Extracellular Vesicles in Host-Parasite Interaction of Entamoeba histolytica with Primary Monocytes
Background
Amebic liver abscesses (ALAs) are formed when the protozoan parasite Entamoeba histolytica disseminates from the intestine to the liver. The immune response underlying ALA formation is crucially mediated by monocytes and differs between the sexes, resulting in a male bias to ALA. While pro-inflammatory Ly6Chi monocytes are known to drive pathology, Ly6Clo monocytes have been shown to contribute to tissue repair in a murine ALA model. In order to further investigate the interaction of E. histolytica with the host immune system, we here studied the role of parasitic EVs in interaction with monocytes.
Methods
EVs were isolated from two amebic clones of different virulence (low pathogenic EhA1 and highly pathogenic EhB2) by differential ultracentrifugation and characterized using NTA and TEM. Mass spectrometry and miRNA sequencing were employed for the characterization of the EV content. The effect of these EVs on primary murine monocytes was assessed after in vitro stimulation using cytokine assays, flow cytometry, RT-qPCR and bulk RNA sequencing.
Results
Analysis of the EV proteome and miRNA cargo, including novel predicted E. histolytica miRNAs, revealed considerable differences between the two clones that may be relevant in the context of pathogenicity. Stimulation of male- and female-derived monocytes resulted in a pro-inflammatory immune response to EVs of both clones. This was characterized by increased release of pro-inflammatory cytokines and chemokines, which was higher in male-derived cells, and a higher surface expression of the activation marker CD38 compared with negative controls. RNA sequencing revealed the upregulation of genes involved in key immune pathways. EhA1 EVs triggered release of the enzyme myeloperoxidase by stimulated monocytes, whereas EhB2 EVs did not.
Conclusion
Taken together, our results suggest that E. histolytica-derived EVs may be involved in the immunopathology of ALA mediated by pro-inflammatory monocytes and provide insight into factors involved in amebic pathogenicity.
Keywords
Parasite, Infection, Immune Response, Monocyte
Funding/Acknowledgments
Joachim Herz Foundation
Authors
Barbara Honecker1 (Corresponding author: Barbara Honecker, barbara.honecker[at]bnitm[dot]de), Valentin Bärreiter1, Nahla Galal Metwally1, Katharina Höhn1, Pilar Martínez Tauler1, Stephanie Leyk1, Karel Harant2, Dániel Cadar1, Stephan Lorenzen1, Balázs Horváth1, Claudia Marggraff1, Hanna Lotter1, Iris Bruchhaus1