Adhesion to host cell membrane microdomains in cornea as an antimicrobial target to prevent corneal ulceration

Lead Research Organisation: University of Sheffield
Department Name: Infection Immunity & Cardiovasc Disease

Abstract

All over the world, there is a growing problem with antibiotics: there have been years of misuse by patients, doctors and even farmers seeking greater yields from livestock, with the result that microbes have learned to live with these once potent drugs. This problem is particularly acute in India, where access to professional healthcare is often limited and so ineffective antibiotics are bought and used by patients. For agricultural and domestic labourers, minor damage to the surface of the eye frequently results in bacterial and fungal infections; when not properly treated, this can lead to corneal ulceration and, eventually, to blindness. In a working-age person, the economic consequences can be disastrous for them and thier families. Given these issues, we are now looking for an alternative route to protect eyes against microbes. We have formed a partnership with a leading eye hospital, LV Prasad Eye Institute. LVPEI have developed a pyramidal structure so that research developed in the advanced research and surgery centre in Hyderabad can rapidly be disseminated throughout their organisation. They have a major drive to develop therapies that can benefit patients in rural villages.

The approach that we have taken came originally from a study of how our cells stick together to form tissues such as skin. There are structures on the surfaces of cells that resemble Velcro, highly organised patches of adhesive molecules that enable cells to cling tightly together. In some cases, these are long-lasting and static; in other cases they are short-lived and dynamic, allowing mobility, for instance when our white blood cells are travelling through tissues to get to the site of an infection. We discovered that some types of bacteria and yeasts can 'hijack' the dynamic sites, to allow them to stick to our tissues even when our natural defences try to dislodge them with tears and blinking. This is the starting point of an infection, when a colony of microorganisms attaches and starts to grow, often then penetrating deeper into tissues to cause serious disease. Even superficial infections can cause problems, leading to ulceration of the surface of the eye and eventually blindness if not properly treated.

Different types of microbes use different types of human molecules to cling to: targeting all of them would be very expensive. Our approach is not to target the molecular hooks themselves, but the material in which they are held to form the sticky patches. On Velcro, hooks are embedded in a baselayer of woven material but on our cells this is formed by a sort of molecular raft called a microdomain. We have discovered how to weaken one type of microdomain, in a way that is analagous to stretching Velcro, pulling the molecular hooks further apart and significantly lowering the stickiness of the patches on cells. By addressing only one type of microdomain, we have found that we do not affect the normal behaviour of our cells but we do make bacteria and fungi much easier to wash away.

Unlike antibiotics that directly target microbes, our treatment targets human cells and so should not lead to new forms of antibiotic resistance. If we can show that it is both safe and effective on the types of microbes that cause eye infections in India, we aim to produce a cheap and simple treatment for people who have injured their eyes, or who have early stage infections. This could be administered by patients or by a network of trained volunteers, easily and quickly. By helping to prevent infection, or giving more time to seek professional diagnosis, we hope to reduce the rate of a common cause of blindness in young people in India.

Technical Summary

Clinicians at the LVPrasad Eye Institute identified a vital need for effective first line therapy for patients in rural India with early stage eye infections. Without appropriate treatment, infections can quickly progress into irreversible corneal ulceration with loss of sight. LVPEI alone see 1200 cases of corneal infection per year: 30% will experience vision loss. In LMIC, many eye infections result in corneal ulceration and 10,000 patients per year lose eyes that might otherwise be saved
Inhibiting the adhesion of bacteria to the cornea is an innovative, low-risk strategy to prevent ulceration. Pathogens use a variety of means to adhere but all are dependent on interactions with molecules on the host cell surface. These are frequently located within highly organised microdomains, allowing control of the strength of adhesive interactions, allowing them to resist mechanical removal by mechanisms such as tear production and blinking. Human tetraspanin family proteins form microdomains that organise adhesion receptors such as integrins. Several species of pathogens use these microdomains for tight attachment to host cells. Treatment with tetraspanin-derived peptides weakens the attachment of a range of microbes and facilitates removal by natural defences. Importantly, an interaction occurs between the peptides and antibiotics that will allow the continued use of common antibiotics.
We aim to apply this treatment to microbial keratitis in India, exploring the effect of the peptides on common infections and the underlying mechanism, to promote the development of a safe and inexpensive topical treatment. The targeting of a broad range of pathogens allows treatment without diagnosis. This will benefit economically active people who damage their eyes during agricultural or domestic labour. Loss of sight from eye infection exists in other LMIC and our treatment will be appropriate for corneal infections in other areas lacking an integrated healthcare system.

Planned Impact

This proposal seeks to validate the use of a small peptide as a first-line defence in the prevention and treatment of early-stage infection. It would be applied immediately after corneal damage to prevent microbial adhesion and infection that can lead to corneal ulceration and loss of sight. The output will be validation of a new host-targeted anti-microbial strategy, providing a major step towards a simple, safe way of preventing acute corneal infections developing into corneal ulcerations in LMIC.

