A comparative study of different strategies for removal of endotoxins from bacteriophage preparations

Rapid Bench to Bedside Therapeutic Bacteriophage Production

It has been over 100 years since bacteriophages (phages) were used as a human therapeutic. Since then, phage production has dramatically evolved. Current phage preparations have fewer adverse effects due to their low bacterial toxin content. As a result, therapeutic phages have become a predominant class of new antimicrobials and are being widely used for compassionate treatment of multidrug-resistant (MDR) infections. We describe herein a protocol for the production and ultrapurification of phages. By this technique, it is possible for a lab experienced with the process to produce >109 plaque-forming units (PFU) per mL of Gram-negative phages that meet FDA endotoxins limits for intravenous infusions in as little as 48 hours. We provide illustrations of the process and tips on how to safely remove bacterial toxins from phage lysates. Although dependent on the phage strain, the approach described can rapidly generate and purify phages for a variety of applications.

Phage Therapy-Challenges, Opportunities and Future Prospects

The increasing drug resistance of bacteria to commonly used antibiotics creates the need to search for and develop alternative forms of treatment. Phage therapy fits this trend perfectly. Phages that selectively infect and kill bacteria are often the only life-saving therapeutic option. Full legalization of this treatment method could help solve the problem of multidrug-resistant infectious diseases on a global scale. The aim of this review is to present the prospects for the development of phage therapy, the ethical and legal aspects of this form of treatment given the current situation of such therapy, and the benefits of using phage products in persons for whom available therapeutic options have been exhausted or do not exist at all. In addition, the challenges faced by this form of therapy in the fight against bacterial infections are also described. More clinical studies are needed to expand knowledge about phages, their dosage, and a standardized delivery system. These activities are necessary to ensure that phage-based therapy does not take the form of an experiment but is a standard medical treatment. Bacterial viruses will probably not become a miracle cure-a panacea for infections-but they have a chance to find an important place in medicine.

Bacterial outer membrane vesicles bound to bacteriophages modulate neutrophil responses to bacterial infection

Pseudomonas aeruginosa is a major human pathogen, particularly effective at colonizing the airways of patients with cystic fibrosis. Bacteriophages are highly abundant at infection sites, but their impact on mammalian immunity remains unclear. We previously showed that Pf4, a temperate filamentous bacteriophage produced by P. aeruginosa, modifies the innate immune response to P. aeruginosa infections via TLR3 signaling, but the underlying mechanisms remained unclear. Notably, Pf4 is a single-stranded DNA and lysogenic phage, and its production does not typically result in lysis of its bacterial host. We identified previously that internalization of Pf4 by human or murine immune cells triggers maladaptive viral pattern recognition receptors and resulted in bacterial persistence based on the presence of phage RNA. We report now that Pf4 phage dampens inflammatory responses to bacterial endotoxin and that this is mediated in part via bacterial vesicles attached to phage particles. Outer membrane vesicles (OMVs) are produced by Gram-negative bacteria and play a key role in host pathogen interaction. Recently, evidence has emerged that OMVs differentially package small RNAs. In this study, we show that Pf4 are decorated with OMVs that remain affixed to Pf4 despite of purification steps. These phages are endocytosed by human cells and delivered to endosomal vesicles. We demonstrate that short RNAs within the OMVs form hairpin structures that trigger TLR3-dependent type I interferon production and antagonize production of antibacterial cytokines and chemokines. In particular, Pf4 phages inhibit CXCL5, preventing efficient neutrophil chemotaxis in response to endotoxin. Moreover, blocking IFNAR or TLR3 signaling abrogates the effect of Pf4 bound to OMVs on macrophage activation. In a murine acute pneumonia model, mice treated with Pf4 associated with OMVs show significantly less neutrophil infiltration in BAL fluid than mice treated with purified Pf4. These changes in macrophage phenotype are functionally relevant: conditioned media from cells exposed to Pf4 decorated with OMVs are significantly less effective at inducing neutrophil migration in vitro and in vivo. These results suggest that Pf4 phages alter innate immunity to bacterial endotoxin and OMVs, potentially dampening inflammation at sites of bacterial colonization or infection.

