Convection-enhanced delivery of M13 bacteriophage to the brain

Genetically engineered filamentous phage for bacterial detection using magnetic resonance imaging

Detecting bacterial cells with high specificity in deep tissues is challenging. Optical probes provide specificity, but are limited by the scattering and absorption of light in biological tissues. Conversely, magnetic resonance imaging (MRI) allows unfettered access to deep tissues, but lacks contrast agents for detecting specific bacterial strains. Here, we introduce a biomolecular platform that combines both capabilities by exploiting the modularity of M13 phage to target bacteria with tunable specificity and allow deep-tissue imaging using T1-weighted MRI. We engineered two types of phage probes: one for detecting the phage's natural host, viz., F-pilus expressing E. coli; and the other for detecting a different (F-negative) bacterial target, V. cholerae. We show that these phage sensors generate 3-9-fold stronger T1 relaxation upon recognizing target cells relative to non-target bacteria. We further establish a preliminary proof-of-concept for in vivo applications, by demonstrating that phage-labeled bacteria can be detected in mice using MRI. The framework developed in this study may have potential utility in a broad range of applications, from basic biomedical research to in situ diagnostics, which require methods to detect and track specific bacteria in the context of intact living systems.

Next-generation viral nanoparticles for targeted delivery of therapeutics: Fundamentals, methods, biomedical applications, and challenges

INTRODUCTION

Viral nanoparticles (VNPs) are virus-based nanocarriers that have been studied extensively and intensively for biomedical applications. However, their clinical translation is relatively low compared to the predominating lipid-based nanoparticles. Therefore, this article describes the fundamentals, challenges, and solutions of the VNP-based platform, which will leverage the development of next-generation VNPs.

AREAS COVERED

Different types of VNPs and their biomedical applications are reviewed comprehensively. Strategies and approaches for cargo loading and targeted delivery of VNPs are examined thoroughly. The latest developments in controlled release of cargoes from VNPs and their mechanisms are highlighted too. The challenges faced by VNPs in biomedical applications are identified, and solutions are provided to overcome them.

EXPERT OPINION

In the development of next-generation VNPs for gene therapy, bioimaging and therapeutic deliveries, focus must be given to reduce their immunogenicity, and increase their stability in the circulatory system. Modular virus-like particles (VLPs) which are produced separately from their cargoes or ligands before all the components are coupled can speed up clinical trials and commercialization. In addition, removal of contaminants from VNPs, cargo delivery across the blood brain barrier (BBB), and targeting of VNPs to organelles intracellularly are challenges that will preoccupy researchers in this decade.

Phage Interactions with the Nervous System in Health and Disease

The central nervous system manages all of our activities (e.g., direct thinking and decision-making processes). It receives information from the environment and responds to environmental stimuli. Bacterial viruses (bacteriophages, phages) are the most numerous structures occurring in the biosphere and are also found in the human organism. Therefore, understanding how phages may influence this system is of great importance and is the purpose of this review. We have focused on the effect of natural bacteriophages in the central nervous system, linking them to those present in the gut microbiota, creating the gut-brain axis network, as well as their interdependence. Importantly, based on the current knowledge in the field of phage application (e.g., intranasal) in the treatment of bacterial diseases associated with the brain and nervous system, bacteriophages may have significant therapeutic potential. Moreover, it was indicated that bacteriophages may influence cognitive processing. In addition, phages (via phage display technology) appear promising as a targeted therapeutic tool in the treatment of, among other things, brain cancers. The information collected and reviewed in this work indicates that phages and their impact on the nervous system is a fascinating and, so far, underexplored field. Therefore, the aim of this review is not only to summarize currently available information on the association of phages with the nervous system, but also to stimulate future studies that could pave the way for novel therapeutic approaches potentially useful in treating bacterial and non-bacterial neural diseases.

Engineered M13 phage as a novel therapeutic bionanomaterial for clinical applications: From tissue regeneration to cancer therapy

Bacteriophages (phages) are nanostructured viruses with highly selective antibacterial properties that have gained attention beyond eliminating bacteria. Specifically, M13 phages are filamentous phages that have recently been studied in various aspects of nanomedicine due to their biological advantages and more compliant engineering capabilities over other phages. Having nanofiber-like morphology, M13 phages can reach varied target sites and self-assemble into multidimensional scaffolds in a relatively safe and stable way. In addition, genetic modification of the coat proteins enables specific display of peptides and antibodies on the phages, allowing for precise and individualized medicine. M13 phages have also been subjected to novel engineering approaches, including phage-based bionanomaterial engineering and phage-directed nanomaterial combinations that enhance the bionanomaterial properties of M13 phages. In view of these features, researchers have been able to utilize M13 phages for therapeutic applications such as drug delivery, biodetection, tissue regeneration, and targeted cancer therapy. In particular, M13 phages have been utilized as a novel bionanomaterial for precisely mimicking natural tissue environment in order to overcome the shortage in tissue and organ donors. Hence, in this review, we address the recent studies and advances of using M13 phages in the field of nanomedicine as therapeutic agents based upon their characteristics as novel bionanomaterial with biomolecules displayed. This paper also emphasizes the novel engineering approach that enhances M13 phage's bionanomaterial capabilities. Current limitations and future approaches are also discussed to provide insight in further progress for M13 phage-based clinical applications.

Mechanism of extracellular space changes in cryptococcal brain granuloma revealed by MRI tracer

Purpose

This study aimed to investigate the changes in extracellular space (ECS) in cryptococcal brain granuloma and its pathological mechanism.

Materials and methods

The animal model of cryptococcal brain granuloma was established by injecting 1 × 10⁶ CFU/ml of Cryptococcus neoformans type A suspension into the caudate nucleus of Sprague-Dawley rats with stereotactic technology. The infection in the brain was observed by conventional MRI scanning on days 14, 21, and 28 of modeling. The tracer-based MRI with a gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) as a magnetic tracer was performed on the rats with cryptococcal granuloma and the rats in the control group. The parameters of ECS in each area of cryptococcal brain granuloma were measured. The parameters of ECS in the two groups were compared by independent sample t-test, and the changes in ECS and its mechanism were analyzed.

