Evaluation and validation of reference genes for RT-qPCR gene expression in Naegleria gruberi

Naegleria gruberi is a free-living amoeboflagellate commonly found in freshwater and in soils around the world. It is a non-pathogenic relative of Naegleria fowleri, which is the etiologic agent of Primary Amoebic Meningoencephalitis (PAM). PAM occurs world-wide and it is considered a rare disease, but its fatality rate is high (96%) mainly because of delay in initiation of treatment due to misdiagnosis and lack of a specific treatment. The analysis of gene expression by quantitative real-time PCR in N. gruberi could be a highly efficient means to understand the pathogenicity of N. fowleri and also to find drug targets. Accurate RT-qPCR analysis requires correct normalization of gene expression data using reference genes (RG), whose expression should be constant under different experimental conditions. In this study, six genes, representing the most frequently used housekeeping genes, were selected for evaluation as reference genes in N. gruberi. The expression and stability of these genes was evaluated employing four algorithms (geNorm, NormFinder, BestKeeper and RefFinder). This work shows significant variations of the stability of RGs depending on the algorithms employed and on the experimental conditions (i.e. logarithmic, stationary, heat-shock and oxidative stress). The geNorm, NormFinder and RefFinder analysis of all the experimental conditions in combination revealed that ACT and G6PD were the most stable RGs. While BestKeeper analysis showed that 18S and TBP were the most stable RGs. Moreover, normalization of HSP90 gene expression with the most stable RGs resulted in an upregulation whereas when the normalization was done with the unstable RGs, the gene expression was not reliable. Hence, the implications of this study are relevant to gene expression studies in N. gruberi.

Assessing Acanthamoeba cytotoxicity: comparison of common cell viability assays

Background

In vitro models for studying interactions between Acanthamoeba and host cells are crucial for understanding the pathomechanism of Acanthamoeba and assessing differences between strains and cell types. The virulence of Acanthamoeba strains is usually assessed and monitored by using cell cytotoxicity assays. The aim of the present study was to evaluate and compare the most widely used cytotoxicity assays for their suitability to assess Acanthamoeba cytopathogenicity.

Methods

The viability of human corneal epithelial cells (HCECs) after co-culture with Acanthamoeba was evaluated in phase contrast microscopy.

Results

It was shown that Acanthamoeba is unable to considerably reduce the tetrazolium salt and the NanoLuc® Luciferase prosubstrate to formazan and the luciferase substrate, respectively. This incapacity helped to generate a cell density-dependent signal allowing to accurately quantify Acanthamoeba cytotoxicity. The lactate dehydrogenase (LDH) assay led to an underestimation of the cytotoxic effect of Acanthamoeba on HCECs since their co-incubation negatively affected the lactate dehydrogenase activity.

Discussion

Our findings demonstrate that cell-based assays using the aqueous soluble tetrazolium-formazan, and the NanoLuc® Luciferase prosubstrate products, in contrast to LDH, are excellent markers to monitor the interaction of Acanthamoeba with human cell lines and to determine and quantify effectively the cytotoxic effect induced by the amoebae. Furthermore, our data indicate that protease activity may have an impact on the outcome and thus the reliability of these tests.

Optimal Fast Integral Decontamination of Bacillus thuringiensis Aerosols and Fast Disinfection of Contaminated Surfaces

Aerosolized anthrax (Bacillus anthracis) spores are of extreme health concern and can remain airborne for hours and contaminate all kinds of surfaces, constituting reservoirs from which resuspension is easily produced. The assessment of decontamination techniques must therefore consider both air and surfaces. In the present study, several kinds of disinfecting fogs were experimentally tested against Bacillus thuringiensis spores, which served as a surrogate for Bacillus anthracis, both as aerosols released into the air and spread on porous and non-porous surfaces with different positions and orientations. This technology removed Bacillus thuringiensis spores from the air in 20 min with just a 1 min application of fog. The dynamics and characteristics of the fog, related to aerosol and surface interactions, proved to be critical for optimal performance and decontamination. An optimal configuration could provide effective disinfection even on indirectly reached surfaces. In all cases, 8% hydrogen peroxide (H₂O₂) provided a higher disinfection rate than 2% glutaraldehyde.

