Modulation of the mTOR pathway plays a central role in dendritic cell functions after Echinococcus granulosus antigen recognition

Christian Rodriguez Rodrigues,Andrea C Cumino,Mora Massaro,Julia Loos,Maia Chop,María Celeste Nicolao,Natalia Plá

doi:10.1038/s41598-021-96435-z

Abstract

Immune evasion is a hallmark of persistent echinococcal infection, comprising modulation of innate immune cells and antigen-specific T cell responses. However, recognition of Echinococcus granulosus by dendritic cells (DCs) is a key determinant of the host's response to this parasite. Given that mTOR signaling pathway has been described as a regulator linking metabolism and immune function in DCs, we reported for the first time in these cells, global translation levels, antigen uptake, phenotype, cytokine transcriptional levels, and splenocyte priming activity upon recognition of the hydatid fluid (HF) and the highly glycosylated laminar layer (LL). We found that LL induced a slight up-regulation of CD86 and MHC II in DCs and also stimulated the production of IL-6 and TNF-α. By contrast, HF did not increase the expression of any co-stimulatory molecules, but also down-modulated CD40 and stimulated the expression of the anti-inflammatory cytokine IL-10. Both parasitic antigens promoted protein synthesis through mTOR activation. The use of rapamycin decreased the expression of the cytokines tested, empowered the down-modulation of CD40 and also reduced splenocyte proliferation. Finally, we showed that E. granulosus antigens increase the amounts of LC3-positive structures in DCs which play critical roles in the presentation of these antigens to T cells.

Highlights

Immune evasion is a hallmark of persistent echinococcal infection, comprising modulation of innate immune cells and antigen-specific T cell responses
The laminar layer of E. granulosus enhance translation in Bone Marrow Dendritic Cells (BMDCs) compared to control cells. purified laminar layer (pLL), showed statistically significant differences of puromycin detection, similar to that detected in LPS-stimulated BMDCs
We corroborated that the stimulation of BMDCs with pLL and hydatid fluid (HF) did not cause a significant decrease in cell viability (Fig. 1A), both antigens were used for the subsequent studies

Summary

Introduction

Immune evasion is a hallmark of persistent echinococcal infection, comprising modulation of innate immune cells and antigen-specific T cell responses. The cyst may rupture or slowly leak out, permeate into a coelomic cavity, open on an epithelial surface or empty into the lumen of a hollow organ, leading to different host immune responses, ranging from a severe anaphylactic shock to a spontaneous resolution of the infection[6] In this context, Eg-antigens of metacestodes exposed and released in the tissues, lymphatics and circulation could be detected by dendritic cells (DCs). Three independent experiments were performed. (D) Bar graph show the MHC II mean intensity of twenty different cells in a representative experiment (one-way ANOVA test ****p < 0.0001 and Tukey post hoc test, *p < 0.01 HF-stimulated cells vs control)

Methods

Results

Conclusion