Inhaled phage therapy: a promising and challenging approach to treat bacterial respiratory infections

Introduction: Bacterial respiratory tract infections (RTIs) are increasingly difficult to treat due to evolving antibiotic resistance. In this context, bacteriophages (or phages) are part of the foreseen alternatives or combination therapies. Delivering phages through the airways seems more relevant to accumulate these natural antibacterial viruses in proximity to their bacterial host, within the infectious site.

Areas covered: This review addresses the potential of phage therapy to treat RTIs and discusses preclinical and clinical results of phages administration in this context. Recent phage formulation and aerosolization attempts are also reviewed, raising technical challenges to achieve efficient pulmonary deposition via inhalation.

Expert opinion: Overall, the inhalation of phages as antibacterial treatment seems both clinically relevant and technically feasible. Several crucial points still need to be investigated, such as phage product pharmacokinetics and immunogenicity. Furthermore, given phage-specific features, appropriate regulatory and manufacturing guidelines will need to be defined. Finally, randomized controlled clinical trials should be carried out to establish phage therapy’s clinical positioning in the antimicrobial arsenal against RTIs.     

Nasal and pulmonary drug delivery systems

The respiratory route of administration has long been the medically desired drug delivery portal for the administration of topical anti-inflammatory drugs. These drugs are administered either to the lung, i.e., the lower respiratory system to treat asthma, or to the nasal cavity, i.e., the upper respiratory system to treat allergic rhinitis. This therapeutic focus dominates the drug delivery applications for the respiratory system. More recently, the respiratory system has provided a non-invasive method for the administration of biotherapeutics. And finally, formulation and device advancements have led to the consideration of the respiratory route for a number of other therapeutic applications where systemic delivery is desirable. All of these factors have resulted in the therapeutic patents that are discussed in this review.     

A double antigen bridging immunogenicity ELISA for the detection of antibodies to polyethylene glycol polymers

Introduction

Polyethylene glycol (PEG) polymers attached to biotherapeutic molecules enhance in vivo delivery and stability of these large molecular weight drugs. However, these polymers may by themselves be immunogenic and elicit antibodies that can reduce the efficacy of the drug and contribute to potential patient morbidity. A double antigen bridging ELISA immunogenicity assay for the detection of anti-drug antibodies (ADAs) specific to PEG polymers of various sizes has been developed.

Methods

Hapten-labeled conjugate of 40 kDa PEG polymer was synthesized and used in a double antigen bridging ELISA. The hapten-labeled PEG is incubated with the patient sample, then this mixture is added to a 96-well microplate precoated with 40 kDa PEG, allowing PEG-specific ADA to form a bridge complex with the PEG conjugate and the PEG coated on the microplate. After incubation, the reaction mixture is removed and replaced by horseradish peroxidase (HRP)-labeled anti-hapten antibody. After sufficient incubation, the plate is washed and substrate reagent is added. Enzyme color development, directly proportional to ADA, is stopped after 20 min with 2N sulfuric acid and the absorbance in each well is measured at 450/630 nm. Dose response, drug tolerance, matrix effects, reproducibility, specificity/free drug depletion experiments and screening cut-point determination of 350 naïve normal human sera were performed.

Results

Using an anti-PEG mouse monoclonal IgM as a positive control, a reproducible dose response curve was demonstrated for the PEG Immunogenicity ELISA. Pre-existing PEG-specific antibodies which were proven to be highly specific to the PEG polymer structure were found in 15 human serum samples in a total population of 350 naïve donors. The assay exhibited no significant matrix effects and was shown to be highly reproducible.

Discussion

A double antigen bridging immunogenicity assay for the detection of antibodies to PEG in the typical polymer size ranges used in biotherapeutics has been successfully developed in ELISA format. The antibodies detected in positive samples displayed a diverse spectrum of specificities for different PEG polymer lengths and linking functional groups. The discovery of 15 confirmed positive samples among 350 naïve patient samples calls into focus the need for testing PEG-specific immunogenicity of PEGylated biotherapeutics.     

