RESUMO
Eukaryotic high-mobility-group-box (HMGB) proteins are nuclear factors involved in chromatin remodeling and transcription regulation. When released into the extracellular milieu, HMGB1 acts as a proinflammatory cytokine that plays a central role in the pathogenesis of several immune-mediated inflammatory diseases. We found that the Plasmodium genome encodes two genuine HMGB factors, Plasmodium HMGB1 and HMGB2, that encompass, like their human counterparts, a proinflammatory domain. Given that these proteins are released from parasitized red blood cells, we then hypothesized that Plasmodium HMGB might contribute to the pathogenesis of experimental cerebral malaria (ECM), a lethal neuroinflammatory syndrome that develops in C57BL/6 (susceptible) mice infected with Plasmodium berghei ANKA and that in many aspects resembles human cerebral malaria elicited by P. falciparum infection. The pathogenesis of experimental cerebral malaria was suppressed in C57BL/6 mice infected with P. berghei ANKA lacking the hmgb2 gene (Δhmgb2 ANKA), an effect associated with a reduction of histological brain lesions and with lower expression levels of several proinflammatory genes. The incidence of ECM in pbhmgb2-deficient mice was restored by the administration of recombinant PbHMGB2. Protection from experimental cerebral malaria in Δhmgb2 ANKA-infected mice was associated with reduced sequestration in the brain of CD4(+) and CD8(+) T cells, including CD8(+) granzyme B(+) and CD8(+) IFN-γ(+) cells, and, to some extent, neutrophils. This was consistent with a reduced parasite sequestration in the brain, lungs, and spleen, though to a lesser extent than in wild-type P. berghei ANKA-infected mice. In summary, Plasmodium HMGB2 acts as an alarmin that contributes to the pathogenesis of cerebral malaria.
Assuntos
Proteína HMGB2/metabolismo , Malária Cerebral/patologia , Malária Cerebral/parasitologia , Plasmodium berghei/patogenicidade , Fatores de Virulência/metabolismo , Animais , Encéfalo/patologia , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/imunologia , Citocinas/biossíntese , Modelos Animais de Doenças , Deleção de Genes , Técnicas de Inativação de Genes , Proteína HMGB2/genética , Histocitoquímica , Camundongos Endogâmicos C57BL , Neutrófilos/imunologia , Plasmodium berghei/genética , Virulência , Fatores de Virulência/genéticaRESUMO
Epigenetic factors such as histone methylation control the developmental progression of malaria parasites during the complex life cycle in the human host. We investigated Plasmodium falciparum histone lysine methyltransferases as a potential target class for the development of novel antimalarials. We synthesized a compound library based upon a known specific inhibitor (BIX-01294) of the human G9a histone methyltransferase. Two compounds, BIX-01294 and its derivative TM2-115, inhibited P. falciparum 3D7 parasites in culture with IC(50) values of ~100 nM, values at least 22-fold more potent than their apparent IC(50) toward two human cell lines and one mouse cell line. These compounds irreversibly arrested parasite growth at all stages of the intraerythrocytic life cycle. Decrease in parasite viability (>40%) was seen after a 3-h incubation with 1 µM BIX-01294 and resulted in complete parasite killing after a 12-h incubation. Additionally, mice with patent Plasmodium berghei ANKA strain infection treated with a single dose (40 mg/kg) of TM2-115 had 18-fold reduced parasitemia the following day. Importantly, treatment of P. falciparum parasites in culture with BIX-01294 or TM2-115 resulted in significant reductions in histone H3K4me3 levels in a concentration-dependent and exposure time-dependent manner. Together, these results suggest that BIX-01294 and TM2-115 inhibit malaria parasite histone methyltransferases, resulting in rapid and irreversible parasite death. Our data position histone lysine methyltransferases as a previously unrecognized target class, and BIX-01294 as a promising lead compound, in a presently unexploited avenue for antimalarial drug discovery targeting multiple life-cycle stages.
