Echinococcus granulosus glycoconjugates induce peritoneal B cell differentiation into antibody-secreting cells and cytokine production

Metabolomics Analysis of Splenic CD19+ B Cells in Mice Chronically Infected With Echinococcus granulosus sensu lato Protoscoleces

Background: The larval stages of Echinococcus granulosus sensu lato (E. granulosus s.l) infection can alter B cell function and affect host anti-infective immunity, but the underlying mechanism remains unclear. The newly emerging immunometabolism highlights that several metabolites are key factors in determining the fate of immune cells, which provides a new insight for exploring how larval E. granulosus s.l. infection remodels B cell function. This study investigated the metabolomic profiles of B cells in mice infected with E. granulosus s.l. protoscoleces (PSC).

Results:Total CD19⁺ B cells, purified from the spleen of infected mice, showed significantly increased production of IL-6, TNF-α, and IL-10 after exposure to LPS in vitro. Moreover, the mRNA expression of metabolism related enzymes in B cells was remarkably disordered post infection. In addition, differential metabolites were identified in B cells after infection. There were 340 differential metabolites (83 upregulated and 257 downregulated metabolites) identified in the positive ion model, and 216 differential metabolites (97 upregulated and 119 downregulated metabolites) identified in the negative ion mode. Among these, 64 differential metabolites were annotated and involved in 68 metabolic pathways, including thyroid hormone synthesis, the metabolic processes of glutathione, fructose, mannose, and glycerophospholipid. Furthermore, several differential metabolites such as glutathione, taurine, and inosine were validated to regulate the cytokine production in LPS stimulated B cells.

Conclusion:Infection with the larval E. granulosus s.l. causes metabolic reprogramming in the intrinsic B cells of mice, which provides the first evidence for understanding the role and mechanism of B cells in parasite anti-infective immunity from the viewpoint of immunometabolism.

The local immune response during Echinococcus granulosus growth in a quantitative hepatic experimental model

The local immune mechanisms responsible for the establishment and development of Echinococcus granulosus sensu stricto infection in the liver, have been little explored. We developed a suitable experimental model that mimics naturally infected livers using portal injection of protoscoleces. Opposite to Echinococcus multilocularis infection which is dose-dependent, fully mature hydatid cysts can be established in the liver whatever the injection dose; although most of the infection sites were seen at the establishment phase as inflammatory granulomas associated with fibrosis, they never matured into cysts. At the establishment phase, a strong immune response was composed of T and B cells, with T1-type, T2-type cells and cytokines and IL-10-secreting CD8⁺ T cells in the liver. At the established phase, results suggested a local production of antibodies by B cells, and an involvement of NK and NKT cells. Infection outcome and local immune response in the liver, were different in the mouse models of Echinococcus granulosus sensu stricto and Echinococcus multilocularis respectively; however, only early specificities at the microenvironment level might explain the major differences found between the lesions induced by the two species. Our quantitative experimental model appears fully appropriate to further study this microenvironment and its relationship with each cestode species.

The excretory-secretory products of Echinococcus granulosus protoscoleces stimulated IL-10 production in B cells via TLR-2 signaling

Background

Excretory-secretory products released by Echinococcus granulosus protoscoleces (EgPSC-ESPs) are well-known to regulate T cell responses. However, their direct influence on the differentiation of B cell subsets remains largely elusive. This study investigated the effects of EgPSC-ESPs on the differentiation of IL-10-producing B cells (B10), and explored the possible role of Toll-like receptor 2 (TLR-2) signaling in this process.

Results

In comparison to phosphate buffered saline (PBS), B cells exposed to the excretory–secretory products (ESPs) generated higher percentages of B10 cells, with higher expression of IL-10 mRNA, and larger amount of IL-10 production, which were in a dose dependent way. The mRNA and protein expression of TLR-2 in the ESPs-stimulated B cells were significantly higher than those in PBS, which was consistent to the results in B cells isolated from EgPSC infected mice. Moreover, TLR-2^−/− B cells in response to ESPs stimulation expressed lower levels of IL-10 mRNA and produced undetectable IL-10 in comparison to those in normal B cells. In addition, Phosphatase and tensin homolog deleted on chromosome ten/AKT/Phosphatidylinositol-3 kinase (PTEN/AKT/PI3K) pathway was activated in ESPs-treated B cells, which was also dependent on TLR-2 signaling. Pam3CSK4, the agonist of TLR-2, could mock the effects of ESPs on the expression of PTEN, AKT and PI3K.

