluated in two different media: water and phosphate buffer. Interestingly, the release profiles are affected by both the acceptor media and the presence of silver. The synergistic antibacterial activity of LDH containing both silver and antibiotics were investigated on gram-positives (Staphylococcus aureus and Streptococcus pneumoniae) and gram-negatives (Pseudomonas aeruginosa) and compared with the plain antimicrobials and LDH containing only antibiotics or silver.

Effect of a UV-C Automatic Last-Generation Mobile Robotic System on Multi-Drug Resistant Pathogens

Background: Healthcare-associated infections caused by multi-drug resistant (MDR) pathogens are associated with increased mortality and morbidity among hospitalized patients. Inanimate surfaces, and in particular high-touch surfaces, have often been described as the source for outbreaks of nosocomial infections. The present work aimed to evaluate the efficacy of a last-generation mobile (robotic) irradiation UV-C light device R2S on MDR microorganisms in inanimate surfaces and its translation to hospital disinfection. Methods: The efficacy of R2S system was evaluated in environmental high-touch surfaces of two separate outpatient rooms of Perugia Hospital in Italy. The static UV-C irradiation effect was investigated on both the bacterial growth of S. aureus, MRSA, P. aeruginosa, and K. pneumoniae KPC and photoreactivation. The antimicrobial activity was also tested on different surfaces, including glass, steel, and plastic. Results: In the environmental tests, the R2S system decreased the number of bacteria, molds, and yeasts of each high-touch spot surface (HTSs) compared with manual sanitization. UV-C light irradiation significantly inhibits in vitro bacterial growth, also preventing photoreactivation. UV-C light bactericidal activity on MDR microorganisms is affected by the type of materials of inanimate surfaces. Conclusions: The last-generation mobile R2S system is a more reliable sanitizing procedure compared with its manual counterpart.

Solid State Photoreduction of Silver on Mesoporous Silica to Enhance Antifungal Activity

A solid-state Ultraviolet-photoreduction process of silver cations to produce Ag0 nanostructures on a mesoporous silica is presented as an innovative method for the preparation of efficient environmental anti-fouling agents. Mesoporous silica powder, contacted with AgNO3, is irradiated at 366 nm, where silica surface defects absorb. The detailed characterization of the materials enables us to document the silica assisted photo-reduction. The appearance of a Visible (Vis) band centered at 470 nm in the extinction spectra, due to the surface plasmon resonance of Ag0 nanostructures, and the morphology changes observed in transmission electron microscopy (TEM) images, associated with the increase of Ag/O ratio in energy dispersive X-ray (EDX) analysis, indicate the photo-induced formation of Ag0. The data demonstrate that the photo-induced reduction of silver cation occurs in the solid state and takes place through the activation of silica defects. The activation of the materials after UV-processing is then tested, evaluating their antimicrobial activity using an environmental filamentous fungus, Aspergillus niger. The treatment doubled inhibitory capacity in terms of minimal inhibitory concentration (MIC) and biofilm growth. The antimicrobial properties of silver-silica nanocomposites are investigated when dispersed in a commercial sealant; the nanocomposites show excellent dispersion in the silicon and improve its anti-fouling capacity.

Ethidium bromide exposure unmasks an antibiotic efflux system in Rhodococcus equi

BACKGROUND

This study introduces a newly created strain (Rhodococcus equiEtBr25) by exposing R. equi ATCC 33701 to ethidium bromide (EtBr), a substrate for MDR transporters. Such an approach allowed us to investigate the resulting phenotype and genetic mechanisms underlying the efflux-mediated resistance in R. equi.

METHODS

R. equi ATCC 33701 was stimulated with increasing concentrations of EtBr. The antimicrobial susceptibility of the parental strain and R. equiEtBr25 was investigated in the presence/absence of efflux pump inhibitors (EPIs). EtBr efflux was evaluated by EtBr-agar method and flow cytometry. The presence of efflux pump genes was determined by conventional PCR before to quantify the expression of 30 genes coding for membrane transporters by qPCR. The presence of erm(46) and mutations in 23S rRNA, and gyrA/gyrB was assessed by PCR and DNA sequencing to exclude the occurrence of resistance mechanisms other than efflux.

RESULTS

R. equi EtBr25 showed an increased EtBr efflux. Against this strain, the activity of EtBr, azithromycin and ciprofloxacin was more affected than that of rifampicin and azithromycin/rifampicin combinations. Resistances were reversed by combining the antimicrobials with EPIs. Gene expression analysis detected a marked up-regulation of REQ_RS13460 encoding for a Major Facilitator Superfamily (MFS) transporter. G→A transition occurred in the transcriptional repressor tetR/acrR adjacent to REQ_RS13460.

CONCLUSIONS

Exposure of R. equi to EtBr unmasked an efflux-mediated defence against azithromycin and ciprofloxacin, which seemingly correlates with the overexpression of a specific MFS transporter. This genotype may mirror an insidious low-level resistance of clinically important isolates that could be countered by EPI-based therapies.

