Central role for interleukin-4 in regulating nitric oxide-mediated inhibition of T-cell proliferation and gamma interferon production in schistosomiasis

Cysteinyl leukotriene receptor-1 as a potential target for host-directed therapy during chronic schistosomiasis in murine model

Schistosomiasis remains the most devastating neglected tropical disease, affecting over 240 million people world-wide. The disease is caused by the eggs laid by mature female worms that are trapped in host's tissues, resulting in chronic Th2 driven fibrogranulmatous pathology. Although the disease can be treated with a relatively inexpensive drug, praziquantel (PZQ), re-infections remain a major problem in endemic areas. There is a need for new therapeutic drugs and alternative drug treatments for schistosomiasis. The current study hypothesized that cysteinyl leukotrienes (cysLTs) could mediate fibroproliferative pathology during schistosomiasis. Cysteinyl leukotrienes (cysLTs) are potent lipid mediators that are known to be key players in inflammatory diseases, such as asthma and allergic rhinitis. The present study aimed to investigate the role of cysLTR1 during experimental acute and chronic schistosomiasis using cysLTR1-/- mice, as well as the use of cysLTR1 inhibitor (Montelukast) to assess immune responses during chronic Schistosoma mansoni infection. Mice deficient of cysLTR1 and littermate control mice were infected with either high or low dose of Schistosoma mansoni to achieve chronic or acute schistosomiasis, respectively. Hepatic granulomatous inflammation, hepatic fibrosis and IL-4 production in the liver was significantly reduced in mice lacking cysLTR1 during chronic schistosomiasis, while reduced liver pathology was observed during acute schistosomiasis. Pharmacological blockade of cysLTR1 using montelukast in combination with PZQ reduced hepatic inflammation and parasite egg burden in chronically infected mice. Combination therapy led to the expansion of Tregs in chronically infected mice. We show that the disruption of cysLTR1 is dispensable for host survival during schistosomiasis, suggesting an important role cysLTR1 may play during early immunity against schistosomiasis. Our findings revealed that the combination of montelukast and PZQ could be a potential prophylactic treatment for chronic schistosomiasis by reducing fibrogranulomatous pathology in mice. In conclusion, the present study demonstrated that cysLTR1 is a potential target for host-directed therapy to ameliorate fibrogranulomatous pathology in the liver during chronic and acute schistosomiasis in mice.

Effect of Allium cepa extract on total and differential WBC, TP level, oxidant and antioxidant biomarkers, and lung pathology in ovalbumin-sensitized rats

BACKGROUND

Previous studies have shown that Allium cepa (A. cepa) has relaxant and anti-inflammatory effects. In this research, A. cepa extract was examined for its prophylactic effect on lung inflammation and oxidative stress in sensitized rats.

METHODS

Total and differential white blood cell (WBC) count in the blood, serum levels of oxidant and antioxidant biomarkers, total protein (TP) in bronchoalveolar lavage fluid (BALF), and lung pathology were investigated in control group (C), sensitized group (S), and sensitized groups treated with A. cepa and dexamethasone.

RESULTS

Total and most differential WBC count, TP, NO2, NO3, MDA (malondialdehyde), and lung pathological scores were increased while lymphocytes, superoxide dismutase (SOD), catalase (CAT), and thiol were decreased in sensitized animals compared to controls (p < 0.01 to p < 0.001). Treatment with all concentrations of extract significantly improved total WBC, TP, NO2, NO3, interstitial fibrosis, and emphysema compared to the S group (p < 0.05 to p < 0.001). Two higher concentrations of the extract significantly decreased neutrophil and monocyte count, malondialdehyde, bleeding and epithelial damage but increased lymphocyte, CAT, and thiol compared to the S group (p < 0.05 to p < 0.001). Dexamethasone treatment also substantially improved most measured parameters (p < 0.05 to p < 0.001), but it did not change eosinophil percentage. It was proposed that A. cepa extract could affect lung inflammation and oxidative stress in sensitized rats.

