Laura Cervi

Potential role for excretory–secretory forms of glutathione-S-transferase (GST) in Fasciola hepatica

The excretory-secretory antigen of Fasciola hepatica (ESA) is involved in the suppressive phenomena of cellular immune responses in rats. The ESA can depress the proliferative response of spleen mononuclear cells and inhibit nitric oxide (NO) production by peritoneal cells. In the present study we identified ESA proteins of ca 24 kDa, which shared significant sequence homology to glutathione-S-transferase (GST) obtained from homogenates of F. hepatica adults, other helminths and different mammals. When the dimeric form of these proteins ca 48 kDa was cultured with rat spleen cells, a significant decrease of proliferative response to Con A was detected, starting from 20 micrograms/ml of ESA protein (P < 0.03). We also observed a significant inhibition of nitrite production by incubation with the dimeric form in normal peritoneal macrophages (P < 0.04). These results indicated that the GST secreted by the parasite could be involved in evasion of the parasite from the host immune response.

Control of dendritic cell maturation and function by triiodothyronine

Accumulating evidence indicates a functional crosstalk between immune and endocrine mechanisms in the modulation of innate and adaptive immunity. However, the impact of thyroid hormones (THs) in the initiation of adaptive immune responses has not yet been examined. Here we investigated the presence of thyroid hormone receptors (TRs) and the impact of THs in the physiology of mouse dendritic cells (DCs), specialized antigen‐presenting cells with the unique capacity to fully activate naive T cells and orchestrate adaptive immunity. Both immature and lipopolysaccharide‐matured bone marrow‐derived DCs expressed TRs at mRNA and protein levels, showing a preferential cytoplasmic localization. Remarkably, physiological levels of triiodothyronine (T3) stimulated the expression of DC maturation markers (major histocompatability complex II, CD80, CD86, and CD40), markedly in‐creased the secretion of interleukin‐12, and stimulated the ability of DCs to induce naive T cell proliferation and IFN‐γ production in allogeneic T cell cultures. Analysis of the mechanisms involved in these effects revealed the ability of T3 to influence the cytoplasmic‐nuclear shuttling of nuclear factor‐κB on primed DCs. Our study provides the first evidence for the presence of TRs on bone marrow‐derived DCs and the ability of THs to regulate DC maturation and function. These results have profound implications in immunopathology, including cancer and autoimmune manifestations of the thyroid gland at the crossroads of the immune and endocrine systems. Mascanfroni, I., Montesinos, M., Susperreguy, S., Cervi, L., Ilarregui, J. M., Ramseyer, V. D., Masini‐Repiso, A. M., Targovnik, H. M., Rabinovich, G. A., Pellizas, C. G. Control of dendritic cell maturation and function by triiodothyronine. FASEB J. 22, 1032–1042 (2008)

Excretory-secretory products (ESP) from Fasciola hepatica induce tolerogenic properties in myeloid dendritic cells.

Fasciola hepatica is a helminth trematode that migrates through the host tissues until reaching bile ducts where it becomes an adult. During its migration the parasite releases different excretory-secretory products (ESP), which are in contact with the immune system. In this study, we focused on the effect of ESP on the maturation and function of murine bone marrow derived-dendritic cells (DC). We found that the treatment of DC with ESP failed to induce a classical maturation of these cells, since ESP alone did not activate DC to produce any cytokines, although they impaired the ability of DC to be activated by TLR ligands and also their capacity to stimulate an allospecific response. In addition, using an in vitro ovalbumin peptide-restricted priming assay, ESP-treated DC exhibited a capacity to drive Th2 and regulatory T cell (Treg) polarization of CD4(+) cells from DO11.10 transgenic mice. This was characterized by increased IL-4, IL-5, IL-10 and TGF-beta production and the expansion of CD4(+)CD25(+)Foxp3(+) cells. Our results support the hypothesis that ESP from F. hepatica modulate the maturation and function of DC as part of a generalized immunosuppressive mechanism that involves a bias towards a Th2 response and Treg development.

Helminth Antigens Enable CpG-Activated Dendritic Cells to Inhibit the Symptoms of Collagen-induced Arthritis through Foxp3+ Regulatory T Cells