Assuntos
Antimaláricos/farmacologia , Azepinas/farmacologia , Histona-Lisina N-Metiltransferase/antagonistas & inibidores , Plasmodium falciparum/efeitos dos fármacos , Quinazolinas/farmacologia , Sequência de Aminoácidos , Animais , Antimaláricos/química , Azepinas/química , Western Blotting , Células Cultivadas , Relação Dose-Resposta a Droga , Eritrócitos/parasitologia , Histona Metiltransferases , Histona-Lisina N-Metiltransferase/genética , Histona-Lisina N-Metiltransferase/metabolismo , Histonas/metabolismo , Humanos , Estágios do Ciclo de Vida , Lisina/metabolismo , Malária/tratamento farmacológico , Malária/parasitologia , Metilação/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Parasitemia/parasitologia , Parasitemia/prevenção & controle , Plasmodium berghei/efeitos dos fármacos , Plasmodium berghei/crescimento & desenvolvimento , Plasmodium falciparum/crescimento & desenvolvimento , Quinazolinas/química , Homologia de Sequência de AminoácidosRESUMO
Antibodies normally do not cross the blood-brain barrier (BBB) and cannot bind an intracellular cerebral antigen. We demonstrate here for the first time that a new class of antibodies can cross the BBB without treatment. Camelids produce native homodimeric heavy-chain antibodies, the paratope being composed of a single-variable domain called VHH. Here, we used recombinant VHH directed against human glial fibrillary acidic protein (GFAP), a specific marker of astrocytes. Only basic VHHs (e.g., pI=9.4) were able to cross the BBB in vitro (7.8 vs. 0% for VHH with pI=7.7). By intracarotid and intravenous injections into live mice, we showed that these basic VHHs are able to cross the BBB in vivo, diffuse into the brain tissue, penetrate into astrocytes, and specifically label GFAP. To analyze their ability to be used as a specific transporter, we then expressed a recombinant fusion protein VHH-green fluorescent protein (GFP). These "fluobodies" specifically labeled GFAP on murine brain sections, and a basic variant (pI=9.3) of the fusion protein VHH-GFP was able to cross the BBB and to label astrocytes in vivo. The potential of VHHs as diagnostic or therapeutic agents in the central nervous system now deserves attention.
Assuntos
Astrócitos/metabolismo , Barreira Hematoencefálica/metabolismo , Encéfalo/metabolismo , Proteína Glial Fibrilar Ácida/metabolismo , Anticorpos de Domínio Único/metabolismo , Animais , Astrocitoma/metabolismo , Linhagem Celular , Linhagem Celular Tumoral , Ensaio de Imunoadsorção Enzimática , Feminino , Imunofluorescência , Proteína Glial Fibrilar Ácida/genética , Proteína Glial Fibrilar Ácida/imunologia , Humanos , Imuno-Histoquímica , Camundongos , Camundongos Endogâmicos C57BL , Mutagênese Sítio-Dirigida , Plasmodium berghei/patogenicidade , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Anticorpos de Domínio Único/genética , Anticorpos de Domínio Único/imunologiaRESUMO
An immunomodulatory role of arthropod saliva has been well documented, but evidence for an effect on Plasmodium sp. infectiousness remains controversial. Mosquito saliva may orient the immune response toward a Th2 profile, thereby priming a Th2 response against subsequent antigens, including Plasmodium. Orientation toward a Th1 versus a Th2 profile promotes IgG and IgE proliferation, respectively, where the former is crucial for the development of an efficient antiparasite immune response. Here we assessed the direct effect of mosquito bites on the density of Plasmodium falciparum asexual parasites and the prevalence of gametocytes in chronic, asymptomatic infections in a longitudinal cohort study of seasonal transmission. We additionally correlated these parasitological measures with IgE and IgG antiparasite and anti-salivary gland extract titers. The mosquito biting density was positively correlated with the asexual parasite density but not asexual parasite prevalence and was negatively correlated with gametocyte prevalence. Individual anti-salivary gland IgE titers were also negatively correlated with gametocyte carriage and were strongly positively correlated with antiparasite IgE titers, consistent with the hypothesis that mosquito bites predispose individuals to develop an IgE antiparasite response. We provide evidence that mosquito bites have an impact on asymptomatic infections and differentially so for the production of asexual and sexual parasites. An increased research focus on the immunological impact of mosquito bites during asymptomatic infections is warranted, to establish whether strategies targeting the immune response to saliva can reduce the duration of infection and the onward transmission of the parasite.