Cytokines and microRNAs in SARS-CoV-2: What do we know?

The coronavirus disease 2019 (COVID-19) pandemic constitutes a global health emergency. Currently, there are no completely effective therapeutic medications for the management of this outbreak. The cytokine storm is a hyperinflammatory medical condition due to excessive and uncontrolled release of pro-inflammatory cytokines in patients suffering from severe COVID-19, leading to the development of acute respiratory distress syndrome (ARDS) and multiple organ dysfunction syndrome (MODS) and even mortality. Understanding the pathophysiology of COVID-19 can be helpful for the treatment of patients. Evidence suggests that the levels of tumor necrosis factor alpha (TNF-α) and interleukin (IL)-1 and IL-6 are dramatically different between mild and severe patients, so they may be important contributors to the cytokine storm. Several serum markers can be predictors for the cytokine storm. This review discusses the cytokines involved in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, focusing on interferons (IFNs) and ILs, and whether they can be used in COVID-19 treatment. Moreover, we highlight several microRNAs that are involved in these cytokines and their role in the cytokine storm caused by COVID-19.

Dynamics of Host Immune Response Development During Schistosoma mansoni Infection

Schistosomiasis is a disease of global significance, with severity and pathology directly related to how the host responds to infection. The immunological narrative of schistosomiasis has been constructed through decades of study, with researchers often focussing on isolated time points, cell types and tissue sites of interest. However, the field currently lacks a comprehensive and up-to-date understanding of the immune trajectory of schistosomiasis over infection and across multiple tissue sites. We have defined schistosome-elicited immune responses at several distinct stages of the parasite lifecycle, in three tissue sites affected by infection: the liver, spleen, and mesenteric lymph nodes. Additionally, by performing RNA-seq on the livers of schistosome infected mice, we have generated novel transcriptomic insight into the development of schistosome-associated liver pathology and fibrosis across the breadth of infection. Through depletion of CD11c+ cells during peak stages of schistosome-driven inflammation, we have revealed a critical role for CD11c+ cells in the co-ordination and regulation of Th2 inflammation during infection. Our data provide an updated and high-resolution account of how host immune responses evolve over the course of murine schistosomiasis, underscoring the significance of CD11c+ cells in dictating host immunopathology against this important helminth infection.

Current Understanding of Immunity Against Schistosomiasis: Impact on Vaccine and Drug Development

Schistosomiasis is a neglected tropical disease inflicting significant morbidity in humans worldwide. The disease is caused by infections with a parasitic trematode belonging to the genus Schistosoma. Over 250 million people are currently infected globally, with an estimated disability-adjusted life-years of 1.9 million attributed to the disease. Current understanding, based on several immunological studies using experimental and human models of schistosomiasis, reveals that complex immune mechanisms play off each other in the acquisition of immune resistance to infection/reinfection. Nevertheless, the precise characteristics of these responses, the specific antigens against which they are elicited, and how these responses are intricately regulated are still being investigated. What is apparent is that immunity to schistosome infections develops slowly and over a prolonged period of time, augmented by the death of adult worms occurring naturally or by praziquantel therapy. In this review, aspects of immunity to schistosomiasis, host–parasite interactions and their impact on schistosomiasis vaccine development are discussed.

Identification, expression profiling and functional characterization of interleukin 11a ortholog from redlip mullet Liza haematocheila: Insight into its roles in the inflammation and apoptosis regulation