Effect of biotherapeutics on antitoxin IgG in experimentally induced Clostridium difficile infection

Purpose: Recurrent diarrhoea after successful treatment of primary Clostridium difficile associated disease (CDAD) occurs due to bowel flora alterations and failure to mount an effective antibody response. Apart from antibiotics, risk factors include immunosuppressive and acid-suppressive drug administration. Biotherapeutics such as probiotic and epidermal growth factor (EGF) may offer potential effective therapy for CDAD. Materials and Methods: The effect of biotherapeutics in mounting an antibody response against C. difficile toxins was studied in BALB/c mice challenged with C. difficile after pre-treatment with ampicillin, lansoprazole or cyclosporin. Sera from sacrificed animals were estimated for antitoxin IgG by enzyme linked immunosorbent assay. Results: Antitoxin IgG was significantly higher (P<0.05) in C. difficile challenged groups compared to unchallenged controls, but insignificant (P>0.05) in animals in which C. difficile was given after pre-treatment with cyclosporin compared to those without any pre-treatment, or pre-treatment with antibiotic or lansoprazole. In inter-subgroup comparisons also significant anomaly in production of antitoxin IgG was found. The antitoxin IgG levels were raised in animals administered C. difficile after pre-treatment with ampicillin, but lower in animals administered cyclosporin. High levels of antitoxin IgG were also found in the serum samples of animals receiving lansoprazole and C. difficile. Conclusions: Probiotics showed their beneficial effect by boosting the immune response as seen by production of antitoxin IgG. Oral administration of EGF did not affect the immune response to C. difficile toxins as significant increase was not observed in the serum antitoxin IgG levels in any of the groups investigated.     

A Randomized Trial of Yogurt for Prevention of Antibiotic-Associated Diarrhea

Antibiotic-associated diarrhea (AAD) is the most common adverse effect of antibiotic therapy. Our aim was to determine the effectiveness of a dietary supplement of yogurt for prevention of AAD. Two hundred two hospitalized patients receiving oral or intravenous antibiotics were randomized to receive or not receive a dietary yogurt supplement, consisting of 227 grams of commercial yogurt, and followed for 8 days. Mean age of the study group was 70 years and 43% were male. Compliance and 8-day follow-up were 85% and 91%, respectively. Patients receiving yogurt reported less frequent diarrhea (12% vs 24%; P = 0.04), and significantly less total diarrheal days (23 vs 60). The cumulative proportions of patients without diarrhea were significantly different (P = 0.02) between patients receiving and not receiving yogurt. For conclusion, dietary supplementation with yogurt is a simple, effective, and safe treatment that decreases the incidence and duration of AAD.     

Varying polymer architecture to deliver drugs

Variable architecture polymers are of considerable interest for the delivery of therapeutic biopolymers, such as DNA and proteins, to their site of action. Polymers that can respond with a change in conformation to biologically relevant stimuli, such as temperature and pH, are being carefully designed to take advantage of the change in environmental conditions the polymer-drug conjugate encounters upon progression from larger-scale systems in the body to subcellular compartments. Viruses respond to changes in the cellular environment to gain access to their desired region of cells, and much can be learned from the mechanisms they employ in this effort. However, despite the efficiency of therapeutic biopolymers, undesirable immune and inflammatory responses may result from their repeated administration, so synthetic polymers are an attractive alternative. This mini-review examines a range of recently developed variable architecture polymers, mainly focusing on polymers responsive to temperature and pH, covering both synthetic copolymers and derivatives of naturally occurring polymers for advanced drug delivery applications. The polymers discussed in the article have some of the properties that are most important for polymer drug delivery vehicles to be effective, such as biodegradability, specificity, and biocompatibility.     