Assuntos
Culicidae/fisiologia , Imunoglobulina E/sangue , Imunoglobulina G/sangue , Mordeduras e Picadas de Insetos/complicações , Malária Falciparum/parasitologia , Plasmodium falciparum/fisiologia , Animais , Anticorpos Antiprotozoários/sangue , Doença Crônica , Estudos de Coortes , Culicidae/imunologia , Família , Perfilação da Expressão Gênica , Regulação da Expressão Gênica/imunologia , Humanos , Mordeduras e Picadas de Insetos/imunologia , Malária Falciparum/sangue , Malária Falciparum/epidemiologia , Malária Falciparum/imunologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Senegal/epidemiologiaRESUMO
BACKGROUND: Murine basophils can contribute to the T(H)2 polarization of the immune response by providing rapidly large amounts of IL-4, which suggests that pharmacologic downregulation of this cytokine might provide a strategy to attenuate pathologies associated with excessive production. OBJECTIVE: We examined a number of physiological and pharmacologic ligands of the organic cation transporter 3 (OCT3), a membrane carrier of biogenic amines, for their inhibitory effect on IL-4 production by basophils, selecting the most efficient compounds for in vivo evaluation in basophil-dependent experimental models. METHODS: IL-4 production by basophils isolated ex vivo or from bone marrow cultures was assessed in response to various stimuli with or without biogenic monoamines or pharmacologic analogs. Selected compounds were administered in vivo to examine their effect on levels of circulating IgE generated during a basophil-dependent T(H)2 response and on basophil activation in mice receiving IL-33. RESULTS: We found a drastic decrease in IL-4 production by stimulated basophils on exposure to serotonin (5-hydroxytryptamine [5-HT]) that is taken up by basophils through the specific high-affinity transporters serotonin transporter and the polyspecific, high-capacity organic cation transporter 3 (OCT3; or Slc22a3) but inhibits their function exclusively through the latter. This downregulation is likewise observed in vivo in response to 5-HT and other OCT3 ligands, as well as in human basophils sorted from PMBCs of nonatopic donors. CONCLUSIONS: We provide evidence for a new means of downregulating IL-4 production by basophils, both in vitro and in vivo, through OCT3 targeted by 5-HT and pharmacologic ligands.
Assuntos
Basófilos/imunologia , Imunoglobulina E/imunologia , Interleucina-4/imunologia , Proteínas de Transporte de Cátions Orgânicos/agonistas , Serotonina/imunologia , Células Th2/imunologia , Animais , Basófilos/metabolismo , Células da Medula Óssea/imunologia , Células da Medula Óssea/metabolismo , Células Cultivadas , Regulação para Baixo/efeitos dos fármacos , Regulação para Baixo/genética , Regulação para Baixo/imunologia , Feminino , Humanos , Imunoglobulina E/metabolismo , Interleucina-33 , Interleucina-4/biossíntese , Interleucina-4/genética , Interleucinas/imunologia , Interleucinas/farmacologia , Ligantes , Masculino , Camundongos , Camundongos Knockout , Proteínas de Transporte de Cátions Orgânicos/genética , Proteínas de Transporte de Cátions Orgânicos/imunologia , Proteínas de Transporte de Cátions Orgânicos/metabolismo , Serotonina/genética , Serotonina/metabolismo , Serotonina/farmacologia , Agonistas do Receptor de Serotonina/imunologia , Agonistas do Receptor de Serotonina/metabolismo , Agonistas do Receptor de Serotonina/farmacologia , Células Th2/metabolismoRESUMO
Infection with vector-borne pathogens starts with the inoculation of these pathogens during blood feeding. In endemic regions, the population is regularly bitten by naive vectors, implicating a permanent stimulation of the immune system by the vector saliva itself (pre-immune context). Comparatively, the number of bites received by exposed individuals from non-infected vectors is much higher than the bites from infected ones. Therefore, vector saliva and the immunological response in the skin may play an important role, so far underestimated, in the establishment of anti-pathogen immunity in endemic areas. Hence, the parasite biology and the disease pathogenesis in "saliva-primed" and "saliva-unprimed" individuals must be different. This integrated view on how the pathogen evolves within the host together with vector salivary components, which are known to be endowed with a variety of pharmacological and immunological properties, must remain the focus of any investigational study dealing with vector-borne diseases. Considering this three-way partnership, the host skin (immune system), the pathogen, and the vector saliva, the approach that consists in the validation of vector saliva as a source of molecular entities with anti-disease vaccine potential has been recently a subject of active and fruitful investigation. As an example, the vaccination with maxadilan, a potent vasodilator peptide extracted from the saliva of the sand fly Lutzomyia longipalpis, was able to protect against infection with various leishmanial parasites. More interestingly, a universal mosquito saliva vaccine that may potentially protect against a range of mosquito-borne infections including malaria, dengue, Zika, chikungunya and yellow fever. In this review, we highlight the key role played by the immunobiology of vector saliva in shaping the outcome of vector-borne diseases and discuss the value of studying diseases in the light of intimate cross talk among the pathogen, the vector saliva, and the host immune mechanisms.
