Novel Antimicrobial Peptides Formulated in Chitosan Matrices are Effective Against Biofilms of Multidrug-Resistant Wound Pathogens.

INTRODUCTION: Infection frequently complicates the treatment of combat-related wounds, impairs healing, and leads to worse outcomes. To better manage wound infections, antimicrobial therapies that are effective against biofilm and designed for direct wound application are needed. The primary objective of this work was to evaluate a chitosan matrix for delivery of two engineered antimicrobial peptides, (ASP)-1 and ASP-2, to treat biofilm-associated bacteria. A secondary objective was to determine whether replacing the levorotatory (L) form amino acids in ASP-2 with dextrorotatory (D) form amino acids would impact peptide activity. MATERIALS AND METHODS: Chitosan gels loaded with antimicrobial peptides were evaluated for peptide release over 7 days and tested for efficacy against biofilms grown both in vitro on polymer mesh and ex vivo on porcine skin. RESULTS: When delivered via chitosan, 70% to 80% of peptides were released over 7 days. Gels eradicated biofilms of gram-positive and gram-negative, drug-resistant bacteria in vitro and ex vivo. Under the conditions tested, no meaningful differences in peptide activity between the L and D forms of ASP-2 were detected. CONCLUSIONS: Chitosan serves as an effective delivery platform for ASP-1 and ASP-2 to treat biofilm-embedded bacteria and warrants further development as a topical treatment.

Adapting Digital Social Prescribing for Suicide Bereavement Support: The Findings of a Consultation Exercise to Explore the Acceptability of Implementing Digital Social Prescribing within an Existing Postvention Service.

This paper describes a consultation exercise to explore the acceptability of adapting digital social prescribing (DSP) for suicide bereavement support. Bereavement by suicide increases the risk of suicide and mental health issues. Social prescribing improves connectedness and empowerment and can provide digital outcomes-based reporting to improve the capacity for measuring the effectiveness of interventions. Our aim was to consult on the acceptability and potential value of DSP for addressing the complexities of suicide bereavement support. Our approach was underpinned by implementation science and a co-design ethos. We reviewed the literature and delivered DSP demonstrations as part of our engagement process with commissioners and service providers (marrying evidence and context) and identified key roles for stakeholders (facilitation). Stakeholders contributed to a co-designed workshop to establish consensus on the challenges of providing postvention support. We present findings on eight priority challenges, as well as roles and outcomes for testing the feasibility of DSP for support after suicide. There was a consensus that DSP could potentially improve access, reach, and monitoring of care and support. Stakeholders also recognised the potential for DSP to contribute substantially to the evidence base for postvention support. In conclusion, the consultation exercise identified challenges to facilitating DSP for support after suicide and parameters for feasibility testing to progress to the evaluation of this innovative approach to postvention.

A Novel Peptide-Based Antimicrobial Wound Treatment is Effective Against Biofilms of Multi-Drug Resistant Wound Pathogens.

Wound infections are a common complication of combat-related injuries that significantly increase morbidity and mortality. Multi-drug resistant (MDR) organisms and their associated biofilms play a significant role in the pathogenicity and chronicity of wound infections. A critical barrier to progress in the treatment of traumatic wounds is the need for broad spectrum antimicrobials that are effective against biofilms and compatible with topical delivery. In this study, we present the in vitro efficacy of two de novo designed cationic, antimicrobial peptides and related topical formulations against single species and polymicrobial biofilms of MDR bacteria. Minimum biofilm eradication concentrations for peptides ranged from 0.7 µM for Staphylococcus aureus to 13.2 µM for Pseudomonas aeruginosa. Varying pH did not adversely impact peptide activity, however, in the presence of albumin, minimum biofilm eradication concentrations generally increased. When formulated into gels or dressings, both peptides eradicated mono- and polymicrobial biofilms of MDR pathogens. The biocompatibility index (BI) was found to be greater than one for both ASP-1 and ASP-2, with a slightly greater (more favorable) BI for ASP-2. The BIs for both peptides were greater than BIs previously reported for commonly used topical antimicrobial agents. The antimicrobial peptides and related formulations presented provide a promising platform for treatment of wound biofilms to improve outcomes for those injured in combat.

