title: The Ebola Interferon Inhibiting Domains Attenuate and Dysregulate Cell-Mediated Immune Responses.
abstract: Ebola virus (EBOV) infections are characterized by deficient T-lymphocyte responses, T-lymphocyte apoptosis and lymphopenia. We previously showed that disabling of interferon-inhibiting domains (IIDs) in the VP24 and VP35 proteins effectively unblocks maturation of dendritic cells (DCs) and increases the secretion of cytokines and chemokines. Here, we investigated the role of IIDs in adaptive and innate cell-mediated responses using recombinant viruses carrying point mutations, which disabled IIDs in VP24 (EBOV/VP24m), VP35 (EBOV/VP35m) or both (EBOV/VP35m/VP24m). Peripheral blood mononuclear cells (PBMCs) from cytomegalovirus (CMV)-seropositive donors were inoculated with the panel of viruses and stimulated with CMV pp65 peptides. Disabling of the VP35 IID resulted in increased proliferation and higher percentages of CD4+ T cells secreting IFNγ and/or TNFα. To address the role of aberrant DC maturation in the IID-mediated suppression of T cell responses, CMV-stimulated DCs were infected with the panel of viruses and co-cultured with autologous T-lymphocytes. Infection with EBOV/VP35m infection resulted in a significant increase, as compared to wt EBOV, in proliferating CD4+ cells secreting IFNγ, TNFα and IL-2. Experiments with expanded CMV-specific T cells demonstrated their increased activation following co-cultivation with CMV-pulsed DCs pre-infected with EBOV/VP24m, EBOV/VP35m and EBOV/VP35m/VP24m, as compared to wt EBOV. Both IIDs were found to block phosphorylation of TCR complex-associated adaptors and downstream signaling molecules. Next, we examined the effects of IIDs on the function of B cells in infected PBMC. Infection with EBOV/VP35m and EBOV/VP35m/VP24m resulted in significant increases in the percentages of phenotypically distinct B-cell subsets and plasma cells, as compared to wt EBOV, suggesting inhibition of B cell function and differentiation by VP35 IID. Finally, infection with EBOV/VP35m increased activation of NK cells, as compared to wt EBOV. These results demonstrate a global suppression of cell-mediated responses by EBOV IIDs and identify the role of DCs in suppression of T-cell responses.
authors.affiliation: Department of Pathology, the University of Texas Medical Branch, Galveston, Texas, United States of America.|Galveston National Laboratory, the University of Texas Medical Branch, Galveston, Texas, United States of America.
authors.forename: Ndongala Michel
authors.initials: NM
authors.lastname: Lubaki
authors.affiliation: Department of Pathology, the University of Texas Medical Branch, Galveston, Texas, United States of America.|Galveston National Laboratory, the University of Texas Medical Branch, Galveston, Texas, United States of America.
authors.forename: Patrick
authors.initials: P
authors.lastname: Younan
authors.affiliation: Department of Pathology, the University of Texas Medical Branch, Galveston, Texas, United States of America.|Galveston National Laboratory, the University of Texas Medical Branch, Galveston, Texas, United States of America.
authors.forename: Rodrigo I
authors.identifier: http://orcid.org/0000-0003-2548-1288
authors.initials: RI
authors.lastname: Santos
authors.affiliation: Department of Pathology, the University of Texas Medical Branch, Galveston, Texas, United States of America.|Galveston National Laboratory, the University of Texas Medical Branch, Galveston, Texas, United States of America.
authors.forename: Michelle
authors.initials: M
authors.lastname: Meyer
authors.affiliation: Department of Pathology, the University of Texas Medical Branch, Galveston, Texas, United States of America.|Galveston National Laboratory, the University of Texas Medical Branch, Galveston, Texas, United States of America.
authors.forename: Mathieu
authors.identifier: http://orcid.org/0000-0001-7667-3584
authors.initials: M
authors.lastname: Iampietro
authors.affiliation: Immunology Laboratory, Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Koup
authors.affiliation: Department of Pathology, the University of Texas Medical Branch, Galveston, Texas, United States of America.|Galveston National Laboratory, the University of Texas Medical Branch, Galveston, Texas, United States of America.|Department of Microbiology & Immunology, the University of Texas Medical Branch, Galveston, Texas, United States of America.
authors.forename: Alexander
authors.initials: A
authors.lastname: Bukreyev
mesh_terms: D001402:B-Lymphocytes / Q000276:immunology; D015153:Blotting, Western; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D002469:Cell Separation; D003713:Dendritic Cells / Q000276:immunology; D029043:Ebolavirus / Q000276:immunology; D005434:Flow Cytometry; D019142:Hemorrhagic Fever, Ebola / Q000276:immunology*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000821:virology; D008213:Lymphocyte Activation / Q000276:immunology*; D018613:Microscopy, Confocal; D000072417:Protein Domains / Q000276:immunology; D014764:Viral Proteins / Q000276:immunology*; D054334:Viral Regulatory and Accessory Proteins / Q000276:immunology*
chemical_list: C446938:VP24 protein, Ebola virus; C080980:VP35 protein, filovirus; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins