Cellules natural killer et immunité innée contre le paludisme

La réponse immunitaire dirigée contre Plasmodium falciparum (Pf), agent responsable du paludisme chez l’homme, est le résultat de plusieurs milliers d’années de co-évolution entre le parasite et son hôte. La production rapide d’IFNγ (interféron γ) est importante pour le pronostic évolutif de la pathologie. Des études récentes suggèrent que les cellules natural killer (NK) pourraient être l’une des sources de cette production précoce d’IFNγ. Plus connues pour leur rôle dans l’immunité antitumorale et antivirale, les cellules NK seraient également capables de reconnaître directement des hématies infectées par Pf. À la suite de ce contact, leur sécrétion de la chimiokine IL-8 (interleukine 8) pourrait permettre le recrutement d’autres types cellulaires dans des lieux stratégiques. L’activation des cellules NK doit être replacée dans le contexte d’une réponse immunitaire complexe impliquant d’autres acteurs. Une collaboration entre cellules NK et macrophages serait notamment requise pour une réponse NK optimale. Les fondements moléculaires de l’activation des cellules NK, ainsi que leur rôle dans le contrôle initial du stade sanguin de l’infection font aujourd’hui l’objet d’intenses recherches.Innate immune response against Plasmodium falciparum (Pf), a causative agent of human malaria, is the result of several thousand years of co-evolution between the parasite and his host. An early IFN-γ production during infection is associated with a better evolution of the disease. Natural killer (NK) cells are among the first cells in peripheral blood to produce IFN-γ in response to Pf-infected erythrocytes (Pf-E). NK cells are found in blood, in secondary lymphoid organs as well as in peripheral non-lymphoid tissues. They participate in host innate responses that occur upon viral and intracytoplasmic bacterial infections, but also during the course of tumor development and allogeneic transplantation. These lymphocytes are not only important players of innate effector responses, but also participate in the initiation and development of adaptive immune responses. In addition, direct sensing of Pf infection by NK cells induces their production of the proinflammatory chemokine IL-8, suggesting a role for NK cells in the recruitment and the activation of other cells during malaria infection. Several other cell subsets are involved in the innate immune response to Pf. Dendritic cells, macrophages, γδT cells, NKT cells are able to sense the presence of the parasite. Along this line, the presence of IL-12 is necessary to NK cell IFN-γ production and a functional cooperation takes place between macrophages and NK cells in the context of this parasitic infection. In particular, IL-18 produced by macrophages is a key factor for this NK response. However, the molecular basis of Pf-E recognition by NK cells as well as the functional role of NK cell responses during the course of the disease remain to be adressed

Synthesis and biological evaluation of novel substituted pyrrolo[1,2-a]quinoxaline derivatives as inhibitors of the human protein kinase CK2

Herein we describe the synthesis and properties of substituted phenylaminopyrrolo[1,2-a]quinoxaline-carboxylic acid derivatives as a novel class of potent inhibitors of the human protein kinase CK2. A set of 15 compounds was designed and synthesized using convenient and straightforward synthesis protocols. The compounds were tested for inhibition of human protein kinase CK2, which is a potential drug target for many diseases including inflammatory disorders and cancer. New inhibitors with IC50 in the micro- and sub-micromolar range were identified. The most promising compound, the 4-[(3-chlorophenyl)amino]pyrrolo[1,2-a]quinoxaline-3-carboxylic acid 1c inhibited human CK2 with an IC50 of 49 nM. Our findings indicate that pyrrolo[1,2-a]quinoxalines are a promising starting scaffold for further development and optimization of human protein kinase CK2 inhibitorsFil: Guillon, Jean. Universite de Bordeaux; Francia;Fil: Le Borgne, Marc. Université de Lyon; Francia;Fil: Rimbault, Charlotte. Universite de Bordeaux; Francia;Fil: Moreau, Stéphane. Universite de Bordeaux; Francia;Fil: Savrimoutou, Solène. Universite de Bordeaux; Francia;Fil: Pinaud, Noël. Universite de Bordeaux; Francia;Fil: Baratin, Sophie. Universite de Bordeaux; Francia;Fil: Marchivie, Mathieu. Universite de Bordeaux; Francia;Fil: Roche, Séverine. Universite de Bordeaux; Francia;Fil: Bollacke, Andre. Institut für Pharmazeutische und Medizinische Chemie. Westfälische Wilhelms-Universität Münster; Alemania;Fil: Pecci, Adali. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Fisiol., Biol.molecular y Neurociencias; Argentina;Fil: Alvarez, Lautaro Damian. Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unid.microanal.y Met.fisicos En Quim.org.(i); Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Quimica Organica;Fil: Desplat, Vanessa. Universite de Bordeaux; Francia;Fil: Joachim, Jose. Institut für Pharmazeutische und Medizinische Chemie. Westfälische Wilhelms-Universität Münster; Alemania

Dissection of the Role of PfEMP1 and ICAM-1 in the Sensing of Plasmodium falciparum-Infected Erythrocytes by Natural Killer Cells

BACKGROUND: Host innate immunity contributes to malaria clinical outcome by providing protective inflammatory cytokines such as interferon-γ, and by shaping the adaptive immune response. Plasmodium falciparum (Pf) is the etiologic agent of the most severe forms of human malaria. Natural Killer (NK) cells are lymphocytes of the innate immune system that are the first effectors to produce interferon-γ in response to Pf. However, the molecular bases of Pf-NK cell recognition events are unknown. Our study focuses on the role of Pf erythrocyte membrane protein 1 (PfEMP1), a major Pf virulence factor. PfEMP1 is expressed on parasitized-erythrocytes and participates to vascular obstruction through the binding to several host receptors. PfEMP1 is also a pivotal target for host antibody response to Pf infection. METHODOLOGY/PRINCIPAL FINDINGS: Using genetically-engineered parasite mutant strains, a human genetic deficiency, and blocking antibodies, we identified two receptor-ligand pairs involved in two uncoupled events occurring during the sensing of Pf infection by NK cells. First, PfEMP1 interaction with one of its host receptor, chondroitin sulfate A, mediates the cytoadhesion of Pf-infected erythrocytes to human NK cell lines, but is not required for primary NK cell activation. Second, intercellular adhesion molecule-1 (ICAM-1), another host receptor for PfEMP1, is mandatory for NK cell interferon-γ response. In this case, ICAM-1 acts via its engagement with its host ligand, LFA-1, and not with PfEMP1, consistent with the obligatory cross-talk of NK cells with macrophages for their production of interferon-γ. CONCLUSION/SIGNIFICANCE: PfEMP1-independent but ICAM-1/LFA-1-dependent events occurring during NK cell activation by Pf highlight the fundamental role of cellular cooperation during innate immune response to malaria

The SIB Swiss Institute of Bioinformatics' resources: focus on curated databases

The SIB Swiss Institute of Bioinformatics (www.isb-sib.ch) provides world-class bioinformatics databases, software tools, services and training to the international life science community in academia and industry. These solutions allow life scientists to turn the exponentially growing amount of data into knowledge. Here, we provide an overview of SIB's resources and competence areas, with a strong focus on curated databases and SIB's most popular and widely used resources. In particular, SIB's Bioinformatics resource portal ExPASy features over 150 resources, including UniProtKB/Swiss-Prot, ENZYME, PROSITE, neXtProt, STRING, UniCarbKB, SugarBindDB, SwissRegulon, EPD, arrayMap, Bgee, SWISS-MODEL Repository, OMA, OrthoDB and other databases, which are briefly described in this article

Natural killer cells and malaria.

Malaria, caused by the infection with parasites of the germs Plasmodium, is one of the three most important infectious diseases worldwide, along with tuberculosis and infection with human immunodeficiency virus. Natural killer (NK) cells are lymphocytes classically involved in the early defense against viral infections and intracytoplasmic bacterial infections and are also implicated during the course of tumor development and allogeneic transplantation. These cells display important cytotoxic activity and produce high levels of proinflammatory cytokines. In both mouse and human models of malaria, NK cells appear to be a major source of interferon-gamma during the early phase of infection. In humans, indirect signaling through monocytes/macrophages required to optimally stimulate NK cell activity. However, the in vivo functions of NK cells during malaria are still enigmatic, and many issues remain to be dissected, such as the molecular basis of the direct recognition of iRBCs by NK cells

Complement factor P is a ligand for the natural killer cell-activating receptor NKp46