Results

Up to 28 days of modeling, the success rate of establishing the brain cryptococcal granuloma model with 1 × 10⁶ CFU/ml Cryptococcus neoformans suspension was 60%. In the internal area of cryptococcal granuloma, the effective diffusion coefficient D* was significantly higher than that of the control group (t = 2.76, P < 0.05), and the same trend showed in the volume ratio α (t = 3.71, P < 0.05), the clearance rate constant k (t = 3.137, P < 0.05), and the tracer half-life T_1/2 (t = 3.837, P < 0.05). The tortuosity λ decreased compared with the control group (t = -2.70, P < 0.05). At the edge of the cryptococcal granuloma, the D* and α decreased, while the λ increased compared with the control group (D*:t = -6.05, P < 0.05; α: t = -4.988, P < 0.05; λ: t = 6.222, P < 0.05).

Conclusion

The internal area of the lesion demonstrated a quicker, broader, and more extended distribution of the tracer, while the edge of the lesion exhibited a slower and narrower distribution. MRI tracer method can monitor morphological and functional changes of ECS in pathological conditions and provide a theoretical basis for the treatment via ECS.

Focused Delivery of Chemotherapy to Augment Surgical Management of Brain Tumors

Chemotherapy as an adjuvant therapy that has largely failed to significantly improve outcomes for aggressive brain tumors; some reasons include a weak blood brain barrier penetration and tumor heterogeneity. Recently, there has been interest in designing effective ways to deliver chemotherapy to the tumor. In this review, we discuss the mechanisms of focused chemotherapies that are currently under investigation. Nanoparticle delivery demonstrates both a superior permeability and retention. However, thus far, it has not demonstrated a therapeutic efficacy for brain tumors. Convection-enhanced delivery is an invasive, yet versatile method, which appears to have the greatest potential. Other vehicles, such as angiopep-2 decorated gold nanoparticles, polyamidoamine dendrimers, and lipid nanostructures have demonstrated efficacy through sustained release of focused chemotherapy and have either improved cell death or survival in humans or animal models. Finally, focused ultrasound is a safe and effective way to disrupt the blood brain barrier and augment other delivery methods. Clinical trials are currently underway to study the safety and efficacy of these methods in combination with standard of care.

Viral metagenomics combined with metabolomics reveals the role of gut viruses in mouse model of depression

Depression is a heterogeneous mental disorder that has been linked to disturbances in the gut microbiome. As an essential part of the gut microbiome, gut virome may play critical roles in disease progression and development. However, the relationship between the effect of gut virome on neurotransmitter metabolism and depression is unknown. We evaluated the alterations of gut virome and neurotransmitters in chronic restraint stress (CRS)-induced mouse model of depression based on viral metagenomics and LC-MS/MS metabolomics analyses. The results reveal that the gut virome profile of CRS group differed significantly from CON group. Microviridae was the most abundant differential viral family in both groups, followed by Podoviridae, while Siphoviridae was only enriched in CRS group of the top 100 differential viruses. The differential viruses that predicted to Enterobacteriaceae phage, Gammaproteobacteria phage and Campylobacteraceae phage were enriched in CRS group. Furthermore, 12 differential neurotransmitters primarily involved in the tryptophan metabolism pathway were altered in depressive-like mice. Besides, tryptamine and 5-methoxytryptamine hydrochloride were strongly associated with differential viruses belonging to Podoviridae and Microviridae. Our findings provide new insight into understanding the potential role of the gut virome and metabolites in depression.

Gut Virome: Role and Distribution in Health and Gastrointestinal Diseases

The study of the intestinal microbiome is an evolving field of research that includes comprehensive analysis of the vast array of microbes – bacterial, archaeal, fungal, and viral. Various gastrointestinal (GI) diseases, such as Crohn’s disease and ulcerative colitis, have been associated with instability of the gut microbiota. Many studies have focused on importance of bacterial communities with relation to health and disease in humans. The role of viruses, specifically bacteriophages, have recently begin to emerge and have profound impact on the host. Here, we comprehensively review the importance of viruses in GI diseases and summarize their influence in the complex intestinal environment, including their biochemical and genetic activities. We also discuss the distribution of the gut virome as it relates with treatment and immunological advantages. In conclusion, we suggest the need for further studies on this critical component of the intestinal microbiome to decipher the role of the gut virome in human health and disease.

Filamentous Bacteriophage-A Powerful Carrier for Glioma Therapy

Glioma is a life-threatening malignant tumor. Resistance to traditional treatments and tumor recurrence present major challenges in treating and managing this disease, consequently, new therapeutic strategies must be developed. Crossing the blood-brain barrier (BBB) is another challenge for most drug vectors and therapy medications. Filamentous bacteriophage can enter the brain across the BBB. Compared to traditional drug vectors, phage-based drugs offer thermodynamic stability, biocompatibility, homogeneity, high carrying capacity, self-assembly, scalability, and low toxicity. Tumor-targeting peptides from phage library and phages displaying targeting peptides are ideal drug delivery agents. This review summarized recent studies on phage-based glioma therapy and shed light on the developing therapeutics phage in the personalized treatment of glioma.

Interactions of Bacteriophages with Animal and Human Organisms-Safety Issues in the Light of Phage Therapy

Bacteriophages are viruses infecting bacterial cells. Since there is a lack of specific receptors for bacteriophages on eukaryotic cells, these viruses were for a long time considered to be neutral to animals and humans. However, studies of recent years provided clear evidence that bacteriophages can interact with eukaryotic cells, significantly influencing the functions of tissues, organs, and systems of mammals, including humans. In this review article, we summarize and discuss recent discoveries in the field of interactions of phages with animal and human organisms. Possibilities of penetration of bacteriophages into eukaryotic cells, tissues, and organs are discussed, and evidence of the effects of phages on functions of the immune system, respiratory system, central nervous system, gastrointestinal system, urinary tract, and reproductive system are presented and discussed. Modulations of cancer cells by bacteriophages are indicated. Direct and indirect effects of virulent and temperate phages are discussed. We conclude that interactions of bacteriophages with animal and human organisms are robust, and they must be taken under consideration when using these viruses in medicine, especially in phage therapy, and in biotechnological applications.