IRAK3 Knockout and Wildtype THP-1 Monocytes as Models for Endotoxin Detection Assays and Fusobacterium nucleatum Bacteriophage FNU1 Cytokine Induction

Microbial resistance to antibiotics poses a tremendous challenge. Bacteriophages may provide a useful alternative or adjunct to traditional antibiotics. To be used in therapy, bacteriophages need to be purified from endotoxins and tested for their effects on human immune cells. Interleukin-1 Receptor Associated Kinase-3 (IRAK3) is a negative regulator of inflammation and may play a role in the modulation of immune signalling upon bacteriophage exposure to immune cells. This study aimed to investigate the immune effects of crude and purified bacteriophage FNU1, a bacteriophage that targets the oral pathobiont Fusobacterium nucleatum, on wildtype and IRAK3 knockout THP-1 monocytic cell lines. The IRAK3 knockout cell line was also used to develop a novel endotoxin detection assay. Exposure to crude FNU1 increased the production of pro-inflammatory cytokines (Tumour necrosis factor - alpha (TNF-α) and Interleukin 6 (IL-6)) compared to purified FNU1 in wildtype and IRAK3 knockout THP-1 monocytes. In the IRAK3 knockout THP-1 cells, exposure to crude FNU1 induced a higher immune response than the wildtype monocytes, supporting the suggestion that the inhibitory protein IRAK3 regulates reactions to endotoxins and impurities in bacteriophage preparations. Finally, the novel endotoxin detection assay generated here provides a robust and accurate method for determining endotoxin concentrations.

Cell Free Bacteriophage Synthesis from Engineered Strains Improves Yield

Phage therapy to treat life-threatening drug-resistant infections has been hampered by technical challenges in phage production. Cell-free bacteriophage synthesis (CFBS) can overcome the limitations of standard phage production methods by manufacturing phage virions in vitro. CFBS mimics intracellular phage assembly using transcription/translation machinery (TXTL) harvested from bacterial lysates and combined with reagents to synthesize proteins encoded by a phage genomic DNA template. These systems may enable rapid phage production and engineering to accelerate phages from bench-to-bedside. TXTL harvested from wild type or commonly used bacterial strains was not optimized for bacteriophage production. Here, we demonstrate that TXTL from genetically modified E. coli BL21 can be used to enhance phage T7 yields in vitro by CFBS. Expression of 18 E. coli BL21 genes was manipulated by inducible CRISPR interference (CRISPRi) mediated by nuclease deficient Cas12a from F. novicida (dFnCas12a) to identify genes implicated in T7 propagation as positive or negative effectors. Genes shown to have a significant effect were overexpressed (positive effectors) or repressed (negative effectors) to modify the genetic background of TXTL harvested for CFBS. Phage T7 CFBS yields were improved by up to 10-fold in vitro through overexpression of translation initiation factor IF-3 (infC) and small RNAs OxyS and CyaR and by repression of RecC subunit exonuclease RecBCD. Continued improvement of CFBS will mitigate phage manufacturing bottlenecks and lower hurdles to widespread adoption of phage therapy.

Human Neutrophil Response to Pseudomonas Bacteriophage PAK_P1, a Therapeutic Candidate

The immune system offers several mechanisms of response to harmful microbes that invade the human body. As a first line of defense, neutrophils can remove pathogens by phagocytosis, inactivate them by the release of reactive oxygen species (ROS) or immobilize them by neutrophil extracellular traps (NETs). Although recent studies have shown that bacteriophages (phages) make up a large portion of human microbiomes and are currently being explored as antibacterial therapeutics, neutrophilic responses to phages are still elusive. Here, we show that exposure of isolated human resting neutrophils to a high concentration of the Pseudomonas phage PAK_P1 led to a 2-fold increase in interleukin-8 (IL-8) secretion. Importantly, phage exposure did not induce neutrophil apoptosis or necrosis and did not further affect activation marker expression, oxidative burst, and NETs formation. Similarly, inflammatory stimuli-activated neutrophil effector responses were unaffected by phage exposure. Our work suggests that phages are unlikely to inadvertently cause excessive neutrophil responses that could damage tissues and worsen disease. Because IL-8 functions as a chemoattractant, directing immune cells to sites of infection and inflammation, phage-stimulated IL-8 production may modulate some host immune responses.

