TGF-β/Smad signaling pathway regulates Th17/Treg balance during Echinococcus multilocularis infection

Yin and yang of interleukin-17 in host immunity to infection

The interleukin-17 (IL-17) family cytokines, such as IL-17A and IL-17F, play important protective roles in host immune response to a variety of infections such as bacterial, fungal, parasitic, and viral. The IL-17R signaling and downstream pathways mediate induction of proinflammatory molecules which participate in control of these pathogens. However, the production of IL-17 can also mediate pathology and inflammation associated with infections. In this review, we will discuss the yin-and-yang roles of IL-17 in host immunity to pathogens.

Chinese 1 strain of Toxoplasma gondii excreted-secreted antigens negatively modulate Foxp3 via inhibition of the TGFßRII/Smad2/Smad3/Smad4 pathway

Toxoplasma gondii is an opportunistic intracellular parasite and is considered an important aetiological factor in the process of abortion, especially as occurs in early gestation. Chinese 1 strain of T. gondii is a dominant genotype prevalent in China. Although it is known that early foetal resorption triggered by RH strain of T. gondii is attributable to immune mechanisms rather than its direct effect in uterus, the underlying mechanism of the abortion caused by Chinese 1 strain remains unclear. This study was designed to investigate the effect of excreted–secreted antigens (ESA) of Chinese 1 strain of T. gondii on the expression of forkhead box transcription factor (Foxp3) as it pertains to early pregnancy and abortion. ESA caused a marked inhibition in the expression of Foxp3 both in vivo and in vitro. In addition, ESA negatively modulated Smad2 and Smad3 at the posttranslational level. Smad2 siRNA cooperated with ESA to further suppress the level of Foxp3. This inhibitory effect on Foxp3 expression was partially abrogated by overexpression of Smad2, Smad3 and Smad4. Additionally, ESA attenuated the expression of TGFßRII, whereas TGFßRII agonist could profoundly reversed the decreased Foxp3 triggered by ESA. Collectively, the findings suggested that ESA restricted Foxp3 expression by inhibiting TGFßRII/Smad2/Smad3/Smad4 signalling, ultimately resulting in abortion.

Laboratory Diagnosis of Echinococcus spp. in Human Patients and Infected Animals

Among the species composing the genus Echinococcus, four species are of human clinical interest. The most prevalent species are Echinococcus granulosus and Echinococcus multilocularis, followed by Echinococcus vogeli and Echinococcus oligarthrus. The first two species cause cystic echinococcosis (CE) and alveolar echinococcosis (AE) respectively. Both diseases have a complex clinical management, in which laboratory diagnosis could be an adjunctive to the imaging techniques. To date, several approaches have been described for the laboratory diagnosis and followup of CE and AE, including antibody, antigen and cytokine detection. All of these approaches are far from being optimal as adjunctive diagnosis particularly for CE, since they do not reach enough sensitivity and/or specificity. A combination of several methods (e.g., antibody and antigen detection) or of several (recombinant) antigens could improve the performance of the adjunctive laboratory methods, although the complexity of echinococcosis and heterogeneity of clinical cases make necessary a deep understanding of the host-parasite relationships and the parasite phenotype at different developmental stages to reach the best diagnostic tool and to make it accepted in clinical practice. Standardization approaches and a deep understanding of the performance of each of the available antigens in the diagnosis of echinococcosis for the different clinical pictures are also needed. The detection of the parasite in definitive hosts is also reviewed in this chapter. Finally, the different methods for the detection of parasite DNA in different analytes and matrices are also reviewed.

Regulation of immunity by Taeniids: lessons from animal models and in vitro studies

Taeniidae is the largest family of the Cyclophyllidea order of parasites despite being composed of just two genera: Taenia spp and Echinococcus spp. These parasites are flatworms with a terrestrial life cycle, having an immature or larval stage called metacestode, which develops into the mature form within the intestine of the primary host after being consumed in raw or poorly cooked meat. Consumed eggs hatch into oncospheres, penetrate the intestinal walls and are transported via the bloodstream to later develop into metacestodes within the muscles and internal organs of secondary and sometimes primary hosts, thereby initiating the cycle again. Larval stages of both Taenia spp and Echinococcus spp are well known to produce tissue-dwelling, long-lasting infections; in this stage, these parasites can reach centimetres (macroparasites) and both genera may cause life-threatening diseases in humans. Establishing such long-term infections requires an exceptional ability to modulate host immunity for long periods of time. In this review, we analyse the immunoregulatory mechanisms induced by these tapeworms and their products, mainly discussing the importance of taeniid strategies to successfully colonize their hosts, such as antigen-presenting cell phenotype manipulation and the consequent induction of T-cell anergy, among others.