Interleukin 11 (IL-11) is a secretory cytokine with pleotropic properties, including anti-inflammatory and anti-apoptotic functions. This study aimed to functionally characterize a teleostean IL-11a ortholog from redlip mullet (LhIL-11a) through bioinformatic analysis, transcriptional expression profiling and protein function assays. The deduced LhIL-11a protein sequence is 200 amino acids long, with a predicted molecular weight of 23.168 kDa. Multiple sequence alignment indicates that LhIL-11a has a typical four-bundle architecture of α-helixes as observed in other IL-11s. The identity-similarity matrix show a higher identity between LhIL-11a and other fish IL-11a sequences. Phylogenetic analysis demonstrated that LhIL-11a falls within a clade including other fish counterparts. In the tissue distribution analysis, the highest constitutive expression of LhIL-11a mRNA was observed in the mullet gastrointestinal tract and brain tissues. Following the challenges with LPS, poly I:C and Lactococcus garvie, the transcription levels of LhIL-11a were significantly upregulated in both PBCs and liver. In the biological functional assay, recombinant LhIL-11a protein showed strong activities of suppressing pro-inflammatory cytokines and apoptotic gene expression in mullet kidney cells and reducing LPS stimulated NO production in murine macrophage cells. Overall, the findings in this study provide the experimental clues to understanding the functional roles of fish IL-11a in inflammation and apoptosis regulation during host defense against invading microbial pathogens.

Indoleamine 2,3-Dioxygenase Activity During Acute Toxoplasmosis and the Suppressed T Cell Proliferation in Mice

Toxoplasma gondii (T. gondii) is an obligate intracellular parasite and belongs to the phylum Apicomplexa. T. gondii is of medical and veterinary importance, because T. gondii causes the parasitic disease toxoplasmosis. In human cells, the interferon-gamma inducible indoleamine 2,3-dioxygenase 1 (IDO1) is an antimicrobial effector mechanism that degrades tryptophan to kynurenine and thus limits pathogen proliferation in vitro. Furthermore, IDO is described to have immunosuppressive properties, e.g., regulatory T cell differentiation and T cell suppression in humans and mice. However, there is only little known about the role of IDO1 in mice during acute toxoplasmosis. To shed further light on the role of mIDO1 in vivo, we have used a specifically adjusted experimental model. Therein, we infected mIDO1-deficient (IDO^−/−) C57BL/6 mice and appropriate wild-type (WT) control mice with a high dose of T. gondii ME49 tachyozoites (type II strain) via the intraperitoneal route and compared the phenotype of IDO^−/− and WT mice during acute toxoplasmosis. During murine T. gondii infection, we found mIDO1 mRNA and mIDO1 protein, as well as mIDO1-mediated tryptophan degradation in lungs of WT mice. IDO^−/− mice show no tryptophan degradation in the lung during infection. Even though T. gondii is tryptophan auxotroph and rapidly replicates during acute infection, the parasite load was similar in IDO^−/− mice compared to WT mice 7 days post-infection. IDO1 is described to have immunosuppressive properties, and since T cell suppression is observed during acute toxoplasmosis, we analyzed the possible involvement of mIDO1. Here, we did not find differences in the intensity of ex vivo mitogen stimulated T cell proliferation between WT and IDO^−/− mice. Concomitant nitric oxide synthase inhibition and interleukin-2 supplementation increased the T cell proliferation from both genotypes drastically, but not completely. In sum, we analyzed the involvement of mIDO1 during acute murine toxoplasmosis in our specifically adjusted experimental model and found a definite mIDO1 induction. Nevertheless, mIDO1 seems to be functional redundant as an antiparasitic defense mechanism during acute toxoplasmosis in mice. Furthermore, we suggest that the systemic T cell suppression observed during acute toxoplasmosis is influenced by nitric oxide activity and IL-2 deprivation.