Current Clinical Landscape and Global Potential of Bacteriophage Therapy

In response to the global spread of antimicrobial resistance, there is an increased demand for novel and innovative antimicrobials. Bacteriophages have been known for their potential clinical utility in lysing bacteria for almost a century. Social pressures and the concomitant introduction of antibiotics in the mid-1900s hindered the widespread adoption of these naturally occurring bactericides. Recently, however, phage therapy has re-emerged as a promising strategy for combatting antimicrobial resistance. A unique mechanism of action and cost-effective production promotes phages as an ideal solution for addressing antibiotic-resistant bacterial infections, particularly in lower- and middle-income countries. As the number of phage-related research labs worldwide continues to grow, it will be increasingly important to encourage the expansion of well-developed clinical trials, the standardization of the production and storage of phage cocktails, and the advancement of international collaboration. In this review, we discuss the history, benefits, and limitations of bacteriophage research and its current role in the setting of addressing antimicrobial resistance with a specific focus on active clinical trials and case reports of phage therapy administration.

Man vs Microbes - The Race of the Century

The complexity of the antimicrobial resistance (AMR) crisis and its global impact on healthcare invokes an urgent need to understand the underlying forces and to conceive and implement innovative solutions. Beyond focusing on a traditional pathogen-centric approach to antibiotic discovery yielding diminishing returns, future therapeutic interventions can expand to focus more comprehensively on host-pathogen interactions. In this manner, increasing the resiliency of our innate immune system or attenuating the virulence mechanisms of the pathogens can be explored to improve therapeutic outcomes. Key pathogen survival strategies such as tolerance, persistence, aggregation, and biofilm formation can be considered and interrupted to sensitize pathogens for more efficient immune clearance. Understanding the evolution and emergence of so-called 'super clones' that drive AMR spread with rapid clonotyping assays may guide more precise antibiotic regimens. Innovative alternatives to classical antibiotics such as bacteriophage therapy, novel engineered peptide antibiotics, ionophores, nanomedicines, and repurposing drugs from other domains of medicine to boost innate immunity are beginning to be successfully implemented to combat AMR. Policy changes supporting shorter durations of antibiotic treatment, greater antibiotic stewardship, and increased surveillance measures can enhance patient safety and enable implementation of the next generation of targeted prevention and control programmes at a global level.

Bacteriophage-Mediated Control of Biofilm: A Promising New Dawn for the Future

Biofilms are complex microbial microcolonies consisting of planktonic and dormant bacteria bound to a surface. The bacterial cells within the biofilm are embedded within the extracellular polymeric substance (EPS) consisting mainly of exopolysaccharides, secreted proteins, lipids, and extracellular DNA. This structural matrix poses a major challenge against common treatment options due to its extensive antibiotic-resistant properties. Because biofilms are so recalcitrant to antibiotics, they pose a unique challenge to patients in a nosocomial setting, mainly linked to lower respiratory, urinary tract, and surgical wound infections as well as the medical devices used during treatment. Another unique property of biofilm is its ability to adhere to both biological and man-made surfaces, allowing growth on human tissues and organs, hospital tools, and medical devices, etc. Based on prior understanding of bacteriophage structure, mechanisms, and its effects on bacteria eradication, leading research has been conducted on the effects of phages and its individual proteins on biofilm and its role in overall biofilm removal while also revealing the obstacles this form of treatment currently have. The expansion in the phage host-species range is one that urges for improvement and is the focus for future studies. This review aims to demonstrate the advantages and challenges of bacteriophage and its components on biofilm removal, as well as potential usage of phage cocktail, combination therapy, and genetically modified phages in a clinical setting.

Prospects of Inhaled Phage Therapy for Combatting Pulmonary Infections

With respiratory infections accounting for significant morbidity and mortality, the issue of antibiotic resistance has added to the gravity of the situation. Treatment of pulmonary infections (bacterial pneumonia, cystic fibrosis-associated bacterial infections, tuberculosis) is more challenging with the involvement of multi-drug resistant bacterial strains, which act as etiological agents. Furthermore, with the dearth of new antibiotics available and old antibiotics losing efficacy, it is prudent to switch to non-antibiotic approaches to fight this battle. Phage therapy represents one such approach that has proven effective against a range of bacterial pathogens including drug resistant strains. Inhaled phage therapy encompasses the use of stable phage preparations given via aerosol delivery. This therapy can be used as an adjunct treatment option in both prophylactic and therapeutic modes. In the present review, we first highlight the role and action of phages against pulmonary pathogens, followed by delineating the different methods of delivery of inhaled phage therapy with evidence of success. The review aims to focus on recent advances and developments in improving the final success and outcome of pulmonary phage therapy. It details the use of electrospray for targeted delivery, advances in nebulization techniques, individualized controlled inhalation with software control, and liposome-encapsulated nebulized phages to take pulmonary phage delivery to the next level. The review expands knowledge on the pulmonary delivery of phages and the advances that have been made for improved outcomes in the treatment of respiratory infections.

