Entamoeba histolyticaextracellular vesicles drive pro-inflammatory monocyte signaling
Authors: Honecker Barbara , Bärreiter Valentin A. , Höhn Katharina , Horváth Balázs , Harant Karel , Galal Metwally Nahla , Marggraff Claudia , Anders Juliett , Leyk Stephanie , Martínez-Tauler Maria del Pilar , Bea Annika , Hansen Charlotte , Fehling Helena , Lütkemeyer Melanie , Lorenzen Stephan , Franzenburg Sören , Lotter Hanna , Bruchhaus Iris 
Published: December 2024

The parasitic protozoanEntamoeba histolyticasecretes extracellular vesicles (EVs), but so far little is known about their function in the interaction with the host immune system. Infection withE. histolyticatrophozoites can lead to formation of amebic liver abscesses (ALAs), in which pro-inflammatory immune responses of Ly6Chimonocytes contribute to liver damage. Men exhibit a more severe pathology as the result of higher monocyte recruitment and a stronger immune response. To investigate the role of EVs and pathogenicity in the host immune response, we studied the effect of EVs secreted by low pathogenicEhA1 and highly pathogenicEhB2 amebae on monocytes. Size and quantity of isolated EVs from both clones were similar. However, they differed in their proteome and miRNA cargo, providing insight into factors potentially involved in amebic pathogenicity. In addition, EVs were enriched in proteins with signaling peptides compared with the total protein content of trophozoites. Exposure to EVs from both clones induced monocyte activation and a pro-inflammatory immune response as evidenced by increased surface presentation of the activation marker CD38 and upregulated gene expression of key signaling pathways (including NF-κB, IL-17 and TNF signaling). The release of pro-inflammatory cytokines was increased in EV-stimulated monocytes and more so in male-than in female-derived cells. WhileEhA1 EV stimulation caused elevated myeloperoxidase (MPO) release by both monocytes and neutrophils,EhB2 EV stimulation did not, indicating the protective role of MPO during amebiasis. Collectively, our results suggest that parasite-released EVs contribute to the male-biased immunopathology mediated by pro-inflammatory monocytes during ALA formation.

Author summary

Parasites communicate with their host via small membranous extracellular vesicles (EVs) that can shuttle cargo and thus information between cells. The protozoan parasiteEntamoeba histolyticareleases EVs but not much is known about their role in the interaction with the host immune system. Infection withE. histolyticacan lead to amebic liver abscess (ALA) formation. Innate immune cells, particularly monocytes, contribute to liver damage by releasing microbicidal factors. Men have a more severe ALA pathology as the result of a stronger monocyte immune response. In this study, we analyzed the effect of EVs from differently virulentE. histolyticaclones on monocytes to better understand their interaction. EVs of both clones were similar in size and quantity but differed in their cargo, which provides information on factors potentially involved in pathogenicity. Monocytes responded to EVs of both clones in a pro-inflammatory manner that reflected the immune processes occurring during ALAin vivo, including the bias towards the male sex. Only EVs of amebae with low pathogenicity, and not those released by the highly pathogenic clone, elicited secretion of the granular enzyme myeloperoxidase, which plays a protective role during ALA. Overall, our data suggest that EVs may contribute to liver injury.