Macrophage-migration Inhibitory Factor (MIF) homologues in the host-parasite interaction.

The ability of filarial parasites to persist in an immunological competent host, has led to the suggestion that they have evolved specific measures to counter immune defences. Filarial nematodes produce and secrete excretory-secretory (ES) products, some of which have been described to have a potential role in immune evasion. As part of these ES products, two homologues of the mammalian cytokine macrophage-migration inhibitory factor (MIF) have been described from the filarial nematode Brugia malayi, Bm-MIF-1 and Bm-MIF-2. Mammalian MIF is a widely distributed protein constitutively expressed in many immune and non-immune cell types. Although firstly characterised by its ability to stop migration of peritoneal macrophages, it has now been shown to play an important role during different inflammation processes. The main aim of this study is to elucidate the role of Brugia MIF homologues and their relation with the mammalian cytokine. This thesis studies the effect of both filarial and host MIF homologues on two major immune cell types, macrophages and dendritic cells (DC). We found that both Brugia and mouse-MIF synergise with IL-4 to activate macrophages to an alternative phenotype, by enhancing expression of IL-4-induced alternative activation markers Arginase-1, Ym-1 and the macrophage Mannose Receptor. MIF also synergises with IL-4 to render macrophages suppressive, an important outcome during filarial infection. Additionally we found that MIF homologues induce IL-4Ra expression, suggesting a mechanism by which MIF enhances IL-4 activation. We showed that filarial and mouse MIF homologues differ in their capacity to activate bone marrow-derived immature dendritic cells. Mouse-MIF up-regulates MHC-II and CD40 expression and induces pro-inflammatory cytokine production after overnight treatment. On the other hand Bm-MIF-2 induces low levels of cytokine production but does not up-regulate activation markers, and Bm-MIF-1 failed to activate DC. Furthermore, we demonstrate that filarial MIF homologues impair DC differentiation from bone marrow precursors. While bone marrow cells cultured in the presence of GM-CSF, with or without mouse-MIF, differentiate into CD11c+ DC, addition of Bm-MIF-2 to the culture media impairs differentiation arresting the cells in an undifferentiated phenotype characterised by the expression of myeloid and granulocyte markers CD11b and GR1. Finally, using an in vivo model where we implant Brugia malayi parasites in the peritoneal cavity of mice, we observed that host MIF does not play an essential role in the activation of macrophages by adult parasites as macrophages form MIF deficient mice present the same phenotype as their wild type counterparts

Heterologous expression of the filarial nematode alt gene products reveals their potential to inhibit immune function

BACKGROUND: Parasites exploit sophisticated strategies to evade host immunity that require both adaptation of existing genes and evolution of new gene families. We have addressed this question by testing the immunological function of novel genes from helminth parasites, in which conventional transgenesis is not yet possible. We investigated two such novel genes from Brugia malayi termed abundant larval transcript (alt), expression of which reaches ~5% of total transcript at the time parasites enter the human host. RESULTS: To test the hypothesis that ALT proteins modulate host immunity, we adopted an alternative transfection strategy to express these products in the protozoan parasite Leishmania mexicana. We then followed the course of infection in vitro in macrophages and in vivo in mice. Expression of ALT proteins, but not a truncated mutant, conferred greater infectivity of macrophages in vitro, reaching 3-fold higher parasite densities. alt-transfected parasites also caused accelerated disease in vivo, and fewer mice were able to clear infection of organisms expressing ALT. alt-transfected parasites were more resistant to IFN-γ-induced killing by macrophages. Expression profiling of macrophages infected with transgenic L. mexicana revealed consistently higher levels of GATA-3 and SOCS-1 transcripts, both associated with the Th2-type response observed in in vivo filarial infection. CONCLUSION: Leishmania transfection is a tractable and informative approach to determining immunological functions of single genes from heterologous organisms. In the case of the filarial ALT proteins, our data suggest that they may participate in the Th2 bias observed in the response to parasite infection by modulating cytokine-induced signalling within immune system cells

Alternatively Activated Macrophages Elicited by Helminth Infection Can Be Reprogrammed to Enable Microbial Killing