Past and Future of Phage Therapy and Phage-Derived Proteins in Patients with Bone and Joint Infection

Phage-derived therapies comprise phage therapy and the use of phage-derived proteins as anti-bacterial therapy. Bacteriophages are natural viruses that target specific bacteria. They were proposed to be used to treat bacterial infections in the 1920s, before the discovery and widespread over-commercialized use of antibiotics. Phage therapy was totally abandoned in Western countries, whereas it is still used in Poland, Georgia and Russia. We review here the history of phage therapy by focusing on bone and joint infection, and on the development of phage therapy in France in this indication. We discuss the rationale of its use in bacterial infection and show the feasibility of phage therapy in the 2020s, based on several patients with complex bone and joint infection who recently received phages as compassionate therapy. Although the status of phage therapy remains to be clarified by health care authorities, obtaining pharmaceutical-grade therapeutic phages (i.e., following good manufacturing practice guidelines or being “GMP-like”) targeting bacterial species of concern is essential. Moreover, multidisciplinary clinical expertise has to determine what could be the relevant indications to perform clinical trials. Finally “phage therapy 2.0” has to integrate the following steps: (i) follow the status of phage therapy, that is not settled and defined; (ii) develop in each country a close relationship with the national health care authority; (iii) develop industrial–academic partnerships; (iv) create academic reference centers; (v) identify relevant clinical indications; (vi) use GMP/GMP-like phages with guaranteed quality bioproduction; (vii) start as salvage therapy; (vii) combine with antibiotics and adequate surgery; and (viii) perform clinical trials, to finally (ix) demonstrate in which clinical settings phage therapy provides benefit. Phage-derived proteins such as peptidoglycan hydrolases, polysaccharide depolymerases or lysins are enzymes that also have anti-biofilm activity. In contrast to phages, their development has to follow the classical process of medicinal products. Phage therapy and phage-derived products also have a huge potential to treat biofilm-associated bacterial diseases, and this is of crucial importance in the worldwide spread of antimicrobial resistance.

Solvent Extraction of Klebsiella pneumoniae Bacteriophage Lysates with 1-Dodecanol Results in Endotoxin Reduction with Low Risk of Solvent Contamination

Antimicrobial resistance in pathogenic bacteria is increasing worldwide. One solution to this crisis is bacteriophage therapy, a treatment that harnesses naturally occurring bacterial viruses to invade and lyse antimicrobial resistant bacterial hosts. In Gram-negative hosts, a by-product of bacteriophage production is bacterial endotoxin, which can cause serious immune reactions in vivo. Purification methods using organic solvent extraction can remove endotoxin in bacteriophage lysates. In this study, we investigate a method for removal of endotoxin from 16 high-titer Klebsiella pneumoniae lysates by extraction with 1-dodecanol, 1-octanol, dodecane, or decane. In these experiments, treatment with either 1-dodecanol or 1-octanol resulted in removal of 10⁴-10⁵ endotoxin units/mL. Recovery of bacteriophage in lysates treated with dodecanol without dialysis was >90%, and residual dodecanol was low (10-1500 ppm). Overall these results suggest that organic solvent extraction using 1-dodecanol is effective at removing bacterial endotoxin, maintaining bacteriophage titer, and reducing solvent contamination in 16 K. pneumoniae bacteriophage lysates.

The Safety and Toxicity of Phage Therapy: A Review of Animal and Clinical Studies

Increasing rates of infection by antibiotic resistant bacteria have led to a resurgence of interest in bacteriophage (phage) therapy. Several phage therapy studies in animals and humans have been completed over the last two decades. We conducted a systematic review of safety and toxicity data associated with phage therapy in both animals and humans reported in English language publications from 2008-2021. Overall, 69 publications met our eligibility criteria including 20 animal studies, 35 clinical case reports or case series, and 14 clinical trials. After summarizing safety and toxicity data from these publications, we discuss potential approaches to optimize safety and toxicity monitoring with the therapeutic use of phage moving forward. In our systematic review of the literature, we found some adverse events associated with phage therapy, but serious events were extremely rare. Comprehensive and standardized reporting of potential toxicities associated with phage therapy has generally been lacking in the published literature. Structured safety and tolerability endpoints are necessary when phages are administered as anti-infective therapeutics.

