IL-4 and IL-10 are essential for immunosuppression induced by high molecular weight proteins from Ascaris suum

Extract from Ascaris suum and N-acetyl-L-cysteine induces an immunosuppressant effect in model of autoimmune hepatitis

BACKGROUND

Extract of adult Ascaris suum (ASC) worms attenuated the liver damage in experimental autoimmune hepatitis (EAH) with induction of Th2 immune response, but fibrosis occurred. N-acetyl-L-cysteine (NAC) has protective effects against liver fibrosis.

OBJECTIVES

Evaluate the association ASC + NAC on the T- and B-cell activation, inflammation and fibrogenic markers in the liver in EAH.

METHODS

Experimental autoimmune hepatitis was induced intravenously with concanavalin A in BALB/c mice. EAH + ASC+NAC group received NAC and ASC; EAH + ASC group received ASC; EAH group received PBS. Doubly labelled CD4⁺ T (CD28, CTLA-4, CD40L or IL-10) and CD45R⁺ B lymphocytes (IL-10) and CD4⁺ CD25⁺ FoxP3⁺ cells were evaluated, along with gene expression of Col1a1, α-SMA, Fizz1, Arg1 and PPAR-γ and histomorphometry.

RESULTS

Experimental autoimmune hepatitis group showed high frequency of CD28⁺ and CD40L⁺  T lymphocytes, but not the EAH + ASC group. In relation to EAH group, the Fizz1 expression was lower in both groups treated, but Arg1 expression was lower in only EAH + ASC+NAC group. In the EAH + ASC+NAC group, there were higher frequencies of CD4⁺ IL-10⁺ and CD4⁺ CD25⁺ FoxP3⁺ cells, but not CD45R⁺ IL-10⁺ , along with mitigated inflammation and collagen production.

CONCLUSIONS

Ascaris suum favoured immunosuppression in EAH limiting the T cells activation. However, association ASC and NAC was necessary for attenuating the inflammatory process and collagen production.

Lipopolysaccharide and lipotheicoic acid differentially modulate epididymal cytokine and chemokine profiles and sperm parameters in experimental acute epididymitis

Bacterial infections are the most prevalent etiological factors of epididymitis, a commonly diagnosed inflammatory disease in the investigation of male infertility factors. The influence of early pathogenic mechanisms at play during bacterial epididymitis on reproductive outcomes is little understood. We report here that experimental epididymitis induced in rats by Gram-negative (LPS) and Gram-positive (LTA) bacterial products resulted in differential patterns of acute inflammation in the cauda epididymis. LPS elicited a strong inflammatory reaction, as reflected by upregulation of levels of mRNA for seven inflammatory mediators (Il1b, Tnf, Il6, Ifng, Il10, Nos2 and Nfkbia), and tissue concentration of six cytokines/chemokines (IL1A, IL1B, IL6, IL10, CXCL2 and CCL2) within the first 24 h post-treatment. Conversely, LTA induced downregulation of one (Nfkbia) and upregulation of six (Il1b, Il6, Nos2, Il4 Il10 and Ptgs1) inflammatory gene transcripts, whereas increased the tissue concentration of three cytokines/chemokines (IL10, CXCL2 and CCL2). The stronger acute inflammatory response induced by LPS correlated with a reduction of epididymal sperm count and transit time that occurred at 1, 7, and 15 days post-treatment. Our study provides evidence that early epididymal inflammatory signaling events to bacterial activators of innate immunity may contribute to the detrimental effects of epididymitis upon male fertility.

