Immunomodulation of the hepatic egg granuloma in Schistosoma japonicum-infected pigs

Vaccination against the HDL receptor of S. japonicum inhibits egg embryonation and prevents fatal hepatic complication in rabbit model

BACKGROUND

Schistosomiasis is one of the most important neglected tropical infectious diseases to overcome and the primary cause of its pathogenesis is ectopic maturation of the parasite eggs. Uptake of cholesteryl ester from the host high-density lipoprotein (HDL) is a key in this process in Schistosoma japonicum and CD36-related protein (CD36RP) has been identified as the receptor for this reaction. Antibody against the extracellular domain of CD36RP (Ex160) efficiently blocked the HDL cholesteryl ester uptake and the egg embryonation in vitro. However, whether Ex160 immunization could efficiently raise proper antibody responses to sufficiently block HDL cholesteryl ester uptake and the egg embryonation to protect host in vivo is very interesting but unknown.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, rabbits were immunized with the recombinant Ex160 peptide (rEx160) to evaluate its anti-pathogenic vaccine potential. Immunization with rEx160 induced consistent anti-Ex160 IgG antibody and significant reduction in development of the liver granulomatosis lesions associated with suppressed intrahepatic maturation of the schistosome eggs. The immunization with rEx160 rescued reduction of serum HDL by the infection without changing its size distribution, being consistent with interference of the HDL lipid uptake by the parasites or their eggs by antibody against Ex160 in in vitro culture.

CONCLUSIONS/SIGNIFICANCE

The results demonstrated that vaccination strategy against nutritional supply pathway of the parasite is effective for reducing its pathogenesis.

Glycomic Analysis of Life Stages of the Human Parasite Schistosoma mansoni Reveals Developmental Expression Profiles of Functional and Antigenic Glycan Motifs

Glycans present on glycoproteins and glycolipids of the major human parasite Schistosoma mansoni induce innate as well as adaptive immune responses in the host. To be able to study the molecular characteristics of schistosome infections it is therefore required to determine the expression profiles of glycans and antigenic glycan-motifs during a range of critical stages of the complex schistosome lifecycle. We performed a longitudinal profiling study covering schistosome glycosylation throughout worm- and egg-development using a mass spectrometry-based glycomics approach. Our study revealed that during worm development N-glycans with Galβ1–4(Fucα1–3)GlcNAc (LeX) and core-xylose motifs were rapidly lost after cercariae to schistosomula transformation, whereas GalNAcβ1–4GlcNAc (LDN)-motifs gradually became abundant and predominated in adult worms. LeX-motifs were present on glycolipids up to 2 weeks of schistosomula development, whereas glycolipids with mono- and multifucosylated LDN-motifs remained present up to the adult worm stage. In contrast, expression of complex O-glycans diminished to undetectable levels within days after transformation. During egg development, a rich diversity of N-glycans with fucosylated motifs was expressed, but with α3-core fucose and a high degree of multifucosylated antennae only in mature eggs and miracidia. N-glycan antennae were exclusively LDN-based in miracidia. O-glycans in the mature eggs were also diverse and contained LeX- and multifucosylated LDN, but none of these were associated with miracidia in which we detected only the Galβ1–3(Galβ1–6)GalNAc core glycan. Immature eggs also exhibited short O-glycan core structures only, suggesting that complex fucosylated O-glycans of schistosome eggs are derived primarily from glycoproteins produced by the subshell envelope in the developed egg. Lipid glycans with multifucosylated GlcNAc repeats were present throughout egg development, but with the longer highly fucosylated stretches enriched in mature eggs and miracidia. This global analysis of the developing schistosome's glycome provides new insights into how stage-specifically expressed glycans may contribute to different aspects of schistosome-host interactions.

