Sulaiman Azad A, Zolnierczyk Katarzyna, Japa Ornampai, Owen Jonathan P, Maddison Ben C, Emes Richard D, Hodgkinson Jane E, Gough Kevin C, Flynn Robin J
School of Veterinary Medicine and Science, the University of Nottingham, Sutton Bonington Campus, Nottingham, United Kingdom.
School of Medicine, University of Phayao, Phayao, Thailand.
PLoS Pathog. 2016 Nov 2;12(11):e1005991. doi: 10.1371/journal.ppat.1005991. eCollection 2016 Nov.
The trematode Fasciola hepatica is responsible for chronic zoonotic infection globally. Despite causing a potent T-helper 2 response, it is believed that potent immunomodulation is responsible for rendering this host reactive non-protective host response thereby allowing the parasite to remain long-lived. We have previously identified a growth factor, FhTLM, belonging to the TGF superfamily can have developmental effects on the parasite. Herein we demonstrate that FhTLM can exert influence over host immune functions in a host receptor specific fashion. FhTLM can bind to receptor members of the Transforming Growth Factor (TGF) superfamily, with a greater affinity for TGF-β RII. Upon ligation FhTLM initiates the Smad2/3 pathway resulting in phenotypic changes in both fibroblasts and macrophages. The formation of fibroblast CFUs is reduced when cells are cultured with FhTLM, as a result of TGF-β RI kinase activity. In parallel the wound closure response of fibroblasts is also delayed in the presence of FhTLM. When stimulated with FhTLM blood monocyte derived macrophages adopt an alternative or regulatory phenotype. They express high levels interleukin (IL)-10 and arginase-1 while displaying low levels of IL-12 and nitric oxide. Moreover they also undergo significant upregulation of the inhibitory receptor PD-L1 and the mannose receptor. Use of RNAi demonstrates that this effect is dependent on TGF-β RII and mRNA knock-down leads to a loss of IL-10 and PD-L1. Finally, we demonstrate that FhTLM aids newly excysted juveniles (NEJs) in their evasion of antibody-dependent cell cytotoxicity (ADCC) by reducing the NO response of macrophages-again dependent on TGF-β RI kinase. FhTLM displays restricted expression to the F. hepatica gut resident NEJ stages. The altered fibroblast responses would suggest a role for dampened tissue repair responses in facilitating parasite migration. Furthermore, the adoption of a regulatory macrophage phenotype would allow for a reduced effector response targeting juvenile parasites which we demonstrate extends to an abrogation of the ADCC response. Thus suggesting that FhTLM is a stage specific evasion molecule that utilises host cytokine receptors. These findings are the first to clearly demonstrate the interaction of a helminth cytokine with a host receptor complex resulting in immune modifications that facilitate the non-protective chronic immune response which is characteristic of F. hepatica infection.
肝片吸虫是一种全球范围内引起慢性人畜共患感染的吸虫。尽管它会引发强烈的辅助性T细胞2型反应,但据信强大的免疫调节作用导致宿主产生反应性非保护性宿主反应,从而使寄生虫能够长期存活。我们之前鉴定出一种属于转化生长因子(TGF)超家族的生长因子FhTLM,它对寄生虫具有发育影响。在此我们证明,FhTLM能够以宿主受体特异性方式影响宿主免疫功能。FhTLM可以与转化生长因子(TGF)超家族的受体成员结合,对TGF-β RII具有更高亲和力。结合后,FhTLM启动Smad2/3信号通路,导致成纤维细胞和巨噬细胞发生表型变化。当细胞与FhTLM一起培养时,由于TGF-β RI激酶活性,成纤维细胞集落形成单位(CFU)的形成减少。同时,在FhTLM存在的情况下,成纤维细胞的伤口闭合反应也会延迟。当受到FhTLM刺激时,血液单核细胞衍生的巨噬细胞会呈现替代或调节性表型。它们高水平表达白细胞介素(IL)-10和精氨酸酶-1,而低水平表达IL-12和一氧化氮。此外,它们还会使抑制性受体PD-L1和甘露糖受体显著上调。RNA干扰的应用表明这种效应依赖于TGF-β RII,mRNA敲低会导致IL-10和PD-L1缺失。最后,我们证明FhTLM通过降低巨噬细胞的一氧化氮反应,再次依赖于TGF-β RI激酶,帮助新脱囊的幼虫(NEJ)逃避抗体依赖性细胞毒性(ADCC)。FhTLM仅在肝片吸虫肠道驻留的NEJ阶段表达。成纤维细胞反应改变表明在促进寄生虫迁移方面,组织修复反应减弱起到了一定作用。此外,调节性巨噬细胞表型的形成会使针对幼虫寄生虫的效应反应减弱,我们证明这延伸至ADCC反应的消除。因此表明FhTLM是一种利用宿主细胞因子受体的阶段特异性逃避分子。这些发现首次清楚地证明了一种蠕虫细胞因子与宿主受体复合物的相互作用,导致免疫修饰促进了肝片吸虫感染特有的非保护性慢性免疫反应。