Convection-enhanced drug delivery for glioblastoma: a review

INTRODUCTION

Convection-enhanced delivery (CED) is a method of targeted, local drug delivery to the central nervous system (CNS) that bypasses the blood-brain barrier (BBB) and permits the delivery of high-dose therapeutics to large volumes of interest while limiting associated systemic toxicities. Since its inception, CED has undergone considerable preclinical and clinical study as a safe method for treating glioblastoma (GBM). However, the heterogeneity of both, the surgical procedure and the mechanisms of action of the agents studied-combined with the additional costs of performing a trial evaluating CED-has limited the field's ability to adequately assess the durability of any potential anti-tumor responses. As a result, the long-term efficacy of the agents studied to date remains difficult to assess.

MATERIALS AND METHODS

We searched PubMed using the phrase "convection-enhanced delivery and glioblastoma". The references of significant systematic reviews were also reviewed for additional sources. Articles focusing on physiological and physical mechanisms of CED were included as well as technological CED advances.

RESULTS

We review the history and principles of CED, procedural advancements and characteristics, and outcomes from key clinical trials, as well as discuss the potential future of this promising technique for the treatment of GBM.

CONCLUSION

While the long-term efficacy of the agents studied to date remains difficult to assess, CED remains a promising technique for the treatment of GBM.

Convection Enhanced Delivery of Topotecan for Gliomas: A Single-Center Experience

A key limitation to glioma treatment involves the blood brain barrier (BBB). Convection enhanced delivery (CED) is a technique that uses a catheter placed directly into the brain parenchyma to infuse treatments using a pressure gradient. In this manuscript, we describe the physical principles behind CED along with the common pitfalls and methods for optimizing convection. Finally, we highlight our institutional experience using topotecan CED for the treatment of malignant glioma.

Mechanical characterization of a fiberoptic microneedle device for controlled delivery of fluids and photothermal excitation

Current clinical approaches for treating pancreatic cancer have been demonstrated as ineffective at improving midterm survival. A primary obstacle to local drug delivery is the desmoplastic nature of the peritumoral environment, which acts as a significant barrier to circulating macromolecules. To address this need, our group presents a sharp fiberoptic microcatheter capable of accessing the pancreas through transduodenal endoscope and penetrating a tumor to locally co-deliver photothermal and fluid-based therapies. Experiments sought to characterize the mechanical penetration capabilities and fluid mechanics of the fiberoptic microneedle design. A refined off-center fusion splicing technique was developed for joining a multimode fiber to the annular core of a light-guiding capillary, allowing light transmission with minimal optical loss. A novel and frugal technique for assessing the penetration force of the microneedle was conducted in a bovine gelatin tissue phantom with a Young's modulus stiffer than the high range for pancratic tissue or tumor. Buckling forces for different microneedle lengths were measured and compared against theoretical values obtained from Euler's Critical Load equation under fixed-pinned column conditions. Hydraulic resistance of different capillary lengths was evaluated and compared against the theoretical values from Hagen-Poiseuille's law, allowing assessment of contributions from different segments of the device. The results demonstrated that the microcatheter can robustly and repeatably penetrate a soft tissue phantom chosen to be a conservative model of pancreatic tissue for penetration properties. Experiments showed that a 1.5 N insertion force was required for phantom penetration with a 45° beveled needle at a 5 mm unsupported length, while the critical buckling load was measured to be approximately 4 N. In addition, the design was demonstrated to efficiently transport 1064 nm light and aqueous fluids with a 70-75% light coupling efficiency and 12,200 Pa.s/μl hydraulic resistance, respectively. These findings motivate the FMD's further development as a treatment platform for pancreatic cancer.

Validation of an effective implantable pump-infusion system for chronic convection-enhanced delivery of intracerebral topotecan in a large animal model

OBJECTIVE

Intracerebral convection-enhanced delivery (CED) has been limited to short durations due to a reliance on externalized catheters. Preclinical studies investigating topotecan (TPT) CED for glioma have suggested that prolonged infusion improves survival. Internalized pump-catheter systems may facilitate chronic infusion. The authors describe the safety and utility of long-term TPT CED in a porcine model and correlation of drug distribution through coinfusion of gadolinium.

METHODS

Fully internalized CED pump-catheter systems were implanted in 12 pigs. Infusion algorithms featuring variable infusion schedules, flow rates, and concentrations of a mixture of TPT and gadolinium were characterized over increasing intervals from 4 to 32 days. Therapy distribution was measured using gadolinium signal on MRI as a surrogate. A 9-point neurobehavioral scale (NBS) was used to identify side effects.

RESULTS

All animals tolerated infusion without serious adverse events. The average NBS score was 8.99. The average maximum volume of distribution (Vdmax) in chronically infused animals was 11.30 mL and represented 32.73% of the ipsilateral cerebral hemispheric volume. Vdmax was achieved early during infusions and remained relatively stable despite a slight decline as the infusion reached steady state. Novel tissue TPT concentrations measured by liquid chromatography mass spectroscopy correlated with gadolinium signal intensity on MRI (p = 0.0078).

CONCLUSIONS

Prolonged TPT-gadolinium CED via an internalized system is safe and well tolerated and can achieve a large Vdmax, as well as maintain a stable Vd for up to 32 days. Gadolinium provides an identifiable surrogate for measuring drug distribution. Extended CED is potentially a broadly applicable and safe therapeutic option in select patients.