Purinergic signaling in schistosomal infection

Human schistosomiasis is a chronic inflammatory disease caused by blood fluke worms belonging to the genus Schistosoma. Health metrics indicate that the disease is related to an elevated number of years lost-to-disability and years lost-to-life. Schistosomiasis is an intravascular disease that is related to a Th1 and Th2 immune response polarization, and the degree of polarization affects the outcome of the disease. The purinergic system is composed of adenosine and nucleotides acting as key messenger molecules. Moreover, nucleotide-transforming enzymes and cell-surface purinergic receptors are obligatory partners of this purinergic signaling. In mammalian cells, purinergic signaling modulates innate immune responses and inflammation among other functions; conversely purinergic signaling may also be modulated by inflammatory mediators. Moreover, schistosomes also express some enzymes of the purinergic system, and it is possible that worms modulate host purinergic signaling. Current data obtained in murine models of schistosomiasis support the notion that the host purinergic system is altered by the disease. The dysfunction of adenosine receptors, metabotropic P2Y and ionotropic P2X₇ receptors, and NTPDases likely contributes to disease morbidity.

Inflammatory Immune Response

Lactic acid bacteria (LAB) are the most commonly used microorganisms in probiotic products and it is known that these LAB enhanced the immune response and increase resistance to neoplasia and infections. In previous studies using an experimental model of BALB/c mice it was demonstrated that a cyclical diet of yoghurt given to animals previously injected with the carcinogen 1,2 dimethylhydrazine (DMH) inhibited the development of colorectal carcinoma. The animals showed an inflammatory response prior to the development of the tumour, which was diminished with the yoghurt feeding. We examined the immunoregulatory and antiinflammatory mechanisms involved in the inhibition of tumour growth by yoghurt and compared with the mechanisms of a non-steroidal antiinflammatory drug (Indomethacin). Five experimental groups (BALB/c mice) were used in this study: 1) DMH group, injected with 1,2 dimethylhydrazine weekly for 10 weeks. 2) DMH-yoghurt group, yoghurt was supplemented 10 days followed by inoculation with DMH. After tumour induction yoghurt was given every 10 days for six months. 3) Only yoghurt given during six months following the same schedule (yoghurt control. 4) DMH-indomethacin group. After tumour induction, animals were treated with indomethacin, injected cyclically. 5) Non-treatment control group fed with a conventional balanced diet. We studied IgA secreting cells and CD4+ and CD8+ T cells in the large intestine of mice fed long term with yoghurt and others treated with indomethacin. TNFα, INFγ cytokines, Bcl2 protein and iNOS enzyme production was also measured We observed an increase in the number of IgA-secreting cells but not in the CD4+ and CD8+ cells in the mice fed long term with yoghurt. Indomethacin treated mice showed high values of all these cellular populations. Mice injected with indomethacin did not show increased levels of the proinflammatory cytokine TNFα and INFγ. These cytokines were increased in DMH and DMH plus yoghurt groups. iNOS enzyme determinations were increased in DMH and DMH plus indomethacin group. These results coincided with the inflammatory response observed in the histological findings. Bcl-2 protein was increased in mice fed long term with yoghurt. We suggest that the immune mechanisms by which yoghurt operates would be different to those induced with the antiinflammatory drug indomethacin. Yoghurt activated the production of cytokines that could exert a regulation of the immune response by apoptosis induced by TNFα. We conclude that yoghurt down modulate the immune response and exert its antitumour activity by its antiinflammatory activity, a mechanism that is different with that of the antiinflammatory indomethacin.

Immunology of human schistosomiasis

There is a wealth of immunologic studies that have been carried out in experimental and human schistosomiasis that can be classified into three main areas: immunopathogenesis, resistance to reinfection and diagnostics. It is clear that the bulk of, if not all, morbidity due to human schistosomiasis results from immune-response-based inflammation against eggs lodged in the body, either as regulated chronic inflammation or resulting in fibrotic lesions. However, the exact nature of these responses, the antigens to which they are mounted and the mechanisms of the critical regulatory responses are still being sorted out. It is also becoming apparent that protective immunity against schistosomula as they develop into adult worms develops slowly and is hastened by the dying of adult worms, either naturally or when they are killed by praziquantel. However, as with anti-egg responses, the responsible immune mechanisms and inducing antigens are not clearly established, nor are any potential regulatory responses known. Finally, a wide variety of immune markers, both cellular and humoral, can be used to demonstrate exposure to schistosomes, and immunologic measurement of schistosome antigens can be used to detect, and thus diagnose, active infections. All three areas contribute to the public health response to human schistosome infections.