The prime function of classically activated macrophages (activated by Th1-type signals, such as IFN-γ) is microbial destruction. Alternatively activated macrophages (activated by Th2 cytokines, such as IL-4 and IL-13) play important roles in allergy and responses to helminth infection. We utilize a murine model of filarial infection, in which adult nematodes are surgically implanted into the peritoneal cavity of mice, as an in vivo source of alternatively activated macrophages. At 3 wk postinfection, the peritoneal exudate cell population is dominated by macrophages, termed nematode-elicited macrophages (NeMφ), that display IL-4-dependent features such as the expression of arginase 1, RELM-α (resistin-like molecule α), and Ym1. Since increasing evidence suggests that macrophages show functional adaptivity, the response of NeMφ to proinflammatory Th1-activating signals was investigated to determine whether a switch between alternative and classical activation could occur in macrophages differentiated in an in vivo infection setting. Despite the long-term exposure to Th2 cytokines and antiinflammatory signals in vivo, we found that NeMφ were not terminally differentiated but could develop a more classically activated phenotype in response to LPS and IFN-γ. This was reflected by a switch in the enzymatic pathway for arginine metabolism from arginase to inducible NO synthase and the reduced expression of RELM-α and Ym1. Furthermore, this enabled NeMφ to become antimicrobial, as LPS/IFN-γ-treated NeMφ produced NO that mediated killing of Leishmania mexicana. However, the adaptation to antimicrobial function did not extend to key regulatory pathways, such as IL-12 production, which remained unaltered

MIF homologues from a filarial nematode parasite synergize with IL-4 to induce alternative activation of host macrophages

Macrophage migration inhibitory factor (MIF) is a highly conserved cytokine considered to exert wide-ranging, proinflammatory effects on the immune system. Recently, members of this gene family have been discovered in a number of invertebrate species, including parasitic helminths. However, chronic helminth infections are typically associated with a Th2-dominated, counter-inflammatory phenotype, in which alternatively activated macrophages (AAMs) are prominent. To resolve this apparent paradox, we have analyzed the activity of two helminth MIF homologues from the filarial nematode Brugia malayi, in comparison with the canonical MIF from the mouse. We report that murine MIF (mMIF) and Brugia MIF proteins induce broadly similar effects on bone marrow-derived mouse macrophages, eliciting a measured release of proinflammatory cytokines. In parallel, MIF was found to induce up-regulation of IL-4R on macrophages, which when treated in vitro with MIF in combination with IL-4, expressed markers of alternative activation [arginase, resistin-like molecule α (RELM-α) or found in inflammatory zone 1, Ym-1, murine macrophage mannose receptor] and differentiated into functional AAMs with in vitro-suppressive ability. Consistent with this finding, repeated in vivo administration of Brugia MIF induced expression of alternative macrophage activation markers. As mMIF did not induce RELM-α or Ym-1 in vivo, alternative activation may require components of the adaptive immune response to Brugia MIF, such as the production of IL-4. Hence, MIF may accentuate macrophage activation according to the polarity of the environment, thus promoting AAM differentiation in the presence of IL-4-inducing parasitic helminths

Macrophage-migration Inhibitory Factor (MIF) homologues in the host-parasite interaction

The ability of filarial parasites to persist in an immunological competent host, has led to the suggestion that they have evolved specific measures to counter immune defences. Filarial nematodes produce and secrete excretory-secretory (ES) products, some of which have been described to have a potential role in immune evasion. As part of these ES products, two homologues of the mammalian cytokine macrophage-migration inhibitory factor (MIF) have been described from the filarial nematode Brugia malayi, Bm-MIF-1 and Bm-MIF-2. Mammalian MIF is a widely distributed protein constitutively expressed in many immune and non-immune cell types. Although firstly characterised by its ability to stop migration of peritoneal macrophages, it has now been shown to play an important role during different inflammation processes. The main aim of this study is to elucidate the role of Brugia MIF homologues and their relation with the mammalian cytokine. This thesis studies the effect of both filarial and host MIF homologues on two major immune cell types, macrophages and dendritic cells (DC). We found that both Brugia and mouse-MIF synergise with IL-4 to activate macrophages to an alternative phenotype, by enhancing expression of IL-4-induced alternative activation markers Arginase-1, Ym-1 and the macrophage Mannose Receptor. MIF also synergises with IL-4 to render macrophages suppressive, an important outcome during filarial infection. Additionally we found that MIF homologues induce IL-4Ra expression, suggesting a mechanism by which MIF enhances IL-4 activation. We showed that filarial and mouse MIF homologues differ in their capacity to activate bone marrow-derived immature dendritic cells. Mouse-MIF up-regulates MHC-II and CD40 expression and induces pro-inflammatory cytokine production after overnight treatment. On the other hand Bm-MIF-2 induces low levels of cytokine production but does not up-regulate activation markers, and Bm-MIF-1 failed to activate DC. Furthermore, we demonstrate that filarial MIF homologues impair DC differentiation from bone marrow precursors. While bone marrow cells cultured in the presence of GM-CSF, with or without mouse-MIF, differentiate into CD11c+ DC, addition of Bm-MIF-2 to the culture media impairs differentiation arresting the cells in an undifferentiated phenotype characterised by the expression of myeloid and granulocyte markers CD11b and GR1. Finally, using an in vivo model where we implant Brugia malayi parasites in the peritoneal cavity of mice, we observed that host MIF does not play an essential role in the activation of macrophages by adult parasites as macrophages form MIF deficient mice present the same phenotype as their wild type counterparts.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Suicides in the Nenets Autonomous Okrug, Russia.