Interactions between Bacteriophages and Eukaryotic Cells

As the name implies, bacteriophage is a bacterium-specific virus. It infects and kills the bacterial host. Bacteriophages have gained attention as alternative antimicrobial entities in the science community in the western world since the alarming rise of antibiotic resistance among microbes. Although generally considered as prokaryote-specific viruses, recent studies indicate that bacteriophages can interact with eukaryotic organisms, including humans. In the current review, these interactions are divided into two categories, i.e., indirect and direct interactions, with the involvement of bacteriophages, bacteria, and eukaryotes. We discuss bacteriophage-related diseases, transcytosis of bacteriophages, bacteriophage interactions with cancer cells, collaboration of bacteriophages and eukaryotes against bacterial infections, and horizontal gene transfer between bacteriophages and eukaryotes. Such interactions are crucial for understanding and developing bacteriophages as the therapeutic agents and pharmaceutical delivery systems. With the advancement and combination of in silico, in vitro, and in vivo approaches and clinical trials, bacteriophages definitely serve as useful repertoire for biologic target-based drug development to manage many complex diseases in the future.

Convection-Enhanced Delivery of Muscimol Into the Bilateral Subthalamic Nuclei of Nonhuman Primates

BACKGROUND

Muscimol is a gamma-aminobutyric acid receptor agonist that selectively and temporarily inhibits neurons. Local bolus injection of muscimol has been used experimentally to inhibit neuronal populations within discrete anatomical structures and discern their physiological function.

OBJECTIVE

To determine the safety and behavioral effects of convection-enhanced delivery of muscimol into the bilateral subthalamic nuclei (STN) of nonhuman primate rhesus macaques (NHPs).

METHODS

Six awake NHPs underwent co-infusion of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA), a surrogate magnetic resonance imaging (MRI) tracer, with increasing concentrations of muscimol for behavioral and histological assessment. Three other NHPs were co-infused with Gd-DTPA and 3H-muscimol into the STN to determine muscimol distribution by MRI and autoradiography. Two NHPs underwent microcatheter implantation without muscimol infusion for control comparison.

RESULTS

MRI revealed selective and complete perfusion of the bilateral STN in animals infused with Gd-DTPA and muscimol. No abnormal movements occurred at 0.125 mM. Muscimol doses between 0.25 and 4.4 mM resulted in transient, dose-dependent hyperkinesia. Muscimol (8.8 mM) resulted in severe bilateral dyskinesias, ballistic movements, and sedation. An 88.8 mM dose produced unresponsiveness in 1 animal. Infusion-related pathological abnormities or toxicity was not present on histological examination. MRI distribution of co-infused Gd-DTPA was similar to autoradiographic distribution of 3H-muscimol (Vd; R = 0.94). Mean Vd of infused animals was 37.9 mm3 ± 11.7 mm3 and mean Vd: Vi 7.6 ± 2.3.

CONCLUSION

Bilateral convection-enhanced delivery of muscimol into the primate STN resulted in dose-related hyperkinetic movements that resolved after stopping the infusion. Muscimol was not toxic to brain tissue. Gd-DTPA accurately tracked muscimol distribution.

Temporal Characterization of Blood-Brain Barrier Disruption with High-Frequency Electroporation

Treatment of intracranial disorders suffers from the inability to accumulate therapeutic drug concentrations due to protection from the blood–brain barrier (BBB). Electroporation-based therapies have demonstrated the capability of permeating the BBB, but knowledge of the longevity of BBB disruption (BBBD) is limited. In this study, we quantify the temporal, high-frequency electroporation (HFE)-mediated BBBD in an in vivo healthy rat brain model. 40 male Fisher rats underwent HFE treatment; two blunt tipped monopolar electrodes were advanced into the brain and 200 bursts of HFE were delivered at a voltage-to-distance ratio of 600 V/cm. BBBD was verified with contrast enhanced T1W MRI (gadopentetate dimeglumine) and pathologically (Evans blue dye) at time points of 1, 24, 48, 72, and 96 h after HFE. Contrast enhanced T1W scans demonstrated BBBD for 1 to 72 h after HFE but intact BBB at 96 h. Histologically, tissue damage was restricted to electrode insertion tracks. BBBD was induced with minimal muscle contractions and minimal cell death attributed to HFE. Numerical modeling indicated that brief BBBD was induced with low magnitude electric fields, and BBBD duration increased with field strength. These data suggest the spatiotemporal characteristics of HFE-mediated BBBD may be modulated with the locally applied electric field.

Arming Filamentous Bacteriophage, a Nature-Made Nanoparticle, for New Vaccine and Immunotherapeutic Strategies

The pharmaceutical use of bacteriophages as safe and inexpensive therapeutic tools is collecting renewed interest. The use of lytic phages to fight antibiotic-resistant bacterial strains is pursued in academic and industrial projects and is the object of several clinical trials. On the other hand, filamentous bacteriophages used for the phage display technology can also have diagnostic and therapeutic applications. Filamentous bacteriophages are nature-made nanoparticles useful for their size, the capability to enter blood vessels, and the capacity of high-density antigen expression. In the last decades, our laboratory focused its efforts in the study of antigen delivery strategies based on the filamentous bacteriophage 'fd', able to trigger all arms of the immune response, with particular emphasis on the ability of the MHC class I restricted antigenic determinants displayed on phages to induce strong and protective cytotoxic responses. We showed that fd bacteriophages, engineered to target mouse dendritic cells (DCs), activate innate and adaptive responses without the need of exogenous adjuvants, and more recently, we described the display of immunologically active lipids. In this review, we will provide an overview of the reported applications of the bacteriophage carriers and describe the advantages of exploiting this technology for delivery strategies.

Bacteriophage interactions with mammalian tissue: Therapeutic applications

The human body is a large reservoir for bacterial viruses known as bacteriophages (phages), which participate in dynamic interactions with their bacterial and human hosts that ultimately affect human health. The current growing interest in human resident phages is paralleled by new uses of phages, including the design of engineered phages for therapeutic applications. Despite the increasing number of clinical trials being conducted, the understanding of the interaction of phages and mammalian cells and tissues is still largely unknown. The presence of phages in compartments within the body previously considered purely sterile, suggests that phages possess a unique capability of bypassing anatomical and physiological barriers characterized by varying degrees of selectivity and permeability. This review will discuss the direct evidence of the accumulation of bacteriophages in various tissues, focusing on the unique capability of phages to traverse relatively impermeable barriers in mammals and its relevance to its current applications in therapy.

