Background/Objectives
Streptococcus pneumoniae-induced hemolytic uremic syndrome (Sp-HUS) is a kidney disease characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. This disease is frequently underdiagnosed and its pathophysiology is poorly understood. In this work, we compared clinical strains, isolated from infant Sp-HUS patients, with a reference pathogenic strain D39, for host cytotoxicity and further explored the role of Sp-derived extracellular vesicles (EVs) in the pathogenesis of an HUS infection.
Methods
Isolated Sp-HUS EVs were characterized for their morphology, cargo (proteomic analysis) and host interaction. Immunoregu- lation was tested by performing cytokine and chemokine measurements, adherence and internalization microscopy assays and a co- cultivation model was established.
Results
Sp-HUS strain released EVs at a constant concentration during growth, yet the size of the EVs varied and several subpopula- tions emerged at later time points. The cargo of the Sp-HUS EVs included several virulence factors at high abundance, i.e., the ribosomal subunit assembly factor BipA, the pneumococcal surface protein A, the lytic enzyme LytC, several sugar utilization, and fatty acid syn- thesis proteins. Sp-HUS EVs strongly downregulated the expression of the endothelial surface marker platelet endothelial cell adhesion molecule-1 and were internalized by human endothelial cells. Sp-HUS EVs elicited the release of pro-inflammatory cytokines (interleukin [IL]-1β, IL-6) and chemokines (CCL2, CCL3, CXCL1) by human monocytes.
Conclusion
These findings shed new light on the overall function of Sp-EVs, in the scope of infection-mediated HUS, and suggest new avenues of research for exploring the usefulness of Sp-EVs as therapeutic and diagnostic targets.
Keywords
extracellular vesicles, immunomodulation, cytokines, microbe-host
Funding/Acknowledgments
The work of the authors is supported by the Collaborative Research Center, FungiNet [project C6 (PFZ)] Deutsche Forschungsgemeinschaft (DFG). S.H. received funding by the Deutsche Forschungsgemeinschaft DFG HA 3125/5–2 and DFG- GRK 2719. M.T.F. has acquired funding for B.H., supported by the Leibniz ScienceCampus InfectoOptics Jena, which is financed by the funding line Strategic Networking of the Leibniz Association. M.T.F. has acquired funding for Y.B., supported by the MuMoSim project (grant number 031L0291A), which is financed by the Ministry of Education and Research, Germany.
We thank the Microverse Imaging Center for providing microscope facility support for data acquisition.