The activities we will undertake to foster the impacts identified in the impact summary can be grouped into five main categories: 1. Demonstrating the mechanism of a disruptor of membrane microdomains; 2. Taking a product to market in India. ; 3. Maximising patient take up of the treatment; 4. Dissemination beyond the project region; 5. Governance, monitoring and evaluation.

Publications

10 25 50
 
Description We have tested our anti-microbial peptides in a human cornea infection system, using corneas found to be unusable for human transplantation. This is the most realistic model for eye infections (microbial keratitis) and results should be strongly indicative of the likelihood of a successful repsonse in human patients. Our peptides achieved a highly significant decrease in corneal infection levels using a clnically relevant strain of Pseudomonas aeruginosa, a bacterium that causes rapid destruction of the surface of the eye in patients in India and which is resistant to some of the commonly used antibiotics.

We have data from an in vivo bacterial keratitis model, using an aggressive clinical isolate of P. aeruginosa obtained from a keratitis patient at LV Prasad Eye Institute, Hyderabad. Corneas are wounded and then pretreated with 1000nM CD9-derived peptide before inoculation. Peptide reduced the load of bacteria in wounded and infected eyes by >99.9%, a 3-log reduction after 24 hours. A 3-log reduction was once considered as the minimum level of efficacy for continued commercial research and development, although 1- to 2-log reductions are now considered suitable due to the limited pipeline of new antibiotics (doi.org/10.1093/jac/dky019). Infection by P. aeruginosa causes corneal blindness, as assessed by the opacity of the corneas in the two trials. Peptide treatment significantly reduced opacity, by 35% and 49%. This result suggests that bacterial infection is affected early enough to protect the corneal stroma from irreversible damage by bacterial proteases. Efficacy of stapled peptide has also been demonstrated in a 1 hour corneal cell line infection model and in a 24 hour human corneal explant infection model using the same clinical isolate. In both cases, a 1-log reduction in bacterial load was obtained with a single pretreatment with 400nM peptide. It is likely that the peptide is more effective in vivo because of mechanical (blinking) and immune mechanisms of clearance of bacteria.
Exploitation Route The peptides are undergoing further development that we expect will make them attractive to pharmaceutical compnies to licence for use in eye infections in LMIC.
Sectors Healthcare

Pharmaceuticals and Medical Biotechnology

 
Description Corneal biofilm models and anti-biofilm nanoparticles
Amount £69,573 (GBP)
Funding ID 01POC18029 
Organisation National Biofilms Innovation Centre 
Sector Private
Start 05/2019 
End 01/2020
 
Description NBIC proof of concept award with Destiny Pharma
Amount £64,045 (GBP)
Organisation University of Southampton 
Sector Academic/University
Country United Kingdom
Start 02/2020 
End 05/2020
 
Title Biofilm formation on corneal epithelial cells under flow conditions 
Description Use of Bioflux to measure Pseudomonal biofilm formation on corneal epithelial cells under flow conditions mimicking blinking 
Type Of Material Technology assay or reagent 
Year Produced 2020 
Provided To Others? No  
Impact N/A 
 
Title Porcine corneal explant cultures for antimicrobial drug development 
Description The corneum is a complex multi-layered tissue that is not easy to reproduce using cell lines. To avoid the use of living animals, we have developed an ex vivo model using the easily available by-product of the food industry. Infection with bacteria or fungi requires abrasion of the corneal epithelial layer, usually a requirement in vivo. Infection of the explants recapitulates infection in vivo, and appears similar to that seen in human corneal explants. 
Type Of Material Model of mechanisms or symptoms - in vitro 
Year Produced 2019 
Provided To Others? No  
Impact We will shortly be creating a video methods publication to allow other groups to use this method. 
 
Title PhD Thesis Additional Data: CARD-RGI Perfect & Strict Hits 
Description Supplementary data from the PhD thesis, 'The Development of in vitro Corneal Infection Models for Antimicrobial Drug Testing' (Lucy Urwin, 2022, Dept. IICD).Chapter 4 of the thesis describes characterisation of clinical isolates, including 39 Pseudomonas aeruginosa isolates from LV Prasad Eye Institute, Hyderabad, India. Genome sequencing was performed by Microbes NG (LVP3-6), Dr Luke Green, University of Sheffield (LVP3-6) and Dr Naveen Kumar, Christian Medical College, Vellore (all other isolates). FASTA files were analysed using the Comprehensive Antibiotic Resistance Database Resistance Gene Identifier (CARD-RGI). This file contains details of perfect and strict hits for antibiotic resistance genes, as identified by CARD-RGI.See README file for more details. 
Type Of Material Database/Collection of data 
Year Produced 2022 
Provided To Others? Yes  
URL https://figshare.shef.ac.uk/articles/dataset/CARD-RGI_Perfect_Strict_Hits/19169657
 