Phage therapy: What factors shape phage pharmacokinetics and bioavailability? Systematic and critical review

Bacteriophages are not forgotten viruses anymore: scientists and practitioners seek to understand phage pharmacokinetics in animals and humans, investigating bacteriophages as therapeutics, nanocarriers or microbiome components. This review provides a comprehensive overview of factors that determine phage circulation, penetration, and clearance, and that in consequence determine phage applicability for medicine. It makes use of experimental data collected by the phage community so far (PubMed 1924‐2016, including non‐English reports), combining elements of critical and systematic review.

This study covers phage ability to enter a system by various routes of administration, how (and if) the phage may access various tissues and organs, and finally what mechanisms determine the courses of phage clearance. The systematic review method was applied to analyze (i) phage survival in the gut (gut transit) and (ii) phage ability to enter the mammalian system by many administration routes. Aspects that have not yet been covered by a sufficient number of reports for mathematical analysis, as well as mechanisms underlying trends, are discussed in the form of a critical review.

In spite of the extraordinary diversity of bacteriophages and possible phage applications, the analysis revealed that phage morphology, phage specificity, phage dose, presence of sensitive bacteria or the characteristics of treated individuals (age, taxonomy) may affect phage bioavailability in animals and humans. However, once phages successfully enter the body, they reach most organs, including the central nervous system. Bacteriophages are cleared mainly by the immune system: innate immunity removes phages even when no specific response to bacteriophages has yet developed.

A bacteriophages journey through the human body

The human body is colonized by a diverse collective of microorganisms, including bacteria, fungi, protozoa and viruses. The smallest entity of this microbial conglomerate are the bacterial viruses. Bacteriophages, or phages for short, exert significant selective pressure on their bacterial hosts, undoubtedly influencing the human microbiome and its impact on our health and well-being. Phages colonize all niches of the body, including the skin, oral cavity, lungs, gut, and urinary tract. As such our bodies are frequently and continuously exposed to diverse collections of phages. Despite the prevalence of phages throughout our bodies, the extent of their interactions with human cells, organs, and immune system is still largely unknown. Phages physically interact with our mucosal surfaces, are capable of bypassing epithelial cell layers, disseminate throughout the body and may manipulate our immune system. Here, I establish the novel concept of an "intra-body phageome," which encompasses the collection of phages residing within the classically "sterile" regions of the body. This review will take a phage-centric view of the microbiota, human body, and immune system with the ultimate goal of inspiring a greater appreciation for both the indirect and direct interactions between bacteriophages and their mammalian hosts.

A human gut phage catalog correlates the gut phageome with type 2 diabetes

BACKGROUND

Substantial efforts have been made to link the gut bacterial community to many complex human diseases. Nevertheless, the gut phages are often neglected.

RESULTS

In this study, we used multiple bioinformatic methods to catalog gut phages from whole-community metagenomic sequencing data of fecal samples collected from both type II diabetes (T2D) patients (n = 71) and normal Chinese adults (n = 74). The definition of phage operational taxonomic units (pOTUs) and identification of large phage scaffolds (n = 2567, ≥ 10 k) revealed a comprehensive human gut phageome with a substantial number of novel sequences encoding genes that were unrelated to those in known phages. Interestingly, we observed a significant increase in the number of gut phages in the T2D group and, in particular, identified 7 pOTUs specific to T2D. This finding was further validated in an independent dataset of 116 T2D and 109 control samples. Co-occurrence/exclusion analysis of the bacterial genera and pOTUs identified a complex core interaction between bacteria and phages in the human gut ecosystem, suggesting that the significant alterations of the gut phageome cannot be explained simply by co-variation with the altered bacterial hosts.

CONCLUSIONS

Alterations in the gut bacterial community have been linked to the chronic disease T2D, but the role of gut phages therein is not well understood. This is the first study to identify a T2D-specific gut phageome, indicating the existence of other mechanisms that might govern the gut phageome in T2D patients. These findings suggest the importance of the phageome in T2D risk, which warrants further investigation.

Imaging of Convective Drug Delivery in the Nervous System

Convection-enhanced delivery permits the direct homogeneous delivery of small- and large-molecular-weight putative therapeutics to the nervous system in a manner that bypasses the blood-nervous system barrier. The development of co-infused surrogate imaging tracers (for computed tomography and MRI) allows for the real-time, noninvasive monitoring of infusate distribution during convective delivery. Real-time image monitoring of convective distribution of therapeutic agents insures that targeted structures/nervous system regions are adequately perfused, enhances safety, informs efficacy (or lack thereof) of putative agents, and provides critical information regarding the properties of convection-enhanced delivery in normal and various pathologic tissue states.

Convection-Enhanced Delivery

Convection-enhanced delivery (CED) is a promising technique that generates a pressure gradient at the tip of an infusion catheter to deliver therapeutics directly through the interstitial spaces of the central nervous system. It addresses and offers solutions to many limitations of conventional techniques, allowing for delivery past the blood-brain barrier in a targeted and safe manner that can achieve therapeutic drug concentrations. CED is a broadly applicable technique that can be used to deliver a variety of therapeutic compounds for a diversity of diseases, including malignant gliomas, Parkinson's disease, and Alzheimer's disease. While a number of technological advances have been made since its development in the early 1990s, clinical trials with CED have been largely unsuccessful, and have illuminated a number of parameters that still need to be addressed for successful clinical application. This review addresses the physical principles behind CED, limitations in the technique, as well as means to overcome these limitations, clinical trials that have been performed, and future developments.

Bacteriophage-based tools: recent advances and novel applications

Bacteriophages (phages) are viruses that infect bacterial hosts, and since their discovery over a century ago they have been primarily exploited to control bacterial populations and to serve as tools in molecular biology. In this commentary, we highlight recent diverse advances in the field of phage research, going beyond bacterial control using whole phage, to areas including biocontrol using phage-derived enzybiotics, diagnostics, drug discovery, novel drug delivery systems and bionanotechnology.

