Biology subjects

Echterhof, A.

Publications and source records attributed to Echterhof, A..

5 recordsLinked to original sources

bioRxiv2025

Whole-body Bacteriophage Distribution Characterized by a Physiologically based Pharmacokinetic Model

In 2019 there were over 2.8 million cases of antibiotic-resistant bacterial infection in the US with gram negative organisms having up to a 6% rate of mortality. Bacteriophage (phage) therapy holds great promise to treat such infections. However, the biologic features which influence the pharmacokinetics (PK) of phage have been difficult to characterize due to a lack of standardized protocols of phage purification, tissue assay, and labeling. Here we present robust methods for ultrapure phage preparation as well as non-destructive highly stable attachment of radio-iodide to phage using the well described Sulfo-SHPP linker. We purified and radiolabeled the phage strains, PAML-31-1, OMKO1, and Luz24 lytic to drug-resistant Pseudomonas aeruginosa for biodistribution assay in normal young adult CD-1 mice injected via penile vein. Groups of 5 mice were euthanized and tissues/organs removed for weighing and scintillation well counting of I-125 activity at 30 min, 1h, 2h, 4h, 8h, and 24h. A physiologically based PK (PBPK) model was then constructed focusing on compartments describing blood, lung, muscle, bone, liver, stomach, spleen, small intestines, large intestines, and kidney. Model permeability coefficient (PS) was estimated across all organs as being 0.0227. Tissue partition coefficients (KP) were estimated for high perfusion organs (lung and kidney) as 0.000138, GI organs (liver, spleen, and stomach) as 0.627, and all other organs as 0.220. Elimination was governed by MPS-mediated elimination (TMPS,deg) and active secretion at epithelial barriers (CLActive), which were estimated as 0.00301 h and 0.0145 L/h/kg, respectively. Monte Caro simulations showed that the rapid elimination phage in humans is expected, resulting in phage blood concentrations being lower than 102 PFU/mL (limit of quantification by plaque assay) by 12 hours. As such, multi-dose regimens and continuous infusion regimens were the only strategies that allowed continuously detectible phage concentrations. Evaluation of different dose levels showed that at a maximum dose of 1012 PFU, phage concentrations are expected to be approximately 107 PFU/g. Our physiologically based PK model of phage represents the first rigorous pre-clinical assessment of phage PK utilizing contemporary pharmacometric approaches amenable to both pre-clinical and clinical study design.

microbiology↗

bioRxiv2025

Bacteriophage purification using CIMmultus monolithic OH-column chromatography for therapeutic purposes

Bacteriophages are increasingly explored as antibacterial agents for therapeutic applications and pathogen biocontrol. Rigorous quality control and removal of microbial growth byproducts is essential for safety and compliance with regulatory standards for the use of phages; for phages isolated from Gram-negative bacterial lysates, this involves removal of endotoxin (lipopolysaccharide/LPS) and contaminating host proteins. Here, we describe the development of CIMmultus OH-Monolithic chromatography as a single-step purification process for five tailed anti-pseudomonal phages, including myoviral and siphoviral morphologies, as well as so-called "jumbo" phages, yielding therapeutically compliant samples suitable for human IV administration. Using preferential exclusion chromatography with a potassium phosphate gradient, we achieved near-complete removal of endotoxin (99.96-100.00% depletion) and protein impurities (95.8-99.7% depletion). We found that phage recovery post-purification was inversely associated with tail length and hydrodynamic diameter, with shorter-tailed and smaller phages demonstrating greater recovery. We conclude that single-step CIMmultus OH-monolithic chromatography is scalable, reproducible, and free from hazardous chemicals, supporting its integration into industrial phage purification processes.

microbiology↗

bioRxiv2024

Hydrogels for Local and Sustained Delivery of Bacteriophages to Treat Multidrug-Resistant Wound Infections

Lytic bacteriophages, viruses that lyse (kill) bacteria, hold great promise for treating infections, including wound infections caused by antimicrobial-resistant Pseudomonas aeruginosa. However, dosing and delivery strategies for phage therapy remain underdeveloped. In a mouse wound infection model, we investigated the impact of administration route, dose, and frequency on the efficacy of phage therapy. We find that topical but not systemic delivery is effective in this model. In vitro and in vivo data supported the use of high doses of phage. Repeated dosing achieves the highest eradication rates in vivo. Building on these insights, we developed "HydroPhage", a hyaluronan-based hydrogel system that uses dynamic covalent crosslinking to deliver high-titre phages over one week, a substantial improvement over existing burst-release systems. We conclude that hydrogel-based sustained phage delivery offers a practical, efficacious, and well-tolerated option for topical phage application.

bioengineering↗

bioRxiv2024

A Blueprint for Broadly Effective Bacteriophage Therapy Against Bacterial Infections

Bacteriophage therapy is a tantalizing therapeutic option for anti-microbial resistant bacterial infections but is currently limited to personalized therapy due to the narrow host range of individual phages. Theoretically, cocktails incorporating numerous phages targeting all possible bacterial receptor specificities could confer broad host range. Practically, however, extensive bacterial diversity and the complexity of phage-phage interactions precludes this approach. Here, using screening protocols for identifying "complementarity groups" of phages using non-redundant receptors, we generate effective, broad-range phage cocktails that prevent emergence of bacterial resistance. Further, phage complementarity groups have characteristic interactions with particular antibiotic classes, making it possible to predict phage-antibiotic as well as phage-phage interactions. Using this strategy, we generate three phage-antibiotic cocktails, each effective against >96% of 153 Pseudomonas aeruginosa clinical isolates, including when used in biofilm cultures and wound infections in vivo. We similarly develop effective Staphylococcus aureus phage-antibiotic cocktails and demonstrate the utility of combined cocktails against polymicrobial (mixed P. aeruginosa/S. aureus) cultures, highlighting the broad applicability of this approach. These studies establish a blueprint for effective, broad-spectrum phage therapy cocktails and enable off-the-shelf phage-based therapeutics for antimicrobial-resistant bacterial infections.

microbiology↗

bioRxiv2024

The contribution of neutrophils to bacteriophage clearance and pharmacokinetics in vivo

With the increasing prevalence of antimicrobial-resistant bacterial infections, there is great interest in using lytic bacteriophages (phages) to treat such infections. However, the factors that govern bacteriophage pharmacokinetics in vivo remain poorly understood. Here, we have examined the contribution of neutrophils, the most abundant phagocytes in the body, to the pharmacokinetics of intravenously administered bacteriophage in uninfected mice. A single dose of LPS-5, an antipseudomonal bacteriophage recently used in human clinical trials, was administered intravenously to both wild-type BALB/c and neutropenic ICR mice. Phage concentrations were assessed in peripheral blood and spleen at 0.5, 1, 2, 4, 8, 12, and 24 hours after administration by plaque assay and qPCR. We observed that the phage clearance is only minimally affected by neutropenia. Indeed, the half-life of phages in blood in BALB/c and ICR mice is 3.45 and 3.66 hours, respectively. These data suggest that neutrophil-mediated phagocytosis is not a major determinant of phage clearance. Conversely, we observed a substantial discrepancy in circulating phage levels over time when measured by qPCR versus plaque assay, suggesting that substantial functional inactivation of circulating phages occurs over time. These data indicate that circulating factors, but not neutrophils, inactivate intravenously administered phages.

pharmacology and toxicology↗