Bioinspired Reactive Interfaces Based on Layered Double Hydroxides-Zn Rich Hydroxyapatite with Antibacterial Activity

This work is focused on the preparation and multi-technique characterization of potentially biocompatible reactive interfaces obtained by combining layered double hydroxides (LDHs) and hydroxyapatite (HA). Antimicrobial and osteoinductive metallic ions as Zn²⁺ and Ga³⁺ were chosen as intralayer constituents of LDH to obtain ZnAl and ZnAlGa systems. These LDHs, exchanged with dihydrogenphosphate anions, promoted the precipitation of HA on the LDH surface yielding HA@LDH composites. X-ray diffraction quantitative analysis, through the Rietveld refinement method, coupled with elemental analysis and micro-Raman spectroscopy showed the formation of a mixed Ca-Zn HA phase. Scanning electron microscopy revealed that HA, in the presence of LDH, grew preferentially along its a-axis, thus crystallizing mainly in the form of flake crystals. LDH and HA@LDH composites showed antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa at not cytotoxic concentrations for human osteoblasts (hFob 1.19), especially when Ga cations were present in the LDH structure. The effect of the presence of HA in the composites on the bone-bonding ability and on human osteoblast proliferation was also investigated. The HA seemed to reduce the toxicity of the LDH toward human osteoblast while did not affect the bone-bonding ability. This multidisciplinary study provides the bio-chemical, structural characterization of new LDH and HA@LDH composites, evaluating also their bioactivity to be potentially applicable to titanium-based prostheses.

Evaluation of Lumipulse® G SARS-CoV-2 antigen assay automated test for detecting SARS-CoV-2 nucleocapsid protein (NP) in nasopharyngeal swabs for community and population screening

Objectives

To compare the Lumipulse® SARS-CoV-2 antigen test with the gold standard real-time reverse transcription-polymerase chain reaction (RT-PCR) for diagnosis of SARS-CoV-2 infection and to evaluate its role in screening programs.

Methods

Lumipulse® SARS-CoV-2 antigen assay was compared with the gold standard RT-PCR test in a selected cohort of 226 subjects with suspected SARS-CoV-2 infection, and its accuracy was evaluated. Subsequently, the test was administered to a real-life screening cohort of 1738 cases. ROC analysis was performed to explore test features and cutoffs. All tests were performed in the regional reference laboratory in Umbria, Italy.

Results

A 42.0% positive result at RT-PCR was observed in the selected cohort. The Lumipulse® system showed 92.6% sensitivity (95% CI 85.4–97.0%) and 90.8% specificity (95% CI 84.5–95.2%) at 1.24 pg/mL optimal cutoff. In the screening cohort, characterized by 5.2% prevalence of infection, Lumipulse® assay showed 100% sensitivity (95% CI 96.0–100.0%) and 94.8% specificity (95% CI 93.6–95.8%) at 1.645 pg/mL optimal cutoff; the AUC was 97.4%, NPV was 100% (95% CI 99.8–100.0%) and PPV was 51.1% (95% CI 43.5–58.7%).

Conclusions

The Lumipulse® SARS-CoV-2 antigen assay can be safely employed in the screening strategies in small and large communities and in the general population.

Accelerate Pheno™ blood culture detection system: a literature review

Accelerate Pheno™ (ACC) is a fully automated system providing rapid identification of a panel of bacteria and yeasts, and antimicrobial susceptibility testing of common bacterial pathogens responsible for bloodstream infections and sepsis. Diagnostic accuracy for identification ranges from 87.9 to 100%, and antimicrobial susceptibility testing categorical agreement is higher than 91%. The present review includes peer-reviewed studies on ACC published to date. Both interventional and hypothetical studies evidenced the potential positive clinical role of ACC in the management and therapy of patients with bloodstream infections and sepsis, due to the important reduction in time to report, suggesting a crucial impact on the therapeutic management of these patients, provided the presence of a hospital antimicrobial stewardship program, a 24/7 laboratory operating time and a strict collaboration between clinical microbiologist and clinician. Further prospective multicenter studies are necessary to explore the impact of this system on mortality, length of stay and spread of multidrug-resistant organisms.

C-2 phenyl replacements to obtain potent quinoline-based Staphylococcus aureus NorA inhibitors

NorA is the most studied efflux pump of Staphylococcus aureus and is responsible for high level resistance towards fluoroquinolone drugs. Although along the years many NorA efflux pump inhibitors (EPIs) have been reported, poor information is available about structure-activity relationship (SAR) around their nuclei and reliability of data supported by robust assays proving NorA inhibition. In this regard, we focussed efforts on the 2-phenylquinoline as a promising chemotype to develop potent NorA EPIs. Herein, we report SAR studies about the introduction of different aryl moieties on the quinoline C-2 position. The new derivative 37a showed an improved EPI activity (16-fold) with respect to the starting hit 1. Moreover, compound 37a exhibited a high potential in time-kill curves when combined with ciprofloxacin against SA-1199B (norA+). Also, 37a exhibited poor non-specific effect on bacterial membrane polarisation and showed an improvement in terms of “selectivity index” in comparison to 1.