Bacteriophages and phage-inspired nanocarriers for targeted delivery of therapeutic cargos

The main goal of drug delivery systems is to target therapeutic cargoes to desired cells and to ensure their efficient uptake. Recently a number of studies have focused on designing bio-inspired nanocarriers, such as bacteriophages, and synthetic carriers based on the bacteriophage structure. Bacteriophages are viruses that specifically recognize their bacterial hosts. They can replicate only inside their host cell and can act as natural gene carriers. Each type of phage has a particular shape, a different capacity for loading cargo, a specific production time, and their own mechanisms of supramolecular assembly, that have enabled them to act as tunable carriers. New phage-based technologies have led to the construction of different peptide libraries, and recognition abilities provided by novel targeting ligands. Phage hybridization with non-organic compounds introduces new properties to phages and could be a suitable strategy for construction of bio-inorganic carriers. In this review we try to cover the major phage species that have been used in drug and gene delivery systems, and the biological application of phages as novel targeting ligands and targeted therapeutics.

Phage Therapy in the Era of Synthetic Biology

For more than a century, bacteriophage (or phage) research has enabled some of the most important discoveries in biological sciences and has equipped scientists with many of the molecular biology tools that have advanced our understanding of replication, maintenance, and expression of genetic material. Phages have also been recognized and exploited as natural antimicrobial agents and nanovectors for gene therapy, but their potential as therapeutics has not been fully exploited in Western medicine because of challenges such as narrow host range, bacterial resistance, and unique pharmacokinetics. However, increasing concern related to the emergence of bacteria resistant to multiple antibiotics has heightened interest in phage therapy and the development of strategies to overcome hurdles associated with bacteriophage therapeutics. Recent progress in sequencing technologies, DNA manipulation, and synthetic biology allowed scientists to refactor the entire bacterial genome of Mycoplasma mycoides, thereby creating the first synthetic cell. These new strategies for engineering genomes may have the potential to accelerate the construction of designer phage genomes with superior therapeutic potential. Here, we discuss the use of phage as therapeutics, as well as how synthetic biology can create bacteriophage with desirable attributes.

Nanomedicine to Overcome Current Parkinson's Treatment Liabilities: A Systematic Review

Nanoparticles might be produced and manipulated to present a large spectrum of properties. The physicochemical features of the engineered nanomaterials confer to them different features, including the ability to cross the blood-brain barrier. The main objective of this review is to present the state-of-art research in nano manipulation concerning Parkinson's disease (PD). In the past few years, the association of drugs with nanoparticles solidly improved treatment outcomes. We systematically reviewed 28 studies, describing their potential contributions regarding the role of nanomedicine to increase the efficacy of known pharmacological strategies for PD treatment. Data from animal models resulted in the (i) improvement of pharmacological properties, (ii) more stable drug concentrations, (iii) longer half-live and (iv) attenuation of pharmacological adverse effects. As this approach is recent, with many of the described works being published less than 5 years ago, the expectancy is that this knowledge gives support to an improvement in the current clinical methods to the management of PD and other neurodegenerative diseases.

Systems-level thinking for nanoparticle-mediated therapeutic delivery to neurological diseases

Neurological diseases account for 13% of the global burden of disease. As a result, treating these diseases costs $750 billion a year. Nanotechnology, which consists of small (~1-100 nm) but highly tailorable platforms, can provide significant opportunities for improving therapeutic delivery to the brain. Nanoparticles can increase drug solubility, overcome the blood-brain and brain penetration barriers, and provide timed release of a drug at a site of interest. Many researchers have successfully used nanotechnology to overcome individual barriers to therapeutic delivery to the brain, yet no platform has translated into a standard of care for any neurological disease. The challenge in translating nanotechnology platforms into clinical use for patients with neurological disease necessitates a new approach to: (1) collect information from the fields associated with understanding and treating brain diseases and (2) apply that information using scalable technologies in a clinically-relevant way. This approach requires systems-level thinking to integrate an understanding of biological barriers to therapeutic intervention in the brain with the engineering of nanoparticle material properties to overcome those barriers. To demonstrate how a systems perspective can tackle the challenge of treating neurological diseases using nanotechnology, this review will first present physiological barriers to drug delivery in the brain and common neurological disease hallmarks that influence these barriers. We will then analyze the design of nanotechnology platforms in preclinical in vivo efficacy studies for treatment of neurological disease, and map concepts for the interaction of nanoparticle physicochemical properties and pathophysiological hallmarks in the brain. WIREs Nanomed Nanobiotechnol 2017, 9:e1422. doi: 10.1002/wnan.1422 For further resources related to this article, please visit the WIREs website.

Phage M13 for the treatment of Alzheimer and Parkinson disease

The studies of microbes have been instrumental in combatting infectious diseases, but they have also led to great insights into basic biological mechanism like DNA replication, transcription, and translation of mRNA. In particular, the studies of bacterial viruses, also called bacteriophage, have been quite useful to study specific cellular processes because of the ease to isolate their DNA, mRNA, and proteins. Here, I review the recent discovery of how properties of the filamentous phage M13 emerge as a novel approach to combat neurodegenerative diseases.

Evolving Drug Delivery Strategies to Overcome the Blood Brain Barrier

The blood-brain barrier (BBB) poses a unique challenge for drug delivery to the central nervous system (CNS). The BBB consists of a continuous layer of specialized endothelial cells linked together by tight junctions, pericytes, nonfenestrated basal lamina, and astrocytic foot processes. This complex barrier controls and limits the systemic delivery of therapeutics to the CNS. Several innovative strategies have been explored to enhance the transport of therapeutics across the BBB, each with individual advantages and disadvantages. Ongoing advances in delivery approaches that overcome the BBB are enabling more effective therapies for CNS diseases. In this review, we discuss: (1) the physiological properties of the BBB, (2) conventional strategies to enhance paracellular and transcellular transport through the BBB, (3) emerging concepts to overcome the BBB, and (4) alternative CNS drug delivery strategies that bypass the BBB entirely. Based on these exciting advances, we anticipate that in the near future, drug delivery research efforts will lead to more effective therapeutic interventions for diseases of the CNS.