Manufacturing of bacteriophages for therapeutic applications

Bacteriophages, or simply phages, are the most abundant biological entities on Earth. One of the most interesting characteristics of these viruses, which infect and use bacteria as their host organisms, is their high level of specificity. Since their discovery, phages became a tool for the comprehension of basic molecular biology and originated applications in a variety of areas such as agriculture, biotechnology, food safety, veterinary, pollution remediation and wastewater treatment. In particular, phages offer a solution to one of the major problems in public health nowadays, i.e. the emergence of multidrug-resistant bacteria. In these situations, the use of virulent phages as therapeutic agents offers an alternative to the classic, antibiotic-based strategies. The development of phage therapies should be accompanied by the improvement of phage biomanufacturing processes, both at laboratory and industrial scales. In this review, we first present some historical and general aspects related with the discovery, usage and biology of phages and provide a brief overview of the most relevant phage therapy applications. Then, we showcase current processes used for the production and purification of phages and future alternatives in development. On the production side, key factors such as the bacterial physiological state, the conditions of phage infection and the operation parameters are described alongside with the different operation modes, from batch to semi-continuous and continuous. Traditional purification methods used in the initial phage isolation steps are then described followed by the presentation of current state-of-the-art purification approaches. Continuous purification of phages is finally presented as a future biomanufacturing trend.

Self-assembled raccoon dog parvovirus VP2 protein confers immunity against RDPV disease in raccoon dogs: in vitro and in vivo studies

BACKGROUND

Raccoon dog parvovirus (RDPV) causes acute infectious diseases in raccoon dogs and may cause death in severe cases. The current treatment strategy relies on the extensive usage of classical inactivated vaccine which is marred by large doses, short immunization cycles and safety concerns.

METHODS

The present study aimed at optimization of RDPV VP2 gene, subcloning the gene into plasmid pET30a, and its subsequent transfer to Escherichia coli with trigger factor 16 for co-expression. The protein thus expressed was purified with ammonium sulfate precipitation, hydrophobic chromatography, and endotoxin extraction procedures. VLPs were examined by transmission electron microscopy, dynamic light scattering, and the efficacy of VLPs vaccine was tested in vivo.

RESULTS

Results indicated that RDPV VP2 protein could be expressed soluble. Transmission electron microscopy and dynamic light scattering results indicated that RDPV VP2 self-assembled into VLPs. Hemagglutination inhibition antibody titers elicited by Al(OH)3 adjuvanted RDPV VLPs were comparable with RDPV inactivated vaccines, and the viral loads in the blood of the struck raccoon dogs were greatly reduced. Hematoxylin and eosin and Immunohistochemical results indicated that RDPV VLPs vaccine could protect raccoon dogs against RDPV infections.

CONCLUSIONS

These results suggest that RDPV VLPs can become a potential vaccine candidate for RDPV therapy.

Pharmacokinetics and Time-Kill Study of Inhaled Antipseudomonal Bacteriophage Therapy in Mice

Inhaled bacteriophage (phage) therapy is a potential alternative to conventional antibiotic therapy to combat multidrug-resistant (MDR) Pseudomonas aeruginosa infections. However, pharmacokinetics (PK) and pharmacodynamics (PD) of phages are fundamentally different from antibiotics and the lack of understanding potentially limits optimal dosing. The aim of this study was to investigate the in vivo PK and PD profiles of antipseudomonal phage PEV31 delivered by pulmonary route in immune-suppressed mice. BALB/c mice were administered phage PEV31 at doses of 107 and 109 PFU by the intratracheal route. Mice (n = 4) were sacrificed at 0, 1, 2, 4, 8, and 24 h posttreatment and various tissues (lungs, kidney, spleen, and liver), bronchoalveolar lavage fluid, and blood were collected for phage quantification. In a separate study combining phage with bacteria, mice (n = 4) were treated with PEV31 (109 PFU) or phosphate-buffered saline (PBS) at 2 h postinoculation with MDR P. aeruginosa Infective PEV31 and bacteria were enumerated from the lungs. In the phage-only study, the PEV31 titer gradually decreased in the lungs over 24 h, with a half-life of approximately 8 h for both doses. In the presence of bacteria, in contrast, the PEV31 titer increased by almost 2-log10 in the lungs at 16 h. Furthermore, bacterial growth was suppressed in the PEV31-treated group, while the PBS-treated group showed exponential growth. Of the 10 colonies tested, four phage-resistant isolates were observed from the lung homogenates sampled at 24 h after phage treatment. These colonies had a different antibiogram to the parent bacteria. This study provides evidence that pulmonary delivery of phage PEV31 in mice can reduce the MDR bacterial burden.