Conclusion

Overall, this study revealed that TLR-2 signaling was required for B10 induction mediated by EgPSC-ESPs, which might be an immunomodulatory target against the parasite infection.

Electronic supplementary material

The online version of this article (10.1186/s12865-018-0267-7) contains supplementary material, which is available to authorized users.

Th1/Th2-type cytokine profile in C57 black mice inoculated with live Echinococcus granulosus protoscolices

BACKGROUND AND OBJECTIVE

Cystic echinococcosis (CE) is a widespread parasitic disease caused by infection with the larval stage of a tapeworm, Echinococcus granulosus. The immune response to hydatid cyst in intermediate hosts is a complex and contradictory issue. It is suggested that a Th2 response would favor the establishment of the parasite, whereas a Th1 response would be lethal for the parasite. Thus, the aim of the present study was to evaluate the levels of IL2, TNFα, and IFNγ as T helper (Th)1-type cytokines, IL4 as a Th2-type cytokine, and total IgG in C57/black mice inoculated with E. granulosus protoscoleces (PSCs).

MATERIALS AND METHOD

In this experimental study, six C57/black mice were intraperitoneally inoculated with live E. granulosus PSCs and a control group consist of six C57/black mice received normal saline. The quantitative concentrations of IL2, TNFα, IFNγ, and IL4 were determined in the first, second, fourth, eighth and 12th-week post inoculation in both case and control groups.

RESULTS

The results showed that at the early post-infection phase (3-4 weeks) the Th1-type cytokine profile was predominant, however the shift to Th2-type cytokine took place in the 4th week.

CONCLUSION

Based on the results of the present study, we can suggest that the shift from Th1 to Th2 reactivity may be associated with persistent of the disease because Th2 reactivity may be less effective than Th1 reactivity in countering the parasite.

Increase of Vascular Endothelial Growth Factor and Decrease of MCP-1 and Some Updated Epidemiology Aspects of Cystic Echinococcosis Human Cases in Calabria Region

We aim to investigate some of the pathogenetic mediators of the human echinococcosis and to obtain updated epidemiological findings on cases of echinococcosis in Calabria, Southern Italy. Echinococcosis diagnosis was based on imaging, serological investigations, and molecular assay. Indeed, real-time PCR indicated the presence of G2/G3 genotypes of Echinococcus granulosus complex. Regarding pathogenesis, a relevant novel tool of immune depression should be deemed the reduced level of serum MCP-1. Also, we found a previously unreported VEGF, possibly associated with neovascularization requested by the parasite cyst metabolism. Cytokine profiles suggest a bias of the immunity toward Th2 and Treg responses. Nitric oxide levels exhibited a significant decrease one week after therapy versus basal level measured before surgery and/or chemotherapy. An increase of serum total IgE class and IgG4 subclass was found in Echinococcus-positive patients versus controls. Our data demonstrated an endemic spreading, at least in the province of Catanzaro and neighboring Calabria territories, for such parasitosis with the novel issue of the number of female overcoming male cases. In conclusion, the novel findings of this study were the increased VEGF and the reduced serum MCP-1 in the studied cases, as well as the number of Echinococcus-infected females overcoming the infected males.

The effect of Echinococcus granulosus on spleen cells and TGF-β expression in the peripheral blood of BALB/c mice

Cystic echinococcosis (CE) caused by the cestode Echinococcus granulosus (E. granulosus) is a zoonotic parasitic disease. The effective immune evasion mechanisms of E. granulosus allow it to parasitize its hosts. However, the status of the innate and adaptive immune cells and their contributions to E. granulosus progression remain poorly understood. In this study, we aimed to determine the impact of E. granulosus infection on T cells, NK cell responses and TGF-β expression during the early infection phase in BALB/c mice. In E. granulosus infections, there was an increasing tendency in the percentage of CD4⁺ CD25⁺ T cells and CD4⁺ Foxp3⁺ T cells and peripheral blood TGF-β levels and relative expression of the Foxp3 gene. Moreover, there were a decreasing tendency in the percentage of NK cells and NK cell cytotoxicity and the expression of NKG2D on NK cells. The TGF-β1/Smad pathway was activated by E. granulosus in mice. Above results can be reversed by the inhibitor SB-525334 (potent activin receptor-like kinase 5 inhibitor). These results suggest that the TGF-β/Smad pathway plays an important role in changes of T-cell or NK cell responses. These results may contribute to revealing the preliminary molecular mechanisms in establishing hydatid infection.