Role of immune tolerance in BALB/c mice with anaphylactic shock after Echinococcus granulosus infection

This study tested the hypothesis that immune tolerance mediated by regulatory T (Treg) cells is protective against cystic echinococcosis (CE)-induced anaphylactic shock. BALB/c mice were inoculated with protoscoleces of Echinococcus granulosus. After 3 months, the presence of cysts in the peritoneal cavity was confirmed after which a subset of mice was sensitized using a cyst fluid suspension to induce anaphylactic shock. While IgE levels were significantly higher in both groups inoculated with E. granulosus as compared to the healthy control group (both P < 0.01), sensitized mice had higher IgE levels as compared with those with E. granulosus alone (P < 0.05). Mice inoculated with E. granulosus alone and sensitized mice both had significantly higher histamine levels as compared to the healthy controls. The proportion of CD4(+)CD25(+)Foxp3(+) Treg cells relative to CD4(+) cells was significantly higher in mice inoculated with E. granulosus alone (P < 0.0167); significantly higher interleukin-10 (IL-10) and tumor growth factor-β (TGF-β1) levels were also noted in this group (all P < 0.01). In contrast, IL-13 and IL-17A levels were significantly higher in the sensitized mice (both P < 0.05). Taken together, these data suggest that the biphasic changes in Treg cell and cytokine levels may be associated with anaphylactic shock induced by CE.

Emerging roles of T helper 17 and regulatory T cells in lung cancer progression and metastasis

Lung cancer is a leading cause of cancer-related deaths worldwide. Lung cancer risk factors, including smoking and exposure to environmental carcinogens, have been linked to chronic inflammation. An integral feature of inflammation is the activation, expansion and infiltration of diverse immune cell types, including CD4⁺ T cells. Within this T cell subset are immunosuppressive regulatory T (Treg) cells and pro-inflammatory T helper 17 (Th17) cells that act in a fine balance to regulate appropriate adaptive immune responses.In the context of lung cancer, evidence suggests that Tregs promote metastasis and metastatic tumor foci development. Additionally, Th17 cells have been shown to be an integral component of the inflammatory milieu in the tumor microenvironment, and potentially involved in promoting distinct lung tumor phenotypes. Studies have shown that the composition of Tregs and Th17 cells are altered in the tumor microenvironment, and that these two CD4⁺ T cell subsets play active roles in promoting lung cancer progression and metastasis.We review current knowledge on the influence of Treg and Th17 cells on lung cancer tumorigenesis, progression, metastasis and prognosis. Furthermore, we discuss the potential biological and clinical implications of the balance among Treg/Th17 cells in the context of the lung tumor microenvironment and highlight the potential prognostic function and relationship to metastasis in lung cancer.

Immunology of Alveolar and Cystic Echinococcosis (AE and CE)

Cystic and alveolar echinococcosis are severe chronic helminthic diseases caused by the cystic growth or the intrahepatic tumour-like growth of the metacestode of Echinococcus granulosus or Echinococcus multilocularis, respectively. Both parasites have evolved sophisticated strategies to escape host immune responses, mainly by manipulating and directing this immune response towards anergy and/or tolerance. Recent research studies have revealed a number of respective immunoregulatory mechanisms related to macrophages and dendritic cell as well as T cell activities (regulatory T cells, Tregs). A better understanding of this complex parasite-host relationship, and the elucidation of specific crucial events that lead to disease, represents targets towards the development of novel treatment strategies and options.

Potential Effects of Interleukins on the Pathogenesis of Systemic Onset Juvenile Idiopathic Arthritis

BACKGROUND

To analyze the correlation of cytokines with clinical inflammatory indexes in systemic onset juvenile idiopathic arthritis (SOJIA).

METHODS

A total of 30 active SOJIAs, 30 remission SOJIAs, and 20 normal controls were enrolled. The clinical inflammatory indexes such as tender joints counts, swelling joints counts, C-reactive protein, erythrocyte sedimentation rate, visual analogue scale (VAS), and disease activity score 28 (DAS28) were detected. The serum cytokines interleukin (IL)-17, IL-6, IL-21, interferon (IFN)-γ, and IL-4 levels were determined with enzyme-linked immunosorbent assay method. The correlation coefficients between these cytokines and two clinical indexes (VAS and DAS28) in the active SOJIA group were calculated with the Spearman's method.