RESUMO
Epigenetic post-translational modifications are essential for human malaria parasite survival and progression through its life cycle. Here, we present new functionalized suberoylanilide hydroxamic acid (SAHA) derivatives that chemically combine the pan-histone deacetylase inhibitor SAHA with the DNA methyltransferase inhibitor procainamide. A three- or four-step chemical synthesis was designed starting from cheap raw materials. Compared to the single drugs, the combined molecules showed a superior activity in Plasmodium and a potent inhibition against human HDAC6, exerting no cytotoxicity in human cell lines. These new compounds are fully active in multidrug-resistant Plasmodium falciparum Cambodian isolates. They target transmission of the parasite by inducing irreversible morphological changes in gametocytes and inhibiting exflagellation. The compounds are slow-acting and have an additive antimalarial effect in combination with fast-acting epidrugs and dihydroartemisinin. The lead compound decreases parasitemia in mice in a severe malaria model. Taken together, this novel fused molecule offers an affordable alternative to current failing antimalarial therapy.
Assuntos
Antimaláricos/farmacologia , Desacetilase 6 de Histona/antagonistas & inibidores , Inibidores de Histona Desacetilases/farmacologia , Ácidos Hidroxâmicos/farmacologia , Malária Falciparum/tratamento farmacológico , Plasmodium falciparum/efeitos dos fármacos , Procainamida/farmacologia , Antimaláricos/síntese química , Antimaláricos/química , Relação Dose-Resposta a Droga , Resistência a Múltiplos Medicamentos/efeitos dos fármacos , Desacetilase 6 de Histona/metabolismo , Inibidores de Histona Desacetilases/síntese química , Inibidores de Histona Desacetilases/química , Ácidos Hidroxâmicos/química , Estrutura Molecular , Procainamida/química , Relação Estrutura-AtividadeRESUMO
Malaria is the deadliest parasitic disease affecting over 200 million people worldwide. The increasing number of treatment failures due to multi-drug-resistant parasites in South-East Asia hinders the efforts for elimination. It is thus urgent to develop new antimalarials to contain these resistant parasites. Based on a previous report showing the presence of DNA methylation in Plasmodium, we generated new types of DNA methylation inhibitors against malaria parasites. The quinoline-quinazoline-based inhibitors kill parasites, including artemisinin-resistant field isolates adapted to culture, in the low nanomolar range. The compounds target all stages of the asexual cycle, including early rings, during a 6 h treatment period; they reduce DNA methylation in the parasite and show in vivo activity at 10 mg/kg. These potent inhibitors are a new starting point to develop fast-acting antimalarials that could be used in combination with artemisinins.
RESUMO
A hallmark of the host response to Plasmodium parasite is an inflammatory reaction characterized by elevated histaminemia levels. Since histamine, which acts through four different receptors and which synthesis is under the control of the histidine decarboxylase (HDC), is endowed with pro-inflammatory and immunosuppressive activities, we hypothesized that this vaso-active amine may participe to malaria pathogenesis. Combining genetic and pharmacologic approaches by using H1R(-/-), H2R(-/-), H3R(-/-), HDC(-/-) mice and H1R, H2R-, and H3R-antagonists, respectively, we found that cerebral malaria-associated pathogenetic processes such as blood brain barrier disruption, and T lymphocyte sequestration to cerebral vascular endothelium in mice were associated with histamine production. The identification of this novel inflammatory pathway and its implication in Plasmodium infection may lead to novel strategies to manipulate the anti-Plasmodium immune response and may provide new therapeutic tools to alleviate malaria disease.