2-Phenylquinoline S. aureus NorA Efflux Pump Inhibitors: Evaluation of the Importance of Methoxy Group Introduction

Antimicrobial resistance (AMR) represents a hot topic in drug discovery. Besides the identification of new antibiotics, the use of nonantibiotic molecules to block resistance mechanisms is a powerful alternative. Bacterial efflux pumps exert an early step in AMR development by allowing bacteria to grow at subinhibitorial drug concentrations. Thus, efflux pump inhibitors (EPIs) offer a great opportunity to fight AMR. Given our experience in developing Staphylococcus aureus NorA EPIs, in this work, starting from the 2-phenylquinoline hit 1, we planned the introduction of methoxy groups on the basis of their presence in known NorA EPIs. Among the 35 different synthesized derivatives, compounds 3b and 7d exhibited the best NorA inhibition activity by restoring at very low concentrations ciprofloxacin MICs against resistant S. aureus strains. Interestingly, both compounds displayed EPI activities at nontoxic concentrations for human cells as well as highlighted promising results by preliminary pharmacokinetic studies.

Anti-inflammatory effect of multistrain probiotic formulation (L. rhamnosus, B. lactis, and B. longum)

OBJECTIVE

In recent years, a great number of studies have been directed toward the evaluation of gastrointestinal microbiota modulation through the introduction of beneficial microorganisms, also known as probiotics. Many studies have highlighted how this category of bacteria is very important for the good development, functioning, and maintenance of our immune system. There is a delicate balance between the immune system, located under the gut epithelial barrier, and the microbiota, but many factors can induce a disequilibrium that leads to an inflammatory state and dysbiosis. The aim of this work is to verify the anti-inflammatory effects of a probiotic formulation of Lactobacillus rhamnosus, Bifidobacterium lactis, and Bifidobacterium longum (Serobioma).

METHODS

To mimic the natural host compartmentalization between probiotics and immune cells through the intestinal epithelial barrier in vitro, the transwell model was used. We focused on a particular subset of immune cells that play a key role in the mucosal immune system. The immunomodulatory effects of probiotic formulation were investigated in the human macrophage cell line THP1 and macrophages derived from ex vivo human peripheral blood mononuclear cells.

RESULTS

Probiotic formulation induced a significant increase in anti-inflammatory cytokine interleukin-10 (IL-10) production and was able to decrease the secretion of the major proinflammatory cytokines IL-1β and IL-6 by 70% and 80%, respectively. Finally, for the first time, the ability of probiotic formulation to favor the macrophage M2 phenotype has been identified.

CONCLUSION

The transwell model is an intriguing toll approach to studying the human epithelial barrier.

Pharmacophore-Based Repositioning of Approved Drugs as Novel Staphylococcus aureus NorA Efflux Pump Inhibitors

An intriguing opportunity to address antimicrobial resistance is represented by the inhibition of efflux pumps. Focusing on NorA, the most important efflux pump of Staphylococcus aureus, an efflux pump inhibitors (EPIs) library was used for ligand-based pharmacophore modeling studies. By exploitation of the obtained models, an in silico drug repositioning approach allowed for the identification of novel and potent NorA EPIs.

Investigation on the effect of known potent S. aureus NorA efflux pump inhibitors on the staphylococcal biofilm formation

The emergence of multidrug resistant microorganisms has triggered the impending need of developing effective antibacterial strategies.

Diphenyl diselenide derivatives inhibit microbial biofilm formation involved in wound infection

Background

Organoselenium compounds have antimicrobial activity against some bacteria and fungi; furthermore, the antioxidant activity of diselenides has been demonstrated. The aim of the present work was to examine the in vitro minimal inhibitory concentration of a panel of differently substituted diselenides and their effectiveness in inhibiting biofilm formation and dispersing preformed microbial biofilm of Staphylococcus epidermidis, Staphylococcus aureus, Streptococcus pyogenes and Pseudomonas aeruginosa and the yeast Candida albicans, all involved in wound infections. Moreover, the cytotoxicity of the compounds was determined in human dermal fibroblast and keratinocytes. In closing, we tested their direct antioxidant activity.

Results

Diselenides showed different antimicrobial activity, depending on the microorganism. All diselenides demonstrated a good antibiofilm activity against S. aureus and S. epidermidis, the compounds camphor diselenide, bis[ethyl-N-(2’-selenobenzoyl) glycinate] and bis[2’-seleno-N-(1-methyl-2-phenylethyl) benzamide] were active against S. pyogenes and C. albicans biofilm while only diselenides 2,2’-diselenidyldibenzoic acid and bis[ethyl-N-(2’-selenobenzoyl) glycinate] were effective against P. aeruginosa. Moreover, the compounds bis[ethyl-N-(2’-selenobenzoyl) glycinate] and bis[2’-seleno-N-(1-methyl-2-phenylethyl) benzamide] showed an antioxidant activity at concentrations lower than the 50 % of cytotoxic concentration.

Conclusions

Because microbial biofilms are implicated in chronic infection of wounds and treatment failure, the combination of antimicrobial activity and potential radical scavenging effects may contribute to the improvement of wound healing. Therefore, this study suggests that bis[ethylN-(2’-selenobenzoyl) glycinate] and bis[2’-seleno-N-(1-methyl-2-phenylethyl) benzamide] are promising compounds to be used in preventing and treating microbial wound infections.

Carboxymethylcellulose films containing chlorhexidine–zirconium phosphate nanoparticles: antibiofilm activity and cytotoxicity

Hybrid composite films of carboxymethylcellulose and chlorhexidine intercalated nanosized zirconium phosphate result able to reduce the formation of biofilms on wound surface.

