Formulation, stabilisation and encapsulation of bacteriophage for phage therapy

Against a backdrop of global antibiotic resistance and increasing awareness of the importance of the human microbiota, there has been resurgent interest in the potential use of bacteriophages for therapeutic purposes, known as phage therapy. A number of phage therapy phase I and II clinical trials have concluded, and shown phages don’t present significant adverse safety concerns. These clinical trials used simple phage suspensions without any formulation and phage stability was of secondary concern. Phages have a limited stability in solution, and undergo a significant drop in phage titre during processing and storage which is unacceptable if phages are to become regulated pharmaceuticals, where stable dosage and well defined pharmacokinetics and pharmacodynamics are de rigueur. Animal studies have shown that the efficacy of phage therapy outcomes depend on the phage concentration (i.e. the dose) delivered at the site of infection, and their ability to target and kill bacteria, arresting bacterial growth and clearing the infection. In addition, in vitro and animal studies have shown the importance of using phage cocktails rather than single phage preparations to achieve better therapy outcomes. The in vivo reduction of phage concentration due to interactions with host antibodies or other clearance mechanisms may necessitate repeated dosing of phages, or sustained release approaches. Modelling of phage-bacterium population dynamics reinforces these points. Surprisingly little attention has been devoted to the effect of formulation on phage therapy outcomes, given the need for phage cocktails, where each phage within a cocktail may require significantly different formulation to retain a high enough infective dose. This review firstly looks at the clinical needs and challenges (informed through a review of key animal studies evaluating phage therapy) associated with treatment of acute and chronic infections and the drivers for phage encapsulation. An important driver for formulation and encapsulation is shelf life and storage of phage to ensure reproducible dosages. Other drivers include formulation of phage for encapsulation in micro- and nanoparticles for effective delivery, encapsulation in stimuli responsive systems for triggered controlled or sustained release at the targeted site of infection. Encapsulation of phage (e.g. in liposomes) may also be used to increase the circulation time of phage for treating systemic infections, for prophylactic treatment or to treat intracellular infections. We then proceed to document approaches used in the published literature on the formulation and stabilisation of phage for storage and encapsulation of bacteriophage in micro- and nanostructured materials using freeze drying (lyophilization), spray drying, in emulsions e.g. ointments, polymeric microparticles, nanoparticles and liposomes. As phage therapy moves forward towards Phase III clinical trials, the review concludes by looking at promising new approaches for micro- and nanoencapsulation of phages and how these may address gaps in the field

A Low Gastric pH Mouse Model to Evaluate Live Attenuated Bacterial Vaccines

The low pH of the stomach serves as a barrier to ingested microbes and must be overcome or bypassed when delivering live bacteria for vaccine or probiotic applications. Typically, the impact of stomach acidity on bacterial survival is evaluated in vitro, as there are no small animal models to evaluate these effects in vivo. To better understand the effect of this low pH barrier to live attenuated Salmonella vaccines, which are often very sensitive to low pH, we investigated the value of the histamine mouse model for this application. A low pH gastric compartment was transiently induced in mice by the injection of histamine. This resulted in a gastric compartment of approximately pH 1.5 that was capable of distinguishing between acid-sensitive and acid-resistant microbes. Survival of enteric microbes during gastric transit in this model directly correlated with their in vitro acid resistance. Because many Salmonella enterica serotype Typhi vaccine strains are sensitive to acid, we have been investigating systems to enhance the acid resistance of these bacteria. Using the histamine mouse model, we demonstrate that the in vivo survival of S. Typhi vaccine strains increased approximately 10-fold when they carried a sugar-inducible arginine decarboxylase system. We conclude that this model will be a useful for evaluating live bacterial preparations prior to clinical trials

Diabetes and Cardiovascular Care Among People with Severe Mental Illness: A Literature Review

Close to 19 million US adults have severe mental illnesses (SMI), and they die, on average, 25 years earlier than the general population, most often from cardiovascular disease (CVD). Many of the antipsychotic medications used to treat SMI contribute to CVD risk by increasing risk for obesity, type 2 diabetes, dyslipidemia, and hypertension. Based on compelling evidence, the American Diabetes Association and the American Psychiatric Association developed guidelines for metabolic screening and monitoring during use of these medications. In this manuscript, we have reviewed the evidence on diabetes and other CVD risk screening, prevalence, and management among populations with SMI. We also review differences in screening among subpopulations with SMI (e.g., racial/ethnic minorities, women, and children). We found that despite national guidelines for screening for diabetes and other cardiovascular risk factors, up to 70 % of people taking antipsychotics remain unscreened and untreated. Based on estimates that 20 % of the 19 million US adults with SMI have diabetes and 70 % of them are not screened; it is likely that over 2 million Americans with SMI have unidentified diabetes. Given that undiagnosed diabetes costs over $4,000 per person, this failure to identify diabetes among people with SMI represents a missed opportunity to prevent morbidity and translates to over$8 billion in annual preventable costs to our healthcare system. Given the high burden of disease and significant evidence of suboptimal medical care received by people with SMI, we propose several clinical and policy recommendations to improve diabetes and other CVD risk screening and care for this highly vulnerable population. These recommendations include reducing antipsychotic medication dose or switching antipsychotic medications, enhancing smoking cessation efforts, sharing electronic health records between physical and mental health care systems, and promoting integration of care