RESULTS

The serum IL-17 and IL-6 levels in active SOJIA group were significantly increased compared with those in the remission SOJIA group and control group (p < 0.05), and the serum IL-21, IFN-γ, and IL-4 levels showed no obvious difference. In the active SOJIA group, the Spearman coefficients between IL-17 and DAS28, IL-17 and IL-6, IL-6 and DAS28, and between IL-17 and VAS were 0.686 (p = 0.000), 0.833 (p = 0.000), 0.633 (p = 0.000), and 0.524 (p = 0.003), respectively. There was no correlation between cytokines of IL-21, IFN-γ, and IL-4 and the clinical indexes of DAS28 and VAS. Furthermore, in the other two groups, none of the five cytokines exhibited an association with DAS28 or VAS.

CONCLUSION

IL-6 and IL-17 were significantly correlated with DAS28 and VAS, and they might be considered as therapeutic targets for the treatment of SOJIA.

The Dynamics of Treg/Th17 and the Imbalance of Treg/Th17 in Clonorchis sinensis-Infected Mice

Clonorchiasis, caused by the liver fluke Clonorchis sinensis, is a chronic parasitic infection regulated by T cell subsets. An imbalance of CD4⁺CD25⁺ Foxp3⁺regulatory T (Treg) and interleukin (IL)-17-secreting T cells (Th17) may control inflammation and play an important role in the pathogenesis of immune evasion. In the present study, we assessed the dynamics of Treg/Th17 and determined whether the Treg/Th17 ratio is altered in C. sinensis-infected mice. The results showed that the percentages of splenic Treg cells in CD4⁺ T cells were suppressed on day 14 post-infection (PI) but increased on day 56 PI, while Th17 cells were increased on day 56 PI compared with normal control (NC) mice. The Treg/Th17 ratio steadily increased from day 28 to day 56 PI. The hepatic levels of their specific transcription factors (Foxp3 for Treg and RORγt for Th17) were increased in C. sinensis-infected mice from day 14 to 56 PI, and significantly higher than those in NC mice. Meanwhile, serum levels of IL-2 and IL-17 were profoundly increased in C. sinensis-infected mice throughout the experiment; while the concentrations of IL-6 and transforming growth factor β₁ (TGF-β₁) peaked on day 14 PI, but then decreased on day 28 and 56 PI. Our results provide the first evidence of an increased Treg/Th17 ratio in C. sinensis-infected mice, suggesting that a Treg/Th17 imbalance may play a role in disease outcomes of clonorchiasis.

Expression of Toll-Like Receptors 2 and 4 and Related Cytokines in Patients with Hepatic Cystic and Alveolar Echinococcosis

Several studies have demonstrated the important role of Toll-like receptors in various parasitic infections. This study aims to explore expression of Toll-like receptors (TLRs) and related cytokines in patients with human cystic echinococcosis (CE) and alveolar echinococcosis (AE). 78 subjects including AE group (N = 28), CE group (N = 22), and healthy controls (HC, N = 28) were enrolled in this study. The mRNA expression levels of TLR2 and TLR4 in blood and hepatic tissue and plasma levels related cytokines were detected by using ELISA. Median levels of TLR2 mRNA in AE and CE groups were significantly elevated as compared with that in healthy control group. Median levels of TLR4 expression were increased in AE and CE. Plasma concentration levels of IL-5, IL-6, and IL-10 were slightly increased in AE and CE groups compared with those in HC group with no statistical differences (p > 0.05). The IL-23 concentration levels were significantly higher in AE and CE groups than that in HC subjects with statistical significance. The increased expression of TLR2 and IL-23 might play a potential role in modulating tissue infiltrative growth of the parasite and its persistence in the human host.

CCR7(lo)PD-1(hi) CXCR5(+) CD4(+) T cells are positively correlated with levels of IL-21 in active and transitional cystic echinococcosis patients

Background

In our study, we investigated whether circulating T follicular helper (Tfh) and the related cytokines are involved in human cystic echinococcosis (CE).

Methods

A total of 64 patients with CE and 30 healthy controls were enrolled in this study. Percentages of CCR7^loPD-1^hi cells within CXCR5⁺ CD4⁺ T cells (circulating Tfh cells) were detected by flow cytometry. Levels of IL-21 and IL-4 in peripheral blood were detected by cytometric bead array. The mRNA expression of IL-21, IL-4, Bcl-6, and Blimp-1 in peripheral blood mononuclear cells (PBMCs) were measured by real-time PCR. Levels of IgG1, IgG2, IgG3, and IgG4 in the patients’ sera were measured using enzyme-linked immunosorbent assay.