The excretory-secretory products of Echinococcus granulosus protoscoleces directly regulate the differentiation of B10, B17 and Th17 cells

Background

Excretory-secretory products (ESPs) released by helminths are well-known to regulate T cell responses in the host. However, their direct influence in the differentiation of naïve T cells, and especially B cells, remains largely unknown. This study investigated the effects of Echinococcus granulosus protoscoleces ESPs (EgPSC-ESPs) on the differentiation of IL-10-producing B cells (B10), IL-17A-producing B cells (B17) and Th17 cells.

Methods

BALB/c mice injected with EgPSC were used to evaluate the in vivo profiles of B10, B17 and Th17 cells. In vitro purified CD19⁺ B and naïve CD4⁺ T cells were cultured in the presence of native, heat-inactivated or periodate-treated EgPSC-ESPs, and the differentiation of these cell subsets were compared.

Results

In contrast to the control group, infected mice showed higher frequencies of B10, B17 and Th17 cells, and higher levels of IL-10 and IL-17A in the sera. Interestingly, B17 cells were first identified to express CD19⁺CD1d^high. In vitro, B cells cultured with native ESPs exhibited a higher percentage of B10 cells but lower percentage of B17 and Th17 cells compared to the PBS group. Moreover, the relative expression of IL-10 and IL-17A mRNA were consistent with the altered frequencies. However, ESPs subjected to heat-inactivation or periodate treatment exhibited an inverse effect on the induction of these cell subsets.

Conclusions

Our findings indicate that ESPs released by EgPSC can directly regulate the differentiation of B10, B17 and Th17 cells, which appear to be heat-labile and carbohydrate-dependent.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2263-9) contains supplementary material, which is available to authorized users.

Parasite molecules and host responses in cystic echinococcosis

Cystic echinococcosis is the infection by the larvae of cestode parasites belonging to the Echinococcus granulosus sensu lato species complex. Local host responses are strikingly subdued in relation to the size and persistence of these larvae, which develop within mammalian organs as 'hydatid cysts' measuring up to tens of cm in diameter. In a context in which helminth-derived immune-suppressive, as well as Th2-inducing, molecules garner much interest, knowledge on the interactions between E. granulosus molecules and the immune system lags behind. Here, we discuss what is known and what are the open questions on E. granulosus molecules and structures interacting with the innate and adaptive immune systems, potentially or in demonstrated form. We attempt a global biological approach on molecules that have been given consideration primarily as protective (Eg95) or diagnostic antigens (antigen B, antigen 5). We integrate glycobiological information, which traverses the discussions on antigen 5, the mucin-based protective laminated layer and immunologically active preparations from protoscoleces. We also highlight some less well-known molecules that appear as promising candidates to possess immune-regulatory activities. Finally, we point out gaps in the molecular-level knowledge of this infectious agent that hinder our understanding of its immunology.

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.

Immunogenetics of human echinococcosis

Susceptibility and resistance to human Echinococcus infection and disease, although poorly understood, appear to reflect a complex interaction of parasite and host immunological and genetic factors. Disease stage, progression, and prognosis following treatment appear to be strongly influenced by cytokine and antibody profiles, and more recent evidence has suggested an important role of dendritic cells (DCs) and T regulatory cells (Tregs) in immunomodulation. Microarrays have supported these findings, highlighting both known and novel pathways involved in chronic murine disease. Genetic studies to date have been few and with limited success. Advanced genomic approaches, such as genome-wide association studies (GWAS), may provide further insight to identify the relevant pathways involved, thereby facilitating a new approach for the development of new clinical therapies.