Assuntos
Histamina/fisiologia , Malária/fisiopatologia , Receptores Histamínicos/fisiologia , Adulto , Animais , Basófilos/fisiologia , Barreira Hematoencefálica/fisiologia , Pré-Escolar , Histamina/sangue , Histamina/deficiência , Histidina Amônia-Liase/deficiência , Histidina Amônia-Liase/fisiologia , Interações Hospedeiro-Parasita , Humanos , Lactente , Malária Cerebral/fisiopatologia , Malária Falciparum/fisiopatologia , Mastócitos/fisiologia , Camundongos , Camundongos Knockout , Modelos Biológicos , Parasitemia/fisiopatologia , Plasmodium berghei , Receptores Histamínicos/deficiência , Receptores Histamínicos/genéticaRESUMO
Heterochromatin plays a central role in the process of immune evasion, pathogenesis, and transmission of the malaria parasite Plasmodium falciparum during blood stage infection. Here, we use ChIP sequencing to demonstrate that sporozoites from mosquito salivary glands expand heterochromatin at subtelomeric regions to silence blood-stage-specific genes. Our data also revealed that heterochromatin enrichment is predictive of the transcription status of clonally variant genes members that mediate cytoadhesion in blood stage parasites. A specific member (here called NF54varsporo) of the var gene family remains euchromatic, and the resultant PfEMP1 (NF54_SpzPfEMP1) is expressed at the sporozoite surface. NF54_SpzPfEMP1-specific antibodies efficiently block hepatocyte infection in a strain-specific manner. Furthermore, human volunteers immunized with infective sporozoites developed antibodies against NF54_SpzPfEMP1. Overall, we show that the epigenetic signature of var genes is reset in mosquito stages. Moreover, the identification of a strain-specific sporozoite PfEMP1 is highly relevant for vaccine design based on sporozoites.
Assuntos
Hepatócitos/imunologia , Proteínas de Protozoários/metabolismo , Esporozoítos/imunologia , AnimaisRESUMO
Mutant isoforms of the KIT or PDGF receptors expressed by gastrointestinal stromal tumors (GISTs) are considered the therapeutic targets for STI571 (imatinib mesylate; Gleevec), a specific inhibitor of these tyrosine kinase receptors. Case reports of clinical efficacy of Gleevec in GISTs lacking the typical receptor mutations prompted a search for an alternate mode of action. Here we show that Gleevec can act on host DCs to promote NK cell activation. DC-mediated NK cell activation was triggered in vitro and in vivo by treatment of DCs with Gleevec as well as by a loss-of-function mutation of KIT. Therefore, tumors that are refractory to the antiproliferative effects of Gleevec in vitro responded to Gleevec in vivo in an NK cell-dependent manner. Longitudinal studies of Gleevec-treated GIST patients revealed a therapy-induced increase in IFN-gamma production by NK cells, correlating with an enhanced antitumor response. These data point to a novel mode of antitumor action for Gleevec.
Assuntos
Inibidores Enzimáticos/farmacologia , Células Matadoras Naturais/metabolismo , Proteínas Tirosina Quinases/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-kit/genética , Proteínas Proto-Oncogênicas c-kit/metabolismo , Receptores Proteína Tirosina Quinases/metabolismo , Animais , Antineoplásicos/farmacologia , Benzamidas , Estudos de Casos e Controles , Técnicas de Cocultura , Células Dendríticas/efeitos dos fármacos , Células Dendríticas/metabolismo , Feminino , Neoplasias Gastrointestinais/tratamento farmacológico , Neoplasias Gastrointestinais/genética , Neoplasias Gastrointestinais/metabolismo , Neoplasias Gastrointestinais/patologia , Regulação Neoplásica da Expressão Gênica , Humanos , Mesilato de Imatinib , Interferon gama/efeitos dos fármacos , Interferon gama/metabolismo , Leucócitos Mononucleares/metabolismo , Estudos Longitudinais , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos SCID , Mutação , Ativação de Neutrófilo/efeitos dos fármacos , Piperazinas/farmacologia , Proteínas Proto-Oncogênicas c-kit/efeitos dos fármacos , Pirimidinas/farmacologia , Receptores Proteína Tirosina Quinases/efeitos dos fármacos , Receptores Proteína Tirosina Quinases/genética , Receptores do Fator de Crescimento Derivado de Plaquetas/efeitos dos fármacos , Receptores do Fator de Crescimento Derivado de Plaquetas/genética , Receptores do Fator de Crescimento Derivado de Plaquetas/metabolismo , Células Estromais/efeitos dos fármacosRESUMO
BACKGROUND: There is an increase of serum levels of IgE during Plasmodium falciparum infections in individuals living in endemic areas. These IgEs either protect against malaria or increase malaria pathogenesis. To get an insight into the exact role played by IgE in the outcome of P. falciparum infection, total IgE levels and functional anti-parasite IgE response were studied in children and adults, from two different endemic areas Gabon and India, exhibiting either uncomplicated malaria, severe non cerebral malaria or cerebral malaria, in comparison with control individuals. METHODOLOGY AND RESULTS: Blood samples were collected from controls and P. falciparum-infected patients before treatment on the day of hospitalization (day 0) in India and, in addition, on days 7 and 30 after treatment in Gabon. Total IgE levels were determined by ELISA and functional P. falciparum-specific IgE were estimated using a mast cell line RBL-2H3 transfected with a human Fcepsilon RI