Immunopathological study of parasitic cholangitis in cetaceans

This paper describes the immunophenotype of cellular inflammatory infiltrates in chronic cholangitis in six common dolphins (Delphinus delphis), four striped dolphins (Stenella coeruleoalba), three Atlantic spotted dolphins (Stenella frontalis) and one pygmy sperm whale (Kogia Breviceps) found stranded along the coasts of the Canary Islands (Spain). A panel of 5 antibodies previously tested in dolphins (anti-CD3, -IgG, -MHC class II, -S100 protein and -lysozyme) were used. The present work also reports cross reactivity with dolphin antigens of two antibodies not used to date in dolphins (anti-mouse iNOS and anti-mouse Foxp3). The most common type of cholangitis found was chronic granulomatous cholangitis, associated with the presence of the parasite Campula spp., or its eggs in bile ducts. The cellular composition of the hepatic inflammatory infiltrate associated to chronic parasitic cholangitis was closely similar to that found in the cortex of control lymph nodes, including the presence of S100(+) and MHC class II(+) dendritic-like cells in lymphoid follicles and interfollicular areas. Only occasional macrophages expressed iNOS, whereas Foxp3(+) lymphocytes were not found in any of the lesions described in the different types of cholangitis.

Modulation of innate antigen-presenting cell function by pre-patent schistosome infection

Schistosomes are intravascular helminths that infect over 200 million people worldwide. Deposition of eggs by adult schistosomes stimulates Th2 responses to egg antigens and induces granulomatous pathology that is a hallmark of schistosome infection. Paradoxically, schistosomes require host immune function for their development and reproduction and for egress of parasite eggs from the host. To identify potential mechanisms by which immune cells might influence parasite development prior to the onset of egg production, we assessed immune function in mice infected with developing schistosomes. We found that pre-patent schistosome infection is associated with a loss of T cell responsiveness to other antigens and is due to a diminution in the ability of innate antigen-presenting cells to stimulate T cells. Diminution of stimulatory capacity by schistosome worms specifically affected CD11b⁺ cells and did not require concomitant adaptive responses. We could not find evidence for production of a diffusible inhibitor of T cells by innate cells from infected mice. Rather, inhibition of T cell responsiveness by accessory cells required cell contact and only occurred when cells from infected mice outnumbered competent APCs by more than 3∶1. Finally, we show that loss of T cell stimulatory capacity may in part be due to suppression of IL-12 expression during pre-patent schistosome infection. Modulation of CD4⁺ T cell and APC function may be an aspect of host immune exploitation by schistosomes, as both cell types influence parasite development during pre-patent schistosome infection.

The disease schistosomiasis is caused by a parasitic blood fluke found mainly in the tropics and subtropics and affects over 200 million people worldwide. Using mice to model human schistosome infection, our previous studies showed that schistosome development in the infected host is linked to host immune function, such that parasite development is impaired in hosts with immunological deficiencies. CD4⁺ T cells and cells of the monocyte/macrophage lineage are two types of immune cells that are involved in modulating schistosome development. In this study, we examined immune function in mice infected with developing schistosomes, to gain insights into how immune cells might influence parasite development. We found evidence of broad-spectrum suppression of CD4⁺ T cell responses during early schistosome infection. We also show that the loss of T cell responsiveness is due to impairment of T cell stimulation by CD11b⁺ cells. These findings suggest that exploitation of CD4⁺ T cells and monocytes/macrophages by schistosomes may involve parasite modification of the function of these cells.

