Clonorchis sinensis adult-derived proteins elicit Th2 immune responses by regulating dendritic cells via mannose receptor

Abstract

BackgroundClonorchis sinensis (C. sinensis) is the most widespread human liver fluke in East Asia including China and Korea. Clonorchiasis as a neglected tropical zoonosis, leads to serious economic and public health burden in China. There are considerable evidences for an etiological relation between chronic clonorchiasis and liver fibrosis in human beings. Liver fibrosis is a highly conserved and over-protected response to hepatic tissue injury. Immune cells including CD4+ T cell as well as dendritic cell (DC), and pro-fibrogenic cytokines like interleukin 4 (IL-4), IL-13 have been identified as vital manipulators in liver fibrogenesis. Our previous studies had a mere glimpse of T helper type 2 (Th2) dominant immune responses as key players in liver fibrosis induced by C. sinensis infection, but little is known about the involved mechanisms in this pathological process.Methodology/Principal findingsBy flow cytometry (FACS), adult-derived total proteins of C. sinensis (CsTPs) down-regulated the expression of surface markers CD80, CD86 and major histocompatibility complex class II (MHC-II) on lipopolysaccharide (LPS) induced DC. ELISA results demonstrated that CsTPs inhibited IL-12p70 release from LPS-treated bone marrow-derived dendritic cells (BMDC). IL-10 level increased in a time-dependent manner in LPS-treated BMDCs after incubation with CsTPs. CD4+ T cells incubated with LPS-treated BMDCs plus CsTPs could significantly elevate IL-4 level by ELISA. Meanwhile, elevated expression of pro-fibrogenic mediators including IL-13 and IL-4 were detected in a co-culture system of LPS-activated BMDCs and naive T cells containing CsTPs. In vivo, CsTPs-immunized mice enhanced expression of type 2 cytokines IL-13, IL-10 and IL-4 in both splenocytes and hepatic tissue. Exposure of BMDCs to CsTPs activated expression of mannose receptor (MR) but not toll like receptor 2 (TLR2), TLR4, C-type lectin receptor DC-SIGN and Dectin-2 on the cell surface by RT-PCR and FACS. Blockade of MR almost completely reversed the capacity of CsTPs to suppress LPS-induced BMDCs surface markers CD80, CD86 and MHC-II expression, and further made these BMDCs fail to induce a Th2-skewed response as well as Th2 cell-associated cytokines IL-13 and IL-4 release in vitro.Conclusions/SignificanceCollectively, we validated that CsTPs could suppress the maturation of BMDCs in the presence of LPS via binding MR, and showed that the CsTPs-pulsed BMDCs actively polarized naive T helper cells to Th2 cells though the production of IL-10 instead of IL-12. CsTPs endowed host with the capacity to facilitate Th2 cytokines production including IL-13 and IL-4 in vitro and vivo. The study might provide useful information for developing potential therapeutic targets against the disease.

Recombinant CsHscB of carcinogenic liver fluke Clonorchis sinensis induces IL-10 production by binding with TLR2

“…sinensis has evolved complex mechanisms for resistance to immune responses. Zhao et al demonstrated that total protein from C. sinensis inhibited Th1 immune responses by the activation of mannose receptor (MR), but not TLR2 or TLR4 to induce Th2-skewed response [15]. Our previous study showed that during the secretion of ESPs by C. sinensis, TLR4 plays a regulatory role in the induction of type I-relative cytokines (such as IFN-γ, IL-12, IL-6, TNFα) [14].…”

“…Zhao et al demonstrated that total protein from C . sinensis inhibited Th1 immune responses by the activation of mannose receptor (MR), but not TLR2 or TLR4 to induce Th2-skewed response [ 15 ]. Our previous study showed that during the secretion of ESPs by C .…”

“…sinensis , it showed that augment IL-10 was triggered by dendritic cells treated by C . sinensis crude antigen [ 15 , 36 ]. Furthermore, it’s found that IL-10 secreted by lymphocytes from FVB was significantly higher than by those of BALB/c mice, which suggests that IL-10 may contribute to the susceptibility of different strains mice [ 22 , 37 ].…”

“…It is also evident that IL-10 sourced from CD4 + CD25effector T cells impair IFN-γ production for the control of acute inflammation and myositis in the diaphragm caused by Trichinella spiralis as well [34,35]. In respect of C. sinensis, it showed that augment IL-10 was triggered by dendritic cells treated by C. sinensis crude antigen [15,36]. Furthermore, it's found that IL-10 secreted by lymphocytes from FVB was significantly higher than by those of BALB/c mice, which suggests that IL-10 may contribute to the susceptibility of different strains mice [22,37].…”

“…Additionally, chronic infection with this fluke has been shown to cause cholangiocarcinoma (CCA) and C. sinensis is now defined as Group 1 human biological agents (carcinogens) by the International Agency of Research on Cancer (IARC) due to sufficient pieces of evidence in human [12,13]. Previous studies have shown that the components of C. sinensis excretory/secretory products (ESPs) and crude antigen (CA) can potently induce a type 2 or a mix type1/type2 immune responses in vitro [14][15][16]. During the in vivo study of C. sinensis infection, the interaction between worms and host immune cells also potently drives type I immune responses, however, type 2 immune responses become more prevalent after worms are well-developed in susceptible hosts [17].…”