Hookworm excretory/secretory products modulate immune responses to heterologous and species-specific antigens

Approximately one billion people are currently infected with hookworm. Despite its high prevalence and the concomitant immune suppression seen in infected individuals, little research has been performed on the mechanism of immunosuppression by hookworm. Our study focused on characterizing mechanisms utilized by hookworm to suppress the host immune response. Splenocytes and draining lymph node cells from mice injected with hookworm excretory/secretory (ES) proteins showed decreased proliferation in response to both heterologous and species-specific antigens while also having increased nitric oxide secretion. Analysis by fluorescence-activated cell sorting revealed that mice injected with ES had reduced percentages of CD4⁺ T cells indicating potential effects of ES proteins on lymphocyte homeostasis. Antibody and cytokine response analyses demonstrated that immunization with ES proteins decreased IgG and IgG1 levels, also decreased interleukin (IL-)-4 and increased IL-12 and interferon-gamma (IFN-γ) cytokine production suggesting impairment of B-cell activation and a shift towards a nonhealing IL-12 directed T helper-1 immune response. Together, these data demonstrate for the first time that host immunosuppression by hookworms is orchestrated by ES proteins and provide mechanisms underlying the shift towards a nonhealing Th-1 profile as seen in humans suffering from hookworm infection.

Immunomodulation of liver injury by Ascaris suum extract in an experimental model of autoimmune hepatitis

Adult worm extract from Ascaris suum (Asc) has immunosuppressive activity and elicits Th2/IL-4/IL-10 response. This study evaluated the prophylactic and therapeutic effect of Asc in a murine model of concanavalin A (ConA)-induced autoimmune hepatitis (AIH). BALB/c mice received ConA, iv, (20 mg/kg), and three groups of animals were formed: (1) AIH, received only ConA; (2) AIH + Asc prophylactic, treated with Asc (1 mg/ml), ip, 30 min before of the AIH; and (3) AIH + Asc therapeutic, treated with Asc 2 h after the AIH. Plasma transaminase and immunoglobulins (measured at 8 and 24 h and 7 days after treatment) and cytokine production (IL-4, IL-10, IL-13, and IFN-γ) by splenocytes upon ConA and Asc stimulus were compared. The livers were weighed and examined histologically. In the AIH group, there was an increase in liver weight, transaminase levels, and total immunoglobulins. These parameters were reduced by 8-24 h and 7 days in the prophylactic group, but in the therapeutic group, only on day 7. The survival rate of mice in the AIH group was 38.5%, compared to 67% in the therapeutic Asc group. The survival rate of the animals with AIH that were prophylactically treated with Asc was 100%. A decrease of cellular infiltration and high levels of IL-4, IL-10, and IL-13 were induced by Asc. An increase of liver fibrosis was also observed, but with less intensity with prophylactic treatment. Thus, the Ascaris components have an inhibitory effect on AIH, with an intense Th2 immune response.

PAS-1, an Ascaris suum protein, modulates allergic airway inflammation via CD8+γδTCR+ and CD4+CD25+FoxP3+ T cells

We have previously demonstrated that PAS-1, a 200 kDa protein from Ascaris suum, has a potent immunomodulatory effect on humoral and cell-mediated responses induced by APAS-3 (an allergenic protein from A. suum) or unrelated antigens. In this study, we investigated the mechanisms by which PAS-1 is able to induce this effect on an allergic airway inflammation induced by OVA in mice. C57BL/6 mice were adoptively transferred on day 0 with seven different PAS-1-primed cell populations: PAS-1-primed CD19(+) or B220(+) or CD3(+) or CD4(+) or CD8(+) or CD4(+) CD25⁻ or CD4(+) CD25(+) lymphocytes. These mice were immunized twice with OVA and alum by intraperitoneal route (days 0 and 7) and challenged twice by intranasal route (days 14 and 21). Two days after the last challenge, the airway inflammation was evaluated by antibody levels, cellular migration, eosinophil peroxidase levels, cytokine and eotaxin production, and pulmonary mechanical parameters. Among the adoptively transferred primed lymphocytes, only CD4(+) CD25(+) , CD8(+) or the combination of both T cells impaired the production of total IgE and OVA-specific IgE and IgG1 antibodies, eosinophilic airway inflammation, Th2-type cytokines (IL-4, IL-5 and IL-13), eotaxin release and airway hyperreactivity. Moreover, airway recruited cells from CD4(+) CD25(+) and CD8(+) T-cell recipient secreted more IL-10/TGF-β and IFN-γ, respectively. Moreover, we found that PAS-1 expands significantly the number of CD4(+) CD25(+) FoxP3(+) and CD8(+) γδTCR(+) cells. In conclusion, these findings demonstrate that the immunomodulatory effect of PAS-1 is mediated by these T-cell subsets.

