Immunointervention of immune pathologies and cancer : studies on the use of therapeutic immunoglobulins and viscum album preparations

COMPIEGNE-BU (601592101) / SudocSudocFranceF

PE_PGRS Antigens of Mycobacterium tuberculosis Induce Maturation and Activation of Human Dendritic Cells

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Modulation of human dendritic cell maturation and function by natural IgG antibodies

International audienceDendritic cells (DCs) are professional antigen-presenting cells, which have a central role in the initiation of primary immune responses and in maintaining immune tolerance. The functions of DCs can be regulated both by environmental signals as well as signals delivered by endogenous molecules. Recently we have examined regulation of human DCs by B cells via natural IgG antibodies. Natural antibodies (NAbs) are defined as antibodies that circulate in normal individuals in the absence of deliberate immunization or microbial aggression. We demonstrate that the differentiation of DCs is severely impaired in primary immunodeficient patients such as X-linked agammaglobulinemia (XLA) and common variable immunodeficiency (CVID) at least in part due to the deficiency of circulating NAbs. Further, we show that NAbs are able to restore normal phenotypes of DCs from patients with XLA and CVID. Our results suggest that B cells promote bystander DC development through NAbs and the interaction between NAbs and DCs may play a role in steady-state migration of DCs

Surface hydrophobin prevents immune recognition of airborne fungal spores

International audienceThe air we breathe is filled with thousands of fungal spores (conidia) per cubic metre, which in certain composting environments can easily exceed 10(9) per cubic metre. They originate from more than a hundred fungal species belonging mainly to the genera Cladosporium, Penicillium, Alternaria and Aspergillus. Although these conidia contain many antigens and allergens, it is not known why airborne fungal microflora do not activate the host innate immune cells continuously and do not induce detrimental inflammatory responses following their inhalation. Here we show that the surface layer on the dormant conidia masks their recognition by the immune system and hence prevents immune response. To explore this, we used several fungal members of the airborne microflora, including the human opportunistic fungal pathogen Aspergillus fumigatus, in in vitro assays with dendritic cells and alveolar macrophages and in in vivo murine experiments. In A. fumigatus, this surface 'rodlet layer' is composed of hydrophobic RodA protein covalently bound to the conidial cell wall through glycosylphosphatidylinositol-remnants. RodA extracted from conidia of A. fumigatus was immunologically inert and did not induce dendritic cell or alveolar macrophage maturation and activation, and failed to activate helper T-cell immune responses in vivo. The removal of this surface 'rodlet/hydrophobin layer' either chemically (using hydrofluoric acid), genetically (DeltarodA mutant) or biologically (germination) resulted in conidial morphotypes inducing immune activation. All these observations show that the hydrophobic rodlet layer on the conidial cell surface immunologically silences airborne moulds

The protective role of immunoglobulins in fungal infections and inflammation

International audienceIncreased incidence of fungal infections in the immunocompromised individuals and fungi-mediated allergy and inflammatory conditions in immunocompetent individuals is a cause of concern. Consequently, there is a need for efficient therapeutic alternatives to treat fungal infections and inflammation. Several studies have demonstrated that antibodies or immunoglobulins have a role in restricting the fungal burden and their clearance. However, based on the data from monoclonal antibodies, it is now evident that the efficacy of antibodies in fungal infections is dependent on epitope specificity, abundance of protective antibodies, and their isotype. Antibodies confer protection against fungal infections by multiple mechanisms that include direct neutralization of fungi and their antigens, inhibition of growth of fungi, modification of gene expression, signaling and lipid metabolism, causing iron starvation, inhibition of polysaccharide release, and biofilm formation. Antibodies promote opsonization of fungi and their phagocytosis, complement activation, and antibody-dependent cell toxicity. Passive administration of specific protective monoclonal antibodies could also prove to be beneficial in drug resistance cases, to reduce the dosage and associated toxic symptoms of anti-fungal drugs. The longer half-life of the antibodies and flexibilities to modify their structure/forms are additional advantages. The clinical data obtained with two monoclonal antibodies should incite interests in translating pre-clinical success into the clinics. The anti-inflammatory and immunoregulatory role of antibodies in fungal inflammation could be exploited by intravenous immunoglobulin or IVIg