Release of Staphylococcus aureus extracellular vesicles and their application as a vaccine platform

Xiaogang Wang,Christopher Weidenmaier,Jean C Lee,Christopher D Thompson

doi:10.1038/s41467-018-03847-z

Abstract

Secretion of extracellular vesicles (EVs), a process common to eukaryotes, archae, and bacteria, represents a secretory pathway that allows cell-free intercellular communication. Microbial EVs package diverse proteins and influence the host-pathogen interaction, but the mechanisms underlying EV production in Gram-positive bacteria are poorly understood. Here we show that EVs purified from community-associated methicillin-resistant Staphylococcus aureus package cytosolic, surface, and secreted proteins, including cytolysins. Staphylococcal alpha-type phenol-soluble modulins promote EV biogenesis by disrupting the cytoplasmic membrane; whereas, peptidoglycan cross-linking and autolysin activity modulate EV production by altering the permeability of the cell wall. We demonstrate that EVs purified from a S. aureus mutant that is genetically engineered to express detoxified cytolysins are immunogenic in mice, elicit cytolysin-neutralizing antibodies, and protect the animals in a lethal sepsis model. Our study reveals mechanisms underlying S. aureus EV production and highlights the usefulness of EVs as a S. aureus vaccine platform.

Highlights

Secretion of extracellular vesicles (EVs), a process common to eukaryotes, archae, and bacteria, represents a secretory pathway that allows cell-free intercellular communication
Ultrathin sections of JE219 cells examined by transmission electron microscopy (TEM) revealed vesicle-like structures released from the S. aureus cell surface (Fig. 1a)
To determine whether the presence of capsular polysaccharide (CP) production impacted S. aureus EV biogenesis, we evaluated a number of isogenic CP+ and CP− strains

Summary

Introduction

Secretion of extracellular vesicles (EVs), a process common to eukaryotes, archae, and bacteria, represents a secretory pathway that allows cell-free intercellular communication. Microbial EVs package diverse proteins and influence the host-pathogen interaction, but the mechanisms underlying EV production in Gram-positive bacteria are poorly understood. We show that EVs purified from community-associated methicillin-resistant Staphylococcus aureus package cytosolic, surface, and secreted proteins, including cytolysins. Our study reveals mechanisms underlying S. aureus EV production and highlights the usefulness of EVs as a S. aureus vaccine platform. The mechanisms by which cytoplasmic proteins are excreted by S. aureus have attracted recent interest[4,5], and there is increasing evidence that these proteins may be secreted within extracellular membrane vesicles (EVs)[6,7,8,9]. Recent work has described the production and release of EVs from Gram-positive bacteria and fungi[6,7,8,9,14]. The development of EVs as a S. aureus vaccine platforms will require characterization of the mechanisms of EV biogenesis to enable consistent production with adequate quality assurance

Methods

Results

Conclusion