Standardized bacteriophage purification for personalized phage therapy

The world is on the cusp of a post-antibiotic era, but researchers and medical doctors have found a way forward-by looking back at how infections were treated before the advent of antibiotics, namely using phage therapy. Although bacteriophages (phages) continue to lack drug approval in Western medicine, an increasing number of patients are being treated on an expanded-access emergency investigational new drug basis. To streamline the production of high-quality and clinically safe phage preparations, we developed a systematic procedure for medicinal phage isolation, liter-scale cultivation, concentration and purification. The 16- to 21-day procedure described in this protocol uses a combination of modified classic techniques, modern membrane filtration processes and no organic solvents to yield on average 23 mL of 10¹¹ plaque-forming units (PFUs) per milliliter for Pseudomonas, Klebsiella, and Serratia phages tested. Thus, a single production run can produce up to 64,000 treatment doses at 10⁹ PFUs, which would be sufficient for most expanded-access phage therapy cases and potentially for clinical phase I/II applications. The protocol focuses on removing endotoxins early by conducting multiple low-speed centrifugations, microfiltration, and cross-flow ultrafiltration, which reduced endotoxins by up to 10⁶-fold in phage preparations. Implementation of a standardized phage cultivation and purification across research laboratories participating in phage production for expanded-access phage therapy might be pivotal to reintroduce phage therapy to Western medicine.

Bacteriophage biocontrol to fight Listeria outbreaks in seafood

Listeria monocytogenes is a well-known pathogen responsible for the severe foodborne disease listeriosis. The control of L. monocytogenes occurrence in seafood products and seafood processing environments is an important challenge for the seafood industry and the public health sector. However, bacteriophage biocontrol shows great potential to be used as safety control measure in seafood. This review provides an update on Listeria-specific bacteriophages, focusing on their application as a safe and natural strategy to prevent L. monocytogenes contamination and growth in seafood products and seafood processing environments. Furthermore, the main properties required from bacteriophages intended to be used as biocontrol tools are summarized and emerging strategies to overcome the current limitations are considered. Also, major aspects relevant for bacteriophage production at industrial scale, their access to the market, as well as the current regulatory status of bacteriophage-based solutions for Listeria biocontrol are discussed.

Review article: bacteriophages in gastroenterology-from biology to clinical applications

BACKGROUND

The gut microbiota plays an important role in the pathogenesis of several gastrointestinal diseases. Its composition and function are shaped by host-microbiota and intra-microbiota interactions. Bacteriophages (phages) are viruses that target bacteria and have the potential to modulate bacterial communities.

AIMS

To summarise phage biology and the clinical applications of phages in gastroenterology METHODS: PubMed was searched to identify relevant studies.

RESULTS

Phages induce bacterial cell lysis, integration of viral DNA into the bacteria and/or coexistence in a stable equilibrium. Bacteria and phages have co-evolved and their dynamic interactions are yet to be fully understood. The increasing need to modulate microbial communities (e.g., gut microbiota, multidrug-resistant bacteria) has been a strong stimulus for research in phages as an antibacterial therapy. In gastroenterology, phage therapy has been mainly studied in infectious diseases such as cholera. However, it is currently being explored in several other circumstances such as treating Clostridioides difficile colitis, targeting adherent-invasive Escherichia coli in Crohn's disease or eradicating Fusobacterium nucleatum in colorectal cancer. Overall, phage therapy has a favourable and acceptable safety profile. Presently, trials with phage therapy are ongoing in Crohn's disease.