alpha-chain that triggers degranulation upon human IgE cross-linking. Mann Whitney and Kruskall Wallis tests were used to compare groups and the Spearman test was used for correlations. Total IgE levels were confirmed to increase upon infection and differ with level of transmission and age but were not directly related to the disease phenotype. All studied groups exhibited functional parasite-specific IgEs able to induce mast cell degranulation in vitro in the presence of P. falciparum antigens. Plasma IgE levels correlated with those of IL-10 in uncomplicated malaria patients from Gabon. In Indian patients, plasma IFN-gamma , TNF and IL-10 levels were significantly correlated with IgE concentrations in all groups. CONCLUSION: Circulating levels of total IgE do not appear to correlate with protection or pathology, or with anti-inflammatory cytokine pattern bias during malaria. On the contrary, the P. falciparum-specific IgE response seems to contribute to the control of parasites, since functional activity was higher in asymptomatic and uncomplicated malaria patients than in severe or cerebral malaria groups.
Assuntos
Anticorpos Antiprotozoários/sangue , Especificidade de Anticorpos , Imunoglobulina E/sangue , Malária Cerebral/imunologia , Malária Falciparum/imunologia , Plasmodium falciparum/imunologia , Adolescente , Adulto , Idoso , Animais , Linhagem Celular , Criança , Pré-Escolar , Feminino , Gabão , Humanos , Índia , Lactente , Malária Cerebral/parasitologia , Malária Cerebral/fisiopatologia , Malária Falciparum/parasitologia , Malária Falciparum/fisiopatologia , Masculino , Mastócitos , Pessoa de Meia-Idade , Índice de Gravidade de DoençaRESUMO
Infection with vector-borne pathogens starts with the inoculation of these pathogens during blood feeding. In endemic regions, the population is regularly bitten by naive vectors, implicating a permanent stimulation of the immune system by the vector saliva itself (pre-immune context). Comparatively, the number of bites received by exposed individuals from non-infected vectors is much higher than the bites from infected ones. Therefore, vector saliva and the immunological response in the skin may play an important role, so far underestimated, in the establishment of anti-pathogen immunity in endemic areas. Hence, the parasite biology and the disease pathogenesis in "saliva-primed" and "saliva-unprimed" individuals must be different. This integrated view on how the pathogen evolves within the host together with vector salivary components, which are known to be endowed with a variety of pharmacological and immunological properties, must remain the focus of any investigational study dealing with vector-borne diseases. Considering this three-way partnership, the host skin (immune system), the pathogen, and the vector saliva, the approach that consists in the validation of vector saliva as a source of molecular entities with anti-disease vaccine potential has been recently a subject of active and fruitful investigation. As an example, the vaccination with maxadilan, a potent vasodilator peptide extracted from the saliva of the sand fly Lutzomyia longipalpis, was able to protect against infection with various leishmanial parasites. More interestingly, a universal mosquito saliva vaccine that may potentially protect against a range of mosquito-borne infections including malaria, dengue, Zika, chikungunya and yellow fever. In this review, we highlight the key role played by the immunobiology of vector saliva in shaping the outcome of vector-borne diseases and discuss the value of studying diseases in the light of intimate cross talk among the pathogen, the vector saliva, and the host immune mechanisms.(AU)
Assuntos
Parasitos , Calcanhar , Vacinação , Inflamação/imunologia , ImunidadeRESUMO
Epigenetic control via reversible histone methylation regulates transcriptional activation throughout the malaria parasite genome, controls the repression of multi-copy virulence gene families and determines sexual stage commitment. Plasmodium falciparum encodes ten predicted SET domain-containing protein methyltransferases, six of which have been shown to be refractory to knock-out in blood stage parasites. We have expressed and purified the first recombinant malaria methyltransferase in sufficient quantities to perform a full enzymatic characterization and reveal the ill-defined PfSET7 is an AdoMet-dependent histone H3 lysine methyltransferase with highest activity towards lysines 4 and 9. Steady-state kinetics of the PfSET7 enzyme are similar to previously characterized histone methyltransferase enzymes from other organisms, however, PfSET7 displays specific protein substrate preference towards nucleosomes with pre-existing histone H3 lysine 14 acetylation. Interestingly, PfSET7 localizes to distinct cytoplasmic foci adjacent to the nucleus in erythrocytic and liver stage parasites, and throughout the cytoplasm in salivary gland sporozoites. Characterized recombinant PfSET7 now allows for target based inhibitor discovery. Specific PfSET7 inhibitors can aid in further investigating the biological role of this specific methyltransferase in transmission, hepatic and blood stage parasites, and may ultimately lead to the development of suitable antimalarial drug candidates against this novel class of essential parasite enzymes.