Results

Percentages of circulating Tfh cells were significantly increased in the CE1, CE2, and CE3 groups (p < 0.05). The concentrations of IL-21 and IL-4 in the serum were significantly increased in CE1, CE2, and CE3 groups (p < 0.05). IL-21 was positively correlated with circulating Tfh cells in CE3 group (r = 0.779, p < 0.05). The mRNA levels of IL-21, IL-4, and Bcl-6 were increased in CE1, CE2, and CE3 groups. Levels of IgG1 and IgG4 in patients’ sera were increased in CE1, CE2, and CE3 groups. Levels of IgG2 and IgG3 were increased in CE4-5 group. Additionally, after stimulation with hydatid fluid in vitro, the levels of circulating Tfh cells, IL-21 and IL-4 in PBMCs isolated from CE patients were significantly increased (p < 0.05).

Conclusions

The levels of circulating Tfh and related cytokines were significantly increased in CE patients, suggesting that they are involved in human CE.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-015-1156-9) contains supplementary material, which is available to authorized users.

Susceptibility versus resistance in alveolar echinococcosis (larval infection with Echinococcus multilocularis)

Epidemiological studies have demonstrated that the majority of human individuals exposed to infection with Echinococcus spp. eggs exhibit resistance to disease as shown by either seroconversion to parasite--specific antigens, and/or the presence of 'dying out' or 'aborted' metacestodes, not including hereby those individuals who putatively got infected but did not seroconvert and who subsequently allowed no development of the pathogen. For those individuals where infection leads to disease, the developing parasite is partially controlled by host immunity. In infected humans, the type of immune response developed by the host accounts for the subsequent trichotomy concerning the parasite development: (i) seroconversion proving infection, but lack of any hepatic lesion indicating the failure of the parasite to establish and further develop within the liver; or resistance as shown by the presence of fully calcified lesions; (ii) controlled susceptibility as found in the "conventional" alveolar echinococcosis (AE) patients who experience clinical signs and symptoms approximately 5-15 years after infection, and (iii) uncontrolled hyperproliferation of the metacestode due to an impaired immune response (AIDS or other immunodeficiencies). Immunomodulation of host immunity toward anergy seems to be triggered by parasite metabolites. Beside immunomodulating IL-10, TGFβ-driven regulatory T cells have been shown to play a crucial role in the parasite-modulated progressive course of AE. A novel CD4+CD25+ Treg effector molecule FGL2 recently yielded new insight into the tolerance process in Echinococcus multilocularis infection.

Upregulation of PD-1 on CD4⁺CD25⁺ T cells is associated with immunosuppression in liver of mice infected with Echinococcus multilocularis

Alveolar echinococcosis is a zoonotic disease caused by Echinococcus multilocularis (E. multilocularis) infection. The relationship between PD-1/PD-L1 pathway and Tregs at different stages of E. multilocularis infection has rarely been reported. This study aims to investigate the role of PD-1/PD-L1 in immunosuppression of Tregs in E. multilocularis infection. Hematoxylin-eosin staining, flow cytometry, immunohistochemistry, quantitative RT-PCR analysis, cytometric bead array and MTT assay were used to analyze liver pathological changes, percentages of PD-1(+) Tregs and PD-L1(+) dendritic cells (DCs), expression levels of PD-1, PD-L1 and Foxp3, levels of interleukin-10 (IL-10) and transforming growth factor beta (TGF-β) and proliferation of lymphocytes. During middle-late stage (day 30 to day 330) the percentages of PD-1(+) Tregs and PD-L1(+) DCs together with levels of Foxp3, IL-10 and TGF-β increased significantly and maintained at high level. The expression of PD-1 and PD-L1 was increased with the enlarging erosion of E. multilocularis, and was mainly distributed in hepatic sinus, fibrous wall of alveolar hydatid and germinal layer around foci of infection. PD-1/PD-L1 promoted the secretion of IL-10 and TGF-β. Our results indicate that engagement of the PD-1 and PD-L1 correlates with inhibition of T-cell effector function, cytokine secretion and proliferation. High expression of PD-1/PD-L1 may play an important role in stimulating CD4(+)CD25(+) T cells, and maintaining peripheral tolerance and immune evasion during chronic infection of E. multilocularis.