Dendritic cells (DC) have the potential to control the outcome of autoimmunity by modulating the immune response. In this study, we tested the ability of Fasciola hepatica total extract (TE) to induce tolerogenic properties in CpG-ODN (CpG) maturated DC, to then evaluate the therapeutic potential of these cells to diminish the inflammatory response in collagen induced arthritis (CIA). DBA/1J mice were injected with TE plus CpG treated DC (T/C-DC) pulsed with bovine collagen II (CII) between two immunizations with CII and clinical scores CIA were determined. The levels of CII-specific IgG2 and IgG1 in sera, the histological analyses in the joints, the cytokine profile in the draining lymph node (DLN) cells and in the joints, and the number, and functionality of CD4+CD25+Foxp3+ T cells (Treg) were evaluated. Vaccination of mice with CII pulsed T/C-DC diminished the severity and incidence of CIA symptoms and the production of the inflammatory cytokine, while induced the production of anti-inflammatory cytokines. The therapeutic effect was mediated by Treg cells, since the adoptive transfer of CD4+CD25+ T cells, inhibited the inflammatory symptoms in CIA. The in vitro blockage of TGF-β in cultures of DLN cells plus CII pulsed T/C-DC inhibited the expansion of Treg cells. Vaccination with CII pulsed T/C-DC seems to be a very efficient approach to diminish exacerbated immune response in CIA, by inducing the development of Treg cells, and it is therefore an interesting candidate for a cell-based therapy for rheumatoid arthritis (RA).

Indoleamine 2,3-dioxigenase (IDO) is critical for host resistance against Trypanosoma cruzi

Indoleamine 2,3‐dioxigenase (IDO) is an inflammatory cytokine‐inducible rate‐limiting enzyme of the tryptophan (Trp) catabolism, which is involved in the inhibition of intracellular pathogen replication as well as in immunomodulation. Here we demonstrated the effect of IDO‐dependent Trp catabolism on Trypanosoma cruzi resistance to acute infection. Infection with T. cruzi resulted in the systemic activation of IDO. The blocking of IDO activity in vivo impaired resistance to the infection and exacerbated the parasite load and infection‐associated pathology. In addition, IDO activity was critical to controlling the parasites replication in macrophages (Mos), despite the high production of nitric oxide produced by IDO‐blocked T. cruzi‐infected Mos. Analysis of the mechanisms by which IDO controls the parasite replication revealed that T. cruzi amastigotes were sensitive to l‐kynurenine downstream metabolites 3‐hydroxykynurenine (3‐HK) and 3‐hydroxyanthranilic acid, while 3‐HK also affected the trypomastigote stage. Finally, 3‐HK treatment of mice acutely infected with T. cruzi was able to control the parasite and to improve the survival of lethally infected mice. During infection, IDO played a critical role in host defense against T. cruzi; therefore, the intervention of IDO pathway could be useful as a novel antitrypanosomatid therapeutic strategy.—Knubel, C. P., Martínez, F. F., Fretes, R. E., Díaz Lujan, C., Theumer, M. G., Cervi, L., Motran, C. C. Indoleamine 2,3‐dioxigenase (IDO) is critical for host resistance against Trypanosoma cruzi. FASEB J. 24, 2689–2701 (2010). www.fasebj.org

Involvement of excretion-secretion products from Fasciola hepatica inducing suppression of the cellular immune responses.

Normal rats i.p. injected with Fasciola hepatica excretor-secretor antigen (ESA) induced a population of spleen mononuclear (SpM) cells, which suppressed the delayed type hypersensitivity (DTH) response to parasite antigens as well as to non-related antigens (human serum albumin) by adoptive transfer. A similar effect was observed when the cell transfer was performed with SpM cells non-adherent to nylon wool. The DTH was not modified by cells transfer adherent to nylon wool in syngeneic receptor animals. The observed suppression depended on the concentration and inoculation moment of the antigen; 1.8 mg of protein ESA being enough to suppress the DTH response at the different days studied, before and after immunization with whole F. hepatica antigens. A marked suppression was observed when ESA was injected on day 7 pre-immunization. On the other hand, inoculation of ESA treated with 0.01 M sodium periodate (carbohydrate oxidant) diminished the suppressor effect found after the native ESA inoculation, indicating participation of ESA glucidic components in induced suppression. Inoculation of ESA fractions obtained from polyacrylamide gel elution with different MW range, showed that components between 12 and 23 kDa actively induced suppression to the DTH response to parasite antigens.

Inhibition of spleen cell proliferative response to mitogens by excretory-secretory antigens of Fasciola hepatica

The effect of Fasciola hepatica excretory-secretory antigen (ESA) on the proliferative response of spleen mononuclear (SpM) cells of normal rats to stimulation with mitogens has been examined. When ESA was added to normal SpM cells, there was a decrease in the proliferative response to concanavalin A (Con A) or lipo-polysaccharide (LPS) in a dose-dependent manner. The addition of indomethacin, which blocks prostaglandin synthesis, or N omega-nitro-L-arginine methyl ester (L-NAME) a specific inhibitor of nitric oxide (NO) synthase, had no effect on the ability of ESA to suppress the proliferative response to Con A. However, supplementation of the culture media with catalase, which degrades hydrogen peroxide (H2O2) or superoxide dismutase (SOD) to remove superoxide anion (O2), resulted in a restoration of proliferation to Con A. When LPS was used as mitogenic stimulus no inhibitor added to the culture restored the proliferation. These results suggest that H2O2 and O2- are involved in the suppressor phenomenon induced by ESA in the T-cell proliferative events.