CONCLUSIONS

Phage therapy is a promising therapeutic tool against pathogenic bacteria in the fields of infectious diseases and gastroenterology. Randomised, placebo-controlled trials with phage therapy for gastroenterological diseases are ongoing.

Pharmacological limitations of phage therapy

Clinical trial results of phage treatment of bacterial infections show a low to moderate efficacy, and the variation in infection clearance between subjects within studies is often large. Phage therapy is complicated and introduces many additional components of variance as compared to antibiotic treatment. A large part of the variation is due to in vivo pharmacokinetics and pharmacodynamics being virtually unknown, but also to a lack of standardisation. This is a consequence of the great variation of phages, bacteria, and infections, which results in different experiments or trials being impossible to compare, and difficulties in estimating important parameter values in a quantitative and reproducible way. The limitations of phage therapy will have to be recognised and future research focussed on optimising infection clearance rates by e.g. selecting phages, bacteria, and target bacterial infections where the prospects of high efficacy can be anticipated, and by combining information from new mathematical modelling of in vivo pharmacokinetic and pharmacodynamic processes and quantitatively assessed experiments.

Robust Approaches for the Production of Active Ingredient and Drug Product for Human Phage Therapy

To be successful, academic and commercial efforts to reintroduce phage therapy must ensure that only safe and efficacious products are used to treat patients. This raises a number of manufacturing, formulation, and delivery challenges. Since phages are biologics, robust manufacturing processes will be crucial to avoid unwanted variability in each step of the process. The quality standards themselves need to be developed, as patients are currently being treated with phages produced under quality standards ranging from cGMP for clinical trials in EMA and FDA regulated environments to no standards at all in some last resort treatments. In this short review, we will systematically review the literature covering technical issues and approaches to increase robustness at every step of the production process: the identity of the phage and bacterial production strains, the fermentation process and purification, the formulation of the drug product, the quality controls and the documentation standards themselves. We conclude that it is possible to control cost at the same time, which is critical to re-introduce phage therapy to western medicine.

PolyBall: A new adsorbent for the efficient removal of endotoxin from biopharmaceuticals

The presence of endotoxin, also known as lipopolysaccharides (LPS), as a side product appears to be a major drawback for the production of certain biomolecules that are essential for research, pharmaceutical, and industrial applications. In the biotechnology industry, gram-negative bacteria (e.g., Escherichia coli) are widely used to produce recombinant products such as proteins, plasmid DNAs and vaccines. These products are contaminated with LPS, which may cause side effects when administered to animals or humans. Purification of LPS often suffers from product loss. For this reason, special attention must be paid when purifying proteins aiming a product as free as possible of LPS with high product recovery. Although there are a number of methods for removing LPS, the question about how LPS removal can be carried out in an efficient and economical way is still one of the most intriguing issues and has no satisfactory solution yet. In this work, polymeric poly-ε-caprolactone (PCL) nanoparticles (NPs) (dP = 780 ± 285 nm) were synthesized at a relatively low cost and demonstrated to possess sufficient binding sites for LPS adsorption and removal with ~100% protein recovery. The PCL NPs removed greater than 90% LPS from protein solutions suspended in water using only one milligram (mg) of NPs, which was equivalent to ~1.5 × 106 endotoxin units (EU) per mg of particle. The LPS removal efficacy increased to a higher level (~100%) when phosphate buffered saline (PBS containing 137 mM NaCl) was used as a protein suspending medium in place of water, reflecting positive effects of increasing ionic strength on LPS binding interactions and adsorption. The results further showed that the PCL NPs not only achieved 100% LPS removal but also ~100% protein recovery for a wide concentration range from 20-1000 μg/ml of protein solutions. The NPs were highly effective in different buffers and pHs. To scale up the process further, PCL NPs were incorporated into a supporting cellulose membrane which promoted LPS adsorption further up to ~100% just by running the LPS-containing water through the membrane under gravity. Its adsorption capacity was 2.8 × 106 mg of PCL NPs, approximately 2 -fold higher than that of NPs alone. This is the first demonstration of endotoxin separation with high protein recovery using polymer NPs and the NP-based portable filters, which provide strong adsorptive interactions for LPS removal from protein solutions. Additional features of these NPs and membranes are biocompatible (environment friendly) recyclable after repeated elution and adsorption with no significant changes in LPS removal efficiencies. The results indicate that PCL NPs are an effective LPS adsorbent in powder and membrane forms, which have great potential to be employed in large-scale applications.