Amoebicidal activity of cationic carbosilane dendrons derived with 4-phenylbutyric acid against Acanthamoeba griffini and Acanthamoeba polyphaga trophozoites and cysts

Amoebae from the genus Acanthamoeba are important pathogens responsible for severe illnesses in humans such as Acanthamoeba keratitis and granulomatous amoebic encephalitis. In the last few decades, AK diagnoses have steadily increased. Most patients suffering from AK were contact lens users and the infection was related to poor hygiene. However, therapy is not yet well established, and treatments may last for several months due to resistance. Moreover, these treatments have been described to generate cytotoxicity. Therefore, there is an urgent need to develop new therapeutic strategies against AK. In this study, the amoebicidal activity of different generation cationic carbosilane dendrons derived with 4-phenylbutyric acid was demonstrated against Acanthamoeba polyphaga and Acanthamoeba griffini trophozoites and cysts. In addition, the combination of chlorhexidine digluconate and the most effective dendron (ArCO2G2(SNMe3I)4) showed an in vitro effect against Acanthamoeba trophozoites and cysts, reducing the minimal trophozoite amoebicidal concentration as well as concentrations with cysticidal activity.

Thio- and selenosemicarbazones as antiprotozoal agents against Trypanosoma cruzi and Trichomonas vaginalis

Herein, we report the preparation of a panel of Schiff bases analogues as antiprotozoal agents by modification of the stereoelectronic effects of the substituents on N-1 and N-4 and the nature of the chalcogen atom (S, Se). These compounds were evaluated towards Trypanosoma cruzi and Trichomonas vaginalis. Thiosemicarbazide 31 showed the best trypanocidal profile (epimastigotes), similar to benznidazole (BZ): IC₅₀ (31)=28.72 μM (CL-B5 strain) and 33.65 μM (Y strain), IC₅₀ (BZ)=25.31 μM (CL-B5) and 22.73 μM (Y); it lacked toxicity over mammalian cells (CC₅₀ > 256 µM). Thiosemicarbazones 49, 51 and 63 showed remarkable trichomonacidal effects (IC₅₀ =16.39, 14.84 and 14.89 µM) and no unspecific cytotoxicity towards Vero cells (CC₅₀ ≥ 275 µM). Selenoisosters 74 and 75 presented a slightly enhanced activity (IC₅₀=11.10 and 11.02 µM, respectively). Hydrogenosome membrane potential and structural changes were analysed to get more insight into the trichomonacidal mechanism.

In Vitro Evaluation of the Combination of Melaleuca alternifolia (Tea Tree) Oil and Dimethyl Sulfoxide (DMSO) against Trophozoites and Cysts of Acanthamoeba Strains. Oxygen Consumption Rate (OCR) Assay as a Method for Drug Screening

Ameobae belonging to the genus Acanthamoeba are responsible for the human diseases Acanthamoeba keratitis (AK) and granulomatous amoebic encephalitis (GAE). The treatment of these illnesses is hampered by the existence of a resistance stage (cysts). In an attempt to add new agents that are effective against trophozoites and cysts, tea tree oil (TTO) and dimethyl sulfoxide (DMSO), separately and in combination, were tested In Vitro against two Acanthamoeba isolates, T3 and T4 genotypes. The oxygen consumption rate (OCR) assay was used as a drug screening method, which is to some extent useful in amoebicide drug screening; however, evaluation of lethal effects may be misleading when testing products that promote encystment. Trophozoite viability analysis showed that the effectiveness of the combination of both compounds is higher than when either compound is used alone. Therefore, the TTO alone or TTO + DMSO in combination were an amoebicide, but most of the amoebicidal activity in the combination’s treatments seemed to be caused mainly by the TTO effect. In fact, DMSO alone seems to be a non-amoebicide, triggering encystment. Regarding cytotoxicity, these compounds showed toxicity in human corneal epithelial cells (HCEpiC), even at low concentrations when tested in combination. In conclusion, the use of TTO and DMSO, in combination or alone, cannot be recommended as an alternative for AK treatment until more cytotoxicity and cyst adhesion tests are performed.

Ultrastructural Study of Acanthamoeba polyphaga Trophozoites and Cysts Treated In Vitro with Cationic Carbosilane Dendrimers

Cationic carbosilane dendrimers are branched molecules with antimicrobial properties. Their activity has been tested against Acanthamoeba polyphaga, a causative agent of Acanthamoeba keratitis, a severe ocular disease in humans. A. polyphaga trophozoites and cysts were exposed to different noncytotoxic cationic carbosilane dendrimers with proven antiamoebic activity. The effects of treatment on cell surface and cell ultrastructure were examined by scanning and transmission electron microscopy, respectively. Two of the dendrimers tested induced dramatic alterations of cellular ultrastructure in both trophozoites and cysts, including vacuolization, depletion of cytoplasmic contents, and reduced cell size. Additionally, we observed severe alterations of the plasma membrane with membrane blebbing in trophozoites and disruption in cysts. These alterations were also observed with chlorhexidine, a drug used for treatment of Acanthamoeba keratitis. Our results support that these compounds may target membranes, and their action is critical for parasite integrity.