Chlorhexidine-loaded functionalized mesoporous MCM-41 poly(methylmethacrylate) based composites with Candida antibiofilm activity

The complete or partial dentures made of acrylic resins or composites constitute the support for Candida biofilm with consequent onset of stomatitis and candidiasis.

Reaction kinetics and targeting to cellular glutathione S-transferase of the glutathione peroxidase mimetic PhSeZnCl and its D,L-polylactide microparticle formulation

Catalytic properties and cellular effects of the glutathione peroxidase (GPx)-mimetic compound PhSeZnCl or its d,l-lactide polymer microencapsulation form (M-PhSeZnCl) were investigated and compared with the prototypical Se-organic compounds ebselen and diselenide (PhSe)2. PhSeZnCl was confirmed to catalyze the ping-pong reaction of GPx with higher Vmax than ebselen and (PhSe)2, but the catalytic efficiency calculated for the cosubstrates glutathione (GSH) and H2O2, and particularly the high reactivity against thiols (lowest KM for GSH in the series of test molecules), suggested poor biological applicability of PhSeZnCl as a GPx mimetic. Cytotoxicity of PhSeZnCl was demonstrated in various cancer cell lines via increased reactive oxygen species (ROS) generation, depletion of intracellular thiols, and induction of apoptosis. Experiments carried out in GSH S-transferase P (GSTP)-overexpressing K562 human erythroleukemia cells and in GSTP1-1-knockout murine embryonic fibroblasts (MEFs) demonstrated that this cytosolic enzyme represents a preferential target of the redox disturbances produced by this Se-compound with a key role in controlling H2O2 generation and the perturbation of stress/survival kinase signaling. Microencapsulation was adopted as a strategy to control the thiol reactivity and oxidative stress effects of PhSeZnCl, then assessing applications alternative to anticancer. The uptake of this "depowered" GPx-mimetic formulation, which occurred through an endocytosis-like mechanism, resulted in a marked reduction of cytotoxicity. In MCF-7 cells transfected with different allelic variants of GSTP, M-PhSeZnCl lowered the burst of cellular ROS induced by the exposure to extracellular H2O2, and the extent of this effect changed between the GSTP variants. Microencapsulation is a straightforward strategy to mitigate the toxicity of thiol-reactive Se-organic drugs that enhanced the antioxidant and cellular protective effects of PhSeZnCl. A mechanistic linkage of these effects with the expression pattern and signaling properties of GSTP . This has overcome the GPx-mimetic paradigm proposed for Se-organic drugs with a more pragmatic concept of GSTP signaling modulators.

Secreted aspartic proteases of Candida albicans activate the NLRP3 inflammasome

In a recent report, we demonstrated that distinct members of the secreted aspartic protease (Sap) family of Candida albicans are able to induce secretion of proinflammatory cytokines by human monocytes, independently of their proteolytic activity and specific pH optima. In particular, C. albicans Sap2 and Sap6 potently induced IL-1β, TNF-α, and IL-6 production. Here, we demonstrate that Sap2 and Sap6 proteins trigger IL-1β and IL-18 production through inflammasome activation. This occurs via NLRP3 and caspase-1 activation, which cleaves pro-IL-1β into secreted bioactive IL-1β, a cytokine that was induced by Saps in monocytes, in monocyte-derived macrophages and in dendritic cells. Downregulation of NLRP3 by RNA interference strongly reduced the secretion of bioactive IL-1β. Inflammasome activation required Sap internalization via a clathrin-dependent mechanism, intracellular induction of K(+) efflux, and ROS production. Inflammasome activation of monocytes induced by Sap2 and Sap6 differed from that induced by LPS-ATP in several aspects. Our data reveal novel immunoregulatory mechanisms of C. albicans and suggest that Saps contribute to the pathogenesis of candidiasis by fostering rather than evading host immunity.

Mouse strain-dependent differences in estrogen sensitivity during vaginal candidiasis

The animal models available for studying the immune response to genital tract infection require induction of a pseudo estrous state, usually achieved by administration of 17-β-estradiol. In our experimental model of vaginal candidiasis, under pseudo estrus, different strains of mice were used. We observed major differences in the clearance of Candida albicans infection among the different strains, ascribable to differing susceptibility to estradiol treatment. In the early phase of infection CD1, BALB/c, C57BL/6 albino and C57BL/6 mice were colonized to similar levels, while in the late phase of infection, BALB/c mice, which are considered genetically resistant to C. albicans infection, exhibited greater susceptibility to vaginal candidiasis than CD1 and C57BL/6 albino strains of mice. This was because estradiol induced "per se" enlarged and fluid-filled uteri, more pronounced in infected mice and consistently more evident in BALB/c and C57BL/6 mice than in CD1 mice. Unlike CD1, BALB/c and C57BL/6 mice showed a heavy fungal colonization of the uterus, even though C57BL/6 mice apparently cleared C. albicans from the vagina. The presence of C. albicans in the vagina and uterus was accompanied by a heavy bacterial load. Collectively these observations prompted us to carry out a careful analysis of estradiol effects in a mouse model of vaginal infection.

