Development of a Photo-Antibody Therapeutic platform for the treatment of infected burns in children
Chief Investigator: Professor Allison Cowin
Funding Amount: $99,852
Recipient: University of South Australia
Burns are one of the most common injuries suffered by children and one of the top three causes of death under five years. Burn wound infection and sepsis are serious complications leading to over 60% of these deaths. With the increase in antimicrobial resistance, alternative approaches are urgently required to treat infections. We are developing an innovative new therapeutic approach for the treatment of infected burns. Our photo-antibody therapy (PAT) uses a photosensitizer to kill microbial cells upon excitation with a NIR laser. This new approach will significantly improve treatment of infected burns and reduce their impact in children.
Researchers: Prof Allison Cowin, Prof David Lancaster, Dr Zlatko Kopecki
Research Completed: 2021
Burns are one of the most common injuries that occur in young children. They can cause lifelong scarring and frequently contract as the child gets older therefore requiring extensive surgical interventions and placing a significant physical and psychological toll on patients. The emergence of multi-drug resistant bacteria is leading to increasing numbers of paediatric burn patients suffering burn wound infections which can lead to sepsis. Alarmingly, the infection risk is four times greater in Aboriginal and Torrens Strait Islander children who account for 10 percent of all burn admissions in Australia. The aim of this project was therefore to develop a safe, yet effective treatment for the management of infected burn wounds. To achieve this we have developed an antibody-based phototherapy technology platform which uses the specificity of antibodies to target photosensitisers to bacteria that infect burn wounds.
Photodynamic therapy has, to date, been mainly used as an adjuvant therapy for the treatment of cancerous and pre-cancerous skin lesions. Photodynamic therapy involves the activation of photosensitizing agents using light lasers of different wavelength resulting in the generation of reactive oxygen species which are critical for killing bacterial pathogens. By using antibodies against specific proteins present in the cell wall of Gram-positive and Gram-negative bacteria that are commonly found in burn wounds we hypothesized that we would be able to increase the specificity of the Photo-Antibody Therapy (PAT) for killing bacteria in burns. Our study involved two overarching aims:
Aim 1: Optimise the PAT platform for its effectiveness in killing bacteria prevalent in paediatric burns. The first step in developing the Photo-Antibody Therapy (PAT) platform involved screening a range of commonly used photosensitisers (Methylene Blue, Zinc (II) phthalocyanine and Rose Bengal) chosen for their unique properties and investigated different optimal conjugation protocols, including optimal ratio of antibody to photosensitisers for effective conjugation while still allowing exposed lysine binding sites to facilitate strong interactions with bacterial pathogens. We were able to demonstrate that Antibody : Photosensitiser ratio was critical in determining the optimal dose of antibody required. For example, while both Methylene Blue and Zinc (II) phthalocyanine showed no significant changes in fluorescence intensity in response to varying antibody amounts, we found that increasing the antibody ratio for Rose Bengal photosensitiser significantly increased fluorescence intensity (Fig 1a). Additionally, we conducted experiments to show that conjugated photosensitisers were still being able to have free lysine binding sites to allow interaction with bacteria leading to cytotoxic responses. An example of antibody-conjugated Methylene Blue photosensitiser being detected in a Western Blot is shown in Fig 1b. Following optimisation of the antibody conjugation protocols and confirmation of binding specificity, we showed that the conjugated photosensitisers were toxic to bacterial burn pathogens using an in-vitro biofilm assay. This allowed us to select the most promising conjugated photosensitiser with the maximum bactericidal activity and minimum cytotoxicity to skin cells for use in animal studies.
Aim 2. Conduct in-vivo studies using murine burn models to test safety and efficacy of PAT. We have also developed and optimised a scald burn wound infection models for both S. aureus and P. aerogenes in conjunction with IVIS Live Animal Imaging which will be used to test the PAT therapy in-vivo (Fig 1c). We have obtained animal ethics approval to test the lead conjugated photosensitiser and are ready to start these trials. Unfortunately delays with this aim were encountered due to purchasing of the laser equipment from the USA and optimisation of the model due to the COVID-19 pandemic that limited our access to the UniSA Centralized Animal Facility for trials and procedural training. However, we have also been able to recruit a PhD student who will continue these studies even though the CRF funding is completed and advance the PAT therapy for the treatment of burns.Therefore, we have been able to advance the PAT technology to the stage that we are ready to perform preclinical assessment of its effectiveness in murine burn models of infection. Upon completion of these studies we will have proof-of-concept data that will support this new technology for the treatment of paediatric burn injuries.
Key Outcomes: In Australia, childhood burns continue to account for a large number of hospital admissions, quarter of which need hospital readmission within the 28 days, placing a significant financial burden on the health system. This project has developed a novel photodynamic antibody therapy platform that specifically targets the bacteria found in infected burns. Future preclinical studies will determine if the use of the photodynamic antibody therapy can safely and effectively reduce the infections in burn wounds.
Paper in preparation:
Black N, Ravindram-Girija A, Lancaster D, Kopecki Z and Cowin AJ. “Photodynamic Therapy and it’s Role Against Infection and Microbial Resistance” manuscript prepared for submission to Australian Wound Journal Wound Practice and Research.
Black N, Ravindram-Girija A, Lancaster D, Kopecki Z and Cowin AJ. “Antimicrobial effects of conjugated Rose Bangal photosensitiser on in-vitro biofilm formation of burn wound pathogens” Manuscript in preparation for submission to Burns and Trauma.
Black N, Ravindram-Girija A, Lancaster D, Kopecki Z and Cowin AJ. “Development of a Photo-Antibody Therapy for the Treatment of Paediatric Burn Wound Infections” Clinical Health Sciences Symposium University of South Australia Sep 2020.
Future Outcomes: We are currently investigating the intellectual property landscape in the use of PAT platform to treat burn wound injuries.