Nanoparticle­based antiviral strategies to combat the influenza virus (Review).

The rapid availability of effective antiviral treatments would be beneficial during the early phases of a pandemic, as they could reduce viral loads and control serious infections until antigenic vaccines become widely available. One promising alternative therapy to combat pandemics is nanotechnology, which has the potential to inhibit a wide variety of viruses, including the influenza virus. This review summarizes the recent progress using gold, copper, silver, silicone, zinc and selenium nanoparticles, since these materials have shown remarkable antiviral capacity against influenza A virus.

Radical Scavenging, Hemocompatibility, and Antibacterial Activity against MDR Acinetobacter baumannii in Alginate-Based Aerogels Containing Lipoic Acid-Capped Silver Nanoparticles.

Retaining the hemocompatibility, supporting cell growth, and exhibiting anti-inflammatory and antioxidant properties, while having antimicrobial activity, particularly against multidrug-resistant bacteria (MDR), remain a challenge when designing aerogels for biomedical applications. Here, we report that our synthesized alginate-based aerogels containing either 7.5 or 11.25 µg of lipoic acid-capped silver nanoparticles (AgNPs) showed improved hemocompatibility properties while retaining their antimicrobial effect against MDR Acinetobacter baumannii and the reference strain Escherichia coli, relative to a commercial dressing and polymyxin B, used as a reference. The differences in terms of the microstructure and nature of the silver, used as the bioactive agent, between our synthesized aerogels and the commercial dressing used as a reference allowed us to improve several biological properties in our aerogels with respect to the reference commercial material. Our aerogels showed significantly higher antioxidant capacity, in terms of nmol of Trolox equivalent antioxidant capacity per mg of aerogel, than the commercial dressing. All our synthesized aerogels showed anti-inflammatory activity, expressed as nmol of indomethacin equivalent anti-inflammatory activity per mg of aerogel, while this property was not found in the commercial dressing material. Finally, our aerogels were highly hemocompatible (less than 1% hemolysis ratio); however, the commercial material showed a 20% hemolysis rate. Therefore, our alginate-based aerogels with lipoic acid-capped AgNPs hold promise for biomedical applications.

Antimicrobial and Antibiofilm Effect of Inulin-Type Fructans, Used in Synbiotic Combination with Lactobacillus spp. Against Candida albicans.

There is great interest in the search for new alternatives to antimicrobial drugs, and the use of prebiotics and probiotics is a promising approach to this problem. This study aimed to assess the effect of inulin-type fructans, used in synbiotic combinations with Lactobacillus paracasei or Lactobacillus plantarum, on the production of short-chain fatty acids and antimicrobial activity against Candida albicans. The inhibition assay using the L. paracasei and L. plantarum supernatants resulting from the metabolization of inulin-type fructans displayed growth inhibition and antibiofilm formation against C. albicans. Inhibition occurred at concentrations of 12.5, 25, and 50% of the L. paracasei supernatant and at a concentration of 50% of the L. plantarum supernatant. The analysis of short-chain fatty acids by gas chromatography showed that lactic acid was the dominating produced metabolite. However, acetic, propionic, and butyric acids were also detected in supernatants from both probiotics. Therefore, the synbiotic formulation of L. paracasei or L. plantarum in the presence of inulin-type fructans constitutes with anticandidal effect is a possible option to produce antifungal drugs or antimicrobial compounds.

Green Metallic Nanoparticles for Cancer Therapy: Evaluation Models and Cancer Applications.

Metal-based nanoparticles are widely used to deliver bioactive molecules and drugs to improve cancer therapy. Several research works have highlighted the synthesis of gold and silver nanoparticles by green chemistry, using biological entities to minimize the use of solvents and control their physicochemical and biological properties. Recent advances in evaluating the anticancer effect of green biogenic Au and Ag nanoparticles are mainly focused on the use of conventional 2D cell culture and in vivo murine models that allow determination of the half-maximal inhibitory concentration, a critical parameter to move forward clinical trials. However, the interaction between nanoparticles and the tumor microenvironment is not yet fully understood. Therefore, it is necessary to develop more human-like evaluation models or to improve the existing ones for a better understanding of the molecular bases of cancer. This review provides recent advances in biosynthesized Au and Ag nanoparticles for seven of the most common and relevant cancers and their biological assessment. In addition, it provides a general idea of the in silico, in vitro, ex vivo, and in vivo models used for the anticancer evaluation of green biogenic metal-based nanoparticles.