Immune response of γδT cells in Schistosome japonicum-infected C57BL/6 mouse liver

Systematic evaluation of the role of γδT cells during the Schistosoma japonicum infection has not been reported, despite the fact that γδT cells contribute to many infectious diseases in innate immunity. Therefore, the aim of this study was to observe the properties of γδT cells in the liver of C57BL/6 mice infected by S. japonicum. In this report, using immuno-fluorescent histological analysis, γδT cells were found around hepatic granulomatous. Moreover, the flow cytometry results revealed that the percentage of hepatic γδT cells increased significantly after S. japonicum infection. More interestingly, a subset of CD3(-)γδTCR(+) cells were found and markedly increased after infection. Furthermore, expression of activation markers (CD25 and CD69) and cytokine profiles were detected in these hepatic CD3(+)γδTCR(+) and CD3(-)γδTCR(+) cells. The significantly higher level of CD69, IL-4 and IL-17 were observed in CD3(+)γδTCR(+) cells after infection, suggesting that CD3(+)γδTCR(+) cells instead of CD3(-)γδTCR(+) cells might play a predominant role during the infection. Finally, our results indicated that the expression of NKG2D on CD3(+)γδTCR(+) cells was higher than that on CD3(-)γδTCR(+) cells. Collectively, γδT cells could play an important role in the liver of C57BL/6 mouse during japonicum infection.

Exogenous bone morphogenetic protein-7 reduces hepatic fibrosis in Schistosoma japonicum-infected mice via transforming growth factor-β/Smad signaling

AIM: To investigate the antifibrotic effects of bone morphogenetic protein-7 (BMP-7) on Schistosoma japonicum (S. japonicum)-induced hepatic fibrosis in BALB/C mice.

METHODS: Sixty BALB/C mice were randomly divided into three groups, including a control group (group A, n = 20), model group (group B, n = 20) and BMP-7 treated group (group C, n = 20). The mice in group B and group C were abdominally infected with S. japonicum cercariae to induce a schistosomal hepatic fibrosis model. The mice in group C were administered human recombinant BMP-7. Liver samples were extracted from mice sacrificed at 9 and 15 wk after modeling. Hepatic histopathological changes were assessed using Masson’s staining. Transforming growth factor-beta 1 (TGF-β1), alpha-smooth muscle actin (α-SMA), phosphorylated Smad2/3 (pSmad2/3) and Smad7 protein levels and localization were measured by Western blotting and immunohistochemistry, respectively, and their mRNA expressions were detected by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS: The schistosomal hepatic fibrosis mouse model was successfully established, as the livers of mice in group B and group C showed varying degrees of typical schistosomal hepatopathologic changes such as egg granuloma and collagen deposition. The degree of collagen deposition in group C was higher than that in group A (week 9: 22.95 ± 6.66 vs 2.02 ± 0.76; week 15: 12.84 ± 4.36 vs 1.74 ± 0.80; P < 0.05), but significantly lower than that in group B (week 9: 22.95 ± 6.66 vs 34.43 ± 6.96; week 15: 12.84 ± 4.36 vs 18.90 ± 5.07; P < 0.05) at both time points. According to immunohistochemistry data, the expressions of α-SMA, TGF-β1 and pSmad2/3 protein in group C were higher than those in group A (α-SMA: week 9: 21.24 ± 5.73 vs 0.33 ± 0.20; week 15: 12.42 ± 4.88 vs 0.34 ± 0.27; TGF-β1: week 9: 37.00 ± 13.74 vs 3.73 ± 2.14; week 15: 16.71 ± 9.80 vs 3.08 ± 2.35; pSmad2/3: week 9: 12.92 ± 4.81 vs 0.83 ± 0.48; week 15: 7.87 ± 4.09 vs 0.90 ± 0.45; P < 0.05), but significantly lower than those in group B (α-SMA: week 9: 21.24 ± 5.73 vs 34.39 ± 5.74; week 15: 12.42 ± 4.88 vs 25.90 ± 7.01; TGF-β1: week 9: 37.00 ± 13.74 vs 55.66 ± 14.88; week 15: 16.71 ± 9.80 vs 37.10 ± 12.51; pSmad2/3: week 9: 12.92 ± 4.81 vs 19.41 ± 6.87; week 15: 7.87 ± 4.09 vs 13.00 ± 4.98; P < 0.05) at both time points; the expression of Smad7 protein in group B was higher than that in group A and group C at week 9 (8.46 ± 3.95 vs 1.00 ± 0.40 and 8.46 ± 3.95 vs 0.77 ± 0.42; P < 0.05), while there were no differences in Smad7 expression between the three groups at week 15 (1.09 ± 0.38 vs 0.97 ± 0.42 vs 0.89 ± 0.39; P > 0.05). Although minor discrepancies were observed, the results of RT-PCR and Western blotting were mainly consistent with the immunohistochemical results.