Beyond conventional antibiotics - New directions for combination products to combat biofilm.

Medical device related infections are a significant and growing source of morbidity and mortality. Biofilm formation is a common feature of medical device infections that is not effectively prevented or treated by systemic antibiotics. Antimicrobial medical device combination products provide a pathway for local delivery of antimicrobial therapeutics with the ability to achieve high local concentrations while minimizing systemic side effects. In this review, we present considerations for the design of local antimicrobial delivery systems, which can be facilitated by modeling local pharmacokinetics in the context of the target device application. In addition to the need for local delivery, a critical barrier to progress in the field is the need to incorporate agents effective against biofilm. This article aims to review key properties of antimicrobial peptides that make them well suited to meet the demands of the next generation of antimicrobial medical devices, including broad spectrum activity, rapid and biocidal mechanisms of action, and efficacy against biofilm.

Nisin adsorption to polyethylene oxide layers and its resistance to elution in the presence of fibrinogen.

The adsorption and elution of the antimicrobial peptide nisin at silanized silica surfaces coated to present pendant polyethylene oxide chains was detected in situ by zeta potential measurements. Silica microspheres were treated with trichlorovinylsilane to introduce hydrophobic vinyl groups, followed by self assembly of the polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock surfactant Pluronic F108, or an F108 derivative with nitrilotriacetic acid end groups. Triblock-coated microspheres were gamma-irradiated to covalently stabilize the PPO-surface association. PEO layer stability was evaluated by triblock resistance to elution by SDS, and layer uniformity was evaluated by fibrinogen repulsion. Introduction of nisin to uncoated or triblock-coated microspheres produced a significant positive change in surface charge (zeta potential) as a result of adsorption of the cationic peptide. In sequential adsorption experiments, the introduction of fibrinogen to nisin-loaded triblock layers caused a decrease in zeta potential that was consistent with partial elution of nisin and/or preferential location of fibrinogen at the interface. This change was substantially more pronounced for uncoated than triblock-coated silica, indicating that the PEO layer offers enhanced resistance to nisin elution.

A novel system of polymorphic and diverse NK cell receptors in primates.

There are two main classes of natural killer (NK) cell receptors in mammals, the killer cell immunoglobulin-like receptors (KIR) and the structurally unrelated killer cell lectin-like receptors (KLR). While KIR represent the most diverse group of NK receptors in all primates studied to date, including humans, apes, and Old and New World monkeys, KLR represent the functional equivalent in rodents. Here, we report a first digression from this rule in lemurs, where the KLR (CD94/NKG2) rather than KIR constitute the most diverse group of NK cell receptors. We demonstrate that natural selection contributed to such diversification in lemurs and particularly targeted KLR residues interacting with the peptide presented by MHC class I ligands. We further show that lemurs lack a strict ortholog or functional equivalent of MHC-E, the ligands of non-polymorphic KLR in "higher" primates. Our data support the existence of a hitherto unknown system of polymorphic and diverse NK cell receptors in primates and of combinatorial diversity as a novel mechanism to increase NK cell receptor repertoire.

Synthesis and antibacterial activity of nisin-containing block copolymers.