International audienceInnate lymphoid cells (ILCs) are involved in immune responses to microbes and various stressed cells, such as tumor cells. They include group 1 [such as natural killer (NK) cells and ILC1], group 2, and group 3 ILCs. Besides their capacity to respond to cytokines, ILCs detect their targets through a series of cell surface-activating receptors recognizing microbial and nonmicrobial ligands. The nature of some of these ligands remains unclear, limiting our understanding of ILC biology. We focused on NKp46, which is highly conserved in mammals and expressed by all mature NK cells and subsets of ILC1 and ILC3. We show here that NKp46 binds to a soluble plasma glycoprotein, the complement factor P (CFP; properdin), the only known positive regulator of the alternative complement pathway. Consistent with the selective predisposition of patients lacking CFP to lethal Neisseria meningitidis (Nm) infections, NKp46 and group 1 ILCs bearing this receptor were found to be required for mice to survive Nm infection. Moreover, the beneficial effects of CFP treatment for Nm infection were dependent on NKp46 and group 1 NKp46(+)ILCs. Thus, group 1 NKp46(+)ILCs interact with the complement pathway, via NKp46, revealing a cross-talk between two partners of innate immunity in the response to an invasive bacterial infection

CSA is involved in IE interaction with human NK cell line but not in primary NK cell activation.

<p>(A) The human NK cell line NK92 was incubated with whole culture of IE in different conditions. After 1 h at 37°C, a sample of the co-culture was placed between slide and cover and analyzed under a microscope. The NK92 cells directly interacts with IE (FCR3-CSA strain) as rosettes, but not with uninfected erythrocytes (x100 original magnification, left panel). RBC infected with FCR3-CSA or 2A5 were co-cultured with NK92 cells alone or in the presence of soluble CSA (+CSA), or with NK92 cells pre-treated with chondroitinase ABC (+Case ABC). At the end of the co-culture, the percentage of NK cells interacting with at least two IE was determined and expressed as % of cytoadhesion. Each dot represents one independent experiment (right panel). (B) Freshly isolated human PBMC were cultured with uninfected RBC (RBC), RBC infected with FCR3-CSA or RBC infected with the <i>var2csa</i> KO parasite 2A5. After 24 h, NK cell activation was analyzed by flow cytometry by gating on CD3⁻CD56⁺ lymphocytes. The CD69 MFI (mean fluorescence intensity) staining on NK cells (left panel), the percentage of CD25⁺ NK cells (middle panel) and the percentage of IFN-γ⁺ NK cells (right panel) were determined for 7 different healthy donors. Means±SEM are represented. Statistical analyses were performed using the Wilcoxon test.</p

Deficiency in CD36 does not alter NK cell response to IE.

<p>(A) The level of CD36 expression was determined on PBMC collected from a healthy donor (Control donor) or from a patient deficient for CD36. Total PBMC protein extracts were prepared and analyzed by Western Blot (left panel). Total PBMC were stained with CD36 antibody or with an isotype control (filled grey histogram, right panel). Histograms for CD3⁻CD56⁺ NK cells from a CD36 deficient donor (dotted line) and a control donor (bold line) are represented. (B) Control or CD36-deficient PBMC were cultured with uninfected RBC (RBC, black bars), or with RBC infected with the 3D7 <i>Pf</i> strain (3D7, grey bars). After 24 h, NK cell activation was analyzed by flow cytometry by gating on CD3⁻CD56⁺ NK cells. The CD69 MFI staining on NK cells (left panel), the percentage of CD25⁺ NK cells (middle panel) and the percentage of IFN-γ⁺ NK cells (right panel) were determined in three independent experiments. Means ± SEM are represented. Statistical analyses were performed using the Mann Whitney test.</p

Engagement of ICAM-1 with its cellular ligand but not with PfEMP1 is required for NK cell IFN-γ production.

<p>(A) Diagram of an ICAM-1 molecule showing schematic binding sites for LFA-1, Mac-1, CD11c/CD18 and PfEMP1. The epitope map of the anti-ICAM-1 mAb 15.2, My13 and RR1/1 is indicated. (B) Human PBMC were cultured with uninfected RBC (RBC, black bars) or with RBC infected with the 3D7 <i>Pf</i> strain (3D7, grey bars) in presence or absence of antibodies directed against NKG2D (isotype control), ICAM-1 or CD18. Three different clones of anti-ICAM-1 were used: 15.2 blocks the interaction of ICAM-1 with LFA-1 and with PfEMP1, RR1/1 blocks only the interaction with LFA-1 and My13 blocks only the interaction with PfEMP1. After 24 h of co-culture, NK cell activation was analyzed by flow cytometry by gating on CD3⁻CD56⁺ NK cells. The CD69 MFI staining on NK cells (left panel), the percentage of CD25⁺ NK cells (middle panel) and the percentage of IFN-γ⁺ NK cells (right panel) were determined for 24 donors (None, NKG2D and 15.2), 13 donors (CD18), 9 donors (My13) or 5 donors (RR1/1). Means ± SEM are represented. Statistical analyses were performed using the Mann Whitney test.</p