Experimental keratitis in rats caused by Acanthamoeba griffini: A kinetic histopathological study

The aim of this study was to evaluate the inflammation process that resulted from the inoculation of Wistar Rats with Acanthamoeba griffini, a virulent T3 Acanthamoeba genotype that produces keratitis. Haematoxylin and eosin, periodic acid stain, immunohistochemistry and morphometry were used to analyse tissues from rats of an Acanthamoeba keratitis (AK) model. Two weeks after inoculating the rats with A griffini trophozoites, the thickness of the stroma had diminished, followed by an increase in thickness at 4 weeks. At the latter time, an abundance of inflammatory infiltrate cells was observed, some found to express IL-1β, IL-10 and/or caspase 3. Intercellular adhesion molecule-1 was expressed in corneal blood vessels amid the abundant vascularization characteristic of the development of AK. Through an immunohistochemical technique, trophozoites were detected at 2 and 4 weeks post-inoculation. By 8 weeks, there were a low number of trophozoites and cysts and the corneas of infected rats were similar in thickness to those of the controls. Thus, the rats were capable of healing experimental AK in the present rat model. Diverse immunological mechanisms regulated the inflammatory process in acute AK induced by A griffini in a murine model.

Synthesis and in vitro activity of new biguanide-containing dendrimers on pathogenic isolates of Acanthamoeba polyphaga and Acanthamoeba griffini

The genus Acanthamoeba can cause Acanthamoeba keratitis (AK) and granulomatous amoebic encephalitis (GAE). The treatment of these illnesses is hampered by the existence of a resistance stage that many times causes infection relapses. In an attempt to add new agents to our chemotherapeutic arsenal against acanthamebiasis, two Acanthamoeba isolates were treated in vitro with newly synthesized biguanide dendrimers. Trophozoite viability analysis and ultrastructural studies showed that dendrimers prevent encystment by lysing the cellular membrane of the amoeba. Moreover, one of the dendrimers showed low toxicity when tested on mammalian cell cultures, which suggest that it might be eventually used as an amoebicidal drug or as a disinfection compound in contact lens solutions.

Development and optimization of new culture media for Acanthamoeba spp. (Protozoa: Amoebozoa)

The isolation and growth in axenic liquid media of Acanthamoeba strains is necessary in order to carry out primary in vitro drug screening. Amoebic isolates which are hard to grow in the current liquid media have been reported. Such circumstances hampers the ability of conducting drug sensitivity tests. Therefore, finding suitable universal growth media for Acanthamoeba species is required. The present study was aimed at the development of liquid medium suitable for growing a fastidious (F) genotype T3 Acanthamoeba isolate, and eventually for other genotypes of this genus as well. Trophozoite growth was indirectly monitored by respiration analysis with oxygen-sensitive microplates (OSM) and further confirmed by manual counting. Media were empirically designed and tested first in a non-fastidious (NF) T3 isolate and then tested with 14 different strains, including the fastidious one. Combinations of nutritive components such as meat/vegetable broth, LB medium, malt and skimmed milk led to the design of new media suitable for culturing all the isolates tested, in conditions similar to those obtained in standard culture media such as PYG or CERVA.

Antibacterial and antifungal properties of dendronized silver and gold nanoparticles with cationic carbosilane dendrons

Water soluble silver nanoparticles (AgNPs) capped with cationic carbosilane dendrons have been synthesized by direct reaction in water of dendrons, silver precursor and a reducing agent. These nanoparticles have been characterized by nuclear magnetic resonance (NMR), transmission electron microscopy (TEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), ultraviolet spectroscopy (UV), elemental analysis, and zeta potential (ZP). The antibacterial and antifungal properties of the cationic dendrons and dendronized AgNPs and AuNPs with these dendrons have been evaluated against Gram-negative and Gram-positive bacterial -including resistant strains- and yeast strains, respectively. The results stand out for the activity of AgNPs covered with first generation dendron compared with this free dendron and corresponding dendronized AuNPs.