Protective effect of platycodin D on liver injury in alloxan-induced diabetic mice via regulation of Treg/Th17 balance

Platycodin D is a major pharmacological constituent of Platycodi Radix with immunomodulatory activity. The present study was designed to investigate how platycodin D (PLD) reveals liver injury in diabetic mice and its mechanism. Fifty mice were divided into five groups randomly: control group, model group, rosiglitazone (ROG, 10 mg/kg) group, PLD (50 mg/kg) group, and PLD (100 mg/kg) group. Diabetes was induced with the injection of alloxan monohydrate (150 mg/kg) subcutaneously, and animals with blood glucose level of ≥250 mg/dl were considered as diabetic mice. After the first day of diabetes induction, the treatments were performed for 8 weeks. Then the animals were anaesthetized, and blood and liver samples were also collected for further assay. PLD significantly decreased the serum levels of glucose, insulin, interleukin-6 (IL-6), interleukin-1β, tumor necrosis factor-α (TNF-α), and interleukin (IL)-17A and increased IL-10 level in serum. PLD effectively downregulated aspartate transaminase (AST), alanine aminotransferase (ALT), total cholesterol (TC), and triglycerides (TG) in liver. PLD also attenuated liver histological change. In addition, PLD significantly attenuated IL-17A and IL-10 levels in vitro, flow cytometry (FCM) studies also showed that PLD remarkably inhibited Th17 cells and significantly increased Treg cells in liver tissues and spleen cells. Western blot demonstrated PLD inhibited the phosphorylation of JAK and STAT-3 and the expression of RORγt and increased the expression of Foxp3. The findings showed that PLD exerts beneficial effects on alloxan-induced liver injury in mice.

Ganoderma lucidum polysaccharide extract inhibits hepatocellular carcinoma growth by downregulating regulatory T cells accumulation and function by inducing microRNA-125b

Background

Ganoderma lucidum polysaccharides (GLPS) have been used as traditional Chinese medicine for their properties of cancer prevention and immunomodulation. However, it is unclear whether GLPS has therapeutic effect on anti-hepatocellular carcinoma (HCC) in vivo. In this study, the effect of GLPS and their impact on the balance of regulatory T cell (Treg) and effector T cell (Teff) was measured in a model of hepatoma-bearing mice.

Methods

The effect of GLPS and their impact on the balance of regulatory T cell (Treg) and effector T cell (Teff) were measured in a model of hepatoma-bearing mice. Real-time PCR detected the levels of MicroRNAs (miRNAs) and mRNA. The effects of Tregs on Teff proliferation were determined via suppression assay. The mircroRNA-125b (miR-125b) inhibitor was used to down-regulate miR-125b expression.

Results

GLPS significantly suppressed tumor growth in hepatoma-bearing mice associated with an increase of the ratio of Teffs to Tregs. Moreover, GLPS eliminate Treg suppression of Teff proliferation with an increase in IL-2 secretion. Addition of GLPS to treat T cells inhibited Notch1 and FoxP3 expression through increase of miR-125b expression. In hepatoma-bearing mice, miR-125b inhibitor obviously abolished the effect of GLPS on tumor growth.

Conclusions

This finding provides the novel evidence for GLPS on inhibition of HCC through miR-125b inhibiting Tregs accumulation and function.

Investigating the impact of Echinococcus multilocularis vesicular fluid on human cells from healthy blood donors

CONTEXT AND OBJECTIVES

Alveolar echinococcosis (AE) is a severe chronic helminthic disease that mimics slow-growing liver cancer. Previous studies using murine models suggest that Echinococcus multilocularis (Em) metacestodes have developed mechanisms which impair the natural inflammatory host response. The aim of this study was to investigate in vitro the impact of Em vesicular fluid (VF) on monocytes, monocytes derived dendritic cells and lymphocytes from healthy blood donors.

METHODS

First, assays were performed to investigate whether or not Em-VF influences monocyte-derived dendritic cell (MoDC) differentiation and maturation. Monocytes during differentiation and immature MoDCs were exposed to Em-VF. The effect of Em-VF was assessed using flow cytometry (CD86, CD83, CD80) and immune assays (IL-10 and TGFβ). Second, assays were performed to investigate the interaction between Em-VF, peripheral blood monocyte cells (PBMC) and Toll-like Receptor (TLR) agonists (LPS, PolyIC, R848 and CpG). PBMC were stimulated by each of the TLR agonists with and without Em-VF. The subsequent TGFβ production was assessed.

RESULTS

Exposure to Em-VF had bearing on both differentiation and maturation of MoDC, but only partially. A decrease in the expression of co-stimulatory molecules was observed; however, levels of immune-regulatory cytokines were stable. PBMC exposed simultaneously to Em-VF and LPS induced a significant increase of TGFβ (p<0.05, Wilcoxon signed-rank test). Further experiments showed that TGFβ production was lymphocyte-dependent.

CONCLUSION

The assays performed confirmed that Em-VF influences the host immune response. However, only minor changes were observed when investigating the Em-VF impact on cells from healthy blood donors. Assays with TLR agonists suggested that co-stimulation with LPS reinforces the response of healthy blood donors exposed to Em-VF.