Vaccination with BCGΔBCG1419c protects against pulmonary and extrapulmonary TB and is safer than BCG.

A single intradermal vaccination with an antibiotic-less version of BCGΔBCG1419c given to guinea pigs conferred a significant improvement in outcome following a low dose aerosol exposure to M. tuberculosis compared to that provided by a single dose of BCG Pasteur. BCGΔBCG1419c was more attenuated than BCG in murine macrophages, athymic, BALB/c, and C57BL/6 mice. In guinea pigs, BCGΔBCG1419c was at least as attenuated as BCG and induced similar dermal reactivity to that of BCG. Vaccination of guinea pigs with BCGΔBCG1419c resulted in increased anti-PPD IgG compared with those receiving BCG. Guinea pigs vaccinated with BCGΔBCG1419c showed a significant reduction of M. tuberculosis replication in lungs and spleens compared with BCG, as well as a significant reduction of pulmonary and extrapulmonary tuberculosis (TB) pathology measured using pathology scores recorded at necropsy. Evaluation of cytokines produced in lungs of infected guinea pigs showed that BCGΔBCG1419c significantly reduced TNF-α and IL-17 compared with BCG-vaccinated animals, with no changes in IL-10. This work demonstrates a significantly improved protection against pulmonary and extrapulmonary TB provided by BCGΔBCG1419c in susceptible guinea pigs together with an increased safety compared with BCG in several models. These results support the continued development of BCGΔBCG1419c as an effective vaccine for TB.

Proteomic characterization of a second-generation version of the BCGΔBCG1419c vaccine candidate by means of electrospray-ionization quadrupole time-of-flight mass spectrometry.

Tuberculosis (TB) is the most important infectious disease worldwide, based on the number of new cases and deaths reported by the World Health Organization. Several vaccine candidates against TB have been characterized at preclinical and clinical levels. The BCGΔBCG1419c vaccine candidate, which lacks the BCG1419c gene that encodes for a c-di-GMP phosphodiesterase, provides improved efficacy against chronic TB, reactivation from latent-like infection and against chronic TB in the presence of type 2 diabetes in murine models. We previously reported that compared with wild type BCG, BCGΔBCG1419c changed levels of several proteins. Here, using a label-free proteomic approach, we confirmed that a novel, second-generation version of BCGΔBCG1419c maintains changes in antigenic proteins already reported, and here we further found differences in secreted proteins, as well as that this new BCGΔBCG1419c version modifies its production of proteins involved in redox and nitrogen/protein metabolism compared with wild type BCG. This work contributes to the proteomic characterization of a novel vaccine candidate that is more effective against TB than parental BCG in diverse murine models.

Overexpression of the celA1 gene in BCG modifies surface pellicle, glucosamine content in biofilms, and affects in vivo replication.

Biofilm formed in vitro by mycobacteria has been associated with increased antibiotic tolerance as compared with planktonic cells. Cellulose has been identified as a component of DTT-exposed biofilms formed by M. tuberculosis. The celA1 gene of M. tuberculosis encodes a cellulase, which could affect the formation of biofilm by slow-growing mycobacteria. In this work, the celA1 gene of M. tuberculosis was cloned into the integrative pMV361 plasmid and then transformed into M. bovis BCG Pasteur to produce BCG:celA1, to have celA1 expressed from the strong promoter hsp60. We compared planktonic and biofilm growth, possible presence of CelA1 in whole protein extracts, quantitated biofilm, presence of monosaccharides, and bacillary burden in lungs after aerosol infection in BALB/c mice. Differences in the appearance of the surface pellicle and of the biofilm attached to the substrate were observed. In biofilms, we observed a significant decrease of glucosamine in BCG:celA1 compared with BCG:pMV361. Finally, BCG:celA1 had lower viable bacteria than the BCG:pMV361 strain after 24 h and 3 weeks post-infection, but no difference was found at 9 weeks post-infection.

Transcriptional portrait of M. bovis BCG during biofilm production shows genes differentially expressed during intercellular aggregation and substrate attachment.

