Modelling staphylococcal pneumonia in a human 3D lung tissue model system delineates toxin-mediated pathology.

Abstract

Staphylococcus aureus necrotizing pneumonia is recognized as a toxin-mediated disease, yet the tissue-destructive events remain elusive, partly as a result of lack of mechanistic studies in human lung tissue. In this study, a three-dimensional (3D) tissue model composed of human lung epithelial cells and fibroblasts was used to delineate the role of specific staphylococcal exotoxins in tissue pathology associated with severe pneumonia. To this end, the models were exposed to the mixture of exotoxins produced by S. aureus strains isolated from patients with varying severity of lung infection, namely necrotizing pneumonia or lung empyema, or to purified toxins. The necrotizing pneumonia strains secreted high levels of α-toxin and Panton-Valentine leukocidin (PVL), and triggered high cytotoxicity, inflammation, necrosis and loss of E-cadherin from the lung epithelium. In contrast, the lung empyema strain produced moderate levels of PVL, but negligible amounts of α-toxin, and triggered limited tissue damage. α-toxin had a direct damaging effect on the epithelium, as verified using toxin-deficient mutants and pure α-toxin. Moreover, PVL contributed to pathology through the lysis of neutrophils. A combination of α-toxin and PVL resulted in the most severe epithelial injury. In addition, toxin-induced release of pro-inflammatory mediators from lung tissue models resulted in enhanced neutrophil migration. Using a collection of 31 strains from patients with staphylococcal pneumonia revealed that strains producing high levels of α-toxin and PVL were cytotoxic and associated with fatal outcome. Also, the strains that produced the highest toxin levels induced significantly greater epithelial disruption. Of importance, toxin-mediated lung epithelium destruction could be inhibited by polyspecific intravenous immunoglobulin containing antibodies against α-toxin and PVL. This study introduces a novel model system for study of staphylococcal pneumonia in a human setting. The results reveal that the combination and levels of α-toxin and PVL correlate with tissue pathology and clinical outcome associated with pneumonia.

• Authors: Srikanth Mairpady Shambat, Puran Chen, Anh Thu Nguyen Hoang, Helena Bergsten, Francois Vandenesch, Nikolai Siemens, Gerard Lina, Ian R Monk, Timothy J Foster, Gayathri Arakere, Mattias Svensson, Anna Norrby-Teglund
• Journal: Disease models & mechanisms (Dis Model Mech) Vol. 8 Issue 11 Pg. 1413-25 (Nov 2015) ISSN: 1754-8411 [Electronic] England
• PMID: 26398950 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2015. Published by The Company of Biologists Ltd.

Chemical References

• Bacterial Toxins
• Exotoxins
• Hemolysin Proteins
• Immunoglobulins, Intravenous
• Immunologic Factors
• Inflammation Mediators
• Leukocidins
• Panton-Valentine leukocidin
• staphylococcal alpha-toxin

Topics

• Bacterial Toxins (immunology, metabolism)
• Cell Line, Tumor
• Chemotaxis
• Coculture Techniques
• Empyema, Pleural (immunology, metabolism, microbiology, pathology)
• Epithelial Cells (drug effects, immunology, metabolism, microbiology, pathology)
• Exotoxins (immunology, metabolism)
• Fibroblasts (metabolism, microbiology, pathology)
• Hemolysin Proteins (immunology, metabolism)
• Humans
• Immunoglobulins, Intravenous (pharmacology)
• Immunologic Factors (pharmacology)
• Inflammation Mediators (metabolism)
• Leukocidins (immunology, metabolism)
• Lung (drug effects, immunology, metabolism, microbiology, pathology)
• Necrosis
• Neutrophil Infiltration
• Pneumonia, Staphylococcal (drug therapy, immunology, metabolism, microbiology, pathology)
• Staphylococcus aureus (classification, drug effects, immunology, metabolism, pathogenicity)
• Time Factors