Superparamagnetic iron oxide nanoparticle-based delivery systems for biotherapeutics

Introduction: Superparamagnetic iron oxide nanoparticle (SPION)-based carrier systems have many advantages over other nanoparticle-based systems. They are biocompatible, biodegradable, facilely tunable and superparamagnetic and thus controllable by an external magnetic field. These attributes enable their broad biomedical applications. In particular, magnetically driven carriers are drawing considerable interest as an emerging therapeutic delivery system because of their superior delivery efficiency.

Areas covered: This article reviews the recent advances in use of SPION-based carrier systems to improve the delivery efficiency and target specificity of biotherapeutics. The authors examine various formulations of SPION-based delivery systems, including SPION micelles, clusters, hydrogels, liposomes and micro/nanospheres, as well as their specific applications in delivery of biotherapeutics.

Expert opinion: Recently, biotherapeutics including therapeutic cells, proteins and genes have been studied as alternative treatments to various diseases. Despite the advantages of high target specificity and low adverse effects, clinical translation of biotherapeutics has been hindered by the poor stability and low delivery efficiency compared with chemical drugs. Accordingly, biotherapeutic delivery systems that can overcome these limitations are actively pursued. SPION-based materials can be ideal candidates for developing such delivery systems because of their excellent biocompatibility and superparamagnetism that enables long-term accumulation/retention at target sites by utilization of a suitable magnet. In addition, synthesis technologies for production of finely tuned, homogeneous SPIONs have been well developed, which may promise their rapid clinical translation.     

Live bacterial cells as orally delivered therapeutics

Despite the swift escalation in research regarding the use of live bacterial cells for therapeutic purposes, the prophylactic and curative use of probiotic microorganisms still remains a wide and controversial field. In addition, the acknowledgement that live bacterial cells can be genetically engineered to synthesise products that have therapeutic potential has generated substantial interest among clinicians and health professionals. Clinical trials have increasingly provided an insightful scientific derivation for the use of live bacterial cells in medicinal practice in diseases such as diarrhoea, cancer, Crohn’s disease, enhancement of the host’s immune response, and numerous other diseases. A key constraint in the use of live bacterial cells, however, is the complexity of delivering them to the correct target sites. Oral delivery of free live cells, lyophilised cells and immobilised cells has been attempted, but with restricted success, chiefly because bacterial cells are unable to survive passage through the gastrointestinal tract in sufficient dosage. On many occasions, when given orally, these cells have been found to provoke immunogenic responses that are undesirable. Recent studies show that these problems can be overcome by delivering live bacterial cells using artificial cell microcapsules. This review abridges recent developments in the therapeutic use of live bacterial cells, addresses the potential and restrictions for their application in therapy, and provides insights into the future course of this emerging therapy.     

活菌药物在肿瘤免疫治疗中的应用进展和未来展望

肠道微生物是人体重要的器官，在人类健康和疾病中发挥重要作用。很多疾病被证实与肠道微生物的组成和功能 改变相关。肿瘤免疫治疗作为一种新兴的肿瘤治疗手段，具有特异性强、疗效显著等特点，免疫检查点抑制剂是目前应用较为 广泛的方法之一。免疫检测点抑制剂的疗效与肠道菌群有直接联系。本文对近年来肿瘤免疫治疗相关肠道微生物的研究进 展进行总结，阐述了肠道菌群在肿瘤治疗中的功能和作用机制，如通过代谢产物或表面蛋白直接或间接抑制肿瘤生长或诱导 肿瘤细胞凋亡，调节免疫系统特别是肿瘤微环境发挥抗肿瘤功能等。随着HUMAnN2流程、DADA2流程、metaWRAP等生物信 息工具和统计方法在肠道菌群方面的应用，肠道菌群在肿瘤免疫方面的研究得到进一步发展。目前，各研究机构和生物制药 公司均已在肠道微生物领域进行规划，并已注册多项临床试验。本文还就免疫治疗相关肠道微生物的发现方法以及用于肿瘤 免疫治疗的活菌药物开发进展情况进行介绍，并在此基础上探讨了目前的缺陷和未来的发展趋势。