New approaches in the development of a vaccine for mucosal candidiasis: progress and challenges

The commensal fungus Candida albicans causes mucosal candidiasis in the rapidly expanding number of immunocompromised patients. Mucosal candidiasis includes oropharyngeal, esophageal, gastrointestinal, and vaginal infections. Vulvovaginal candidiasis (VVC) and antimycotic-refractory recurrent VVC is a frequent problem in healthy childbearing women. Both these mucosal infections can affect the quality of life and finding new therapeutical and preventive approaches is a challenge. A vaccine against candidal infections would be a new important tool to prevent and/or cure mucosal candidiasis and would be of benefit to many patients. Several Candida antigens have been proposed as vaccine candidates including cell wall components and virulence factors. Here we discuss the recent progress and problems associated with vaccination against mucosal candidiasis.

A luciferase reporter for gene expression studies and dynamic imaging of superficial Candida albicans infections

Real-time imaging of fungal infections is becoming integral to the study of host-pathogen interactions, as it allows monitoring of the spatial and temporal progression of pathogen growth or of the host response in a single animal as well as reducing the number of animals used to obtain significant data. We present different applications of a novel luciferase reporter gene constructed from the coding sequences of the Candida albicans PGA59 gene, encoding a GPI-linked cell wall protein, and the Gaussia princeps luciferase gene. Upon addition of the coelenterazine substrate, light produced by the surface-exposed luciferase can be used to quantify gene expression from a variety of C. albicans promoters as well as monitoring cutaneous, subcutaneous, and vaginal infections.

Beneficial effect of Mentha suaveolens essential oil in the treatment of vaginal candidiasis assessed by real-time monitoring of infection

Background

Vaginal candidiasis is a frequent and common distressing disease affecting up to 75% of the women of fertile age; most of these women have recurrent episodes. Essential oils from aromatic plants have been shown to have antimicrobial and antifungal activities. This study was aimed at assessing the anti-fungal activity of essential oil from Mentha suaveolens (EOMS) in an experimental infection of vaginal candidiasis.

Methods

The in vitro and in vivo activity of EOMS was assessed. The in vitro activity was evaluated under standard CLSI methods, and the in vivo analysis was carried out by exploiting a novel, non-invasive model of vaginal candidiasis in mice based on an in vivo imaging technique.

Differences between essential oil treated and saline treated mice were evaluated by the non-parametric Mann-Whitney U-test. Viable count data from a time kill assay and yeast and hyphae survival test were compared using the Student's t-test (two-tailed).

Results

Our main findings were: i) EOMS shows potent candidastatic and candidacidal activity in an in vitro experimental system; ii) EOMS gives a degree of protection against vaginal candidiasis in an in vivo experimental system.

Conclusions

This study shows for the first time that the essential oil of a Moroccan plant Mentha suaveolens is candidastatic and candidacidal in vitro, and has a degree of anticandidal activity in a model of vaginal infection, as demonstrated in an in vivo monitoring imaging system. We conclude that our findings lay the ground for further, more extensive investigations to identify the active EOMS component(s), promising in the therapeutically problematic setting of chronic vaginal candidiasis in humans.

A beta-glucan-conjugate vaccine and anti-beta-glucan antibodies are effective against murine vaginal candidiasis as assessed by a novel in vivo imaging technique

The protective capacity of a parenterally administered beta-glucan-conjugate vaccine formulated with the human-compatible MF59 adjuvant was assessed in a murine model of vaginal candidiasis. To monitor infection, an in vivo imaging technique exploiting genetically engineered, luminescent Candida albicans was adopted, and compared with measurements of colony forming units. The vaccine conferred significant protection, and this was associated with production of serum and vaginal anti-beta-glucan IgG antibodies. Vaginal IgG molecules were the likely mediators of protection as inferred by the efficacy of passive transfer of immune vaginal fluid and passive protection by an anti-beta-1,3-glucan mAb. Overall, the in vivo imaging technique was more reliable than vaginal CFU counts in assessing the extent and duration of the vaginal infection, and the consequent protection level.

An anti-beta-glucan monoclonal antibody inhibits growth and capsule formation of Cryptococcus neoformans in vitro and exerts therapeutic, anticryptococcal activity in vivo

In this study we tested the in vitro and in vivo anti-Cryptococcus neoformans activity of an antilaminarin (anti-beta-glucan) monoclonal antibody (MAb 2G8) (immunoglobulin G2b) which was previously shown to inhibit the growth of beta-glucan-exposing Candida albicans cells. Here we show that MAb 2G8 binds to the cell wall of C. neoformans and inhibits its growth to an extent comparable to that observed for C. albicans. Binding and growth inhibition were detected almost equally for encapsulated and acapsular C. neoformans strains. In addition, at subinhibitory concentrations, MAb 2G8 reduced the capsule thickness without affecting protease or phospholipase production. Acapsular fungal cells, but not encapsulated fungal cells, were opsonized by the antibody and more efficiently phagocytosed and killed by human monocytes and by murine peritoneal macrophages. A single administration of MAb 2G8 resulted in a reduction in the fungal burden in the brains and livers of mice systemically infected with a highly virulent, encapsulated C. neoformans strain. This protective effect was also detected in neutropenic mice. Overall, these findings demonstrate that cell wall beta-glucan of encapsulated C. neoformans is accessible to antibodies which can exert remarkable anticryptococcal activities in vitro and in vivo.