Nisin, an antibacterial peptide proven to be an effective inhibitor of Gram-positive bacteria, was incorporated into novel block copolymer constructs and tested for retained antibacterial activity. Covalent coupling was achieved by chemical modification of the N-terminal isoleucine to introduce a thiol group. Thiolated-nisin derivatives were then linked to poly[ethylene oxide]-poly[propylene oxide]-poly[ethylene oxide] (PEO-PPO-PEO) triblocks that had been end-activated such that terminal hydroxyl groups of the PEO chains were replaced with pyridyl disulfide moieties. The nisin-containing block copolymers were separated from free nisin by dialysis and showed antimicrobial activity against the Gram-positive indicator strain Pediococcus pentosaceus. The contribution to antimicrobial activity from nisin that was covalently linked was not distinguished from the contribution of nisin that had associated with the PEO-PPO-PEO triblocks through noncovalent interactions. However, nisin that was covalently linked showed activity upon reduction of the disulfide bond and release from the end-activated PEO.

Nisin antimicrobial activity and structural characteristics at hydrophobic surfaces coated with the PEO-PPO-PEO triblock surfactant Pluronic F108.

The antimicrobial peptide nisin has been observed to preferentially locate at surfaces coated with the poly[ethylene oxide]-poly[propylene oxide]-poly[ethylene oxide] (PEO-PPO-PEO) surfactant Pluronic F108, to an extent similar to its adsorption at uncoated, hydrophobic surfaces. In order to evaluate nisin function following its adsorption to surfaces presenting pendant PEO chains, the antimicrobial activity of nisin-loaded, F108-coated polystyrene microspheres and F108-coated polyurethane catheter segments was evaluated against the Gram-positive indicator strain, Pediococcus pentosaceus. The retained biological activity of these nisin-loaded layers was evaluated after incubation in the presence and absence of blood proteins, for contact periods up to one week. While an increase in serum protein concentration reduced the retained activity on both bare hydrophobic and F108-coated materials, F108-coated surfaces retained more antimicrobial activity than the uncoated surfaces. Circular dichroism spectroscopy experiments conducted with nisin in the presence of F108-coated and uncoated, silanized silica nanoparticles suggested that nisin experienced conformational rearrangement at a greater rate and to a greater extent on bare hydrophobic surfaces relative to F108-coated surfaces. These results support the notion that immobilized, pendant PEO chains confer some degree of conformational stability to nisin while also inhibiting its exchange by blood proteins.

Nisin adsorption to hydrophobic surfaces coated with the PEO-PPO-PEO triblock surfactant Pluronic F108.

The adsorption and elution of the antimicrobial peptide nisin at hydrophobic, silanized silica surfaces coated with the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) surfactant Pluronic F108 were measured in situ, with ellipsometry. While such layers are known to inhibit protein adsorption, nisin was observed to adsorb in multilayer quantities, to an extent similar to its adsorption at uncoated, hydrophobic surfaces. The rates of nisin adsorption and elution were generally slower at F108-coated surfaces. And, the sequential adsorption of nisin, including two adsorption-elution cycles at each surface, showed greater differences in adsorption rates between the first and second adsorption cycles, when evaluated at identical mass density, for uncoated relative to F108-coated surfaces. These results indicate that nisin adsorption occurs via "entrapment" within the PEO brush layer at F108-coated surfaces, in this way slowing adsorption and spontaneous elution, and inhibiting post-adsorptive molecular rearrangements by reducing the lateral mobility of nisin. While F108-coated layers rejected adsorption of serum albumin, sequential adsorption experiments carried out with nisin and albumin showed a low level of albumin adsorption when nisin was present at the interface.

Ketoconazole, a cytochrome P450 3A4 inhibitor, markedly increases concentrations of levo-acetyl-alpha-methadol in opioid-naive individuals.

