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Staphylococcus aureus membrane vesicles contain immunostimulatory DNA, RNA and peptidoglycan that activate innate immune receptors and induce autophagy

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journal contribution
posted on 03.05.2021, 05:37 by Natalie BittoNatalie Bitto, Lesley SimLesley Sim, Ella JohnstonElla Johnston, Rishi Pathirana, Thanh PhanThanh Phan, Ivan PoonIvan Poon, Neil M O'Brien-Simpson, Andrew HillAndrew Hill, Timothy P Stinear, Maria LiaskosMaria Liaskos
Gram-positive bacteria ubiquitously produce membrane vesicles (MVs), and although they contribute to biological functions, our knowledge regarding their composition and immunogenicity remains limited. Here we examine the morphology, contents and immunostimulatory functions of MVs produced by three Staphylococcus aureus strains; a methicillin resistant clinical isolate, a methicillin sensitive clinical isolate and a laboratory-adapted strain. We observed differences in the number and morphology of MVs produced by each strain and showed that they contain microbe-associated molecular patterns (MAMPs) including protein, nucleic acids and peptidoglycan. Analysis of MV-derived RNA indicated the presence of small RNA (sRNA). Furthermore, we detected variability in the amount and composition of protein, nucleic acid and peptidoglycan cargo carried by MVs from each S. aureus strain. S. aureus MVs activated Toll-like receptor (TLR) 2, 7, 8, 9 and nucleotide-binding oligomerization domain containing protein 2 (NOD2) signalling and promoted cytokine and chemokine release by epithelial cells, thus identifying that MV-associated MAMPs including DNA, RNA and peptidoglycan are detected by pattern recognition receptors (PRRs). Moreover, S. aureus MVs induced the formation of and colocalized with autophagosomes in epithelial cells, while inhibition of lysosomal acidification using bafilomycin A1 resulted in accumulation of autophagosomal puncta that colocalized with MVs, revealing the ability of the host to degrade MVs via autophagy. This study reveals the ability of DNA, RNA and peptidoglycan associated with MVs to activate PRRs in host epithelial cells, and their intracellular degradation via autophagy. These findings advance our understanding of the immunostimulatory roles of Gram-positive bacterial MVs in mediating pathogenesis, and their intracellular fate within the host.

Funding

This work was supported by the Australian Research Council (Project: Maria Kaparakis-Liaskos, Andrew F. Hill) under Grant DP190101655; the National Health and Medical Research Council (Project: Maria Kaparakis-Liaskos) under Grant 1107800 and a La Trobe University RFA Understanding Diseases Grant (Maria Kaparakis-Liaskos, Timothy P. Stinear). Maria Kaparakis-Liaskos is supported by a veski Inspiring Women Fellowship. This work was supported by the LIMS Bioimaging Facility (La Trobe University). We would like to acknowledge Natasha Holmes for her work in sourcing the S. aureus clinical isolates used in this study.

History

Publication Date

01/04/2021

Journal

Journal Of Extracellular Vesicles

Volume

10

Issue

6

Article Number

ARTN e12080

Pagination

19p.

Publisher

WILEY

ISSN

2001-3078

Rights Statement

The Author reserves all moral rights over the deposited text and must be credited if any re-use occurs. Documents deposited in OPAL are the Open Access versions of outputs published elsewhere. Changes resulting from the publishing process may therefore not be reflected in this document. The final published version may be obtained via the publisher’s DOI. Please note that additional copyright and access restrictions may apply to the published version.