Assuntos
Histona-Lisina N-Metiltransferase/metabolismo , Histonas/metabolismo , Plasmodium falciparum/enzimologia , Proteínas de Protozoários/metabolismo , Esporozoítos/enzimologia , Trofozoítos/enzimologia , Sequência de Aminoácidos , Animais , Anopheles/parasitologia , Baculoviridae/genética , Baculoviridae/metabolismo , Clonagem Molecular , Epigênese Genética , Eritrócitos/parasitologia , Eritrócitos/ultraestrutura , Expressão Gênica , Histona-Lisina N-Metiltransferase/genética , Histonas/genética , Humanos , Cinética , Fígado/citologia , Fígado/parasitologia , Mutação , Plasmodium falciparum/genética , Plasmodium falciparum/ultraestrutura , Proteínas de Protozoários/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Glândulas Salivares/parasitologia , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Células Sf9 , Spodoptera , Esporozoítos/ultraestrutura , Especificidade por Substrato , Trofozoítos/ultraestruturaRESUMO
Transmission of information from mast cells to neighboring or distant cells must be established continuously in order to ensure homeostasis or to initiate immune and inflammatory responses. Owing to their strategic location in peripheral tissues and their prompt response to various stimuli, mast cells can be considered as the cell prototype to fulfill such a sentinel function. There are several ways for mast cells to communicate with other cells including cell-cell interactions via membrane-associated receptors, cytokines and other soluble mediators, and a newly described messenger which consists of membrane vesicles called exosomes carrying a number of immunoregulatory molecules.
Assuntos
Mastócitos/imunologia , Vesículas Secretórias/fisiologia , Animais , Comunicação Celular , Exocitose , Lisossomos/química , Mastócitos/química , Vesículas Secretórias/químicaRESUMO
OBJECTIVE: Anaphylaxis is a life-threatening outcome of immediate-type hypersensitivity to allergen, consecutive to mast cell degranulation by allergen-specific IgE. Regulatory T cells (Treg) can control allergic sensitization and mast cell degranulation, yet their clinical benefit on anaphylactic symptoms is poorly documented. Here we investigated whether Treg action during the effector arm of the allergic response alleviates anaphylaxis. METHODS: We used a validated model of IgE-mediated passive systemic anaphylaxis, induced by intravenous challenge with DNP-HSA in mice passively sensitized with DNP-specific IgE. Anaphylaxis was monitored by the drop in body temperature as well as plasma histamine and serum mMCP1 levels. The role of Treg was analyzed using MHC class II-deficient (Aß(°/°)) mice, treatment with anti-CD25 or anti-CD4 mAbs and conditional ablation of Foxp3(+) Treg in DEREG mice. Therapeutic efficacy of Treg was also evaluated by transfer experiments using FoxP3-eGFP knock-in mice. RESULTS: Anaphylaxis did not occur in mast cell-deficient W/W(v) mutant mice and was only moderate and transient in mice deficient for histamine receptor-1. Defects in constitutive Treg, either genetic or induced by antibody or toxin treatment resulted in a more severe and/or sustained hypothermia, associated with a rise in serum mMCP1, but not histamine. Adoptive transfer of Foxp3(+) Treg from either naïve or DNP-sensitized donors similarly alleviated body temperature loss in Treg-deficient DEREG mice. CONCLUSION: Constitutive Foxp3(+) Treg can control the symptomatic phase of mast cell and IgE-dependent anaphylaxis in mice. This might open up new therapeutic avenues using constitutive rather than Ag-specific Treg for inducing tolerance in allergic patients.