Pneumologie 2014; 68 - A19
DOI: 10.1055/s-0034-1376788

The effector protein ExoY secreted by Pseudomonas aeruginosa augments the inflammatory reaction in the respiratory tract of mice

A Munder 1, C Hartwig 1, B Schirmer 1, T Stelzer 1, B Tümmler 1, 3, R Seifert 1
  • 1Clinic for Pediatric Pneumology, Allergology and Neonatology, Hannover Medical School, Hannover
  • 2Institute of Pharmacology, Hannover Medical School, Hannover
  • 3Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Hannover, Member of the German Center for Lung Research (DZL)

Infection with the gram-negative opportunistic pathogen P. aeruginosa causes serious pulmonary, urogenital and systemic inflammation in immunodeficient patients. Most prominently, P. aeruginosa is the key organism responsible for pneumonia in cystic fibrosis patients, defining the course of the disease as well as its prognosis. P. aeruginosa produces a wide variety of effector proteins and injects them into host cells via the type III secretion system [1]. One of the effectors, injected by this needle-like structure is ExoY, which can be found in 90% of clinical isolates from P. aeruginosa. Despite of the highly frequent ExoY occurrence, its function is still unknown. While previous publications described ExoY to be apathogenic, our recent in vivo studies demonstrated a distinct role of ExoY as a pathogenic factor of P. aeruginosa.

In our murine infection model we infected B6 mice intratracheally with 1 × 106 – 8 colony forming units (cfu) of two P. aeruginosa strains, the first expressing a functional ExoY, the second the catalytically inactive ExoY mutant K81 M [2]. Mice were sacrificed 0 – 48h after infection and bacterial infection was characterized by analyzing the migration of neutrophils into the lung and inflammatory cytokines in the respiratory tract.

Infection doses of 107 cfu/mouse lead to ExoY-dependent, severe pathological changes in lung tissue and to increased mortality. Even more distinct effects were seen at concentrations of 108 cfu/mouse. Within 4 to 8 hours severe signs of infection and lung inflammation were observed. Lethality occured 24 – 48 hours after infection. Inflammatory lung reaction was characterized by interstitial edema, hemorrhagic infiltration and necrotic/apoptotic areas in the tissue. Secretion of proinflammatory factors such as IL-6, IL-1, MCP-1 and KC was significantly increased in the ExoY infected groups.

References:

[1] Hauser AR. The type III secretion system of Pseudomonas aeruginosa: infection by injection. Nat Rev Microbiol 2009 7: 654 – 665

[2] Yahr TL, Vallis AJ, Hancock MK, Barbieri JT and Frank DW. ExoY, an adenylate cyclase secreted by the Pseudomonas aeruginosa type III system. Proc. Natl. Acad. Sci. 1998 95:13899 – 13904