Boosting the suppressive effects of Ascaris suum components in IFN-γ-deficient mice

High molecular weight components from Ascaris suum extract suppress ovalbumin-specific immunity in mice. In IFN-γ-deficient mice, ovalbumin-specific delayed-type hypersensitivity reactions are more strongly downregulated by these suppressive components. Here, the cellularity of the delayed-type hypersensitivity reaction in IFN-γ-deficient mice and the increased downregulation induced by Ascaris suum components were analyzed. IL-12p40-dependent neutrophilic influx was predominant. Suboptimal doses of the suppressive fraction from this nematode completely inhibited the hypersensitivity reaction, thus indicating intensification of the immunosuppression under conditions of intense recruitment of IFN-γ-independent neutrophils.

Functional group/guild modelling of inter-specific pathogen interactions: a potential tool for predicting the consequences of co-infection

Although co-infection is the norm in most human and animal populations, clinicians currently have no practical tool to assist them in choosing the best treatment strategy for such patients. Given the vast range of potential pathogens which may co-infect the host, obtaining such a practical tool may seem an intractable problem. In ecology the joint concepts of functional groups and guilds have been used to conceptually simplify complex ecosystems, in order to understand how their component parts interact and may be manipulated. Here we propose a mechanism by which to apply these concepts to pathogen co-infection systems. Further, we describe how these groups could be incorporated into a mathematical modelling framework which, after validation, could be used as a clinical tool to predict the outcome of any particular combination of pathogens co-infecting a host.

Impairment of dendritic cell function by excretory-secretory products: A potential mechanism for nematode-induced immunosuppression

To determine whether helminth-derived products modulate dendritic cell (DC) function, we investigated the effects of excretory-secretory products (ES) and adult worm homogenate (AWH) derived from the gastrointestinal nematode Heligmosomoides polygyrus (Hp) on murine bone marrow-derived DC (BMDC). Compared to the TLR9 ligand CpG, Hp-derived products alone failed to induce DC activation. ES, but not AWH, inhibited BMDC cytokine and chemokine production and co-stimulatory molecule expression (CD40, CD86 and MHC class II) induced by TLR ligation. TLR ligand-independent, PMA-induced DC activation was unaffected by ES. Recipients of ES-treated BMDC pulsed with OVA had suppressed Ab responses in vivo, irrespective of the Th1 or Th2 isotype affiliation, compared to recipients of control OVA-pulsed BMDC. Importantly, suppression occurred even in the presence of the potent type 1 adjuvant CpG. In contrast to untreated OVA-pulsed BMDC, ES-treated BMDC pulsed with OVA had reduced co-stimulatory molecule and cytokine expression. CD4(+)CD25(+)Foxp3(-) T cells, which secreted high IL-10 levels, were generated in co-cultures of OT-II OVA-specific TCR-transgenic CD4(+) T cells and ES-treated BMDC. These IL-10-secreting T cells suppressed effector CD4(+) T cell proliferation and IFN-gamma production, the latter effect mediated by an IL-10-dependent mechanism. Together, these results demonstrate that nematode ES impaired DC function and suppressed both Th1 and Th2 adaptive immune responses possibly by inducing regulatory T cells.

Modulation of anaphylaxis by helminth-derived products in animal models

Helminths have a profound immunomodulatory effect upon the inductive and effector phases of inflammatory responses, including allergy. Several animal models of anaphylaxis have been established to investigate the mechanisms by which helminth infections or helminth-derived products interfere with the onset of allergic reactions. The focus of our studies was the immunosuppression induced by the intestinal roundworm Ascaris suum in the production of anaphylactic antibodies and the development of lung eosinophilic inflammation and hyperreactivity to its own allergens and to unrelated antigens. Thus, we identified a single protein affinity purified from the A. suum body extract, named PAS-1, which maintains all its immunosuppressive properties and promotes a significant increase in interleukin-10 production, an essential cytokine for the effectiveness of the suppressive mechanism. In addition, PAS-1 primes for regulatory T cells, which also mediate this mechanism. Therefore, this helminth molecule may be a promising target for therapeutic applications in allergic disorders.