Candida albicans mannoprotein influences the biological function of dendritic cells

Cell wall components of fungi involved in induction of host immune response are predominantly proteins and glycoproteins, the latter being mainly mannoproteins (MP). In this study we analyse the interaction of the MP from Candida albicans (MP65) with dendritic cells (DC) and demonstrate that MP65 stimulates DC and induces the release of TNF-alpha, IL-6 and the activation of IL-12 gene, with maximal value 6 h post treatment. MP65 induces DC maturation by increasing costimulatory molecules and decreasing CD14 and FcgammaR molecule expression. The latter effect is partly mediated by toll-like receptor 2 (TLR2) and TLR4, and the MyD88-dependent pathway is involved in the process. MP65 enables DC to activate T cell response, its protein core is essential for induction of T cell activation, while its glycosylated portion primarily promotes cytokine production. The mechanisms involved in induction of protective response against C. albicans could be mediated by the MP65 antigen, suggesting that MP65 may be a suitable candidate vaccine.

Design, synthesis, and microbiological evaluation of new Candida albicans CYP51 inhibitors

In a program aimed at the design and synthesis of novel azole inhibitors of Candida albicans CYP51 (CA-CYP51), a series of azole 1,4-benzothiazines (BT) and 1,4-benzoxazines (BO) were recently synthesized. A morphological study of the enzyme active site highlighted a hydrophobic access channel, and a docking study pointed out that the C-2 position of the BT or BO nucleus was oriented toward the access channel. Here, we report the design, synthesis, and microbiological evaluation of C-2-alkyl BT and BO compounds. In both series, introduction of the alkyl chain maintained and in some cases improved the anti-Candida in vitro activity; however, there was not always a strict correlation between in vitro and in vivo activity for several compounds.

Mannoproteins from Cryptococcus neoformans promote dendritic cell maturation and activation

Our previous data show that mannoproteins (MPs) from Cryptococcus neoformans are able to induce protective responses against both C. neoformans and Candida albicans. Here we provide evidence that MPs foster maturation and activation of human dendritic cells (DCs). Maturation was evaluated by the ability of MPs to facilitate expression of costimulatory molecules such as CD40, CD86, CD83, and major histocompatibility complex classes I and II and to inhibit receptors such as CD14, CD16, and CD32. Activation of DCs was measured by the capacity of MPs to promote interleukin-12 and tumor necrosis factor alpha secretion. DC-induced maturation and interleukin-12 induction are largely mediated by engagement of mannose receptors and presume MP internalization and degradation. DC activation leads to IkappaBalpha phosphorylation, which is necessary for nuclear factor kappaB transmigration into the nucleus. MP-loaded DCs are efficient stimulators of T cells and show a remarkable capacity to promote CD4 and CD8 proliferation. In conclusion, we have evidenced a novel regulatory role of MPs that promotes their candidacy as a vaccine against fungi.

An early imbalance of interleukin 12 influences the adjuvant effect of mannoproteins of Cryptococcus neoformans

Mannoprotein from Cryptococcus neoformans induces protective response against a lethal challenge with this fungus or with Candida albicans. This phenomenon is largely related to early production of interleukin 12 (IL-12) and induction of T helper 1 response. Our study assesses whether the early absence of this critical cytokine could account for the incomplete activation of cellular response and whether the immune system compensates this imbalance. The results show that the neutralization of early IL-12 enhanced IL-18 production but decreased IFN-gamma secretion and IL-12R expression by splenic CD4 T cells. In contrast, IL-18R was not augmented despite an increase in IL-18 production. The co-stimulatory pathway was partially dysregulated because splenic macrophages showed unmodified B7-2, and a decrease of B7-1 expression. This dysregulation led to incomplete proliferative response of T cells in response to Cryptococcus neoformans and to increased fungal load in the brain 21 days post infection. The inability to dispose early IL-12, forced the immune system to compensate the imbalance and produced a series of long-lasting dysregulations involving the co-stimulatory pathway and T cell activation.

Glucuronoxylomannan, a microbial compound, regulates expression of costimulatory molecules and production of cytokines in macrophages

Glucuronoxylomannan (GXM) is a microbial compound that can modulate the immune response. We investigated (1) the receptors involved in uptake of GXM on monocyte-derived macrophages (MDMs) from healthy donors, (2) the effects of GXM on expression of specific receptors, (3) the effects of GXM mediated by pattern-recognition receptors, and (4) GXM modulation of MDM accessory and secretory functions. Cellular receptors involved in uptake of GXM included Fc gamma RII, CD18, Toll-like receptor (TLR) 4, and CD14. Some biological functions of MDMs were profoundly affected by treatment with GXM, resulting in (1) increased expression of CD40 and CD86 via perturbation of TLR4, (2) decreased expression of major histocompatibility complex class II, (3) induction of interleukin-10 but not of tumor necrosis factor-alpha, and (4) decreased lipopolysaccharide (LPS)-induced production of cytokines. GXM represents an attractive compound to limit inflammatory processes and induce an LPS-tolerant state.

