Deletion of Fibrinogen-like Protein 2 (FGL-2), a Novel CD4+ CD25+ Treg Effector Molecule, Leads to Improved Control of Echinococcus multilocularis Infection in Mice

Junhua Wang; Dominique A Vuitton; Norbert Müller; Andrew Hemphill; Markus Spiliotis; Oleg Blagosklonov; Denis Grandgirard; Stephen L Leib; Itay Shalev; Gary Levy; Xiaomei Lu; Renyong Lin; Hao Wen; Bruno Gottstein

doi:10.1371/journal.pntd.0003755

Deletion of Fibrinogen-like Protein 2 (FGL-2), a Novel CD4+ CD25+ Treg Effector Molecule, Leads to Improved Control of Echinococcus multilocularis Infection in Mice

PLoS Negl Trop Dis. 2015 May 8;9(5):e0003755. doi: 10.1371/journal.pntd.0003755. eCollection 2015 May.

Authors

Affiliations

¹ Institute of Parasitology, University of Bern, Bern, Switzerland; State Key Lab Incubation Base of Xinjiang Major Diseases Research (2010DS890294) and Xinjiang Key Laboratory of Echinococcosis, First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, China; Department of Nuclear Medicine, University of Franche-Comté and Jean Minjoz University Hospital, Besançon, Franche-Comté, France.
² World Health Organization (WHO)-Collaborating Centre for the Prevention and Treatment of Human Echinococcosis, University of Franche-Comté and University Hospital, Besançon, Franche-Comté, France.
³ Institute of Parasitology, University of Bern, Bern, Switzerland.
⁴ Department of Nuclear Medicine, University of Franche-Comté and Jean Minjoz University Hospital, Besançon, Franche-Comté, France.
⁵ Neuroinfection Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland.
⁶ Neuroinfection Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland; Biology Division, Spiez Laboratory, Federal Office for Civil Protection (FOCP), Spiez, Switzerland.
⁷ University of Toronto Transplantation Institute, Toronto, Ontario, Canada.
⁸ State Key Lab Incubation Base of Xinjiang Major Diseases Research (2010DS890294) and Xinjiang Key Laboratory of Echinococcosis, First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, China.

Abstract

Background: The growth potential of the tumor-like Echinococcus multilocularis metacestode (causing alveolar echinococcosis, AE) is directly linked to the nature/function of the periparasitic host immune-mediated processes. We previously showed that Fibrinogen-like-protein 2 (FGL2), a novel CD4+CD25+ Treg effector molecule, was over-expressed in the liver of mice experimentally infected with E. multilocularis. However, little is known about its contribution to the control of this chronic helminth infection.

Methods/findings: Key parameters for infection outcome in E. multilocularis-infected fgl2-/- (AE-fgl2-/-) and wild type (AE-WT) mice at 1 and 4 month(s) post-infection were (i) parasite load (i. e. wet weight of parasitic metacestode tissue), and (ii) parasite cell proliferation as assessed by determining E. multilocularis 14-3-3 gene expression levels. Serum FGL2 levels were measured by ELISA. Spleen cells cultured with ConA for 48h or with E. multilocularis Vesicle Fluid (VF) for 96h were analyzed ex-vivo and in-vitro. In addition, spleen cells from non-infected WT mice were cultured with rFGL2/anti-FGL2 or rIL-17A/anti-IL-17A for further functional studies. For Treg-immune-suppression-assays, purified CD4+CD25+ Treg suspensions were incubated with CD4+ effector T cells in the presence of ConA and irradiated spleen cells as APCs. Flow cytometry and qRT-PCR were used to assess Treg, Th17-, Th1-, Th2-type immune responses and maturation of dendritic cells. We showed that AE-fgl2-/- mice exhibited (as compared to AE-WT-animals) (a) a significantly lower parasite load with reduced proliferation activity, (b) an increased T cell proliferative response to ConA, (c) reduced Treg numbers and function, and (d) a persistent capacity of Th1 polarization and DC maturation.

Conclusions: FGL2 appears as one of the key players in immune regulatory processes favoring metacestode survival by promoting Treg cell activity and IL-17A production that contributes to FGL2-regulation. Prospectively, targeting FGL2 could be an option to develop an immunotherapy against AE and other chronic parasitic diseases.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
CD4 Antigens
Concanavalin A / immunology
Dendritic Cells / cytology
Dendritic Cells / immunology
Echinococcosis
Echinococcosis, Hepatic / immunology*
Echinococcosis, Hepatic / parasitology
Echinococcus multilocularis / immunology*
Fibrinogen / genetics
Fibrinogen / immunology*
Flow Cytometry
Interleukin-17 / biosynthesis*
Mice
T-Lymphocytes, Regulatory / immunology*
Th1 Cells / immunology
Th17 Cells / immunology
Th2 Cells / immunology

Substances

CD4 Antigens
Fgl2 protein, mouse
Interleukin-17
Concanavalin A
Fibrinogen

Supplementary concepts

Alveolar echinococcosis

Grants and funding

This work was funded by: Swiss National Science Foundation (grant number 31003A_141039/1) [BG], Natural Science Fundation of China (NSFC) Grant Projects (grant numbers 81260452 [JW], 81260252 [RL], U1303222 [HW]), the European Commission French-Swiss InterReg IV program ‘IsotopEchino’ project [BG, DAV], the Program for Changjiang Scholars and Innovative Research Team in Universities (grant number IRT1181) [HW] and Xinjiang Key-Lab Projects (grant number SKLIB-XJMDR-2012-Y1) [JW]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.