Phage therapy for respiratory infections

A respiratory infection caused by antibiotic-resistant bacteria can be life-threatening. In recent years, there has been tremendous effort put towards therapeutic application of bacteriophages (phages) as an alternative or supplementary treatment option over conventional antibiotics. Phages are natural parasitic viruses of bacteria that can kill the bacterial host, including antibiotic-resistant bacteria. Inhaled phage therapy involves the development of stable phage formulations suitable for inhalation delivery followed by preclinical and clinical studies for assessment of efficacy, pharmacokinetics and safety. We presented an overview of recent advances in phage formulation for inhalation delivery and their efficacy in acute and chronic rodent respiratory infection models. We have reviewed and presented on the prospects of inhaled phage therapy as a complementary treatment option with current antibiotics and as a preventative means. Inhaled phage therapy has the potential to transform the prevention and treatment of bacterial respiratory infections, including those caused by antibiotic-resistant bacteria.

Regenerative Core-Shell Nanoparticles for Simultaneous Removal and Detection of Endotoxins

Detection and removal of lipopolysaccharides (LPS) from food and pharmaceutical preparations is important for their safe intake and administration to avoid septic shock. We have developed an abiotic system for reversible capture, removal, and detection of LPS in aqueous solutions. Our system comprises long C18 acyl chains tethered to Fe₃O₄/Au/Fe₃O₄ nanoflowers (NFs) that act as solid supports during the separation process. The reversible LPS binding is mediated by facile hydrophobic interactions between the C18 chains and the bioactive lipid A component present on the LPS molecule. Various parameters such as pH, solvent, sonication time, NF concentration, alkane chain length, and density are optimized to achieve a maximum LPS capture efficiency. The NFs can be reused at least three times by simply breaking the NF-LPS complexes in the presence of food-grade surfactants, making the entire process safe, efficient, and scalable. The regenerated particles also serve as colorimetric labels in dot blot bioassays for simple and rapid estimation of the LPS removed.

Intracellular drug delivery: Potential usefulness of engineered Shiga toxin subunit B for targeted cancer therapy

A treasure trove of intracellular cancer drug targets remains hidden behind cell membranes. However, engineered pathogen-derived toxins such as Shiga toxins can deliver small or macromolecular drugs to specific intracellular organelles. After binding to ganglioglobotriaosylceramide (Gb3, CD77), the non-toxic subunit B (StxB) of the Shiga-holotoxin is endocytosed and delivers its payload by a unique retrograde trafficking pathway via the endoplasmic reticulum to the cytosol. This review provides an overview of biomedical applications of StxB-based drug delivery systems in targeted cancer diagnosis and therapy. Biotechnological production of the Stx-material is discussed from the perspective of developing efficacious and safe therapeutics.

Pro- and anti-inflammatory responses of peripheral blood mononuclear cells induced by Staphylococcus aureus and Pseudomonas aeruginosa phages

The ability of bacteriophages to kill bacteria is well known, as is their potential use as alternatives to antibiotics. As such, bacteriophages reach high doses locally through infection of their bacterial host in the human body. In this study we assessed the gene expression profile of peripheral blood monocytes from six donors for twelve immunity-related genes (i.e. CD14, CXCL1, CXCL5, IL1A, IL1B, IL1RN, IL6, IL10, LYZ, SOCS3, TGFBI and TNFA) induced by Staphylococcus aureus phage ISP and four Pseudomonas aeruginosa phages (i.e. PNM, LUZ19, 14-1 and GE-vB_Pae-Kakheti25). The phages were able to induce clear and reproducible immune responses. Moreover, the overall immune response was very comparable for all five phages: down-regulation of LYZ and TGFBI, and up-regulation of CXCL1, CXCL5, IL1A, IL1B, IL1RN, IL6, SOCS3 and TNFA. The observed immune response was shown to be endotoxin-independent and predominantly anti-inflammatory. Addition of endotoxins to the highly purified phages did not cause an immune response comparable to the one induced by the (endotoxin containing) phage lysate. In addition, the use of an intermediate level of endotoxins tipped the immune response to a more anti-inflammatory response, i.e. up-regulation of IL1RN and a strongly reduced expression of CXCL1 and CXCL5.