The application of probiotic fermented milks in cancer and intestinal inflammation

Lactic acid bacteria are present in many foods such as yoghurt and are frequently used as probiotics to improve some biological functions of the host. Many researchers have evaluated the effects of yoghurt and lactic acid bacteria against diseases such as cancer and intestinal inflammation. The preventive effect of probiotics on intestinal carcinogenesis may be associated with changes in the intestinal microbiota, suppressing the growth of bacteria that convert procarcinogens into carcinogens. Other mechanisms could be related to the immune response modulation and have been evaluated using milks fermented with lactic acid bacteria in chemically induced colon cancer and hormone-dependent breast cancer models. We demonstrated, using a murine colon cancer model, that yoghurt consumption inhibited tumour growth by decreasing the inflammatory response by increasing IL-10-secreting cells, cellular apoptosis and diminishing procarcinogenic enzymes. Milk fermented with Lactobacillus helveticus R389 delayed breast tumour growth by decreasing IL-6 and increasing IL-10 in serum and in the mammary glands and tumour-infiltrating immune cells. Previous results obtained with yoghurt administration in a colon cancer model led us to analyse its effect on a trinitrobenzenesulfonic acid-induced intestinal inflammation model in mice. Yoghurt was able to attenuate the symptoms of acute inflammation by reducing inflammatory cytokines, and increasing regulatory cytokine IL-10-producing cells, leading to desirable changes of the intestinal microbiota. It was demonstrated, by using murine models, that the consumption of fermented milks can modulate the immune system and can maintain it in a state of surveillance, which could affront different pathologies such as cancer and intestinal inflammation.

Arginase I suppresses IL-12/IL-23p40-driven intestinal inflammation during acute schistosomiasis

Alternatively activated macrophages prevent lethal intestinal pathology caused by worm ova in mice infected with the human parasite Schistosoma mansoni through mechanisms that are currently unclear. This study demonstrates that arginase I (Arg I), a major product of IL-4- and IL-13-induced alternatively activated macrophages, prevents cachexia, neutrophilia, and endotoxemia during acute schistosomiasis. Specifically, Arg I-positive macrophages promote TGF-beta production and Foxp3 expression, suppress Ag-specific T cell proliferation, and limit Th17 differentiation. S. mansoni-infected Arg I-deficient bone marrow chimeras develop a marked accumulation of worm ova within the ileum but impaired fecal egg excretion compared with infected wild-type bone marrow chimeras. Worm ova accumulation in the intestines of Arg I-deficient bone marrow chimeras was associated with intestinal hemorrhage and production of molecules associated with classical macrophage activation (increased production of IL-6, NO, and IL-12/IL-23p40), but whereas inhibition of NO synthase-2 has marginal effects, IL-12/IL-23p40 neutralization abrogates both cachexia and intestinal inflammation and reduces the number of ova within the gut. Thus, macrophage-derived Arg I protects hosts against excessive tissue injury caused by worm eggs during acute schistosomiasis by suppressing IL-12/IL-23p40 production and maintaining the Treg/Th17 balance within the intestinal mucosa.

Nitric oxide and respiratory helminthic diseases

Nitric oxide (NO) is a very simple molecule that displays very important functions both in helminths (mainly those involved in respiratory pathology) and in mammalian hosts. In this paper we review four issues related to interaction of NO and lung helminthic diseases. Firstly, we evaluated data available on the NO synthesis and release by helminths and their biological role. Next, we summarized the effect of antigens obtained from different phases of the biological cycle on NO production by host mammalian cells (mainly from human sources). Thirdly, we revised the evaluation of NO on the biological activities and/or the viability of respiratory helminths. Lastly, the deleterious consequences of increased production of NO during helminthic human infection are detailed.