Disruption of CD40/CD40L interaction influences the course of Cryptococcus neoformans infection

CD40 signaling has been implicated in various pathogenic processes such as chronic inflammatory disease, graft-versus-host disease, autoimmune disease and cancer. We previously demonstrated in an in vitro system that the CD40/CD40L pathway mediates late interleukin (IL) 12 production in response to Cryptococcus neoformans. The purpose of this study was to examine the course of C. neoformans infection in the absence of CD40/CD40L costimulation. We compared infection in mice genetically lacking CD40L (CD40L(-/-)) and in the wild-type counterpart. The animals were injected intratracheally with C. neoformans and monitored for clearance of the organism and the development of cellular immune response. CD40L(-/-) mice exhibited an exacerbation of infection, evaluated as scarce inflammatory response in the lung, that mirrored an increase of fungal burden. This correlated with impairment of nitrite production and antimicrobial activity by macrophages against C. neoformans and unrelated microorganisms such as Candida albicans. Moreover, IL-12 production by splenic macrophages was diminished in CD40L(-/-) mice and interferon-gamma production by CD4 and CD8 T cells was decreased. CD4 T cells retained the ability to express a costimulatory molecule, CTLA-4, but showed a decrease in CD28 expression. This latter molecule is implicated in a positive effect on proliferation, cytokine production and survival of T cells. Collectively these data demonstrate that absence of CD40L correlates with (i) reduced antimicrobial activity of natural effector cells; (ii) reduction of the magnitude of T cell response; and (iii) increase of fungal growth in the brain. These findings suggest that disruption of CD40/CD40L may be deleterious for development of an efficient immune response to C. neoformans and may identify potential molecular targets for novel immunotherapeutic approaches

The polysaccharide capsule of Cryptococcus neoformans interferes with human dendritic cell maturation and activation

The ability of encapsulated and acapsular strains of Cryptococcus neoformans to activate dendritic cells (DC) derived from monocytes stimulated with granulocyte macrophage-colony stimulating factor and interleukin-4 was evaluated. Profound differences in DC response to encapsulated and acapsular C. neoformans strains were observed. In particular, (i) the acapsular strain was easily phagocytosed by immature DC, and the process induced several molecular markers, such as major histocompatibility complex (MHC) class I and class II, CD40, and CD83, which are characteristic of mature DC; (ii) the encapsulated strain did not up-regulate MHC class I and class II and CD83 molecules; (iii) the soluble capsular polysaccharide glucuronoxylomannan (GXM) is unable to regulate MHC class I and class II molecules; (iv) the addition of monoclonal antibody to GXM (anti-GXM) to the encapsulated strain facilitated antigen-presenting cell maturation by promoting ingestion of C. neoformans via Fc receptor for immunoglobulin G (FcgammaR)II (CD32) and FcgammaRIII (CD16); (v) pertubation of FcRgammaII or FcgammaRIII was insufficient to promote DC maturation; and (vi) optimal DC maturation permitted efficient T cell activation and differentiation, as documented by the enhancement of lymphoproliferation and interferon-gamma production. These results indicate that the C. neoformans capsule interferes with DC activation and maturation, indicating a new pathway by which the fungus may avoid an efficient T cell response.

Phenotypic switching of Cryptococcus neoformans can influence the outcome of the human immune response

The human pathogenic fungus Cryptococcus neoformans exhibits the phenomenon of phenotypic switching, a process that generates variant colonies that can differ in morphology, virulence and other characteristics such as capsular glucuronoxylomannan (GXM) size and structure. A previous study established that mucoid colony (MC) variants of C. neoformans were more virulent and elicited a different inflammatory response than smooth colony (SM) variants. In this study, we investigated the interaction of cells from MC and SM variants and their respective GXMs with human T cells and monocytes. Specifically, we measured CD40, CD80 and CD86 expression, lymphoproliferation and interleukin (IL)-4, IL-10, interferon (IFN)-gamma and IL-12Rbeta2 expression in the presence and absence of variant cells and their GXMs. For some immune parameters, both MC and SM strains produced similar results, in particular no differences were observed in IL-4 induction. However, for other critical parameters, including CD86 expression, lymphoproliferation and IL-10 production, the MC variant had effects that can be expected to impair the immune response. Hence, a single C. neoformans strain can elicit several different immune responses depending on the colony type expressed, and this is unlikely to be accounted for by differences in phagocytosis only. The results provide a potential explanation for the higher virulence of the MC variant based on the concept that these cells inhibit the development of a vigorous immune response. Furthermore, the results suggest a mechanism by which phenotypic switching can generate variants able to evade the immune response.

Silica, hyaluronate, and alveolar macrophage functional differentiation

BACKGROUND

Silicosis is mediated by macrophages, their soluble mediators, and extracellular matrix molecules. In this study, we investigated the effects of silica and/or hyaluronate (HA) on several alveolar macrophage responses.

METHODS

We evaluated glycosaminoglycan (GAG) production by radiolabeled precursors, nitric oxide (NO) release by its oxidation product, phagocytic activity by Candida albicans internalization, and the secretion of two fibrogenic cytokines, tumor necrosis factor (TNF)-alpha and transforming growth factor (TGF)-beta, by specific assays.

RESULTS

Silica significantly reduced GAG secretion, particularly HA secretion. Alone, it decreased Candida uptake; associated with HA, it enhanced the reduction. Silica and Candida reduced NO release, which was not significantly affected when silica- or Candida-exposed cells were also treated with HA. TNF-alpha and TGF-beta activities were stimulated by silica but reduced by HA.

