title: The human metapneumovirus matrix protein stimulates the inflammatory immune response in vitro.
abstract: Each year, during winter months, human Metapneumovirus (hMPV) is associated with epidemics of bronchiolitis resulting in the hospitalization of many infants. Bronchiolitis is an acute illness of the lower respiratory tract with a consequent inflammation of the bronchioles. The rapid onset of inflammation suggests the innate immune response may have a role to play in the pathogenesis of this hMPV infection. Since, the matrix protein is one of the most abundant proteins in the Paramyxoviridae family virion, we hypothesized that the inflammatory modulation observed in hMPV infected patients may be partly associated with the matrix protein (M-hMPV) response. By western blot analysis, we detected a soluble form of M-hMPV released from hMPV infected cell as well as from M-hMPV transfected HEK 293T cells suggesting that M-hMPV may be directly in contact with antigen presenting cells (APCs) during the course of infection. Moreover, flow cytometry and confocal microscopy allowed determining that M-hMPV was taken up by dendritic cells (moDCs) and macrophages inducing their activation. Furthermore, these moDCs enter into a maturation process inducing the secretion of a broad range of inflammatory cytokines when exposed to M-hMPV. Additionally, M-hMPV activated DCs were shown to stimulate IL-2 and IFN-γ production by allogeneic T lymphocytes. This M-hMPV-mediated activation and antigen presentation of APCs may in part explain the marked inflammatory immune response observed in pathology induced by hMPV in patients.
authors.affiliation: bioMérieux, Emerging Pathogens Department, Institut Fédératif de Recherche 128 BioSciences Lyon Gerland, Lyon, France.
authors.forename: Audrey
authors.initials: A
authors.lastname: Bagnaud-Baule
authors.forename: Olivier
authors.initials: O
authors.lastname: Reynard
authors.forename: Magali
authors.initials: M
authors.lastname: Perret
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Berland
authors.forename: Mimoun
authors.initials: M
authors.lastname: Maache
authors.forename: Christophe
authors.initials: C
authors.lastname: Peyrefitte
authors.forename: Guy
authors.initials: G
authors.lastname: Vernet
authors.forename: Viktor
authors.initials: V
authors.lastname: Volchkov
authors.forename: Gláucia
authors.initials: G
authors.lastname: Paranhos-Baccalà
mesh_terms: D017951:Antigen Presentation / Q000276:immunology; D000938:Antigen-Presenting Cells / Q000378:metabolism; D018949:Antigens, CD1 / Q000378:metabolism; D017209:Apoptosis; D002454:Cell Differentiation / Q000276:immunology; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology / Q000821:virology; D004705:Endocytosis; D057809:HEK293 Cells; D006801:Humans; D007109:Immunity / Q000276:immunology*; D007249:Inflammation / Q000276:immunology*; D018836:Inflammation Mediators / Q000378:metabolism; D007372:Interferons / Q000096:biosynthesis; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D029121:Metapneumovirus / Q000276:immunology*; D009000:Monocytes / Q000166:cytology; D011485:Protein Binding; D013347:Subcellular Fractions / Q000276:immunology / Q000821:virology; D013601:T-Lymphocytes / Q000276:immunology; D014162:Transfection; D014763:Viral Matrix Proteins / Q000276:immunology*
chemical_list: D018949:Antigens, CD1; C419393:CD1a antigen; D018836:Inflammation Mediators; D018950:Lipopolysaccharide Receptors; D014763:Viral Matrix Proteins; D007372:Interferons