Immunosuppressive components ofAscaris suumdown-regulate expression of costimulatory molecules and function of antigen-presenting cellsvia an IL-10-mediated mechanism

High-molecular-weight components (PI) of Ascaris suum suppress both cell-mediated and humoral responses against ovalbumin (OVA) via an IL-4/IL-10-dependent mechanism. The aim of this work was to investigate the effect of PI on the ability of APC to activate T cells and the role of IL-10 in this process. Flow cytometry analyses of MHC class II, CD80, CD86 and CD40 molecules on LN cells from mice immunized with OVA or OVA+PI showed that PI inhibits expression of these molecules on unfractionated cells and on purified CD11c(+) cells. A low proliferative response was obtained when OVA-specific TCR-Tg T cells were incubated with CD11c(+) cells from OVA+PI-immunized mice pulsed with OVA, when compared to those incubated with cells from OVA-immunized mice. Similar results were obtained using as APC CD11c(+) cells from OVA-immunized mice pulsed with OVA+PI, which also expressed less of the four markers. The inhibitory effect of PI on both the expression of costimulatory molecules and the induction of T cell proliferation was abolished in IL-10-deficient mice. Our data indicate that the potent immunosuppressive effect of A. suum extract components on the host immune system is primarily related to their property of down-regulating the Ag-presenting ability of DC via an IL-10-mediated mechanism.

Ascaris suum-derived products suppress mucosal allergic inflammation in an interleukin-10-independent manner via interference with dendritic cell function

We have previously demonstrated that protection from allergic inflammation by Ascaris suum infection was characterized by a global increase in interleukin-10 (IL-10) and the development of protective CD4(+)/CD25(+) T cells (L. Schopf, S. Luccioli, V. Bundoc, P. Justice, C. C. Chan, B. J. Wetzel, H. H. Norris, J. F. Urban, Jr., and A. Keane-Myers, Investig. Ophthalmol. Vis. Sci. 46:2772-2780, 2005). Here, we used A. suum pseudocoelomic fluid (PCF) in lieu of infection to define molecular mechanisms of allergic protection in a mouse model of allergic inflammation. Mice were sensitized with ragweed (RW) and PCF (RW/PCF), PCF alone, or RW alone and then challenged intratracheally, intranasally, and supraocularly with RW. Histological examination of the eyes and lungs, analysis of the bronchoalveolar lavage fluid (BALF), and characterization of ex vivo cytokine responses were performed to determine allergic inflammatory responses. RW/PCF-treated mice had suppressed allergic immune responses compared to mice given RW alone. To investigate whether IL-10 was involved in PCF-mediated allergic protection, similar experiments were performed using mice genetically deficient for IL-10. Persistent protection from allergic disease was observed in the absence of IL-10, indicating the primary mechanism of PCF protection is IL-10 independent. Ex vivo and in vitro analysis of PCF-treated dendritic cells (DC) demonstrated reduced activation receptor expression and cytokine production in response to either RW or lipopolysaccharide stimulation. These findings extend previous studies that showed infection with A. suum alters expression of allergic disease and suggest that PCF can contribute to this effect by interference with DC function.

Regulation of Anaphylactic IgG1 Antibody Production by IL-4 and IL-10

BACKGROUND

Different cytokines have been implicated in the regulation of isotype expression in primary and secondary antibody responses. The aim of this study was to assess the regulation of anaphylactic IgG1 and IgE antibodies by IL-4, IL-10 and IFN-gamma at different time points of the antibody response against PI, an immunosuppressive fraction of Ascaris suum extract, and ovalbumin (OVA).

METHODS

Wild-type or cytokine-deficient C57BL/6 or BALB/c mice were immunized with PI or OVA in different adjuvants. Twenty days later, they were boosted with the respective antigen. IgG1 and IgE antibodies produced during primary and secondary responses were measured by passive cutaneous anaphylaxis.