Clinical analysis of spinal stereotactic radiosurgery in the treatment of neurogenic tumors

OBJECT

In this study the authors sought to evaluate clinical outcomes after using stereotactic radiosurgery (SRS) to treat benign and malignant spinal neurogenic tumors.

METHODS

The authors reviewed a total of 66 procedures of spinal SRS performed between 2001 and 2013 for 110 tumors in 58 patients with spinal neurogenic tumors, which included schwannomas, neurofibromas, and malignant peripheral nerve sheath tumors (MPNSTs). The clinical and radiological findings were evaluated in patients with benign neurogenic tumors. For the 4 patients with MPNSTs, the authors reported overall survival and results of additional immunohistochemical staining to predict the survival difference among the patients.

RESULTS

Of the 92 benign neurogenic tumors, 65 tumors that were serially followed up using MRI after SRS showed significant change in mean tumor volume, from a mean of 12.0 ± 2.6 cm3 pre-SRS to 10.8 ± 2.5 cm3 post-SRS (p = 0.027), over an average of 44 months. The local control rate of benign neurogenic tumors was 95.4%. The 34 patients who presented with clinical symptoms of pain showed a significant symptomatic improvement. The initial mean visual analog scale (VAS) score was 6.0 and decreased dramatically to 1.0 after SRS during an average follow-up period of 10.9 months (median of 8.1 months). Although the proportions of transient swelling and loss of intramural enhancement were significantly different among the groups, there was no statistically significant correlation between those 2 factors and local tumor control (p = 0.253 and 0.067, respectively; Fisher’s exact text). Cross-table analysis also indicated that there was no statistically significant relationship between groups with loss of intramural enhancement and transient swelling. The median survival of neurofibromatosis Type 1 (NF1)-related and sporadic MPNSTs was 1.13 and 5.8 years, respectively. Immunohistochemical results showed that S100 was expressed in a sporadic MPNST or neurofibroma, whereas topoisomerase-IIa was expressed in NF1-related MPNSTs.

CONCLUSIONS

SRS is an effective treatment modality for benign neurogenic tumors, while MPNSTs showed heterogeneity in their responses to SRS.

Beyond phage display: non-traditional applications of the filamentous bacteriophage as a vaccine carrier, therapeutic biologic, and bioconjugation scaffold

For the past 25 years, phage display technology has been an invaluable tool for studies of protein-protein interactions. However, the inherent biological, biochemical, and biophysical properties of filamentous bacteriophage, as well as the ease of its genetic manipulation, also make it an attractive platform outside the traditional phage display canon. This review will focus on the unique properties of the filamentous bacteriophage and highlight its diverse applications in current research. Particular emphases are placed on: (i) the advantages of the phage as a vaccine carrier, including its high immunogenicity, relative antigenic simplicity and ability to activate a range of immune responses, (ii) the phage's potential as a prophylactic and therapeutic agent for infectious and chronic diseases, (iii) the regularity of the virion major coat protein lattice, which enables a variety of bioconjugation and surface chemistry applications, particularly in nanomaterials, and (iv) the phage's large population sizes and fast generation times, which make it an excellent model system for directed protein evolution. Despite their ubiquity in the biosphere, metagenomics work is just beginning to explore the ecology of filamentous and non-filamentous phage, and their role in the evolution of bacterial populations. Thus, the filamentous phage represents a robust, inexpensive, and versatile microorganism whose bioengineering applications continue to expand in new directions, although its limitations in some spheres impose obstacles to its widespread adoption and use.

Investigation of intrathecal transport of NPT002, a prospective therapeutic based on phage M13, in nonhuman primates

Presently, there are no effective treatments for conditions characterized by protein misfolding, such as Alzheimer's, Parkinson's, and other diseases involving CNS. Since misfolding occurs at the earliest stage of the disease, it is likely to be involved in subsequent pathological developments. It has been found that NPT002 (bacteriophage M13) directly dissociates aggregates of misfolded proteins that form amyloid, including amyloid-β, tau and α-synuclein. For CNS applications, NPT002 requires delivery to the brain parenchyma, the target tissue. NPT002 is an elongated ~950 nm particle that cannot penetrate into the brain from the blood. Furthermore, phage particles, due to their size, cannot be effectively transported in vivo by diffusion. Considering the physiology of the leptomeningeal space, intrathecal administration appears to be a promising convection-driven avenue for NPT002 delivery. In this paper, we use positron emission tomography to investigate the transport of NPT002 in Macaca fascicularis. The data suggest that approximately 50 % of the administered dose can reach the cerebral leptomeningeal space after a single lumbar intrathecal injection. A biologically significant fraction of the phage then enters the brain, resulting in potentially therapeutic cortical and subcortical exposure.

Convection-enhanced delivery to the central nervous system

Convection-enhanced delivery (CED) is a bulk flow–driven process. Its properties permit direct, homogeneous, targeted perfusion of CNS regions with putative therapeutics while bypassing the blood-brain barrier. Development of surrogate imaging tracers that are co-infused during drug delivery now permit accurate, noninvasive real-time tracking of convective infusate flow in nervous system tissues. The potential advantages of CED in the CNS over other currently available drug delivery techniques, including systemic delivery, intrathecal and/or intraventricular distribution, and polymer implantation, have led to its application in research studies and clinical trials. The authors review the biophysical principles of convective flow and the technology, properties, and clinical applications of convective delivery in the CNS.

Exploitation of viral properties for intracellular delivery

Nanotechnology is an expanding area of study with potentially pivotal applications in a discipline as medicine where new biomedical active molecules or strategies are continuously developing. One of the principal drawbacks for the application of new therapies is the difficulty to cross membranes that represent the main physiological barrier in our body and in all living cells. Membranes are selectively permeable and allow the selective internalization of substances; generally, they form a highly impermeable barrier to most polar and charged molecules, and represent an obstacle for drug delivery, limiting absorption to specific routes and mechanisms. Viruses provide attracting suggestions for the development of targeted drug carriers as they have evolved naturally to deliver their genomes to host cells with high fidelity.

