ePoster Presentation 49th Annual Scientific Meeting of the Australian and New Zealand Society for Immunology 2021

Cystic fibrosis airway microbes differentially activate a pathological neutrophil subset (#206)

Daniel R Laucirica 1 2 , Craig J Schofield 2 , Samantha A McLean 2 , Camilla Margaroli 3 4 , Patricia Agudelo-Romero 2 , Stephen M Stick 1 2 5 , Rabindra Tirouvanziam 6 7 , Anthony Kicic 1 2 5 8 , Luke W Garratt 2 , AREST CF 2 5 9 10
  1. Faculty of Health and Medical Sciences, University of Western Australia, Nedlands, WA, Australia
  2. Wal-yan Respiratory Research Centre, Telethon Kids Institute, Nedlands, WA, Australia
  3. Department of Medicine, Division of Pulmonary, Allergy & Critical Care Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
  4. Program in Protease and Matrix Biology, University of Alabama at Birmingham, Birmingham, AL, USA
  5. Dept of Respiratory and Sleep Medicine, Perth Children's Hospital, Nedlands, WA, Australia
  6. Dept of Pediatrics, Emory University, Atlanta, GA, USA
  7. Center for CF & Airways Disease Research, Children's Healthcare of Atlanta, Atlanta, GA, USA
  8. School of Population Health, Curtin University, Bentley, WA, Australia
  9. Murdoch Children's Research Institute, Melbourne, VIC, Australia
  10. Dept of Paediatrics, University of Melbourne, Melbourne, VIC, Australia

Background/Aim: A subset of neutrophils recruited into cystic fibrosis (CF) airways abundantly release tissue damaging neutrophil elastase (NE)1, causing lung damage2. Triggers of this subset are unknown, limiting intervention. Evidence points to respiratory viral-bacterial co-infections as a possible cause3, but this has not been directly studied. To explore this, we developed a laboratory model to characterise responses of airway tissue and neutrophils to virus and bacteria.

Methods: Differentiated primary airway epithelial cell cultures were challenged individually, or co-infected, with rhinovirus and bacteria representative of CF pathogens and airway microbes (Pseudomonas aeruginosa, Staphylococcus aureus, Neisseria lactamica, and Prevotella nigrescens). After infection, cultures were washed apically with medical saline to sample infection milieus. Washes were assessed for epithelial inflammatory signals, then applied to a published model of neutrophil transmigration to the airways1.

Results: Epithelial infection microenvironments were characterised by increased antiviral signals with exclusive rhinovirus infection, including MIG and IP-10, while P. aeruginosa uniquely increased pro-inflammatory cytokines IL-1α and β. Only neutrophils migrating into washes primed by P. aeruginosa and P. nigrescens had elevated CD63, a marker of granules that contain NE, and reduced CD16, a protein that allows neutrophils to engulf bacteria. These changes are reflective of neutrophils in CF airways1,2.

Conclusion: Our findings suggest both primary and secondary bacterial infections trigger the development of NE releasing neutrophils. Furthermore, different airway microbes variably prompted this neutrophil subset, suggesting CF airway dysbiosis may be a driver of neutrophil pathological activity. Further studies will characterise mechanisms of this process and identify potential therapeutic targets.

  1. 1) Forrest OA et al. Pathological conditioning of human neutrophils recruited to the airway milieu in cystic fibrosis. JLB. 2018;104:665-675.
  2. 2) Margaroli C and Garratt L.W. et al. Elastase exocytosis by airway neutrophils associates with early lung damage in children with cystic fibrosis. Am J Respir Crit Care Med. 2019. 199(7): 873-881.
  3. Grunwell J et al. Neutrophil Dysfunction in the Airways of Children with Acute Respiratory Failure Due to Lower Respiratory Tract Viral and Bacterial Coinfections. Sci Rep. 2019. 9(1): 2874.