RESULTS

PI induced low levels of anaphylactic IgG1 antibodies in the primary response and moderate levels after the antigenic booster, which were IL-4-dependent. In the absence of IL-10 and IFN-gamma, PI-specific IgG1 and IgE enhanced significantly, indicating that these cytokines downregulated antibody production in primary and secondary responses. The IgG1 response to OVA in aluminium hydroxide or complete Freund's adjuvant was IL-4-dependent in the beginning of the primary response. Later on, it became only partially regulated by IL-4 in C57BL/6 mice and IL-4-independent in Th2-prone BALB/c mice. In contrast, IgE antibodies depended exclusively upon IL-4 during the entire time course.

CONCLUSIONS

These results indicate, first, that the IL-4 dependency of anaphylactic IgG1 antibody production, mainly in the secondary response, varies among mouse strains, and, second, that the nature of the antigen determines whether IL-10 and IFN-gamma limit the potential to make large amounts of anaphylactic IgG1 and IgE.

PAS-1, a protein affinity purified from Ascaris suum worms, maintains the ability to modulate the immune response to a bystander antigen

Helminth infections and parasite components have potent immunomodulatory effects on a host's immune system. In the present study, we investigated the effect of PAS-1, a protein component of Ascaris suum adult worms recognized by a monoclonal antibody (MAIP-1), on humoral and cell-mediated responses to a bystander antigen (ovalbumin [OVA]). MAIP-1 recognized only one of the three polypeptide chains of PAS-1, but neutralized the suppressive effect of the whole worm extract on OVA-specific antibody production. PAS-1 inhibited antibody production against a T-cell-dependent, but not a T-cell-independent, antigen in a dose-dependent way. IgM, IgG1, IgG2b, and also IgE and anaphylactic IgG1 levels were downregulated. In addition, PAS-1 inhibited OVA-specific delayed type hypersensitivity reactions in the footpad of mice, showing a potent immunosuppressive activity on both Th1 and Th2 responses that seems to be mediated by the induction of large amounts of IL-10 and IL-4. Indeed, PAS-1-specific spleen cells secreted sevenfold more IL-10 and threefold more IL-4 than OVA-specific cells in response to in vitro restimulation with the respective antigens. In conclusion, we showed that PAS-1, a single protein component from A. suum, maintains all its immunosuppressive properties.

Modulation of murine experimental asthma by Ascaris suum components

BACKGROUND

We have recently isolated two distinct components from Ascaris suum adult worms with different effects on the immune system: the allergenic protein of A. suum (APAS-3), which induces IgE antibody production, and suppressive protein of A. suum (PAS-1), which inhibits humoral and cellular immune responses induced by unrelated antigens. In this study, we investigated the immunomodulatory effect of PAS-1 on a murine model of asthma induced by APAS-3.

METHODS

BALB/c mice were immunized twice with APAS-3 or APAS-3 plus PAS-1 by the intraperitoneal and subcutaneous route (on days 0 and 7) and challenged twice with the same antigens intranasally (days 14 and 21). Two days after the last challenge, the allergic airway inflammation was evaluated by cellular migration, eosinophil peroxidase (EPO) activity, cytokine and chemokine production and pulmonary mechanical parameters.

RESULTS

The allergenic properties of APAS-3 were confirmed by the stimulation of anaphylactic IgE and IgG1 antibody production and eosinophilic airway inflammation and hyper-responsiveness. On the other hand, PAS-1-treated mice showed a marked suppression of cellular migration and EPO activity that correlated well with a significant reduction in the levels of IL-4, IL-5, eotaxin and RANTES in the bronchoalveolar lavage (BAL) fluid. In contrast, considerable amounts of IL-10 were observed in the BAL fluid of PAS-1-treated mice. Airway hyper-responsiveness was obtained in APAS-3-immunized mice, but the conductance of the respiratory system was restored to normal values in the presence of PAS-1.

CONCLUSION

These results indicate that A. suum allergenic protein APAS-3 induces a T helper 2-type immune response and, consequently, eosinophilic airway inflammation and hyper-responsiveness. Moreover, the modulatory protein PAS-1 has a marked suppressive effect on this response, and the inhibition of cytokine (IL-4, IL-5) and chemokine (eotaxin and RANTES) release, probably because of the presence of IL-10, may contribute to this effect.