Description Bovine anti-bacterial antibodies in milk 
Organisation Shikhar Biotech
Country Nepal 
Sector Private 
PI Contribution We employed Shikar to test the milk of cows in the vicinity of Kathmandu, Nepal. Our contribution has been financial and advisory. Dr Meenu Chaudhary was recently recruited to the collaboration to provide ophthalmology advice, Nepali clinical isolates of pathogens and for future clinical trials.
Collaborator Contribution Shikhar have sourced the milk, developed ELISAs for the detection of anti-bacterial (S. aureus, P. aeruginosa, E. coli) IgA antibodies.
Impact None yet
Start Year 2018
 
Description Bovine anti-bacterial antibodies in milk 
Organisation Tribhuvan University of Nepal
Country Nepal 
Sector Academic/University 
PI Contribution We employed Shikar to test the milk of cows in the vicinity of Kathmandu, Nepal. Our contribution has been financial and advisory. Dr Meenu Chaudhary was recently recruited to the collaboration to provide ophthalmology advice, Nepali clinical isolates of pathogens and for future clinical trials.
Collaborator Contribution Shikhar have sourced the milk, developed ELISAs for the detection of anti-bacterial (S. aureus, P. aeruginosa, E. coli) IgA antibodies.
Impact None yet
Start Year 2018
 
Description Genetic analysis of keratitis pathogens in India 
Organisation Christian Medical College, Vellore
Country India 
Sector Academic/University 
PI Contribution Supply of ocular pathogens; characterisation of AMR and biofilm formation in these pathogens
Collaborator Contribution Genomics of microbial pathogens: sequencing and analysis.
Impact Publication: 10.3389/fmicb.2020.591679
Start Year 2019
 
Description Immunoglobulin purification and testing 
Organisation Shikhar Biotech
Country Nepal 
Sector Private 
PI Contribution Testing in vitro of milk immunoglobulins sourced, purified and characterised by Shikhar; production of antigens.
Collaborator Contribution Sourced local milk suppliers in Kathmandu and purified immunoglobulins. Characterised immunoglobulin content and purity and performed ELISA assays using antigens supplied by Sheffield.
Impact N/A
Start Year 2018
 
Description Testing new antimicrobials in skin and corneal infections 
Organisation JNCASR Jawaharlal Nehru Centre for Advanced Scientific Research
Country India 
Sector Academic/University 
PI Contribution Provision of 3D human skin and porcine cornea explant infection models
Collaborator Contribution Provision of new compounds
Impact https://pubs.acs.org/doi/10.1021/acsinfecdis.9b00334
Start Year 2019
 
Title ANTIMICROBIAL TARGET 
Description The present invention relates to a peptide for reducing pathogen adhesion. Specifically, a peptide comprising an amino acid sequence having at least 75% sequence identity to SEQ ID NO: 1. The peptide also comprises at least one staple between two or more residues equivalent to residues 3, 7, 10 or 14 of SEQ ID NO: 1. 
IP Reference WO2021175809 
Protection Patent application published
Year Protection Granted 2021
Licensed No
Impact It will form the basis of commercial development of out compound.
 
Description Supplementary data from the PhD thesis, 'The Development of in vitro Corneal Infection Models for Antimicrobial Drug Testing' (Lucy Urwin, 2022, Dept. IICD).Chapter 6 of the thesis describes use of the BioFlux microfluidic system for simulating bacterial keratitis under shear flow conditions. A combination of ImageJ and MATLAB code were used for batch processing time-lapse microscopy images; batch processing images using the Feature-Assisted Segmenter/Tracker (FAST) in MATLAB; and extracting data from FAST. The annotated code used to perform these functions is contained in this folder. See README file for further instructions. 
Type Of Technology Software 
Year Produced 2022 
Open Source License? Yes  
URL https://figshare.shef.ac.uk/articles/software/PhD_Thesis_Additional_Data_BioFlux_code/19213785
 
Description Interview for Express Healthcare magazine 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Online interview with Express Healthcare, one of the leading business news magazines for the Healthcare Industry. The magazine belongs to the Indian Express Group.
Year(s) Of Engagement Activity 2018
URL http://www.expressbpd.com/healthcare/knowledge/we-will-be-treating-the-patients-eyes-rather-than-the...
 
Description UK university collaborates with Indian scientists to combat eye infections 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Online interview as follow-up from press release
Year(s) Of Engagement Activity 2018
URL https://timesofindia.indiatimes.com/world/uk/uk-university-collaborates-with-indian-scientists-to-co...