Mycobacterium tuberculosis and M. smegmatis form drug-tolerant biofilms through dedicated genetic programs. In support of a stepwise process regulating biofilm production in mycobacteria, it was shown elsewhere that lsr2 participates in intercellular aggregation, while groEL1 was required for biofilm maturation in M. smegmatis. Here, by means of RNA-Seq, we monitored the early steps of biofilm production in M. bovis BCG, to distinguish intercellular aggregation from attachment to a surface. Genes encoding for the transcriptional regulators dosR and BCG0114 (Rv0081) were significantly regulated and responded differently to intercellular aggregation and surface attachment. Moreover, a M. tuberculosis H37Rv deletion mutant in the Rv3134c-dosS-dosR regulon, formed less biofilm than wild type M. tuberculosis, a phenotype reverted upon reintroduction of this operon into the mutant. Combining RT-qPCR with microbiological assays (colony and surface pellicle morphologies, biofilm quantification, Ziehl-Neelsen staining, growth curve and replication of planktonic cells), we found that BCG0642c affected biofilm production and replication of planktonic BCG, whereas ethR affected only phenotypes linked to planktonic cells despite its downregulation at the intercellular aggregation step. Our results provide evidence for a stage-dependent expression of genes that contribute to biofilm production in slow-growing mycobacteria.

Transcriptional and Mycolic Acid Profiling in Mycobacterium bovis BCG In Vitro Show an Effect for c-di-GMP and Overlap between Dormancy and Biofilms.

Mycobacterium tuberculosis produces mycolic acids which are relevant for persistence, recalcitrance to antibiotics and defiance to host immunity. c-di-GMP is a second messenger involved in transition from planktonic cells to biofilms, whose levels are controlled by diguanylate cyclases (DGC) and phosphodiesterases (PDE). The transcriptional regulator dosR, is involved in response to low oxygen, a condition likely happening to a subset of cells within biofilms. Here, we found that in M. bovis BCG, expression of both BCG1416c and BCG1419c genes, which code for a DGC and a PDE, respectively, decreased in both stationary phase and during biofilm production. The kasA, kasB, and fas genes, which are involved in mycolic acid biosynthesis, were induced in biofilm cultures, as was dosR, therefore suggesting an inverse correlation in their expression compared with that of genes involved in c-di-GMP metabolism. The relative abundance within trehalose dimycolate (TDM) of α-mycolates decreased during biofilm maturation, with methoxy mycolates increasing over time, and keto species remaining practically stable. Moreover, addition of synthetic c-di-GMP to mid-log phase BCG cultures reduced methoxy mycolates, increased keto species and practically did not affect α-mycolates, showing a differential effect of c-di-GMP on keto- and methoxy-mycolic acid metabolism.

Sterilized chitosan-based composite hydrogels: Physicochemical characterization and in vitro cytotoxicity.

Gelatin/chitosan/polyvinyl alcohol hydrogels were fabricated at different polymer ratios using the freeze-drying and sterilized by steam sterilization. The thermal stability, chemical structure, morphology, surface area, mechanical properties, and biocompatibility of hydrogels were evaluated by simultaneous thermal analysis, Fourier transform infrared spectroscopy, X-ray diffraction, confocal microscopy, adsorption/desorption of nitrogen, rheometry, and 3-4,[5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide cell viability assay (MTT assay), respectively. The samples showed a decomposition onset temperature below 253.3 ± 4.8°C, a semicrystalline nature, and a highly porous structure. Hydrogels reached the maximum water uptake in phosphate-buffered saline after 80 min, showing values from nine to twelve times their dry mass. Also, hydrogels exhibiting a solid-like behavior ranging from 2,567 ± 467 to 48,705 ± 2,453 Pa at 0.1 rad/s (low frequency). The sterilized hydrogels showed low cytotoxicity (cell viability > 70%) to the HT29-MTX-E12 cell line. Sterilized hydrogels by steam sterilization can be good candidates as scaffolds for tissue engineering applications.

Immune response elicited by two rBCG strains devoid of genes involved in c-di-GMP metabolism affect protection versus challenge with M. tuberculosis strains of different virulence.

