Fighting Staphylococcus aureus infections with light and photoimmunoconjugates

Area of Science:

• Microbiology
• Immunology
• Photomedicine

Background:

• Multidrug-resistant Staphylococcus aureus (MRSA) infections pose a significant global health threat, with increasing community-acquired infections.
• Existing antibiotics face limitations due to rising drug resistance, necessitating novel therapeutic strategies.
• Antimicrobial photodynamic therapy (aPDT) presents a promising approach to combat resistant bacteria by utilizing light-activated compounds.

Purpose of the Study:

• To develop and evaluate a targeted aPDT strategy for eradicating MRSA infections.
• To investigate the efficacy of a novel immunoconjugate, 1D9-700DX, for MRSA targeting and photo-inactivation.
• To assess the potential of aPDT in overcoming host-related resistance mechanisms, such as plasma antioxidant properties.

Main Methods:

• Conjugation of a near-infrared photosensitizer (IRDye700DX) to a human monoclonal antibody (mAb) targeting the staphylococcal antigen IsaA, creating the immunoconjugate 1D9-700DX.
• Biochemical characterization of the immunoconjugate.
• Preclinical evaluation of targeted aPDT efficacy in vitro, in vivo, and in a human orthopedic implant infection model.
• Assessment of aPDT performance in the presence of human plasma, with and without potassium iodide as an aPDT-enhancing agent.

Main Results:

• The immunoconjugate 1D9-700DX specifically targets MRSA.
• Targeted aPDT with 1D9-700DX demonstrated high efficacy in eradicating MRSA in various preclinical models.
• The addition of potassium iodide enabled 1D9-700DX to overcome human plasma's antioxidant effects and achieve complete MRSA eradication.
• The therapy effectively killed MRSA upon red light illumination without causing collateral damage to human cells.

Conclusions:

• Targeted antimicrobial photodynamic therapy using the IsaA-targeting immunoconjugate 1D9-700DX is a highly effective strategy against MRSA.
• This novel aPDT approach offers a promising alternative to conventional antibiotics for treating drug-resistant staphylococcal infections.
• The developed therapy shows potential for clinical translation, particularly in challenging infection settings like orthopedic implants.