IL-4(-/-) mice with lethal Mesocestoides corti infections--reduced Th2 cytokines and alternatively activated macrophages

Protection against Mesocestoides corti, a cestode that invades vital organs, is dependent on the production of IL-4, as IL-4(-/-) mice were found to have higher parasite burdens when compared with wild-type mice. The goal of this study was to investigate the role of IL-4 in immunity to M. corti, focusing on the immunological profile and on potential mediators of pathology. IL-4(-/-) mice infected with M. corti showed 100% mortality by 32 days, whereas wild-type mice survived for approximately 1 year. Parasite burdens were significantly increased in the liver, peritoneal, and thoracic cavities of IL-4(-/-) mice, associated with impaired recruitment of inflammatory cells and a reduction in monocytes and macrophages. IL-5 production by splenocytes and expression in liver tissue was decreased in infected IL-4(-/-) mice compared with wild-type mice. In contrast, IL-4(-/-) mice produced increased amounts of IFNgamma and TNFalpha. Alternatively activated macrophages were a major feature of liver granulomas in wild-type mice evidenced by Arginase I expression, while livers from infected IL-4(-/-) mice showed impaired alternative macrophage activation without increased classical macrophage activation. Thus, lethality during M. corti infection of IL-4(-/-) mice is associated with decreased Th2 cytokines, increased Th1 cytokines and impairment of alternatively activated macrophages.

Protection from EAE by IL-4Ralpha(-/-) macrophages depends upon T regulatory cell involvement

The administration of Th2 cytokines or immune deviation to a Th2 phenotypic response has been shown to protect against the autoimmune pathology of experimental autoimmune encephalomyelitis (EAE). To better understand the function of Th2 cytokines in the induction stage of EAE in the absence of an overt Th2 response, we immunized IL-4 receptor alpha-deficient (IL-4Ralpha(-/-)) mice, which are unable to respond to either IL-4 or IL-13. Contrary to expectations, mice lacking IL-4Ralpha had a lower incidence of EAE and a delayed onset compared to WT BALB/c mice; however, this delay did not correlate to an alteration in the Th1/Th17 cytokine balance. Instead, IL-4Ralpha-responsive macrophages were essential promoters of disease as macrophage-specific IL-4Ralpha-deficient (LysM(cre)IL-4Ralpha(-/lox)) mice were protected from EAE. The protection afforded by IL-4Ralpha-deficiency was not due to IL-10-, IFN-gamma-, NO- or IDO-mediated suppression of T-cell responses but was dependent upon the presence of regulatory T cells (Tregs). This investigation highlights the importance of macrophages and Tregs in regulating central nervous system inflammation and demonstrates that macrophages activated in the absence of Th2 cytokines can promote disease suppression by Tregs.

Preliminary results on interleukin-4 and interleukin-10 cytokine production in malnourished, inducible nitric oxide synthase-deficient mice with schistosomiasis mansoni infection

Schistosoma mansoni infected C57Bl/6 inducible nitric oxide synthase (iNOS)-deficient and non-deficient malnourished mice, both fed a balanced controlled diet were studied. Interleukins, IL-4 and IL-10 responses to soluble egg antigens (SEA) 90 days after infection, were determined. Our results suggest that in iNOS deficient, malnourished mice, 90 days after of infection, nitric oxide has a downregulating effect on IL-4 and IL-10 production. We are currently investigating the biological significance of these findings.

TH1-dominant granulomatous pathology does not inhibit fibrosis or cause lethality during murine schistosomiasis

Schistosoma mansoni egg-induced inflammation is accompanied by TH2 cell polarization and development of fibrotic granulomas in host tissue. The interleukin (IL)-4 receptor alpha (IL-4Ralpha), which mediates IL-4 and IL-13 signaling, is essential for granulomatous pathology through a putative CD4+ T-cell-dependent mechanism. In this study, we asked whether CD4+ T-cell-specific IL-4Ralpha-deficient mice (Lck(Cre)IL-4Ralpha(-/lox)) developed granulomas and egg-driven collagen production. Although eosinophilia and goblet cell hyperplasia were impaired in Lck(Cre)IL-4Ralpha(-/lox) mice, there was no reduction in size or collagen content of lung and liver granulomas. The lack of CD4+ T-cell IL-4Ralpha expression caused significant increases in interferon-gamma-producing cells, inducible nitric-oxide synthetase production, and hepatic damage, compared with similarly infected wild-type mice. Interestingly, this TH1-associated liver injury did not lead to premature mortality in this strain. Instead, lower levels of serum endotoxin in Lck(Cre)IL-4Ralpha(-/lox) mice suggest that intestinal barrier function may be the dominant factor for survival during natural infection.