A detailed understanding of virus structure and their mechanisms of entry into mammalian cells will facilitate the development and analysis of virus‐based materials for medical applications. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.

Exploiting gut bacteriophages for human health

The human gut contains approximately 10(15) bacteriophages (the 'phageome'), probably the richest concentration of biological entities on earth. Mining and exploiting these potential 'agents of change' is an attractive prospect. For many years, phages have been used to treat bacterial infections in humans and more recently have been approved to reduce pathogens in the food chain. Phages have also been studied as drug or vaccine delivery vectors to help treat and prevent diseases such as cancer and chronic neurodegenerative conditions. Individual phageomes vary depending on age and health, thus providing a useful biomarker of human health as well as suggesting potential interventions targeted at the gut microbiota.

Influence of neuropathology on convection-enhanced delivery in the rat hippocampus

Local drug delivery techniques, such as convention-enhanced delivery (CED), are promising novel strategies for delivering therapeutic agents otherwise limited by systemic toxicity and blood-brain-barrier restrictions. CED uses positive pressure to deliver infusate homogeneously into interstitial space, but its distribution is dependent upon appropriate tissue targeting and underlying neuroarchitecture. To investigate effects of local tissue pathology and associated edema on infusate distribution, CED was applied to the hippocampi of rats that underwent electrically-induced, self-sustaining status epilepticus (SE), a prolonged seizure. Infusion occurred 24 hours post-SE, using a macromolecular tracer, the magnetic resonance (MR) contrast agent gadolinium chelated with diethylene triamine penta-acetic acid and covalently attached to albumin (Gd-albumin). High-resolution T1- and T2-relaxation-weighted MR images were acquired at 11.1 Tesla in vivo prior to infusion to generate baseline contrast enhancement images and visualize morphological changes, respectively. T1-weighted imaging was repeated post-infusion to visualize final contrast-agent distribution profiles. Histological analysis was performed following imaging to characterize injury. Infusions of Gd-albumin into injured hippocampi resulted in larger distribution volumes that correlated with increased injury severity, as measured by hyperintense regions seen in T2-weighted images and corresponding histological assessments of neuronal degeneration, myelin degradation, astrocytosis, and microglial activation. Edematous regions included the CA3 hippocampal subfield, ventral subiculum, piriform and entorhinal cortex, amygdalar nuclei, middle and laterodorsal/lateroposterior thalamic nuclei. This study demonstrates MR-visualized injury processes are reflective of cellular alterations that influence local distribution volume, and provides a quantitative basis for the planning of local therapeutic delivery strategies in pathological brain regions.

Convection-enhanced drug delivery to the brain: therapeutic potential and neuropathological considerations

Convection-enhanced delivery (CED) describes a direct method of drug delivery to the brain through intraparenchymal microcatheters. By establishing a pressure gradient at the tip of the infusion catheter in order to exploit bulk flow through the interstitial spaces of the brain, CED offers a number of advantages over conventional drug delivery methods-bypass of the blood-brain barrier, targeted distribution through large brain volumes and minimization of systemic side effects. Despite showing early promise, CED is yet to fulfill its potential as a mainstream strategy for the treatment of neurological disease. Substantial research effort has been dedicated to optimize the technology for CED and identify the parameters, which govern successful drug distribution. It seems likely that successful clinical translation of CED will depend on suitable catheter technology being used in combination with drugs with optimal physicochemical characteristics, and on neuropathological analysis in appropriate preclinical models. In this review, we consider the factors most likely to influence the success or failure of CED, and review its application to the treatment of high-grade glioma, Parkinson's disease (PD) and Alzheimer's disease (AD).

A multi-national report on methods for institutional credentialing for spine radiosurgery

BACKGROUND

Stereotactic body radiotherapy and radiosurgery are rapidly emerging treatment options for both malignant and benign spine tumors. Proper institutional credentialing by physicians and medical physicists as well as other personnel is important for the safe and effective adoption of spine radiosurgery. This article describes the methods for institutional credentialing for spine radiosurgery at seven highly experienced international institutions.

METHODS

All institutions (n = 7) are members of the Elekta Spine Radiosurgery Research Consortium and have a dedicated research and clinical focus on image-guided spine radiosurgery. A questionnaire consisting of 24 items covering various aspects of institutional credentialing for spine radiosurgery was completed by all seven institutions.

RESULTS

Close agreement was observed in most aspects of spine radiosurgery credentialing at each institution. A formal credentialing process was believed to be important for the implementation of a new spine radiosurgery program, for patient safety and clinical outcomes. One institution has a written policy specific for spine radiosurgery credentialing, but all have an undocumented credentialing system in place. All institutions rely upon an in-house proctoring system for the training of both physicians and medical physicists. Four institutions require physicians and medical physicists to attend corporate sponsored training. Two of these 4 institutions also require attendance at a non-corporate sponsored academic society radiosurgery course. Corporate as well as non-corporate sponsored training were believed to be complimentary and both important for training. In 5 centers, all cases must be reviewed at a multidisciplinary conference prior to radiosurgery treatment. At 3 centers, neurosurgeons are not required to be involved in all cases if there is no evidence for instability or spinal cord compression. Backup physicians and physicists are required at only 1 institution, but all institutions have more than one specialist trained to perform spine radiosurgery. All centers believed that credentialing should also be device specific, and all believed that professional societies should formulate guidelines for institutions on the requirements for spine radiosurgery credentialing. Finally, in 4 institutions radiation therapists were required to attend corporate-sponsored device specific training for credentialing, and in only 1 institution were radiation therapists required to also attend academic society training for credentialing.

CONCLUSIONS

This study represents the first multi-national report of the current practice of institutional credentialing for spine radiosurgery. Key methodologies for safe implementation and credentialing of spine radiosurgery have been identified. There is strong agreement among experienced centers that credentialing is an important component of the safe and effective implementation of a spine radiosurgery program.