CONCLUSION: Exogenous BMP-7 significantly decreased the degree of hepatic fibrosis in both the acute and chronic stages of hepato-schistosomiasis, and the regulatory mechanism may involve the TGF-β/Smad signaling pathway.

Study of the activity of 3-benzyl-5-(4-chloro-arylazo)-4-thioxo-imidazolidin-2-one against Schistosomiasis mansoni in mice

Previous studies conducted with the imidazolidinic derivative 3-benzyl-5-(4-chloro-arylazo)-4-thioxo-imidazolidin-2-one (LPSF-PT05) show outstanding activity against adult Schistosoma mansoni worms in vitro. In the first phase of this study, S. mansoni-infected mice were treated, orally, with 100 mg/Kg of the LPSF-PT05 in three formulations: Tween 80 and saline solution, oil/water (70 : 30) emulsion, and solid dispersion with polyethylene glycol (PEG). In the second phase, three other doses of the LPSF-PT05 in PEG were tested: 3, 10, 30 mg/kg. These treatment regimens significantly reduced the number of recovered worms due to increases in the solubility of the compound in this formulation; the greatest reduction (70.5%) was observed at the dose of 100 mg/kg. There was no changes in the pattern of mature egg compared to immature eggs; however there was a significant increase in the number of dead eggs. Histopathological analysis of liver tissue showed changes in morphological aspects of the hepatic parenchyma with decrease exudative-productive hepatic granuloma stages, although we found no significant differences in IFN-γ, IL-4, IL-10, or NO production in response to the specific antigen SEA. The results show the derivative LPSF-PT05 to be a potential candidate in the etiological treatment of schistosomiasis with a possible dampening effect of the granulomatous process.

Immunopathogenesis of human schistosomiasis

Schistosomiasis continues to be a significant cause of parasitic morbidity and mortality worldwide. This review considers the basic features of the pathology and clinical outcomes of hepatointestinal and genitourinary schistosomiasis, presents an overview of the numerous studies on animal models that have clarified many of the immunopathological features, and provides insight into our current understanding of the immunopathogenesis and genetic control of human schistosomiasis. In murine schistosomiasis, pathology is induced by a CD4(+) Th2 driven granulomatous response directed against schistosome eggs lodged in the host liver. The Th2 cytokines IL-4 and IL-13 drive this response, whereas IL-10, IL13Ralpha2, IFN-gamma and a subset of regulatory T-cells act to limit schistosome induced pathology. A variety of cell types including hepatic stellate cells, alternatively activated macrophages and regulatory T-cells have also been implicated in the pathogenesis of schistosomiasis. Current knowledge suggests the immunopathogenic mechanisms underlying human schistosomiasis are likely to be similar. The review also considers the future development of anti-pathology schistosome vaccines. As fibrosis is an important feature of many other diseases such as Crohn's disease and sarcoidosis, a comprehensive understanding of the cellular and molecular mechanisms involved in schistosomiasis may also ultimately contribute to the development an effective disease intervention strategy for other granulofibrotic diseases.