BACKGROUND: Levo-acetyl-alpha-methadol (LAAM) exerts most of it mu-agonist activity through the action of its 2 N-demethylation metabolites, norLAAM and dinorLAAM. The N-demethylation of LAAM to norLAAM and norLAAM to dinorLAAM is primarily performed by cytochrome P450s (CYP) in the 3A family. No previous studies have been conducted to determine the effect of in vivo inhibition of CYP3A on the pharmacokinetics and pharmacodynamics of LAAM. METHODS: Oral LAAM (5 mg/70 kg) was administered on 2 occasions in a single-blind, randomized crossover design to 13 opioid-naive subjects (6 women and 7 men) 1 hour after pretreatment with 400 mg ketoconazole or placebo. Blood and urine samples were collected at defined intervals over 240- and 96-hour periods, respectively; LAAM, norLAAM, and dinorLAAM concentrations were determined by liquid chromatography-tandem mass spectrometry. Physiologic and subjective measures were collected for up to 72 hours. RESULTS: Results are presented as the geometric mean with 90% confidence intervals of individual ratios of ketoconazole to placebo sessions. Coadministration of ketoconazole and LAAM resulted in a 3.22-fold (2.53-4.10, P <.001) and 5.29-fold (4.24-6.61, P <.001) increase in the maximum plasma concentration (Cmax) and area under the curve (AUC) of LAAM. The values for time to Cmax (tmax) of norLAAM and dinorLAAM were increased 2.43-fold (1.92-3.08, P <.001) and 11.6-fold (8.36-16.1, P <.001), with 0.77-fold (0.67-0.87, P <.005) and 0.55-fold (0.49-0.60, P <.001) decreases in their respective Cmax values. The AUCs of norLAAM and dinorLAAM were increased 2.25-fold (1.96-2.58, P <.001) and 1.21-fold (1.12-1.32, P <.005), respectively. Pupil diameter was significantly decreased by LAAM after both placebo and ketoconazole pretreatment; ketoconazole increased the tmax for miosis 2.92-fold (2.01-4.25, P <.001). Other physiologic measures and numerous subjective effects measures were significantly affected by LAAM; however, few significant effects of ketoconazole pretreatment were observed on these outcomes. CONCLUSION: A single dose of ketoconazole causes a significant pharmacokinetic drug interaction with a single dose of LAAM that results in increased LAAM concentrations relative to norLAAM and dinorLAAM at early time points. Coadministration also results in prolongation of the appearance of its active metabolites and a concomitant prolongation of miosis, a sensitive dynamic index of mu-opioid action. The clinically relevant increase in LAAM concentrations and prolongation of plasma LAAM metabolites may affect physiologic function, such as QT intervals, suggesting that coadministration of LAAM and CYP3A4 inhibitors should be contraindicated.

Inhibition of accelerated graft arteriosclerosis by gene transfer of soluble fibroblast growth factor receptor-1 in rat aortic transplants.

OBJECTIVE: Because increased fibroblast growth factor-1 (FGF-1) and FGF receptor (FGFR) expression correlate with the development of accelerated graft arteriosclerosis in transplanted human hearts, this study sought to determine whether local gene transfer of soluble FGFR-1, capable of binding both FGF-1 and FGF-2, could blunt the development of accelerated graft arteriosclerosis in the rat aortic transplant model. METHODS AND RESULTS: A construct encoding the FGFR-1 ectodomain, capable of neutralizing FGF-2 action, was expressed in rat aortic allografts, using adenoviral gene transfer at the time of transplantation. Neointima formation was inhibited in aortic allografts transduced with soluble FGFR-1, compared with allografts transduced with Null virus. CONCLUSIONS: FGFs play a causal role in the development of accelerated graft arteriosclerosis in the rat aortic transplant model. Targeted interruption of FGF function could potentially reduce neointima formation in patients with heart and kidney transplants.

Receptor interactions involved in adenoviral-mediated gene delivery after systemic administration in non-human primates.