Pregnancy-specific glycoprotein 1a activates dendritic cells to provide signals for Th17-, Th2-, and Treg-cell polarization

Because of their plasticity and central role in orchestrating immunity and tolerance, DCs can respond to pregnancy‐specific signals, thus promoting the appropriate immune response in order to support pregnancy. Here, we show that pregnancy‐specific glycoprotein (PSG1a), the major variant of PSG released into the circulation during pregnancy, targets DCs to differentiate into a subset with a unique phenotype and function. This semi‐mature phenotype is able to secrete IL‐6 and TGF‐β. PSG1a also affected the maturation of DCs, preventing the up‐regulation of some costimulatory molecules, and inducing the secretion of TGF‐β or IL‐10 and the expression of programmed death ligand 1 (PD‐L1) in response to TLR‐9 or CD40 ligation. In addition, PSG1a‐treated DCs promoted the enrichment of Th2‐type cytokines, IL‐17‐producing cells, and Treg cells from CD4+ T cells from DO11.10 Tg mice. Moreover, in vivo expression of PSG1a promoted the expansion of Ag‐specific CD4+CD25+Foxp3+ Treg cells and IL‐17‐, IL‐4‐, IL‐5‐, and IL‐10‐secreting cells able to protect against Listeria monocytogenes infection. Taken together, our data indicate that DCs can be targeted by PSG1a to generate the signals necessary to mount an appropriate, well‐balanced, and effective immune response able to protect against invading pathogens while at the same time being compatible with a successful pregnancy.

Glycans from Fasciola hepatica Modulate the Host Immune Response and TLR-Induced Maturation of Dendritic Cells

Helminths express various carbohydrate-containing glycoconjugates on their surface, and they release glycan-rich excretion/secretion products that can be very important in their life cycles, infection and pathology. Recent evidence suggests that parasite glycoconjugates could play a role in the evasion of the immune response, leading to a modified Th2-polarized immune response that favors parasite survival in the host. Nevertheless, there is limited information about the nature or function of glycans produced by the trematode Fasciola hepatica, the causative agent of fasciolosis. In this paper, we investigate whether glycosylated molecules from F. hepatica participate in the modulation of host immunity. We also focus on dendritic cells, since they are an important target of immune-modulation by helminths, affecting their activity or function. Our results indicate that glycans from F. hepatica promote the production of IL-4 and IL-10, suppressing IFNγ production. During infection, this parasite is able to induce a semi-mature phenotype of DCs expressing low levels of MHCII and secrete IL-10. Furthermore, we show that parasite glycoconjugates mediate the modulation of LPS-induced maturation of DCs since their oxidation restores the capacity of LPS-treated DCs to secrete high levels of the pro-inflammatory cytokines IL-6 and IL-12/23p40 and low levels of the anti-inflammatory cytokine IL-10. Inhibition assays using carbohydrates suggest that the immune-modulation is mediated, at least in part, by the recognition of a mannose specific-CLR that signals by recruiting the phosphatase Php2. The results presented here contribute to the understanding of the role of parasite glycosylated molecules in the modulation of the host immunity and might be useful in the design of vaccines against fasciolosis.

Cytokines involved in the immunosuppressor period in experimental fasciolosis in rats

The aim of this study was to evaluate the kinetics of the cytokines interferon-gamma, interleukin-2, interleukin-10 and interleukin-4 produced by spleen mononuclear cells stimulated by Con A during an experimental infection in rats with Fasciola hepatica. The proliferative response to Con A of Spm cells from rats infected with F. hepatica was significantly decreased on day 7 post-infection (P<0.006) and simultaneously an increase of interferon-gamma, interleukin-10 and interleukin-4 production along with a decrease of interleukin-2 by spleen mononuclear cells were observed. Interleukin-4 and interleukin-10 were involved in ablating cellular proliferation in vitro, as the addition of neutralising antibodies to either cytokine reversed the proliferative block. The addition of exogenous recombinant interleukin-2 also restored the proliferative response by spleen mononuclear cells obtained 7 days after infection from infected rats. At the same time, we found an increase in interleukin-10 production by peritoneal cells (in close contact with the flukes) and decreased nitric oxide levels. In addition, histological studies on the liver on day 7 after infection showed the presence of parasite inside migratory tunnels in the parenchyma, and polymorphonuclear leukocytes, predominantly eosinophils, around the parasite. The transient suppression in proliferative response mediated by cytokines interleukin-4 and interleukin-10 in the spleen, and diminution of nitric oxide production in the peritoneum could be mechanisms to evade the protective immune response during the first stages of liver penetration by the parasite.