Alternative macrophage activation is essential for survival during schistosomiasis and downmodulates T helper 1 responses and immunopathology

Macrophage/neutrophil-specific IL-4 receptor alpha-deficient mice (LysM(Cre)IL-4Ralpha(-/flox)) were generated to understand the role of IL-4/IL-13 responsive myeloid cells during Type 2 immune responses. LysM(Cre)IL-4Ralpha(-/flox) mice developed protective immunity against Nippostrongylus brasiliensis accompanied by T(H)2 development and goblet cell hyperplasia. In contrast, LysM(Cre)IL-4Ralpha(-/flox) mice were extremely susceptible to Schistosoma mansoni infection with 100% mortality during acute infection. Mortality was not dependent on neutrophils and occurred in the presence of T(H)2/Type 2 responses, granuloma formation, and egg-induced fibrosis. Death was associated with increased T(H)1 cytokines, hepatic and intestinal histopathology, increased NOS-2 activity, impaired egg expulsion, and sepsis. IL-10 was not able to compensate for the absence of IL-4/IL-13-activated alternative macrophages. Together, this shows that alternative macrophages are essential during schistosomiasis for protection against organ injury through downregulation of egg-induced inflammation.

Both interleukin-4 (IL-4) and IL-4 receptor alpha signaling contribute to the development of hepatic granulomas with optimal antileishmanial activity

The roles of interleukin-4 (IL-4) and IL-13 in the regulation of immunity to Leishmania donovani infection are still poorly understood. Here we show that the increased parasite load observed in IL-4(-/-) and IL-4 receptor alpha(-/-) mice correlates with retarded granuloma maturation and antileishmanial activity and that the increased parasite load observed in IL-4 receptor alpha(-/-) mice correlates with increased NOS2 expression and decreased serum gamma interferon levels. IL-4 and IL-13 appear to play little role in regulating collagen deposition in L. donovani-induced granulomas.

Overexpression of interleukin-4 in lungs of mice impairs elimination of Histoplasma capsulatum

Protection against the pathogenic fungus Histoplasma capsulatum requires Th1 cytokines. Since interleukin-4 (IL-4) can inhibit both Th1 cytokine production and activity, we examined the effects of overproduction of IL-4 in the lung on the course of pulmonary histoplasmosis. IL-4 lung transgenic mice manifested a higher fungal burden in their lungs, but not spleens, compared to wild-type infected controls. Despite the higher burden, the transgenic animals were ultimately capable of controlling infection. The adverse effects of IL-4 on H. capsulatum elimination were not observed during the early phase of infection (days 1 to 3) but were maximal at day 7 postinfection, prior to the induction of cell-mediated immunity. Analysis of total body and lung cytokine levels revealed that gamma interferon and tumor necrosis factor alpha production were not inhibited in the presence of excess IL-4. Our results with transgenic mice were supported by additional in vivo studies in which allergen induction of pulmonary IL-4 was associated with delayed clearance of H. capsulatum yeast and increased fungal burden. These findings demonstrate that excess production of endogenous IL-4 modulates protective immunity to H. capsulatum by delaying clearance of the organism but does not prevent the generation of a Th1 response that ultimately controls infection.

Experimental models of Schistosoma mansoni infection

Experimental models of Schistosoma mansoni infections in mammals have contributed greatly to our understanding of the pathology and pathogenesis of infection. We consider here hepatic and extrahepatic disease in models of acute and chronic infection. Experimental schistosome infections have also contributed more broadly to our understanding of granulomatous inflammation and our understanding of Th1 versus Th2 related inflammation and particularly to Th2-mediated fibrosis of the liver.