Adenovirus serotype 5 (Ad5)-based vectors can bind at least three separate cell surface receptors for efficient cell entry: the coxsackie-adenovirus receptor (CAR), alpha nu integrins, and heparan sulfate glycosaminoglycans (HSG). To address the role of each receptor involved in adenoviral cell entry, we mutated critical amino acids in fiber or penton to inhibit receptor interaction. A series of five adenoviral vectors was prepared and the biodistribution of each was previously characterized in mice. To evaluate possible species differences in Ad vector tropism, we characterized the effects of each detargeting mutation in non-human primates after systemic delivery to confirm our conclusions made in mice. In non-human primates, CAR was found to have minimal effects on vector delivery to all organs examined including liver and spleen. Cell-surface alpha nu integrins played a significant role in delivery of vector to the spleen, lung and kidney. The fiber shaft mutation S*, which presumably inhibits HSG binding, was found to significantly decrease delivery to all organs examined. The ability to detarget the liver corresponded with decreased elevations in liver serum enzymes (aspartate transferase [AST] and alanine transferase [ALT]) 24 hr after vector administration and also in serum interleukin (IL)-6 levels 6 hr after vector administration. The biodistribution data generated in cynomolgus monkeys correspond with those data derived from mice, demonstrating that CAR binding is not the major determinant of viral tropism in vivo. Vectors containing the fiber shaft modification may provide for a detargeted adenoviral vector on which to introduce new tropisms for the development of targeted, systemically deliverable adenoviral vectors for human clinical application.

Adenovirus serotype 5 fiber shaft influences in vivo gene transfer in mice.

Adenoviral vectors used in gene therapy are predominantly derived from adenovirus serotype 5 (Ad5), which infects a broad range of cells. Ad5 cell entry involves interactions with the coxsackie-adenovirus receptor (CAR) and integrins. To assess these receptors in vivo, we mutated amino acid residues in fiber and penton that are involved in receptor interaction and showed that CAR and integrins play a minor role in hepatic transduction but that integrins can influence gene delivery to other tissues. These data suggest that an alternative entry pathway exists for hepatocyte transduction in vivo that is more important than CAR or integrins. In vitro data suggest a role for heparan sulfate glycosaminoglycans (HSG) in adenovirus transduction. The role of the fiber shaft in liver uptake was examined by introducing specific amino acid changes into a putative HSG-binding motif contained within the shaft or by preparing fiber shaft chimeras between Ad5 and Ad35 fibers. Results were obtained that demonstrate that the Ad5 fiber shaft can influence gene transfer both in vitro and to the liver in vivo. These observations indicate that the currently accepted two-step entry pathway, which involves CAR and integrins, described for adenoviral infection in vitro, is not used for hepatic gene transfer in vivo. In contrast, alpha(v) integrins influence gene delivery to the lung, spleen, heart, and kidney. The detargeted vector constructs described here may provide a foundation for the development of targeted adenoviral vectors.

Overexpression of soluble fas attenuates transplant arteriosclerosis in rat aortic allografts.

BACKGROUND: The killing of vascular cells by activated macrophages is an important step in the process of destabilization of the arterial wall. The death receptor Fas is implicated in vascular cell death. Hence, we extended our studies in a rat aortic allograft model, using adenovirus-mediated overexpression of soluble Fas (sFas) to block Fas binding to Fas ligand (Fas-L). The contribution of Fas to vascular cell injury and consequent transplant arteriosclerosis was investigated. METHODS AND RESULTS: Activated monocytes in the presence of macrophage colony-stimulating factor induce endothelial cell apoptosis in vitro, which was significantly inhibited by adenovirus-mediated sFas overexpression. Next, donor rat abdominal aortas were either untreated or transduced with adenoviruses encoding (1) rat soluble Fas (Ad3rsFas), (2) no insert (Ad3Null), and (3) beta-galactosidase (Ad3nBg). A total of 175 aortic grafts were harvested 2 to 90 days after transplantation. Vascular cell apoptosis and CD45+ cell infiltration were significantly reduced in Ad3rsFas-transduced aortas, as compared with control allografts. Moreover, the control allografts developed marked intimal thickening, whereas Ad3rsFas-transduced allografts had significantly less neointima until the 90-day time point. CONCLUSIONS: sFas overexpression protects the integrity of the vessel wall from immune injury and attenuates transplant arteriosclerosis.