Staphylococcus aureus internalisation in mast cells in nasal polyps - Characterisation of interactions and potential mechanisms

Stephen H. Hayes, PhDa,b,c,d

, 

Timothy C. Biggs, MRCSa,b,c,d

, 

Simon P. Goldie, MRCSa,b,c,d

, 

Philip G. Harries, FRCSc

, 

Andrew F. Walls, PhDa

, 

Raymond N. Allan, PhDd,e

, 

Sylvia L.F. Pender, PhDa

, 

Rami J. Salib, PhDa,b,c,d,∗,Correspondence information about the author PhD Rami J. SalibEmail the author PhD Rami J. Salib

DOI: https://doi.org/10.1016/j.jaci.2019.06.013

Article Info

Publication History

Published online:June 26, 2019Accepted:June 4, 2019Received in revised form:May 30, 2019Received:November 16, 2018

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Abstract

Background

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a common chronic condition. The exact cause of nasal polyps remains unknown. Recently, we made the novel observation of intracellular localisation of Staphylococcus aureus (S aureus) within mast cells in nasal polyps.

Objective

This follow-up study aimed to further characterise interactions between S aureus and mast cells in this setting, and elucidate potential internalisation mechanisms with particular emphasis on the role of S aureus enterotoxin B (SEB).

Methods

A prospective study was performed using an explant tissue model with ex vivo inferior turbinate mucosa obtained from CRSwNP patients (n=7) and non-CRS (n=5) patients. Immunohistochemistry was used to characterise S aureus uptake into mast cells and investigate the effects of SEB on this process. An in vitro cell culture model was used to investigate mast cell-S aureus interactions using a combination of fluorescent in situ hybridisation, confocal laser scanning microscopy, scanning electron microscopy, transmission electron microscopy, and proliferation assays.

Results

S aureus were entrapped by extracellular traps and entered mast cells through phagocytosis. Proliferating intracellular S aureus led to the expansion and eventual rupture of mast cells, resulting in release of viable S aureus into the extracellular space. The presence of SEB appeared to promote internalisation of S aureus into mast cells.

Conclusion

This study provides new insights into the interactions between S aureus and mast cells, including the internalisation process, and demonstrates a prominent role for SEB in promoting uptake of the bacteria into these cells.

Key Words:

Chronic rhinosinusitis, chronic rhinosinusitis with nasal polyps, nasal polyps, intracellular bacteria, Staphylococcus aureus, mast cells, bacterial superantigens, SEB

Abbreviations:

CLSM (Confocal Laser Scanning Microscopy), CRS (Chronic rhinosinusitis), CRSsNP (Chronic rhinosinusitis without nasal polyps), CRSwNP (Chronic rhinosinusitis with nasal polyps), CFU (Colony Forming Unit), DAB (3,3’-Diaminobenzidine), DAPI (4’,6’-diamidino-2-phenylindole), GMA (Glycol methacrylate), HBSS (Hank’s Balanced Salt Solution), HMC-1 (Human mast cell culture line 1), IBDR (Intracellular bacteria detection rate), IFNγ(Interferon Gamma), IgE (Immunoglobulin E), IL (Interleukin), MOI (Multiplicity of infection), PBS (Phosphate Buffered Saline), PIPES (Piperazine-N,N′-bis), RANTES (Regulated on Activation, Normal T Cell Expressed and Secreted), RPMI (Roswell Park Memorial Institute medium), S aureus (Staphylococcus aureus), SEB(Staphylococcus enterotoxin B), SPT (Skin Prick Test), TEM (Transmission Electron Microscopy), TGFβ(Transforming Growth Factor Beta), TH1 (T helper 1), TH2 (T helper 2), TNFα (Tumour Necrosis Factor Alpha)