This is a study of suicides in the Nenets Autonomous Okrug (NAO), a region with a large proportion of indigenous Nenets. To our knowledge, this is the first study investigating the problem of suicide in the indigenous and non-indigenous populations of the Russian Arctic. Our study aim was to assess suicide rates in the indigenous and non-indigenous populations of the NAO, as well as the socio-demographic characteristics, differences in suicide methods, seasonal variations, and the potential role of alcohol in suicides in these two populations. We conducted a retrospective, population-based mortality study of suicides in the NAO, using data from the autopsy reports of suicide victims in the region in 2002-2012. Socio-demographic data were obtained from passports and medical records, and then linked to total population data from the 2002 and 2010 censuses. Suicide rates for indigenous Nenets and the non-indigenous population were calculated according to different socio-demographic characteristics, and corresponding relative risks for these two populations were compared. Variations in suicide methods, seasonal variations, and variations in the day of the week suicides occurred in the NAO were compared with national data from the Russian Federal Statistics Service (Rosstat). Data on the presence of alcohol in the blood and blood alcohol content in suicide cases from the NAO were compared with data from the neighboring Arkhangelsk Oblast. Suicide rates in the NAO were higher than corresponding national figures. Suicide rates were higher among the indigenous Nenets than the non-indigenous population, and were associated with different socio-demographic characteristics. We showed different relative frequencies of suicide by hanging, cutting, and firearm, as well as differences in suicide occurrence by month and day of the week in the NAO when compared with Russia as a whole. The study results and conclusions may be useful to create suicide prevention programs that are targeted to different population groups in the Russian Arctic. Key words: Nenets Autonomous Okrug (NAO), Arkhangelsk Oblast (AO), suicide rates, relative risks, person-years, indigenous Nenets, suicide methods, seasonality, alcohol

Heterologous expression of the filarial nematode gene products reveals their potential to inhibit immune function-1

<p><b>Copyright information:</b></p><p>Taken from "Heterologous expression of the filarial nematode gene products reveals their potential to inhibit immune function"</p><p>BMC Biology 2005;3():8-8.</p><p>Published online 23 Mar 2005</p><p>PMCID:PMC555940.</p><p>Copyright © 2005 Gomez-Escobar et al; licensee BioMed Central Ltd.</p>ith anti-serum or anti-ALT-1 antibody. Cloned transfected and transfected fixed parasites were incubated with an anti-ALT-1 antibody, which binds to both ALT-1 and ALT-2, and detected with an anti-mouse-FITC secondary antibody. FACS analysis of transfected promastigotes of . Fixed promastigotes were stained, without permeabilization, with anti-ALT-1 antibody and analysed by FACS. -transfected ; -transfected ; wild-type . Positive cells are those within the gate (M1) set above the threshold defined by reactivity of transfected parasites stained with normal mouse serum . Multiplication of transfectants within macrophages. -transformed wild-type amastigotes or transfected amastigotes were added to bone marrow-derived macrophages from CBA mice at a ratio of 10 parasites per macrophage. After 24 hours at 34°C the infected macrophages were observed by microscopy