Investigation of the anti-biofilm activities of inhibitors of the LasB protease and their application in the treatment of Pseudomonas aeruginosa infections in cystic fibrosis patients

Novel treatments are required to treat persistent bacterial infections in people with cystic fibrosis (CF). The most common pathogen in adults is Pseudomonas aeruginosa (PA) which, in chronic infections, grows on mucosal and epithelial surfaces, or in sputum, as structured communities called biofilms. Bacteria in biofilms are enclosed in a self-produced biopolymer matrix and display reduced susceptibility to antibiotic challenge, compared to their planktonic (free living) counterparts, due to a combination of poor antibiotic penetration and altered bacterial physiology, helping to promote the evolution and transmission of antimicrobial resistance (AMR). This leads to persistent colonisation of the lung by PA that is not cleared by conventional antibiotic treatment. Patients who are colonised with PA biofilms show a more rapid decline in lung function, faster decline in chest radiograph score, poor weight gain, increased hospitalisation rates and an increased need for antibiotic therapy with, ultimately, an increased mortality rate.

This PhD project will focus on an important effector of virulence and disease pathology in PA: the LasB elastase. The mature LasB protein is a 33 kDa metallo-protease and is the most significant of several PA toxins which degrade host immune proteins and cause tissue damage. In addition to its’s toxicity, several studies have also identified the importance of LasB in biofilm production, swarming motility and antibiotic tolerance in PA. Therefore, novel therapies targeted towards LasB could potentially decrease both the disease severity of the infection, as well as biofilm formation and persistence in the face of immune and antibiotic pressure.

The overall aim of this PhD will be to test the hypothesis that LasB inhibitors can reduce biofilm formation and virulence in CF sputum. In particular, nothing is known about how LasB inhibition may influence the interaction of PA-biofilms with host cells or affect their ability protect against host immunity factors in sputum, and this will be the focus for this PhD. The specific objectives will therefore be: i) To establish model systems that closely represents the host environment and allows for the study of PA biofilm-neutrophil interactions; ii) Measure LasB activity (and inhibition) directly within PA aggregates in the sputum model; and iii) to validate and extend our findings to ex-vivo expectorated sputum samples taken directly from CF patients. The proposed approach will be complementary to our drug discovery program by providing basic information on the role of LasB in PA-host immunity interactions, and will greatly benefit our efforts towards new therapies against PA-related disease progression in CF.

The successful applicant will become part of a vibrant and productive biofilm research team in Biological Sciences, University of Southampton. We are collaborating with Antabio, a France and UK-based private biopharmaceutical company who produce the inhibitor compounds. In addition to their university supervisors (Prof Jeremy Webb, Prof Saul Faust & Dr Rob Howlin), the student will also have an industrial supervisor (Dr Martin Everett, Chief Scientific Officer at Antabio) and get the exciting opportunity to spend a minimum of 3 months working within the Discovery Biology Group at Antabio in Labège, France during the PhD. The project will also take advantage of the excellent clinical research infrastructure we have in Southampton, enabled by the Southampton National Institute for Health Research Wellcome Trust Clinical Research Facility to provide clinically relevant translational research of benefit to patient health. The student will become part of an exciting interdisciplinary environment, taking part in the activities of the Institute for Life Sciences (IfLS) and the Network for AntiMicrobial Resistance and Infection Prevention (NAMRIP), gaining the opportunity to become part of and learn from a successful group of over 200 engineers, chemists, microbiologists, environmental scientists, medics, vets, experts in food, ethics and law, economists, geographers and health scientists aiming to drive forward research into the huge global health problem caused by AMR.