Wang Junhua, Vuitton Dominique A, Müller Norbert, Hemphill Andrew, Spiliotis Markus, Blagosklonov Oleg, Grandgirard Denis, Leib Stephen L, Shalev Itay, Levy Gary, Lu Xiaomei, Lin Renyong, Wen Hao, Gottstein Bruno
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.
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.
PLoS Negl Trop Dis. 2015 May 8;9(5):e0003755. doi: 10.1371/journal.pntd.0003755. eCollection 2015 May.
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.
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.
类肿瘤泡球蚴（导致肺泡型包虫病，AE）的生长潜能与寄生虫周围宿主免疫介导过程的性质/功能直接相关。我们之前发现，纤维蛋白原样蛋白2（FGL2），一种新型的CD4+CD25+调节性T细胞效应分子，在实验感染多房棘球绦虫的小鼠肝脏中过度表达。然而，关于其在控制这种慢性蠕虫感染中的作用知之甚少。
方法/研究结果：在感染多房棘球绦虫的fgl2-/-（AE-fgl2-/-）和野生型（AE-WT）小鼠感染后1个月和4个月时，感染结局的关键参数为：（i）寄生虫负荷（即寄生性类肿瘤组织的湿重），以及（ii）通过测定多房棘球绦虫14-3-3基因表达水平评估的寄生虫细胞增殖。通过ELISA测定血清FGL2水平。用刀豆蛋白A（ConA）培养48小时或用多房棘球绦虫囊液（VF）培养96小时的脾细胞进行体外和体内分析。此外，将未感染的WT小鼠的脾细胞与重组FGL2/抗FGL2或重组白细胞介素-17A/抗白细胞介素-17A一起培养，进行进一步的功能研究。对于调节性T细胞免疫抑制试验，将纯化的CD4+CD25+调节性T细胞悬液与CD4+效应T细胞在ConA存在下以及作为抗原呈递细胞的辐照脾细胞一起孵育。使用流式细胞术和定量逆转录-聚合酶链反应评估调节性T细胞、辅助性T细胞17、辅助性T细胞1、辅助性T细胞2型免疫反应以及树突状细胞的成熟。我们发现，与AE-WT动物相比，AE-fgl2-/-小鼠表现出：（a）寄生虫负荷显著降低，增殖活性降低；（b）对ConA的T细胞增殖反应增加；（c）调节性T细胞数量和功能降低；以及（d）辅助性T细胞1极化和树突状细胞成熟的持续能力。
FGL2似乎是免疫调节过程中的关键参与者之一，通过促进调节性T细胞活性和白细胞介素-17A产生来促进类肿瘤存活，这有助于FGL2调节。前瞻性地，靶向FGL2可能是开发针对肺泡型包虫病和其他慢性寄生虫病的免疫疗法的一种选择。