Pellicles, a type of biofilm, have gathered a renewed interest in the field of tuberculosis as a structure that mimics some characteristics occurring during M. tuberculosis infection, such as antibiotic recalcitrance and chronicity of infection, and as a source of antigens for humoral response in infected guinea pigs. In other bacteria, it has been well documented that the second messenger c-di-GMP modulates the transition from planktonic cells to biofilm formation. In this work, we used the live vaccine Mycobacterium bovis BCG to determine whether deletion of genes involved in c-di-GMP metabolism would affect interaction with macrophages, capacity to induce immune response in a murine cell line and mice, and how the protein profile was modified when grown as surface pellicles. We found that deletion of the BCG1419c (Delta c-di-GMP phosphodiesterase, ΔPDE) gene, or deletion of the BCG1416c (Delta c-di-GMP diguanylate cyclase, ΔDGC) gene, altered production of TNF-α, IL-6, and IL-1ß, in murine macrophages, and resulted in attenuation in intra-macrophage replication. Moreover, in addition to the improved immunogenicity of the BCGΔBCG1419c mutant already reported, deletion of the BCG1416c gene leads to increased T CD4+ and T CD8+ activation. This correlated with protection versus lethality in mice infected with the highly virulent M. tuberculosis 5186 afforded by vaccination with all the tested BCG strains, and controlled the growth of the mildly virulent M. tuberculosis H37Rv in lungs by vaccination with BCGΔBCG1419c during chronic late infection from 4 to 6 months after challenge. Furthermore, when grown as surface pellicles, a condition used to manufacture BCG vaccine, in comparison to BCG wild type, both rBCGs changed expression of antigenic proteins such as DnaK, HbhA, PstS2, 35KDa antigen, GroEL2, as well as AcpM, a protein involved in synthesis of mycolic acids, molecules relevant to modulate inflammatory responses.

A quantitative model for dermal infection and oedema in BALB/c mice pinna.

BACKGROUND: Pharmaceutical industry demands innovation for developing new molecules to improve effectiveness and safety of therapeutic medicines. Preclinical assays are the first tests performed to evaluate new therapeutic molecules using animal models. Currently, there are several models for evaluation of treatments, for dermal oedema or infection. However, the most common or usual way is to induce the inflammation with chemical substances instead of infectious agents. On the other hand, this kind of models require the implementation of histological techniques and the interpretation of pathologies to verify the effectiveness of the therapy under assessment. This work was focused on developing a quantitative model of infection and oedema in mouse pinna. The infection was achieved with a strain of Streptococcus pyogenes that was inoculated in an injury induced at the auricle of BALB/c mice, the induced oedema was recorded by measuring the ear thickness with a digital micrometer and histopathological analysis was performed to verify the damage. The presence of S. pyogenes at the infection site was determined every day by culture. RESULTS: Our results showed that S. pyogenes can infect the mouse pinna and that it can be recovered at least for up to 4 days from the infected site; we also found that S. pyogenes can induce a bigger oedema than the PBS-treated control for at least 7 days; our results were validated with an antibacterial and anti-inflammatory formulation made with ciprofloxacin and hydrocortisone. CONCLUSIONS: The model we developed led us to emulate a dermal infection and allowed us to objectively evaluate the increase or decrease of the oedema by measuring the thickness of the ear pinna, and to determine the presence of the pathogen in the infection site. We consider that the model could be useful for assessment of new anti-inflammatory or antibacterial therapies for dermal infections.

The Cyclic Di-GMP Phosphodiesterase Gene Rv1357c/BCG1419c Affects BCG Pellicle Production and In Vivo Maintenance.

Bacteria living in a surface-attached community that contains a heterogeneous population, coated with an extracellular matrix, and showing drug tolerance (biofilms) are often linked to chronic infections. In mycobacteria, the pellicle mode of growth has been equated to an in vitro biofilm and meets several of the criteria mentioned above, while tuberculosis infection presents a chronic (latent) phase of infection. As mycobacteria lack most genes required to control biofilm production by other microorganisms, we deleted or expressed from the hsp60 strong promoter the only known c-di-GMP phosphodiesterase (PDE) gene in Mycobacterium bovis BCG. We found changes in pellicle production, cellular protein profiles, lipid production, resistance to nitrosative stress and maintenance in lungs and spleens of immunocompetent BALB/mice. Our results show that pellicle production and capacity to remain within the host are linked in BCG.