Improvement in neutrophil recruitment and phagocytosis of resistant <em>Staphylococcus aureus</em> treated with antibiotic-chemoattractants — ASN Events

Improvement in neutrophil recruitment and phagocytosis of resistant Staphylococcus aureus treated with antibiotic-chemoattractants (#256)

Winfrey PY Hoo 1 2 , Jennifer AE Payne 1 2 3 , Julien Tailhades 1 2 4 , Jemma Gullick 2 , Rachel Cass 2 , Ee Shan Pang 2 , Meredith O'Keeffe 2 , Felix Ellett 5 , Alex J Fulcher 6 , Daniel Irima 5 , Anton Y Peleg 7 8 9 , Max J Cryle 1 2 4
  1. ARC Centre of Excellence for Innovations in Peptide and Protein Science, Monash University, Clayton, Victoria, Australia
  2. Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
  3. CSIRO Health and Biosecurity, Adelaide, South Australia, Australia
  4. EMBL Australia, Monash University, Clayton, Victoria, Australia
  5. BioMEMS Resource Center, Center for Engineering in Medicine and Surgical Services, Massachusetts General Hospital, Shriners Hospital for Children, and Harvard Medical School, Charlestown, Massachusett, USA
  6. Monash Micro Imaging, Monash University, Clayton, Victoria, Australia
  7. Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, Victoria, Australia
  8. Department of Infectious Diseases, The Alfred Hospital, Melbourne, Victoria, Australia
  9. Central Clinical School, Monash University, Melbourne, Victoria, Australia

Immunotherapy is a potential approach to modulate and enhance host immunity to combat antibiotic resistant pathogens such as S. aureus, instead of direct microbial killing as seen with traditional antibiotics. Our work has used this strategy to combat S. aureus through antibiotic-chemoattractants that consist of vancomycin conjugated to formyl peptides (fPeps). In these conjugates, vancomycin acts as a cell wall binding element to deliver fPep to S. aureus, while the attached fPep recruits neutrophils and enhances phagocytosis leading to clearance of S. aureus. With the growing burden of S. aureus resistance to last resort antibiotics, including daptomycin and vancomycin, we have now investigated the ability of these antibiotic-chemoattractants to combat these strains. Daptomycin resistance in S. aureus (DapR) results in strains that recruit less neutrophils, which could be potentially countered by our antibiotic-chemoattractants that enhance neutrophil recruitment. Meanwhile, vancomycin intermediate S. aureus (VISA) strains have thickened cell walls with increased vancomycin binding sites that leads to increased levels of vancomycin required for direct killing. However, our antibiotic-chemoattractants use vancomycin as a cell wall targeting element instead of direct antimicrobial activity. Thus, we predict an increase in binding of our antibiotic-chemoattractants to VISA and enhanced antimicrobial activity. Using fluorescently labelled antibiotic-chemoattractants, we determined the location of binding to clinical isolates by stimulated emission depletion (STED) microscopy and quantified binding by flow cytometry. Infection-on-a-chip assays allowed real time monitoring by confocal microscopy to determine neutrophil recruitment, phagocytosis of pHrodo-labelled isolates, and growth of GFP-expressing S. aureus clinical isolates. The application of antibiotic-chemoattractants resulted in improvements in neutrophil recruitment, phagocytosis, and reduced bacterial growth for DapR and VISA clinical isolates. The development of this immunotherapy method can be further explored by using different targeting elements or chemoattractant in the war against antimicrobial resistance.

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