CONCLUSIONS

The results suggest that silica and HA modify alveolar macrophage functional differentiation. Silica- and HA-induced modifications of the microenvironment could determine whether the response proceeds toward healing and repair or toward lung chronic pathology.

Silica, Hyaluronate, and Alveolar Macrophage Functional Differentiation

Background

Silicosis is mediated by macrophages, their soluble mediators, and extracellular matrix molecules. In this study, we investigated the effects of silica and/or hyaluronate (HA) on several alveolar macrophage responses.

Methods

We evaluated glycosaminoglycan (GAG) production by radiolabeled precursors, nitric oxide (NO) release by its oxidation product, phagocytic activity by Candida albicans internalization, and the secretion of two fibrogenic cytokines, tumor necrosis factor (TNF)-α and transforming growth factor (TGF)-β, by specific assays.

Results

Silica significantly reduced GAG secretion, particularly HA secretion. Alone, it decreased Candida uptake; associated with HA, it enhanced the reduction. Silica and Candida reduced NO release, which was not significantly affected when silica- or Candida-exposed cells were also treated with HA. TNF-α and TGF-β activities were stimulated by silica but reduced by HA.

Conclusions

The results suggest that silica and HA modify alveolar macrophage functional differentiation. Silica- and HA-induced modifications of the microenvironment could determine whether the response proceeds toward healing and repair or toward lung chronic pathology.

Mannoprotein from Cryptococcus neoformans promotes T-helper type 1 anticandidal responses in mice

We previously demonstrated that mannoprotein (MP) from Cryptococcus neoformans (CnMP) stimulates interleukin-12 production by human monocytes, thus fostering a T-helper type 1 (Th1) protective anticryptococcal response. In this paper we show that CnMP was also able to induce a Candida albicans-directed protective Th1 response. This was demonstrated for mice immunized with CnMP by induction of a delayed-type hypersensitivity (DTH) reaction to C. albicans MP (CaMP) as well as induction of gamma interferon production by CD4(+) and CD8(+) splenic T cells stimulated in vitro with CaMP. CnMP-immunized mice were also partially protected from lethal systemic challenge with C. albicans, as shown by prolonged median survival times and decreased fungal burden in the kidney. Much evidence supports the validity of these cross-reactive and functional Th1 responses: (i) a non-cross-reactive C. albicans antigen, such as enolase, did not produce a DTH response to CaMP; (ii) passive adoptive transfer of T cells primed with CnMP induced a DTH reaction; (iii) C. neoformans extract elicited a DTH response to CaMP; and (iv) a monoclonal antibody (7H6) directed against a major and immunodominant T-cell-stimulatory 65-kDa MP (MP65) of C. albicans also recognized discrete 100-kDa constituents of C. neoformans extracts, as well as secretory constituents of the fungus. These results suggest the presence of common Th1 antigenic determinants in the mannoproteic material of C. neoformans and C. albicans epitopes, which should be considered in devising common strategies for immunoprophylactic or immunotherapeutic control of the fungi.

Anti-Candida albicans properties of novel benzoxazine analogues

We previously reported that azole 1,4-benzothiazine derivatives have appreciable anti-Candida activity. In this study, we synthesized 1,4-benzoxazine analogues and examined their possible antifungal activity to further analyze the structure-activity relationships. Results of in vitro and in vivo experiments showed that 1,4-benzoxazine analogues show appreciable antifungal activity. In particular, they have significant capability to cure mice systemically infected with a lethal challenge of Candida albicans, as indicated by increased survival time paralleling reduction of colony forming units. Moreover, 1,4-benzoxazine derivatives also showed immunomodulating activity, as indicated by a significant increase of interleukin-12 and interferon-gamma production by splenocytes and reinforcement of a T helper type 1 protective immune response to C. albicans. In conclusion, the results demonstrate that replacement of sulfur by oxygen may improve immune response against C. albicans infection.

Antibody to Cryptococcus neoformans capsular glucuronoxylomannan promotes expression of interleukin-12Rbeta2 subunit on human T cells in vitro through effects mediated by antigen-presenting cells

The results reported herein show that T cells responding to encapsulated Cryptococcus neoformans cells had reduced expression of interleukin-12 receptor beta2 (IL-12Rbeta2) in comparison to those responding to non-encapsulated cells. This suggested that encapsulation with glucuronoxylomannan (GXM), the principal constituent of the C. neoformans polysaccharide antiphagocytic capsule, inhibited expression of the IL-12Rbeta2 subunit on T cells responding to cryptococcal antigens. Addition of GXM-binding monoclonal antibody (mAb) overcame this effect by promoting IL-12Rbeta2 expression and by decreasing IL-1R expression on T cells. This effect may be a consequence of mAb-induced changes on antigen-presenting cells (APC) that are closely related to increased phagocytosis. Blocking of phagocytosis with monoiodacetic acid (MIA) precluded up-regulation of B7 expression on APC and was associated with diminished IL-12Rbeta2 expression on T cells. The observed effects on T cells were interpreted as a consequence of increased APC function due to enhanced phagocytosis. These findings suggest a mechanism by which specific antibody can promote the polarization of the cellular immune response towards a Th1-like response and thus contribute to an enhanced cellular immune response against C. neoformans.